Abstract:
An auxiliary power supply circuit of a two wire dimmer, comprising: an auxiliary source capacitor ( 20 ) and a cutoff switch ( 30 ) constituting a series branch, a chopper switch ( 10 ) parallel-connected to the series branch, and a control device ( 40 ) connected to the chopper switch ( 10 ) and to the cutoff switch ( 30 ). The control device ( 40 ) measures an auxiliary source voltage and receives a chopper voltage control signal (Vg), and outputs signals (V 1  and V 2 ), on the basis of the result of a comparison between the auxiliary source voltage and a preset voltage and of the state of the chopper voltage control signal (Vg), to control the on and off of the chopper switch ( 10 ) and of the cutoff switch ( 30 ) for controlling the charging of the auxiliary source capacitor ( 20 ). The auxiliary power supply circuit has low losses, high efficiency, and is not limited by minimum chopper angle, and has low electromagnetic interference.

Description:
[0001]    This application claims the priority to Chinese patent application No. 201110083933.8, titled “AUXILIARY POWER SUPPLY CIRCUIT OF TWO WIRE DIMMER”, filed with the State Intellectual Property Office on Apr. 2, 2011, which is incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to the technical field of auxiliary power supply, and in particular to an auxiliary power supply circuit of a two-wire dimmer. 
       BACKGROUND OF THE INVENTION 
       [0003]    A dimmer is an electrical apparatus used to change luminous flux and adjust illumination level for a light source in an illumination apparatus. The dimmer is usually connected between a hot and a dimmed hot to adjust light by changing the effective value of the input current of a light source. 
         [0004]    The commonly-used dimmer has only two wires to connect with the hot and the dimmed hot, therefore, the dimmer is referred to as a two-wire dimmer. In the two-wire dimmer, a semiconductor power device such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor) or a thyristor may be adopted as a chopper switch. The power network voltage may be controlled by controlling the chopper switch to be on or off. The magnitude of the chopper angle by the chopper switch indicates the level of the light-adjusting signal. 
         [0005]    In order to meet requirements of a color lighting system, the two-wire dimmer is required to adjust light in multiple ways such as adjust the color and/or brightness. Generally, there are many circuits in the two-wire dimmer, and even a digital controlling such as a microcontroller is needed. Therefore, an auxiliary power supply for powering the microcontroller or other circuits is needed in the two-wire dimmer. 
         [0006]      FIG. 1  is a diagram of an auxiliary power supply circuit of a two-wire dimmer in the prior art. In a case that both chopper switches  110  and  112  are turned off, the auxiliary power supply  124  in the circuit charges the capacitor C 1  by using voltage drop generated when the chopper switches are turned off. In the positive half period of the sinusoidal wave, a charging loop is formed by the diode D 1 , the capacitor C 1 , the body diode of the chopper switch  112  and the load; in the negative half period of the sinusoidal wave, a charging loop is formed by the diode D 2 , the capacitor C 1 , the body diode of the chopper switch  112  and the load. Then an auxiliary voltage Vcc is obtained by voltage regulation of the auxiliary power supply  124 . 
         [0007]    Since the auxiliary voltage Vcc is obtained by using the voltage generated due to the turn-off of the chopper switches, the minimum chopper angle is needed in order to obtain the minimum auxiliary voltage (the chopper switch is turned off). However, even the chopper switch is off in a very short time (very small angle), a significant electromagnetic interference will be brought into the circuit due to abrupt change of the voltage and the current. In addition, the capacitor C 1  may suffer from a peak voltage of the power network voltage, which is converted into a low voltage signal Vcc after passing through the auxiliary power supply  124 , to power other circuits, resulting in a high cost and a low efficiency. 
       SUMMARY OF THE INVENTION 
       [0008]    In view of the above, an object of the present invention is to provide an auxiliary power supply circuit of a two-wire dimmer, by which the defects in the prior art can be solved with a simple circuit and a low cost. 
         [0009]    In order to achieve the above object, the following solution is provided according to the present invention: an auxiliary power supply circuit of a two-wire dimmer, including an auxiliary source capacitor and a disconnecting switch connected in series to form a series branch, a chopper switch connected in parallel with the series branch, and a control device connected to the chopper switch and the disconnecting switch; 
         [0010]    the control device is configured to detect an auxiliary source voltage and receive a chopper voltage control signal, output a signal to control the chopper switch and the disconnecting switch to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage and a state of the chopper voltage control signal, to control charging of the auxiliary source capacitor. 
         [0011]    Another auxiliary power supply circuit of a two-wire dimmer is further provided according to the present invention, including an auxiliary source capacitor and a disconnecting switch connected in series to form a series branch, a chopper switch connected in parallel with the series branch, and a control device connected to the chopper switch and the disconnecting switch; 
         [0012]    the control device is configured to detect an auxiliary source voltage and receive a chopper period control signal and a chopper voltage control signal, judge whether the chopper switch is in a chopper period according to the chopper period control signal, output a signal to control the chopper switch and the disconnecting switch to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage, a state of the chopper voltage control signal and whether the chopper switch being in a chopper period, to control charging of the auxiliary source capacitor. 
         [0013]    Another auxiliary power supply circuit of a two-wire dimmer is further provided according to the present invention, including a rectifier device and an auxiliary source capacitor connected in series to form a series branch, a disconnecting switch connected in parallel with the series branch to form a parallel branch, a chopper switch connected in series with the parallel branch, and a control device connected to the chopper switch and the disconnecting switch; 
         [0014]    the control device is configured to detect an auxiliary source voltage and receive a chopper voltage control signal, and output a signal to control the disconnecting switch and the chopper switch to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage and a state of the chopper voltage control signal, to charge the auxiliary source capacitor by the rectifier device. 
         [0015]    Another auxiliary power supply circuit of a two-wire dimmer is further provided according to the present invention, including a rectifier device and an auxiliary source capacitor connected in series to form a series branch, a disconnecting switch connected in parallel with the series branch to form a parallel branch, a chopper switch connected in series with the parallel branch, and a control device connected to the chopper switch and the disconnecting switch; 
         [0016]    the control device is configured to detect an auxiliary source voltage and receive a chopper voltage control signal and a chopper period control signal, judge whether the chopper switch is in a chopper period according to the chopper period control signal, and output a signal to control the disconnecting switch and the chopper switch to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage, a state of the chopper voltage control signal and whether the chopper switch being in a chopper period, to control charging of the auxiliary source capacitor by the rectifier device. 
         [0017]    Another auxiliary power supply circuit of a two-wire dimmer is further provided according to the present invention, including a first power supply branch and a second power supply branch, 
         [0018]    the first power supply branch includes a first auxiliary source capacitor and a first disconnecting switch connected in series to form a first series branch, and a first chopper switch connected in parallel with the first series branch; 
         [0019]    the second power supply branch includes a rectifier device and a second auxiliary source capacitor connected in series to form a second series branch, a second disconnecting switch connected in parallel with the second series branch to form a parallel branch, and a second chopper switch connected in series with the parallel branch; 
         [0020]    the auxiliary power supply circuit further includes a first control device for controlling the first power supply branch and a second control device for controlling the second power supply branch, 
         [0021]    the first control device is configured to detect an auxiliary source voltage of the first power supply branch and receive a first chopper voltage control signal or a first chopper period control signal, and output a signal to control the first chopper switch and the first disconnecting switch to be on or off according to a comparison result of the auxiliary source voltage of the first power supply branch with a preset voltage and a state of the first chopper voltage control signal or a state of the first chopper period control signal, to control charging of the first auxiliary source capacitor; and 
         [0022]    the second control device is configured to detect an auxiliary source voltage of the second power supply branch and receive a second chopper voltage control signal or a second chopper period control signal, and output a signal to control the second disconnecting switch and the second chopper switch to be on or off according to a comparison result of the auxiliary source voltage of the second power supply branch with a preset voltage and a state of the second chopper voltage control signal or a state of the second chopper period control signal, to charge the second auxiliary source capacitor by the rectifier device. 
         [0023]    The following technical effects are provided by embodiments of the present invention. 
         [0024]    In the circuits described in the embodiments of the invention, in a case that the auxiliary source voltage is lower than a preset value, at least one chopper switch is turned off, and the auxiliary source capacitor replaces the chopper switch turned off to form a loop together with the alternating current power supply and the output load of the two-wire dimmer, such that the alternating current power supply charges the auxiliary source capacitor to obtain an auxiliary source voltage; in a case that the auxiliary source voltage reaches a certain value, the chopper switch is turned on and operates in a saturation state, such that the alternating current power supply stops charging the auxiliary source capacitor to reduce the loss of the circuit; in a case that the two-wire dimmer is required to output a chopper voltage, the loop which charges the auxiliary source capacitor is cut off. 
         [0025]    In the embodiments of the present invention, the chopper switch operates in a switch state instead of a linear state, so the loss of the auxiliary power supply circuit of the two-wire dimmer is small and the efficiency is high. In addition, the minimum chopper angle is not limited in the auxiliary power supply circuit of the two-wire dimmer, so the electromagnetic interference is small. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The accompanying drawings to be used in the description of the embodiments will be described briefly below, to make technical solutions according to the embodiments of the present invention or the prior art clearer. It is obvious that the accompany drawings in the following description are only some embodiments of the present invention. Other accompany drawings may be obtained by those skilled in the art according to these accompany drawings without any creative work. 
           [0027]      FIG. 1  is a diagram of an auxiliary power supply circuit of a two-wire dimmer in the prior art; 
           [0028]      FIG. 2  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a first embodiment of the present invention; 
           [0029]      FIG. 3  is a circuit diagram of a first implementation of a control device of the auxiliary power supply circuit according to the first embodiment of the present invention; 
           [0030]      FIG. 4  is a circuit diagram of a second implementation of the control device of the auxiliary power supply circuit according to the first embodiment of the present invention; 
           [0031]      FIG. 5  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a second embodiment of the present invention; 
           [0032]      FIG. 6  is a circuit diagram of an implementation of a control device of the auxiliary power supply circuit according to the second embodiment of the present invention; 
           [0033]      FIG. 7  is a circuit diagram of a first implementation of a chopper switch according to an embodiment of the present invention; 
           [0034]      FIG. 8  is a diagram of a waveform of an output voltage of the circuit shown in  FIG. 7 ; 
           [0035]      FIG. 9  is a circuit diagram of a second implementation of the chopper switch according to an embodiment of the present invention; 
           [0036]      FIG. 10  is a diagram of a waveform of an output voltage of the circuit shown in  FIG. 9 ; 
           [0037]      FIG. 11  is a circuit diagram of a third implementation of the chopper switch according to an embodiment of the present invention; 
           [0038]      FIG. 12  is a circuit diagram of a fourth implementation of the chopper switch according to an embodiment of the present invention; 
           [0039]      FIG. 13  is a structural diagram of an auxiliary power supply of a two-wire dimmer according to a third embodiment of the present invention; 
           [0040]      FIG. 14  is a circuit diagram of an implementation of a control device of the auxiliary power supply circuit according to the third embodiment of the present invention; 
           [0041]      FIG. 15  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a fourth embodiment of the present invention; 
           [0042]      FIG. 16  is a circuit diagram of an implementation of a control device of the auxiliary power supply circuit according to the fourth embodiment of the present invention; 
           [0043]      FIG. 17  is a circuit diagram of a fifth implementation of the chopper switch according to an embodiment of the present invention; 
           [0044]      FIG. 18  is a diagram of a waveform of an output voltage of the circuit shown in  FIG. 17 ; 
           [0045]      FIG. 19  is a circuit diagram of a sixth implementation of the chopper switch according to an embodiment of the present invention; 
           [0046]      FIG. 20  is a diagram of a waveform of an output voltage of the circuit shown in  FIG. 19 ; 
           [0047]      FIG. 21  is a circuit diagram of a seventh implementation of the chopper switch according to an embodiment of the present invention; 
           [0048]      FIG. 22  is a circuit diagram of an eighth implementation of the chopper switch according to an embodiment of the present invention; 
           [0049]      FIG. 23  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a fifth embodiment of the present invention; and 
           [0050]      FIG. 24  is a circuit diagram of an implementation of the auxiliary power supply circuit according to the fifth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    The technical solutions according to the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present invention. It is obvious that the described embodiments are only part but not all of embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in the present invention without any creative work belong to the protection scope of the present invention. 
         [0052]    In view of the above, an object of the present invention is to provide an auxiliary power supply circuit of a two-wire dimmer, to solve the defects in the prior art with a simple circuit and a lower cost. 
         [0053]    In order to make the objects, features and advantages of the present invention more apparent and better understood, the present invention will be described in further detail below in conjunction with the accompanying drawings and the embodiments. 
         [0054]    In the auxiliary power supply circuit of the two-wire dimmer according to the embodiments of the invention, in a case that the auxiliary source voltage is lower than a preset value, at least one chopper switch is turned off and the auxiliary source capacitor replaces the chopper switch turned off to form a loop together with the alternating current power supply and the output load of the two-wire dimmer, such that the alternating current power supply charges the auxiliary source capacitor to obtain an auxiliary source voltage; in a case that the auxiliary source voltage reaches a certain value, the chopper switch is turned on and operates in a saturation state, such that the alternating current power supply stops charging the auxiliary source capacitor, to reduce the loss of the circuit; in a case that the two-wire dimmer is required to output a chopper voltage, the loop which charges the auxiliary source capacitor is cut off. 
         [0055]    The auxiliary power supply circuit of the two-wire dimmer according to the embodiments of the present invention includes a chopper switch, an auxiliary source capacitor and a disconnecting switch. The auxiliary source capacitor and the disconnecting switch are connected in series to form a series branch, and the chopper switch is connected in parallel with the series branch. 
         [0056]    In a case that the disconnecting switch is on and the chopper switch is off, the auxiliary source capacitor is connected in parallel with the chopper switch and the auxiliary source capacitor is charged; in a case that the disconnecting switch is off or both the chopper switch and the disconnecting switch are on, the charging of the auxiliary source capacitor is stopped. 
         [0057]      FIG. 2  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a first embodiment of the present invention. The auxiliary power supply of the two-wire dimmer may include a chopper switch  10 , an auxiliary source capacitor  20 , a disconnecting switch  30  and a control device  40 . 
         [0058]    The auxiliary source capacitor  20  and the disconnecting switch  30  are connected in series to form a series branch, and the chopper switch  10  is connected in parallel with the series branch. 
         [0059]    The two ends of the chopper switch  10  are respectively connected to an end of an input alternating current power supply Vin and an output load end which is not connected to the input alternating current power supply. The other end of the output load is connected to the other end of the input alternating current power supply. 
         [0060]    In a case that the disconnecting switch  30  is on and the chopper switch  10  is off, the auxiliary source capacitor  20  is connected in parallel with the chopper switch  10  and the auxiliary source capacitor  20  is charged; in a case that the disconnecting switch  30  is off or both the chopper switch  10  and the disconnecting switch  30  are on, the charging of the auxiliary source capacitor  20  is stopped. 
         [0061]    The control device  40  detects an auxiliary source voltage and receives a chopper voltage control signal Vg, to output a signal to control the chopper switch  10  and the disconnecting switch  20  to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage and the state of the chopper voltage control signal Vg, so as to control the charging of the auxiliary source capacitor  20 . 
         [0062]    The two-wire dimmer outputs a chopper voltage or a non-chopper voltage. In a case that the chopper voltage is output, the chopper voltage is used for transferring an adjusting signal to a post-stage circuit by the two-wire dimmer. 
         [0063]    It should be noted that in the embodiments of the present invention, the chopper voltage control signal (shown as Vg in  FIG. 2 ) is a signal for controlling the output voltage of the two-wire dimmer. 
         [0064]    In a case that the chopper voltage control signal Vg is turning off the chopper switch  10 , the two-wire dimmer outputs a zero voltage; and in a case that the chopper voltage control signal Vg is not turning off the chopper switch  10 , the two-wire dimmer outputs a non-zero voltage. 
         [0065]    In a case that the chopper voltage control signal Vg is turning off the chopper switch  10 , the two-wire dimmer is to output a zero voltage, therefore, the auxiliary source capacitor  20  is not charged. The control device  40  outputs a first signal V 1  to control the chopper switch  10  to be off and outputs a second signal V 2  to control the disconnecting switch  30  to be off, thus the two-wire dimmer outputs a zero voltage. 
         [0066]    In a case that the chopper voltage control signal Vg is not turning off the chopper switch  10  and the auxiliary source voltage is lower than a lower limit value, the auxiliary source capacitor  20  needs to be charged. In this case, the control device  40  outputs a first signal V 1  to control the chopper switch  10  to be off and outputs a second signal V 2  to control the disconnecting switch  30  to be on. The voltage across the chopper switch  10  charges the auxiliary source capacitor  20  via the disconnecting switch  30 . If the alternating current input voltage Vin is a power network voltage (for example, 110 Vac, 220 Vac or 277 Vac), the alternating current input voltage Vin is far greater than the voltage across the chopper switch  10  since the auxiliary source voltage is generally controlled to be a voltage which ranges from 0 to 20 volts. Therefore, the output voltage V 0  of the two-wire dimmer is the difference between the input alternating current voltage Vin and the voltage across the chopper switch  10 , and thus is a non-zero voltage. 
         [0067]    In a case that the chopper voltage control signal Vg is not turning off the chopper switch  10  and the auxiliary source voltage is higher than an upper limit value, the auxiliary source capacitor  20  does not need to be charged. In this case, the control device  40  outputs a first signal V 1  to control the chopper switch  10  to be on and outputs a second signal V 2  to control the disconnecting switch  30  to be off, and the output voltage of the two-wire dimmer is the alternating current input voltage Vin, which is a non-zero voltage. 
         [0068]    The implementation of the auxiliary power supply circuit of the two-wire dimmer according to the first embodiment of the present invention will be described in detail below. 
         [0069]    In a first implementation of the auxiliary power supply circuit of the two-wire dimmer according to the first embodiment of the present invention, the control device may include a judging circuit and a disconnecting switch driving circuit. 
         [0070]    The judging circuit is configured to receive a chopper voltage control signal and output a signal to control the chopper switch and the disconnecting switch to be off in a case that the chopper voltage control signal is turning off the chopper switch; detect an auxiliary source voltage, compare the auxiliary source voltage with a preset voltage, and output a signal to control the chopper switch to be off in a case that the auxiliary source voltage is lower than a set lower limit value and the chopper voltage control signal is not turning off the chopper switch; and output a signal to control the chopper switch to be on in a case that the auxiliary source voltage is higher than a set upper limit value and the chopper voltage control signal is not turning off the chopper switch. 
         [0071]    The disconnecting switch driving circuit is configured to control the disconnecting switch to be on in a case that the chopper switch is off and the chopper voltage control signal is not turning off the chopper switch. 
         [0072]    It should be noted that in a case that the chopper voltage control signal is turning off the chopper switch, the chopper switch and the disconnecting switch are directly controlled to be off; and in a case that the chopper voltage control signal is not turning off the chopper switch, the chopper switch and the disconnecting switch are not controlled to be on or off according to the chopper voltage control signal, but are controlled to be on or off according to signals at the control ends of the chopper switch and the disconnecting switch respectively. 
         [0073]    In a case that the chopper voltage control signal controls the chopper switch or the disconnecting switch, the priority of the chopper voltage control signal is higher than the priority of the signal at the control end of the chopper switch or the disconnecting switch. 
         [0074]    In a case that the judging circuit receives a chopper voltage control signal which is turning off the chopper switch, the judging circuit directly outputs a signal to control the chopper switch and the disconnecting switch to be off without considering a comparison result of the auxiliary source voltage with the preset voltage; and in a case that the judging circuit receives a chopper voltage control signal which is turning off the chopper switch, the judging circuit controls the chopper switch and the disconnecting switch to be on or off according to a comparison result of the auxiliary source voltage with the preset voltage, specifically, the judging circuit outputs a signal to control the chopper switch to be off in a case that the auxiliary source voltage is lower than a set lower limit value, and outputs a signal to control the chopper switch to be on in a case that the auxiliary source voltage is higher than a set upper limit value. 
         [0075]    The first implementation of the control device of the auxiliary power supply circuit according to the first embodiment of the present invention may be as the circuit shown in  FIG. 3 .  FIG. 3  is a circuit diagram of the first implementation of the control device of the auxiliary power supply circuit according to the first embodiment of the present invention. In the circuit shown in  FIG. 3 , the chopper switch  10  consists of two MOS transistors Q 3  and Q 4 . 
         [0076]    As shown in  FIG. 3 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1  is connected in series with the disconnecting switch Q 2 , and is connected in series with two diodes (a ninth diode D 9  and a tenth diode D 10 ) respectively to form two series branches; and the series branches are respectively connected in parallel with the two MOS transistors of the chopper switch  10 . 
         [0077]    The series branches include a first series branch and a second series branch. In the first series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 , and the other end of the disconnecting switch Q 2  is connected to the cathode of the ninth diode D 9 . In the second series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 , and the other end of the disconnecting switch Q 2  is connected to the cathode of the tenth diode D 10 . 
         [0078]    The chopper switch  10  includes a third MOS transistor Q 3  and a fourth MOS transistor Q 4 . The source electrode of the third MOS transistor Q 3  and the source electrode of the fourth MOS transistor Q 4  are connected to the ground; the drain electrode of the third MOS transistor Q 3  and the anode of the ninth diode D 9  are connected to one input end of the input voltage Vin; the drain electrode of the fourth MOS transistor Q 4  and the anode of the tenth diode D 10  are connected to an end of the output load; the other end of the output load is connected to the other input end of the input voltage Vin; the gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4  are connected together, and as the control end of the chopper switch  10 , are connected to the output end of the control device  40 . 
         [0079]    As shown in  FIG. 3 , the control device  40  includes a judging circuit and a disconnecting switch driving circuit. 
         [0080]    The judging circuit may include a second resistor R 2 , a third resistor R 3 , a fourth resistor R 4 , a first comparator IC 1  and a fifth resistor R 5 . 
         [0081]    An end of the second resistor R 2 , as an input end of the control device  40 , is connected to the positive electrode of the auxiliary source capacitor C 1 , and an end of the third resistor R 3  is connected to the ground. 
         [0082]    The other end of the second resistor R 2  and the other end of the third resistor R 3  are connected to the non-inverted input end of the first comparator IC 1 , the inverted input end of the first comparator IC 1  is connected to a reference voltage Vref, and the fourth resistor R 4  is connected between the non-inverted input end and the output end of the first comparator IC 1 . 
         [0083]    The output end of the first comparator IC 1  is connected to an end of the fifth resistor R 5 , and the other end of the fifth resistor R 5 , as a first output end of the control device  40 , is connected to the control end of the chopper switch  10 . 
         [0084]    All devices of the judging circuit form a hysteresis comparator, and the preset voltage (i.e., the upper limit value and the lower limit value set for the auxiliary source voltage) is obtained according to a reference voltage Vref of the hysteresis comparator. 
         [0085]    The set lower limit value is 
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         [0086]    The disconnecting switch driving circuit includes a first resistor R 1 . 
         [0087]    An end of the first resistor R 1  is connected to the chopper voltage control signal Vg, and as a second output end of the control device  40 , is connected to the control end of the disconnecting switch Q 2 . The other end of the first resistor R 1  is connected to a common end of the disconnecting switch Q 2 , the ninth diode D 9  and the tenth diode D 10 , i.e., a high potential end of the disconnecting switch Q 2 . 
         [0088]    The control end of the chopper switch  10  (i.e., the gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4 ) and the control end of the disconnecting switch Q 2  are connected to the chopper voltage control signal Vg. 
         [0089]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0090]    As shown in  FIG. 3 , the chopper voltage control signal Vg may be provided by a chopper control circuit  50 . The chopper control circuit  50  is used to control the two-wire dimmer to output a chopper voltage. The two-wire dimmer outputs a zero voltage in a case that the chopper voltage control signal Vg is turning off the chopper switch  10 ; and the two-wire dimmer outputs a non-zero voltage in a case that the chopper voltage control signal Vg is not turning off the chopper switch  10 . 
         [0091]    It should be noted that in the embodiment of the present invention, the gate electrode driving current of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  is provided by a control signal Va output from the judging circuit of the control device  40  (as shown in  FIG. 3 ). The chopper voltage control signal Vg controls the third MOS transistor Q 3 , the fourth MOS transistor Q 4  and the disconnecting switch Q 2  to make them turned off, but does not control the third MOS transistor Q 3 , the fourth MOS transistor Q 4  and the disconnecting switch Q 2  to make them turned on. 
         [0092]    In a case that the chopper voltage control signal Vg is turning off the chopper switch  10 , the chopper voltage control signal Vg is at a low level and has a highest priority, therefore, the third MOS transistor Q 3  or the fourth MOS transistor Q 4  is controlled to be off, and the disconnecting switch Q 2  is off. The charging loop of the auxiliary source capacitor C 1  is cut off, the chopper switch  10  is off, and the two-wire dimmer outputs a zero voltage. 
         [0093]    In a case that the chopper voltage control signal Vg is not turning off the chopper switch  10 , the chopper voltage control signal Vg is not at the low level, which still can not drive the third MOS transistor Q 3 , the fourth MOS transistor Q 4  and the disconnecting switch Q 2  to be on, that is, the chopper voltage control signal Vg does not control the chopper switch  10  and the disconnecting switch  30 . In a case that the judging circuit detects that the auxiliary source voltage Vcc is lower than the set lower limit value, the output signal Va of the first comparator IC 1  is at a low level, which controls the chopper switch  10  to be off. In this case, since the chopper switch  10  is off, the first resistor R 1  in the disconnecting switch driving circuit outputs a driving voltage signal to the control end of the disconnecting switch Q 2  via the ninth diode D 9  or the tenth diode D 10 , to turn on the disconnecting switch Q 2 . Therefore, a charging loop for the auxiliary source capacitor C 1  is formed. 
         [0094]    In a case that the chopper voltage control signal Vg is not turning off the chopper switch  10 , the chopper voltage control signal Vg is not at the low level, which still can not drive the third MOS transistor Q 3 , the fourth MOS transistor Q 4  and the disconnecting switch Q 2  to be on, that is, the chopper voltage control signal Vg does not control the chopper switch  10  and the disconnecting switch  30 . In a case that the judging circuit detects that the auxiliary source voltage Vcc is higher than the set upper limit value, the output signal Va of the first comparator IC 1  is at a high level, which controls the chopper switch  10  to be on. In this case, the turn-on voltage drop of the chopper switch  10  is too low to turn on the ninth diode D 9  or the tenth diode D 10 , therefore, the disconnecting switch driving circuit can not provide a driving voltage signal to the disconnecting switch Q 2  and the disconnecting switch Q 2  is off. In this case, the charging loop for the auxiliary source capacitor C 1  can not be formed. 
         [0095]    Another implementation of the auxiliary power supply circuit is further provided according to the first embodiment of the present invention. In the second implementation of the auxiliary power supply circuit of the two-wire dimmer according to the first embodiment of the present invention, the control device may includes a judging circuit, a logic circuit and a disconnecting switch driving circuit. 
         [0096]    The judging circuit is configured to detect the auxiliary source voltage, compare the auxiliary source voltage with a preset voltage, output a first signal to the logic circuit in a case that the auxiliary source voltage is lower than a set lower limit value, and output a second signal to the logic circuit in a case that the auxiliary source voltage is higher than a set upper limit value. 
         [0097]    The logic circuit is configured to receive a chopper voltage control signal and control the disconnecting switch and the chopper switch to be off in a case that the chopper voltage control signal is turning off the chopper switch; receive an output signal of the judging circuit and control the chopper switch to be off in a case that the output signal of the judging circuit is the first signal; control the disconnecting switch to be off in a case that the output signal of the judging circuit is the second signal; and control the chopper switch to be on in a case that the output signal of the judging circuit is the second signal and the chopper voltage control signal is not turning off the chopper switch. 
         [0098]    The disconnecting switch driving circuit is configured to control the disconnecting switch to be on in a case that the chopper switch is off, the chopper voltage control signal is not turning off the chopper switch and the output signal of the judging circuit is the first signal. 
         [0099]    The second implementation of the control device of the auxiliary power supply circuit according to the first embodiment of the present invention may be as the circuit shown in  FIG. 4 .  FIG. 4  is a circuit diagram of the second implementation of the control device of the auxiliary power supply circuit according to the first embodiment of the present invention. 
         [0100]    In the circuit shown in  FIG. 4 , the chopper switch  10  consists of two MOS transistors Q 3  and Q 4 . The auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1 , the disconnecting switch Q 2  and two diodes (the ninth diode D 9  and the tenth diode D 10 ) connected in parallel form two series branches; the series branches are respectively connected in parallel with the two MOS transistors of the chopper switch  10 , and the series branches are the same as the series branch described in  FIG. 3 . 
         [0101]    The connection of the chopper switch  10  and the series branches in the circuit shown in  FIG. 4  is the same as that in  FIG. 3 , and the detailed description thereof is omitted herein. The circuit shown in  FIG. 4  differs from the circuit shown in  FIG. 3  as follows. 
         [0102]    As shown in  FIG. 4 , the judging circuit may include an eighth resistor R 8 , a ninth resistor R 9 , a tenth resistor R 10  and a second comparator IC 2 . The judging circuit forms a hysteresis comparator, as that shown in  FIG. 3 . The judging circuit outputs a first signal to the logic circuit in a case that the auxiliary source voltage is lower than a set lower limit value, and outputs a second signal to the logic circuit in a case that the auxiliary source voltage is higher than a set upper limit value. In the embodiment shown in  FIG. 4 , the first signal is a low level signal, and the second signal is a high level signal. 
         [0103]    The non-inverted input end of the second comparator IC 2  is connected to the positive electrode of the auxiliary source capacitor C 1  via the ninth resistor R 9 , the non-inverted input end of the second comparator IC 2  is connected to the negative electrode of the auxiliary source capacitor C 1  via the tenth resistor R 10 , the eighth resistor R 8  is connected between the non-inverted input end and the output end of the second comparator IC 2 , and the inverted input end of the second comparator IC 2  is connected to the reference voltage Vref. 
         [0104]    The logic circuit includes a thirteenth diode Ds 13 , a fourteenth diode Ds 14 , a fifth transistor Qs 5 , a sixth resistor R 6 , a seventh resistor R 7 , an eleventh diode Ds 11 , a second diode Ds 12  and a second auxiliary power supply Vs. 
         [0105]    The output end of the second comparator IC 2  is connected to the cathode of the thirteenth diode Ds 13 , and the anode of the thirteenth diode Ds 13 , as a first output end of the control device  40 , is connected to the control end of the chopper switch  10 . 
         [0106]    The cathode of the fourteenth diode Ds 14  is connected to an end of the sixth resistor R 6  and the collector of the fifth transistor Qs 5 ; the other end of the sixth resistor R 6  is connected to the positive electrode of the second auxiliary power supply Vs; the emitter of the fifth transistor Qs 5  is connected to the ground, and the base of the fifth transistor Qs 5  is connected to the output end of the second comparator IC 2 . 
         [0107]    An end of the seventh resistor R 7  is connected to the anode of the thirteenth diode Ds 13  which is the control end of the chopper switch  10 , and the other end of the seventh resistor R 7  is connected to the positive electrode of the second auxiliary power supply Vs. 
         [0108]    The first output end of the control device which is the anode of the thirteenth diode Ds 13  is connected to the chopper voltage control signal Vg via the eleventh diode Ds 11 , and the control end of the disconnecting switch  30  is connected to the chopper voltage control signal Vg via the twelfth diode Ds 12 . 
         [0109]    The disconnecting switch driving circuit includes an eleventh resistor R 11 . 
         [0110]    A common end of the eleventh resistor R 11  and the anode of the fourteenth diode Ds 14 , as a second output end of the control device  40 , is connected to the control end of the disconnecting switch Q 2 . 
         [0111]    The other end of the eleventh resistor R 11  is connected to a high potential end of the disconnecting switch Q 2  which is a common end of the disconnecting switch Q 2 , the ninth diode D 9  and the tenth diode D 10 . 
         [0112]    The control end of the chopper switch  10  is connected to the chopper voltage control signal Vg via the eleventh diode Ds 11 , and the control end of the disconnecting switch Q 2  is connected to the chopper voltage control signal Vg via the twelfth diode Ds 12 . Specifically, the control end of the chopper switch  10  (i.e., the gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4 ) is connected to the anode of the eleventh diode Ds 11 , and the cathode of the eleventh diode Ds 11  is connected to the chopper voltage control signal Vg; the control end of the disconnecting switch Q 2  is connected to the anode of the twelfth diode Ds 12 , and the cathode of the twelfth diode Ds 12  is connected to the chopper voltage control signal Vg. 
         [0113]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0114]    The chopper voltage control signal Vg in the second implementation shown in  FIG. 4  is the same as that shown in  FIG. 3 , and the detailed description thereof is omitted herein. 
         [0115]    The judging circuit detects the auxiliary source voltage, and in a case that the auxiliary source voltage Vcc is higher than a set upper limit value, the second comparator IC 2  outputs Va which is at a high level (that is, a second signal), and the thirteenth diode Ds 13  in the logic circuit is turned off, therefore, the judging circuit does not control the chopper switch  10 . By inverting of the fifth transistor Qs 5  in the logic circuit, the fourteenth diode Ds 14  is turned on, and the control end of the disconnecting switch Q 2  is at a low level, therefore, the judging circuit controls the disconnecting switch Q 2  to be off, and the auxiliary source capacitor C 1  is not charged. 
         [0116]    Based on the above, in a case that the chopper voltage control signal Vg is not turning off the chopper switch, the eleventh diode Ds 11  is turned off, therefore, the chopper voltage control signal Vg does not control the chopper switch  10 , the gate electrodes of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  are at a high level by the seventh resistor R 7  and the second auxiliary power supply Vs in the logic circuit, which provide the gate electrode driving current to the third MOS transistor Q 3  and the fourth MOS transistor Q 4  to make them turned on, and the output voltage V 0  of the two-wire dimmer is an alternating current input voltage Vin which is a non-zero voltage; and in a case that the chopper voltage control signal Vg is turning off the chopper switch, the eleventh diode Ds 11  is turned on, the gate electrodes of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are at a low level and the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are turned off since the priority of the chopper voltage control signal Vg is higher than the priority of other signals, therefore, the output voltage of the two-wire dimmer is a zero voltage. In addition, the disconnecting switch Q 2  is off, and the auxiliary source capacitor C 1  is not charged. 
         [0117]    The judging circuit detects the auxiliary source voltage, and in a case that the auxiliary source voltage Vcc is lower than a set lower limit value, the second comparator IC 2  outputs Va which is at a low level (that is, a first signal), and the fourteenth diode Ds 14  in the logic circuit is turned off, therefore, the judging circuit does not control the disconnecting switch Q 2 . The thirteenth diode Ds 13  in the logic circuit is turned on, and the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  are off. 
         [0118]    Based on the above, in a case that the chopper voltage control signal Vg is turning off the chopper switch, the eleventh diode Ds 11  and the twelfth diode Ds 12  are turned on, and the chopper switch  10  and the disconnecting switch Q 2  are off since the priority of the chopper voltage control signal is higher than the priority of other signals at the control end of the chopper switch  10  and the disconnecting switch Q 2 , therefore, the charging loop for the auxiliary source capacitor C 1  is not formed, and the two-wire dimmer outputs a zero voltage; and 
         [0119]    in a case that the chopper voltage control signal Vg is not turning off the chopper switch, the eleventh diode Ds 11  and the twelfth diode Ds 12  are turned off, therefore, the chopper voltage control signal Vg controls neither the chopper switch  10  nor the disconnecting switch Q 2 . In this case, by the ninth diode D 9  or the tenth diode D 10 , the eleventh resistor R 11  in the disconnecting switch driving circuit provides the driving voltage signal to the disconnecting switch Q 2 , such that the control end of the disconnecting switch Q 2  is at a high level, the disconnecting switch Q 2  is turned on, a charging loop for the auxiliary source capacitor C 1  is formed, and the voltage across the chopper switch  10  charges the auxiliary source capacitor by the disconnecting switch Q 2 . If the alternating current input voltage Vin is a power network voltage (for example, 110 Vac, 220 Vac or 277 Vac), the alternating current input voltage Vin is far greater than the voltage across the chopper switch  10  since the auxiliary source voltage Vcc is generally controlled to be a voltage which ranges from 0 to 20 volts. Therefore, the output voltage of the two-wire dimmer is the difference between the voltage across the chopper switch  10  and the alternating current input voltage Vin, and thus is a non-zero voltage. 
         [0120]    The embodiment described above only provides two implementations of the control device of the auxiliary power supply circuit of the two-wire dimmer according to the first embodiment of the present invention. In practical application, the control device of the auxiliary power supply circuit described in the first embodiment of the present invention may be but not limited to the two implementations described above. 
         [0121]      FIG. 5  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a second embodiment of the present invention. The circuit of the second embodiment shown in  FIG. 5  differs from the circuit of the first embodiment in that: the control device  40  detects the auxiliary source voltage and receives a chopper period control signal Vb and a chopper voltage control signal Vg, judges whether the chopper switch  10  is in a chopper period according to the chopper period control signal Vb, and outputs a signal to control the chopper switch  10  and the disconnecting switch  30  to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage, a state of the chopper voltage control signal Vg and whether the chopper switch  10  being in the chopper period, to control the charging of the auxiliary source capacitor  20 . 
         [0122]    Specifically, in a case that the auxiliary source voltage is lower than a set lower limit value and the chopper switch  10  is in a non-chopper period, the chopper switch  10  is controlled to be off and the disconnecting switch  30  is controlled to be on, to charge the auxiliary source capacitor  20 ; in a case that the auxiliary source voltage is not lower than the set lower limit value, or in a case that the auxiliary source voltage is lower than the set lower limit value and the chopper switch  10  is in a chopper period, the chopper switch  10  and the disconnecting switch  30  are controlled according to the chopper voltage control signal Vg, such that the two-wire dimmer outputs a corresponding voltage. 
         [0123]    The chopper period control signal Vb may be output from a chopper control circuit (not shown in the figures). The chopper period control signal Vb has two states: the chopper period control signal Vb is in a first state in a case that the chopper switch  10  is in a chopper period; and the chopper period control signal Vb is in a second state in a case that the chopper switch  10  is in a non-chopper period. The control device  40  may judge whether the chopper switch  10  is in a chopper period or a non-chopper period according to the state of the chopper period control signal Vb. The control device  40  controls the auxiliary source capacitor to be charged in the non-chopper period according to the chopper period control signal Vb in a case that the auxiliary source voltage is lower than a set lower limit value. 
         [0124]    An implementation of the auxiliary power supply circuit is provided according to the second embodiment of the present invention. In the auxiliary power supply circuit of the two-wire dimmer according to the second embodiment of the present invention, the control device includes a first judging circuit, a second judging circuit, a logic circuit and a disconnecting switch driving circuit. 
         [0125]    The first judging circuit is configured to detect the auxiliary source voltage, compare the auxiliary source voltage with a preset voltage, output a first signal to the logic circuit in a case that the auxiliary source voltage is lower than a set lower limit value, and output a second signal to the logic circuit in a case that the auxiliary source voltage is higher than a set upper limit value. 
         [0126]    The second judging circuit is configured to detect the chopper period control signal, judge whether the chopper switch is in a chopper period according to the chopper period control signal, output a third signal to the logic circuit in a case that the chopper switch is in a chopper period, and output a fourth signal to the logic circuit in a case that the chopper switch is in a non-chopper period. 
         [0127]    The logic circuit is configured to receive an output signal of the first judging circuit, an output signal of the second judging circuit and a chopper voltage control signal, control the chopper switch to be on in a case that the first judging circuit outputs the second signal and the chopper switch control signal is not turning off the chopper switch or in a case that the second judging circuit outputs the third signal and the chopper switch control signal is not turning off the chopper switch; control the chopper switch to be off in a case that the first judging circuit outputs the first signal and the second judging circuit outputs the fourth signal or in a case that the chopper switch control signal is turning off the chopper switch; and control the disconnecting switch to be off in a case that the chopper switch control signal is turning off the chopper switch. 
         [0128]    The disconnecting switch driving circuit controls the disconnecting switch to be on in a case that the chopper switch is off and the chopper voltage control signal is not turning off the chopper switch. 
         [0129]    Specifically, the implementation of the control device of the auxiliary power supply circuit according to the second embodiment of the present invention may be as the circuit shown in  FIG. 6 .  FIG. 6  is a circuit diagram of an implementation of a control device of the auxiliary power supply circuit according to the second embodiment of the present invention. As shown in  FIG. 6 , the chopper switch  10  consists of two MOS transistors Q 3  and Q 4 . 
         [0130]    As shown in  FIG. 6 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1 , the disconnecting switch Q 2  and two diodes connected in parallel (the ninth diode D 9  and the tenth diode D 10 ) form a series branch; and the series branch is connected in parallel with the chopper switch  10 . 
         [0131]    Specifically, in the series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 , and the other end of the disconnecting switch Q 2  is connected to the cathode of the ninth diode D 9  and the cathode of the tenth diode D 10 . 
         [0132]    The chopper switch  10  includes a third MOS transistor Q 3  and a fourth MOS transistor Q 4 . The source electrode of the third MOS transistor Q 3  and the source electrode of the fourth MOS transistor Q 4  are connected to the ground; the drain electrode of the third MOS transistor Q 3  and the anode of the ninth diode D 9  are connected to an input end of the input voltage Vin; the drain electrode of the fourth MOS transistor Q 4  and the anode of the tenth diode D 10  are connected to an end of the output load, and the other end of the load is connected to the other input end of the input voltage Vin; and the gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4  are connected together, and as the control end of the chopper switch  10 , are connected to the output end of the control device  40 . 
         [0133]    As shown in  FIG. 6 , the control device  40  includes a first judging circuit, a second judging circuit, a logic circuit and a disconnecting switch driving circuit. 
         [0134]    The first judging circuit includes a thirteenth resistor R 13 , a fourteenth resistor R 14 , a fifteenth resistor R 15 , a sixteenth resistor R 16  and a third comparator IC 3 . The first judging circuit forms a hysteresis comparator, as the judging circuit in  FIG. 3 . In this embodiment, a first signal and a second signal, being signals output from the first judging circuit, are a low level signal and a high level signal respectively. 
         [0135]    An end of the thirteenth resistor R 13 , as an input end of the control device  40 , is connected to the positive electrode of the auxiliary source capacitor C 1 , and an end of the fourteenth resistor R 14  is connected to the ground. 
         [0136]    The other end of the thirteenth resistor R 13  and the other end of the fourteenth resistor R 14  are connected to the non-inverted input end of the third comparator IC 3 ; the inverted input end of the third comparator IC 3  is connected to a reference voltage Vref, and the fifteenth resistor R 15  is connected between the non-inverted input end and the output end of the third comparator IC 3 . 
         [0137]    The output end of the third comparator IC 3  is connected to an end of the sixteenth resistor R 16 , and the other end of the sixteenth resistor R 16  is connected to the anode of the fifteenth diode Ds 15 . 
         [0138]    The second judging circuit includes a sixth transistor Qs 6 , a seventeenth resistor R 17  and a second auxiliary power supply Vs. In this embodiment, a third signal and a fourth signal, being signals output from the second judging circuit, are a high level signal and a low level signal respectively. 
         [0139]    The base of the sixth transistor Qs 6  is connected to the chopper period control signal Vb output from the chopper control circuit  60 , the emitter of the sixth transistor Qs 6  is connected to the ground, the collector of the sixth transistor Qs 6  is connected to an end of the seventeenth resistor R 17  and the anode of the sixteenth diode Ds 16 , and the other end of the seventeenth resistor R 17  is connected to the positive electrode of the second auxiliary power supply Vs. 
         [0140]    The logic circuit includes a twenty-fourth resistor R 24 , a fifteenth diode Ds 15  and a sixteenth diode Ds 16 . 
         [0141]    The cathode of the sixteenth diode Ds 16  and the cathode of the fifteenth diode Ds 15  are connected together, and as a first output end of the control device  40 , are connected to the control end of the chopper switch  10  and an end of the twenty-fourth resistor R 24 , and the other end of the twenty-fourth resistor R 24  is connected to the ground. 
         [0142]    The disconnecting switch driving circuit includes a twelfth resistor R 12 . 
         [0143]    An end of the twelfth resistor R 12  is connected to the chopper voltage control signal Vg and as the first output end of the control device  40 , is connected to the control end of the disconnecting switch Q 2 . 
         [0144]    The other end of the twelfth resistor R 12  is connected to a high potential end of the disconnecting switch Q 2  which is a common end of the disconnecting switch Q 2 , the ninth diode D 9  and the tenth diode D 10 . 
         [0145]    The control end of the chopper switch  10  (i.e., the gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4 ) and the control end of the disconnecting switch Q 2  are connected to the chopper voltage control signal Vg output from the chopper control circuit  60 . 
         [0146]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0147]    In the circuit shown in  FIG. 6 , the chopper period control signal Vb has two states: a high level state and a low level state. 
         [0148]    The auxiliary source capacitor  10  is only charged in a non-chopper period. That is, in a chopper period, the control device  40  controls the disconnecting switch  30  and the chopper switch  10  such that the auxiliary source capacitor  10  is not charged, no matter whether the auxiliary source voltage Vcc is lower than a low limit value. 
         [0149]    The second judging circuit detects the chopper period control signal Vb. In a case that the chopper switch  10  is in a chopper period, the chopper period control signal Vb is at a low level, the second judging circuit outputs a high level (that is, the third signal) to the logic circuit by inverting of the sixth transistor Qs 6 , the sixteenth diode Ds 16  in the logic circuit is turned on, and the second judging circuit controls the gate electrodes of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  to be high level. Then, in a case that the gate electrode of the chopper switch  10  is at a high level under the control of a signal output from the second judging circuit via the logic circuit and the chopper voltage control signal Vg is not turning off the chopper switch, the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are turned on, but the turn-on voltage drops are low, such that the ninth diode D 9  and the tenth diode D 10  are turned off, the disconnecting switch driving circuit can not provide the driving voltage signal to the disconnecting switch Q 2 , therefore, the disconnecting switch Q 2  is off, and the auxiliary source capacitor C 1  is not charged. 
         [0150]    In a case that the gate of the chopper switch  10  is at a high level under the control of a signal output from the second judging circuit via the logic circuit and the chopper voltage control signal Vg is turning off the chopper switch, the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are turned off, and the ninth diode D 9  and the tenth diode D 10  are turned on. However, since the chopper voltage control signal Vg is turning off the chopper switch and has a priority higher than other signals, the control end of the disconnecting switch Q 2  is at a low level under the control of the chopper voltage control signal Vg, therefore, the disconnecting switch Q 2  is turned off, and the auxiliary source capacitor C 1  is not charged. 
         [0151]    The second judging circuit detects the chopper period control signal Vb, the two-wire dimmer does not output the zero voltage in a case that the chopper switch  10  is in a non-chopper period, therefore, the chopper voltage control signal Vg is not turning off the chopper switch, that is, the chopper voltage control signal Vg controls neither the chopper switch nor the disconnecting switch; and since the chopper switch  10  is in a non-chopper period, the chopper period control signal Vb is at the high level rather than the low level, the second judging circuit outputs a low level signal (i.e., the fourth signal) to the logic circuit by the inverting of the sixth transistor Qs 6  of the second judging circuit, the sixteenth diode Ds 16  in the logic circuit is turned off, therefore, the second judging circuit does not control the chopper switch  10  by the logic circuit. 
         [0152]    Based on the above, the first judging circuit detects the auxiliary source voltage Vcc. In a case that the auxiliary source voltage Vcc is higher than a set upper limit value, Va output from the third comparator IC 3  is at a high level (i.e., the second signal), the fifteenth diode Ds 15  in the logic circuit is turned on, the gate electrodes of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  are at high level, and the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are turned on, but the turn-on voltage drops are low, such that the ninth diode D 9  and the tenth diode D 10  are turned off, therefore, the disconnecting switch driving circuit can not provide the driving voltage to the disconnecting switch Q 2 , and the auxiliary source capacitor C 1  is not charged; and 
         [0153]    in a case that the auxiliary source voltage Vcc is lower than a set lower limit value, Va output from the third comparator IC 3  is at a low level (i.e., the first signal), the fifteenth diode Ds 15  in the logic circuit is turned off, that is, the first judging circuit does not control the chopper switch  10 . Since all of the first judging circuit, the second judging circuit and the chopper voltage control signal Vg do not control the chopper switch  10 , the gate electrodes of the third MOS transistor Q 3  and the fourth MOS transistor Q 4  of the chopper switch  10  are at low levels under the action of the twenty-fourth resistor R 24  in the logic circuit, and the third MOS transistor Q 3  and the fourth MOS transistor Q 4  are turned off, but the ninth diode D 9  and the tenth diode D 10  are turned on due to the voltage drops, such that the disconnecting switch driving circuit provides a driving voltage to the disconnecting switch Q 2  via the twelfth resistor R 12 , the control end of the disconnecting switch Q 2  is at a high level, the disconnecting switch Q 2  is turned on, and the auxiliary source capacitor C 1  is charged. 
         [0154]    The embodiment described above only provides one implementation of the control device of the auxiliary power supply circuit of the two-wire dimmer according to the second embodiment of the present invention. In practical application, the control device of the auxiliary power supply circuit described in the second embodiment of the present invention may be but not limited to the implementation described above. 
         [0155]    In the implementations of the control device of the auxiliary power supply circuit of the two-wire dimmer according to the two embodiments described above, the chopper switch  10  consists of two MOS transistors. In practical application, the chopper switch  10  may be implemented in many ways. Several implementations of the chopper switch are described in detail below. 
         [0156]      FIG. 7  is a circuit diagram of a first implementation of the chopper switch according to an embodiment of the present invention. As shown in  FIG. 7 , the chopper switch  10  consists of a rectifier bridge and a unidirectional switch. 
         [0157]    As shown in  FIG. 7 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1  and the disconnecting switch Q 2  are connected in series to form a series branch; and the series branch is connected in parallel with the output end of the rectifier bridge of the chopper switch  10 , an input end of the rectifier bridge of the chopper switch  10  is connected between an end of the input voltage Vin and an end of the output load, and the other end of the output load is connected to the other end of the input voltage Vin. 
         [0158]    In the series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, and the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 . 
         [0159]    Specifically, an end of the series branch which is the other end of the disconnecting switch Q 2  is connected to a positive output end of the rectifier bridge of the chopper switch  10 ; and the other end of the series branch which is the negative electrode of the auxiliary source capacitor C 1  is connected to a negative output end of the rectifier bridge of the chopper switch  10 . 
         [0160]    The chopper switch  10  is a bi-direction switch consisting of a switch transistor Q 1  and a rectifier bridge, in which the rectifier bridge consists of a first diode D 1 , a second diode D 2 , a third diode D 3  and a fourth diode D 4 . 
         [0161]    The source electrode of the switch transistor Q 1  is connected to a common end of the series branch and the ground, and the drain electrode of the switch transistor Q 1  is connected to the other end of the series branch. 
         [0162]    The first diode D 1  is connected in series with the second diode D 2 , and the cathode of the first diode D 1  is connected to the anode of the second diode D 2 . 
         [0163]    The third diode D 3  is connected in series with the fourth diode D 4 , and the cathode of the third diode D 3  is connected to the anode of the fourth diode D 4 . 
         [0164]    The anode of the first diode D 1  and the anode of the third diode D 3  are connected to the source electrode of the switch transistor Q 1 ; and the cathode of the second diode D 2  and the cathode of the fourth diode D 4  are connected to the drain electrode of the switch transistor Q 1 . 
         [0165]    A common end of the first diode D 1  and the second diode D 2 , as an end of the two-wire dimmer, is connected to the end of the input voltage Vin; a common end of the third diode D 3  and the fourth diode D 4 , as the other end of the two-wire dimmer, is connected to the end of the output load, and the voltage output from the two-wire dimmer is Vo; the two-wire dimmer and the output load are connected in series and then connected in parallel with the alternating current input voltage Vin. 
         [0166]    The gate electrode of the switch transistor Q 1  is connected to a first signal V 1 ; and the control end of the disconnecting switch Q 2  is connected to a second signal V 2 . 
         [0167]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0168]    It should be noted that the switch transistor Q 1  which forms the chopper switch  10  in  FIG. 7  is only illustrated as a MOS transistor. In practical application, any unidirectional switch transistor may be used as the switch transistor Q 1  shown in the figures to form the chopper switch in the embodiment of the present invention. 
         [0169]    In the circuit shown in  FIG. 7 , in a case that the switch transistor Q 1  is controlled to be off and the disconnecting switch Q 2  is controlled to be on, the two-wire dimmer obtains the auxiliary source voltage, the output voltage of the two-wire dimmer, which is a voltage V 0  between two ends of the load, is a difference between the input voltage Vin and the auxiliary source voltage Vcc; in a case that the switch transistor Q 1  is controlled to be on and the disconnecting switch Q 2  is controlled to be off, the auxiliary source capacitor C 1  is discharged to an auxiliary source load (not shown in the figures), the output voltage V 0  of the two-wire dimmer is equal to the input voltage Vin; and in a case that the switch transistor Q 1  is controlled to be off and the disconnecting switch Q 2  is controlled to be off, the auxiliary source capacitor C 1  is discharged, and the output voltage V 0  of the dimmer is zero. 
         [0170]    In the auxiliary power supply circuit shown in  FIG. 7 , if the two-wire dimmer outputs a zero voltage and a non-zero voltage alternately in half period of the alternating current voltage Vin, the output voltage of the two-wire dimmer is a chopper voltage. Specifically, in a case that the chopper voltage control signal Vg of the circuit shown in  FIG. 7  is a control signal of a trailing edge dimmer, the waveform of the output voltage V 0  is shown in  FIG. 8 . 
         [0171]    In  FIG. 8 , the dotted lines indicate the input voltage Vin of the two-wire dimmer which is a sinusoidal alternating current; and the solid lines indicate the output voltage V 0  of the two-wire dimmer which is the chopper voltage when the auxiliary source capacitor is not charged. 
         [0172]      FIG. 9  is a circuit diagram of a second implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 9 , the chopper switch  10  consists of a unidirectional switch. Compared with the circuit shown in  FIG. 7 , the circuit shown in  FIG. 9  further includes a rectifier device D 5  connected in series with the auxiliary source capacitor C 1  and the disconnecting switch Q 2 . 
         [0173]    As shown in  FIG. 9 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1 , the disconnecting switch Q 2  and the rectifier device D 5  are connected in series to form a series branch; the series branch and the chopper switch  10  are connected in parallel and are connected between the input voltage Vin and the output load. 
         [0174]    In the series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to an end of the output load, and the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 ; the other end of the disconnecting switch Q 2  is connected to the cathode of the rectifier device D 5 , and the anode of the rectifier device D 5  is connected to an end of the input voltage Vin. 
         [0175]    The chopper switch  10  includes a MOS transistor Q 1 . The source electrode of the MOS transistor Q 1  is connected to an end of the output load, and the drain electrode of the MOS transistor Q 1  is connected to the series branch and an end of the input voltage Vin. The two-wire dimmer and the load are connected in series and then connected in parallel with the input voltage Vin. 
         [0176]    The gate electrode of the MOS transistor Q 1  is connected to a first signal V 1 ; and the control end of the disconnecting switch Q 2  is connected to a second signal V 2 . 
         [0177]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0178]    The operating principle of the circuit shown in  FIG. 9  is similar to that in  FIG. 7 , and the description thereof is omitted. The circuit shown in  FIG. 9  differs from the circuit shown in  FIG. 7  in that: a chopper voltage is output in one half period and the body diode of the MOS transistor Q 1  is turned on in the other half period in a case that the two-wire dimmer outputs a chopper voltage. That is, the two-wire dimmer outputs a chopper voltage in one half period and outputs an alternating current input voltage in the other half period during an alternating current period. Specifically, in a case that the chopper voltage control signal Vg of the circuit shown in  FIG. 9  is a control signal of a trailing edge dimmer, the waveform of the output voltage is shown as  FIG. 10 . 
         [0179]    It should be noted that the MOS transistor is taken as an example to form the chopper switch  10  in  FIG. 9 . In practical application, the switch transistor Q 1  shown in  FIG. 9  may be replaced by inversely connecting a unidirectional switch transistor with a diode in parallel, to form the chopper switch in the embodiment of the present invention. For example, the chopper switch  10  may be as shown in  FIG. 11 . 
         [0180]      FIG. 11  is a circuit diagram of a third implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 11 , the chopper switch  10  includes a unidirectional switch. Compared with the circuit shown in  FIG. 9 , a switch transistor Q 1  is inversely connected in parallel with a diode D 6  in the circuit shown in  FIG. 11  to replace the MOS transistor Q 1  in  FIG. 9 . 
         [0181]    As shown in  FIG. 11 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1 , the disconnecting switch Q 2  and the rectifier device D 5  are connected in series to form a series branch; the series branch and the chopper switch  10  are connected in parallel between the input voltage Vin and the output load. 
         [0182]    In the series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to an end of the output load, and the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 ; the other end of the disconnecting switch Q 2  is connected to the cathode of the rectifier device D 5 , and the anode of the rectifier device D 5  is connected to an end of the input voltage Vin. 
         [0183]    The chopper switch  10  includes a switch transistor Q 1  and a sixth diode D 6 , the emitter of the switch transistor Q 1  is connected to an end of the output load, and the collector of the switch transistor Q 1  is connected to the series branch and an end of the input voltage Vin. 
         [0184]    The cathode of the sixth diode D 6  is connected to the collector of the switch transistor Q 1 , and the anode of the sixth diode D 6  is connected to the emitter of the switch transistor Q 1 . 
         [0185]    The gate electrode of the switch transistor Q 1  is connected to the first control signal V 1 ; and the control end of the disconnecting switch Q 2  is connected to the second control signal V 2 . 
         [0186]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0187]    The operating principle of the circuit shown in  FIG. 11  is similar as that in  FIG. 9 , and the detailed description thereof is omitted. 
         [0188]      FIG. 12  is a circuit diagram of a fourth implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 12 , the chopper switch  10  consists of two MOS transistors. The chopper switches according to the embodiments described above in  FIG. 3 ,  FIG. 4  and  FIG. 6  are described by taking the chopper switch in this embodiment as an example. 
         [0189]    As shown in  FIG. 12 , the auxiliary source capacitor  20  is C 1 , and the disconnecting switch  30  is Q 2 ; the auxiliary source capacitor C 1  and the disconnecting switch Q 2  are connected in series with two diodes to form two series branches; and the series branches are connected in parallel with the switch transistors in the chopper switch  10  respectively. 
         [0190]    In the first series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 , and the other end of the disconnecting switch Q 2  is connected to the cathode of a seventh diode D 7 . 
         [0191]    In the second series branch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to an end of the disconnecting switch Q 2 , and the other end of the disconnecting switch Q 2  is connected to the cathode of an eighth diode D 8 . 
         [0192]    The chopper switch  10  includes a third MOS transistor Q 3  and a fourth MOS transistor Q 4 . The source electrode of the third MOS transistor Q 3  and the source electrode of the fourth MOS transistor Q 4  are connected to the ground. 
         [0193]    The first series branch is connected in parallel with the third MOS transistor Q 3  of the chopper switch  10 , and the second series branch is connected in parallel with the fourth MOS transistor Q 4  of the chopper switch  10 . 
         [0194]    Specifically, an end of the first series branch (i.e., the anode of the seventh diode D 7 ) is connected to the drain electrode of the third MOS transistor Q 3 , and the other end of the first series branch (i.e., the negative electrode of the auxiliary source capacitor C 1 ) is connected to the source electrode of the third MOS transistor Q 3 ; an end of the second series branch (i.e., the anode of the eighth diode D 8 ) is connected to the drain electrode of the fourth MOS transistor Q 4 , and the other end of the second series branch (i.e., the negative electrode of the auxiliary source capacitor C 1 ) is connected to the source electrode of the fourth MOS transistor Q 4 . 
         [0195]    The drain electrode of the third MOS transistor Q 3  is connected to an end of the input voltage Vin, the drain electrode of the fourth MOS transistor Q 4  is connected to an end of the output load, and the other end of the output load is connected to the other end of the input voltage Vin. 
         [0196]    The gate electrode of the third MOS transistor Q 3  and the gate electrode of the fourth MOS transistor Q 4  are connected to a first control signal V 1 ; and the control end of the disconnecting switch Q 2  is connected to a second control signal V 2 . 
         [0197]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0198]    The operating principle of the circuit shown in  FIG. 12  is similar to that in  FIG. 7 , and the detailed description thereof is omitted. 
         [0199]    All of the implementations of the control device described in the first embodiment and the second embodiment of the present invention may be applied to the circuits of the four chopper switches provided in  FIG. 7  to  FIG. 12 . 
         [0200]    In the embodiments shown in  FIG. 7  to  FIG. 12 , the disconnecting switch Q 2  may be any unidirectional switch transistors. Moreover, in the embodiments shown in  FIG. 7  to  FIG. 12 , the first control signal V 1  and the second control signal V 2  are connected to the output ends of the control device  40  according to the specific implementation. 
         [0201]    Preferably, in the embodiments of the present invention, the chopper switch may be one or more; and each of the chopper switches may be a unidirectional switch or a bi-directional switch. 
         [0202]    Preferably, the series branch connected in parallel with the chopper switch may be one or more. 
         [0203]    Another auxiliary power supply circuit of a two-wire dimmer is further provided according to an embodiment of the present invention. Compared with the circuit provided in the embodiments described above, the circuit includes a chopper switch, an auxiliary source capacitor, a disconnecting switch and a rectifier device. 
         [0204]    The rectifier device and the auxiliary source capacitor are connected in series to form a series branch; the disconnecting switch and the series branch are connected in parallel to form a parallel branch; and then the chopper switch is connected in series with the parallel branch. 
         [0205]    In a case that the disconnecting switch is off, the auxiliary source capacitor is connected in series with the chopper switch, and the auxiliary source capacitor is charged via the rectifier device; and in a case that the disconnecting switch is on, the charging of the auxiliary source capacitor is stopped. 
         [0206]      FIG. 13  is a structural diagram of an auxiliary power supply of a two-wire dimmer according to a third embodiment of the present invention. The auxiliary power supply of the two-wire dimmer may include a chopper switch  100 , an auxiliary source capacitor  200 , a disconnecting switch  300 , a rectifier device  400  and a control device  500 . 
         [0207]    The rectifier device  400  and the auxiliary source capacitor  200  are connected in series to form a series branch; the disconnecting switch  300  and the series branch are connected in parallel to form a parallel branch; and then the chopper switch  100  is connected in series with the parallel branch. 
         [0208]    The two ends of the chopper switch  100  are respectively connected to an end of the input alternating current power supply Vin and an end of the parallel branch, the other end of the parallel branch is connected to an output load end which is not connected to the alternating current power supply Vin, and the other end of the load is connected to the other end of the input alternating current power supply. 
         [0209]    In a case that the disconnecting switch  300  is off, the auxiliary source capacitor  200  is connected in series with the chopper switch  100 , and the alternating current power supply Vin charges the auxiliary source capacitor  200  via the rectifier device  400  when the chopper switch  100  is on; in a case that the disconnecting switch  300  is on, the charging of the auxiliary source capacitor  200  is stopped. 
         [0210]    The control device  500  detects the auxiliary source voltage and receives a chopper voltage control signal Vg, outputs a signal to control the disconnecting switch  300  and the chopper switch  100  to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage and a state of the chopper voltage control signal Vg, and charges the auxiliary source capacitor  200  via the rectifier device  400 . 
         [0211]    In  FIG. 13 , in a case that the auxiliary source voltage is lower than a set lower limit value and the chopper voltage control signal Vg is not turning off (i.e., turning on) the chopper switch  100 , the control device  500  controls the auxiliary source capacitor  200  to be charged. 
         [0212]    Here, the two-wire dimmer outputs a chopper voltage or a non-chopper voltage. In a case that a chopper voltage is output, the chopper voltage is used to transfer an adjusting signal by the two-wire dimmer. 
         [0213]    It should be noted that in the embodiment of the present invention, the chopper voltage control signal (for example, Vg shown in  FIG. 13 ) is a signal for controlling the output voltage of the two-wire dimmer. In a case that the chopper voltage control signal Vg is turning off the chopper switch  100 , the two-wire dimmer outputs a zero voltage; and in a case that the chopper voltage control signal Vg is not turning off the chopper switch  100 , the two-wire dimmer outputs a non-zero voltage. 
         [0214]    In a case that the chopper voltage control signal Vg is turning off the chopper switch  100 , the control device  500  outputs a first signal V 1  to control the chopper switch  100  to be off, and outputs a second signal V 2  to control the disconnecting switch  300  to be on, and the two-wire dimmer outputs a zero voltage. 
         [0215]    In a case that the chopper voltage control signal Vg is not turning off the chopper switch  100 , the control device  500  outputs the first signal V 1  to control the chopper switch  100  to be on. In a case that the auxiliary source voltage is lower than a set lower limit value and the auxiliary source capacitor  200  needs to be charged, the control device  500  outputs the second signal V 2  to control the disconnecting switch  300  to be off, and the voltage across the disconnecting switch  300  charges the auxiliary source capacitor  200  via the rectifier device  400 . If the alternating current input voltage Vin is a power network voltage (for example, 110 Vac, 220 Vac or 277 Vac), the alternating current input voltage Vin is far greater than the voltage across the chopper switch  100  since the auxiliary source voltage is usually a voltage which ranges from 0 to 20 volts. Therefore, the output voltage of the two-wire dimmer is the difference between the alternating current input voltage Vin and the voltage across the chopper switch  100 , and thus is a non-zero voltage. 
         [0216]    In a case that the chopper switch control signal Vg is not turning off the chopper switch  100 , the control device  500  outputs the first signal V 1  to control the chopper switch  100  to be on, and in a case that the auxiliary source voltage is higher than a set upper limit value and the auxiliary source capacitor  200  does not need to be charged, the control device  500  outputs the second signal V 2  to control the disconnecting switch  300  to be on, and the output voltage of the two-wire dimmer is the alternating current input voltage Vin, which is a non-zero voltage. 
         [0217]    An implementation of the control device of the auxiliary power supply circuit of the two-wire dimmer according to the third embodiment of the present invention is described in detail below. 
         [0218]    A specific implementation of the auxiliary power supply circuit is provided according to the third embodiment of the present invention. In the auxiliary power supply circuit of the two-wire dimmer according to the third embodiment of the present invention, the control device may include a first judging circuit, a second judging circuit and a logic circuit. 
         [0219]    The first judging circuit is configured to detect the auxiliary source voltage, compare the auxiliary source voltage with a preset voltage, output a first signal to the logic circuit in a case that the auxiliary source voltage is lower than a set lower limit value, and output a second signal to the logic circuit in a case that the auxiliary source voltage is higher than a set upper limit value. 
         [0220]    The second judging circuit is configured to detect the chopper voltage control signal, output a third signal to the logic circuit in a case that the chopper voltage control signal is turning off the chopper switch, and output a fourth signal to the logic circuit in a case that the chopper voltage control signal is not turning off the chopper switch. 
         [0221]    The logic circuit is configured to receive an output signal of the first judging circuit, an output signal of the second judging circuit and a chopper voltage control signal, control the disconnecting switch to be on in a case that the first judging circuit outputs the second signal or the second judging circuit outputs the third signal; control the disconnecting switch to be off in a case that the first judging circuit outputs the first signal and the second judging circuit outputs the fourth signal; control the chopper switch to be off in a case that the chopper switch control signal is turning off the chopper switch; and control the chopper switch to be on in a case that the chopper switch control signal is not turning off the chopper switch. 
         [0222]    An implementation of the control device of the auxiliary power supply circuit according to the third embodiment of the present invention may be as the circuit shown in  FIG. 14 .  FIG. 14  is a circuit diagram of an implementation of the control device of the auxiliary power supply circuit according to the third embodiment of the present invention. In the circuit shown in  FIG. 14 , the chopper switch  100  consists of two MOS transistors. 
         [0223]    As shown in  FIG. 14 , the auxiliary source capacitor  200  is C 1 , the disconnecting switch  300  includes a sixth switch transistor Q 6  and a seventh switch transistor Q 7 , and the rectifier device includes a seventeenth diode D 17  and an eighteenth diode D 18 . 
         [0224]    In the parallel branch consisting of the auxiliary source capacitor, the rectifier device and the disconnecting switch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, and the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the seventeenth diode D 17  and the cathode of the eighteenth diode D 18 ; the two ends of the sixth switch transistor Q 6  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the seventeenth diode D 17 ; and the two ends of the seventh switch transistor Q 7  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the eighteenth diode D 18 . 
         [0225]    The chopper switch  100  includes an eighth MOS transistor Q 8  and a ninth MOS transistor Q 9 . 
         [0226]    The source electrode of the eighth MOS transistor Q 8  is connected to a common end of the sixth switch transistor Q 6  and the anode of the seventeenth diode D 17 , and the drain electrode of the eighth MOS transistor Q 8  is connected to an end of the input voltage Vin. 
         [0227]    The source electrode of the ninth MOS transistor Q 9  is connected to a common end of the seventh switch transistor Q 7  and the anode of the eighteenth diode D 18 , and the drain electrode of the ninth MOS transistor Q 9  is connected to an end of the output load. 
         [0228]    The other end of the alternating current input voltage Vin is connected to the other end of the output load. 
         [0229]    The gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9  are connected together, and as the control end of the chopper switch  100 , are connected to the output end of the control device  500 . The control end of the sixth switch transistor Q 6  and the control end of the seventh switch transistor Q 7  are connected together and are used as the control end of the disconnecting switch  300 . 
         [0230]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0231]    As shown in  FIG. 14 , the control device  500  includes a first judging circuit, a second judging circuit and a logic circuit. 
         [0232]    The first judging circuit includes an eighteenth resistor R 18 , a nineteenth resistor R 19 , a twentieth resistor R 20 , a twenty-first resistor R 21  and a fourth comparator IC 4 . The eighteenth resistor R 18 , the nineteenth resistor R 19 , the twentieth resistor R 20  and the fourth comparator IC 4  form a hysteresis comparator, and its principle is the same as that of the judging circuit in  FIG. 3 . In the embodiment, a first signal and a second signal, being signals output from the first judging circuit, are a low level signal and a high level signal respectively. 
         [0233]    An end of the eighteenth resistor R 18 , as an input end of the control device  500 , is connected to the positive electrode of the auxiliary source capacitor C 1 , and an end of the nineteenth resistor R 19  is connected to the ground. 
         [0234]    The other end of the eighteenth resistor R 18  and the other end of the nineteenth resistor R 19  are connected to the non-inverted input end of the fourth comparator IC 4 ; the inverted input end of the fourth comparator IC 4  is connected to a reference voltage Vref, and the twentieth resistor R 20  is connected between the non-inverted input end and the output end of the fourth comparator IC 4 ; and the output end of the fourth comparator IC 4  is connected to an end of the twenty-first resistor R 21 . 
         [0235]    The second judging circuit includes a first integrated operational amplifier U 1 , a twenty-third resistor R 23 , a tenth transistor Qs 10  and a second auxiliary power supply Vs. In the embodiment, a third signal and a fourth signal, being signals output from the second judging circuit, are a high level signal and a low level signal. 
         [0236]    The base of the tenth transistor Qs 10  is connected to the output end of the first integrated operational amplifier U 1 ; the inverted input end and the output end of the first integrated operational amplifier U 1  are connected together, and the non-inverted input end of the first integrated operational amplifier U 1  is connected to the chopper voltage control signal Vg output from the chopper control circuit  600 , and as a first output end of the control device  500 , is connected to the control end of the chopper switch  100  (i.e., the gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9 ). 
         [0237]    The emitter of the tenth transistor Qs 10  is connected to the ground, the collector of the tenth transistor Qs 10  is connected to an end of the twenty-third resistor R 23  and the anode of the nineteenth diode Ds 19 , and the other end of the twenty-third resistor R 23  is connected to the positive electrode of the second auxiliary power supply Vs. 
         [0238]    The logic circuit includes a twenty-fifth resistor R 25 , an eighteenth diode Ds 18 , a nineteenth diode Ds 19  and a twenty-second resistor R 22 . 
         [0239]    The other end of the twenty-first resistor R 21  is connected to the anode of the eighteenth diode Ds 18 . 
         [0240]    The twenty-fifth resistor R 25  is connected between the control end of the chopper switch  100  and the positive electrode of the second auxiliary power supply Vs; and the cathode of the nineteenth diode Ds 19  and the cathode of the eighteenth diode Ds 18  are connected together, and as a second output end of the control device  500 , is connected to the control end of the disconnecting switch  300  (i.e., the control end of the sixth switch transistor Q 6  and the control end of the seventh switch transistor Q 7 ). 
         [0241]    The twenty-second resistor R 22  is connected between the control end of the disconnecting switch  300  and the ground. 
         [0242]    The control end of the chopper switch  10  (i.e., the gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9 ) is connected to the chopper voltage control signal Vg output from the chopper control circuit  600 . 
         [0243]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0244]    In  FIG. 14 , the chopper voltage control signal Vg may be output by the chopper control circuit  600 , and the chopper control circuit  600  is configured to control the two-wire dimmer to output a chopper voltage. 
         [0245]    It should be noted that in the embodiment of the present invention, the gate electrode driving current of the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  of the chopper switch  100  is provided by the second auxiliary power supply Vs via the twenty-fifth resistor R 25 , and the chopper voltage control signal Vg output from the chopper control circuit  600  is a voltage which only used for turning off the chopper switch  100 . 
         [0246]    The second judging circuit detects the chopper voltage control signal, and in a case that the chopper voltage control signal Vg is turning off the chopper switch, that is, Vg is at a low level, the gate electrodes of the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  of the chopper switch  100  are controlled to be at low level via the logic circuit, and the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  are turned off. A high level signal (i.e., the third signal) is output to the logic circuit by inverting of the tenth transistor Qs 10 , and the nineteenth diode Ds 19  in the logic circuit is turned on, which controls the control end of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  to be at high level, the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned on. The voltage across the disconnecting switch  300  turned on is low, which cause the seventeenth diode D 17  and the eighteenth diode D 18  to be turned off, the auxiliary source capacitor C 1  is not charged, and the dimmer outputs a zero voltage. 
         [0247]    The second judging circuit detects the chopper voltage control signal Vg, and in a case that the chopper voltage control signal Vg is not turning off the chopper switch, that is, Vg is at a high level, the gate electrodes of the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  of the chopper switch  100  are at a high level of the second auxiliary power supply Vs via the twenty-fifth resistor R 25  in the logic circuit, and the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  are turned on. A low level signal (i.e., the fourth signal) is output to the logic circuit by inverting of the tenth transistor Qs 10 , such that the nineteenth diode Ds 19  in the logic circuit is turned off, that is, the second judging circuit does not control the disconnecting switch  300 . 
         [0248]    Based on the above, the first judging circuit detects the auxiliary source voltage Vcc. In a case that the auxiliary source voltage Vcc is lower than a set lower limit value, the fourth comparator IC 4  outputs a low level signal (i.e., the first signal) to the logic circuit, the eighteenth diode Ds 18  of the logic circuit is turned off, that is, the first judging circuit does not control the disconnecting switch  300 ; since both the first judging circuit and the second judging circuit do not control the disconnecting switch  300 , the control ends of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  are at low level via the twenty-second resistor R 22  in the logic circuit, the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned off, and their voltage drops charge the auxiliary source capacitor C 1  via the seventeenth diode D 17  or the eighteenth diode D 18 ; the output voltage V 0  of the two-wire dimmer is the difference between the input alternating current voltage Vin and the auxiliary source voltage Vcc, and the two-wire dimmer outputs a non-zero voltage; and 
         [0249]    in a case that the auxiliary source voltage Vcc is higher than a set upper limit value, the fourth comparator IC 4  outputs a high level signal (i.e., the second signal) to the logic circuit, the eighteenth diode Ds 18  of the logic circuit is turned on, the first judging circuit controls the control ends of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  to be at high level, and the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned on; the voltage drops across the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are low, the seventeenth diode D 17  or the eighteenth diode D 18  is turned off, and the auxiliary source capacitor C 1  is not charged; the output voltage of the two-wire dimmer is the input alternating current voltage Vin, which is a non-zero voltage. 
         [0250]    The embodiment described above only provides an implementation of the auxiliary power supply circuit of the two-wire dimmer according to the third embodiment of the present invention. In practical application, the auxiliary power supply circuit of the two-wire dimmer according to the third embodiment of the present invention may be but not limited to the implementation described above. 
         [0251]      FIG. 15  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a fourth embodiment of the present invention. The circuit of the fourth embodiment shown in  FIG. 15  differs from the circuit of the third embodiment shown in  FIG. 14  in that: the control device  500  detects the auxiliary source voltage and receives the chopper voltage control signal Vg and the chopper period control signal Vb, judges whether the chopper switch  100  is in a chopper period according to the chopper period control signal Vb, outputs a signal to control the disconnecting switch  300  and the chopper switch  100  to be on or off according to a comparison result of the auxiliary source voltage with a preset voltage, a state of the chopper voltage control signal Vg and whether the chopper switch  100  being in a chopper period, to control the charging of the auxiliary source capacitor  200  via the rectifier device  400 . 
         [0252]    As shown in  FIG. 15 , the chopper period control signal Vb may be output by a chopper control circuit (not shown in the figures). The chopper period control signal Vb has two states, the chopper period control signal Vb is in a first state in a case that the chopper switch  100  is in a chopper period; and the chopper period control signal Vb is in a second state in a case that the chopper switch  100  is in a non-chopper period. The control device  500  may judge whether the chopper switch  100  is in a chopper period or a non-chopper period according to the state of the chopper period control signal Vb. The control device  500  controls the auxiliary source capacitor to be charged in a non-chopper period according to the chopper period control signal Vb in a case that the auxiliary source voltage is lower than a set lower limit value. 
         [0253]    An implementation of the auxiliary power supply circuit is provided according to the fourth embodiment of the present invention. In the auxiliary power supply circuit of the two-wire dimmer according to the fourth embodiment of the present invention, the control device may include a first judging circuit, a second judging circuit and a logic circuit. 
         [0254]    The first judging circuit is configured to detect the auxiliary source voltage, compare the auxiliary source voltage with a preset voltage, output a first signal to the logic circuit in a case that the auxiliary source voltage is lower than a set lower limit value, and output a second signal to the logic circuit in a case that the auxiliary source voltage is higher than a set upper limit value. 
         [0255]    The second judging circuit is configured to detect the chopper period control signal, judge whether the chopper switch is in a chopper period according to the chopper period control signal, output a third signal to the logic circuit in a case that the chopper switch is in a chopper period, and output a fourth signal to the logic circuit in a case that the chopper switch is in a non-chopper period. 
         [0256]    The logic circuit is configured to receive an output signal of the first judging circuit, an output signal of the second judging circuit and a chopper voltage control signal, control the disconnecting switch to be on in a case that the first judging circuit outputs the second signal or the second judging circuit outputs the third signal; control the disconnecting switch to be off in a case that the first judging circuit outputs the first signal and the second judging circuit outputs the fourth signal; control the chopper switch to be off in a case that the chopper switch control signal is turning off the chopper switch; and control the chopper switch to be on in a case that the chopper switch control signal is not turning off the chopper switch. 
         [0257]    An implementation of the control device of the auxiliary power supply circuit of the fourth embodiment of the present invention may be as the circuit shown in  FIG. 16 .  FIG. 16  is a circuit diagram of an implementation of the control device of the auxiliary power supply circuit according to the fourth embodiment of the present invention. As shown in  FIG. 16 , the chopper switch  100  consists of two MOS transistors. 
         [0258]    As shown in  FIG. 16 , the auxiliary source capacitor  200  is C 1 , the disconnecting switch  300  includes a sixth switch transistor Q 6  and a seventh switch transistor Q 7 , and the rectifier device includes a seventeenth diode D 17  and an eighteenth diode D 18 . 
         [0259]    In the parallel branch consisting of the auxiliary source capacitor, the rectifier device and the disconnecting switch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the seventeenth diode D 17  and the cathode of the eighteenth diode D 18 ; the two ends of the sixth switch transistor Q 6  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the seventeenth diode D 17 ; and the two ends of the seventh switch transistor Q 7  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the eighteenth diode D 18 . 
         [0260]    The chopper switch  100  includes an eighth MOS transistor Q 8  and a ninth MOS transistor Q 9 . The source electrode of the eighth MOS transistor Q 8  is connected to a common end of the sixth switch transistor Q 6  and the anode of the seventeenth diode D 17 , and the drain electrode of the eighth MOS transistor Q 8  is connected to an end of the input voltage Vin. The source electrode of the ninth MOS transistor Q 9  is connected to a common end of the seventh switch transistor Q 7  and the anode of the eighteenth diode D 18 , and the drain electrode of the ninth MOS transistor Q 9  is connected to an end of the output load. The other end of the alternating current input voltage Vin is connected to the other end of the output load. The gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9  are connected together, and as the control end of the chopper switch  100 , is connected to the output end of the control device  500 . The control end of the sixth switch transistor Q 6  and the control end of the seventh switch transistor Q 7  are connected together and are used as the control end of the disconnecting switch  300 . 
         [0261]    The control device shown in  FIG. 16  differs from that in  FIG. 14  in that: the other end of the twenty-fourth resistor R 24  of the control device  500  is connected to the chopper period control signal Vb output from the chopper control circuit  700 , and the control end of the chopper switch  100  (i.e., the gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9 ) is connected to the chopper voltage control signal Vg output from the chopper control circuit  700 . 
         [0262]    The control device  500  includes a first judging circuit, a second judging circuit and a logic circuit. 
         [0263]    The first judging circuit includes an eighteenth resistor R 18 , a nineteenth resistor R 19 , a twentieth resistor R 20 , a twenty-first resistor R 21  and a fourth comparator IC 4 . The eighteenth resistor R 18 , the nineteenth resistor R 19 , the twentieth resistor R 20  and the fourth comparator IC 4  form a hysteresis comparator, as the judging circuit in  FIG. 3 . In the embodiment, a first signal and a second signal, being signals output from the first judging circuit, are a low level signal and a high level signal respectively. 
         [0264]    An end of the eighteenth resistor R 18 , as an input end of the control device  500 , is connected to the positive electrode of the auxiliary source capacitor C 1 , and an end of the nineteenth resistor R 19  is connected to the ground. 
         [0265]    The other end of the eighteenth resistor R 18  and the other end of the nineteenth resistor R 19  are connected to the non-inverted input end of the fourth comparator IC 4 , the inverted input end of the fourth comparator IC 4  is connected to a reference voltage Vref, and the twentieth resistor R 20  is connected between the non-inverted input end and the output end of the fourth comparator IC 4 . 
         [0266]    The output end of the fourth comparator IC 4  is connected to an end of the twenty-first resistor R 21 , and the other end of the twenty-first resistor R 21  is connected to the anode of the eighteenth diode Ds 18 . 
         [0267]    The second judging circuit includes a twenty-third resistor R 23 , a twenty-fourth resistor R 24 , a tenth transistor Qs 10  and a second auxiliary power supply Vs. In the embodiment, a third signal and a fourth signal, being signals output from the second judging circuit, are a high level signal and a low level signal respectively. 
         [0268]    The base of the tenth transistor Qs 10  is connected to an end of the twenty-fourth resistor R 24 , and the other end of the twenty-fourth resistor R 24  is connected to the chopper period control signal Vb output from the chopper control circuit  700 . 
         [0269]    The emitter of the tenth transistor Qs 10  is connected to the ground, the collector of the tenth transistor Qs 10  is connected to an end of the twenty-third resistor R 23  and the anode of the nineteenth diode Ds 19 , and the other end of the twenty-third resistor R 23  is connected to the positive electrode of the second auxiliary power supply Vs. 
         [0270]    The logic circuit includes a twenty-fifth resistor R 25 , an eighteenth diode Ds 18 , a nineteenth diode Ds 19  and a twenty-second resistor R 22 . 
         [0271]    An end of the twenty-fifth resistor R 25  is connected to the positive electrode of the second auxiliary power supply Vs, the other end of the twenty-fifth resistor R 25  is connected to the chopper voltage control signal Vg output from the chopper control circuit  700 , and as a first output end of the control device  500 , is connected to the control end of the chopper switch  100  (i.e., the gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9 ). 
         [0272]    The cathode of the nineteenth diode Ds 19  and the cathode of the eighteenth diode Ds 18  are connected together, and as a second output end of the control device  500 , is connected to the control end of the disconnecting switch  300  (i.e., the control end of the sixth switch transistor Q 6  and the control end of the seventh switch transistor Q 7 ). 
         [0273]    The twenty-second resistor R 22  is connected between the second output end of the control device  500  and the ground. 
         [0274]    In  FIG. 16 , the chopper period control signal Vb may be output by the chopper control circuit  700 , and has two states: a high level state and a low level state. 
         [0275]    The second judging circuit detects the chopper period control signal Vb, and in a case that the chopper switch  100  is in a chopper period, the chopper period control signal Vb is at a low level, a high level signal (i.e., the third signal) is output to the logic circuit by inverting of the tenth transistor Qs 10 , the nineteenth diode Ds 19  in the logic circuit is turned on, and the second judging circuit controls the control ends of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  to be at high level, and the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned on. The turn-on voltage drops of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are low, the seventeenth diode D 17  and the eighteenth diode D 18  are turned off, and the auxiliary source capacitor C 1  is not charged. The chopper switch  100  is controlled to be off directly in a case that the chopper voltage control signal Vg is turning off the chopper switch  100 , and the chopper switch  100  is controlled to be on via the resistor R 25  and the second auxiliary power supply Vs in the logic circuit in a case that the chopper voltage control signal Vg is not turning off the chopper switch. 
         [0276]    The second judging circuit detects the chopper period control signal Vb, and in a case that the chopper switch  100  is in a non-chopper period, the two-wire dimmer does not output the zero voltage, that is, the chopper voltage control signal Vg is not at a low level, and the chopper switch  100  is on. The chopper period control signal Vb is at a high level, and a low level signal (i.e., the fourth signal) is output to the logic circuit by inverting of the tenth transistor Qs 10 , therefore, the nineteenth diode Ds 19  is turned off, that is, the second judging circuit does not control the disconnecting switch  300  to be on or off. 
         [0277]    The first judging circuit detects the auxiliary source voltage Vcc, and in a case that the auxiliary source voltage Vcc is higher than an upper limit value, the fourth comparator IC 4  outputs a high level signal (i.e., the second signal) to the logic circuit, the eighteenth diode Ds 18  in the logic circuit is turned on, the first judging circuit controls the control ends of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  to be at a high level, and the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned on. The turn-on voltage drops of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are low, the seventeenth diode D 17  and the eighteenth diode D 18  are turned off, and the auxiliary source capacitor C 1  is not charged. 
         [0278]    The first judging circuit detects the auxiliary source voltage Vcc, and in a case that the auxiliary source voltage Vcc is lower than a lower limit value, the fourth comparator IC 4  outputs a low level signal (i.e., the first signal) to the logic circuit, the eighteenth diode Ds 18  in the logic circuit is turned off, that is, the first judging circuit does not control the disconnecting switch  300  to be on or off. Since both the first judging circuit and the second judging circuit do not control the disconnecting switch  300  to be on or off, the control ends of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  of the disconnecting switch  300  are at low level via the twenty-second resistor R 22  in the logic circuit, and the sixth switch transistor Q 6  and the seventh switch transistor Q 7  are turned off. The voltage drops of the sixth switch transistor Q 6  and the seventh switch transistor Q 7  make the seventeenth diode D 17  and the eighteenth diode D 18  be turned on, and the auxiliary source capacitor C 1  is charged. 
         [0279]    In the implementations of the auxiliary power supply circuit of the two-wire dimmer provided by the third embodiment and the fourth embodiment described above, the chopper switch  100  consists of two MOS transistors. In practical application, the chopper switch  100  may be implemented in many ways. Several implementations of the chopper switch will be described in detail below. 
         [0280]      FIG. 17  is a circuit diagram of a fifth implementation of the chopper switch according to an embodiment of the present invention. As shown in  FIG. 17 , the chopper switch  100  consists of a rectifier bridge and a unidirectional switch. 
         [0281]    As shown in  FIG. 17 , the auxiliary source capacitor  200  is C 1 , the disconnecting switch  300  is Q 2 , and the rectifier device is D 21 . The auxiliary source capacitor C 1  and the rectifier device D 21  are connected in series to form a series branch, the series branch and the disconnecting switch Q 2  are connected in parallel to form a parallel branch; and the chopper switch  100  is connected in series with the parallel branch. 
         [0282]    In the parallel branch, the negative electrode of the auxiliary source capacitor C 1  is connected to a common reference end (the ground), the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the rectifier device D 21 , and the two ends of the disconnecting switch Q 2  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the rectifier device D 21 . 
         [0283]    The chopper switch  100  is a bidirectional switch consisting of a switch transistor Q 11  and a rectifier bridge. The rectifier bridge consists of a twenty-second diode D 22 , a twenty-third diode D 23 , a twenty-fourth diode D 24  and a twenty-fifth diode D 25 . 
         [0284]    The twenty-second diode D 22  is connected in series with the twenty-third diode D 23 , and the cathode of the twenty-second diode D 22  is connected to the anode of the twenty-third diode D 23 . 
         [0285]    The twenty-fourth diode D 24  is connected in series with the twenty-fifth diode D 25 , and the cathode of the twenty-fourth diode D 24  is connected to the anode of the twenty-fifth diode D 25 . 
         [0286]    The anode of the twenty-second diode D 22  and the anode of the twenty-fourth diode D 24  are connected to the source electrode of the switch transistor Q 11 , and the cathode of the twenty-third diode D 23  and the cathode of the twenty-fifth diode D 25  are connected to a common end of the anode of the rectifier device D 21  and the disconnecting switch Q 2 . 
         [0287]    The drain electrode of the switch transistor Q 11  is connected to a common end of the disconnecting switch Q 2  and the negative electrode of the auxiliary source capacitor C 1 . 
         [0288]    A common end of the twenty-second diode D 22  and the twenty-third diode D 23 , as an end of the two-wire dimmer, is connected to the input voltage Vin, and a common end of the twenty-fourth diode D 24  and the twenty-fifth diode D 25 , as the other end of the two-wire dimmer, is connected to the output load, and the output voltage of the two-wire dimmer is Vo. 
         [0289]    The two-wire dimmer and the load are connected in series, and then connected in parallel with the input Vin. 
         [0290]    The gate electrode of the switch transistor Q 11  is connected to a first signal V 1 , and the control end of the disconnecting switch Q 2  is connected to a second signal V 2 . 
         [0291]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0292]    It should be noted that the switch transistor Q 11  which forms the chopper switch  100  shown in  FIG. 17  is described by taking a MOS transistor as an example. In practical application, any unidirectional switch transistor may be used as the switch transistor Q 1  shown in the figures to form the chopper switch of the embodiment of the present invention. 
         [0293]    In the circuit shown in  FIG. 17 , in a case that the switch transistor Q 11  is controlled to be on and the disconnecting switch Q 2  is controlled to be off, the two-wire dimmer obtains the auxiliary source voltage, and the output voltage V 0  is a difference between the input voltage Vin and the auxiliary source voltage Vcc. In a case that the switch transistor Q 11  is controlled to be on and the disconnecting switch Q 2  is controlled to be on, the auxiliary source capacitor C 1  is discharged, and the output voltage is equal to the input voltage Vin. In a case that the switch transistor Q 11  is controlled to be off and the disconnecting switch Q 2  is controlled to be on, the auxiliary source capacitor C 1  is discharged to an auxiliary source load (not shown in the figures), and the output voltage is zero. 
         [0294]    In the auxiliary power supply circuit shown in  FIG. 17 , in a case that the two-wire dimmer outputs a zero voltage and a non-zero voltage alternately in a half period of the alternating current voltage Vin, the output voltage of the two-wire dimmer is a chopper voltage. Specifically, in a case that the chopper voltage control signal Vg of the circuit shown in  FIG. 17  is a control signal of a trailing edge dimmer, the waveform of the output voltage V 0  may be as shown in  FIG. 18 . 
         [0295]      FIG. 19  is a circuit diagram of a sixth implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 19 , the chopper switch  100  consists of a unidirectional switch. 
         [0296]    As shown in  FIG. 19 , the auxiliary source capacitor  200  is C 1 , the disconnecting switch  300  is Q 2 , and the rectifier device is D 21 . The auxiliary source capacitor C 1  and the rectifier device D 21  are connected in series to form a series branch, the series branch and the disconnecting switch Q 2  are connected in parallel to form a parallel branch; and the chopper switch  100  is connected in series with the parallel branch. 
         [0297]    In the parallel branch, the negative electrode of the auxiliary source capacitor C 1  is connected to an end of the output load, the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the rectifier device D 21 , and the two ends of the disconnecting switch Q 2  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the rectifier device D 21 . 
         [0298]    The chopper switch  100  includes a switch transistor Q 11 . The source electrode of the switch transistor Q 11  is connected to a common end of the disconnecting switch Q 2  and the anode of the rectifier device D 21 , and the drain electrode of the switch transistor Q 11  is connected to an end of the input voltage Vin. 
         [0299]    The other end of the input voltage Vin is connected to the other end of the output load. 
         [0300]    The gate electrode of the switch transistor Q 11  is connected to the first signal V 1 ; and the control end of the disconnecting switch Q 2  is connected to the second signal V 2 . 
         [0301]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0302]    The operating principle of the circuit shown in  FIG. 19  is similar to that in  FIG. 17 , and the detailed description thereof is omitted. The circuit shown in  FIG. 19  differs from the circuit shown in  FIG. 17  in that: the chopper voltage is output in a half period and the body diode of the switch transistor Q 5  is turned on in the other half period in a case that the two-wire dimmer outputs a chopper voltage. That is, the chopper voltage is output in a half period and the alternating current input voltage is output in the other half period in one alternating current period of the chopper voltage output from the two-wire dimmer. Specifically, the waveform of the output voltage of the circuit shown in  FIG. 19  is shown in  FIG. 20 . 
         [0303]    It should be noted that the switch transistor Q 11  which forms the chopper switch  100  shown in  FIG. 19  is described by taking the MOS transistor as an example. In practical application, the switch transistor Q 11  shown in  FIG. 19  may be replaced by inversely connecting a unidirectional switch transistor with a diode in parallel, to form the chopper switch in the embodiment of the present invention. For example, the chopper switch  100  may be a circuit shown in  FIG. 21 . 
         [0304]      FIG. 21  is a circuit diagram of a seventh implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 21 , the chopper switch  100  consists of a unidirectional switch. The circuit shown in  FIG. 21  differs from the circuit shown in  FIG. 19  in that, a switch transistor Q 11  is inversely connected in parallel with a diode D 26  to replace Q 11  in  FIG. 19 . 
         [0305]    As shown in  FIG. 21 , the structure of the parallel branch is the same as that in  FIG. 19 , and the detailed description thereof is omitted. 
         [0306]    The chopper switch  100  includes a switch transistor Q 11  and a twenty-sixth diode D 26 . The emitter of the switch transistor Q 11  is connected to a common end of the disconnecting switch Q 2  and the anode of the rectifier device D 21 , and the collector of the switch transistor Q 11  is connected to the input voltage Vin. 
         [0307]    The cathode of the twenty-sixth diode D 26  is connected to the collector of the switch transistor Q 11 , and the anode of the twenty-sixth diode D 26  is connected to the emitter of the switch transistor Q 11 . 
         [0308]    The gate electrode of the switch transistor Q 11  is connected to a first signal V 1 , and the control end of the disconnecting switch Q 2  is connected to a second signal V 2 . 
         [0309]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0310]    The operating principle of the circuit shown in  FIG. 21  is similar to that in  FIG. 19 , and the detailed description is omitted herein. 
         [0311]      FIG. 22  is a circuit diagram of an eighth implementation of the chopper switch according to an embodiment of the present invention. In the circuit shown in  FIG. 22 , the chopper switch  100  consists of two MOS transistors. 
         [0312]    As shown in  FIG. 22 , the auxiliary source capacitor  200  is C 1 , the disconnecting switch  300  includes a sixth switch transistor Q 6  and a seventh switch transistor Q 7 , and the rectifier device includes a seventeenth diode D 17  and an eighteenth diode D 18 . 
         [0313]    In the parallel branch consisting of the auxiliary source capacitor, the rectifier device and the disconnecting switch, the negative electrode of the auxiliary source capacitor C 1  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the seventeenth diode D 17  and the cathode of the eighteenth diode D 18 , the two ends of the sixth switch transistor Q 6  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the seventeenth diode D 17 , and the two ends of the seventh switch transistor Q 7  are respectively connected to the negative electrode of the auxiliary source capacitor C 1  and the anode of the eighteenth diode D 18 . 
         [0314]    The chopper switch  100  includes an eighth MOS transistor Q 8  and a ninth MOS transistor Q 9 . 
         [0315]    The source electrode of the eighth MOS transistor Q 8  is connected to a common end of the sixth switch transistor Q 6  and the anode of the seventeenth diode D 17 , and the drain electrode of the eighth MOS transistor Q 8  is connected to an end of the input voltage Vin. 
         [0316]    The source electrode of the ninth MOS transistor Q 9  is connected to a common end of the seventh switch transistor Q 7  and the anode of the eighteenth diode D 18 , and the drain electrode of the ninth MOS transistor Q 9  is connected to an end of the output load. 
         [0317]    The other end of the input voltage Vin is connected to the other end of the output load. 
         [0318]    The gate electrode of the eighth MOS transistor Q 8  and the gate electrode of the ninth MOS transistor Q 9  are connected to a first control signal V 1 ; and the control end of the sixth switch transistor Q 6  and the control end of the seventh switch transistor Q 7  are connected to a second control signal V 2 . 
         [0319]    The voltage across the auxiliary source capacitor C 1  is the auxiliary source voltage Vcc. 
         [0320]    In the circuit shown in  FIG. 22 , the auxiliary source voltage Vcc is detected. The sixth switch transistor Q 6  and the seventh switch transistor Q 7  is controlled to be turned off in a case that the auxiliary source voltage Vcc is lower than a set lower limit value and the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  are turned on. In this case, in the two-wire dimmer, the auxiliary source capacitor C 1  is connected in parallel with the sixth switch transistor Q 6  (or the seventh switch transistor Q 7 ) via the seventeenth diode D 17  (or the eighteenth diode D 18 ), and is connected in series with the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9 , and forms a loop together with the output load of the two-wire dimmer. The alternating current power supply charges the auxiliary source capacitor C 1  through the loop, the auxiliary source voltage Vcc increases, and the output voltage of the two-wire dimmer is the difference between the input voltage Vin and the auxiliary source voltage Vcc. 
         [0321]    The sixth switch transistor Q 6  and the seventh switch transistor Q 7  are controlled to be turned on in a case that the auxiliary source voltage Vcc is lower than a set lower limit value and the eighth MOS transistor Q 8  and the ninth MOS transistor Q 9  are turned off. In this case, the turn-on of the sixth switch transistor Q 6  (or the seventh switch transistor Q 7 ) is causes the series branch of the auxiliary source capacitor C 1  and the seventeenth diode D 17  (or the eighteenth diode D 18 ) is short-circuited, the auxiliary source capacitor C 1  provides power to an auxiliary source load (not shown in the figures), and the output voltage of the two-wire dimmer is zero. 
         [0322]    All the implementations of the control device described in the third embodiment and the fourth embodiment of the present invention may be applied to the circuits of the four chopper switches provided in  FIG. 17  to  FIG. 22 . 
         [0323]    In the embodiments shown in  FIG. 13  to  FIG. 22 , the disconnecting switch Q 2  may be a MOS transistor or a unidirectional switch transistor which is inversely connected with a diode in parallel. Moreover, in the embodiments shown in  FIG. 17  to  FIG. 22 , the first control signal V 1  and the second control signal V 2  are connected to the output ends of the control device  40  according to specific implementations. 
         [0324]    The second auxiliary power supply Vs and the auxiliary source voltage Vcc in  FIG. 2  to  FIG. 23  have a common ground. Moreover, the second auxiliary power supply Vs may be replaced by the auxiliary source voltage Vcc, or may be obtained by converting the auxiliary source voltage Vcc, or does not related to the auxiliary source voltage Vcc. 
         [0325]      FIG. 23  is a structural diagram of an auxiliary power supply circuit of a two-wire dimmer according to a fifth embodiment of the present invention. The auxiliary power supply circuit includes a first power supply branch  1000  and a second power supply branch  2000 . 
         [0326]    The first power supply branch  1000  includes a first auxiliary source capacitor and a first disconnecting switch connected in series to form a first series branch; and a first chopper switch connected in parallel with the first series branch. 
         [0327]    The second power supply branch  2000  includes a rectifier device and a second auxiliary source capacitor connected in series to form a second series branch; a second disconnecting switch connected in parallel with the second series branch to form a parallel branch; and a second chopper switch connected in series with the parallel branch. 
         [0328]    The auxiliary power supply circuit further includes a first control device  3000  for controlling the first power supply branch, and a second control device  4000  for controlling the second power supply branch. 
         [0329]    The first control device  3000  is configured to detect the auxiliary source voltage of the first power supply branch  1000  and receive a first chopper voltage control signal or a first chopper period control signal, output a signal to control the first chopper switch and the first disconnecting switch to be on or off according to a comparison result of the auxiliary source voltage of the first power supply branch  1000  with a preset voltage and a state of the first chopper voltage control signal or a state of the first chopper period control signal, to control the charging of the first auxiliary source capacitor. 
         [0330]    The second control device  4000  is configured to detect the auxiliary source voltage of the second power supply branch  2000  and receive a chopper voltage control signal or a second chopper period control signal, output a signal to control the second disconnecting switch and the second chopper switch to be on or off according to a comparison result of the auxiliary source voltage of the second power supply branch  2000  with a preset voltage and a state of the chopper voltage control signal or a state of the second chopper period control signal, to charge the second auxiliary source capacitor via the rectifier device. 
         [0331]    It should be noted that the first control device described in the fifth embodiment of the present invention is the same as the control device of the auxiliary power supply circuit described in the first embodiment of the present invention, and their specific implementations and operating principles are the same, which will not be described in detail herein. In other embodiments of the present invention, the first control device may be the control device of the auxiliary power supply circuit described in the second embodiment. 
         [0332]    The second control device described in the fifth embodiment of the present invention is the same as the control device of the auxiliary power supply circuit described in the third embodiment of the present invention, and their specific implementations and operating principles are the same, which will not be described in detail herein. In other embodiments of the present invention, the second control device may be the control device of the auxiliary power supply circuit described in the fourth embodiment. 
         [0333]    An implementation of the auxiliary power supply circuit is provided according to the fifth embodiment of the present invention, as shown in  FIG. 24 .  FIG. 24  is a circuit diagram of an implementation of the auxiliary power supply circuit according to the fifth embodiment of the present invention. 
         [0334]    As shown in  FIG. 24 , in the first power supply branch  1000 , the first auxiliary source capacitor is C 100 , the first disconnecting switch is Q 300 , and the first chopper switch is MOS transistor Q 100 ; the auxiliary source capacitor C 100 , the disconnecting switch Q 300  and a diode D 100  are connected in series to form a series branch; and the series branch is connected in parallel with the first chopper switch Q 100 . 
         [0335]    In the series branch, the negative electrode of the first auxiliary source capacitor C 100  is connected to the ground, and the positive electrode of the first auxiliary source capacitor C 100  is connected to an end of the first disconnecting switch Q 300 ; and the other end of the disconnecting switch Q 300  is connected to the cathode of the diode D 100 , and the anode of the diode D 100  is connected to an end of the output load. 
         [0336]    The source electrode of the first chopper switch Q 100  is connected to an end of the output load, and the drain electrode of the first chopper switch Q 100  is connected to an end of the series branch which is connected to the ground. 
         [0337]    In the second power supply branch  2000 , the second auxiliary source capacitor is C 200 , the second disconnecting switch is Q 400 , the rectifier device is D 200 , and the second chopper switch is MOS transistor Q 200 ; the second auxiliary source capacitor C 200  and the rectifier device D 200  are connected in series to form a series branch, then the series branch and the second disconnecting switch Q 400  are connected in parallel to form a parallel branch; and the second chopper switch Q 200  is connected in series with the parallel branch. 
         [0338]    In the parallel branch, the negative electrode of the second auxiliary source capacitor C 200  is connected to the ground, the positive electrode of the auxiliary source capacitor C 1  is connected to the cathode of the rectifier device D 200 ; and the two ends of the second disconnecting switch Q 400  are respectively connected to the negative electrode of the second auxiliary source capacitor C 1  and the anode of the rectifier device D 200 . 
         [0339]    The source electrode of the second chopper switch Q 200  is connected to a common end of the second disconnecting switch Q 400  and the anode of the rectifier device D 200 , and the drain electrode of the second chopper switch Q 200  is connected to an end of an input voltage Vin. 
         [0340]    It can be seen from the embodiment that the first auxiliary source capacitor C 100  and the second auxiliary source capacitor C 200  may be incorporated as one capacitor. 
         [0341]    In the circuit shown in  FIG. 24 , in the first power supply branch  1000 , the first chopper switch Q 100  and the first disconnecting switch Q 300  are controlled to charge the first auxiliary source capacitor C 100  via the diode D 100 ; and in the second power supply branch  2000 , the second chopper switch Q 200  and the second disconnecting switch Q 400  are controlled to charge the second auxiliary source capacitor C 200  via the rectifier device D 200 . 
         [0342]    In the circuit shown in  FIG. 24 , the operating principle of the first power supply branch  1000  is the same as the operating principle of the circuit shown in  FIG. 9 , and the operating principle of the second power supply branch  2000  is the same as the operating principle of the circuit shown in  FIG. 19 , which will not be described in detail herein. 
         [0343]    In the fifth embodiment of the present invention, the first chopper switch of the first power supply branch  1000  may adopt any of the implementations shown in  FIG. 7  to  FIG. 12 ; and the second chopper switch of the second power supply branch  2000  may adopt any of the implementations shown in  FIG. 17  to  FIG. 22 . 
         [0344]    The auxiliary power supply circuit of the two-wire dimmer provided by the present invention is described in detail above. The principle and the embodiments of the present invention are described by detailed examples which are only for understanding the method and the core idea of the present invention. For those skilled in the art, some changes may be made on specific implementations and applications according to the idea of the present invention. Therefore, the content of the disclosure should not be understood as the limit to the present invention.