Abstract:
An exemplary power supply circuit configured for supply power for a load includes: a main power supply configured for converting received voltages into required direct current voltages; a microprocessor configured for providing control signals; a stand-by control circuit configured for controlling the main power supply; an energy storage circuit configured for supplying the stand-by control circuit. When the load stops operating, the microprocessor outputs a control signal to the stand-by control circuit, the stand-by control circuit outputs a corresponding control signal to turn off the main power supply. In response to when the load starts operating, the stand-by control circuit outputs a corresponding control signal to turn on the main power supply, and the main power supply charges the energy storage circuit.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to power supply circuits, and particularly to a power supply circuit with a stand-by control circuit and an energy storage circuit. 
       GENERAL BACKGROUND 
       [0002]      FIG. 7  is a schematic view of a conventional power supply circuit. The power supply circuit  1  includes a first input terminal  2 , a second input terminal  3 , a relay  4 , a main power supply  5 , an assistant power supply  6 , a microprocessor  7 , and a switch  8 . The assistant power supply  6  includes a transformer  9  and a commutating and filter circuit (not labeled). 
         [0003]    The first input terminal  2  is connected to the main power supply  5 , and the second input terminal  3  is connected to the main power supply  5  via the relay  4 . The main power supply  5  is connected to a load (not shown). The transformer  9  includes a primary winding (not labeled) and a secondary winding (not labeled). The primary winding includes two terminals (not labeled). One of the terminals of the primary winding is connected to the first input terminal  2 , and the other terminal is connected to the second input terminal  3 . The secondary winding is connected to the microprocessor  7  via the commutating and filter circuit. The relay  4  includes an inductance coil (not labeled), and the inductance coil includes two terminals (not labeled). One of the terminals of the inductance coil is connected to the microprocessor  7 , and the other terminal is connected to ground. The microprocessor  7  is connected to ground via the switch  8 . 
         [0004]    An alternating current (AC) voltage is inputted into the assistant power supply  6  and converted into a direct current (DC) voltage by the transformer  9  and the commutating and filter circuit. The DC voltage is supplied to the microprocessor  7  to enable the microprocessor  7  to function. 
         [0005]    When a user presses the switch  8 , the switch  8  correspondingly generates a first pulse signal. The microprocessor  7  receives the first pulse signal and correspondingly outputs a first control signal to turn on the relay  4 . The AC voltage is inputted into the main power supply  5  via the first input terminal  2 , the second input terminal  3 , and the relay  4 . The main power supply  5  converts the AC voltage into required voltages to supply the load. 
         [0006]    When the user presses the switch  8  again, the switch  8  correspondingly generates a second pulse signal. The microprocessor  7  receives the second pulse signal and correspondingly outputs a second control signal to turn off the relay  4 . The main power supply  5  outputs no voltage, and the load stops operating correspondingly. That is, the power supply circuit  2  is in a stand-by state. 
         [0007]    Although the power supply circuit  2  is in the stand-by state, the AC voltage is still inputted into the assistant power supply  6 . The DC voltage outputted from the assistant power supply  6  is still supplied to the microprocessor  7 . That is, when the power supply circuit  2  is in the stand-by state, energy consumption is large. 
         [0008]    What is needed, therefore, is a power supply circuit that can overcome the above-described deficiencies. 
       SUMMARY 
       [0009]    A power supply circuit configured for supplying power for a load includes: a main power supply configured for converting a received voltage into a required direct current voltage; a microprocessor; a stand-by control circuit configured for controlling the main power supply; an energy storage circuit configured for supplying power for the stand-by control circuit. When the load stops operating, the microprocessor outputs a control signal to the stand-by control circuit, the stand-by control circuit outputs a corresponding control signal to turn off the main power supply. In response to when the load starts operating, the stand-by control circuit outputs a corresponding control signal to turn on the main power supply, and the main power supply charges the energy storage circuit. 
         [0010]    Other novel features and advantages will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic view of a power supply circuit according to a first embodiment of the present disclosure, the power supply circuit including a voltage conversion circuit, a commutating and filter circuit, a stand-by pilot circuit, an energy storage circuit, a main power supply, a stand-by control circuit, a microprocessor, and a stand-by detecting circuit. 
           [0012]      FIG. 2  is a circuit diagram of one embodiment of the main power supply of  FIG. 1 . 
           [0013]      FIG. 3  is a circuit diagram of one embodiment of the voltage conversion circuit and the energy storage circuit of  FIG. 1 . 
           [0014]      FIG. 4  is a circuit diagram of one embodiment of the stand-by pilot circuit of  FIG. 1 . 
           [0015]      FIG. 5  is a circuit diagram of one embodiment of the stand-by control circuit of  FIG. 1 . 
           [0016]      FIG. 6  is a schematic view of a power supply circuit according to a second embodiment of the present disclosure. 
           [0017]      FIG. 7  is a schematic view of a conventional power supply circuit. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    Reference will now be made to the drawings to describe certain inventive embodiments of the present disclosure in detail. 
         [0019]      FIG. 1  is a schematic view of a power supply circuit  20  according to a first embodiment of the present disclosure. In one embodiment, the power supply circuit  20  includes a first input terminal  211 , a second input terminal  212 , a voltage conversion circuit  22 , a commutating and filter circuit  23 , a stand-by pilot circuit  24 , an energy storage circuit  25 , a main power supply  26 , a stand-by control circuit  27 , a microprocessor  28 , and a stand-by detecting circuit  29 . 
         [0020]    An AC voltage is inputted into the commutating and filter circuit  23  via the first input terminal  211  and the second input terminal  212 . The commutating and filter circuit  23  converts the AC voltage into a DC voltage. The commutating and filter circuit  23  includes an output terminal  231 . The DC voltage is supplied to the main power supply  26  via the output terminal  231 . The AC voltage is also supplied to the voltage conversion circuit  22  via the first input terminal  211  and the second input terminal  212 . 
         [0021]    The main power supply  26  converts the DC voltage into required DC voltages for a device employing the power supply circuit  20 . In one embodiment, the main power supply may convert the DC voltage into, for example, 26V and 5V. In one embodiment, the main power supply  26  includes a first output terminal  260 , a second output terminal  261 , and a third output terminal  262 . The main power supply  26  supplies DC power for the microprocessor  28  via the first output terminal  260  and the second output terminal  261 , and supplies DC power for the voltage conversion circuit  22  via the first output terminal  260  and the third output terminal  262 . 
         [0022]    The voltage conversion circuit  22  includes an output terminal  221 . The voltage conversion circuit  22  supplies DC power for the stand-by pilot circuit  24  and the energy storage circuit  25  via the output terminal  221 . 
         [0023]    The stand-by pilot circuit  24  receives the DC voltage from the first output terminal  260  of the main power supply  26  and displays operation conditions of the main power supply  26 . The operation conditions of the main power supply  26  includes a stand-by condition, an operating normally condition, and so on. 
         [0024]    The energy storage circuit  25  includes an output terminal  251 . The energy storage circuit  25  supplies power for the stand-by control circuit  27  via the output terminal  251 . 
         [0025]    The stand-by detecting circuit  29  includes an input terminal  291 , a first output terminal  292 , and a second output terminal  293 . The stand-by detecting circuit  29  detects operation conditions of a load (not shown) via the input terminal  291 , and outputs correspondingly control signals to the microprocessor  28  via the first output terminal  292  and the stand-by control circuit  27  via the second output terminal  293 . The load can be a liquid crystal display panel for example. 
         [0026]    The stand-by control circuit  27  includes a first output terminal  271  and a second output terminal  272 . The stand-by control circuit  27  outputs control signals to control the main power supply  26  via the first output terminal  271 , and outputs control signals to control the microprocessor  28  via the second output terminal  272 . 
         [0027]    The microprocessor  28  includes a first output terminal  281 , a second output terminal  282 , and a third output terminal  283 . The microprocessor  28  outputs control signals to the stand-by control circuit  27  via the first output terminal  281  and the second output terminal  282 , and outputs control signals to the load via the third output terminal  283 . 
         [0028]      FIG. 2  is a circuit diagram of one embodiment of the main power supply  26  of  FIG. 1 . In one embodiment, the main power supply  26  includes a transformer  263 , a switch control circuit  264 , a transistor  265 , and a feedback circuit  266 . 
         [0029]    The transformer  263  includes a primary winding  267  and a secondary winding  268 . The primary winding  267  includes two terminals (not labeled). One of the terminals of the primary winding  267  is connected to the output terminal  231  of the commutating and filter circuit  23 , and is also connected to the switch control circuit  264  via a resistor (not labeled). Another terminal of the primary winding  267  is connected to a source electrode (not labeled) of the transistor  265 . The secondary winding  268  includes two terminals (not labeled) and a tap (not labeled). One of the terminals of the secondary winding  268  is connected to the first output terminal  260  of the main power supply  26  via a commutating and filter circuit (not labeled), and another terminal is connected to ground. The tap of the secondary winding  268  is connected to the second output terminal  261  of the main power supply  26  via another commutating and filter circuit (not labeled). 
         [0030]    The switch control circuit  264  is connected to the first output terminal  271  of the stand-by control circuit  27 . The switch control circuit  264  is also connected to a gate electrode (not labeled) of the transistor  265 . A drain electrode (not labeled) of the transistor  265  is connected to ground via a resistor (not labeled). The feedback circuit  266  is connected between the second output terminal  261  of the main power supply  26  and the switch control circuit  264 . 
         [0031]      FIG. 3  is a circuit diagram of one embodiment of the voltage conversion circuit  22  and the energy storage circuit  25  of  FIG. 1 . The energy storage circuit  25  includes an energy storage capacitor  250 . The energy storage capacitor  250  is connected between the output terminal  251  and ground. In one embodiment, the voltage conversion circuit  22  includes a large voltage conversion circuit  222 , a first small voltage conversion circuit  223 , a second small voltage conversion circuit  224 , and a third small voltage conversion circuit  225 . 
         [0032]    The large voltage conversion circuit  222  includes a diode (not labeled). An anode of the diode is connected to the first output terminal  260  of the main power supply  26 , and a cathode of the diode is connected to the output terminal  221  of the voltage conversion circuit  22 . 
         [0033]    The first small voltage conversion circuit  223  is connected between the first input terminal  211  of the power supply circuit  20  and the output terminal  221  of the voltage conversion circuit  22 . The second small voltage conversion circuit  224  is connected between the second input terminal  212  of the power supply circuit  20  and the output terminal  221  of the voltage conversion circuit  22 . The third small voltage conversion circuit  225  is connected between the third output terminal  262  of the main power supply  26  and the output terminal  221  of the voltage conversion circuit  22 . The first small voltage conversion circuit  223 , the second small voltage conversion circuit  224 , and the third small voltage conversion circuit  225  may have the same structure. 
         [0034]    Each of the small voltage conversion circuits  223 ,  224 , 225  includes a first capacitor  2231 , a second capacitor  2232 , a first diode  2233 , and a second diode  2234 . The second capacitor  2232  is connected between an anode of the first diode  2233  and ground. A cathode of the first diode  2233  is connected to the output terminal  221 . A cathode of the second diode  2234  is connected to the anode of the first diode  2233 , and an anode of the second diode  2234  is connected to ground. The first capacitor  2231  of the first small voltage conversion circuit  223  is connected between the anode of the first diode  2233  of the first small voltage conversion circuit  223  and the first input terminal  211 . The first capacitor  2231  of the second small voltage conversion circuit  224  is connected between the anode of the first diode  2233  of the second small voltage conversion circuit  224  and the second input terminal  212 . The first capacitor  2231  of the third small voltage conversion circuit  225  is connected between the anode of the first diode  2233  of the third small voltage conversion circuit  225  and the third output terminal  262  of the main power supply  26 . In another embodiment, the first capacitor  2231  of the third small voltage conversion circuit  225  can be replaced by a resistor or an inductor. 
         [0035]    When the main power supply  26  operates, the large voltage conversion circuit  222  and the small voltage conversion circuit  223 ,  224 ,  225  all supply the energy storage capacitor  250  of the energy storage circuit  25 . When the main power supply  26  is in a stand-by state, only the small voltage conversion circuit  223 ,  224 ,  225  supply the energy storage capacitor  250 . 
         [0036]      FIG. 4  is a circuit diagram of one embodiment of the stand-by pilot circuit  24  of  FIG. 1 . In one embodiment, the stand-by pilot circuit  24  includes a capacitor  241 , a first transistor  242 , a second transistor  243 , a light emitting diode  244 , a third diode  403 , a fourth diode  404 , and a zener diode  245 . The first transistor  242  is a positive-negative-positive (PNP) bipolar transistor, and the second transistor  243  is a negative-positive-negative (NPN) bipolar transistor. However, it may be understood that first transistor  242  and the second transistor  243  may be replaced by a P-channel metal oxide semiconductor (PMOS) transistor and a N-channel metal oxide semiconductor (NMOS) depending on the embodiment. 
         [0037]    An emitter (not labeled) of the first transistor  242  is connected to a cathode of the third diode  403  via a resistor (not labeled), and an anode of the third diode  403  is connected to the output terminal  221  of the voltage conversion circuit  22 . The emitter of the first transistor  242  is also connected to ground via the capacitor  241 . A collector (not labeled) of the first transistor  242  is connected to an anode of the light emitting diode  244 , and a cathode of the light emitting diode  244  is connected to ground. A base (not labeled) of the first transistor  242  is connected to a cathode of the fourth diode  404 , and an anode of the fourth diode  404  is connected to the first output terminal  260  of the main power supply  26 . The base of the first transistor  242  is also connected to the emitter of the first transistor  242  via a resistor (not labeled). A collector (not labeled) of the second transistor  243  is connected to the base of the first transistor  242  via a resistor (not labeled). An emitter (not labeled) of the second transistor  243  is connected to ground. A base (not labeled) of the second transistor  243  is connected to an anode of the zener diode  245 . A cathode of the second transistor  243  is connected to the emitter of the first transistor  242 . 
         [0038]    When the main power supply  26  operates, the voltage, for example, 26V, outputted from the first output terminal  260  is loaded on the base of the first transistor  242 . The first transistor  242  is turned off, and the light emitting diode  244  is turned off. 
         [0039]    When the main power supply  26  is in the stand-by state, the voltage outputted from the first output terminal  260  is about zero. The voltage conversion circuit  22  charges the capacitor  241  via the output terminal  221 . When voltage of the capacitor  241  reaches a certain value, the zener diode  245  is turned on. The second transistor  243  is turned on correspondingly. The base of the first transistor  242  is pulled down to a low level via the actived second transistor  243 . The first transistor  242  is turned on correspondingly. The capacitor  241  discharges via the first transistor  242  and the light emitting diode  244 , and the light emitting diode  244  emits light. 
         [0040]    When the voltage of the capacitor  241  discharges to a certain value, the zener diode  245  is turned off. The first transistor  242  and the second transistor  243  are turned off, the light emitting diode  244  stops emitting lights, correspondingly. The small voltage conversion circuit  223 ,  224 ,  225  charge the capacitor  241  again. When the voltage of the capacitor  241  reaches the certain value, the light emitting diode  244  emits light again. That is, the capacitor  241  is charged and discharged continuously when the main power supply  26  is in the stand-by state and the light emitting diode  244  flicks continuously. This indicates that the power supply circuit  20  is in the stand-by state. 
         [0041]      FIG. 5  is a circuit diagram of one embodiment of the stand-by control circuit  27  of  FIG. 1 . The stand-by control circuit  27  includes a switch  273 , a trigger  274 , a transistor  275 , an optical coupler  276 , a fifth diode  405 , a sixth diode  406 , a seventh diode  407 , an eighth diode  408 , and a reverser  277 . The switch  273  is used for manually controlling the power supply circuit  20  by the user. The switch  273  can be a touch switch, a unidirectional switch, or a bidirectional switch depending on the embodiment. The transistor  275  can be an NPN bipolar transistor or a metal-oxide-semiconductor field-effect transistor. 
         [0042]    The switch  273  includes two terminals. One of the terminals of the switch  273  is connected to the trigger  274 , and the terminal is also connected to a cathode of the fifth diode  405 . The other terminal is connected to ground. An anode of the fifth diode  405  is connected to the second output terminal  272  of the stand-by control circuit  27 . A base of the transistor  275  is connected to the trigger  274 . An emitter of the transistor  275  is connected to an anode of a light emitting diode of the optical coupler  276 . A collector of the transistor  275  is connected to the trigger  274 . The collector of the transistor  275  is also connected to a cathode of the sixth diode  406 , and an anode of the sixth diode  406  is connected to the output terminal  251  of the energy storage circuit  25 . The output terminal  271  of the stand-by control circuit  27  is connected to a collector of a phototransistor of the optical coupler  276  via the reverser  277 . A cathode of a light emitting diode of the optical coupler  276  is connected to ground, and an emitter of a phototransistor of the optical coupler  276  is connected to ground. The first output terminal  281  of the microprocessor  28  is connected to an anode of the seventh diode  407 , and a cathode of the seventh diode  407  is connected to the trigger  274 . The second output terminal  282  of the microprocessor  28  is connected to an anode of the eighth diode  408 , and a cathode of the eighth diode  408  is connected to the base of the transistor  275 . The trigger  274  is also connected to the second output terminal  293  of the stand-by detecting circuit  29 . 
         [0043]    When the power supply circuit  20  is in the stand-by state, the main power supply is shut down. Therefore, energy consumption of the power supply circuit  20  decreases compared to conventional art. 
         [0044]      FIG. 6  is a schematic view of a power supply circuit  30  according to a second embodiment of the present disclosure. The power supply circuit  30  is similar to the power supply circuit  20 . However, the power supply circuit  30  further includes a relay  313 . The second input terminal  212  is connected to the commutating and filter circuit  33  via the relay  313 . When the power supply circuit  30  is in the stand-by state, the stand-by control circuit  37  outputs a control signal to turn off the relay  313 . The power supply circuit  30  is turned off correspondingly. 
         [0045]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.