Patent Publication Number: US-2023152357-A1

Title: Control module of power calibration circuit

Description:
FIELD OF THE INVENTION 
     The invention relates to a control module of a power calibration circuit, and more particularly to a control module of a power calibration circuit capable of clamping a feedback voltage. 
     BACKGROUND OF THE INVENTION 
     The conventional control module of a power calibration circuit has a feedback control mechanism to calibrate the current control based on the voltage of the output terminal of the power calibration circuit. 
     Specifically, the voltage of the output terminal of the power calibration circuit varies with the post load. In other words, the higher the demand of the post load, the higher the electric energy provided by the power calibration circuit. However, the post load of the power calibration circuit does not always remain constant. If the voltage of the post load drops suddenly, the voltage of the output terminal of the power calibration circuit has to increase significantly to perform a feedback mechanism that causes the control module to perform appropriate control for the reduction. Accordingly, a problem of delay in response in which the power calibration circuit will continue to output at a higher voltage for a period of time occurred. For a high-voltage capacitor installed at the post load of the power calibration circuit, the high-voltage capacitor needs to withstand a higher voltage during that period of time, and excessive voltage will put the high-voltage capacitor in a dangerous environment. 
     In order to solve this problem, some manufacturers use capacitors that withstand higher voltage, but the problem that follows is the increase in cost. 
     SUMMARY OF THE INVENTION 
     A main object of the invention is to solve the problem of feedback response of the conventional power calibration circuit being too slow, resulting in ineffective protection of the post-stage coordinative circuits. 
     In order to achieve the above object, the invention provides a control module of a power calibration circuit comprising a control unit, a main voltage feedback unit and an auxiliary voltage feedback unit. The control unit is connected to at least one power switch of the power calibration circuit, the main voltage feedback unit is connected to an output terminal of the power calibration circuit and the control unit, and the auxiliary voltage feedback unit is connected to the output terminal of the power calibration circuit and the control unit. The auxiliary voltage feedback unit comprises a voltage dividing circuit which is connected to the output terminal and includes at least one voltage dividing node, and a voltage limiting circuit which is connected to the at least one voltage dividing node and the control unit. If a voltage of the at least one voltage dividing node is not higher than a reference voltage, the voltage limiting circuit is in a first state without interfering a feedback voltage provided from the main voltage feedback unit to the control unit, and if the voltage of the at least one voltage dividing node is higher than the reference voltage, the voltage limiting circuit is in a second state that interferes the feedback voltage provided from the main voltage feedback unit to the control unit with an interference voltage. 
     In one embodiment, the voltage limiting circuit comprises a comparator and a diode connected to the comparator. The comparator comprises a non-inverting input terminal connected to the at least one voltage dividing node, an inverting input terminal receiving the reference voltage, and an output terminal. The diode comprises a positive electrode connected to the output terminal of the comparator, and a negative electrode connected to the control unit. 
     In one embodiment, the voltage limiting circuit comprises a first resistor and a first capacitor connected in series with the first resistor. A first series node formed between the first resistor and the first capacitor is connected to the output terminal of the comparator, and one end of the first resistor not connected in series with the first capacitor is connected to an operating voltage source. 
     In one embodiment, the voltage limiting circuit comprises a second resistor connected to the negative electrode of the diode. 
     In one embodiment, the voltage limiting circuit comprises a reference voltage generating circuit to generate the reference voltage. The reference voltage generating circuit comprises a third resistor connected to an operating voltage source, a three-terminal adjustable shunt reference source connected in series with the third resistor to form a second series node therebetween, a voltage dividing bypass connected in parallel with the three-terminal adjustable shunt reference source, and a second capacitor connected in parallel with the three-terminal adjustable shunt reference source and the voltage dividing bypass. The voltage dividing bypass comprises at least two divider resistors and at least one bypass node formed between the divider resistors. The three-terminal adjustable shunt reference source comprises a reference terminal connected to the at least one bypass node, and a voltage value of the second series node is defined as the reference voltage. 
     In one embodiment, the reference voltage is generated by the comparator. 
     In one embodiment, the power calibration circuit is a bridge-type power calibration circuit. 
     In one embodiment, the power calibration circuit is a bridgeless-type power calibration circuit. 
     Accordingly, compared with conventional technique, the invention comprises the following features: by further comprising the auxiliary voltage feedback unit in addition to the main voltage feedback unit, the invention interferes the feedback voltage received by the control unit when the voltage of the output terminal of the power calibration circuit rises to trigger a condition of the second state. The control unit is capable of performing responded control in advance to prevent the post-stage circuits such as high-voltage capacitor from withstanding excessive voltage, so that the post-stage circuits is effectively protected. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a first schematic diagram of implementation of a control module of a power calibration circuit of the invention. 
         FIG.  2    is a second schematic diagram of implementation of the control module of the power calibration circuit of the invention. 
         FIG.  3    is a circuit diagram of a first embodiment of an auxiliary voltage feedback unit of the invention. 
         FIG.  4    is a circuit diagram of a second embodiment of the auxiliary voltage feedback unit of the invention. 
         FIG.  5    is a third schematic diagram of implementation of the control module of the power calibration circuit of the invention. 
         FIG.  6    is a fourth schematic diagram of implementation of the control module of the power calibration circuit of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The detailed description and technical content of the invention are described below with reference to the accompanying drawings. 
     Please refer to  FIG.  1   ,  FIG.  2    and  FIG.  3   . The invention provides a control module  10  which controls the operation of a power calibration circuit  20 . Any type of power calibration circuit that is capable of performing feedback control can be applied in the invention, for example,  FIG.  1    and  FIG.  2    are implementations of a bridge-type power calibration circuit, and  FIG.  5    and  FIG.  6    are implementations of a bridgeless-type power calibration circuit. Please refer to  FIG.  1   ,  FIG.  2    and  FIG.  3   . The control module  10  of the invention comprises a control unit  11 , a main voltage feedback unit  12 , and an auxiliary voltage feedback unit  13 . The control unit  11  is connected to at least one power switch  201  of the power calibration circuit  20 . The control unit  11  determines to provide an on-off signal  111  to the power switch  201  based on a feedback voltage  121  and a feedback current signal  161 . The feedback voltage  121  is given by the main voltage feedback unit  12  and the auxiliary voltage feedback unit  13 . The feedback current signal  161  is obtained from the power calibration circuit  20 . The operation of the power switch  201  is determined by the on-off signal  111 . In one embodiment, the control unit  11  is a chip and a plurality of electronic components implemented with the chip. 
     On the other hand, the main voltage feedback unit  12  is connected to an output terminal  202  of the power calibration circuit  20  and the control unit  11 . In one embodiment, the main voltage feedback unit  12  is a feedback circuit commonly used for feedback control of the power calibration circuit  20 . The main voltage feedback unit  12  is an important part of the control unit  11  to implement feedback control, the main voltage feedback unit  12  does not change in status, and after the power calibration circuit  20  is started, the feedback voltage  121  is provided to the control unit  11 . 
     Furthermore, both the auxiliary voltage feedback unit  13  and the main voltage feedback unit  12  are connected to a feedback input terminal  112  of the control unit  11 . The auxiliary voltage feedback unit  13  comprises a voltage dividing circuit  131  and a voltage limiting circuit  132 . The voltage dividing circuit  131  is connected to the output terminal  202  and includes at least one voltage dividing node  133 . Moreover, the voltage dividing circuit  131  comprises at least two resistors  134  connected in series. Furthermore, the voltage limiting circuit  132  is connected to the at least one voltage dividing node  133  and the control unit  11 . If a voltage of the at least one voltage dividing node  133  is not higher than a reference voltage (Vref), the voltage limiting circuit  132  is in a first state without interfering the feedback voltage  121  provided from the main voltage feedback unit  12  to the control unit  11 . If a voltage of the at least one voltage dividing node  133  is higher than the reference voltage (Vref), the voltage limiting circuit  132  is in a second state that interferes the feedback voltage  121  provided from the main voltage feedback unit  12  to the control unit  11  with an interference voltage  135 . 
     Accordingly, the auxiliary voltage feedback unit  13  of the invention only acts on the control unit  11  when certain conditions are met; in the rest of the time, the auxiliary voltage feedback unit  13  will not interfere with the feedback voltage  121  provided from the main voltage feedback unit  12  to the feedback input terminal  112 . Furthermore, since a voltage of the output terminal  202  of the power calibration circuit  20  is not a fixed value, the voltage of the output terminal  202  varies with a load of the power calibration circuit  20 , which means that a voltage of the voltage dividing node  133  will change accordingly. Please refer to  FIG.  1   , when a voltage of the voltage dividing node  133  is lower than the reference voltage (Vref), the auxiliary voltage feedback unit  13  is in the first state, and the voltage limiting circuit  132  does not provide any voltage for feedback control to the feedback input terminal  112  of the control unit  11 . Please refer to  FIG.  3   , when a voltage of the voltage dividing node  133  is higher than the reference voltage (Vref), the auxiliary voltage feedback unit  13  is in the second state, and the voltage limiting circuit  132  outputs the interference voltage  135 , to the control unit  11  to interfere with the feedback voltage  121  provided by the main voltage feedback unit  12  to the control unit  11 , so that the control unit  11  modulates the on-off signal  111  based on a voltage value after interference of the interference voltage  135 . The interference voltage  135  can be regarded as another feedback voltage. In this way, the invention solves the problems that the post-stage circuits, such as a high-voltage capacitor  30 , need to be designed with high voltage since the feedback response of the power calibration circuit  20  is too slow. In other words, by disposition of the auxiliary voltage feedback unit  13 , the post-stage circuits of the power calibration circuit  20  are effectively protected without withstanding excessive voltage. 
     Since the output terminal  202  of the power calibration circuit  20  has a relatively high voltage, the output terminal  202  is difficult to be directly used for feedback control. In conventional technique, a voltage of the output terminal  202  is divided by the voltage dividing circuit  131  as described above to obtain a voltage that is more suitable for work. However, when the invention is implemented, the auxiliary voltage feedback unit  13  does not share the voltage dividing circuit  131  with the main voltage feedback unit  12 , and the main voltage feedback unit  12  is implemented with another voltage dividing circuit (not shown in the figures). 
     Please refer to  FIG.  3   . In one embodiment, the voltage limiting circuit  132  comprises a comparator  136  and a diode  137  connected to the comparator  136 . The comparator  136  comprises a non-inverting input terminal  138  connected to the voltage dividing node  133 , an inverting input terminal  139  receiving the reference voltage (Vref), and an output terminal  140  connected to the diode  137 . The diode  137  is used to isolate the main voltage feedback unit  12  and the auxiliary voltage feedback unit  13 . The diode  137  comprises a positive electrode  141  connected to the output terminal  140 , and a negative electrode  142  connected to the control unit  11 . In one embodiment, the comparator  136  comprises a positive power terminal  144  connected to an operating voltage source  143 , and a negative power terminal  145  connected to a ground reference point  146 . In addition, in one embodiment, the voltage limiting circuit  132  further comprises a first resistor  147 , and a first capacitor  148  connected in series with the first resistor  147 , wherein a first series node formed between the first resistor  147  and the first capacitor  148  is connected to the output terminal  140  of the comparator  136 , and one end of the first resistor  147  not connected in series with the first capacitor  148  is connected to the operating voltage source  143 . In another embodiment, the voltage limiting circuit  132  comprises a second resistor  150  connected to the negative electrode  142  of the diode  137 . 
     The reference voltage (Vref) mentioned above can be generated by the comparator  136  directly as shown in  FIG.  4   , or can be generated as shown in  FIG.  3   . In the embodiment shown in  FIG.  3   , the voltage limiting circuit  132  comprises a reference voltage generating circuit  151  to generate the reference voltage (Vref). The reference voltage generating circuit  151  comprises a third resistor  152  connected to the operating voltage source  143 , a three-terminal adjustable shunt reference source  154  connected in series with the third resistor  152 , a voltage dividing bypass  155  connected in parallel with the three-terminal adjustable shunt reference source  154 , and a second capacitor  156  connected in parallel with the three-terminal adjustable shunt reference source  154  and the voltage dividing bypass  155 . A second series node  153  is formed between the third resistor  152  and the three-terminal adjustable shunt reference source  154 . The voltage dividing bypass  155  comprises at least two voltage dividing resistors  157  and at least one bypass node  158  formed between the at least two voltage dividing resistors  157 . In addition, the three-terminal adjustable shunt reference source  154  comprises a reference terminal  159  connected to the bypass node  158 . In one embodiment, the three-terminal adjustable shunt reference source  154  is a TL431 electronic component sold on the market. In addition, a voltage value of the second series node  153  is defined as the reference voltage (Vref).