Voltage conversion circuit for wide input voltage, ammeter and control method

Abstract

The invention discloses a voltage conversion circuit for wide input voltage, an electric meter and a control method, a first-stage power conversion circuit detects the magnitude of voltage of an input bus, when a detection signal of the input bus is smaller than a set threshold voltage, the first-stage power conversion circuit performs driving work, otherwise, the first-stage power conversion circuit stops driving work, and the first-stage power conversion circuit stops driving when the detection signal of the input bus is smaller than the set threshold voltage; the second-stage power conversion circuit receives the output voltage of the first-stage power conversion circuit so as to convert the output voltage into expected output voltage, and the set threshold voltage is set according to the withstand voltage value of a power tube of the first-stage power conversion circuit. According to the technical scheme of the invention, the withstand voltage of the main power switch tube of the first-stage power conversion circuit can be controlled, so that the switch tubes with medium and low withstand voltage can be selected, the switching loss and cost of the switch tubes are greatly reduced, and the stress of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuit control, and more specifically, to a voltage conversion circuit, an electric meter and a control method for wide input voltage. Background Art

[0002] The voltage conversion circuit is used to convert the input voltage into the output voltage to supply the load. In some applications of the voltage conversion circuit, it is necessary to convert a wider range of input voltage into output voltage. For example, in some electric meter application circuits, the grid voltages of different countries are very different. The wide range of input voltage can range from tens of volts to hundreds of volts. In order to take into account various usage scenarios, the voltage conversion circuit in the electric meter needs to take into account a very wide input voltage.

[0003] For such a wide input voltage range, a two-stage power conversion circuit is generally required, such as Figure 1 As shown, it is a two-stage power combination solution of high-voltage linear LDO voltage conversion and flyback voltage conversion. Since the voltage size of the subsequent flyback voltage conversion needs to be guaranteed, the previous LDO voltage conversion needs to bear a higher voltage drop. Therefore, the voltage resistance requirement of its power switch tube is relatively high. The voltage resistance requirement of the power switch tube required in the existing LDO solution may reach more than 1000V, which will also lead to a huge increase in cost, high power consumption, and increased peripheral complexity.

[0004] Therefore, it is necessary to provide an improved technical solution to overcome the above technical problems existing in the prior art. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a voltage conversion circuit, an electric meter and a control method for a wide input voltage, so as to solve the technical problems of the voltage conversion circuit in the prior art, such as high cost, high power consumption and complex peripheral circuits.

[0006] A voltage conversion circuit for wide input voltage is provided, comprising a first-stage power conversion circuit and a second-stage power conversion circuit, wherein the first-stage power conversion circuit receives an input bus voltage to convert it into a first output voltage, and the first-stage power conversion circuit receives the first output voltage to convert it into a desired output voltage, and the first-stage power conversion circuit comprises a controller and a main power switch tube, wherein the controller detects the voltage magnitude of the input bus voltage and obtains a detection signal characterizing the input bus voltage, and when the detection signal is less than a set threshold voltage, the controller controls the main power switch tube to drive, otherwise, the controller controls the main power switch tube to stop driving, wherein the set threshold voltage is set according to the withstand voltage value of the main power switch tube.

[0007] Preferably, the set threshold voltage is equal to the withstand voltage of the main power switch tube minus the sum of the voltage drop borne by the inductive device and the voltage peak of the voltage drop.

[0008] Preferably, it also includes a first capacitor and a second capacitor, the first capacitor is connected to the input end of the first-stage power conversion circuit, and the second capacitor is connected to the output end of the first-stage power conversion circuit, wherein the capacitance of the second capacitor is greater than the capacitance of the first capacitor.

[0009] Preferably, the voltage range of the wide input voltage is 30V to 800V, and the withstand voltage of the main power switch tube is less than or equal to 1200V.

[0010] Preferably, the first-stage power conversion circuit is a flyback power conversion circuit, and the second-stage power conversion circuit is one of a boost, buck-boost or step-down power conversion circuit.

[0011] Preferably, it further comprises a sampling circuit, wherein the sampling circuit is used to connect the node of the input bus, and the controller is connected to the sampling circuit to obtain a detection signal representing the input bus voltage.

[0012] Preferably, the controller includes a comparison circuit, a switch signal control module and a logic operation module. The comparison circuit is used to compare the detection voltage with the set threshold voltage to obtain a comparison signal. When the comparison signal is in a high-level effective state, it indicates that the detection signal is greater than the set threshold voltage. The switch signal control module receives a compensation signal to obtain a turn-on signal and a turn-off signal accordingly. The compensation signal is obtained according to a feedback signal of the output voltage. The logic operation module receives the comparison signal and the turn-on signal and the turn-off signal to obtain a gate-level signal for controlling the state of the main power switch tube.

[0013] Preferably, the comparison circuit comprises a hysteresis comparator.

[0014] Preferably, the switch signal control module includes an on-signal generating module and a off-signal generating module, the on-signal generating module receives the compensation signal and the inductor current of the first-stage power conversion circuit to generate an on-signal for controlling the on-state of the main power tube, so as to control the operating frequency of the main power switch tube, and the off-signal generating module receives the compensation signal to generate an off-signal for controlling the off-state of the main power tube, so as to control the operating time of the main power switch tube.

[0015] Preferably, the logic operation module includes a first switch, an OR gate and a trigger, one end of the first switch receives the turn-on signal, and the other end is connected to the set end of the trigger, the state of the first switch is controlled by the comparison signal, when the comparison signal is in a low-level invalid state, the first switch is turned on, the OR gate receives the turn-off signal and the comparison signal, and its output end is connected to the reset end of the trigger, and the trigger output end outputs the gate level signal.

[0016] Preferably, the logic operation module includes a trigger, a set end of the trigger receives the turn-on signal, a reset end receives the turn-off signal, and an enable end receives the comparison signal. When the comparison signal is in a high-level effective state, the trigger output remains low.

[0017] In a second aspect, a control method for a voltage conversion circuit for a wide input voltage is provided, wherein the voltage conversion circuit comprises a first-stage power conversion circuit and a second-stage power conversion circuit, wherein the first-stage power conversion circuit receives an input bus voltage to convert it into a first output voltage, and the first-stage power conversion circuit receives the first output voltage to convert it into a desired output voltage, and is characterized in that it comprises the steps of: the first-stage power conversion circuit detects the voltage magnitude of the input bus voltage, obtains a detection signal characterizing the input bus voltage, when the detection signal is less than a set threshold voltage, the controller controls the main power switch tube to drive, and when the detection signal is greater than the set threshold voltage, the controller controls the main power switch tube to stop driving, wherein the set threshold voltage is set according to the withstand voltage value of the main power switch tube.

[0018] Preferably, the set threshold voltage is equal to the withstand voltage of the main power switch tube minus the sum of the voltage drop borne by the inductive device and the voltage peak of the voltage drop.

[0019] Preferably, when the detection signal is less than a set threshold voltage, the controller controls the main power switch tube to perform driving operation, specifically including: receiving the compensation signal and the inductor current of the first power stage circuit to generate a turn-on signal for controlling the main power tube to turn on, and receiving the compensation signal to generate a turn-off signal for controlling the main power tube to turn off.

[0020] Preferably, the on-signal controls the operating frequency of the main power switch tube to not exceed a maximum frequency, and / or the off-signal controls the operating time of the main power switch tube to be a constant on-time.

[0021] Preferably, the first-stage power conversion circuit is a flyback power conversion circuit, and the second-stage power conversion circuit is one of a boost, buck-boost or step-down power conversion circuit.

[0022] The voltage conversion circuit, electric meter and control method for wide input voltage of the present invention are adopted. The first-stage power conversion circuit detects the voltage of the input bus. When the detection signal of the input bus is less than the set threshold voltage, the first-stage power conversion circuit performs driving operation. Otherwise, the first-stage power conversion circuit stops driving operation. The second-stage power conversion circuit receives the output voltage of the first-stage power conversion circuit to convert it into the desired output voltage, wherein the set threshold voltage is set according to the withstand voltage value of the power tube of the first-stage power conversion circuit. Through the technical solution of the present application, the withstand voltage of the main power switch tube of the first-stage power conversion circuit can be controlled, so that medium and low withstand voltage switch tubes can be selected, which can reduce the switching loss of the switch tube, improve the stress of the system, and the cost and control of the overall system are controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A circuit block diagram of a voltage conversion circuit according to the prior art

[0024] Figure 2 is a circuit block diagram of a first embodiment of a voltage conversion circuit for wide input voltage according to the present invention;

[0025] Figure 3 is a circuit block diagram of a second embodiment of a voltage conversion circuit for wide input voltage according to the present invention;

[0026] Figure 4 According to the present invention Figure 2 An implementation circuit diagram of the controller in;

[0027] Figure 5 According to the present invention Figure 4 A circuit diagram for realizing a switch signal control module;

[0028] Figure 6 According to the present invention Figure 4 A circuit block diagram of a first embodiment of a logic operation module in FIG.

[0029] Figure 7 According to the present invention Figure 4 A circuit block diagram of a second embodiment of the logic operation module in FIG. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0031] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details.

[0032] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0033] Figure 2 is a circuit block diagram of a first embodiment of a voltage conversion circuit for wide input voltage according to the present invention; Figure 3 is a circuit block diagram of a second embodiment of a voltage conversion circuit for wide input voltage according to the present invention; Figure 4 According to the present invention Figure 2 A circuit diagram of a controller in . Figure 2 The voltage conversion circuit for wide input voltage of the present application includes a first-stage power conversion circuit and a second-stage power conversion circuit. The first-stage power conversion circuit receives an input bus voltage VBUS to convert it into a first output voltage Vout1. The first-stage power conversion circuit receives the first output voltage Vout1 to convert it into a desired output voltage Vout2. Figure 2 Taking the three-phase input voltage as an example, the three-phase input voltage is rectified and filtered to obtain the input bus voltage VBUS. The controller of the first-stage power conversion circuit detects the voltage magnitude VBUS of the input bus voltage to obtain a detection signal V representing the input bus voltage. B , when the detection signal is less than the set threshold voltage V REF When the controller controls the main power switch tube of the first-stage power conversion circuit to drive, otherwise, the controller controls the main power switch tube to stop driving, wherein the set threshold voltage V REFIt is set according to the withstand voltage value of the main power switch tube. Here, the set threshold voltage is set to be equal to the withstand voltage value of the main power switch tube minus the voltage drop borne by the inductive device in the first-stage power conversion circuit, or the set threshold voltage is equal to the withstand voltage value of the main power switch tube minus the sum of the voltage drop borne by the inductive device and the voltage spike of the voltage drop. For example, if the withstand voltage value of the main power switch tube is 1000V, and the voltage drop borne by the inductive device such as the inductor or the winding is 200V, then the set threshold voltage can be 800V, so that a very large input voltage range can be taken into account. For example, even if the input is 500VAC, each power device of the circuit can work safely. Considering that the voltage drop borne by the inductive device may generate some peak voltages, such as 100V, in some abnormal situations, the set threshold voltage can be 700V, which can still take into account a very large input voltage range. Therefore, the solution of the present application can select a medium and low withstand voltage power switch tube in a very large input voltage range application scenario, which can greatly reduce the cost and control difficulty of the power switch tube.

[0034] like Figure 3 , the first-stage power conversion circuit takes a flyback voltage conversion circuit as an example, but the switching power supply of the present application is not limited thereto. The flyback voltage conversion circuit includes a main power switch tube Q1 on the primary side, a primary winding of a transformer T1, and a freewheeling tube and a secondary winding of a transformer T1 on the secondary side. The flyback voltage conversion circuit receives an input voltage, which may be a single-phase or three-phase input voltage, and obtains a bus voltage VBUS after rectification and filtering. The flyback voltage conversion circuit also includes a controller, which generates a switch gate signal Gate to control the switch working state of the main power switch tube Q1. The first-stage power conversion circuit may also be a circuit of boost, buck or other suitable topology, and the second-stage power conversion circuit may be one of a boost, buck-boost or buck power conversion circuit, and a Buck-Boost buck-boost circuit is taken as an example here.

[0035] Continue to refer Figure 3 , the voltage conversion circuit also includes a first capacitor C1 and a second capacitor C2, the first capacitor is connected to the input end of the first-stage power conversion circuit, and the second capacitor is connected to the output end of the first-stage power conversion circuit, wherein the capacitance of the second capacitor is greater than the capacitance of the first capacitor. Here, the capacitance of the first capacitor C1 is set to be smaller so that the signal detected by the controller is closer to the input voltage, and the capacitance of the second capacitor C2 is set to be larger so that when the output voltage of the first-stage power conversion circuit is lower, the input voltage of the second-stage power conversion circuit can still maintain a suitable value to meet the requirements of the final output constant voltage.

[0036] refer to Figure 3The voltage conversion circuit further includes a sampling circuit, the sampling circuit is used to connect the node of the input bus, such as the node of the first capacitor C1 and the input end of the first power conversion circuit, the sampling circuit includes sampling resistors Rup and Rdown connected in series, and the controller is connected to the middle node of the sampling resistors Rup and Rdown to obtain a detection signal V representing the input bus voltage. B .

[0037] Specifically, refer to Figure 4 According to the present invention Figure 2 A circuit diagram of a controller in the embodiment; the controller includes a comparison circuit, a switch signal control module and a logic operation module, the comparison circuit is used to compare the detection voltage V B and the set threshold voltage V REF To obtain the comparison signal V BUS P When the comparison signal is in a high-level valid state, it indicates that the detection signal is greater than the set threshold voltage. At this time, the first power conversion circuit drives its main power switch tube to perform switching operation. When the comparison signal is in a low-level invalid state, it indicates that the detection signal is less than the set threshold voltage. At this time, the first power conversion circuit stops driving its main power switch tube to work.

[0038] The switch signal control module receives the compensation signal Vcomp to obtain the opening signal V 开 and the shutdown signal V 关 , the compensation signal is obtained according to the feedback signal of the output voltage. Here, a compensation signal comp is obtained as follows: the first-stage power conversion circuit also includes an optocoupler, the interior of the optocoupler includes a light-emitting diode and a photoresistor, the high-voltage side of the secondary winding is connected to the positive electrode of the light-emitting diode via a resistor, and the output voltage feedback signal is connected to the negative electrode of the light-emitting diode after the signal of the voltage-dividing resistor is compared with the reference voltage, so as to send a control signal to the light-emitting diode to adjust the size of the optocoupler current of the light-emitting diode, thereby adjusting the conduction state of the photoresistor, one end of the photoresistor is connected to the reference ground, and the other end is connected to the compensation (COMP) pin of the primary controller of the flyback power conversion circuit. The logic operation module receives the comparison signal, the turn-on signal and the turn-off signal to obtain the gate-level signal Gate for controlling the state of the main power switch tube.

[0039] Preferably, the comparison circuit includes a hysteresis comparator to prevent the bus input voltage from switching continuously near the set threshold voltage, causing repeated driving of the main power switch tube and low efficiency. By setting the hysteresis comparator, the bus input voltage switches near the set threshold voltage with a hysteresis and will not jump repeatedly.

[0040] refer to Figure 5 According to the present invention Figure 4 A circuit diagram of an implementation of a switch signal control module in the embodiment of the present invention; the switch signal control module includes an on-signal generating module and an off-signal generating module, the on-signal generating module specifically includes a frequency limiting module and a VS_ZCD sampling and holding module, the frequency limiting module receives the compensation signal Vcomp to obtain a maximum frequency curve, and when the frequency of the first-stage power conversion circuit reaches the maximum frequency, a frequency limiting signal is generated, and the VS_ZCD sampling and holding module receives the inductor current V CS , sampling its zero-crossing point, that is, the inductor current at the end of the secondary side freewheeling, generates a zero-crossing signal, and when both the frequency-limiting signal and the zero-crossing signal are valid, generates an on signal V to control the on of the main power tube 开 The above-mentioned turn-on signal generating module can well control the operating frequency of the main power switch tube to prevent the frequency from getting out of control; the turn-off signal generating module receives the compensation signal Vcomp to generate a turn-off signal V for controlling the turn-off of the main power tube. 关 , to control the working time of the main power switch tube. Here, preferably, the module is configured to control the on-time of the main power switch tube to be a constant on-time, such as generating a set time signal through a signal associated with the compensation signal Vcomp, and when the on-time input voltage VBUS of the main power switch tube is calculated to be low, sufficient energy can still be delivered. Those skilled in the art will know that the shutdown signal generating module can also generate a shutdown signal according to a peak current control method or an average current control method to control the shutdown of the main power switch tube. The peak current control method or the average current control method can be a circuit structure in the prior art, which is not listed here one by one.

[0041] refer to Figure 6 According to the present invention Figure 4 The circuit block diagram of the first embodiment of the logic operation module in FIG. 1; the logic operation module includes a first switch S1, an OR gate and a trigger. Here, an RS trigger is taken as an example. One end of the first switch receives the opening signal V 开 , the other end is connected to the set end S of the trigger, the first switch is controlled by the comparison signal, specifically, when the comparison signal is in a low level invalid state, the first switch is turned on, and the comparison signal V BUS_P The negative signal controls the first switch, and the OR gate receives the shutdown signal V 关 and the comparison signal V BUS_P, whose output end is connected to the reset end R of the trigger, and the trigger output end outputs the gate signal Gate. Its working principle is: when the detection signal is less than the set threshold voltage, the comparison signal is in a low level invalid state, the first switch S1 is turned on, at this time, if the opening signal V 开 If the gate signal Gate is high, the main power switch is turned on. If the shutdown signal V 关 When the detection signal is greater than the set threshold voltage, the comparison signal is in a high level effective state, the first switch S1 is turned off, regardless of the opening signal V 开 and the shutdown signal V 关 No matter what state the main power switch tube is in, it remains off. In this way, the bus input voltage is detected through a two-stage solution. When the detected voltage is lower than the set threshold voltage, the first-stage power conversion circuit is allowed to work, thereby reducing the stress of the main power switch tube and using medium and low voltage tubes, reducing the cost of the system. At the same time, it can reduce the switching loss of the main power switch tube and improve the stress of the system.

[0042] refer to Figure 7 According to the present invention Figure 4 A circuit block diagram of a second embodiment of the logic operation module in FIG. Figure 7 The embodiment shown is another implementation of the logic operation module. The logic operation module includes a trigger, which includes a reset terminal R, a set terminal S and an enable terminal EN. The set terminal S of the trigger receives the enable signal V 开 , the reset terminal R receives the shutdown signal V 关 , the enable terminal receives the comparison signal V BUS_P , here, specifically the comparison signal V BUS_P When the comparison signal is in a high level valid state, the trigger is not enabled to work, and the output remains low; when the comparison signal is in a low level invalid state, the trigger is enabled to work, and the output remains according to the opening signal V 开 and the shutdown signal V 关 The logic operation module of this embodiment is simple and easy to control, and can also achieve the beneficial effect of reducing the stress of the main power switch tube and reducing the cost of the system.

[0043] It should be noted that the second-stage power conversion circuit in the embodiment of the present invention is a DC-DC voltage conversion circuit to achieve output constant voltage. Figure 3 The embodiment in the embodiment takes Buck-Boost as an example, and its power level topology and control scheme can be technical schemes in the prior art as long as the DC-DC voltage conversion function can be realized.

[0044] Finally, the present application provides a control method for a voltage conversion circuit with a wide input voltage, comprising the steps of: the first-stage power conversion circuit detects the voltage of the input bus voltage, obtains a detection signal characterizing the input bus voltage, when the detection signal is less than a set threshold voltage, the controller controls the main power switch tube to drive, when the detection signal is greater than the set threshold voltage, the controller controls the main power switch tube to stop driving, wherein the set threshold voltage is set according to the withstand voltage value of the main power switch tube. The set threshold voltage is set to be equal to the withstand voltage value of the main power switch tube minus the voltage drop borne by the inductive device in the first-stage power stage circuit, or the set threshold voltage is equal to the withstand voltage value of the main power switch tube minus the voltage drop borne by the inductive device and the sum of the voltage spike of the voltage drop.

[0045] Preferably, when the detection signal is less than a set threshold voltage, the controller controls the main power switch tube to perform a driving operation specifically including:

[0046] The compensation signal and the inductor current of the first power stage circuit are received to generate an on signal for controlling the main power tube to be turned on, and the compensation signal is received to generate an off signal for controlling the main power tube to be turned off.

[0047] Preferably, the on-signal controls the operating frequency of the main power switch tube to not exceed a maximum frequency, and the off-signal controls the operating time of the main power switch tube to be a constant on-time.

[0048] Finally, the present application discloses an electric meter that receives an input signal from a power grid and converts it into an output signal for output, including a voltage conversion circuit for a wide input voltage in any of the above-mentioned embodiments, wherein the input signal is a single-phase input voltage or a three-phase input voltage.

[0049] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the present invention, and do not limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the present invention, but these changes and modifications fall within the scope of protection of the present invention.

[0050] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0051] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A voltage conversion circuit for wide input voltage, comprising a first-stage power conversion circuit and a second-stage power conversion circuit, wherein the first-stage power conversion circuit receives an input bus voltage to convert it into a first output voltage, and the first-stage power conversion circuit receives the first output voltage to convert it into a desired output voltage, characterized in that: The first-stage power conversion circuit includes a controller and a main power switch tube. The controller detects the voltage of the input bus voltage to obtain a detection signal representing the input bus voltage. When the detection signal is less than the set threshold voltage, the controller controls the main power switch tube to drive, otherwise, the controller controls the main power switch tube to stop driving. The set threshold voltage is set according to the withstand voltage value of the main power switch tube.

2. The voltage conversion circuit for wide input voltage according to claim 1, characterized in that: The set threshold voltage is set to be equal to the withstand voltage value of the main power switch tube minus the sum of the voltage drop borne by the inductive device and the voltage peak of the voltage drop.

3. The voltage conversion circuit for wide input voltage according to claim 1, characterized in that: Also includes a first capacitor and a second capacitor, The first capacitor is connected to the input end of the first-stage power conversion circuit, and the second capacitor is connected to the output end of the first-stage power conversion circuit. Wherein, the capacitance of the second capacitor is greater than the capacitance of the first capacitor.

4. The voltage conversion circuit for wide input voltage according to claim 2, characterized in that: The voltage range of the wide input voltage is 30V to 800V, and the withstand voltage of the main power switch tube is less than or equal to 1200V.

5. The voltage conversion circuit for wide input voltage according to claim 1, characterized in that: The first-stage power conversion circuit is a flyback power conversion circuit, and the second-stage power conversion circuit is one of a boost, buck-boost or buck power conversion circuit.

6. The voltage conversion circuit for wide input voltage according to claim 1, characterized in that: It also includes a sampling circuit, the sampling circuit is used to connect the node of the input bus, The controller is connected to the sampling circuit to obtain a detection signal representing the input bus voltage.

7. The voltage conversion circuit for wide input voltage according to claim 6, characterized in that: The controller includes a comparison circuit, a switch signal control module and a logic operation module. The comparison circuit is used to compare the detection voltage with the set threshold voltage to obtain a comparison signal. When the comparison signal is in a high-level effective state, it indicates that the detection signal is greater than the set threshold voltage. The switch signal control module receives a compensation signal to obtain an on signal and an off signal accordingly, wherein the compensation signal is obtained according to a feedback signal of the output voltage. The logic operation module receives the comparison signal, the turn-on signal and the turn-off signal to obtain a gate-level signal for controlling the state of the main power switch tube.

8. The voltage conversion circuit for wide input voltage according to claim 7, characterized in that: The comparison circuit includes a hysteresis comparator.

9. The voltage conversion circuit for wide input voltage according to claim 7, characterized in that: The switch signal control module includes an on-signal generating module and an off-signal generating module. The on-signal generating module receives the compensation signal and the inductor current of the first power stage circuit to generate an on-signal for controlling the on-state of the main power switch tube, so as to control the operating frequency of the main power switch tube. The shutdown signal generating module receives the compensation signal to generate a shutdown signal for controlling the shutdown of the main power tube, so as to control the working time of the main power switch tube.

10. The voltage conversion circuit for wide input voltage according to claim 7, characterized in that: The logic operation module includes a first switch, an OR gate and a trigger. One end of the first switch receives the turn-on signal, and the other end is connected to the set end of the trigger. The state of the first switch is controlled by the comparison signal. When the comparison signal is in a low-level invalid state, the first switch is turned on. The OR gate receives the shutdown signal and the comparison signal, and its output terminal is connected to the reset terminal of the trigger. The trigger output terminal outputs the gate level signal.

11. The voltage conversion circuit for wide input voltage according to claim 7, characterized in that: The logic operation module includes a trigger, The set end of the trigger receives the turn-on signal, the reset end receives the turn-off signal, and the enable end receives the comparison signal. When the comparison signal is in an active high state, the flip-flop output remains low.

12. A control method for a voltage conversion circuit with a wide input voltage, characterized in that: The voltage conversion circuit comprises a first-stage power conversion circuit and a second-stage power conversion circuit, wherein the first-stage power conversion circuit receives an input bus voltage to convert it into a first output voltage, and the first-stage power conversion circuit receives the first output voltage to convert it into a desired output voltage, and is characterized in that it comprises the steps of: The first-stage power conversion circuit detects the voltage of the input bus voltage to obtain a detection signal representing the input bus voltage. When the detection signal is less than the set threshold voltage, the controller controls the main power switch tube to drive, and when the detection signal is greater than the set threshold voltage, the controller controls the main power switch tube to stop driving. The set threshold voltage is set according to the withstand voltage value of the main power switch tube.

13. The control method for a voltage conversion circuit with a wide input voltage according to claim 12, characterized in that: The set threshold voltage is set to be equal to the withstand voltage value of the main power switch tube minus the sum of the voltage drop borne by the inductive device and the voltage peak of the voltage drop.

14. The control method for a voltage conversion circuit with a wide input voltage according to claim 12, characterized in that: When the detection signal is less than the set threshold voltage, the controller controls the main power switch tube to perform driving operation, specifically including: receiving the compensation signal and the inductor current of the first-stage power conversion circuit to generate an on signal for controlling the on of the main power tube, The compensation signal is received to generate a shutdown signal for controlling the main power tube to shut down.

15. The control method for a voltage conversion circuit with a wide input voltage according to claim 14, characterized in that: The on-signal controls the operating frequency of the main power switch tube not to exceed a maximum frequency, and / or the off-signal controls the operating time of the main power switch tube to be a constant on-time.

16. The control method for a voltage conversion circuit with a wide input voltage according to claim 12, characterized in that: The first-stage power conversion circuit is a flyback power conversion circuit, and the second-stage power conversion circuit is one of a boost, buck-boost or buck power conversion circuit.

17. An electric meter that receives an input signal from a power grid and converts it into an output signal for output, characterized in that: A voltage conversion circuit for wide input voltage comprising any one of claims 1 to 11, The input signal is a single-phase input voltage or a three-phase input voltage.

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