CN115811208A - Switching power supply, alternating current-direct current conversion circuit and control method - Google Patents
Switching power supply, alternating current-direct current conversion circuit and control method Download PDFInfo
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- CN115811208A CN115811208A CN202210986311.4A CN202210986311A CN115811208A CN 115811208 A CN115811208 A CN 115811208A CN 202210986311 A CN202210986311 A CN 202210986311A CN 115811208 A CN115811208 A CN 115811208A
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Abstract
The invention provides a switching power supply, an alternating current-direct current conversion circuit and a control method, wherein the voltage detection and control circuit calculates the voltage on a bus by detecting the voltage at the output side of a direct current-direct current conversion unit, and when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls a capacitor switch to be conducted, so that a second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be switched off, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
Description
Technical Field
The invention relates to the field of power supplies, in particular to a switching power supply, an alternating current-direct current conversion circuit and a control method.
Background
The ac-dc conversion circuit is used in a switching power supply in various electronic devices, and in the ac-dc conversion circuit, firstly, an ac voltage needs to be rectified into a dc voltage by a rectifying circuit and output to a bus, and then, a dc-dc conversion unit converts the voltage on the bus into a desired target voltage.
The operating principle of the ac-dc converter circuit determines that harmonics are easily generated on the ac circuit connected thereto, and in order to reduce the harmonics, the prior art adopts various input current harmonic suppression circuits to suppress the harmonics, however, these schemes are complicated.
Disclosure of Invention
Research shows that many people use the same switching power supply to move around the world, the alternating current voltage of the power grid in each region is different in magnitude, and harmonic waves caused by the same switching power supply in the power grid under the input of the alternating current voltage of different magnitude are different. In view of the above situation, it is a primary object of the present invention to provide a switching power supply, an ac-dc converter circuit, and a control method, which can adaptively reduce both harmonic and power consumption in various regions with different ac voltages of a power grid.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
an alternating current-direct current conversion circuit comprises a rectification circuit, a first bus capacitor and a direct current-direct current conversion unit, wherein the rectification circuit is used for rectifying input alternating current voltage to obtain direct current voltage and supplying the direct current voltage to a bus; the second bus capacitor and the capacitor switch are connected in series between the bus and the ground; the voltage detection and control circuit calculates the voltage on the bus by detecting the voltage at the output side of the DC-DC conversion unit, and when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be conducted, so that the second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be switched off, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
Preferably, the dc-dc conversion unit includes a transformer, a filter capacitor and a rectifier diode, and the voltage detection and control circuit includes a voltage sampling circuit and a control circuit; the voltage sampling circuit comprises a sampling capacitor, a first sampling resistor, a second sampling resistor, a third sampling resistor and a diode; the control circuit is provided with a reference voltage input end and a voltage detection end; the first end of the secondary coil of the transformer is connected with the anode of the rectifier diode, the cathode of the rectifier diode is connected with the anode of the filter capacitor, the second end of the secondary coil of the transformer, the cathode of the filter capacitor and the anode of the sampling capacitor are all grounded, and the end of the primary coil of the transformer, which is connected with the bus, and the second end of the secondary coil are homonymous ends; the cathode of the diode is connected with the first end of the secondary coil of the transformer, the anode of the diode is connected with the cathode of the sampling capacitor, the cathode of the sampling capacitor is sequentially grounded through a third sampling resistor and a second sampling resistor, the common end of the third sampling resistor and the second sampling resistor is connected with the voltage detection end and is connected with the reference voltage input end through the first sampling resistor, and the reference voltage is input into the reference voltage input end; and the control circuit calculates the voltage on the bus by detecting the voltage of the voltage detection end.
Preferably, the control circuit comprises a control unit and an optical coupler, and the control unit is provided with the voltage detection end and the reference voltage input end; the control unit calculates the voltage on the bus by detecting the voltage of the voltage detection end, and when the voltage on the bus is smaller than a bus voltage threshold value, the control unit controls the conduction of the capacitance switch through an optocoupler, so that the second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the capacitor switch to be switched off through an optical coupler, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
Preferably, the control circuit further includes a first voltage-dividing resistor and a second voltage-dividing resistor, the optical coupler includes an optical coupler transmitting element and an optical coupler receiving element, and the control unit further has a control end; the control unit controls the optocoupler emitting element to emit light or not to emit light through a control end; the optocoupler receiving element and the second voltage-dividing resistor are connected in series between the driving voltage and the control end of the capacitive switch, and the control end of the capacitive switch is grounded through the first voltage-dividing resistor; and satisfies the following conditions: (VCC-V0) × R4/(R5 + R4) > Vth2; wherein Vth2 is a starting voltage of the capacitive switch, VCC is a magnitude of the driving voltage, V0 is a conduction voltage drop of the opto-coupler receiving element, and R4 and R5 are a resistance value of the first divider resistor and a resistance value of the second divider resistor, respectively.
Preferably, the capacity of the second bus capacitor is larger than the capacity of the first bus capacitor.
Preferably, the dc-dc conversion unit is a flyback dc-dc conversion unit.
Preferably, the bus bar is grounded through the second bus bar capacitor and the capacitor switch in sequence.
The invention also provides a switching power supply which comprises any one of the alternating current-direct current conversion circuits.
The invention also provides a control method of the alternating current-direct current conversion circuit, the voltage detection and control circuit calculates the voltage on the bus by detecting the voltage at the output side of the direct current-direct current conversion unit; when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be conducted, so that the second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is greater than or equal to the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be switched off so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
Preferably, the control method adopts the ac-dc conversion circuit, the control unit calculates the voltage on the bus by detecting the voltage at the voltage detection end, and when the voltage on the bus is smaller than the bus voltage threshold, the control unit controls the conduction of the capacitive switch through an optocoupler, so that the second bus capacitor is connected to the charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the capacitor switch to be switched off through an optical coupler, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
Preferably, the control method adopts the ac-dc conversion circuit, when the voltage on the bus is less than the bus voltage threshold, the control unit controls the optocoupler emitting element to emit light, the optocoupler receiving element is turned on after receiving the light, and the voltage at the control end of the capacitive switch is maintained at the voltage of the first voltage-dividing resistor, so that the capacitive switch is controlled to be turned on; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the optical coupling emitting element not to emit light, the optical coupling receiving element does not receive light and is switched off, the voltage of the control end of the capacitive switch is pulled down to zero, and therefore the capacitive switch is controlled to be switched off.
[ PROBLEMS ] the present invention
The voltage detection and control circuit calculates the voltage on the bus by detecting the voltage on the output side of the direct current-direct current conversion unit, when the voltage on the bus is smaller than a bus voltage threshold value (namely the currently accessed alternating current voltage is smaller), the second bus capacitor is accessed to a charge-discharge loop of the bus by controlling the conduction of the capacitor switch, the second bus capacitor can also provide a part of discharge current, the first bus capacitor and the second bus capacitor only need to be charged and discharged with smaller amplitude on the whole, the ripple on the bus is relatively smaller, and the harmonic in the alternating current circuit connected with the rectification circuit is less. When the voltage on the bus is greater than the bus voltage threshold (i.e. the currently accessed alternating voltage is greater), at this time, because the voltage on the bus is greater, in order to meet the output power requirement of the output end and maintain the requirement of the target voltage, only the bus capacitor is needed to provide a smaller discharging current, and the discharging current provided by the first bus capacitor does not cause a larger ripple on the bus, so that the second bus capacitor is not accessed to the charging and discharging loop of the bus by controlling the capacitor switch to be disconnected, thereby avoiding more devices such as the second bus capacitor and the capacitor switch to be accessed to the bus to cause more power consumption, and simultaneously, the ripple caused in the alternating current circuit because the bus ripple is smaller. The scheme can adaptively realize the reduction of harmonic waves and the reduction of power consumption in all areas with different alternating-current voltages by using a simple circuit structure.
Other advantages of the present invention will be described in the detailed description, and those skilled in the art will understand the technical features and technical solutions presented in the description.
Drawings
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. In the figure:
FIG. 1 is a schematic diagram of an AC-DC converter circuit according to an embodiment of the present invention;
fig. 2 is a schematic diagram of an ac-dc converter circuit according to another embodiment of the present invention.
Detailed Description
The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth in order to avoid obscuring the nature of the present invention, and well-known methods, procedures, and components have not been described in detail.
Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".
In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
Fig. 1 is an ac-dc conversion circuit according to an embodiment of the present invention, which includes a rectifier circuit, a first bus capacitor EC1, a second bus capacitor EC2, a capacitor switch Q2, a voltage detection and control circuit, and a dc-dc conversion unit.
The input end of the rectifying circuit is used for inputting alternating-current voltage, and the rectifying circuit is used for rectifying the input alternating-current voltage to obtain direct-current voltage and supplying the direct-current voltage to the bus. The rectifying circuit may be a full-bridge rectifying circuit or a half-bridge rectifying circuit.
The input end of the dc-dc conversion unit inputs the voltage on the bus, and the dc-dc conversion unit is configured to convert the voltage on the bus into an output target voltage, specifically, the dc-dc conversion unit is controlled to convert the voltage on the bus into the output target voltage, which can be set according to a suitable requirement, and for common consumer electronics, 5V, 12V, 24V, and the like are relatively common target voltages. The dc-dc conversion unit may be of various types, for example, may be an isolated type, i.e., a conversion unit with a transformer, such as a flyback conversion unit and a forward conversion unit, or may be a non-isolated type, e.g., a bulk circuit. The dc-dc conversion unit shown in fig. 2 belongs to an isolated flyback conversion unit, and includes a switching tube Q1, a transformer T, a rectifier diode D2, and a filter capacitor EC3, wherein a first end of a primary coil of the transformer T is connected to a bus, a second end of the primary coil of the transformer T is grounded through the switching tube Q1, a first end of a secondary coil of the transformer T is connected to an anode of the rectifier diode D2, a cathode of the rectifier diode D2 is connected to an anode of the filter capacitor EC3, a cathode of the filter capacitor EC3 is grounded, a second end of the secondary coil of the transformer T is grounded, and a cathode end of the rectifier diode D2 is used as an output terminal Vout of the dc-dc conversion unit, that is, an output terminal Vout of an ac-dc conversion circuit, and the output terminal Vout outputs a target voltage, and the voltage of the output terminal Vout can be stabilized at a set target voltage by adjusting a duty ratio of a control signal PWM of the switching tube Q1.
One end of a first bus capacitor EC1 is connected with a bus, the other end of the first bus capacitor EC1 is connected with the ground, a second bus capacitor EC2 and a capacitor switch Q2 are connected between the bus and the ground in series, a voltage detection and control circuit calculates the voltage on the bus by detecting the voltage at the output side of a direct current-direct current conversion unit, and when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch Q2 to be conducted, so that the second bus capacitor EC2 is connected into a charge-discharge loop of the bus; when the voltage on the bus is greater than or equal to the bus voltage threshold, the voltage detection and control circuit controls the capacitor switch Q2 to be switched off, so that the second bus capacitor EC2 is not switched into a charge-discharge loop of the bus. In some embodiments, the capacitive switch Q2 may be a MOS transistor, such as an N-channel MOS transistor.
Because the ac voltages of different power grids in different regions are different, and have a large difference, for example, the ac voltage in china is 220V, while the ac voltage in the united states is 110V, which is twice different from the ac voltage in china, the voltages rectified and output by the rectifying circuit are also different, that is, the voltages on the bus voltages are different. When the output power requirement of the output end Vout is fixed, when the voltage on the bus is smaller than the bus voltage threshold (that is, the currently accessed ac voltage is smaller), at this time, since the voltage on the bus is smaller, in order to meet the output power requirement of the output end Vout, the bus capacitor is required to provide a larger discharge current, if only the first bus capacitor EC1 provides the discharge current, the first bus capacitor EC1 is caused to perform large-amplitude charging and discharging, which causes a large ripple on the bus, and further causes more harmonics in an ac circuit connected to a rectifier circuit, which may reduce the evaluation of the electromagnetic compatibility of the electronic device including the ac-dc conversion circuit. Therefore, in order to reduce such an influence, when the voltage on the bus is smaller than the bus voltage threshold, the capacitor switch Q2 is controlled to be turned on to connect the second bus capacitor EC2 into the bus charging and discharging circuit, and the second bus capacitor EC2 can also provide a part of discharging current, so that the first bus capacitor EC1 and the second bus capacitor EC2 only need to be charged and discharged with a small amplitude as a whole, the ripple on the bus is relatively small, and the harmonics in the ac circuit connected to the rectifying circuit are less. When the voltage on the bus is greater than the bus voltage threshold (i.e., the currently accessed ac voltage is greater), at this time, since the voltage on the bus is greater, in order to meet the output power requirement of the output terminal Vout and the requirement of maintaining the output power at the target voltage, only the bus capacitor EC1 is needed to provide a smaller discharging current, and the discharging current provided by the first bus capacitor EC1 does not cause a larger ripple on the bus, so that the second bus capacitor EC2 is not accessed into the charging and discharging loop of the bus by controlling the capacitor switch Q2 to be switched off, thereby avoiding more devices such as the second bus capacitor EC2 and the capacitor switch Q2 from being accessed into the bus to cause more power consumption, and simultaneously, the ripple caused in the ac circuit due to the smaller bus ripple can be smaller.
In summary, the voltage detection and control circuit respectively controls the second bus capacitor EC2 to be connected to or not to be connected to the charge-discharge circuit of the bus under different conditions according to the magnitude relation between the voltage on the bus and the bus voltage threshold, and can adaptively realize the reduction of the harmonic wave and the reduction of the power consumption in various regions with different alternating-current voltages. In the scheme, the bus voltage threshold can be flexibly set according to actual needs.
In addition, in some embodiments, the bus bar sequentially passes through the second bus bar capacitor EC2 and the capacitor switch Q2 to be grounded, at this time, since the capacitor switch Q2 is connected with the bus bar through the second bus bar capacitor EC2, that is, not directly connected with the bus bar, it is avoided that high voltage on the bus bar is directly applied to the capacitor switch Q2, and therefore, the capacitor switch Q2 is not broken down by the high voltage of the bus bar, and from another perspective, the capacitor switch Q2 can select a device with smaller withstand voltage, so that the cost can be saved.
As shown in fig. 2, in some embodiments, the dc-dc conversion unit includes a transformer T, and the voltage detection and control circuit includes a voltage sampling circuit and a control circuit; the voltage sampling circuit comprises a sampling capacitor C1, a first sampling resistor R1, a second sampling resistor R2, a third sampling resistor R3 and a diode D1; the control circuit is provided with a reference voltage input end VREF and a voltage detection end Vsen; the first end of the secondary coil of the transformer T is connected with the anode of a rectifier diode D2, the cathode of the rectifier diode D2 is connected with the anode of a filter capacitor EC3, the second end of the secondary coil of the transformer T, the cathode of the filter capacitor EC3 and the anode of a sampling capacitor C1 are all grounded, and the end of the primary coil of the transformer T connected with a bus and the second end of the secondary coil are homonymy ends; the cathode of the diode D1 is connected with the first end of the secondary coil of the transformer T, the anode of the diode D1 is connected with the cathode of the sampling capacitor C1, the cathode of the sampling capacitor C1 is grounded through the third sampling resistor R3 and the second sampling resistor R2 in sequence, the common end of the third sampling resistor R3 and the second sampling resistor R2 is connected with the voltage detection end Vsen and is connected with the reference voltage input end VREF through the first sampling resistor R1, and the reference voltage input end VREF inputs reference voltage Vref; the control circuit calculates the voltage on the bus by detecting the voltage of the voltage detection terminal Vsen. Because the positive pole of the sampling capacitor C1 is grounded, and the negative pole is connected with the first end of the secondary coil through the diode D1, the voltage VC1 of the negative pole of the sampling capacitor C1 meets the following conditions: VC1=0- (VDC × NS/NP-VD 1), where VDC is the voltage on the bus, VD1 is the voltage drop of diode D1, and NS and NP are the number of turns of the secondary and primary windings of transformer T, respectively. Since the voltage VC1 of the negative electrode of the sampling capacitor C1 is a negative value, the current flowing through the third sampling resistor R3 is equal to the sum of the current flowing through the first sampling resistor R1 and the current flowing through the second sampling resistor R2, that is: (Vsen-VC 1)/R3 = (Vref-Vsen)/R1 + Vsen/R2, where Vsen is a voltage detected by the voltage detection terminal Vsen, vref is a reference voltage, and R1, R2, and R3 are resistance values of the first sampling resistor R1, the second sampling resistor R2, and the third sampling resistor R3, respectively, the voltage VC1 can be calculated by solving the above equation, and the voltage VDC on the bus can be calculated by combining the above equation. In this embodiment, since the anode of the sampling capacitor C1 is grounded, the cathode of the sampling capacitor C1 is connected to the first end of the secondary coil through the diode D1, and the end of the primary coil of the transformer T connected to the bus and the second end of the secondary coil are dotted terminals, the voltage VC1 of the cathode of the sampling capacitor C1 can change along with the voltage of the bus.
In some embodiments, the control circuit comprises a control unit IC and an optocoupler, the control unit IC having a voltage detection terminal Vsen and a reference voltage input terminal VREF; the power supply end Vin of the control unit IC is connected with the anode of the filter capacitor, namely the power supply voltage of the control chip IC is the output voltage of the alternating current-direct current circuit; the control unit IC calculates the voltage on the bus by detecting the voltage of the voltage detection end Vsen, and when the voltage on the bus is smaller than the bus voltage threshold value, the control unit IC controls the conduction of the capacitance switch Q2 through the optocoupler, so that the second bus capacitor EC2 is connected into a charge-discharge loop of the bus; when the voltage on the bus is greater than or equal to the bus voltage threshold value, the control unit IC controls the capacitor switch Q2 to be switched off through the optical coupler, so that the second bus capacitor EC2 is not connected into a charge-discharge loop of the bus. In this embodiment, the capacitive switch Q2 is controlled by the optocoupler, so that isolation between the input side and the output side of the dc-dc conversion unit can be achieved, and the output side is prevented from being damaged by high voltage on the input side.
Specifically, the control circuit further comprises a first divider resistor R4 and a second divider resistor R5, the optocoupler comprises an optocoupler emitting element U1A and an optocoupler receiving element U1B, and the control unit IC further has a control end IO; the control unit IC controls the optocoupler emitting element U1A to emit light or not to emit light through the control end IO; the optocoupler receiving element U1B and the second divider resistor R5 are connected in series between the driving voltage and the control end of the capacitor switch Q2, and the control end of the capacitor switch Q2 is grounded through the first divider resistor R4; and satisfies the following conditions: (VCC-V0) × R4/(R5 + R4) > Vth2; wherein Vth2 is a starting voltage of the capacitor switch Q2, VCC is a driving voltage, V0 is a conduction voltage drop of the optocoupler receiving element U1B, and R4 and R5 are a resistance value of the first voltage dividing resistor and a resistance value of the second voltage dividing resistor, respectively. Fig. 2 shows that the second voltage-dividing resistor R5 is located between the driving voltage and the optical coupler receiving element U1B, but the positions of the second voltage-dividing resistor R5 and the optical coupler receiving element U1B may be interchanged. Fig. 2 shows one type of the optocoupler emitting element U1A and the optocoupler receiving element U1B, and other types of optocoupler devices may be used. When the bus voltage control circuit works, the control unit IC calculates the voltage on the bus by detecting the voltage of the voltage detection end Vsen, when the voltage on the bus is smaller than the bus voltage threshold value, the control unit IC controls the optocoupler emitting element U1A to emit light, the optocoupler receiving element U1B is conducted after receiving the light, and the voltage of the control end of the capacitor switch Q2 is maintained at the voltage (namely (VCC-V0) × R4/(R5 + R4)) larger than Vth2, so that the capacitor switch Q2 is controlled to be conducted, and the second bus capacitor EC2 is connected to a charge-discharge loop of the bus; when the voltage on the bus is greater than or equal to the bus voltage threshold value, the control unit IC controls the optocoupler emitting element U1A not to emit light, the optocoupler receiving element U1B does not receive light and is not conducted, and the voltage of the control end of the capacitor switch Q2 is pulled down to zero by the first divider resistor R4, so that the capacitor switch Q2 is controlled to be disconnected, and the second bus capacitor EC2 is not connected into a charge-discharge loop of the bus.
The invention also provides a switching power supply which comprises any one of the alternating current-direct current conversion circuits.
The invention also provides a control method of the alternating current-direct current conversion circuit, the voltage detection and control circuit calculates the voltage on the bus by detecting the voltage at the output side of the direct current-direct current conversion unit; when the voltage on the bus is smaller than the bus voltage threshold, the voltage detection and control circuit controls the capacitor switch Q2 to be conducted, so that the second bus capacitor EC2 is connected into a charge-discharge loop of the bus; when the voltage on the bus is greater than or equal to the bus voltage threshold, the voltage detection and control circuit controls the capacitor switch Q2 to be switched off, so that the second bus capacitor EC2 is not switched into a charge-discharge loop of the bus.
It will be appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.
It will be understood that the embodiments described above are illustrative only and not restrictive, and that various obvious and equivalent modifications and substitutions for details described herein may be made by those skilled in the art without departing from the basic principles of the invention.
Claims (11)
1. An alternating current-direct current conversion circuit comprises a rectification circuit, a first bus capacitor and a direct current-direct current conversion unit, wherein the rectification circuit is used for rectifying input alternating current voltage to obtain direct current voltage and supplying the direct current voltage to a bus;
the second bus capacitor and the capacitor switch are connected in series between the bus and the ground;
the voltage detection and control circuit calculates the voltage on the bus by detecting the voltage at the output side of the DC-DC conversion unit, and when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be conducted, so that the second bus capacitor is connected to the charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be switched off, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
2. The AC-DC conversion circuit according to claim 1, wherein the DC-DC conversion unit includes a transformer, a filter capacitor and a rectifier diode,
the voltage detection and control circuit comprises a voltage sampling circuit and a control circuit;
the voltage sampling circuit comprises a sampling capacitor, a first sampling resistor, a second sampling resistor, a third sampling resistor and a diode; the control circuit is provided with a reference voltage input end and a voltage detection end;
the first end of the secondary coil of the transformer is connected with the anode of the rectifier diode, the cathode of the rectifier diode is connected with the anode of the filter capacitor, the second end of the secondary coil of the transformer, the cathode of the filter capacitor and the anode of the sampling capacitor are all grounded, and the end of the primary coil of the transformer, which is connected with the bus, and the second end of the secondary coil are homonymous ends;
the cathode of the diode is connected with the first end of the secondary coil of the transformer, the anode of the diode is connected with the cathode of the sampling capacitor, the cathode of the sampling capacitor is sequentially grounded through a third sampling resistor and a second sampling resistor, the common end of the third sampling resistor and the second sampling resistor is connected with the voltage detection end and is connected with the reference voltage input end through the first sampling resistor, and the reference voltage is input into the reference voltage input end;
the control circuit calculates the voltage on the bus by detecting the voltage of the voltage detection end.
3. The AC-DC conversion circuit according to claim 2,
the control circuit comprises a control unit and an optical coupler, wherein the control unit is provided with a voltage detection end and a reference voltage input end;
the control unit calculates the voltage on the bus by detecting the voltage of the voltage detection end, and when the voltage on the bus is smaller than a bus voltage threshold value, the control unit controls the conduction of the capacitance switch through an optocoupler, so that the second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the capacitor switch to be switched off through an optical coupler, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
4. The AC-DC conversion circuit according to claim 3,
the control circuit further comprises a first voltage-dividing resistor and a second voltage-dividing resistor, the optical coupler comprises an optical coupler transmitting element and an optical coupler receiving element, and the control unit further comprises a control end;
the control unit controls the optocoupler emitting element to emit light or not to emit light through a control end;
the optocoupler receiving element and the second voltage-dividing resistor are connected in series between the driving voltage and the control end of the capacitive switch, and the control end of the capacitive switch is grounded through the first voltage-dividing resistor;
and satisfies the following conditions: (VCC-V0) × R4/(R5 + R4) > Vth2; wherein Vth2 is a starting voltage of the capacitive switch, VCC is a magnitude of the driving voltage, V0 is a conduction voltage drop of the opto-coupler receiving element, and R4 and R5 are a resistance value of the first divider resistor and a resistance value of the second divider resistor, respectively.
5. The AC-DC conversion circuit according to claim 1,
the capacity of the second bus capacitor is greater than the capacity of the first bus capacitor.
6. The AC-DC conversion circuit according to claim 1,
the direct current-direct current conversion unit is a flyback direct current-direct current conversion unit.
7. The AC-DC conversion circuit according to claim 1,
the bus is grounded through the second bus capacitor and the capacitor switch in sequence.
8. A switching power supply comprising an ac-dc converter circuit according to any one of claims 1-7.
9. A control method of an AC-DC conversion circuit according to claim 1,
the voltage detection and control circuit calculates the voltage on the bus by detecting the voltage on the output side of the DC-DC conversion unit;
when the voltage on the bus is smaller than the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be conducted, so that the second bus capacitor is connected to a charge-discharge loop of the bus;
when the voltage on the bus is larger than or equal to the bus voltage threshold value, the voltage detection and control circuit controls the capacitor switch to be switched off, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
10. The control method according to claim 9, wherein the AC-DC conversion circuit according to claim 3 is used,
the control unit calculates the voltage on the bus by detecting the voltage of the voltage detection end, and when the voltage on the bus is smaller than a bus voltage threshold value, the control unit controls the capacitor switch to be switched on through an optocoupler, so that the second bus capacitor is connected to a charge-discharge loop of the bus; when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the capacitor switch to be switched off through an optical coupler, so that the second bus capacitor is not connected to the charge-discharge loop of the bus.
11. The control method according to claim 10, wherein the AC-DC conversion circuit according to claim 4 is used,
when the voltage on the bus is smaller than a bus voltage threshold value, the control unit controls an optical coupling emitting element to emit light, the optical coupling receiving element is conducted after receiving the light, the voltage of the control end of the capacitive switch is maintained at the voltage of the first divider resistor, and therefore the capacitive switch is controlled to be conducted;
when the voltage on the bus is larger than or equal to the bus voltage threshold value, the control unit controls the optical coupling emitting element not to emit light, the optical coupling receiving element does not receive light and is switched off, the voltage of the control end of the capacitive switch is pulled down to zero, and therefore the capacitive switch is controlled to be switched off.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210986311.4A CN115811208A (en) | 2022-08-17 | 2022-08-17 | Switching power supply, alternating current-direct current conversion circuit and control method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210986311.4A CN115811208A (en) | 2022-08-17 | 2022-08-17 | Switching power supply, alternating current-direct current conversion circuit and control method |
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| CN115811208A true CN115811208A (en) | 2023-03-17 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210986311.4A Pending CN115811208A (en) | 2022-08-17 | 2022-08-17 | Switching power supply, alternating current-direct current conversion circuit and control method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115811208A (en) |
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2022
- 2022-08-17 CN CN202210986311.4A patent/CN115811208A/en active Pending
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