A single-switch positive and negative output power factor correction circuit and converter

Abstract

The application belongs to the technical field of power supply, and particularly relates to a single-switch positive and negative output power factor correction circuit and a converter. With the AC input zero line as a reference, when the AC voltage of the AC input live line is in a positive half cycle, a BOOST circuit composed of an inductor, a rectifier bridge, a switch tube, a first freewheeling diode and a first capacitor outputs a positive bus output voltage; when the AC voltage of the AC input live line is in a negative half cycle, a BOOST circuit composed of an inductor, a rectifier bridge, a switch tube, a second freewheeling diode and a second capacitor outputs a negative bus output voltage; a current detection module is used for detecting an inductor current, and a voltage detection module is used for detecting a bus output voltage, which is a positive bus output voltage or a negative bus output voltage. The application realizes power factor correction of positive and negative bus outputs based on one switch tube. The circuit structure and control are simple, and the volume and cost of electromagnetic elements in the power factor correction converter are reduced.

Description

Technical Field

[0001] This invention belongs to the field of power supply technology, specifically relating to a single-switch positive and negative output power factor correction circuit and converter. Background Technology

[0002] A PFC (Power Factor Correction) converter is used to control the input current to follow the voltage waveform, maintain phase with the input voltage, adjust the power factor to approximately 1, and ensure a stable DC output voltage. For example, Chinese patent application CN118174534A discloses a PFC power factor correction circuit and its control system and method, including a power circuit and a control system. The power circuit, acting as the power factor correction circuit, performs power factor correction under the control of the control system, obtaining an output DC voltage and a sinusoidal input current. The power circuit includes four diodes D1-D4, an AC filter inductor L1, an AC filter capacitor C1, a boost inductor L2, a reverse fast recovery diode D5, a main switch S1, a sampling resistor R1, an electrolytic capacitor C2, and a load resistor R2. The control system includes an adaptive limiting high-order differential feedback control module and a dual-integral single-cycle control module. The adaptive limiting high-order differential feedback control module controls the output DC voltage of the power circuit to track the given voltage reference value and obtains the input signal of the dual-integral single-cycle control module. The dual-integral single-cycle control module generates the drive signal of the power circuit based on the input signal, controlling the input current of the power circuit to be in phase and frequency with the input voltage. This scheme is a traditional BOOST PFC topology circuit, a conventional single-phase positive output PFC circuit. The output bus voltage is a positive bus voltage close to 400Vdc, and it cannot output a negative bus voltage. Its control system focuses on the S-domain digital control strategy, and designs the control flow through the Laplace domain transfer function.

[0003] To output positive and negative bus voltages, a dual half-wave power factor correction circuit for small-to-medium power high-frequency uninterruptible power supplies (UPS) has been proposed. The topology of the dual half-wave power factor correction circuit is as follows: Figure 1 As shown, two Boost circuits form a dual-channel PFC, controlling the positive and negative half-cycles of the AC input respectively, thus controlling the positive and negative bus outputs. Since the two PFCs control the positive and negative bus outputs separately, the circuit topology is complex and costly. It employs an average current-mode control strategy with a multiplier, which requires three stages: sampling bus voltage feedback, two-channel current feedback, and input voltage feedforward. This control method is complex and has a slow dynamic response. Summary of the Invention

[0004] The purpose of this invention is to provide a single-switch positive and negative output power factor correction circuit and converter to solve the problems of complex topology and high cost of existing positive and negative output power factor correction circuits.

[0005] To address the aforementioned technical problems, the first aspect of this invention provides a single-switch positive and negative output power factor correction circuit, comprising an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module. The positive terminal of the first capacitor is connected to the positive bus, and the negative terminal of the second capacitor is connected to the negative bus. Using the AC input neutral line as a reference, when the AC voltage of the AC input live wire is in the positive half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, first freewheeling diode, and first capacitor, outputting a positive bus voltage. When the AC voltage of the AC input live wire is in the negative half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, second freewheeling diode, and second capacitor, outputting a negative bus voltage. The current detection module is used to detect the inductor current, and the voltage detection module is used to detect the bus output voltage, which can be either a positive or negative bus output voltage.

[0006] In one possible implementation, the rectifier bridge is a diode bridge rectifier circuit.

[0007] In one possible implementation, the current detection module is a current transformer connected in series between the AC input live wire and the inductor.

[0008] In one possible implementation, the voltage detection module employs a resistor divider circuit, which is positioned between the positive busbar and the reference ground, or between the negative busbar and the reference ground; the reference ground is the midpoint between the positive and negative busbars.

[0009] To address the aforementioned technical problems, a second aspect of the present invention provides a single-switch positive and negative output power factor correction converter, comprising a positive and negative output power factor correction circuit and a control module. The positive and negative output power factor correction circuit includes an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module. The positive terminal of the first capacitor is connected to the positive bus, and the negative terminal of the second capacitor is connected to the negative bus. Using the AC input neutral line as a reference, when the AC voltage of the AC input live wire is in the positive half-cycle, the inductor, rectifier bridge, switching transistor, and first freewheeling diode... A diode and a first capacitor form a BOOST circuit, outputting a positive bus voltage. When the AC voltage of the AC input live wire is in the negative half-cycle, an inductor, a rectifier bridge, a switching transistor, a second freewheeling diode, and a second capacitor form a BOOST circuit, outputting a negative bus voltage. A current detection module is used to detect the inductor current, and a voltage detection module is used to detect the bus output voltage, which can be either a positive or negative bus output voltage. A control module is used to generate a drive signal for the switching transistor based on the bus output voltage and the inductor current, and to control the switching transistor based on the drive signal to achieve power factor correction.

[0010] In one possible implementation, the control module employs a single-cycle control strategy, including an error amplifier, a resettable integrator, a comparator, a subtractor, and a flip-flop. The inputs of the error amplifier are the sampled value of the bus output voltage and the reference voltage, and the output serves as the inputs of the resettable integrator and the subtractor. Another input of the resettable integrator is connected to reference ground, and its output serves as the input of the comparator. The reset switch is controlled by the flip-flop. Another input of the subtractor is the equivalent voltage of the inductor current, and its output serves as another input of the comparator. The flip-flop generates a drive signal for the switching transistor based on the comparator output.

[0011] In one possible implementation, the trigger is an RS trigger, where the S terminal receives a clock signal, the R terminal receives the comparator output, the Q terminal outputs a drive signal, and the Q-not output terminal is connected to the reset switch of a resettable integrator.

[0012] In one possible implementation, an isolation drive circuit is also included, comprising an optocoupler and a push-pull amplifier circuit. The optocoupler is used to isolate the control module and the switching transistor, and to perform voltage conversion on the drive signal output by the trigger. The push-pull amplifier circuit is used to amplify the output signal of the optocoupler and then drive the switching transistor.

[0013] In one possible implementation, the rectifier bridge is a diode bridge rectifier circuit.

[0014] In one possible implementation, the voltage detection module employs a resistor divider circuit, which is positioned between the positive busbar and the reference ground, or between the negative busbar and the reference ground; the reference ground is the midpoint between the positive and negative busbars.

[0015] The beneficial effects of this invention are as follows: The single-switch positive and negative output power factor correction circuit designed in this invention uses the AC input neutral line as a reference. When the AC voltage of the AC input live line is in the positive half-cycle, if the switch is turned on, the power transmission path is: AC input live line, inductor, rectifier bridge arm in the positive half-cycle, switch, AC input neutral line; if the switch is turned off, the power transmission path is: AC input live line, inductor, first freewheeling diode, first capacitor, AC input neutral line. This ensures that when the AC voltage of the AC input live line is in the positive half-cycle, the BOOST circuit, composed of the inductor, rectifier bridge, switch, first freewheeling diode, and first capacitor, outputs a positive bus voltage.

[0016] When the AC voltage on the AC input live wire is in the negative half-cycle, if the switching transistor is on, the power transmission path is: AC input neutral wire, rectifier bridge arm conducting in the negative half-cycle, switching transistor, inductor, AC input live wire; if the switching transistor is off, the power transmission path is: AC input neutral wire, second capacitor, second freewheeling diode, inductor, AC input live wire. This ensures that when the AC voltage on the AC input live wire is in the negative half-cycle, the BOOST circuit, composed of the inductor, rectifier bridge, switching transistor, second freewheeling diode, and second capacitor, outputs a negative bus voltage.

[0017] By detecting the inductor current and the positive or negative bus output voltage, and controlling the switching transistor to turn it on and off, positive and negative output power factor correction can be achieved. This invention requires only one switching transistor to switch between the positive and negative half-cycles of the AC input between two BOOST circuits, achieving power factor correction for both positive and negative bus outputs. The circuit structure and control are simple, reducing the size of electromagnetic components in the power factor correction converter, simplifying the positive and negative output power factor correction circuit, lowering the cost of the positive and negative output power factor correction circuit, and the switching transistor only bears half of the DC bus voltage, resulting in low voltage stress.

[0018] The control module built using analog operational amplifiers controls the positive and negative output PFC circuits, making control simpler, enabling continuous-time power factor correction control, faster dynamic response, and more concise and practical. Attached Figure Description

[0019] Figure 1 This is a topology diagram of a dual half-wave power factor correction circuit in the prior art;

[0020] Figure 2 This is a circuit diagram of the single-switch positive and negative output power factor correction circuit of the present invention;

[0021] Figure 3 This is a schematic diagram of the control module principle of the present invention;

[0022] Figure 4This is the isolation drive circuit diagram of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0024] This invention proposes a novel single-switch positive and negative output power factor correction circuit topology and introduces single-cycle control technology for control. The circuit structure and control of this topology are simple. The switching transistor only bears half of the DC bus voltage, so the voltage stress is low. Moreover, the single-cycle control method makes the total harmonic distortion of the current smaller and the power factor correction performance better.

[0025] Implementation of a single-switch positive and negative output power factor correction circuit

[0026] The present invention provides a single-switch positive and negative output power factor correction circuit, comprising an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module.

[0027] One end of the inductor is connected to the AC input live wire (AC L), and the other end of the inductor is connected to one AC input terminal of the rectifier bridge, and to the first capacitor via the first freewheeling diode, and to the second capacitor via the second freewheeling diode. The rectifier bridge can be a diode bridge rectifier circuit.

[0028] The first capacitor, the second capacitor, and the other AC input terminal of the rectifier bridge are used to connect to the AC input neutral line (AC N). The first and second capacitors are electrolytic capacitors. In one embodiment, the first and second capacitors are connected in series, with the midpoint of the series connection connected to the AC input neutral line. The positive terminal of the first capacitor is connected to the positive busbar, and the negative terminal of the second capacitor is connected to the negative busbar.

[0029] The switching transistor is connected to the positive and negative DC output terminals of the rectifier bridge. The switching transistor can be a MOSFET or an IGBT, or other controllable switching transistor.

[0030] With the AC input neutral line as the reference, when the AC voltage of the AC input live line is in the positive half-cycle, the BOOST circuit is composed of an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, and a first capacitor, and the positive bus output voltage is generated; when the AC voltage of the AC input live line is in the negative half-cycle, the BOOST circuit is composed of an inductor, a rectifier bridge, a switching transistor, a second freewheeling diode, and a second capacitor, and the negative bus output voltage is generated.

[0031] The current detection module is used to detect the inductor current, and the voltage detection module is used to detect the bus output voltage, which can be either positive or negative.

[0032] The current detection module can use a current transformer, which is connected in series between the AC input live wire and the inductor.

[0033] The voltage detection module can use a resistor voltage divider circuit, which is set between the positive bus BUS+ and the reference ground GND, or between the negative bus BUS- and the reference ground GND; the reference ground is the midpoint between the positive and negative buses.

[0034] like Figure 2 As shown, the current transformer CT is connected in series between AC L and inductor L1. The other end of inductor L1 and AC N are respectively connected to one of the AC input terminals of rectifier bridge B1. At the same time, the other end of inductor L1 is connected to one end of freewheeling diode D5 and freewheeling diode D6 respectively. The other end of freewheeling diode D5 is connected to two series electrolytic capacitors E1 and E2. The midpoint of the electrolytic capacitor is connected to AC N. Switch K1 is connected to the positive and negative DC output terminals of rectifier bridge. The four diodes in rectifier bridge B1 are D1, D2, D3 and D4 respectively.

[0035] The single-switch positive and negative output power factor correction circuit of the present invention switches between two BOOST circuits according to the different positive and negative half-cycles of the AC input.

[0036] With AC N as the reference, when AC L is in its positive half-cycle, a BOOST circuit is formed by inductor L1, diodes D2 and D3, switching transistor K1, freewheeling diode D5, and electrolytic capacitor E1, thereby outputting the positive bus voltage. If the switching transistor is on, the power transmission path is: AC L, inductor L1, diode D2, switching transistor K1, diode D3, AC N. If the switching transistor is off, the power transmission path is: AC L, inductor L1, freewheeling diode D5, electrolytic capacitor E1, AC N.

[0037] When AC L is in the negative half-cycle, the BOOST circuit, composed of inductor L1, diode D1, diode D4, switching transistor K1, freewheeling diode D6, and electrolytic capacitor E2, can output a negative bus voltage. If the switching transistor is on, the power transfer path is: AC N, diode D4, switching transistor K1, diode D1, inductor L1, AC L. If the switching transistor is off, the power transfer path is: AC N, electrolytic capacitor E2, freewheeling diode D6, inductor L1, AC L.

[0038] The circuit topology described above in this invention can output a bus voltage of ±400Vdc when a 220V AC sinusoidal signal is input, that is, +400V from BUS+ to GND, -400V from BUS- to GND, and a total bus voltage of 800Vdc.

[0039] Positive and negative output power factor correction can be achieved by controlling the switching transistor's on and off states. Preferably, a single-cycle control strategy can be employed, using analog operational amplifiers in conjunction with analog hardware such as resistors and capacitors to implement single-cycle positive and negative output power factor correction control. This enables continuous-time control, provides faster dynamic response, and offers a simpler and more practical design. Power factor correction can be performed based on the detected positive bus output voltage and inductor current (i.e., single-cycle control using a stable positive bus output voltage), or it can be performed based on the detected negative bus output voltage and inductor current (i.e., control using a stable negative bus output voltage). For example, when using a stable positive bus output voltage for single-cycle control, by ensuring the consistency of the parameters of the single-switch positive and negative output power factor correction circuit, such as the parameters of the switching transistor, diode, and electrolytic capacitor, the symmetry of the single-switch positive and negative output power factor correction circuit parameters can ensure that the negative bus output voltage matches and remains stable with the positive bus output voltage.

[0040] Implementation of a single-switch positive and negative output power factor correction converter

[0041] The present invention provides a single-switch positive and negative output power factor correction converter, including a positive and negative output power factor correction circuit and a control module.

[0042] A single-switch positive and negative output power factor correction circuit includes an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module. The positive terminal of the first capacitor is connected to the positive bus, and the negative terminal of the second capacitor is connected to the negative bus.

[0043] One end of the inductor is connected to the AC input live wire (AC L), and the other end of the inductor is connected to one AC input terminal of the rectifier bridge, and to the first capacitor via the first freewheeling diode, and to the second capacitor via the second freewheeling diode. The rectifier bridge can be a diode bridge rectifier circuit.

[0044] The first capacitor, the second capacitor, and the other AC input terminal of the rectifier bridge are used to connect to the AC input neutral line (AC N). The first and second capacitors are electrolytic capacitors. In one embodiment, the first and second capacitors are connected in series, with the midpoint of the series connection connected to the AC input neutral line.

[0045] The switching transistor is connected to the positive and negative DC output terminals of the rectifier bridge. The switching transistor can be a MOSFET or an IGBT, or other controllable switching transistor.

[0046] With the AC input neutral line as the reference, when the AC voltage of the AC input live line is in the positive half-cycle, the BOOST circuit is composed of an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, and a first capacitor, and the positive bus output voltage is generated; when the AC voltage of the AC input live line is in the negative half-cycle, the BOOST circuit is composed of an inductor, a rectifier bridge, a switching transistor, a second freewheeling diode, and a second capacitor, and the negative bus output voltage is generated.

[0047] The current detection module is used to detect the inductor current, and the voltage detection module is used to detect the bus output voltage, which can be either positive or negative.

[0048] The current detection module can use a current transformer, which is connected in series between the AC input live wire and the inductor.

[0049] The voltage detection module can use a resistor voltage divider circuit, which is set between the positive bus BUS+ and the reference ground GND, or between the negative bus BUS- and the reference ground GND; the reference ground is the midpoint between the positive and negative buses.

[0050] The single-switch positive and negative output power factor correction circuit switches between two BOOST circuits based on the different positive and negative half-cycles of the AC input.

[0051] The control module generates drive signals for the switching transistors based on the bus output voltage and inductor current, and controls the switching transistors according to the drive signals to complete positive power factor correction. That is, power factor correction can be performed based on the detected positive bus output voltage and inductor current, or it can be performed based on the detected negative bus output voltage and inductor current.

[0052] Preferably, the control module employs a single-cycle control strategy. For example, single-cycle control can be implemented by stabilizing the output voltage of the bus. The single-cycle control strategy is described below.

[0053] The purpose of single-cycle control is to make the inductor current i L Follow the input voltage waveform u in At the same time, the output voltage U0 of the bus must be kept stable at a given value. Assuming that the inductor current is proportional to the input voltage and is in phase, the entire converter can be equivalent to a pure resistor R. e Then we get Formula 1:

[0054] u in =i L R e

[0055] Where R e i is the equivalent resistance of the PFC converter. L U is the instantaneous value of the inductor current. inThe instantaneous value of the sinusoidal input voltage is, for a Boost-type PFC converter, the input voltage u within one cycle. in The relationship between the bus output voltage U0 and the duty cycle d of the switching transistor is given by formula 2:

[0056] u in =U0(1-d)

[0057] Combining formulas 1 and 2, we get formula 3:

[0058] i L R e =U0(1-d)

[0059] Assume R s For the equivalent current sensing resistor in the PFC converter, Equation 3 is transformed to obtain Equation 4:

[0060]

[0061] make:

[0062]

[0063] Simplified, formula 5 can be obtained:

[0064] U m -i L R s =U m d

[0065] set up To turn off the duty cycle, .

[0066] If the duty cycle d satisfies Formula 5, then the inductor current and input voltage can be guaranteed to be proportional and in phase. Setting the converter's switching period to T, when the switching frequency is much greater than the input voltage frequency, it can be assumed that the inductor current and regulating voltage remain essentially constant within one switching cycle. Let U... m By constructing the controlled variable, we obtain a single-period control equation system:

[0067]

[0068] As can be seen from the single-cycle control equations, each switching cycle compares U... 1(t) and U 2(t) By controlling the size of the value of the switch and the turn-off time of the switching transistor, the required duty cycle d can be obtained, thus achieving power factor correction.

[0069] Therefore, this invention designs a control module based on the single-cycle control principle, consisting of operational amplifiers, resistors, and capacitors. The control module includes an error amplifier, a resettable integrator, a comparator, a subtractor, and a flip-flop. The inputs of the error amplifier are the sampled value of the bus output voltage and the reference voltage; its output serves as the inputs of the resettable integrator and the subtractor. The other input of the resettable integrator is connected to reference ground, and its output serves as the input of the comparator; the reset switch is controlled by the flip-flop. The other input of the subtractor is the equivalent voltage of the inductor current, and its output serves as the other input of the comparator. The flip-flop generates the drive signal for the switching transistor based on the comparator output.

[0070] For example, the error amplifier inputs the sampled value of the bus output voltage and the reference voltage, and its output is the inverting input of a resettable integrator and the non-inverting input of a subtractor. When using a stable positive bus output voltage for single-cycle control, the sampled value of the bus output voltage input to the error amplifier is the positive bus output voltage sampled value. When using a stable negative bus output voltage for single-cycle control, the sampled value of the bus output voltage input to the error amplifier is the absolute value of the negative bus output voltage sampled value.

[0071] The non-inverting input of the resettable integrator is connected to the reference ground, and the output is the non-inverting input of the comparator. The reset switch is controlled by a trigger.

[0072] The inverting input of the subtractor is the inductor current equivalent voltage, and the output is the comparator's inverting input. The inductor current is detected by the current transformer, and then converted into an inductor current equivalent voltage through a diode rectifier circuit and an equivalent current sensing resistor.

[0073] The flip-flop generates the drive signal for the switching transistor based on the comparator output. An RS flip-flop can be used, where the S terminal receives the clock signal, the R terminal receives the comparator output, the Q terminal outputs the drive signal, and the Q-not output is connected to the reset switch of the resettable integrator.

[0074] The converter also includes an isolation drive circuit, which comprises an optocoupler and a push-pull amplifier circuit. The optocoupler isolates the control module from the switching transistor and performs voltage conversion on the drive signal output from the trigger. The push-pull amplifier circuit amplifies the output signal from the optocoupler to drive the switching transistor. The drive signal frequency of the isolation drive circuit is constant, but the duty cycle is not fixed. By controlling the on-time of the switching transistor, the bus output voltage and inductor current of the converter are controlled, thereby achieving positive and negative output power factor correction.

[0075] like Figure 4As shown, the drive signals DRV and GND sent by the control module are isolated and converted by optocouplers, and then sent to the push-pull amplifier circuit composed of R8, R9, Q2, and Q3. The DC voltages VCC and -VCC are filtered by capacitor E3 and used as the power supply for the push-pull circuit. R10, R11, and R12 serve as the drive resistor and gate-source resistor of the switching transistor.

[0076] When single-cycle control is implemented using a stable positive bus output voltage, the control module, such as Figure 3 As shown. The error amplifier consists of operational amplifier N1, resistor R1, and capacitor C1, with its non-inverting input connected to the positive bus reference voltage V. ref The inverting terminal is connected to the positive bus, and the output voltage sampling value V is... sam The positive bus reference voltage and the positive bus output voltage sample values ​​are fed together into the error amplifier, and the output of the error amplifier is U. m The output of the error amplifier is connected to the inverting input of the resettable integrator, and simultaneously connected to the non-inverting input of the subtractor via resistor R2. The non-inverting input of the subtractor is connected to reference ground via resistor R3.

[0077] The resettable integrator consists of operational amplifier N2, capacitor C2, and a reset switch. Its non-inverting input is connected to reference ground, and its output is connected to the non-inverting input of a comparator. The reset switch is controlled by the Q-not output of the flip-flop. m As the inverting input of a resettable integrator, the integrator's output during one switching cycle is:

[0078]

[0079] The subtractor consists of operational amplifier N4, resistors R2, R3, R4, and R5, where R2 = R3 = R4 = R5. The inductor current is equivalent to the voltage across the circuit (i). L(t) R s The input is fed to the inverting input of the subtractor via resistor R4, and the inverting input is connected to the output of the subtractor via resistor R5. Within one switching cycle, the output of the subtractor is:

[0080] U 1(t) =U m -i L(t) R s

[0081] The inverting input of the comparator is connected to the output of the subtractor, and the comparator outputs a pulse width modulation (PWM) wave. The S terminal of the RS flip-flop is connected to the clock signal, the R terminal is connected to the comparator output, the Q terminal outputs a PWM signal (drive signal) and is connected to the isolation driver, and the Q-not output is connected to the reset switch of the resettable integrator.

[0082] When a clock signal arrives, the S-terminal of the RS flip-flop is set, the Q-terminal is set to "1", the Q-inverse is set to "0", the control switch K1 is turned on, and the reset switch is turned off. In this state, the resettable integrator begins to work, and the integral output voltage is:

[0083]

[0084] The inverting input of the comparator is:

[0085] U 1(t) =U m -i L(t) R s

[0086] When t / T = D, the voltages across the comparator are equal, changing the output state and resetting the RS flip-flop. The Q input is set to "0", the Q-negative input to "1", the control switch K1 is turned off, the reset switch is turned on, and the integral is cleared to zero until the next clock signal arrives. By sampling the inductor current and the positive bus output voltage signal, a PWM signal meeting the duty cycle requirements is output to control the on / off state of the main circuit's switching transistors, achieving power factor correction.

[0087] The single-switch positive and negative output power factor correction converter proposed in this invention achieves positive and negative output power factor correction with only one switch through circuit design, resulting in a simple circuit structure and reduced costs. Furthermore, the switching transistor only bears half of the DC bus voltage, thus reducing the voltage stress on the transistor. The introduction of single-cycle control technology simplifies control by requiring only sampling the inductor current and the output voltage of one of the bus terminals, resulting in lower total harmonic distortion (THD).

Claims

1. A single-switch positive and negative output power factor correction circuit, characterized in that, The circuit includes an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module. The positive terminal of the first capacitor is connected to the positive bus, and the negative terminal of the second capacitor is connected to the negative bus. Using the AC input neutral wire as a reference, when the AC voltage of the AC input live wire is in the positive half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, first freewheeling diode, and first capacitor, outputting a positive bus voltage. When the AC voltage of the AC input live wire is in the negative half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, second freewheeling diode, and second capacitor, outputting a negative bus voltage. The current detection module detects the inductor current, and the voltage detection module detects the bus output voltage, which can be either a positive or negative bus output voltage.

2. The single-switch positive and negative output power factor correction circuit according to claim 1, characterized in that, The rectifier bridge is a diode bridge rectifier circuit.

3. The single-switch positive and negative output power factor correction circuit according to claim 1 or 2, characterized in that, The current detection module is a current transformer, which is connected in series between the AC input live wire and the inductor.

4. The single-switch positive and negative output power factor correction circuit according to claim 1 or 2, characterized in that, The voltage detection module uses a resistor voltage divider circuit, which is set between the positive busbar and the reference ground, or between the negative busbar and the reference ground; the reference ground is the midpoint between the positive and negative busbars.

5. A single-switch positive and negative output power factor correction converter, comprising positive and negative output power factor correction circuits and a control module, characterized in that, The positive and negative output power factor correction circuit includes an inductor, a rectifier bridge, a switching transistor, a first freewheeling diode, a second freewheeling diode, a first capacitor, a second capacitor, a current detection module, and a voltage detection module. The positive terminal of the first capacitor is connected to the positive bus, and the negative terminal of the second capacitor is connected to the negative bus. Using the AC input neutral wire as a reference, when the AC voltage of the AC input live wire is in the positive half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, first freewheeling diode, and first capacitor, outputting a positive bus voltage. When the AC voltage of the AC input live wire is in the negative half-cycle, a BOOST circuit is formed by the inductor, rectifier bridge, switching transistor, second freewheeling diode, and second capacitor, outputting a negative bus voltage. The current detection module detects the inductor current, and the voltage detection module detects the bus output voltage, which can be either a positive or negative bus output voltage. The control module generates a drive signal for the switching transistor based on the bus output voltage and inductor current, and controls the switching transistor according to the drive signal to achieve power factor correction.

6. The single-switch positive and negative output power factor correction converter according to claim 5, characterized in that, The control module employs a single-cycle control strategy and includes an error amplifier, a resettable integrator, a comparator, a subtractor, and a flip-flop. The inputs of the error amplifier are the sampled value of the bus output voltage and the reference voltage, and the output serves as the inputs of the resettable integrator and the subtractor. The other input of the resettable integrator is connected to the reference ground, and its output serves as the input of the comparator. The reset switch is controlled by the flip-flop. The other input of the subtractor is the equivalent voltage of the inductor current, and its output serves as the other input of the comparator. The flip-flop generates the drive signal for the switching transistor based on the comparator output.

7. The single-switch positive and negative output power factor correction converter according to claim 6, characterized in that, The trigger is an RS trigger. The S terminal of the RS trigger receives the clock signal, the R terminal receives the comparator output, the Q terminal outputs the drive signal, and the Q-not output terminal is connected to the reset switch of the resettable integrator.

8. The single-switch positive and negative output power factor correction converter according to claim 7, characterized in that, It also includes an isolation drive circuit, which includes an optocoupler and a push-pull amplifier circuit. The optocoupler is used to isolate the control module and the switching transistor, and to perform voltage conversion on the drive signal output by the trigger. The push-pull amplifier circuit is used to amplify the output signal of the optocoupler to drive the switching transistor.

9. The single-switch positive and negative output power factor correction converter according to claim 5, characterized in that, The rectifier bridge is a diode bridge rectifier circuit.

10. The single-switch positive and negative output power factor correction converter according to claim 5 or 6, characterized in that, The voltage detection module uses a resistor voltage divider circuit, which is set between the positive busbar and the reference ground, or between the negative busbar and the reference ground; the reference ground is the midpoint between the positive and negative busbars.

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