Buck-Boost PFC converter and electrical equipment

Abstract

The present application discloses a Buck-Boost PFC converter and electrical equipment; it relates to the field of power electronics technology, and solves the problems of large startup surge current of traditional Boost PFC converters, high harmonic distortion of input current of bridge Buck-Boost PFC converters, and concentrated thermal stress of main switch devices. In the present application, the main switch tube at the Buck end is moved forward to the source side, and works symmetrically in the positive and negative half-power frequency cycles, which helps to reduce thermal stress and improve conversion efficiency; the converter can automatically switch between Boost, Buck-Boost, and Buck modes by real-time monitoring of input and output voltages, which improves the adaptability and reliability of the system; improves the adaptability and efficiency of the system; the variable conduction time control based on the variable slope sawtooth wave achieves unity power factor, improves overall conversion efficiency and reduces total harmonic distortion.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a Buck-Boost PFC converter and electrical equipment. Background Art

[0002] With the development and application of power electronics technology, various nonlinear loads (such as rectifiers, inverters, LED drivers, etc.) are widely used in power systems, resulting in a significant increase in harmonic currents and reactive power in the power grid, which causes the grid current waveform to be distorted and the power factor to be reduced, thus causing a series of power quality problems. Through power factor correction (PFC) technology, the power factor of the equipment can be improved, the power loss can be reduced, and the overall energy efficiency of the system can be improved. The basic principle of the PFC converter is to make the input current and input voltage in phase and maintain a sinusoidal waveform through power electronic devices and control circuits.

[0003] The dual-switch Buck-Boost PFC converter generally adopts a bridge structure, and its input current is entirely borne by the main switch tube of the previous Buck unit. When the converter switches modes, the input current is distorted, which significantly reduces the power factor value. The critical conduction mode (CRM) type dual-switch Buck-Boost PFC converter generally uses constant on-time (COT) control, which results in a non-sinusoidal input current in the buck mode, a reduced power factor, a large harmonic content, and more severe distortion.

[0004] It can be seen that how to solve the problem of high harmonic distortion and low conversion efficiency of PFC conversion is a technical problem that needs to be solved urgently by people in this field. Summary of the invention

[0005] The purpose of the present application is to provide a Buck-Boost type PFC converter and electrical equipment to solve the problems of high harmonic distortion and low conversion efficiency in PFC conversion.

[0006] In order to solve the above technical problems, the present application provides a Buck-Boost PFC converter, comprising: a Buck-Boost conversion module and a driving module;

[0007] The Buck-Boost conversion module includes three switch tubes, and the operating modes of the three switch tubes are switched between the Boost mode, the Buck-Boost mode, and the Buck mode by controlling the conduction and switching actions of the three switch tubes;

[0008] The driving module includes a mode determination unit, a sawtooth wave generation unit, and a driving signal output unit;

[0009] The mode determination unit determines the current working mode according to the input sampling voltage of the input voltage source, the output sampling voltage of the load resistor, and the preset hysteresis loop width;

[0010] The sawtooth wave generating unit generates a corresponding variable slope sawtooth wave input signal according to the current working mode selection;

[0011] The driving signal output unit outputs three driving signals to respectively control the conduction and switching actions of the three switching tubes when the inductor current passes through zero according to the sawtooth wave input signal, the output error voltage and the current working mode.

[0012] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the Buck-Boost conversion module includes: an input voltage source, a first switch tube, a second switch tube, a third switch tube, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, an output capacitor, an inductor, and a load resistor;

[0013] The first end of the input voltage source is connected to the input end of the first switch tube and the cathode of the third diode; the second end of the input voltage source is connected to the cathode of the fourth diode and the input end of the second switch tube; the output end of the first switch tube is connected to the anode of the first diode, the output end of the second switch tube is connected to the anode of the second diode, the cathode of the first diode and the cathode of the second diode are connected to the first end of the inductor, and the second end of the inductor is connected to the input end of the third switch tube and the anode of the fifth diode; the output capacitor is connected in parallel between the cathode of the fifth diode and the output end of the third switch tube; the load resistor is connected in parallel at both ends of the output capacitor; the output end of the third switch tube, the anode of the third diode, and the anode of the fourth diode are grounded; the control end of the first switch tube, the control end of the second switch tube, and the control end of the third switch tube are connected to the driving module.

[0014] As an optional solution, the Buck-Boost PFC converter further includes: an input differential sampling circuit and an output sampling circuit; the input differential sampling circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor; the output sampling circuit includes a fifth resistor and a sixth resistor;

[0015] The first end of the first resistor is connected to the first end of the input voltage source, the second end of the first resistor is grounded through the second resistor, the second end of the first resistor is connected to the non-inverting input end of the first operational amplifier, the second end of the input voltage source is connected to the first end of the third resistor, the second end of the third resistor is connected to the inverting input end of the first operational amplifier and the output end of the first operational amplifier, and the output end of the first operational amplifier serves as the output end of the input differential sampling circuit;

[0016] The fifth resistor and the sixth resistor are connected in series and then in parallel at both ends of the load resistor, and a common end of the fifth resistor and the sixth resistor serves as an output end of the output sampling circuit.

[0017] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the mode judgment unit includes: an absolute value circuit, a hysteresis width control circuit, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first comparator, a second comparator, a NOR gate, and a multiplexer;

[0018] The input end of the hysteresis width control circuit is connected to the output end of the output sampling circuit, and outputs an interval upper limit signal and an interval lower limit signal according to a preset hysteresis width upper limit and a preset hysteresis width lower limit; the interval lower limit signal output end of the hysteresis width control circuit is connected to the non-inverting input end of the first comparator through the seventh resistor, and the interval upper limit signal output end of the hysteresis width control circuit is connected to the inverting input end of the second comparator through the twelfth resistor;

[0019] The input end of the absolute value circuit is connected to the output end of the input differential sampling circuit, the output end of the absolute value circuit is connected to the inverting input end of the first comparator through the ninth resistor and to the non-inverting input end of the second comparator through the tenth resistor; the non-inverting input end of the first comparator is connected to the output end of the first comparator through the eighth resistor; the non-inverting input end of the second comparator is connected to the output end of the second comparator through the eleventh resistor; the output end of the first comparator and the output end of the second comparator are connected to the input end of the NOR gate; the output end of the first comparator is connected to the first input end of the multiplexer as a signal end of the Boost mode, the output end of the second comparator is connected to the second input end of the multiplexer as a signal end of the Buck mode, and the output end of the NOR gate is connected to the third input end of the multiplexer as a signal end of the Buck-Boost mode.

[0020] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the absolute value circuit includes: a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a sixth diode, a seventh diode, a second operational amplifier, and a third operational amplifier;

[0021] The output end of the input differential sampling circuit is connected to the first end of the thirteenth resistor, the second end of the thirteenth resistor is connected to the inverting input end of the second operational amplifier, the first end of the fourteenth resistor, and the first end of the seventeenth resistor, the non-inverting input end of the second operational amplifier is grounded, the second end of the fourteenth resistor is connected to the first end of the fifteenth resistor and the anode of the sixth diode, the second end of the seventeenth resistor is connected to the cathode of the seventh diode and the non-inverting input end of the third operational amplifier; the cathode of the sixth diode and the anode of the seventh diode are connected to the output end of the second operational amplifier, the second end of the fifteenth resistor is connected to the inverting input end of the third operational amplifier and the first end of the sixteenth resistor, the second end of the sixteenth resistor is connected to the output end of the third operational amplifier, and the output end of the third operational amplifier serves as the output end of the absolute value circuit.

[0022] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the drive signal output unit includes: a PWM drive control circuit and a drive signal generating circuit;

[0023] The PWM drive control circuit includes: a third comparator, a fourth operational amplifier, an SR trigger, a first capacitor, and an eighteenth resistor;

[0024] The output end of the output sampling circuit is connected to the inverting input end of the fourth operational amplifier, the non-inverting input end of the fourth operational amplifier is connected to the reference voltage signal, the inverting input end of the fourth operational amplifier is connected to the output end of the fourth operational amplifier through the first capacitor and the eighteenth resistor connected in series, the output end of the fourth operational amplifier is connected to the inverting input end of the third comparator, the non-inverting input end of the third comparator is connected to the output end of the multiplexer, the output end of the third comparator is connected to the reset end of the SR trigger, the set end of the SR trigger is connected to the zero-crossing signal output end of the inductor, and the Q output end of the SR trigger is connected to the input end of the drive signal generating circuit as the output end of the PWM drive control circuit.

[0025] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the drive signal generating circuit includes: a first NOT gate, a second NOT gate, a third NOT gate, a first OR gate, a second OR gate, a third OR gate, a first AND gate, a second AND gate, and a fourth comparator;

[0026] The output end of the second comparator is connected to the input end of the first NOT gate, the output end of the first comparator is connected to the input end of the second NOT gate and the first input end of the first OR gate, the output end of the first NOT gate is connected to the first input end of the first AND gate, the Q output end of the SR trigger is connected to the second input end of the first AND gate and the second input end of the second AND gate, the output end of the second NOT gate is connected to the first input end of the second AND gate, the output end of the second AND gate is connected to the second input end of the first OR gate, the output end of the first OR gate is connected to the first input end of the second OR gate and the first input end of the third OR gate, the non-inverting input end of the fourth comparator is connected to the output end of the input differential sampling circuit, the inverting input end of the fourth comparator is connected to the 0 signal end, the output end of the fourth comparator is connected to the input end of the third NOT gate and the second input end of the third OR gate, the output end of the third NOT gate is connected to the second input end of the second OR gate, the output end of the second OR gate is connected to the control end of the first switch tube, the output end of the third OR gate is connected to the control end of the second switch tube, and the output end of the first AND gate is connected to the control end of the third switch tube.

[0027] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the sawtooth wave generating unit includes: a Boost variable slope sawtooth wave generating circuit, a Buck-Boost variable slope sawtooth wave generating circuit, and a Buck variable slope sawtooth wave generating circuit;

[0028] The control ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are respectively connected to the inverting output end of the SR trigger to control the charging and discharging of the corresponding energy storage capacitor; the output ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are connected to the input end of the multiplexer.

[0029] As an optional solution, in the above-mentioned Buck-Boost PFC converter, the Boost variable slope sawtooth wave generating circuit includes: a first voltage-controlled current source, a second capacitor, a voltage source, and a fourth switch tube;

[0030] The control end of the fourth switch tube is connected to the inverting output end of the SR trigger, the first end of the fourth switch tube is connected to the first selection end of the multiplexer, the second end of the fourth switch tube is grounded, the first end of the fourth switch tube is connected to the first end of the first voltage-controlled current source and the first end of the second capacitor, the second end of the second capacitor is grounded, the positive electrode of the voltage source is connected to the second end of the first voltage-controlled current source, and the negative electrode of the voltage source is grounded;

[0031] The Buck-Boost variable slope sawtooth wave generating circuit comprises: a second voltage-controlled current source, a third capacitor, a voltage source, a fifth switch tube, a first multiplier, a first divider, and a first adder;

[0032] The control end of the fifth switch tube is connected to the inverting output end of the SR trigger, the first end of the fifth switch tube is connected to the second selection end of the multiplexer, the second end of the fifth switch tube is grounded, the first end of the fifth switch tube is connected to the output end of the second voltage-controlled current source and the first end of the third capacitor, and the second end of the third capacitor is grounded; the input end of the first adder is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit, the output end of the first adder and the output end of the output sampling circuit are connected to the input end of the first divider, the output end of the first divider and the positive electrode of the voltage source are connected to the input end of the first multiplier, the negative electrode of the voltage source is grounded, and the output end of the first multiplier is connected to the second end of the second voltage-controlled current source;

[0033] The Buck variable slope sawtooth wave generating circuit comprises: a third voltage-controlled current source, a fourth capacitor, a voltage source, a sixth switch tube, a second multiplier, a third multiplier, a second divider, and a first subtractor;

[0034] The control end of the sixth switch tube is connected to the inverting output end of the SR trigger, the first end of the sixth switch tube is connected to the third selection end of the multiplexer, the second end of the sixth switch tube is grounded, the first end of the sixth switch tube is connected to the output end of the third voltage-controlled current source and the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded;

[0035] The input end of the second divider is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit, the input end of the first subtractor is connected to the output end of the second divider and the 1-bit input end, the input end of the second multiplier is connected to the output end of the second divider and the output end of the first subtractor, the input end of the third multiplier is connected to the output end of the second multiplier and the positive electrode of the voltage source, the negative electrode of the voltage source is grounded, and the output end of the third multiplier is connected to the second end of the third voltage-controlled current source.

[0036] In order to solve the above technical problems, the present application also provides an electrical device, including the above Buck-Boost PFC converter.

[0037] The Buck-Boost PFC converter provided in the present application, the PFC conversion module includes three switch tubes, and the working modes of Boost mode, Buck-Boost mode and Buck mode are switched by controlling the conduction and switching action of the three switch tubes; the mode judgment unit determines the current working mode according to the input sampling voltage of the input voltage source, the output sampling voltage of the load resistor, and the preset hysteresis loop width; the sawtooth wave generating unit generates a corresponding variable slope sawtooth wave input signal according to the current working mode selection; the drive signal output unit outputs three drive signals to control the conduction and switching action of the three switch tubes respectively according to the sawtooth wave input signal and the output error voltage and the current working mode when the inductor current passes through zero. In the present application, the main switch tube at the Buck end is moved forward to the source side, and works symmetrically in the positive and negative half-power frequency cycles, which helps to reduce thermal stress and improve conversion efficiency; it can automatically switch between Boost, Buck-Boost and Buck modes according to system requirements, thereby improving the adaptability and reliability of the system. By real-time monitoring of the input and output voltages, the most suitable working mode can be judged, thereby improving the adaptability and efficiency of the system. The variable on-time control based on the variable slope sawtooth wave achieves unity power factor, improves the overall conversion efficiency of the converter, and achieves high power factor and low total harmonic distortion.

[0038] In addition, the present application also provides an electrical device corresponding to the above-mentioned Buck-Boost PFC converter, and has the same effect as above. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1A circuit diagram of a Buck-Boost type conversion module provided in an embodiment of the present application;

[0041] Figure 2 A circuit diagram of a mode determination unit and a drive signal output unit provided in an embodiment of the present application;

[0042] Figure 3 A circuit diagram of a sawtooth wave generating unit provided in an embodiment of the present application;

[0043] Figure 4 A schematic diagram of a working waveform in a positive half-power frequency cycle provided by an embodiment of the present application;

[0044] Figure 5 A schematic diagram of simulation results of a Buck-Boost PFC converter provided in an embodiment of the present application;

[0045] Figure 6 A schematic diagram of a mode switching simulation result of a Buck-Boost PFC converter provided in an embodiment of the present application;

[0046] The reference numerals are as follows: 11-Buck-Boost type conversion module; 12-absolute value circuit; 13-PWM drive control circuit; 14-drive signal generation circuit; 15-sawtooth wave generation unit. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0048] The core of this application is to provide a Buck-Boost PFC converter and electrical equipment.

[0049] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0050] With the development and application of power electronics technology, various nonlinear loads (such as switching power supplies, motor drivers, light-emitting diodes, etc.) are widely used in power systems, resulting in a significant increase in harmonic currents and reactive power in the power grid, which causes the grid current waveform to be distorted and the power factor to be reduced, thus causing a series of power quality problems. Through power factor correction (PFC) technology, the power factor of the equipment can be improved, the power loss can be reduced, and the overall energy efficiency of the system can be improved. The basic principle of the PFC converter is to use power electronic devices and control circuits to make the input current and input voltage in phase and maintain a sinusoidal waveform.

[0051] The boost PFC converter has become the most widely used topology for PFC circuits due to its advantages such as continuous input current and simple driving. It can obtain a high PF value in the entire input voltage range. The boost inductor is connected in series at the input end, the high-frequency input current ripple is small, and the structure is simple and the efficiency is high. However, due to topological limitations, the output voltage of the boost converter is higher than the input voltage peak, which causes a large voltage stress on the subsequent converter, increases the subsequent conversion rate, and reduces the conversion efficiency. The buck PFC converter can output at low voltage and has high power conversion efficiency, but the buck converter has an inherent dead zone near the zero crossing of the input voltage, the conversion efficiency is not high, and the input current harmonic distortion rate is high. The traditional buck-boost PFC converter can both boost and buck, and can achieve a higher power factor (PF) value. However, its output voltage is opposite to the polarity of the rectified voltage, and the output voltage needs to be additionally controlled; since there is no direct power transmission channel, the converter efficiency needs to be further improved. In addition to the advantages of the traditional Buck-Boost PFC converter, the dual-switch Buck-Boost PFC converter has the same output and input polarity, and the voltage stress when the circuit is turned on is also reduced. Therefore, it has received widespread attention.

[0052] The dual-switch Buck-Boost PFC converter generally adopts a bridge structure, and its input current is entirely borne by the main switch tube of the previous Buck unit. When the input voltage is low and the output is full-load, the current stress of the main switch tube of the Buck unit increases, and the heat dissipation problem needs to be considered in the design, which also brings difficulties to the layout. Since the quasi-Buck-Boost Buck-Boost PFC converter has two independently controlled switch tubes, it can have multiple working modes. Among them, the Boost and Buck modes are the most common working modes, but when the converter switches between modes, the input current is distorted, which significantly reduces the power factor value. In addition, in order to simplify the design, the current CRM Buck-Boost PFC converter generally adopts constant on-time (COT) control, which causes the input current in the Buck mode to be non-sinusoidal and the distortion is more serious. Therefore, it is necessary to improve the current mode switching method and control strategy to obtain a sinusoidal and smooth input current.

[0053] To solve the above problem, this embodiment provides a Buck-Boost PFC converter, including: a Buck-Boost conversion module 11 and a driving module.

[0054] The Buck-Boost conversion module 11 includes three switch tubes, and the operating modes of the Boost mode, Buck-Boost mode, and Buck mode are switched by controlling the conduction and switching actions of the three switch tubes.

[0055] The driving module includes a mode determination unit, a sawtooth wave generating unit 15 and a driving signal output unit.

[0056] The mode judgment unit is based on the input voltage source V in The current working mode is determined by the input sampling voltage, the output sampling voltage of the load resistor RL, and the preset hysteresis loop width.

[0057] The sawtooth wave generating unit 15 generates a corresponding variable slope sawtooth wave input signal according to the current working mode selection.

[0058] The driving signal output unit outputs three driving signals to respectively control the conduction and switching actions of the three switching tubes when the inductor current passes through zero according to the sawtooth wave input signal, the output error voltage and the current working mode.

[0059] Figure 1 A circuit diagram of a Buck-Boost type conversion module provided in an embodiment of the present application; Figure 2 A circuit diagram of a mode determination unit and a drive signal output unit provided in an embodiment of the present application; Figure 3 A circuit diagram of a sawtooth wave generating unit provided in an embodiment of the present application. Figure 1 , 2 As shown in Figures 3 and 4, in this embodiment, the Buck-Boost type conversion module 11 refers to a converter structure that does not include a traditional diode rectifier bridge, and can specifically realize the switching of the working modes of Boost mode, Buck-Boost mode, and Buck mode through the conduction and switching action of three switching tubes. The Buck, Buck-Boost, and Boost three-mode control is used to realize smooth switching of the input current, which helps to reduce the number of components, reduce costs, and improve efficiency and power factor.

[0060] The driving module refers to the circuit part that controls the conduction and switching action of the switch tube in the Buck-Boost type conversion module 11, which can be specifically composed of a mode judgment unit, a sawtooth wave generating unit 15, and a driving signal output unit, and is responsible for generating corresponding driving signals according to the working mode and system status.

[0061] The mode judgment unit determines the circuit part of the current working mode according to the sampling values ​​of the input voltage and the output voltage and the preset hysteresis loop width. This design can ensure that the converter automatically selects the most appropriate working mode according to the actual working conditions. For example, is the hysteresis width. Less than It is in Boost mode when the input voltage Greater than Buck mode, when the input voltage Greater than and less than The converter works in Buck-Boost mode.

[0062] The sawtooth wave generating unit 15 refers to the circuit part that selects the corresponding sawtooth wave input signal according to the current working mode, which can be specifically an oscillation circuit based on the capacitor charging and discharging principle. It selects the corresponding variable slope sawtooth wave input signal according to the current working mode to accurately control the conduction time of the switch tube.

[0063] The drive signal output unit outputs the drive signals of the three switch tubes according to the sawtooth wave input signal, the output error voltage and the current working mode, which can be specifically used to control the conduction and switching action of the three switch tubes to achieve the normal operation of the converter in different working modes. The inductor current zero crossing refers to the moment when the current in the inductor Lb drops to zero. Switching the switch tube at this moment can reduce energy loss.

[0064] Boost mode, Buck-Boost mode, and Buck mode are the three basic operating states of the converter, corresponding to different voltage conversion requirements and circuit operating modes.

[0065] In this solution, the connection relationship between the Buck-Boost type conversion module 11 and the driving module achieves the effect of automatically switching the working mode according to system requirements, thereby improving the flexibility and adaptability of the system.

[0066] The Buck-Boost PFC converter provided by the present application includes: a Buck-Boost conversion module 11 and a driving module; the Buck-Boost conversion module 11 includes three switch tubes, and the working mode switching between the Boost mode, the Buck-Boost mode, and the Buck mode is performed by controlling the conduction and switching action of the three switch tubes; the driving module includes a mode judgment unit, a sawtooth wave generating unit 15, and a driving signal output unit; the mode judgment unit generates a signal according to the input voltage source V in The input sampling voltage, the output sampling voltage of the load resistor RL, and the preset hysteresis loop width determine the current working mode; the sawtooth wave generating unit 15 generates a corresponding variable slope sawtooth wave input signal according to the current working mode selection; the drive signal output unit outputs three drive signals to control the conduction and switching action of the three switch tubes respectively when the inductor current passes through zero according to the sawtooth wave input signal, the output error voltage and the current working mode. In this application, the Buck-Boost type Buck end main switch tube is moved forward to the source side and works symmetrically in the positive and negative half-power frequency cycles, which helps to reduce thermal stress and improve conversion efficiency; it can automatically switch between Boost, Buck-Boost, and Buck modes according to system requirements, thereby improving the adaptability and reliability of the system. By real-time monitoring of the input and output voltages, the most suitable working mode is determined, thereby improving the adaptability and efficiency of the system. The variable conduction time control based on the variable slope sawtooth wave realizes the unity power factor, improves the overall conversion efficiency of the converter, and achieves high power factor and low total harmonic distortion.

[0067] According to the above embodiment, this embodiment provides a specific solution, the Buck-Boost type conversion module 11 includes: an input voltage source V in , a first switch tube S1, a second switch tube S2, a third switch tube S3, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, an output capacitor C0, an inductor Lb, and a load resistor RL.

[0068] Input voltage source V in The first end is connected to the input end of the first switch tube S1 and the cathode of the third diode D3; the input voltage source V inThe second end of is connected to the cathode of the fourth diode D4 and the input end of the second switch tube S2; the output end of the first switch tube S1 is connected to the anode of the first diode D1, the output end of the second switch tube S2 is connected to the anode of the second diode D2, the cathode of the first diode D1 and the cathode of the second diode D2 are connected to the first end of the inductor Lb, and the second end of the inductor Lb is connected to the input end of the third switch tube S3 and the anode of the fifth diode D5; the output capacitor C0 is connected in parallel between the cathode of the fifth diode D5 and the output end of the third switch tube S3; the load resistor RL is connected in parallel across the output capacitor C0; the output end of the third switch tube S3, the anode of the third diode D3, and the anode of the fourth diode D4 are grounded; the control end Vg_S1 of the first switch tube S1, the control end Vg_S2 of the second switch tube S2, and the control end Vg_S3 of the third switch tube S3 are connected to the driving module.

[0069] In this embodiment, the main switch tube of the front-stage Buck unit is split into two switch tubes with slightly smaller current stress, which are connected in series with the two diodes on the bridge arm of the rectifier bridge, and work symmetrically in the positive and negative half-power frequency cycles respectively. This is very helpful for the heat dissipation design of the input side switch tube and improves the overall conversion efficiency of the converter.

[0070] Input voltage source V in The AC voltage source U1 provides the power required by the converter and is the basis for the operation of the entire circuit. The first switch tube S1 and the second switch tube S2 serve as the main switch tubes of the Buck unit. The first diode D1 and the second diode D2 block the reverse flow of the inductor Lb current. The first switch tube S1 and the second switch tube S2 and the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 replace the traditional input rectifier bridge, making the converter a quasi-bridgeless structure.

[0071] Because the converter saves a freewheeling diode, the two bridge arms of the converter's front stage act as freewheeling paths. In the positive half-power frequency cycle, the second switch tube S2, the second diode D2, and the fourth diode D4 act as freewheeling paths. In the negative half-power frequency cycle, the first switch tube S1, the first diode D1, and the third diode D3 act as freewheeling channels. The fast recovery fifth diode D5 is the freewheeling diode of the Boost unit, and the energy storage inductor Lb is shared by the two units. The third switch tube S3 is the main switch tube of the Boost unit and is shared by the positive and negative half-power frequency cycles. The output capacitor C0 reduces the output voltage ripple and stabilizes the output voltage.

[0072] The load resistor RL simulates an actual load, such as an electrical device, which is connected across the output capacitor C0 to consume the electrical energy provided by the converter.

[0073] The control end of the switch tube receives control signals from the driving module, and is turned on and off according to these signals to achieve different working modes.

[0074] The main switch tube of the Buck-Boost type Buck end is moved forward to the source side, and works symmetrically in the positive and negative half-frequency cycles, which helps to reduce thermal stress and improve conversion efficiency. By accurately controlling the on-time of the switch tube, a power factor close to unity is achieved, reducing grid harmonics. It can adapt to different input voltage conditions and maintain stable output. Automatically switch the working mode according to the input voltage and load requirements, improving the adaptability and reliability of the system.

[0075] According to the above embodiment, this embodiment provides a specific solution, which also includes: an input differential sampling circuit and an output sampling circuit; the input differential sampling circuit includes a first operational amplifier amp1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; the output sampling circuit includes a fifth resistor R5 and a sixth resistor R6.

[0076] A first end of the first resistor R1 is connected to an input voltage source V in The first end of the first resistor R1 is connected to the first end of the operational amplifier amp1, the second end of the first resistor R1 is grounded through the second resistor R2, the second end of the first resistor R1 is connected to the non-inverting input terminal of the first operational amplifier amp1, the second end of the input voltage source is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the inverting input terminal of the first operational amplifier amp1 and the first end of the fourth resistor R4, the second end of the fourth resistor R4 is connected to the output terminal of the first operational amplifier amp1, and the output terminal of the first operational amplifier amp1 serves as the output terminal of the input differential sampling circuit.

[0077] The fifth resistor R5 and the sixth resistor R6 are connected in series and then in parallel to the two ends of the load resistor RL. The common end of the fifth resistor R5 and the sixth resistor R6 serves as the output end V of the output sampling circuit. F .

[0078] In this embodiment, the input differential sampling circuit and the output sampling circuit are added to realize real-time monitoring of the input and output voltages of the converter, thereby providing necessary feedback signals for the driving module. The first operational amplifier, the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 in the input differential sampling circuit constitute an input differential sampling circuit for sampling the input voltage source V in A lower voltage sample is obtained for subsequent signal processing and control circuit use. The output end of the first operational amplifier is used as the output of the sampling circuit and is provided to the mode determination unit as a sampled value of the input voltage.

[0079] The fifth resistor R5 and the sixth resistor R6 of the output sampling circuit are connected in series and then in parallel at both ends of the load resistor RL, and a voltage sample is obtained from both ends of the load without affecting the load current. The common end of the fifth resistor R5 and the sixth resistor R6 is used as the output of the sampling circuit and provided to the mode judgment unit as a sampled value of the output voltage.

[0080] Through the input and output sampling circuits, the control circuit can obtain accurate voltage feedback to achieve more precise control. Accurate sampling values ​​enable the mode judgment unit to correctly judge the current working mode, thereby controlling the switch tube to perform correct on and off actions, and achieving smooth switching between Boost, Buck-Boost, and Buck modes.

[0081] According to the above embodiments, this embodiment provides a specific solution, and the mode judgment unit includes: an absolute value circuit 12, a hysteresis width control circuit, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a first comparator comp1, a second comparator comp2, a NOR gate nor, and a multiplexer MUX.

[0082] The input end of the hysteresis width control circuit is connected to the output end of the output sampling circuit, and outputs an interval upper limit signal and an interval lower limit signal according to a preset hysteresis width upper limit and a preset hysteresis width lower limit; the interval lower limit signal output end of the hysteresis width control circuit is connected to the non-inverting input end of the first comparator comp1 through the seventh resistor R7, and the interval upper limit signal output end of the hysteresis width control circuit is connected to the inverting input end of the second comparator comp2 through the twelfth resistor R12.

[0083] The input end of the absolute value circuit 12 is connected to the output end of the input differential sampling circuit, and the output end of the absolute value circuit 12 is connected to the inverting input end of the first comparator comp1 through the ninth resistor R9 and to the non-inverting input end of the second comparator comp2 through the tenth resistor R10; the non-inverting input end of the first comparator comp1 is connected to the output end of the first comparator comp1 through the eighth resistor R8; the non-inverting input end of the second comparator comp2 is connected to the output end of the second comparator comp2 through the eleventh resistor R11; the output end of the first comparator comp1 and the output end of the second comparator comp2 are connected to the input end of the NOR gate nor; the output end of the first comparator comp1 is connected to the first input end of the multiplexer MUX as a signal end of the Boost mode, the output end of the second comparator comp2 is connected to the second input end of the multiplexer MUX as a signal end of the Buck mode, and the output end of the NOR gate nor is connected to the third input end of the multiplexer MUX as a signal end of the Buck-Boost mode.

[0084] The mode judgment unit is designed to accurately judge the working mode of the converter, thereby achieving precise control of the switch tube.

[0085] In this embodiment, the hysteresis width control circuit is responsible for receiving the output signal of the output sampling circuit, and outputting the interval upper limit signal and the interval lower limit signal according to the preset hysteresis width upper limit and lower limit. These signals are used to compare with the output of the absolute value circuit 12 to determine the current working mode.

[0086] The first comparator comp1 and the second comparator comp2 are used to compare the interval signal output by the hysteresis width control circuit with the output of the absolute value circuit 12 to determine the current working mode.

[0087] The absolute value of the input voltage and the hysteresis range of the output voltage The first comparator comp1 and the second comparator comp2 are used for comparison. is the hysteresis width, the negative input terminal of the first comparator comp1 is the sampling input voltage , the positive input terminal is , when the input voltage Less than When the output of the first comparator comp1 is high, that is, Boost mode, the positive input terminal of the second comparator comp2 is the input voltage , the negative input terminal is , when the input voltage Greater than When the first comparator comp1 outputs a high level, it is the Buck mode. Greater than and less than When , the converter works in Buck-Boost mode. Therefore, the outputs of the first comparator comp1 and the second comparator comp2 can obtain Buck-Boost mode signals through the NOR gate nornor.

[0088] The output of the first comparator comp1 is used as the signal terminal of the Boost mode, the output of the second comparator comp2 is used as the signal terminal of the Buck mode, and the output of the NOR gate nor is used as the signal terminal of the Buck-Boost mode. These signals are selected by the multiplexer MUX to achieve precise control of the converter working mode.

[0089] The working mode of the converter can be accurately determined by the precise comparison between the hysteresis width control circuit and the comparator. The multiplexer MUX selects the corresponding working mode signal according to the comparison result to achieve smooth switching of the converter between different modes. Accurate working mode control helps to improve the stability and efficiency of the entire converter system.

[0090] According to the above embodiment, this embodiment provides a specific solution, the absolute value circuit 12 includes: a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a sixth diode D6, a seventh diode D7, a second operational amplifier amp2, and a third operational amplifier amp3.

[0091] The output end of the input differential sampling circuit is connected to the first end of the thirteenth resistor R13, the second end of the thirteenth resistor R13 is connected to the inverting input end of the second operational amplifier amp2, the first end of the fourteenth resistor R14, and the first end of the seventeenth resistor R17, the non-inverting input end of the second operational amplifier amp2 is grounded, the second end of the fourteenth resistor R14 is connected to the first end of the fifteenth resistor R15 and the anode of the sixth diode D6, the second end of the seventeenth resistor R17 is connected to the cathode of the seventh diode D7 and the non-inverting input end of the third operational amplifier amp3; the cathode of the sixth diode D6 and the anode of the seventh diode D7 are connected to the output end of the second operational amplifier amp2, the second end of the fifteenth resistor R15 is connected to the inverting input end of the third operational amplifier amp3 and the first end of the sixteenth resistor R16, the second end of the sixteenth resistor R16 is connected to the output end of the third operational amplifier amp3, and the output end of the third operational amplifier amp3 serves as the output end of the absolute value circuit 12.

[0092] In the mode judgment unit, since there is no rectifier bridge, the input voltage V in It has two half-cycles, positive and negative, so when comparing the input and output voltages, the input voltage V in the positive half cycle should be sampled. in , which requires the input voltage to be obtained after passing through the absolute value circuit 12. The sixth diode D6, the seventh diode D7, the second operational amplifier amp2, and the third operational amplifier amp3 constitute the absolute value circuit 12. When the input voltage is positive, the sixth diode D6 is turned on, the seventh diode D7 is not turned on, and the output of the third operational amplifier amp3 is in the same direction as the input voltage. On the contrary, when the input voltage is negative, the sixth diode D6 is not turned on, the seventh diode D7 is turned on, and the output of the third operational amplifier amp3 is opposite to the input voltage. Therefore, the output of the second operational amplifier amp2 is the absolute value of the input voltage.

[0093] The mode determination unit can more accurately determine the current working mode through the accurate input voltage value provided by the absolute value circuit 12. Accurate working mode determination helps to improve the stability and efficiency of the entire converter system.

[0094] According to the above embodiment, this embodiment provides a specific solution, in which the driving signal output unit includes: a PWM driving control circuit 13 and a driving signal generating circuit 14 .

[0095] The PWM driving control circuit 13 includes: a third comparator comp3, a fourth operational amplifier amp4, an SR trigger, a first capacitor C1, and an eighteenth resistor R18.

[0096] The output end of the output sampling circuit is connected to the inverting input end of the fourth operational amplifier amp4, the non-inverting input end of the fourth operational amplifier amp4 is connected to the reference voltage signal, the inverting input end of the fourth operational amplifier amp4 is connected to the output end of the fourth operational amplifier amp4 through the first capacitor C1 and the eighteenth resistor R18 connected in series, the output end of the fourth operational amplifier amp4 is connected to the inverting input end of the third comparator comp3, the non-inverting input end of the third comparator comp3 is connected to the output end of the multiplexer MUX, the output end of the third comparator comp3 is connected to the reset end of the SR trigger, the set end of the SR trigger is connected to the zero-crossing signal output end of the inductor Lb, and the Q output end of the SR trigger is connected to the input end of the drive signal generating circuit 14 as the output end of the PWM drive control circuit 13.

[0097] The pulse width modulation (PWM) drive control circuit 13 is used to generate a PWM drive signal. The drive signal generation circuit 14 receives the signal from the PWM drive control circuit 13 and generates a drive signal that ultimately controls the three switch tubes. The SR trigger (reset / set trigger, R and S are the abbreviations of reset and set respectively) has two stable states, 1 and 0, respectively, and is called a bistable trigger. If there is no external trigger signal, it will maintain its original state unchanged, and the trigger has a memory function. Under the action of an external trigger signal, the output state of the trigger may change, and the output state is directly controlled by the input signal.

[0098] The output terminal of the output sampling circuit is connected to the inverting input terminal of the fourth operational amplifier amp4, and is used to introduce the output voltage sampling value into the PWM drive control circuit 13. ref After passing through the output voltage compensation circuit composed of the first capacitor C1, the eighteenth resistor R18 and the fourth operational amplifier amp4, the error voltage U is output. comp , error voltage U comp The three-mode variable slope sawtooth wave U connected to the inverting input terminal of the third comparator comp3 and the non-inverting input terminal saw For comparison, the output result is connected to the reset terminal R of the SR trigger, and the set terminal S of the SR trigger is connected to the inductor current zero-crossing detection signal terminal: ZCD signal terminal (such as Figure 1As shown in the figure, the ZCD signal terminal is connected to the inductor Lb through the resistor Rzcd, and the resistor Rzcd serves as a current limiting resistor. When the inductor current passes through zero, the ZCD signal terminal outputs a high level, and the output of the SR trigger Q terminal is a PWM pulse signal. Since the Buck-Boost type Buck-Boost PFC converter operates in three modes, the signal also needs to be combined with the mode judgment to pass through the drive signal generation circuit 14 to obtain the drive signals of the three switch tubes respectively.

[0099] By using the zero-crossing signal of the SR trigger and the inductor Lb, the drive signal is quickly responded and generated to improve the dynamic performance of the system. The switch tube is switched when the inductor current passes through zero, reducing switching losses and improving efficiency.

[0100] According to the above embodiment, this embodiment provides a specific solution, and the drive signal generating circuit 14 includes: a first NOT gate not1, a second NOT gate not2, a third NOT gate not3, a first OR gate OR1, a second OR gate OR2, a third OR gate OR3, a first AND gate and1, a second AND gate and2, and a fourth comparator comp4.

[0101] The output end of the second comparator comp2 is connected to the input end of the first NOT gate not1, the output end of the first comparator comp1 is connected to the input end of the second NOT gate not2 and the first input end of the first OR gate OR1, the output end of the first NOT gate not1 is connected to the first input end of the first AND gate and1, the Q output end of the SR flip-flop is connected to the second input end of the first AND gate and1 and the second input end of the second AND gate and2, the output end of the second NOT gate not2 is connected to the first input end of the second AND gate and2, the output end of the second AND gate and2 is connected to the second input end of the first OR gate OR1, and the output end of the first OR gate OR1 is connected to the first input end of the second OR gate OR2 The input terminal of the fourth comparator comp4 is connected to the output terminal of the input differential sampling circuit, the inverting input terminal of the fourth comparator comp4 is connected to the 0 signal terminal, the output terminal of the fourth comparator comp4 is connected to the input terminal of the third NOT gate not3 and the second input terminal of the third OR gate OR3, the output terminal of the third NOT gate not3 is connected to the second input terminal of the second OR gate OR2, the output terminal of the second OR gate OR2 is connected to the control terminal of the first switch tube S1, the output terminal of the third OR gate OR3 is connected to the control terminal of the second switch tube S2, and the output terminal of the first AND gate and1 is connected to the control terminal of the third switch tube S3.

[0102] The NOT gate is used to invert a logic signal. The OR gate is used to combine multiple logic signals so that the output is high when any one of the inputs is high. The AND gate is used to combine multiple logic signals so that the output is high only when all inputs are high.

[0103] In the positive half-power frequency cycle, the second switch tube S2 is always turned on as a freewheeling switch, and the first switch tube S1 is used as the main switch tube to perform switching action; in the negative half-power frequency cycle, on the contrary, the first switch tube S1 is turned on, and the second switch tube S2 performs switching action. The driving signals when the first switch tube S1 and the second switch tube S2 are used as the main switch tubes are the same, so only the working conditions of the switches in the positive half-power frequency cycle are discussed. In the Boost mode, the first switch tube S1 is always turned on, and the third switch tube S3 performs switching action; in the Buck-Boost mode, the first switch tube S1 and the third switch tube S3 maintain synchronous action; in the Buck mode, the first switch tube S1 performs switching action, and the third switch tube S3 remains disconnected.

[0104] In these three modes, the inductor Lb current i Lb When the switch tube is turned on, it starts to rise from zero, and the inductor Lb stores energy; when the positive input signal U saw Greater than the negative input signal U comp When the SR trigger is reset, the switch tube is disconnected, and the inductor Lb current drops to 0, the ZCD signal terminal is triggered to start the next cycle. Therefore, the Boost signal is inverted through the second NOT gate not2 and then combined with the PWM pulse signal as the input of the first AND gate and1. After the output result and the Boost signal pass through the first OR gate OR1, the driving signals of the first switch tube S1 and the second switch tube S2 need to be output respectively according to the positive and negative of the input voltage. in_sen After the AND0 signal passes through the fourth comparator comp4, it is combined with the output of the first OR gate OR1 and then passes through the third OR gate OR3 to output the driving signal of the second switch tube S2. The output of the fourth comparator comp4 is inverted and then combined with the output of the first OR gate OR1 through the second OR gate OR2 to obtain the driving signal of the second switch tube S2. The driving signal of the third switch tube S3 is obtained by combining the Buck signal with the PWM pulse signal through the second AND gate and2 after being inverted through the first NOT gate not1.

[0105] This embodiment utilizes a logic gate circuit to combine various mode signals and state signals to generate a driving signal that meets specific conditions.

[0106] According to the above embodiments, this embodiment provides a specific solution, the sawtooth wave generating unit 15 includes: a Boost variable slope sawtooth wave generating circuit, a Buck-Boost variable slope sawtooth wave generating circuit, and a Buck variable slope sawtooth wave generating circuit.

[0107] The control ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are respectively connected to the inverting output end of the SR trigger to control the charging and discharging of the corresponding energy storage capacitor; the output ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are connected to the input end of the multiplexer MUX.

[0108] The sawtooth wave generating unit 15 is designed to generate variable slope sawtooth waves in different modes, which are used to control the on-time of the switch tube, thereby achieving precise control of the output voltage of the converter. The Boost variable slope sawtooth wave generating circuit is used to generate a variable slope sawtooth wave in the Boost mode and control the on-time of the switch tube in the Boost mode. The Buck-Boost variable slope sawtooth wave generating circuit is used to generate a variable slope sawtooth wave in the Buck-Boost mode and control the on-time of the switch tube in the Buck-Boost mode. The Buck variable slope sawtooth wave generating circuit is used to generate a variable slope sawtooth wave in the Buck mode and control the on-time of the switch tube in the Buck mode.

[0109] The inverting output terminal of the SR trigger is connected to the control terminals of three variable slope sawtooth wave generating circuits, and is used to control the charging and discharging of the corresponding energy storage capacitor according to the output state of the SR trigger, thereby controlling the slope of the sawtooth wave.

[0110] The multiplexer MUX is used to select the output of the corresponding variable slope sawtooth wave generating circuit according to the current working mode as the reference signal of the PWM drive control circuit 13.

[0111] When switching between different working modes, by changing the slope of the sawtooth wave, smooth mode switching can be achieved and output voltage fluctuations can be reduced.

[0112] According to the above embodiment, this embodiment provides a specific solution, such as Figure 3 As shown, the Boost variable slope sawtooth wave generating circuit includes: a first voltage-controlled current source i VCCS1 , a second capacitor C2, a voltage source U1, and a fourth switch tube S4.

[0113] The control end of the fourth switch tube S4 is connected to the inverting output end of the SR trigger, the first end of the fourth switch tube S4 is connected to the first selection end of the multiplexer MUX, the second end of the fourth switch tube S4 is grounded, and the first end of the fourth switch tube S4 is connected to the first voltage-controlled current source i VCCS1 The first end of the voltage source U1 and the first end of the second capacitor C2 are connected, the second end of the second capacitor C2 is grounded, and the positive electrode of the voltage source U1 is connected to the first voltage-controlled current source i VCCS1The second end of the voltage source U1 is connected to the ground, and the negative electrode of the voltage source U1 is grounded.

[0114] The Buck-Boost variable slope sawtooth wave generating circuit comprises: a second voltage-controlled current source i VCCS2 , a third capacitor C3, a voltage source U1, a fifth switch tube S5, a first multiplier Multiplier1, a first divider divider1, and a first adder Adder.

[0115] The control end of the fifth switch tube S5 is connected to the inverting output end of the SR trigger, the first end of the fifth switch tube S5 is connected to the second selection end of the multiplexer MUX, the second end of the fifth switch tube S5 is grounded, and the first end of the fifth switch tube S5 is connected to the second voltage-controlled current source i VCCS2 The output end of the first adder Adder is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit, the output end of the first adder Adder and the output end of the output sampling circuit are connected to the input end of the first divider divider1, the output end of the first divider divider1 and the positive electrode of the voltage source U1 are connected to the input end of the first multiplier Multiplier1, the negative electrode of the voltage source U1 is grounded, and the output end of the first multiplier Multiplier1 is connected to the second voltage-controlled current source i VCCS2 The second end of the connection.

[0116] The Buck variable slope sawtooth wave generating circuit comprises: a third voltage-controlled current source i VCCS3 , a fourth capacitor C4, a voltage source U1, a sixth switch tube S6, a second multiplier Multiplier2, a third multiplier Multiplier3, a second divider divider2, and a first subtractor Subtractor.

[0117] The control end of the sixth switch tube S6 is connected to the inverting output end of the SR trigger, the first end of the sixth switch tube S6 is connected to the third selection end of the multiplexer MUX, the second end of the sixth switch tube S6 is grounded, and the first end of the sixth switch tube S6 is connected to the third voltage-controlled current source i VCCS3 The output end of the capacitor C4 and the first end of the fourth capacitor C4 are connected, and the second end of the fourth capacitor C4 is grounded.

[0118] The input end of the second divider divider2 is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit. The input end of the first subtractor Subtractor is connected to the output end of the second divider divider2 and the 1-bit input end (i.e. Figure 3The input end of the second multiplier Multiplier2 is connected to the output end of the second divider divider2 and the output end of the first subtractor Subtractor, the input end of the third multiplier Multiplier3 is connected to the output end of the second multiplier Multiplier2 and the positive electrode of the voltage source U1, the negative electrode of the voltage source U1 is grounded, and the output end of the third multiplier Multiplier3 is connected to the third voltage-controlled current source i VCCS3 The second end of the connection.

[0119] Boost variable slope sawtooth wave generating circuit, the first voltage-controlled current source i VCCS1 The current output is adjusted according to the control signal, affecting the charging rate of the second capacitor C2, thereby changing the slope of the sawtooth wave. The second capacitor C2 is used as an energy storage element, and its charging and discharging process generates a sawtooth waveform. The voltage source U1 provides a stable reference voltage. The fourth switch tube S4 controls the charging and discharging process of the second capacitor C2, and its conduction and shutdown are controlled by the inverting output terminal of the SR trigger. Figure 3 Where saw_Boost represents the Boost variable slope sawtooth wave output control signal.

[0120] Buck-Boost variable slope sawtooth wave generating circuit, the second voltage-controlled current source i VCCS2 Similar to the Boost mode, it has the same function as the second capacitor C2, but is used in the Buck-Boost mode. The fifth switch tube S5 controls the charging and discharging process of the third capacitor C3, and its on and off are also controlled by the inverting output terminal of the SR trigger. The first multiplier Multiplier1, the first divider divider1, and the first adder Adder are used to dynamically adjust the second voltage-controlled current source i according to the input and output sampling signals. VCCS2 The control voltage adjusts the sawtooth wave slope. Figure 3 Where saw_Buck-Boost represents the Buck-Boost variable slope sawtooth wave output control signal.

[0121] Buck variable slope sawtooth wave generating circuit, the third voltage-controlled current source i VCCS3 Provide specific current-voltage characteristics for Buck mode. The fourth capacitor C4 has the same function as the second and third capacitors C3 and is used in Buck mode. The sixth switch tube S6 controls the charging and discharging process of the fourth capacitor C4, and its on and off are controlled by the inverting output terminal of the SR trigger. The second multiplier Multiplier2, the third multiplier Multiplier3, the second divider divider2, and the first subtractor Subtractor are used to dynamically adjust the third voltage-controlled current source i according to the input and output sampling signals and the fixed reference value. VCCS3 The control voltage can achieve precise sawtooth wave slope control. Figure 3 Where saw_Buck represents the Buck variable slope sawtooth wave output control signal. Figure 3 u c2 、u c3 、u c4 Respectively represent the voltages of capacitors C2, C3, and C4. i1 represents the first voltage-controlled current source i VCCS1 , the second voltage-controlled current source i VCCS2 , the third voltage-controlled current source i VCCS3 of output current.

[0122] According to the differences of the three modes, the three-mode variable slope sawtooth wave generating circuit is also different. Taking the Boost mode as an example, its variable slope sawtooth wave generating circuit is composed of a voltage source U1, a voltage-controlled current source, a second capacitor C2 and a fourth switch tube S4. The control terminal input of the fourth switch tube S4 is connected to the inverting output terminal of the SR trigger. The fourth switch tube S4 is controlled to control the charging and discharging of the second capacitor C2. When the converter switch tube is turned on, the fourth switch tube S4 is turned off, and the voltage-controlled current source iVCCS charges the second capacitor C2. The sawtooth wave U saw Increase, increase to the error voltage U comp When the switch tube is turned off, the fourth switch tube S4 is turned on, the second capacitor C2 is grounded, and the sawtooth wave U saw The slope of the variable slope sawtooth wave U is controlled by the on-time and switching period of the PWM pulse signal. saw Unlike the Boost mode, the voltage of the variable slope sawtooth generator in the Buck-boost and Buck modes is not just the voltage source U1. In order to achieve unity power factor, a multiplier, a divider, an adder, and a sampled input and output voltage are also required.

[0123] Charging current in Boost mode for: .

[0124] Charging current in buck-boost mode for:

[0125] .

[0126] Buck mode charging current for: .

[0127] Therefore, the switch on-time in each mode can be obtained (the on-time in Boost mode , Buck-boost mode on-time , On-time in Buck mode ) are:

[0128] .

[0129] .

[0130] .

[0131] If the charging capacitor value of the sawtooth generator in each mode is C, the input current formula of the three modes of the converter will remain consistent, that is:

[0132] .

[0133] In the above formula, Indicates the sampling input voltage, V m Indicates the AC voltage amplitude; Indicates the sampled output voltage; Indicates the size of the charging capacitor (the second capacitor C2, the third capacitor C3, or the fourth capacitor C4), which is distinguished by the subscripts 2, 3, and 4; u c3 、u c4 Respectively represent the voltage magnitudes of capacitors C3 and C4; The error voltage U at the output of the third operational amplifier amp3 is comp The size of the signal; Indicates the size of the voltage source U1; represents the size of the inductor Lb; i1 represents the output current of the voltage-controlled current source; It represents the control coefficient of the voltage-controlled current source. From the above formula, it can be seen that the input current is pure sinusoidal and can achieve unity power factor.

[0134] The sawtooth waves in three modes generated by the variable slope sawtooth wave generator are connected to the three selection channels of the multiplexer MUX. The multiplexer MUX has eight input and three output channels. The eight input channels of the multiplexer MUX are connected to the three mode signals of Boost, Buck-Boost and Buck respectively. The output of the multiplexer MUX is the variable slope sawtooth wave signal. Therefore, when the converter works in the three modes, the corresponding variable slope sawtooth wave will be generated. Then the output of the multiplexer MUX is connected to the negative input terminal of the third comparator comp3 of the comparator and the error voltage U comp Make a comparison.

[0135] Figure 4 A schematic diagram of a working waveform in a positive half-power frequency cycle provided by an embodiment of the present application; Figure 4 As shown, in_avg represents the average input current, i inrepresents the input current, Vgs_S1, Vgs_S2, and Vgs_S3 represent the switch pulse signals of switches S1, S2, and S3 respectively. In the positive half-power frequency cycle, the second switch tube S2 is kept on as a freewheeling switch, and the first switch tube S1 is switched as the main switch tube; Figure 5 A schematic diagram of simulation results of a Buck-Boost PFC converter provided in an embodiment of the present application; Figure 5 Indicates the changes of each signal over time; the vertical coordinates are V in Represents the voltage change of the input voltage source; V o Indicates the voltage change of the sampled output voltage; i in Represents the current change of the input current; i Lb Indicates the change in the current of the inductor Lb; the horizontal axis corresponds to the time signal t.

[0136] Figure 6 A schematic diagram of mode switching simulation results of a Buck-Boost PFC converter provided in an embodiment of the present application. Figure 6 The vertical coordinate dir1 represents the change of the S1 drive signal; dir2 represents the change of the S2 drive signal; i Lb Indicates the change in the current of the inductor Lb; the horizontal axis corresponds to the time signal t.

[0137] The simulation results of the Buck-Boost PFC converter are as follows: Figure 5 , Figure 6 As shown in the figure, the input current waveform of the converter under VOT control realized by variable slope sawtooth wave is almost ideal, which can achieve unity power factor, and the output voltage ripple is also within the standard range. The converter works in critical conduction mode and can smoothly switch modes to realize buck-boost function.

[0138] Finally, this embodiment provides an electrical device, including the above-mentioned Buck-Boost PFC converter.

[0139] The Buck-Boost PFC converter and electrical equipment provided by the present application are introduced in detail above. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0140] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A Buck-Boost PFC converter, characterized in that: include: Buck-Boost conversion module and driver module; The Buck-Boost conversion module includes three switch tubes, and the operating modes of the Boost mode, Buck-Boost mode and Buck mode are switched by controlling the conduction and switching actions of the three switch tubes; The driving module includes a mode determination unit, a sawtooth wave generation unit, and a driving signal output unit; The mode determination unit determines the current working mode according to the input sampling voltage of the input voltage source, the output sampling voltage of the load resistor, and the preset hysteresis loop width; The sawtooth wave generating unit generates a corresponding variable slope sawtooth wave input signal according to the current working mode selection; The drive signal output unit outputs three drive signals to respectively control the conduction and switching actions of the three switch tubes when the inductor current passes through zero according to the sawtooth wave input signal, the output error voltage and the current working mode; The Buck-Boost conversion module includes: an input voltage source, a first switch tube, a second switch tube, a third switch tube, a first diode, a second diode, a third diode, a fourth diode, a fifth diode, an output capacitor, an inductor, and a load resistor; The first end of the input voltage source is connected to the input end of the first switch tube and the cathode of the third diode; the second end of the input voltage source is connected to the cathode of the fourth diode and the input end of the second switch tube; the output end of the first switch tube is connected to the anode of the first diode, the output end of the second switch tube is connected to the anode of the second diode, the cathode of the first diode and the cathode of the second diode are connected to the first end of the inductor, and the second end of the inductor is connected to the input end of the third switch tube and the anode of the fifth diode; the output capacitor is connected in parallel between the cathode of the fifth diode and the output end of the third switch tube; the load resistor is connected in parallel at both ends of the output capacitor; the output end of the third switch tube, the anode of the third diode and the anode of the fourth diode are grounded; the control end of the first switch tube, the control end of the second switch tube and the control end of the third switch tube are connected to the driving module; It also includes: an input differential sampling circuit and an output sampling circuit; the input end of the input differential sampling circuit is connected to the input voltage source, and the input end of the output sampling circuit is connected to the load resistor; The mode determination unit includes: an absolute value circuit, a hysteresis width control circuit, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a first comparator, a second comparator, a NOR gate, and a multiplexer; The input end of the hysteresis width control circuit is connected to the output end of the output sampling circuit, and outputs an interval upper limit signal and an interval lower limit signal according to a preset hysteresis width upper limit and a preset hysteresis width lower limit; the interval lower limit signal output end of the hysteresis width control circuit is connected to the non-inverting input end of the first comparator through the seventh resistor, and the interval upper limit signal output end of the hysteresis width control circuit is connected to the inverting input end of the second comparator through the twelfth resistor; The input end of the absolute value circuit is connected to the output end of the input differential sampling circuit, the output end of the absolute value circuit is connected to the inverting input end of the first comparator through the ninth resistor and to the non-inverting input end of the second comparator through the tenth resistor; the non-inverting input end of the first comparator is connected to the output end of the first comparator through the eighth resistor; the non-inverting input end of the second comparator is connected to the output end of the second comparator through the eleventh resistor; the output end of the first comparator and the output end of the second comparator are respectively connected to the input end of the NOR gate; the output end of the first comparator is connected to the first input end of the multiplexer as a signal end of the Boost mode, the output end of the second comparator is connected to the second input end of the multiplexer as a signal end of the Buck mode, and the output end of the NOR gate is connected to the third input end of the multiplexer as a signal end of the Buck-Boost mode.

2. The Buck-Boost PFC converter according to claim 1, characterized in that: The input differential sampling circuit includes a first operational amplifier, a first resistor, a second resistor, a third resistor, and a fourth resistor; the output sampling circuit includes a fifth resistor and a sixth resistor; The first end of the first resistor is connected to the first end of the input voltage source, the second end of the first resistor is grounded through the second resistor, the second end of the first resistor is connected to the non-inverting input end of the first operational amplifier, the second end of the input voltage source is connected to the first end of the third resistor, the second end of the third resistor is connected to the inverting input end of the first operational amplifier and the first end of the fourth resistor, the second end of the fourth resistor is connected to the output end of the first operational amplifier, and the output end of the first operational amplifier serves as the output end of the input differential sampling circuit; The fifth resistor and the sixth resistor are connected in series and then in parallel at both ends of the load resistor, and a common end of the fifth resistor and the sixth resistor serves as an output end of the output sampling circuit.

3. The Buck-Boost PFC converter according to claim 1, characterized in that: The absolute value circuit comprises: a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a sixth diode, a seventh diode, a second operational amplifier, and a third operational amplifier; The output end of the input differential sampling circuit is connected to the first end of the thirteenth resistor, the second end of the thirteenth resistor is connected to the inverting input end of the second operational amplifier, the first end of the fourteenth resistor, and the first end of the seventeenth resistor, the non-inverting input end of the second operational amplifier is grounded, the second end of the fourteenth resistor is connected to the first end of the fifteenth resistor and the anode of the sixth diode, the second end of the seventeenth resistor is connected to the cathode of the seventh diode and the non-inverting input end of the third operational amplifier; the cathode of the sixth diode and the anode of the seventh diode are connected to the output end of the second operational amplifier, the second end of the fifteenth resistor is connected to the inverting input end of the third operational amplifier and the first end of the sixteenth resistor, the second end of the sixteenth resistor is connected to the output end of the third operational amplifier, and the output end of the third operational amplifier serves as the output end of the absolute value circuit.

4. The Buck-Boost PFC converter according to claim 3, characterized in that: The driving signal output unit includes: a PWM driving control circuit and a driving signal generating circuit; The PWM drive control circuit includes: a third comparator, a fourth operational amplifier, an SR trigger, a first capacitor, and an eighteenth resistor; The output end of the output sampling circuit is connected to the inverting input end of the fourth operational amplifier, the non-inverting input end of the fourth operational amplifier is connected to the reference voltage signal, the inverting input end of the fourth operational amplifier is connected to the output end of the fourth operational amplifier through the first capacitor and the eighteenth resistor connected in series, the output end of the fourth operational amplifier is connected to the inverting input end of the third comparator, the non-inverting input end of the third comparator is connected to the output end of the multiplexer, the output end of the third comparator is connected to the reset end of the SR trigger, the set end of the SR trigger is connected to the zero-crossing signal output end of the inductor, and the Q output end of the SR trigger is connected to the input end of the drive signal generating circuit as the output end of the PWM drive control circuit.

5. The Buck-Boost PFC converter according to claim 4, characterized in that: The driving signal generating circuit comprises: a first NOT gate, a second NOT gate, a third NOT gate, a first OR gate, a second OR gate, a third OR gate, a first AND gate, a second AND gate, and a fourth comparator; The output end of the second comparator is connected to the input end of the first NOT gate, the output end of the first comparator is connected to the input end of the second NOT gate and the first input end of the first OR gate, the output end of the first NOT gate is connected to the first input end of the first AND gate, the Q output end of the SR trigger is connected to the second input end of the first AND gate and the second input end of the second AND gate, the output end of the second NOT gate is connected to the first input end of the second AND gate, the output end of the second AND gate is connected to the second input end of the first OR gate, the output end of the first OR gate is connected to the first input end of the second OR gate and the first input end of the third OR gate, the non-inverting input end of the fourth comparator is connected to the output end of the input differential sampling circuit, the inverting input end of the fourth comparator is connected to the 0 signal end, the output end of the fourth comparator is connected to the input end of the third NOT gate and the second input end of the third OR gate, the output end of the third NOT gate is connected to the second input end of the second OR gate, the output end of the second OR gate is connected to the control end of the first switch tube, the output end of the third OR gate is connected to the control end of the second switch tube, and the output end of the first AND gate is connected to the control end of the third switch tube.

6. The Buck-Boost PFC converter according to claim 4, characterized in that: The sawtooth wave generating unit comprises: a Boost variable slope sawtooth wave generating circuit, a Buck-Boost variable slope sawtooth wave generating circuit, and a Buck variable slope sawtooth wave generating circuit; The control ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are respectively connected to the inverting output end of the SR trigger to control the charging and discharging of the corresponding energy storage capacitor; the output ends of the Boost variable slope sawtooth wave generating circuit, the Buck-Boost variable slope sawtooth wave generating circuit, and the Buck variable slope sawtooth wave generating circuit are connected to the input end of the multiplexer.

7. The Buck-Boost PFC converter according to claim 6, characterized in that: The Boost variable slope sawtooth wave generating circuit comprises: a first voltage-controlled current source, a second capacitor, a voltage source, and a fourth switch tube; The control end of the fourth switch tube is connected to the inverting output end of the SR trigger, the first end of the fourth switch tube is connected to the first selection end of the multiplexer, the second end of the fourth switch tube is grounded, the first end of the fourth switch tube is connected to the first end of the first voltage-controlled current source and the first end of the second capacitor, the second end of the second capacitor is grounded, the positive electrode of the voltage source is connected to the second end of the first voltage-controlled current source, and the negative electrode of the voltage source is grounded; The Buck-Boost variable slope sawtooth wave generating circuit comprises: a second voltage-controlled current source, a third capacitor, a voltage source, a fifth switch tube, a first multiplier, a first divider, and a first adder; The control end of the fifth switch tube is connected to the inverting output end of the SR trigger, the first end of the fifth switch tube is connected to the second selection end of the multiplexer, the second end of the fifth switch tube is grounded, the first end of the fifth switch tube is connected to the output end of the second voltage-controlled current source and the first end of the third capacitor, and the second end of the third capacitor is grounded; the input end of the first adder is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit, the output end of the first adder and the output end of the output sampling circuit are connected to the input end of the first divider, the output end of the first divider and the positive electrode of the voltage source are connected to the input end of the first multiplier, the negative electrode of the voltage source is grounded, and the output end of the first multiplier is connected to the second end of the second voltage-controlled current source; The Buck variable slope sawtooth wave generating circuit comprises: a third voltage-controlled current source, a fourth capacitor, a voltage source, a sixth switch tube, a second multiplier, a third multiplier, a second divider, and a first subtractor; The control end of the sixth switch tube is connected to the inverting output end of the SR trigger, the first end of the sixth switch tube is connected to the third selection end of the multiplexer, the second end of the sixth switch tube is grounded, the first end of the sixth switch tube is connected to the output end of the third voltage-controlled current source and the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded; The input end of the second divider is connected to the output end of the input differential sampling circuit and the output end of the output sampling circuit, the input end of the first subtractor is connected to the output end of the second divider and the 1-bit input end, the input end of the second multiplier is connected to the output end of the second divider and the output end of the first subtractor, the input end of the third multiplier is connected to the output end of the second multiplier and the positive electrode of the voltage source, the negative electrode of the voltage source is grounded, and the output end of the third multiplier is connected to the second end of the third voltage-controlled current source.

8. An electrical device, characterized in that: A Buck-Boost PFC converter comprising any one of claims 1 to 7.

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