Power factor correction circuit and switching power supply

Abstract

The utility model provides a power factor correction circuit and a switching power supply, the power factor correction circuit is a totem-pole bridgeless power factor correction circuit, and the power factor correction circuit comprises a boost inductor; the high-frequency rectifier bridge arm, the power-frequency rectifier bridge arm and the output filter capacitor are sequentially connected between the positive output end and the negative output end of the power factor correction circuit; and a control circuit; the negative output end of the power factor correction circuit is connected with the first reference ground. The power factor correction circuit further comprises a sampling resistor. One end of the sampling resistor is connected with the first input end of the power factor correction circuit and the control circuit, the other end of the sampling resistor is connected with one end of the boost inductor, and the other end of the boost inductor is connected with the midpoint of the high-frequency rectifier bridge arm. One end of the sampling resistor or the other end of the sampling resistor and the reference ground of the control circuit are connected together and then are connected to the second reference ground, and the first reference ground and the second reference ground are electrically isolated. The circuit can be simplified.

Description

Technical Field

[0001] The utility model relates to a power conversion circuit such as a power factor correction circuit. Background Art

[0002] With the rapid development of power electronics technology, the number of AC-DC converter users has increased rapidly, and most power electronic devices need to convert AC power into DC power through rectification and conversion technology, which leads to a large amount of harmonic current injected into the AC power grid, damaging the power quality of the AC power grid. In order to reduce the mutual influence of load harmonics on the power grid and other equipment, the input current harmonic content and power density of each electronic device need to meet the current harmonic requirements of AC power equipment. Therefore, it is of great significance to study high power density PFC converter technology.

[0003] Compared with the traditional bridge Boost PFC converter, the bridgeless PFC uses switches to replace the bridge arm diodes, reducing the loss of the switch devices in the conduction path, thereby improving efficiency. Among various bridgeless PFC topologies, the totem pole bridgeless PFC has become the mainstream due to its advantages such as fewer components and less common-mode noise. Figure 1 The circuit diagram of the well-known totem pole bridgeless PFC is shown, including a boost inductor L, a high-frequency bridge arm composed of a first switch tube Q1 and a second switch tube Q2, and an industrial frequency bridge arm composed of a third switch tube Q3 and a fourth switch tube Q4; wherein the first switch tube Q1 and the second switch tube Q2 are high-frequency switches, the third switch tube Q3 and the fourth switch tube Q4 are industrial frequency switches, and the industrial frequency switches can be replaced by diodes; specifically: in the industrial frequency AC positive half cycle of the totem pole PFC converter, the first switch tube Q1 acts as a high-frequency rectifier, the second switch tube Q2 acts as a high-frequency main tube, the third switch tube Q3 acts as an industrial frequency switch and remains off, and the fourth switch tube Q4 acts as an industrial frequency switch and remains on, and when the boost inductor L is excited, the current flows from the first end of the AC input source → the second switch tube Q2 → the fourth switch tube Q4. Q4→the second end of the AC input source, when the boost inductor L is demagnetized, the current flows from the first end of the AC input source→the first switch tube Q1→the filter capacitor Co→the fourth switch tube Q4→the second end of the AC input source; in the negative half-cycle of the industrial frequency AC of the totem pole PFC converter, the first switch tube Q1 serves as a high-frequency main tube, the second switch tube Q2 serves as a high-frequency rectifier tube, the third switch tube Q3 serves as an industrial frequency switch tube and remains turned on, and the fourth switch tube Q4 serves as an industrial frequency switch tube and remains turned off, when the boost inductor L is excited, the current flows from the second end of the AC input source→the third switch tube Q3→the first switch tube Q1→the first end of the AC input source, and when the boost inductor L is demagnetized, the current flows from the second end of the AC input source→the third switch tube Q3→the filter capacitor Co→the second switch tube Q2→the first end of the AC input source.

[0004] Since the circuit diagram of the totem pole bridgeless PFC swaps roles in the positive half-cycle and the negative half-cycle of the industrial frequency AC, the totem pole bridgeless PFC circuit needs to detect the zero-crossing moment of the current in the boost inductor to generate an on or off signal for the first switch Q1 and the second switch Q2. The prior art generally connects a sampling resistor in series before the boost inductor, and generates a zero-crossing signal through an operational amplifier circuit and a comparator circuit. The zero-crossing signal is connected to the second reference ground. Since the control circuit is connected to the first reference ground, the zero-crossing signal cannot be used directly. In this way, the zero-crossing signal needs to be transmitted to the control circuit through a digital isolator. Therefore, an additional digital isolator needs to be added, and a set of isolated power supplies needs to be provided for the control circuit, which will increase the complexity of the circuit and the device cost, and is not conducive to the realization of high power density. Utility Model Content

[0005] In view of this, the technical problem to be solved by the present invention is to provide a power factor correction circuit and a switching power supply, which can at least to some extent solve the deficiencies of the above-mentioned prior art.

[0006] As a first aspect of the present invention, the technical solution of the embodiment of the power factor correction circuit provided is as follows:

[0007] A power factor correction circuit, which is a totem pole bridgeless power factor correction circuit, comprises: a boost inductor; a high-frequency rectifier bridge arm, a power frequency rectifier bridge arm and an output filter capacitor connected in sequence between a positive output end of the power factor correction circuit and a negative output end of the power factor correction circuit; and a control circuit; the negative output end of the power factor correction circuit is connected to a first reference ground, wherein: the power factor correction circuit also comprises a sampling resistor; one end of the sampling resistor is connected to a first input end of the power factor correction circuit and the control circuit, the other end of the sampling resistor is connected to one end of the boost inductor, the other end of the boost inductor is connected to a midpoint of the high-frequency rectifier bridge arm, the midpoint of the power frequency rectifier bridge arm is connected to a second input end of the power factor correction circuit, one end of the sampling resistor or the other end of the sampling resistor is connected to a reference ground of the control circuit and then connected to a second reference ground, and the first reference ground and the second reference ground are electrically isolated.

[0008] Further, the control circuit is powered by an isolated voltage source, and a reference ground of the isolated voltage source is connected to the second reference ground.

[0009] Furthermore, the switch tube in the power frequency rectifier bridge arm is a diode or an active switch tube.

[0010] Furthermore, the control circuit includes a zero-crossing detection circuit for detecting a zero-crossing signal indicating that the boost inductor current is zero through the sampling resistor.

[0011] Preferably, the zero-crossing detection circuit comprises a sampling circuit and a comparison circuit, the sampling circuit is used to detect the positive and negative voltages on the sampling resistor, and then the comparison circuit compares the positive and negative voltages with a set voltage threshold to generate the zero-crossing signal.

[0012] Preferably, the zero-crossing detection circuit includes a resistor R1, a resistor R2, a resistor R4, a capacitor C2 and an operational amplifier U1, the positive power supply terminal of the operational amplifier U1 is used to input a power supply voltage, one end of the resistor R1, one end of the sampling resistor and the negative power supply terminal of the operational amplifier U1 are connected together and then connected to the second reference ground, the other end of the resistor R1, one end of the resistor R4 and one end of the capacitor C2 are simultaneously connected to the inverting input terminal of the operational amplifier U1, one end of the resistor R2 is connected to the other end of the sampling resistor, the other end of the resistor R2 and one end of the resistor R3 are simultaneously connected to the non-inverting input terminal of the operational amplifier U1, the other end of the resistor R3 is used to input a bias voltage, and the other end of the resistor R4, the other end of the capacitor C2 and the output terminal of the operational amplifier U1 are connected together to output the zero-crossing signal.

[0013] Furthermore, the zero-crossing detection circuit further includes a capacitor C1, and the capacitor C1 is connected across the resistor R1.

[0014] Preferably, the switch tube in the high-frequency rectifier bridge arm is a silicon carbide switch tube.

[0015] Preferably, the withstand voltage of the switch tube in the high-frequency rectifier bridge arm is above 300V.

[0016] As a second aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0017] A switching power supply, comprising: a power factor correction circuit as described in any one of the first aspects above.

[0018] The beneficial effects of the utility model are as follows:

[0019] (1) In the embodiment of the utility model, one end of the sampling resistor or the other end of the sampling resistor is connected to the reference ground of the control circuit and then connected to the second reference ground. The first reference ground and the second reference ground are electrically isolated. The control circuit can be directly connected to the zero-crossing signal generated by the sampling resistor detection circuit, which simplifies the circuit structure, helps to reduce the volume and reduce the cost.

[0020] (2) In the embodiment of the utility model, one end of the sampling resistor is connected to the first input end of the power factor correction circuit and the control circuit, and the sampling signal of the AC high voltage end is directly input into the control circuit for processing, thereby avoiding the signal transmission delay caused by the complex circuit of signal isolation transmission, and can simplify the overall circuit of products such as switching power supplies to the greatest extent through chip design, providing a low-cost solution for products such as high-frequency, high-power density and miniaturized switching power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A circuit diagram of a well-known totem pole bridgeless PFC;

[0022] Figure 2 A first schematic diagram of a power factor correction circuit according to a first embodiment of the utility model;

[0023] Figure 3 A second schematic diagram of the power factor correction circuit of the first embodiment of the utility model;

[0024] Figure 4 A specific principle diagram of a zero-crossing detection circuit in a control circuit of a power factor correction circuit of the first embodiment of the utility model. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application.

[0026] It should be noted that the terms "including" and "having" and any variations thereof described in the specification and claims of the present application are intended to cover non-exclusive inclusions. For example, the inclusion of a series of components, unit circuits or control timings is not necessarily limited to those components, unit circuits or control timings clearly listed, but may include components, unit circuits or control timings that are not clearly listed or inherent to these circuits.

[0027] In addition, the embodiments and features of the embodiments in this application may be combined with each other if there is no conflict.

[0028] It should be understood that, in the specification and the claims, when an element is described as being “connected” to another element, the element may be “directly connected” to the other element, or be “connected” to the other element through a third element; when a step is described as being continued to another step, the step may be directly continued to the other step, or be continued to the other step through a third step.

[0029] First embodiment

[0030] This embodiment discloses a power factor correction circuit. Figure 2 The first schematic diagram of the power factor correction circuit of the first embodiment of the utility model, Figure 3 This is the second schematic diagram of the power factor correction circuit of the first embodiment of the utility model, see Figure 2 and Figure 3 , the power factor correction circuit is a totem pole bridgeless power factor correction circuit, including: a boost inductor L1; a high-frequency rectifier bridge arm, a power frequency rectifier bridge arm and an output filter capacitor C1 connected in sequence between the positive output terminal of the power factor correction circuit and the negative output terminal of the power factor correction circuit; and a control circuit; the negative output terminal of the power factor correction circuit is connected to the first reference ground GND1, wherein: the power factor correction circuit also includes a sampling resistor RS1; one end of the sampling resistor RS1 is connected to the first input terminal 1 of the power factor correction circuit and the control circuit, the other end of the sampling resistor RS1 is connected to one end of the boost inductor L1, the other end of the boost inductor L1 is connected to the midpoint of the high-frequency rectifier bridge arm, the midpoint of the power frequency rectifier bridge arm is connected to the second input terminal 2 of the power factor correction circuit, one end of the sampling resistor RS1 (see Figure 3 ) or the other end of the sampling resistor RS1 (see Figure 2 ) is connected to the reference ground of the control circuit and then connected to the second reference ground GND2. The first reference ground GND1 and the second reference ground GND2 are electrically isolated.

[0031] Among them, the switch tubes of the high-frequency rectifier bridge arm are switch tube S1 and switch tube S2, each of which can be configured to operate at a frequency of at least 65kHz; the switch tubes in the industrial frequency rectifier bridge arm are switch tube Q1 and switch tube Q2; the resistance value of the sampling resistor RS1 can be less than 60 milliohms.

[0032] In this embodiment, one end of the sampling resistor RS1 or the other end of the sampling resistor RS1 is connected to the reference ground of the control circuit and then connected to the second reference ground GND2. The first reference ground GND1 and the second reference ground GND2 are electrically isolated. The control circuit can be directly connected to the zero-crossing signal generated by the sampling resistor detection circuit, which simplifies the circuit structure and is conducive to reducing the volume and reducing the cost. In addition, in this embodiment, one end of the sampling resistor RS1 is connected to the first input terminal 1 of the power factor correction circuit and the control circuit, and the sampling signal of the AC high voltage end is directly input into the control circuit for processing, avoiding the signal transmission delay caused by the complex circuit of signal isolation transmission, and can simplify the whole circuit of products such as switching power supplies to the greatest extent through chip design, providing a low-cost solution for products such as high-frequency, high-power density and miniaturized switching power supplies.

[0033] For further information, please see Figure 2 and Figure 3 , the control circuit is powered by an isolated voltage source, and the reference ground of the isolated voltage source is connected to the second reference ground GND2.

[0034] Furthermore, the switch tube in the power frequency rectifier bridge arm is a diode or an active switch tube. When the switch tube in the power frequency rectifier bridge arm is an active switch tube, it is beneficial to improve efficiency.

[0035] Furthermore, the control circuit includes a zero-crossing detection circuit for detecting a zero-crossing signal indicating that the boost inductor current is zero through a sampling resistor.

[0036] Preferably, the zero-crossing detection circuit includes a sampling circuit and a comparison circuit. The sampling circuit is used to detect the positive and negative voltages on the sampling resistor, and then the comparison circuit compares the positive and negative voltages with a set voltage threshold to generate a zero-crossing signal.

[0037] Figure 4 This is a specific schematic diagram of a zero-crossing detection circuit in the control circuit of the power factor correction circuit of the first embodiment of the utility model, see Figure 4 The zero-crossing detection circuit includes a resistor R1, a resistor R2, a resistor R4, a capacitor C2 and an operational amplifier U1. The positive power supply terminal of the operational amplifier U1 is used to input a power supply voltage. One end of the resistor R1, one end of the sampling resistor and the negative power supply terminal of the operational amplifier U1 are connected together and then connected to a second reference ground. The other end of the resistor R1, one end of the resistor R4 and one end of the capacitor C2 are simultaneously connected to the inverting input terminal of the operational amplifier U1. One end of the resistor R2 is connected to the other end of the sampling resistor. The other end of the resistor R2 and one end of the resistor R3 are simultaneously connected to the non-inverting input terminal of the operational amplifier U1. The other end of the resistor R3 is used to input a bias voltage. The other end of the resistor R4, the other end of the capacitor C2 and the output terminal of the operational amplifier U1 are connected together to output a zero-crossing signal.

[0038] Figure 4The zero-crossing detection circuit in the circuit includes an operational amplifier U1 powered by a voltage source. The operational amplifier U1 adopts a differential sampling circuit and sets a bias value voltage so as to have the function of detecting the positive and negative voltages generated by the sampling resistor RS1. Since the sampling resistor RS1 and the boost inductor L1 are connected in series, the positive and negative voltages generated by the sampling resistor RS1 can represent the current in the boost inductor L1. By comparing it with the set voltage threshold through the operational amplifier U1, a zero-crossing signal can be generated. Figure 4 The circuit adds a bias voltage Vr, so that the negative voltage across the sampling resistor outputs a positive voltage after passing through the operational amplifier. Therefore, only a single positive voltage source is needed for power supply, which simplifies the design of the auxiliary source circuit. The voltage source is connected to the second reference ground.

[0039] Furthermore, the bandwidth of the operational amplifier U1 may be greater than the switching frequency of each of the switch tubes S1 and S2, thereby ensuring that the zero-crossing signal is not distorted and has a small delay.

[0040] Please continue to see Figure 4 The zero-crossing detection circuit further includes a capacitor C1, which is connected across the resistor R1, thereby improving the anti-interference capability of the circuit and reducing the distortion of the sampling circuit.

[0041] Preferably, the switch tube in the high-frequency rectifier bridge arm is a silicon carbide switch tube, which can further increase the operating frequency and achieve higher power density and smaller product volume.

[0042] Preferably, the withstand voltage of the switch tube in the high-frequency rectifier bridge arm is above 300V, such as 300V, 600V or 1200V.

[0043] Second embodiment

[0044] This embodiment provides a switching power supply, which includes any power factor correction circuit in the first embodiment.

[0045] Since the switching power supply of this embodiment includes any one of the power factor correction circuits in the first embodiment, it is possible to simplify the signal transmission path, sample the same reference ground as the controller, and eliminate the need for large-volume isolation devices, thereby providing a feasible solution for the integration of control circuits. In addition, the overall circuit of products such as switching power supplies can be simplified to the greatest extent through chip design, providing a low-cost solution for products such as high-frequency, high-power density and miniaturized switching power supplies.

[0046] The above are only implementation modes of the present invention. It should be pointed out that the above implementation modes should not be regarded as limitations of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A power factor correction circuit, the power factor correction circuit being a totem pole bridgeless power factor correction circuit, comprising: Boost inductor; A high-frequency rectifier bridge arm, an industrial frequency rectifier bridge arm and an output filter capacitor are sequentially connected between the positive output end of the power factor correction circuit and the negative output end of the power factor correction circuit; and a control circuit; the negative output end of the power factor correction circuit is connected to a first reference ground, characterized in that: the power factor correction circuit also includes a sampling resistor; one end of the sampling resistor is connected to the first input end of the power factor correction circuit and the control circuit, the other end of the sampling resistor is connected to one end of the boost inductor, the other end of the boost inductor is connected to the midpoint of the high-frequency rectifier bridge arm, the midpoint of the industrial frequency rectifier bridge arm is connected to the second input end of the power factor correction circuit, one end of the sampling resistor or the other end of the sampling resistor is connected to the reference ground of the control circuit and then connected to the second reference ground, and the first reference ground and the second reference ground are electrically isolated.

2. The power factor correction circuit according to claim 1, characterized in that: The control circuit is powered by an isolated voltage source, and a reference ground of the isolated voltage source is connected to the second reference ground.

3. The power factor correction circuit according to claim 1, characterized in that: The switch tube in the power frequency rectifier bridge arm is a diode or an active switch tube.

4. The power factor correction circuit according to claim 1, characterized in that: The control circuit includes a zero-crossing detection circuit, which is used to detect a zero-crossing signal indicating that the boost inductor current is zero through the sampling resistor.

5. The power factor correction circuit according to claim 4, characterized in that: The zero-crossing detection circuit includes a sampling circuit and a comparison circuit. The sampling circuit is used to detect the positive and negative voltages on the sampling resistor, and then the comparison circuit compares the positive and negative voltages with a set voltage threshold to generate the zero-crossing signal.

6. The power factor correction circuit according to claim 5, characterized in that: The zero-crossing detection circuit includes a resistor R1, a resistor R2, a resistor R4, a capacitor C2 and an operational amplifier U1, the positive power supply terminal of the operational amplifier U1 is used to input a power supply voltage, one end of the resistor R1, one end of the sampling resistor and the negative power supply terminal of the operational amplifier U1 are connected together and then connected to the second reference ground, the other end of the resistor R1, one end of the resistor R4 and one end of the capacitor C2 are simultaneously connected to the inverting input terminal of the operational amplifier U1, one end of the resistor R2 is connected to the other end of the sampling resistor, the other end of the resistor R2 and one end of the resistor R3 are simultaneously connected to the non-inverting input terminal of the operational amplifier U1, the other end of the resistor R3 is used to input a bias voltage, the other end of the resistor R4 and the other end of the capacitor C2 are connected together with the output terminal of the operational amplifier U1 to output the zero-crossing signal.

7. The power factor correction circuit according to claim 6, characterized in that: The zero-crossing detection circuit further includes a capacitor C1 , and the capacitor C1 is connected across the resistor R1 .

8. The power factor correction circuit according to any one of claims 1 to 7, characterized in that: The switch tube in the high-frequency rectifier bridge arm is a silicon carbide switch tube.

9. The power factor correction circuit according to any one of claims 1 to 7, characterized in that: The withstand voltage of the switch tube in the high-frequency rectifier bridge arm is above 300V.

10. A switching power supply, characterized in that: The invention comprises a power factor correction circuit as claimed in any one of claims 1 to 9.

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