PFC synchronous rectification circuit

Abstract

The utility model relates to the technical field of electronic circuits, in particular to a PFC (Power Factor Correction) synchronous rectification circuit, which comprises a filter, a rectifier, a PFC controller, a conduction switch, a first charging energy storage circuit, a power supply circuit, an operational amplifier circuit correspondingly outputting high / low level according to an input signal, and a first voltage division conduction circuit, when the conduction switch is switched on, a low-voltage signal is cut off and output to the operational amplifier circuit, when the first partial pressure conduction circuit is switched on, the partial pressure conduction follow current circuit and the PFC boosting electrolysis are switched on, the positive input end is connected with the conduction switch and the partial pressure conduction follow current circuit, and the output end is connected with the first partial pressure conduction circuit and the operational amplifier circuit; and when the conduction switch is switched off, the follow current circuit is conducted by the reverse electromotive force energy of the first charging energy storage circuit through voltage division for charging. According to the utility model, the problems of low power loss, high temperature rise, low reliability and the like caused by a fly-wheel diode in a traditional PFC circuit are solved, and the size and the cost of a power supply are reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, in particular to a PFC synchronous rectification circuit. Background Art

[0002] Since the switching power supply uses a large-capacity filter capacitor after rectification, the load characteristics of the electrical appliance are capacitive. This causes a slightly sawtooth ripple in the DC voltage at both ends of the AC power supply to the appliance due to the charging and discharging of the filter capacitor.

[0003] The minimum value of the voltage on the filter capacitor is far from zero, and is not much different from its maximum value (ripple peak). According to the unidirectional conductivity of the rectifier diode, the rectifier diode will be turned on due to forward bias only when the instantaneous value of the AC line voltage is higher than the voltage on the filter capacitor. When the instantaneous value of the AC input voltage is lower than the voltage on the filter capacitor, the rectifier diode will be cut off due to reverse bias. That is to say, in each half cycle of the AC line voltage, the diode will be turned on only near its peak value. Although the AC input voltage still maintains a roughly sinusoidal waveform, the AC input current is a high-amplitude spike pulse, such as Figure 1 As shown in the figure, this severely distorted current waveform contains a large amount of harmonic components, causing the line power factor to drop seriously.

[0004] In order to solve this problem, active PFC technology was invented in the 20th century. It is a measure taken to address non-sinusoidal current waveform distortion, forcing the AC line current to track the instantaneous change trajectory of the voltage waveform and to keep the current and voltage in phase, making the system purely resistive (line current waveform correction technology), which is PFC (power factor correction).

[0005] See also Figure 2 The PFC circuit in the prior art includes an EMI filter, a rectifier, a PFC controller, a PFC surge protection diode, a PFC boost inductor, a PFC freewheeling diode, a switch tube, and a PFC boost capacitor. One of the most important components is the PFC freewheeling diode in the frame. It is a key component of the PFC circuit and determines the efficiency of the PFC circuit. The loss of this diode = the current flowing through it * the diode Vf (self-conduction voltage drop). At present, the PFC freewheeling tube needs to select a fast recovery diode, which relies on selecting a diode with a lower VF value specification to improve efficiency, but the VF value of the diode cannot be very low, so for high-power power supplies, this method has limited effect in continuing to improve efficiency.

[0006] Therefore, it is urgent to provide a PFC synchronous rectification circuit to overcome the above defects. Utility Model Content

[0007] The main purpose of the utility model is to provide a PFC synchronous rectification circuit, which solves the problems of high loss, low power, high temperature rise and low reliability caused by the freewheeling diode in the traditional PFC circuit, and reduces the size and cost of the power supply.

[0008] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0009] A PFC synchronous rectification circuit comprises: a filter connected to a mains supply, a rectifier connected to the filter, a PFC controller connected to the rectifier, and further comprising:

[0010] A conduction switch connected to the PFC controller to conduct or disconnect a circuit;

[0011] A first charging energy storage circuit, which charges and stores energy when the conduction switch is turned on, and generates reverse electromotive force energy when the conduction switch is turned off;

[0012] a power supply circuit, which supplies power to the connection circuit when the conduction switch is turned off;

[0013] An operational amplifier circuit, connected to the power supply circuit, and outputting a high / low level corresponding to an input signal;

[0014] A first voltage-dividing conduction circuit, connected to the output end of the operational amplifier circuit, and voltage-dividing conduction is performed when the operational amplifier circuit outputs a high level;

[0015] A voltage-dividing conduction freewheeling circuit, which is cut off and outputs a low voltage signal to the operational amplifier circuit when the conduction switch is turned on, and is turned on when the first voltage-dividing conduction circuit is turned on;

[0016] The PFC boost electrolytic capacitor has a positive input end connected to the conduction switch and the voltage-dividing conduction freewheeling circuit, and an output end connected to the first voltage-dividing conduction circuit and the operational amplifier circuit. When the conduction switch is turned off, the reverse electromotive force energy of the first charging energy storage circuit is used to charge the energy storage circuit via the voltage-dividing conduction freewheeling circuit.

[0017] Preferably, the voltage-dividing conduction freewheeling circuit includes: a Pmos tube Q2 whose gate is connected to the first voltage-dividing conduction circuit, a voltage-dividing circuit connected to the gate and drain of the Pmos tube Q2, and a source of the Pmos tube Q2 connected to the reverse input end of the operational amplifier circuit and the PFC boost electrolytic.

[0018] Preferably, the voltage divider circuit includes a resistor R5 and a resistor R6 which are connected in parallel to the gate of the Pmos tube Q2, the other end of the resistor R5 is connected to the first voltage divider conduction circuit, and the other end of the resistor R6 is connected to the first charging energy storage circuit and the same-direction input end of the operational amplifier circuit.

[0019] Preferably, the operational amplifier circuit includes: an operational amplifier U2D whose reverse end is connected to resistor R1, and a positive feedback circuit connected to the output end and the same-direction input end of the operational amplifier U2D, the reverse end of the operational amplifier U2D is connected to resistor R2, the output end of the operational amplifier U2D is connected to the first voltage divider conduction circuit, and the power pin of the operational amplifier U2D is connected to the power supply circuit.

[0020] Preferably, the positive feedback circuit includes a diode D3 and a resistor R3 connected in series.

[0021] Preferably, the first voltage-dividing conduction circuit comprises: a MOS transistor Q3 whose gate is connected via a second voltage-dividing circuit, and a drain of the MOS transistor Q3 is connected to the voltage-dividing conduction freewheeling circuit.

[0022] Preferably, the second voltage divider circuit includes: a resistor R4 and a resistor R7 which are connected in parallel to the gate of the MOS tube Q3, the other end of the resistor R4 is connected to the output end of the operational amplifier circuit, and the other end of the resistor R7 is connected to the source of the MOS tube Q3 and to the reverse input end of the operational amplifier circuit.

[0023] Preferably, the power supply circuit includes: a power supply coil L1B, a diode D2 whose input end is connected to the power supply coil L1B, an electrolytic capacitor C4 whose cathode is connected to the other end of the power supply coil L1B, and an output end of the diode D2 and a positive electrode of the electrolytic capacitor C4 are both connected to a power pin of a transport amplifier of the operational amplifier circuit.

[0024] Preferably, the first charging energy storage circuit includes: a PFC boost inductor L1A having one end connected to the conduction switch and the voltage-dividing conduction freewheeling circuit respectively, and a diode D1 having an input end connected to the other end of the PFC boost inductor L1A, and the other end of the PFC boost inductor L1A is connected to the rectifier and the PFC controller.

[0025] The utility model discloses a PFC synchronous rectification circuit, wherein the PFC controller sends a signal to turn on / off the conduction switch, and when the conduction switch is turned on, the rectified current starts to charge and store energy in the first charging energy storage circuit, at which time, the first voltage-dividing conduction circuit and the voltage-dividing conduction freewheeling circuit are disconnected; when the conduction switch is turned off, the first voltage-dividing conduction circuit and the voltage-dividing conduction freewheeling circuit are turned on, and the reverse electromotive force energy generated by the first charging energy storage circuit is supplied to the PFC boost electrolytic power supply via the voltage-dividing conduction freewheeling circuit, thereby enabling the utility model to solve the problems of high temperature rise and low reliability of the traditional PFC freewheeling diode, and effectively reduce the volume of the heat sink, reduce the volume of the power supply and the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a voltage waveform and current waveform diagram of a sinusoidal half cycle after full-wave rectification in the background technology of the utility model.

[0027] Figure 2 This is a schematic diagram of a conventional active PFC circuit in the background technology of the present utility model.

[0028] Figure 3 The utility model is a circuit diagram of a PFC synchronous rectification circuit according to an embodiment of the present invention.

[0029] Description of the figure numbers in the manual:

[0030] 1-filter, 2-rectifier, 3-PFC controller, 4-conduction switch, 5-first charging energy storage circuit, 6-operational amplifier circuit, 7-first voltage-dividing conduction circuit, 8-voltage-dividing conduction freewheeling circuit, 9-PFC boost electrolysis. DETAILED DESCRIPTION

[0031] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific implementation methods.

[0032] It should be noted that when an element is referred to as being “connected to” or “disposed on” another element, it can be directly on the other element or indirectly on the other element.

[0033] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0035] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0036] See also Figure 3 A PFC synchronous rectification circuit of the present embodiment includes: a filter 1 connected to the mains, a rectifier 2 connected to the filter 1, a PFC controller 3 connected to the rectifier 2, a conduction switch 4 connected to the PFC controller 3 and conducting or disconnecting the connection circuit, a first charging energy storage circuit 5 for charging and storing energy when the conduction switch 4 is turned on and generating reverse electromotive force energy when the conduction switch 4 is turned off, a power supply circuit 6 for supplying power to the connection circuit when the conduction switch 4 is disconnected, an operational amplifier circuit 7 connected to the power supply circuit 6 and outputting a high / low level according to an input signal, and a first charging energy storage circuit 5 for generating reverse electromotive force energy when the conduction switch 4 is turned off. The output end of the circuit 7 is connected to the first voltage-dividing conduction circuit 8 which is voltage-divided and conducted when the operational amplifier circuit 7 outputs a high level, is cut off and outputs a low voltage signal to the operational amplifier circuit 7 when the conduction switch 4 is turned on, and when the first voltage-dividing conduction circuit 8 is turned on, the voltage-dividing conduction freewheeling circuit 9 which is voltage-divided and conducted, the positive input end is connected to the conduction switch 4 and the voltage-dividing conduction freewheeling circuit 9, the output end is connected to the first voltage-dividing conduction circuit 8 and the operational amplifier circuit 7, and when the conduction switch 4 is turned off, the PFC boost electrolytic capacitor is charged by the reverse electromotive force energy of the first charging energy storage circuit 5 through the voltage-dividing conduction freewheeling circuit 9.

[0037] In a preferred embodiment, the conduction switch 4 is a MOS tube, the PFC boost electrolytic capacitor is an electrolytic capacitor C5, and the conduction switch 4 is controlled to be turned on or off by a signal input by the PFC controller 3.

[0038] The first charging energy storage circuit 5 includes: a PFC boost inductor L1A having one end connected to the conduction switch 4 and the voltage-dividing conduction freewheeling circuit 9, and a diode D1 having an input end connected to the other end of the PFC boost inductor L1A, and the other end of the PFC boost inductor L1A is connected to the rectifier 2 and the PFC controller 3. Specifically, when the conduction switch 4 is turned on, the rectified DC power starts to charge and store energy in the PFC inductor L1A.

[0039] The voltage-dividing conduction freewheeling circuit 9 includes: a gate connected to the first voltage-dividing conduction circuit 8, a voltage-dividing circuit connected to the gate and drain of the Pmos tube Q2, the source of the Pmos tube Q2 is connected to the reverse input end of the operational amplifier circuit 7 and the PFC boosting electrolytic, the voltage-dividing circuit includes a resistor R5 and a resistor R6 connected in parallel to the gate of the Pmos tube Q2, the other end of the resistor R5 is connected to the first voltage-dividing conduction circuit 8, and the other end of the resistor R6 is connected to the first charging energy storage circuit 5 and the same-direction input end of the operational amplifier circuit 7. Specifically, the other end of the resistor R6 is connected to the drain of the mos tube Q1 and one end of the PFC boosting inductor L1A.

[0040] The operational amplifier circuit 7 includes: an operational amplifier U2D whose reverse end is connected to a resistor R1, and a positive feedback circuit connected to the output end and the same-direction input end of the operational amplifier U2D, the reverse end of the operational amplifier U2D is connected to a resistor R2, the output end of the operational amplifier U2D is connected to the first voltage-dividing conduction circuit 8, the power supply pin of the operational amplifier U2D is connected to the power supply circuit 6, and the positive feedback circuit includes a diode D3 and a resistor R3 connected in series. The power supply circuit 6 includes: a power supply coil L1B, a diode D2 whose input end is connected to the power supply coil L1B, an electrolytic capacitor C4 whose cathode is connected to the other end of the power supply coil L1B, and the output end of the diode D2 and the positive electrode of the electrolytic capacitor C4 are both connected to the power supply pin of the transport amplifier of the operational amplifier circuit 7. Specifically, the drain of the Pmos tube Q2 is connected to the non-inverting input terminal of the transport amplifier U2D via the resistor R2, and the source of the Pmos tube Q2 is connected to the reverse input terminal of the transport amplifier U2D via the resistor R1. When the mos tube Q1 is in the on state, the rectified DC power starts to charge and store energy in the PFC inductor L1A, and the drain voltage Q2+ of the Pmos tube Q2 is less than the source voltage HV+. At this time, the output terminal of the operational amplifier outputs a low-level signal, and the first voltage-dividing conduction circuit 8 is cut off.

[0041] The first voltage-dividing conduction circuit 8 includes: a MOS tube Q3 whose gate is connected via a second voltage-dividing circuit, a drain of the MOS tube Q3 is connected to the voltage-dividing conduction freewheeling circuit 9, and the second voltage-dividing circuit includes: a resistor R4 and a resistor R7 connected in parallel to the gate of the MOS tube, the other end of the resistor R4 is connected to the output end of the operational amplifier circuit 6, and the other end of the resistor R7 is connected to the source of the MOS tube Q3 and the reverse input end of the operational amplifier circuit 6. Specifically, the drain of the MOS tube Q3 is connected to the resistor R5, and the source of the MOS tube Q3 is connected to the resistor R7 and the resistor R1, respectively.

[0042] The working principle of the utility model is as follows: the PFC controller 3 sends a conduction signal to the conduction switch 4 to turn on the MOS tube Q1, the current is filtered by the filter 1, rectified by the rectifier 2, and then charged and stored in the PFC inductor L1A through the conduction switch 4, the drain voltage Q2+ of the MOS tube Q2 is less than the source voltage HV+, at this time, the output end of the operational amplifier outputs a low-level signal, at this time the MOS tube Q3 is in the off state, the PMOS tube Q2 is also in the off state, and the PMOS tube Q2 remains cut off; when the PFC controller 3 sends a disconnection signal to the conduction switch 4, the MOS tube Q1 is cut off, and the PFC inductor L1A is cut off. A generates reverse electromotive force and charges the large electrolytic C5 through the freewheeling Pmos tube Q2, causing the drain voltage Q2+ of the Pmos tube Q2 to be greater than the source voltage HV+. At this time, the output end of the op amp outputs a high-level signal, which is divided by the voltage-dividing resistors R4 and R7. The high-level voltage obtained after the voltage division directly turns on the mos tube Q3. Since the mos tube Q3 is turned on, the high level Q2+ generates a voltage division through the resistors R6 and R5. At this time, the gate voltage of the P-channel MOS tube Q2 is less than the source voltage, and the Pmos tube Q2 is turned on. In this way, the Pmos tube Q2 completes the freewheeling function in the PFC circuit.

[0043] The utility model greatly reduces the freewheeling tube loss caused by the circulating current and the conduction voltage drop, greatly improves the overall efficiency of the PFC circuit, overcomes the problem of high loss and low efficiency caused by the freewheeling diode in the prior art, and because the loss and temperature rise are reduced, the PFC circuit can use a smaller heat sink, which can further reduce the size of the power supply and reduce the cost.

[0044] The above shows and describes the basic principle and main features of the utility model and the advantages of the utility model. Those skilled in the art should understand that the utility model is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the utility model. Without departing from the spirit and scope of the utility model, the utility model may have various changes and improvements, which fall within the scope of the utility model to be protected. The scope of protection claimed by the utility model is defined by the attached claims and their equivalents.

Claims

1. A PFC synchronous rectification circuit, comprising: A filter connected to the mains, a rectifier connected to the filter, and a PFC controller connected to the rectifier, characterized in that it also includes: A conduction switch connected to the PFC controller to conduct or disconnect a circuit; A first charging energy storage circuit, which charges and stores energy when the conduction switch is turned on, and generates reverse electromotive force energy when the conduction switch is turned off; a power supply circuit, which supplies power to the connection circuit when the conduction switch is turned off; An operational amplifier circuit, connected to the power supply circuit, and outputting a high / low level corresponding to an input signal; A first voltage-dividing conduction circuit, connected to the output end of the operational amplifier circuit, and voltage-dividing conduction is performed when the operational amplifier circuit outputs a high level; A voltage-dividing conduction freewheeling circuit, which is cut off and outputs a low voltage signal to the operational amplifier circuit when the conduction switch is turned on, and is turned on when the first voltage-dividing conduction circuit is turned on; The PFC boost electrolytic capacitor has a positive input end connected to the conduction switch and the voltage-dividing conduction freewheeling circuit, and an output end connected to the first voltage-dividing conduction circuit and the operational amplifier circuit. When the conduction switch is turned off, the reverse electromotive force energy of the first charging energy storage circuit is used to charge the energy storage circuit via the voltage-dividing conduction freewheeling circuit.

2. The PFC synchronous rectification circuit according to claim 1, characterized in that: The voltage-dividing conduction freewheeling circuit includes: a gate connected to a Pmos tube Q2 with the first voltage-dividing conduction circuit, a voltage-dividing circuit connected to the gate and drain of the Pmos tube Q2, and a source of the Pmos tube Q2 connected to the reverse input end of the operational amplifier circuit and the PFC boost electrolytic.

3. The PFC synchronous rectification circuit according to claim 2, characterized in that: The voltage divider circuit includes resistors R5 and R6 which are connected in parallel to the gate of the Pmos tube Q2, the other end of the resistor R5 is connected to the first voltage divider conduction circuit, and the other end of the resistor R6 is connected to the first charging energy storage circuit and the same-direction input end of the operational amplifier circuit.

4. The PFC synchronous rectification circuit according to claim 1, characterized in that: The operational amplifier circuit includes: an operational amplifier U2D whose reverse end is connected to a resistor R1, and a positive feedback circuit connected to the output end and the same-direction input end of the operational amplifier U2D, the reverse end of the operational amplifier U2D is connected to the resistor R2, the output end of the operational amplifier U2D is connected to the first voltage divider conduction circuit, and the power pin of the operational amplifier U2D is connected to the power supply circuit.

5. The PFC synchronous rectification circuit according to claim 4, characterized in that: The positive feedback circuit includes a diode D3 and a resistor R3 connected in series.

6. The PFC synchronous rectification circuit according to claim 1, characterized in that: The first voltage-dividing conduction circuit comprises: a MOS transistor Q3 whose gate is connected via a second voltage-dividing circuit, and a drain of the MOS transistor Q3 is connected to the voltage-dividing conduction freewheeling circuit.

7. The PFC synchronous rectification circuit according to claim 6, characterized in that: The second voltage divider circuit includes: a resistor R4 and a resistor R7 which are connected in parallel to the gate of the MOS tube Q3, the other end of the resistor R4 is connected to the output end of the operational amplifier circuit, and the other end of the resistor R7 is connected to the source of the MOS tube Q3 and the reverse input end of the operational amplifier circuit.

8. The PFC synchronous rectification circuit according to claim 1, characterized in that: The power supply circuit includes: a power supply coil L1B, a diode D2 whose input end is connected to the power supply coil L1B, an electrolytic capacitor C4 whose cathode is connected to the other end of the power supply coil L1B, and an output end of the diode D2 and a positive electrode of the electrolytic capacitor C4 are both connected to a power pin of a transport amplifier of the operational amplifier circuit.

9. The PFC synchronous rectification circuit according to claim 1, characterized in that: The first charging energy storage circuit includes: a PFC boost inductor L1A having one end connected to the conduction switch and the voltage-dividing conduction freewheeling circuit respectively, and a diode D1 having an input end connected to the other end of the PFC boost inductor L1A, and the other end of the PFC boost inductor L1A is connected to the rectifier and the PFC controller.

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