CN110212749B

CN110212749B - PFC module

Info

Publication number: CN110212749B
Application number: CN201910543562.3A
Authority: CN
Inventors: 王斌
Original assignee: Hisense Guangdong Air Conditioning Co Ltd
Current assignee: Hisense Guangdong Air Conditioning Co Ltd
Priority date: 2019-06-21
Filing date: 2019-06-21
Publication date: 2022-03-04
Anticipated expiration: 2039-06-21
Also published as: CN110212749A

Abstract

The invention discloses a PFC (power factor correction) module, which comprises a shell and a bridge rectifier circuit formed by connecting four rectifier diodes, wherein a power switch tube is respectively connected in parallel on one upper bridge rectifier diode and a lower bridge rectifier diode connected with the upper bridge rectifier diode, a sampling resistor is connected between the anodes of the two lower bridge rectifier diodes, a current signal sampling point is arranged at the connecting node of the sampling resistor and the lower bridge rectifier diode connected with the power switch tube in parallel, and PFC control is carried out according to a PFC control algorithm and a PFC control algorithm according to a voltage signal of an alternating current power supply and a current signal of the current signal sampling point, so that the aim of correcting a power factor is fulfilled. The PFC module of the invention shares the power factor correction circuit and the rectification circuit, thereby saving a single PFC circuit link, reducing circuit loss and obviously improving the conversion efficiency of the AC/DC power supply.

Description

PFC module

Technical Field

The invention belongs to the technical field of power circuits, and particularly relates to a PFC module.

Background

In order to meet the energy-saving requirement of household appliances, frequency conversion products are rapidly developed. Most of the current frequency conversion products need to go through the power conversion process from ac → dc → ac, and the phase difference between the current and the voltage will cause the loss of the converted power during the conversion process, so that the power factor correction circuit is needed to improve the power factor of the power circuit.

The power Factor correction circuit, namely a pfc (power Factor correction) circuit, is used for controlling a current waveform to be synchronous with a waveform of an input voltage. A conventional PFC module, as shown in fig. 1, includes an inductor L1, a boost diode D5, a switching tube Q1, a driving chip, and other main components, and is connected between a rectifier bridge formed by four diodes D1-D4 and a large-capacity energy storage capacitor C1 during use. The working principle is as follows: the driving chip generates a pulse signal to control the switching tube Q1 to be switched on or switched off according to the voltage change of the alternating current input power supply AC. The inductor L1 stores energy while the switching tube Q1 is on, outputs the stored energy while the switching tube Q1 is off, and charges the large-capacity charging capacitor C1 through the boost diode D5, thereby compensating for the power factor.

As shown in fig. 1, in a practical application process of a conventional PFC module, an external rectifier bridge is required, an alternating current input power AC is firstly converted into an alternating current-direct current (AC-DC) through the rectifier bridge, and then the generated DC power is transmitted to the PFC module for a power factor correction process. The disadvantage of this circuit design is the low AC-DC conversion efficiency.

Disclosure of Invention

The invention aims to provide a PFC module without an external rectifier bridge, which can realize the obvious improvement of the power conversion efficiency by controlling the AC/DC conversion process and the power factor correction process to be carried out synchronously.

In order to solve the technical problems, the invention adopts the following technical scheme:

a PFC module comprises a shell, wherein the shell comprises a first side and a second side which are in relative position relation, a direct current output end and an alternating current input end are arranged on the first side, and an upper bridge control signal input pin, a lower bridge control signal input pin and a sampling current output pin are arranged on the second side; a bridge rectifier circuit, a sampling resistor, an upper bridge driving circuit and a lower bridge driving circuit are packaged in the shell; the alternating current side of the bridge rectifier circuit is connected with the alternating current input end, and the direct current side of the bridge rectifier circuit is connected with the direct current output end and comprises two upper bridge rectifier diodes and two lower bridge rectifier diodes; one of the upper bridge rectifier diodes and the lower bridge rectifier diode connected with the upper bridge rectifier diode are respectively connected with a power switch tube in parallel, and the power switch tubes are correspondingly an upper bridge power switch tube and a lower bridge power switch tube; the sampling resistor is connected between the anodes of the two lower bridge rectifier diodes, and a current signal sampling point is arranged at the connecting node of the sampling resistor and the lower bridge rectifier diodes connected with the power switch tube in parallel and is connected with the sampling current output end; the upper bridge driving circuit is connected with the upper bridge control signal input pin and controls the on-off of the upper bridge power switch tube according to the received upper bridge control signal; the lower bridge driving circuit is connected with the lower bridge control signal input pin and controls the on-off of the lower bridge power switch tube according to the received lower bridge control signal; when the PFC module is used, an alternating current input end of the PFC module is externally connected with an alternating current power supply, and an inductor is connected in series in a transmission line of the alternating current power supply; the upper bridge control signal input pin, the lower bridge control signal input pin and the sampling current output pin are externally connected with a main control chip and used for receiving an upper bridge control signal and a lower bridge control signal output by the main control chip; the main control chip controls the upper bridge power switch tube to be closed and controls the lower bridge power switch tube to be switched on and off during the positive voltage half cycle of the alternating current power supply, and current signals are collected through the sampling current output pin during the switching-on period of the lower bridge power switch tube; during the negative half cycle of the voltage of the alternating current power supply, the lower bridge power switch tube is controlled to be closed, the upper bridge power switch tube is controlled to be switched on and off, and a current signal is collected through the sampling current output pin during the closing of the upper bridge power switch tube; and the main control chip combines the acquired current signal and the voltage signal of the alternating current power supply and performs PFC control on the PFC module according to a PFC control algorithm.

Compared with the prior art, the invention has the advantages and positive effects that:

(1) the invention combines the rectification circuit and the power factor correction circuit into a whole to form an integrated PFC module, thereby leading the peripheral circuit of the PFC module to be simpler and more compact and being convenient for the miniaturization design of an electric control board;

(2) the PFC module can directly externally insert an alternating current power supply without an external rectifier bridge in practical application, and can complete a power factor correction process simultaneously in the process of carrying out alternating current-direct current conversion control on the alternating current power supply, so that the power conversion efficiency of the PFC module can be obviously improved, the power loss is reduced, and the electric energy is saved;

(3) according to the invention, the sampling resistor is connected between the anodes of the two lower bridge rectifier diodes for current sampling, so that the current in the inductive charging stage can be obtained in the positive half period of the alternating current input power supply, and the current in the follow current stage can be obtained in the negative half period of the alternating current input power supply, so that the current sampling is completed on the low-voltage side, and the simplification of the current sampling is realized, and the circuit matching with a control circuit is facilitated;

(4) according to the invention, the sampling resistor is arranged on the low-voltage side of the rectifier bridge, compared with the common arrangement of the sampling resistor or other sampling circuits on the high-voltage side, the safety regulation problem is not required to be considered, and the circuit design requirement can be met only by selecting a conventional resistor device and not adding a high-voltage protection measure aiming at the resistor device, so that the hardware cost can be obviously reduced;

(5) the PFC module adopts a dual in-line pin packaging mode, so that the PCB design and processing of the electric control board can be simplified; in addition, the high-voltage terminal and the low-voltage terminal are separated and are respectively arranged on two opposite sides of the PFC module, so that the problem of electromagnetic interference generated by a high-voltage signal on a low-voltage signal can be solved, and the reliability of the operation of a system circuit is improved.

Other features and advantages of the present invention will become more apparent from the detailed description of the embodiments of the present invention when taken in conjunction with the accompanying drawings.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram of a conventional PFC circuit;

fig. 2 is a schematic block diagram of a PFC module according to an embodiment of the present invention;

fig. 3 is a current flow diagram of the PFC circuit shown in fig. 2 operating during the positive half cycle of the ac power source and during the inductor charging process;

fig. 4 is a current flow diagram of the PFC circuit of fig. 2 operating during the positive half cycle of the ac power source and during a circuit freewheeling process;

fig. 5 is a current flow diagram of the PFC circuit of fig. 2 operating during the negative half cycle of the ac power source and during the inductor charging process;

fig. 6 is a current flow diagram of the PFC circuit of fig. 2 operating during the negative half cycle of the ac power source and during a circuit freewheeling process;

FIG. 7 is a graph of a current waveform flowing through a sampling resistor;

FIG. 8 is a circuit schematic of one embodiment of the under and upper bridge drivers of FIG. 2.

Detailed Description

Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention.

It should be noted that in the description of the present invention, the terms of direction or positional relationship indicated by the terms "left", "right", etc. are based on the directions or positional relationships shown in the drawings, which are for convenience of description only, and do not indicate or imply that the device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

First, referring to fig. 2, the overall architecture of the PFC module of the present embodiment will be described in detail.

As shown in fig. 2, the PFC module of the present embodiment includes a housing 100, and two rows of pins are disposed on the housing 100 and are respectively disposed on two opposite sides of the housing 100, such as a first side 101 and a second side 102 in fig. 2. The first side 101 is used for arranging high-voltage terminals and comprises a direct-current output end P, G for outputting high-voltage direct-current power and alternating-current input ends AC1 and AC2 for externally connecting an alternating-current power supply AC. The second side 102 IS used for laying low-voltage terminals, and includes an upper bridge control signal input pin HIN, a lower bridge control signal input pin LIN, alarm signal output pins Fo and Cs, a sampling current output pin IS, a lower bridge high-voltage power supply input pin VD, an upper bridge high-voltage power supply pin Vc, an upper bridge drive reference voltage pin Vg, a ground pin Gnd, and the like. Therefore, the PFC module can be arranged on the electric control board in a dual-in-line mode when in use, so that the design and the processing of the electric control board are simplified.

A PFC circuit is enclosed in a casing 100 of the PFC module, and includes four rectifier diodes V103-V106, two power switching tubes V101 and V102, a sampling resistor Rs, an upper bridge driving circuit, a lower bridge driving circuit, and other main components. The rectifier diodes V103 and V105 are upper bridge rectifier diodes, are connected to the positive electrode P of the dc output terminal of the PFC module, and are respectively defined as a first upper bridge rectifier diode V103 and a second upper bridge rectifier diode V105; rectifier diodes V104 and V106 are lower bridge rectifier diodes, are connected with a negative electrode G of a direct current output end of the PFC module, and are respectively defined as a first lower bridge rectifier diode V104 and a second lower bridge rectifier diode V106; the two power switch tubes V101 and V102 are respectively connected in parallel with the first upper bridge rectifier diode V103 and the first lower bridge rectifier diode V104, and are respectively defined as an upper bridge power switch tube V101 and a lower bridge power switch tube V102.

In this embodiment, preferably, the cathode of the first upper bridge rectifier diode V103 is connected to the anode P of the dc output terminal of the PFC module, the anode is connected to the live wire pin AC1 of the AC input terminal, and is externally connected to the inductor L101 through the live wire pin AC1, and is connected to the AC power source AC through the inductor L101, for example, connected to the live wire L of the AC power source AC. Of course, the inductor L101 may be disposed inside the casing 100 of the PFC module, that is, the anode of the first upper bridge rectifier diode V103 is connected to the live wire pin AC1 of the AC input terminal through the inductor L101, and is externally connected to the live wire L of the AC power source AC through the live wire pin AC 1. The cathode of the second upper bridge rectifier diode V105 is connected to the anode P of the DC output end of the PFC module, the anode is connected to the zero line pin AC2 of the AC input end, and is connected to the zero line N of the AC power supply AC through the zero line pin AC 2. The cathode of the first lower bridge rectifier diode V104 is connected to the anode of the first upper bridge rectifier diode V103, and the anode of the first lower bridge rectifier diode V104 is connected to the anode of the second lower bridge rectifier diode V106 through the sampling resistor Rs, and then connected to the cathode G of the dc output terminal of the PFC module. The cathode of the second lower bridge rectifier diode V106 is connected to the zero line pin AC2 of the AC input terminal, that is, the cathode of the second lower bridge rectifier diode V106 is connected to the anode of the second upper bridge rectifier diode V105, and the anode of the second lower bridge rectifier diode V106 is connected to the negative electrode G of the dc output terminal of the PFC module.

In this embodiment, the four rectifier diodes V103-V106 are connected to form a bridge rectifier circuit, so that the PFC module of this embodiment does not need an external rectifier bridge when in use, and thus the PFC module of this embodiment may be referred to as a "bridgeless" PFC module.

In order to realize power factor correction while alternating current-direct current conversion, in this embodiment, an upper bridge power switching tube V101 is connected in parallel to two ends of a first upper bridge rectifier diode V103, a lower bridge power switching tube V102 is connected in parallel to two ends of a first lower bridge rectifier diode V104, and the two power switching tubes V101 and V102 may be power semiconductor switching devices such as IGBTs or MOSFETs. Taking an IGBT power switch tube as an example for explanation, a collector of the upper bridge power switch tube V101 is connected to a cathode of the first upper bridge rectifier diode V103, an emitter of the upper bridge power switch tube V101 is connected to an anode of the first upper bridge rectifier diode V103, and a switching path of the upper bridge power switch tube V101 is connected in parallel with the first upper bridge rectifier diode V103; meanwhile, the gate of the upper bridge power switching tube V101 is connected to the upper bridge driving circuit, and the on-off control of the upper bridge power switching tube V101 is performed by using the upper bridge driving signal Hi output by the upper bridge driving circuit. Similarly, the collector of the lower bridge power switch tube V102 is connected to the cathode of the first lower bridge rectifier diode V104, the emitter of the lower bridge power switch tube V102 is connected to the anode of the first lower bridge rectifier diode V104, and the switching path of the lower bridge power switch tube V102 is connected in parallel with the first lower bridge rectifier diode V104; meanwhile, the gate of the lower bridge power switching tube V102 is connected to the lower bridge driving circuit, and is turned on and off under the control of a lower bridge driving signal Li output by the lower bridge driving circuit.

In the PFC module of this embodiment, the first upper bridge rectifier diode V103, the first lower bridge rectifier diode V104, the upper bridge power switch tube V101, and the lower bridge power switch tube V102 should be high-frequency fast recovery diodes and high-frequency power switch devices having high-speed switching characteristics at the same level, and the second upper bridge rectifier diode V105 and the second lower bridge rectifier diode V106 may be low-frequency diodes for power rectification.

When the PFC module of the present embodiment is used, the AC input terminals AC1 and AC2 of the PFC module are connected to the AC power supply AC, and the inductor L101 is connected in series to the live line transmission line; a large-capacity energy storage capacitor C101 is connected in parallel with a direct current output end P, N of the PFC module, and a load is connected to the rear stage of the energy storage capacitor C101; and a main control chip IS externally connected to the upper bridge control signal input pin HIN, the lower bridge control signal input pin LIN and the sampling current output pin IS to form a complete system circuit.

In order to synchronize the current waveform with the voltage waveform of the external AC power supply AC to improve the power factor of the power supply, an AC detection circuit is disposed outside the PFC module in this embodiment, and detects the voltage signal Vac of the AC power supply AC and sends the voltage signal Vac to the main control chip. And, set up current signal sampling point A at the connecting node of sampling resistor Rs and first lower bridge rectifier diode V104, gather current signal Is of current signal sampling point A, and send to the main control chip through sampling current output pin IS of PFC module. The main control chip judges the zero crossing point and the positive and negative half-cycle polarity of the alternating voltage according to the collected voltage signal Vac of the alternating current power supply AC, substitutes the collected voltage signal Vac and the collected current signal Is into a conventional PFC control algorithm to generate an upper bridge control signal Hin and a lower bridge control signal Lin, respectively and correspondingly transmits the upper bridge control signal input pin HIN and the lower bridge control signal input pin LIN of the PFC module to an upper bridge driving circuit and a lower bridge driving circuit in the PFC module, generates an upper bridge driving signal Hi through the upper bridge driving circuit to control the on-off of an upper bridge power switching tube V101, generates a lower bridge driving signal Li through the lower bridge driving circuit to control the on-off of a lower bridge power switching tube V102, so that the current waveform can follow the voltage waveform of the alternating current power supply AC to synchronously change in a sinusoidal manner, and further achieve the purpose of power factor correction.

Specifically, during the positive half cycle of the alternating voltage, the upper bridge control signal Hin of the main control chip controls the upper bridge driving circuit to close the upper bridge power switch tube V101; meanwhile, the output lower bridge control signal Lin controls the lower bridge driving circuit to output a pulse lower bridge driving signal Li, controls the on-off of the lower bridge power switch tube V102, and during the on-off period of the lower bridge power switch tube V102, the main control chip collects a current signal IS of a current signal sampling point A through a sampling circuit output pin IS. During the negative half cycle of the alternating-current voltage, the main control chip outputs a lower bridge control signal Lin to control a lower bridge driving circuit to close a lower bridge power switch tube V102; meanwhile, the output upper bridge control signal Hin controls the upper bridge driving circuit to output a pulse-type upper bridge driving signal Hi so as to control the on-off of the upper bridge power switching tube V101, and the main control chip collects a current signal IS of a current signal sampling point A through a sampling circuit output pin IS during the closing period of the upper bridge power switching tube V101. The main control chip substitutes the collected current signal Is and the collected voltage signal Vac into a PFC control algorithm to adjust an upper bridge control signal Hin and a lower bridge control signal Lin output by the main control chip, and then the PFC module Is controlled by the main control chip to enable the current waveform to be synchronous with the voltage waveform of the AC power supply. The PFC control algorithm is a well-known classical PFC algorithm, and is not described here.

The operation principle of the PFC module of the present embodiment is described in detail with reference to fig. 3 to 6.

After the PFC module is connected to the AC power supply AC, the main control chip first receives the voltage signal Vac collected by the AC detection circuit, and determines the zero crossing point and the positive and negative half-cycle polarities of the AC voltage.

During the positive half cycle of the alternating voltage, the main control chip outputs an upper bridge control signal Hin for controlling the upper bridge power switch tube V101 to be kept turned off and a lower bridge control signal Lin for controlling the lower bridge power switch tube V102 to be continuously turned on and off. Wherein the content of the first and second substances,

during the controlled conduction of the lower bridge power switch tube V102, the circulation path of the circuit current is as shown in fig. 3: from a live wire L of an alternating current power supply AC, the voltage returns to a zero line N of the alternating current power supply AC through an inductor L101, a lower bridge power switch tube V102, a sampling resistor Rs and a second lower bridge rectifier diode V106. And collecting a current signal Is of the current signal sampling point A and sending the current signal Is to the main control chip. During the period, the inductor L101 is charged in a short circuit mode until the lower bridge power switch tube V102 is controlled to be turned off, and a free-wheeling process is carried out.

During the off period of the lower bridge power switch tube V102, the circulation path of the circuit current is as shown in fig. 4: from a live wire L of the alternating current power supply AC, the voltage returns to a zero line N of the alternating current power supply AC through an inductor L101, a first upper bridge rectifier diode V103, an energy storage capacitor C101, a load and a second lower bridge rectifier diode V106. Since the current does not pass through the sampling resistor Rs, the current signal Is = 0. During this time, the inductor L101 discharges energy to the subsequent stage.

Therefore, the main control chip continuously controls the lower bridge power switch tube V102 to be switched on and off by matching with the lower bridge driving circuit during the positive half cycle of the alternating voltage, and further continuously performs charging and discharging control on the inductor L101 until the positive half cycle of the alternating voltage is finished and the negative half cycle of the alternating voltage is controlled.

During the negative half cycle of the alternating voltage, the main control chip outputs a lower bridge control signal Lin for controlling the lower bridge power switch tube V102 to be kept turned off and an upper bridge control signal Hin for controlling the upper bridge power switch tube V101 to be continuously turned on and off. Wherein the content of the first and second substances,

during the controlled conduction of the upper bridge power switch V101, the circulation path of the circuit current is as shown in fig. 5: from a zero line N of the alternating current power supply AC, the alternating current power supply returns to a live line L of the alternating current power supply AC through a second upper bridge rectifier diode V105, an upper bridge power switch tube V101 and an inductor L101. Since the current does not pass through the sampling resistor Rs, the current signal Is = 0. During the period, the inductor L101 is charged in a short circuit mode until the upper bridge power switch tube V101 is controlled to be turned off, and a free-wheeling process is carried out.

During the off period of the upper bridge power switch tube V101, the circulation path of the circuit current is as shown in fig. 6: from a zero line N of the alternating current power supply AC, the zero line N returns to a live line L of the alternating current power supply AC through a second upper bridge rectifier diode V105, an energy storage capacitor C101, a load, a sampling resistor Rs, a first lower bridge rectifier diode V104 and an inductor L101. And collecting a current signal Is of the current signal sampling point A and sending the current signal Is to the main control chip. During this time, the inductor L101 discharges energy to the rear stage load.

Therefore, the main control chip continuously controls the on and off of the upper bridge power switch tube V101 during the negative half cycle of the alternating voltage by matching with the upper bridge driving circuit, and further continuously performs charge and discharge control on the inductor L101 until the negative half cycle of the alternating voltage is finished, and then enters the positive half cycle control of the alternating voltage again.

Fig. 7 is a current waveform of a current signal sampling point a when the alternating voltage varies within one cycle. As can be seen from fig. 7, during the positive half cycle of the ac voltage, the current passing through the current signal sampling point a is the charging current, so the current is gradually increased in the single current pulse waveform; during the negative half cycle of the ac voltage, the current passing through sample point a of the current signal is a freewheeling current, so the current is decreasing in a single current pulse waveform. The main control chip is designed to extract a current value corresponding to a middle time (such as t1, t2, t3, k1, k2, k3 and the like in fig. 7) of each sampling period, and the current value is used as an input signal of a PFC control algorithm to match with a voltage signal Vac of the AC power supply AC, so as to adjust the cycle and/or duty ratio of an upper bridge control signal Hin and a lower bridge control signal Lin output by the PFC control algorithm, so that a current waveform can be synchronized with a voltage waveform of the AC power supply AC, such as a sinusoidal waveform shown by a dotted line in fig. 7.

In order to better detect the sampling current Is, the sampling current Is may be properly amplified by an amplifying circuit and then transmitted to the main control chip.

Because the circuit current flows through the sampling resistor Rs during the conduction period of the lower bridge power switch tube V102, the main control chip can judge whether the current flowing through the lower bridge power switch tube V102 Is too high according to the current signal Is, and when the current signal Is detected to exceed a set threshold value, the lower bridge control signal Lin Is stopped being output to control the lower bridge power switch tube V102 to be switched off, so that the overcurrent protection of the lower bridge power switch tube V102 Is realized.

For the upper bridge power switch tube V101, no current flows through the sampling resistor Rs during the on period of the upper bridge power switch tube V101, so as to avoid overcurrent damage of the upper bridge power switch tube V101, in this embodiment, an upper bridge current sampling device is additionally arranged in the PFC module, and is packaged in the housing 100, and the upper bridge current sampling device is used to collect the current Isw flowing through the upper bridge power switch tube V101 and transmit the current Isw to the upper bridge driving circuit. When detecting that the current flowing through the upper bridge power switching tube V101 is greater than a set threshold value, the upper bridge driving circuit can control the upper bridge power switching tube V101 to be turned off, so that overcurrent protection is performed on the upper bridge power switching tube V101, and the working reliability of the PFC module is improved.

As a preferred design scheme of the upper bridge driving circuit and the lower bridge driving circuit, the upper bridge driving circuit and the lower bridge driving circuit of this embodiment mainly include an interface unit, a control unit, an upper bridge driving unit, an overcurrent protection unit, a lower bridge driving unit, and the like, as shown in fig. 8. The upper bridge driving unit comprises two super junction MOS tubes Q103 and Q104, two pull-up resistors R101 and R102, an RS trigger N104 and an output driving circuit Q105. The trigger end S and the reset end R of the RS trigger N104 are respectively connected to a direct current power supply end VC of an upper bridge driving circuit through pull-up resistors R101 and R102, and are respectively controlled by switching signals through two super junction MOS tubes Q103 and Q104. The interface unit is connected with a low-voltage terminal of the PFC module, is connected with the main control chip through the low-voltage terminal, receives an upper bridge control signal Hin and a lower bridge control signal Lin output by the main control chip, and then generates two paths of upper bridge pulse signals Hin _1 and Hin _2 and two paths of lower bridge pulse signals Lin _1 and Lin _2 through conversion of the control unit. The two upper bridge pulse signals Hin _1 and Hin _2 respectively control the on-off of two super junction MOS tubes Q103 and Q104, so that a switch control signal consistent with an upper bridge driving signal Hi is generated through an output end Q of an RS trigger N104, and the upper bridge driving signal Hi is output to a gate pole of an upper bridge power switch tube V101 through an output driving circuit Q105 to control the on-off of the upper bridge power switch tube V101. The lower bridge driving unit mainly includes an RS flip-flop N105 and an output driving circuit Q106. The trigger end S and the reset end R of the RS trigger N105 respectively receive two lower bridge pulse signals Lin _1 and Lin _2 output by the control unit, output a switch control signal consistent with the lower bridge driving signal Li, and further output the lower bridge driving signal Li to a gate pole of the lower bridge power switch tube V102 through the output driving circuit Q106 to control the on-off of the lower bridge power switch tube V102.

In order to sample the current flowing through the upper bridge power switch tube V101, in this embodiment, an IGBT or MOSFET power semiconductor device with a mirror image sampling branch is used as the upper bridge power switch tube V101. According to the principle of the power semiconductor device, when the main device of the upper bridge power switch tube V101 flows the current Io from the point E2, the mirror sampling branch flows the current Iws from the point E1, the ratio of Io to Iws is a fixed value n, and n is a constant greater than 0. The current sampling device is provided with a sampling resistor Rsw connected between E1 and an upper bridge reference point VS (an intermediate node between an upper bridge power switch tube V101 and an inductor L101) for converting a sampling current Iws into a sampling voltage Vb.

When the bridge reference point VS is the reference point and the voltage at point E1 is Vb, the following steps are performed: vb = Rsw × Io/n. Assuming that the overcurrent protection value of Io is Io1, that is, a threshold is set, Vref2= Rsw × Io 1/n. When the current Io is larger than Io1, Vb > Vref2 turns off the upper bridge power switch tube V101, and overcurrent protection is performed.

In order to timely turn off the upper bridge power switching tube V101 when the current Io flowing through the upper bridge power switching tube V101 is greater than the set threshold Io1, the overcurrent protection unit of the embodiment is provided with a first comparator N103, an and gate 102, a delay circuit, a protection signal generation module, and other main components. The sampled voltage Vb is transmitted to the non-inverting input terminal + of the first comparator N103, the first reference voltage Vref2 is transmitted to the inverting input terminal of the first comparator N103, the output terminal of the first comparator N103 is connected to one of the input terminals of the and gate N102, the other input terminal of the and gate N102 receives the switch control signal output by the RS flip-flop N104, and the output terminal of the and gate N102 is connected to the delay circuit and the protection signal generation module.

When the current Io flowing through the upper bridge power switch tube V101 is not less than Io1 and Vb is not less than Vref2, the first comparator N103 outputs a low level (an invalid overcurrent detection signal), at this time, the and gate N102 outputs a low level no matter whether the switch control signal output by the RS flip-flop N104 is a high level or a low level, and the protection signal generation module does not output the overcurrent protection signal Iover. At the moment, the control unit normally operates, two paths of upper bridge pulse signals Hin _1 and Hin _2 are generated according to the received upper bridge control signal Hin, and an upper bridge driving signal Hi is normally output through the upper bridge driving unit to control the upper bridge switching tube V101 to be normally switched on and off.

Conversely, when the current Io > Io1 flowing through the upper bridge power switch V101, Vb > Vref2, the first comparator N103 outputs a high level (active overcurrent detection signal). At this time, when the switch control signal output by the RS flip-flop N104 is at a high level (when the upper bridge power switching tube V101 is turned on when the bridge driving signal Hi is at a high level), the and gate N102 outputs a high level, and on one hand, the high level is transmitted to the protection signal generation module, and on the other hand, the high level is transmitted to the delay circuit. When the duration of the high level output by the AND gate N102 reaches the set time, the delay circuit generates an overcurrent effective signal and sends the overcurrent effective signal to the protection signal generation module. And the protection signal generation module outputs an overcurrent protection signal Iover to the control unit under the condition that the overcurrent valid signal is received and the AND gate N102 keeps outputting a high level. At this time, the control unit stops outputting the upper bridge pulse signals Hin _1 and Hin _2, so that the upper bridge driving signal Hi is at a low level, and the upper bridge switching tube V101 is turned off, thereby realizing overcurrent protection.

In this embodiment, the time delay circuit is arranged in the overcurrent protection unit, and is used to effectively prevent the protection signal generation module from outputting the overcurrent protection signal Iover when the PFC circuit is interfered and the and gate N102 outputs a high level in a short time, so as to eliminate interference influence and improve the working reliability of the PFC module.

As a preferable design of the delay circuit, in the present embodiment, a constant current source a101, a second comparator N101 and a capacitor C102 are provided in the delay circuit. The constant current source A101 is connected with the output end of the AND gate N102, and outputs constant current to charge the capacitor C102 when the AND gate N102 outputs high level. The capacitor C102 is connected between the non-inverting input + of the second comparator N101, the inverting input-of the second comparator N101 receiving a second reference voltage Vref1, and the upper bridge reference point VS. When the and gate N102 continuously outputs the high level, the constant current source a101 continuously outputs the constant current to charge the capacitor C102, and when the time for the constant current source a101 to continuously output the constant current reaches the set time, the charging voltage on the capacitor C102 exceeds the second reference voltage Vref1, and at this time, the second comparator N101 outputs the effective overcurrent signal with the high level to the protection signal generating module. The protection signal generation module of this embodiment may be implemented by an integrated or discrete device such as a single chip or a nand gate, and outputs an overcurrent protection signal Iover to the control unit when receiving an effective overcurrent signal with a high level and the and gate N102 outputs a high level. A PMOS transistor Q101 and a switching transistor Q102 may be further connected between the protection signal generating module and the control unit, as shown in fig. 8, for converting the overcurrent protection signal Iover from high voltage to low voltage.

In this embodiment, when receiving the overcurrent protection signal Iover, the control unit generates an overcurrent alarm signal, and outputs the overcurrent alarm signal to the main control chip through an alarm signal output pin Fo arranged on the housing 100. When receiving the overcurrent alarm signal, the main control chip may stop outputting the upper bridge control signal Hin and the lower bridge control signal Lin, and control the PFC module to stop the PFC control process.

Since some electronic devices need to be powered by dc power during the operation of the upper bridge driving circuit, in order to ensure the reliable operation of the upper bridge driving circuit, a bootstrap diode V201 and a capacitor C201 are further disposed in the PFC module in this embodiment, as shown in fig. 8. Wherein, the anode of the bootstrap diode V201 is connected to the lower bridge high voltage power input pin VD on the housing 100, and receives the externally provided dc power; the cathode of the bootstrap diode V201 is connected to a dc power supply terminal VC of the upper bridge driving circuit, which is connected to an upper bridge high voltage power supply pin VC disposed on the housing 100. Electronic devices or electronic circuits in the upper bridge driving circuit, which need to be powered by direct current, can be connected to the direct current power supply end VC to obtain direct current power. The positive electrode of the capacitor C201 is connected to the direct current power supply end VC of the upper bridge driving circuit, and the negative electrode is connected to the connection node of the upper bridge power switch tube V101 and the lower bridge power switch tube V102, that is, the position of the upper bridge reference point VS. Of course, the capacitor C201 may also be disposed outside the housing 100 of the PFC module in an external connection manner, and connected between the upper bridge high voltage supply pin Vc and the upper bridge driving reference voltage pin Vg. The upper bridge drive reference voltage pin Vg is connected to the position of the upper bridge reference point VS inside the housing 100, as shown in fig. 2.

When the voltage of the alternating current power supply AC is in the positive half cycle, the upper bridge power switch tube V101 does not operate, and during the conduction period of the lower bridge power switch tube V102, the negative electrode of the capacitor C201 is connected to the reference ground through the lower bridge power switch tube V102 (the negative electrode G of the dc output end of the PFC module is connected to the reference ground). At this time, the capacitor C201 is charged by the dc power supply connected from the input pin VD of the lower bridge high voltage power supply through the bootstrap diode V201, and a required dc power supply is provided for the upper bridge driving circuit. During the turn-off period of the lower bridge power switch tube V102, the voltage at the cathode of the capacitor C201 is raised, the bootstrap diode V201 is turned off, so that the direct current power supply end VC of the upper bridge driving circuit is isolated from the input pin VD of the lower bridge high voltage power supply, and at the moment, the capacitor C201 discharges to provide the required direct current power supply for the upper bridge driving circuit.

When the voltage of the alternating current power supply AC is in a negative half cycle, the lower bridge power switch tube V102 does not work, and the bootstrap diode V201 is switched off during the conduction period of the upper bridge power switch tube V101, and the electric energy output by the capacitor C201 is used for supplying power to the upper bridge driving circuit. During the turn-off period of the upper bridge power switch tube V101, the first lower bridge rectifier diode V104 is in a freewheeling state, at this time, the negative electrode of the capacitor C201 is communicated with the reference ground, and the direct current power supply connected from the lower bridge high voltage power supply input pin VD charges the capacitor C201 through the bootstrap diode V201 and provides direct current power supply for the upper bridge driving circuit.

Therefore, the voltage of the DC power supply end VC can be maintained to be stable, and a stable DC power supply is provided for the upper bridge driving circuit.

In order to reduce the inrush current of the bootstrap diode V201, in this embodiment, a diode, which is equivalent to a current-limiting resistor integrated in series and having a resistance value smaller than 200 Ω, is preferably used as the bootstrap diode V201, so as to further improve the reliability of the operation of the PFC module.

For the overcurrent protection of the lower bridge power switch tube V102, in this embodiment, the main control chip IS used to receive the output of the PFC module through the sampling signal output pin IS, and if the current signal IS exceeds the set threshold, the main control chip may stop outputting the lower bridge control signal Lin to control the control unit to stop outputting the lower bridge pulse signals Lin _1 and Lin _2, so as to control the lower bridge driving unit to turn off the lower bridge power switch tube V102 and enter the overcurrent protection state.

The dc power supply required by the electronic devices or circuits in the under-bridge driving circuit can be directly provided by the dc power supply connected through the under-bridge high-voltage power supply input pin VD.

In addition, an upper bridge power supply under-voltage protection circuit can be further arranged in the upper bridge driving circuit, a lower bridge power supply under-voltage protection circuit can be further arranged in the lower bridge driving circuit, and a temperature detection circuit can be further integrated in the PFC module so as to improve the working reliability of the PFC module.

The invention adopts the modularized design for the PFC circuit, has high integration level, does not need an external rectifier bridge, and has more compact circuit and high power density. In addition, the invention adopts a dual in-line pin packaging structure for the PFC module, and separates the high-voltage terminal and the low-voltage terminal to be respectively arranged at two opposite sides of the PFC module, thereby not only facilitating the PCB wiring and processing of the electric control board, but also effectively solving the problem of electromagnetic interference generated by the high-voltage signal to the low-voltage signal and being beneficial to improving the reliability of the operation of a system circuit.

Of course, the above embodiments are only used for illustrating the technical solution of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A PFC module, comprising:

the device comprises a shell, a power supply and a control circuit, wherein the shell comprises a first side and a second side which are in relative position relation, a direct current output end and an alternating current input end are arranged on the first side, and an upper bridge control signal input pin, a lower bridge control signal input pin and a sampling current output pin are arranged on the second side; the following circuits are enclosed in the housing:

the alternating current side of the bridge rectifier circuit is connected with the alternating current input end, the direct current side of the bridge rectifier circuit is connected with the direct current output end, and the bridge rectifier circuit comprises two upper bridge rectifier diodes and two lower bridge rectifier diodes; one of the upper bridge rectifier diodes and the lower bridge rectifier diode connected with the upper bridge rectifier diode are respectively connected with a power switch tube in parallel, and the power switch tubes are correspondingly an upper bridge power switch tube and a lower bridge power switch tube;

the sampling resistor is connected between the anodes of the two lower bridge rectifier diodes, and a current signal sampling point is arranged at the connecting node of the sampling resistor and the lower bridge rectifier diodes connected with the power switch tube in parallel and is connected with a sampling current output end;

the upper bridge driving circuit is connected with the upper bridge control signal input pin and is used for controlling the on-off of the upper bridge power switch tube according to the received upper bridge control signal;

the lower bridge driving circuit is connected with the lower bridge control signal input pin and is used for controlling the on-off of the lower bridge power switch tube according to the received lower bridge control signal;

the upper bridge current sampling device is used for collecting the current flowing through the upper bridge power switch tube, converting the current into sampling voltage and transmitting the sampling voltage to the upper bridge driving circuit;

when the PFC module is used, an alternating current input end of the PFC module is externally connected with an alternating current power supply, and an inductor is connected in series in a transmission line of the alternating current power supply; the upper bridge control signal input pin, the lower bridge control signal input pin and the sampling current output pin are externally connected with a main control chip and used for receiving an upper bridge control signal and a lower bridge control signal output by the main control chip; the main control chip controls the upper bridge power switch tube to be closed and controls the lower bridge power switch tube to be switched on and off during the positive voltage half cycle of the alternating current power supply, and current signals are collected through the sampling current output pin during the switching-on period of the lower bridge power switch tube; during the negative half cycle of the voltage of the alternating current power supply, the lower bridge power switch tube is controlled to be closed, the upper bridge power switch tube is controlled to be switched on and off, and a current signal is collected through the sampling current output pin during the closing of the upper bridge power switch tube; the main control chip combines the collected current signal and the voltage signal of the alternating current power supply and carries out PFC control on the PFC module according to a PFC control algorithm;

the upper bridge driving circuit includes:

the first comparator receives the sampling voltage output by the upper bridge current sampling device, compares the sampling voltage with a first reference voltage and outputs an effective overcurrent detection signal with a high level;

the AND gate receives the overcurrent detection signal output by the first comparator and performs AND operation with an upper bridge driving signal, and the level state of the upper bridge driving signal when the upper bridge driving signal drives the upper bridge power switch tube to be conducted is high level;

the constant current source is connected with the output end of the AND gate and outputs constant current when the AND gate outputs high level;

the capacitor is connected with the constant current source, receives the constant current output by the constant current source for charging, and when the constant current source continuously outputs the constant current for a set time, the voltage of the capacitor exceeds a second reference voltage;

the second comparator is connected with the capacitor, compares the capacitor voltage with the second reference voltage, and outputs an overcurrent valid signal when the capacitor voltage exceeds the second reference voltage;

the protection signal generation module is connected with the output end of the AND gate and the delay circuit, and outputs an overcurrent protection signal when receiving the overcurrent effective signal and the AND gate keeps outputting a high level;

the control unit receives an upper bridge control signal output by the main control chip and controls the driving unit to generate the upper bridge driving signal according to the upper bridge control signal; and when receiving the overcurrent protection signal, the control unit controls the driving unit to close the upper bridge power switch tube to execute overcurrent protection.

2. The PFC module of claim 1,

the two upper bridge rectifier diodes are respectively:

the cathode of the first upper bridge rectifier diode is connected with the anode of the direct current output end, the anode of the first upper bridge rectifier diode is connected with a live wire pin of the alternating current input end, and the live wire pin is connected with an alternating current power supply through the inductor when the PFC module is used;

the anode of the second upper bridge rectifier diode is connected with the zero line pin of the alternating current input end, and the cathode of the second upper bridge rectifier diode is connected with the anode of the direct current output end;

the cathode of the second lower bridge rectifier diode is connected with the zero line pin of the alternating current input end, and the anode of the second lower bridge rectifier diode is connected with the cathode of the direct current output end;

the cathode of the first lower bridge rectifier diode is connected with the anode of the first upper bridge rectifier diode, and the anode of the first lower bridge rectifier diode is connected with the anode of the second lower bridge rectifier diode through the sampling resistor and then is connected with the cathode of the direct current output end;

the upper bridge power switch tube is connected with the first upper bridge rectifier diode in parallel; the lower bridge power switch tube is connected with the first lower bridge rectifier diode in parallel; the first upper bridge rectifier diode, the first lower bridge rectifier diode and the two power switch tubes have high-speed switching characteristics at the same level, and the second upper bridge rectifier diode and the second lower bridge rectifier diode are low-frequency diodes for power frequency rectification.

3. The PFC module of claim 1,

the main control chip detects a voltage signal of an alternating current power supply through an alternating current detection circuit, and substitutes the acquired current signal and voltage signal into a conventional PFC control algorithm to generate an upper bridge control signal and a lower bridge control signal;

the upper bridge driving circuit generates an upper bridge driving signal according to the received upper bridge control signal and sends the upper bridge driving signal to the upper bridge power switching tube so as to control the on-off of the upper bridge power switching tube;

and the lower bridge driving circuit generates a lower bridge driving signal according to the received lower bridge control signal and sends the lower bridge driving signal to the lower bridge power switch tube so as to control the on-off of the lower bridge power switch tube.

4. The PFC module of claim 1, wherein an alarm signal output pin is further provided at the second side of the housing; and when receiving the overcurrent protection signal, the control unit generates an overcurrent alarm signal and outputs the overcurrent alarm signal through the alarm signal output pin.

5. The PFC module of any of claims 1 to 3, further comprising:

the lower bridge high-voltage power supply input pin receives an external direct-current power supply and is connected with the anode of a bootstrap diode;

the upper bridge high-voltage power supply pin is connected with a direct-current power supply end of an upper bridge driving circuit, the direct-current power supply end is connected with a cathode of the bootstrap diode, and the upper bridge driving circuit obtains a direct-current power supply required by the operation of the upper bridge driving circuit from the direct-current power supply end;

and the upper bridge driving reference voltage pin is connected with a connection node of the upper bridge power switch tube and the lower bridge power switch tube and is connected with the upper bridge high-voltage power supply pin through another capacitor.

6. The PFC module of claim 5, wherein the bootstrap diode is an internal equivalent diode integrated with a current limiting resistor connected in series and having a resistance of less than 200 Ω.

7. The PFC module of claim 5, wherein the another capacitor is external to the housing.