CN218850621U

CN218850621U - PFC switching circuit

Info

Publication number: CN218850621U
Application number: CN202221489008.5U
Authority: CN
Inventors: 邓俊高
Original assignee: Shenzhen Qianhai Shouke Technology Holdings Co ltd
Current assignee: Shenzhen Qianhai Shouke Technology Holdings Co ltd
Priority date: 2022-06-14
Filing date: 2022-06-14
Publication date: 2023-04-11
Anticipated expiration: 2032-06-14

Abstract

The utility model discloses a PFC switching circuit, which comprises a PFC circuit and a DC-DC conversion unit circuit, wherein the PFC switching circuit also comprises an output power detection control unit circuit; the output power detection control unit circuit is internally provided with a direct current power metering singlechip U6 which is connected with a power supply secondary end in the PFC circuit and is used for detecting the output power of the power supply secondary end; when the detection result of the output power of the secondary end of the power supply detected by the direct-current power metering singlechip U6 is larger than or equal to a value a, the PFC circuit works normally; when the detection result of the output power of the secondary end of the power supply is detected through the direct current power metering single chip microcomputer U6, the value < a, the direct current power metering single chip microcomputer U6 outputs a high level signal and closes the working power supply of the PFC circuit through a control loop, and the PFC circuit stops working. The utility model discloses a PFC switching circuit not only promotes the average efficiency of high-power supply product, reduces the unloaded consumption of complete machine, for end user practices thrift the electric energy, and energy saving and emission reduction promotes user's use and experiences.

Description

PFC switching circuit

Technical Field

The utility model relates to a switching circuit, specific theory relate to a PFC switching circuit.

Background

In the present high frequency switching power supply product, according to the requirements of international electrotechnical commission 61000-3-2 or related national standards, the output power is greater than or equal to 75W, and the harmonic current distortion must be less than a certain standard requirement, therefore, when designing such power supply product, a power factor correction circuit is generally added at the input part, and the common method is to add an active power factor correction controller to meet the standard requirements. However, the circuit is lossy, so that no-load power consumption can be increased, the average efficiency of the whole power supply product can be reduced, and energy conservation and emission reduction are not facilitated. Based on the control circuit, a power supply product with the power consumption of 75W or more is enabled to enter a PFC function mode when the power supply product with the power consumption of 75W or more is enabled to enter the PFC function mode, and the PFC function is turned off when the power supply product with the power consumption of 75W or more is enabled to be less than 75W, so that energy conservation and emission reduction are achieved, and the national standard requirements of the product are met.

The PFC correction circuit of the prior art has several forms, and the present invention only describes the boost type active power factor correction circuit related to the present application.

As shown in FIGS. 1-2, the PFC control circuit in the prior art is formed by connecting FIG. 1 and FIG. 2 according to A1-A1, A2-A2 and A3-A3. In the PFC control circuit diagram of the prior art, an input mains supply is rectified and then converted into a pulsating direct current voltage, and the pulsating direct current voltage is switched by a power factor correction controller at a switching speed about 500 times a pulsating frequency within each pulsating direct current voltage period, so that an input current basically follows the input voltage, and the purpose of reducing harmonic current distortion is achieved.

No matter the output load of the circuit is large, the PFC control circuit works, and power loss is generated when the circuit works, so that the average efficiency of the whole power supply is reduced, and the no-load power consumption of the power supply is increased.

In the prior art, no matter the output load of the PFC control circuit is large, the PFC control circuit works, and power loss is generated when the circuit works, so that the average efficiency of the whole power supply is reduced, the no-load power consumption of the power supply is increased, energy saving and carbon reduction are not facilitated, and the 2 parameters exceed the standard requirements seriously, and become unqualified products to cause economic loss.

SUMMERY OF THE UTILITY MODEL

To the deficiency among the prior art, the utility model discloses the technical problem who solves provides a PFC switching circuit.

In order to solve the technical problem, the utility model discloses a following scheme realizes: the utility model discloses a PFC switching circuit, this PFC switching circuit include PFC circuit and with the DC-DC conversion unit circuit that PFC circuit is connected, PFC switching circuit still includes output power detection control unit circuit;

the output power detection control unit circuit is internally provided with a direct current power metering singlechip U6 which is connected with a power supply secondary end in the PFC circuit and is used for detecting the output power of the power supply secondary end;

when the detection result of the output power of the secondary end of the power supply detected by the direct-current power metering singlechip U6 is larger than or equal to a value a, the PFC circuit works normally;

when the detection result of the direct current power measurement single chip microcomputer U6 for detecting the output power of the secondary end of the power supply is smaller than a value, the direct current power measurement single chip microcomputer U6 outputs a high level signal and closes the working power supply of the PFC circuit through a control loop, and the PFC circuit stops working.

Further, a 16-pin VDD end of the direct-current power metering singlechip U6 is connected to a 5V power supply and a capacitor C19, and the other end of the capacitor C19 is grounded;

the 15-pin INT2 end of the direct-current power metering single chip microcomputer U6 is connected with a resistor R35, the other end of the resistor R35 is connected to the grid electrode of a transistor Q5, the source electrode of the transistor Q5 is grounded, and the drain electrode of the transistor Q5 is connected to the negative electrode of the light emitting end of an optocoupler U5;

the positive electrode of the light emitting end of the optocoupler U5 is connected with a resistor R32, the other end of the resistor R32 is connected to the negative output voltage Vo-of the DC-DC conversion unit circuit, the emitter of the light receiving end of the optocoupler U5 is grounded, and the collector of the light receiving end of the optocoupler U5 is connected to the grid of the transistor Q2;

the drain electrode of the transistor Q2 is connected to the secondary power supply end VDD of the PFC circuit;

an IAP (integrated circuit board) end of a pin 1 of the direct-current power metering single chip microcomputer U6 is connected to an IAP (integrated circuit board) input pin of the DC-DC conversion unit circuit, an IAN (integrated circuit board) end of a pin 2 of the direct-current power metering single chip microcomputer U6 is connected to an IAN input pin of the DC-DC conversion unit circuit, the IAP end of the pin 1 is connected with a capacitor C18, the other end of the capacitor C18 is connected with a capacitor C17 and is grounded, and the other end of the capacitor C17 is connected to the IAN end of the pin 2;

a 5 pin VP end of the direct current power metering single chip microcomputer U6 is connected to a positive electrode output voltage Vo + of the DC-DC conversion unit circuit;

a 6-pin GND end of the direct-current power metering singlechip U6 is connected to a grounding end of the capacitor C18, the 6-pin GND end is also connected with a capacitor C20, and the other end of the capacitor C20 is connected to a 5-pin VP end;

the VREFF end of the 7 pin of the direct current power metering single chip microcomputer U6 is connected with a capacitor C21, and the other end of the capacitor C21 is connected to the GND end of the 6 pin.

Further, in the DC-DC conversion unit circuit, a resistor R30 is connected between an IAP input pin and an IAN input pin, wherein the IAN input pin is connected to a negative output voltage Vo-in the DC-DC conversion unit circuit.

Further, a =60 to 100 watts.

Further, the a =75 watts.

Compared with the prior art, the beneficial effects of the utility model are that: the utility model discloses a PFC switching circuit not only promotes the average efficiency of high-power supply product, reduces the unloaded consumption of complete machine, for end user practices thrift the electric energy, and energy saving and emission reduction promotes user's use and experiences.

The switching circuit of the utility model adopts a direct current power metering singlechip and is placed at the secondary level of a power supply, when the direct current power metering singlechip U6 detects that the output power of the secondary level is more than or equal to a set value, a PFC controller works normally; when the direct-current power metering single chip microcomputer U6 detects that the output power of the secondary stage is smaller than a set value, the direct-current power metering single chip microcomputer U6 outputs a high-level signal, the PFC working power supply is turned off through a control loop, and the whole PFC working circuit stops working, so that the purposes of improving the light-load efficiency of the whole machine and reducing the no-load power consumption of the whole machine are achieved.

Drawings

Fig. 1 and fig. 2 are connected to form a PFC control circuit in the prior art.

Fig. 3 shows the pulsating dc voltage waveform of AC power after rectification and filtering.

Fig. 4 shows the pulse VD dc voltage and current waveform of the PFC circuit of the present invention.

Fig. 5 and 6 show the DC-DC conversion unit circuit of the present invention.

Fig. 7 shows the output power detection control unit circuit of the present invention.

Fig. 8 and 9 show the PFC circuit controlled by the power detection control unit according to the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making more clear and definite definitions of the protection scope of the present invention. It is obvious that the described embodiments of the invention are only some of the embodiments of the invention, and not all of them. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Furthermore, the technical features mentioned in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Example 1: the utility model discloses a concrete structure as follows:

referring to fig. 3-9, the PFC switching circuit of the present invention includes a PFC circuit and a DC-DC conversion unit circuit connected to the PFC circuit, and the PFC switching circuit further includes an output power detection control unit circuit;

A preferred technical solution of this embodiment: a 16-pin VDD end of the direct-current power metering singlechip U6 is connected with a 5V power supply and a capacitor C19, and the other end of the capacitor C19 is grounded;

the 15 pin INT2 end of the direct current power metering single chip microcomputer U6 is connected with a resistor R35, the other end of the resistor R35 is connected to a grid electrode of a transistor Q5, a source electrode of the transistor Q5 is grounded, and a drain electrode of the transistor Q5 is connected to the negative electrode of a light emitting end of an optocoupler U5;

and the 7-pin VREFF end of the direct current power metering singlechip U6 is connected with a capacitor C21, and the other end of the capacitor C21 is connected to the 6-pin GND end.

A preferred technical solution of this embodiment: in the DC-DC conversion unit circuit, a resistor R30 is connected between an IAP input pin and an IAN input pin, wherein the IAN input pin is connected with a negative electrode output voltage Vo-in the DC-DC conversion unit circuit.

A preferred technical solution of this embodiment: the a =60 to 100 watts, and the a of the present embodiment is 75 watts.

Example 2:

the following is the working principle of the PFC switching circuit of the utility model:

as shown in fig. 8-9, the commercial power input port a capacitor CN1 and the a capacitor CL1 are connected to the commercial power, and then pass through the filter assembly composed of the capacitor CX2, the inductor FL1, the inductor FL2, the capacitor CX1, the capacitor CY1, and the capacitor CY2, enter the rectifier filter assembly composed of the rectifier BD1 and the rectifier BD2, and then pass through the inductor L1 and the capacitor C4 assembly to become the pulsating dc voltage VD.

The pulsating direct current voltage VD reaches a pin 8 of the main control chip U1 through the resistor R5, flows out from a pin 1 of the main control chip U1 to charge the capacitor C8, when the charging voltage of the capacitor C8 reaches the starting voltage of the main control chip U1, the main control chip U1 starts to work, a pin 6 of the main control chip U1 outputs a switching-on pulse, and the transistor Q1 is driven to be switched on through the resistor R10; at this time, current flows from the positive electrode of the capacitor C4 through the inductor L2, the D electrode of the transistor Q1, the S electrode of the transistor Q1, the resistor R24, the resistor R25 and the resistor R26 to the PDNG primary ground, and along with the continuous increase of the current, the inductor L2 stores energy, the voltages of the resistor R24, the resistor R25 and the resistor R26 are continuously increased, pass through the capacitor C10, the resistor R14 and the capacitor C14, and are filtered to the pin 5 of the main control chip U1, when the pin 5 voltage of the main control chip U1 reaches a certain set voltage, the pin 6 of the main control chip U1 outputs a turn-off level, and the transistor Q1 is turned off; at this time, the energy stored in the inductor L2 flows out of the diode D2 in the form of a current, and charges the capacitor C3. Therefore, the positive terminal of the capacitor C3 outputs a positive voltage VBUS, which is provided to the DC-DC conversion unit circuit. And (4) turning on the pulse again until the pin 6 of the main control chip U1, and repeating the steps.

As shown in fig. 5-9, according to the VD voltage stabilization principle, when the DC-DC conversion unit circuit discharges, the VBUS voltage decreases, the voltage of the decreased signal is divided by the resistor R1, the resistor R2, and the resistor R3, the divided voltage VFB is transmitted to the pin 4 of the main control chip U1, the duty ratio of the output pulse of the pin 6 of the main control chip U1 is increased after the main control chip U1 detects the decreased signal, the on duty ratio of the transistor Q1 is increased, the energy stored in the inductor L2 is increased, and the energy transmitted to the output capacitor C3 is also increased; as the energy received by the capacitor C3 increases, the VBUS voltage increases, the voltage-increased signal is divided by the resistor R1, the resistor R2, and the resistor R3, the divided voltage VFB is transmitted to the 4 pins of the main control chip U1, the duty cycle of the output pulse of the 6 pins of the main control chip U1 is reduced after the main control chip U1 detects the increased signal, the on duty cycle of the transistor Q1 is reduced, the energy stored in the inductor L2 is reduced, and the energy transmitted to the output capacitor C3 is also reduced; as the energy received by the capacitor C3 decreases, the VBUS voltage decreases until a steady state of VBUS voltage is reached.

As shown in fig. 7, in each period of the pulsating voltage, the main control chip U1 continuously operates at a frequency of about 50KHz, so that the ac input current waveform completely tracks the ac input voltage waveform, the input current waveform is a pure sine wave and is in phase with the input voltage waveform, and the harmonic and reactive currents are eliminated, thereby increasing the power factor of the power supply to approximately 1, and at this time, the loads of the rectifier BD1 and the rectifier BD2 can be equivalent to a pure resistor.

As shown in fig. 8-9, the power factor correction circuit outputs a set dc high voltage VBUS on the capacitor C1 and the capacitor C2, and then the dc high voltage is converted into a dc low voltage required by the user through the transformer T1, the transistor Q4, the high frequency power switch controller U7, the transistor Q3, the synchronous rectification controller U3, the capacitor EC1, the capacitor EC2, the light emitting end of the optocoupler U2, and the voltage regulator U4. The detailed working process is as follows: the input commercial power flows out a starting current through a diode D3, a diode D4, a resistor R6, a resistor R7 and a high-frequency power switch controller U7, and a1 pin VDDH of the high-frequency power switch controller U7 to charge a capacitor EC3 and a capacitor C16, and when the VCC voltage meets the starting voltage of the high-frequency power switch controller U7, the high-frequency power switch controller U7 is started.

A 5 pin of a high-frequency power switch controller U7 outputs a switching-on pulse, and a transistor Q4 is driven to be conducted through a resistor R33; at the moment, current flows from the positive electrodes of the capacitor C1 and the capacitor C2 to the primary ground through a primary 1-2 pin of the transformer T1, a D electrode of the transistor Q4, an S electrode of the transistor Q4, a resistor R39 and a resistor R41, the transformer T1 stores energy along with the continuous increase of the current, the voltage of the resistor R39 continuously rises and is filtered and added to a 4 pin of the high-frequency power switch controller U7 through the resistor R37 and the capacitor C22, when a certain voltage set by the 4 pins is reached, a pin 5 of the high-frequency power switch controller U7 outputs a turn-off level, and the transistor Q4 is turned off; at this time, the energy stored in the transformer T1 flows out from the secondary 7 pins of the transformer T1 in the form of current, passes through the capacitor EC1, the positive electrode to the negative electrode of the capacitor EC2, reaches the S electrode of the transistor Q3, and the D electrode of the transistor Q3 returns to the 8 pins of the transformer T1; meanwhile, the synchronous rectification controller U3 is started, a turn-on pulse is output from the pin 5, the transistor Q3 is driven to be conducted through the resistor R23, the rectification power consumption of the transistor Q3 is reduced until the transistor Q4 is conducted again, and the steps are repeated. Therefore, the positive terminals of the capacitor EC1 and the capacitor EC2 output a positive voltage Vo to be supplied to the load.

According to the voltage stabilizing principle of the DC-DC converter, the voltage on an output filter capacitor EC1 and a capacitor EC2 is discharged through a load, the Vo voltage is reduced, the reduced voltage signal is transmitted to a pin 1 of a voltage regulator U4 through a resistor R16, a resistor R21 and a resistor R28 in a voltage dividing mode, the voltage regulator U4 detects the voltage reduction, the voltage of the pin 2 of the voltage regulator U4 is automatically regulated to be increased, the current flowing through the pin 1 of the optocoupler U2 and the pin 2 of the optocoupler U2 is reduced, the current flowing through a pin 4 of the optocoupler U2 and a pin 3 of the optocoupler U2 is also reduced at the moment, the pin 7 voltage of a high-frequency power switch controller U7 is increased, the pin 7 voltage is detected to be increased by the high-frequency power switch controller U7, the duty ratio of a 5 pin driving pulse of the high-frequency power switch controller U7 is automatically increased, the conduction time of a transistor Q4 is increased in each period, the stored energy of a transformer T1 is increased, the energy transmitted to a secondary stage is increased, and the output voltage Vo is increased; conversely, the Vo voltage rises, the voltage rising signal is divided by the resistor R16, the resistor R21 and the resistor R28 and transmitted to the pin 1 of the voltage regulator U4, the voltage regulator U4 detects the voltage rise, the voltage of the pin 2 of the voltage regulator U4 is automatically regulated to be reduced, the current flowing through the pin 1 of the optical coupler U2 and the pin 2 of the optical coupler U2 is increased, the current flowing through the pin 4 of the optical coupler U2 and the pin 3 of the optical coupler U2 is also increased, the voltage of the pin 7 of the high-frequency power switch controller U7 is reduced, the voltage of the pin 7 is reduced when detected by the high-frequency power switch controller U7, the duty ratio of the driving pulse of the pin 5 of the high-frequency power switch controller U7 is automatically reduced, the conduction time of the transistor Q4 in each period is reduced, the stored energy of the transformer T1 is reduced, the energy transmitted to the secondary is reduced, and the output voltage Vo is reduced until the Vo voltage reaches a stable state of the Vo voltage.

In fig. 7, after the normal voltage Vo and current Io are output, the dc power metering single-chip microcomputer U6 starts To operate, pin 5 of the dc power metering single-chip microcomputer U6 is connected To the output voltage Vo end, the output voltage Vo is detected, pin 1 IAP of the dc power metering single-chip microcomputer U6, pin 2 IAN of the dc power metering single-chip microcomputer U6 is connected To both ends IAP and IAN of the output current detection resistor R30, the output current Io flows through the resistor R30, voltage is generated at both ends of the resistor R30 and is applied To pin 1 IAP and pin 2 IAN of the dc power metering single-chip microcomputer U6, at this time, the MCU (single-chip microcomputer) of the dc power metering single-chip microcomputer U6 can have a result according To the detected output voltage Vo, output current To, and output power Po = Vo Io, and the MCU of the dc power metering single-chip microcomputer U6 sets 2 operating conditions, po <75W, and pin 15 of the dc power metering single-chip microcomputer U6 outputs a low level L; po > =75W, and the 15 pins of the direct current power metering singlechip U6 output a high level H.

When Po is less than 75W and 15 pins of a direct current power metering single chip microcomputer U6 output low level L, a transistor Q5 is turned off, no current flows through 1 pin of an optocoupler U5 and 2 pins of the optocoupler U5, meanwhile, 4 pins of the optocoupler U5 and 3 pins of the optocoupler U5 are also turned off, a grid electrode of a P-type transistor Q2 obtains voltage which is the same as that of a power supply port VCC through a resistor R15, a DS pin of the transistor Q2 is turned off, a D pin of the transistor Q2 does not obtain the voltage of the power supply port VCC, a pin VDD 1 of a main control chip U1 of a PFC control unit does not obtain the voltage of the power supply port VCC, the PFC control unit does not work due to the fact that the main control chip U1 does not work, the purpose of turning off the PFC control unit when the power output Po is less than 75W is achieved, power loss generated by the work of the PFC control unit is saved, and efficiency and no-load power consumption when Po is less than 75W are improved.

When Po > =75W, a high level H is output by a pin 15 of a direct current power metering single-chip microcomputer U6, a transistor Q5 is conducted, a current flows through a pin 1 of an optical coupler U5 and a pin 2 of the optical coupler U5, meanwhile, a pin 4 of the optical coupler U5 and a pin 3 of the optical coupler U5 are conducted, a grid electrode of a P-type transistor Q2 is pulled to a low level L, a pin DS of the transistor Q2 is conducted, a pin D of the transistor Q2 obtains the voltage of a power supply port VCC, a pin VDD 1 of a U1 of a PFC control unit also obtains the voltage of the power supply port VCC, a main control chip U1 of the PFC control unit starts to work, the purpose of starting the PFC control unit when the power output power Po > =75W is achieved, harmonic current reduction is achieved, and the standard requirements of the international electrotechnical commission 61000-3-2 or the relevant national standard requirements are met.

To sum up, the utility model discloses PFC switching circuit not only promotes the average efficiency of high-power supply product, reduces the unloaded consumption of complete machine, for end user practices thrift the electric energy, for earth energy saving and emission reduction, promotes user's use and experiences. The utility model discloses the technical key point is power calculation and control loop, promotes high-power supply product average efficiency, reduces the key technology node of the unloaded consumption of complete machine.

The above only is the preferred embodiment of the present invention, not limiting the scope of the present invention, all the equivalent structures or equivalent flow changes made by the contents of the specification and the drawings, or directly or indirectly applied to other related technical fields, are included in the same way in the protection scope of the present invention.

Claims

1. A PFC switching circuit comprises a PFC circuit and a DC-DC conversion unit circuit connected with the PFC circuit, and is characterized by further comprising an output power detection control unit circuit;

a 16-pin VDD end of the direct-current power metering singlechip U6 is connected with a 5V power supply and a capacitor C19, and the other end of the capacitor C19 is grounded;

the VREFF end of the 7 pin of the direct current power metering singlechip U6 is connected with a capacitor C21, and the other end of the capacitor C21 is connected to the GND end of the 6 pin;

in the DC-DC conversion unit circuit, a resistor R30 is connected between an IAP input pin and an IAN input pin, wherein the IAN input pin is connected with a negative electrode output voltage Vo-in the DC-DC conversion unit circuit.