CN212231332U

CN212231332U - Regulating circuit for reducing input surge current of switching power supply

Info

Publication number: CN212231332U
Application number: CN202021169765.5U
Authority: CN
Inventors: 涂必林; 杨智; 庄勤锋; 胡国勤; 季鹏
Original assignee: Mingzhi Electrical Appliances Taicang Co ltd
Current assignee: Mingzhi Electrical Appliances Taicang Co ltd
Priority date: 2020-06-22
Filing date: 2020-06-22
Publication date: 2020-12-25
Anticipated expiration: 2030-06-22

Abstract

The utility model relates to a reduce switching power supply input surge current's regulating circuit, this regulating circuit connects between PFC circuit and DCDC circuit, regulating circuit include electric capacity C1, electric capacity C2, silicon controlled Q1, resistance R1, diode D2 and power VCC, electric capacity C1 and electric capacity C2 connect between PFC circuit and DCDC circuit after connecting in parallel, resistance R1 connect between electric capacity C1 and electric capacity C2, diode D2's positive pole be connected with electric capacity C1, the negative pole is connected with electric capacity C2, silicon controlled Q1's positive pole be connected with electric capacity C2, the negative pole is connected with electric capacity C1, the control utmost point is connected with the power VCC. Compared with the prior art, the utility model has the advantages of the problem of silicon controlled rectifier SCR drive loss back damage power has been solved.

Description

Regulating circuit for reducing input surge current of switching power supply

Technical Field

The utility model relates to a switching power supply especially relates to a reduce switching power supply input surge current's regulating circuit.

Background

Normally, the startup surge current of the switching power supply is very large, and a common suppression scheme adopts an NTC with a small resistance value to limit the current, but the NTC has almost no limiting effect when the switching power supply is started in a hot state. After multiple power supplies are connected in parallel, the surge current is greatly superposed, and line burnout or circuit breaker tripping can be caused. Some special occasions, such as explosion-proof occasions, need to make strict restriction to the inrush current I ^2t of the switching power supply, and the common restriction scheme is as follows:

the first scheme is as follows: the bidirectional thyristor is connected in series at the input end, and the conduction of the thyristor is controlled by the photothyristor with zero-crossing detection. Therefore, when the alternating current is input, the controllable silicon is naturally conducted at an angle of 0 degree, and the surge current is very small.

The first solution has obvious disadvantages, needs an expensive optical control silicon and is only suitable for ac input, and if the switching power supply uses dc input, the first solution has no effect, i.e. it is expensive and has narrow application range.

Scheme II: a single-phase silicon controlled rectifier (a fixed resistor is connected in parallel) is connected in series behind the rectifier bridge, an auxiliary power supply part is made to supply power to the silicon controlled rectifier independently, the fixed resistor in a loop limits surge current during starting, and the silicon controlled rectifier is switched on after a fixed time is delayed.

The second scheme needs a unit for supplying power to the controllable silicon independently. Meanwhile, the power supply winding has a fatal weakness, if the drive of the controlled silicon is lost after the power supply stops working, the fixed resistor is connected in series in a loop, and if a large lightning stroke current is injected at the moment, hundreds of volts of voltage drop is generated on the resistor, so that the whole power supply can be damaged. Namely, the method has fatal hidden trouble and needs to increase an independent silicon controlled rectifier driving power supply unit.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a reduce switching power supply input surge current's regulating circuit in order to overcome the defect that above-mentioned prior art exists, this circuit has solved the problem that the silicon controlled rectifier SCR drive loses the back and damages the power.

The purpose of the utility model can be realized through the following technical scheme:

a regulating circuit for reducing input surge current of a switching power supply is connected between a PFC circuit and a DCDC circuit and comprises a capacitor C1, a capacitor C2, a silicon controlled rectifier Q1, a resistor R1, a diode D2 and a power supply VCC, wherein a capacitor C1 and a capacitor C2 are connected between the PFC circuit and the DCDC circuit in parallel, a resistor R1 is connected between a capacitor C1 and a capacitor C2, the anode of the diode D2 is connected with the capacitor C1, the cathode of the diode D2 is connected with the capacitor C2, the anode of the silicon controlled rectifier Q1 is connected with the capacitor C2, the cathode of the diode D1 is connected with the capacitor C1, and the control electrode of the diode is connected with the power supply VCC.

Preferably, the capacitance value ratio of the capacitor C1 to the capacitor C2 is 1:10000 to 1: 2.

Preferably, the capacitance value ratio of the capacitor C1 to the capacitor C2 is 1: 100.

Preferably, the PFC circuit employs an active PFC circuit.

Preferably, the active PFC circuit includes an inductor L1, a MOS transistor Q2 and a diode D1, the inductor L1 is respectively connected to the drain of the MOS transistor Q2 and the anode of the diode D1, and the cathode of the diode D1 is respectively connected to the anode of the capacitor C1 and the anode of the capacitor C2.

Preferably, the DCDC circuit includes a transformer and a MOS transistor Q3, and a primary winding of the transformer is connected to an anode of the capacitor C2 and a drain of the MOS transistor Q3, respectively.

Preferably, the secondary winding of the transformer is output through a diode D4.

Preferably, the winding Nvcc of the power supply VCC is linearly coupled to the primary winding of the transformer.

Preferably, one end of the winding Nvcc is connected to the input end of the power supply VCC through a diode D3.

Preferably, the other end of the winding Nvcc is connected with the source electrode of the MOS transistor Q3.

Compared with the prior art, the utility model has the advantages of it is following:

1) the problem of silicon controlled rectifier SCR drive damage power after losing is solved. Even if the power supply stops operating and there is no drive voltage (while the SCR current is less than the holding current), the surge is injected first into the small capacitor, creating a small voltage drop across the resistor that limits the surge current. The power failure can not be caused.

2) And an independent silicon controlled power supply unit is not needed, and the VCC of a power supply IC is adopted.

Drawings

Fig. 1 is a specific circuit diagram of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in fig. 1, the regulating circuit for reducing the input surge current of the switching power supply is connected between the PFC circuit and the DCDC circuit, the regulating circuit includes a capacitor C1, a capacitor C2, a thyristor Q1, a resistor R1, a diode D2 and a power supply VCC, the capacitor C1 and the capacitor C2 are connected in parallel and then connected between the PFC circuit and the DCDC circuit, the resistor R1 is connected between the capacitor C1 and the capacitor C2, the anode of the diode D2 is connected with the capacitor C1, the cathode is connected with the capacitor C2, the anode of the thyristor Q1 is connected with the capacitor C2, the cathode is connected with the capacitor C1, and the control electrode is connected with the power supply VCC.

The PFC circuit adopts an active PFC circuit. The active PFC circuit comprises an inductor L1, a MOS transistor Q2 and a diode D1, wherein the inductor L1 is respectively connected with the drain electrode of the MOS transistor Q2 and the anode of a diode D1, and the cathode of the diode D1 is respectively connected with the anode of a capacitor C1 and the anode of the capacitor C2.

The DCDC circuit comprises a transformer and an MOS (metal oxide semiconductor) tube Q3, wherein a primary coil of the transformer is respectively connected with the anode of a capacitor C2 and the drain of the MOS tube Q3. The secondary winding of the transformer is output through a diode D4. And a winding Nvcc of the power supply VCC is linearly coupled with a primary coil of the transformer. One end of the winding Nvcc is connected with the input end of a power supply VCC through a diode D3, and the other end of the winding Nvcc is connected with the source electrode of the MOS tube Q3.

The utility model discloses the big electric capacity of filtering of switching power supply's PFC output falls into two electric capacity parallelly connected, and a little electric capacity directly connects power return circuit, and after power return circuit work, the voltage that produces the IC power supply uses this voltage drive SCR, lets the parallelly connected big electric capacity of SCR. Therefore, at the startup moment of the switching power supply, only a small capacitor is arranged in the loop, so that the surge current I ^2t at the startup moment is very small, the power conversion unit is in the startup soft start process, and meanwhile, the loop charges the large capacitor through a fixed resistor. After the power conversion unit is started, the silicon controlled rectifier is driven to be electrified and conducted, and the large capacitor and the small capacitor work in parallel.

The specific working process is as follows:

as shown in fig. 1, capacitors behind the PFC are C1 and C2, and resistors R1, D2 and Q1 are provided between the two capacitors. When the switching power supply is powered on, only one small capacitor C1 is in the loop, and C2 is charged through R1. After the power loop of the switching power supply is powered on by C1, the soft start operation is started, in the soft start process (generally more than 500ms), the transformer winding VCC is powered on, the IC is controlled to operate, meanwhile, the VCC drives the silicon controlled rectifier Q1, and after the SCR Q1 is switched on, the capacitors C1 and C2 are connected in parallel, so that the normal operation of the full power of the power loop is ensured. During the PFC operation, C2 is charged by Q1, and C2 is discharged to C1 through diode D2. Thus, C2 and C1 are physically connected in parallel.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical scope of the present invention, and these modifications or replacements should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A regulating circuit for reducing input surge current of a switching power supply is connected between a PFC circuit and a DCDC circuit and is characterized in that the regulating circuit comprises a capacitor C1, a capacitor C2, a silicon controlled rectifier Q1, a resistor R1, a diode D2 and a power supply VCC, the capacitor C1 and the capacitor C2 are connected between the PFC circuit and the DCDC circuit after being connected in parallel, the resistor R1 is connected between the capacitor C1 and the capacitor C2, the anode of the diode D2 is connected with the capacitor C1, the cathode of the diode D2 is connected with the capacitor C2, the anode of the silicon controlled rectifier Q1 is connected with the capacitor C2, the cathode of the diode D1 is connected with the capacitor C1, and the control pole of the diode is connected with the power supply VCC.

2. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 1, wherein the capacitance ratio of the capacitor C1 to the capacitor C2 is 1:10000 to 1: 2.

3. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 2, wherein the capacitance ratio of the capacitor C1 to the capacitor C2 is 1: 100.

4. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 1, wherein the PFC circuit is an active PFC circuit.

5. The regulating circuit for reducing the input surge current of the switching power supply as claimed in claim 4, wherein the active PFC circuit comprises an inductor L1, a MOS transistor Q2 and a diode D1, the inductor L1 is respectively connected with the drain of the MOS transistor Q2 and the anode of a diode D1, and the cathode of the diode D1 is respectively connected with the anode of a capacitor C1 and the anode of a capacitor C2.

6. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 1, wherein the DCDC circuit comprises a transformer and a MOS transistor Q3, and a primary winding of the transformer is connected to an anode of a capacitor C2 and a drain of the MOS transistor Q3, respectively.

7. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 6, wherein the secondary winding of the transformer outputs through a diode D4.

8. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 6, wherein a winding Nvcc of the power supply VCC is linearly coupled to a primary winding of the transformer.

9. The regulating circuit for reducing the input inrush current of the switching power supply as claimed in claim 8, wherein one end of the winding Nvcc is connected to the input end of the power supply VCC through a diode D3.

10. The regulating circuit for reducing the input surge current of the switching power supply as claimed in claim 9, wherein the other end of the winding Nvcc is connected with the source electrode of a MOS transistor Q3.