Power failure holding circuit for switching power supply and switching power supply

Abstract

The utility model provides a power-down holding circuit for a switching power supply, which relates to the technical field of switching circuits and comprises a thermistor RT2, a diode D1 and a plurality of electrolytic capacitor banks connected in parallel, and the thermistor RT2 is connected in series with the electrolytic capacitor banks after being connected in parallel with the diode D1. According to the utility model, the circuit structure is simple, and components are few; the impact current is effectively reduced by adopting the power-down holding circuit; and after the input power supply is cut off, the diode D1 is used for discharging the loop, so that the output delay power failure is realized. Meanwhile, by changing parameter matching and device type selection of the power-down holding circuit, different power-down holding time is achieved, the performance is reliable, and therefore the design cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to switch circuit technical field especially relates to a kind of power-down holding circuit and switching power supply for switching power supply. BACKGROUND

[0002] At present, with the rapid development of industry, the power supply capacity of switching power supply is required in the field of industrial application. Especially after the system input power is powered down, the switching power supply needs to provide power supply for the system for a period of time to ensure that the system can be reliably closed. The existing method usually uses enough parallel filter capacitors at the input port to store enough energy. However, this method increases the number of electrolytic capacitors, making it difficult to design a port anti-power-on inrush current impact circuit, and the cost is high. In order to solve the above problems, the utility model provides a power-down holding circuit and switching power supply for switching power supply. SUMMARY

[0003] The utility model provides a power-down holding circuit and switching power supply for switching power supply to solve one or more of the above problems.

[0004] The utility model provides a power-down holding circuit for switching power supply, and the power-down holding circuit includes a thermistor RT2, a diode D1 and an electrolytic capacitor group. The thermistor RT2 is connected in parallel with the diode D1 and then connected in series with the electrolytic capacitor group.

[0005] As a preferred implementation, the electrolytic capacitor group is composed of multiple electrolytic capacitors connected in parallel, including electrolytic capacitors EC2, EC3 and EC4.

[0006] As a preferred implementation, the resistance value of the thermistor RT2 is in the range of 20Ω-50Ω.

[0007] The application also provides a switching power supply using the above power-down holding circuit for switching power supply. The switching power supply includes a rectifier circuit, a filter circuit and a power-down holding circuit connected in sequence.

[0008] As a preferred implementation, the rectifier circuit is a bridge rectifier circuit composed of four diodes, which is used to convert alternating current into direct current. The filter circuit is used to smooth the rectified direct current. The filter circuit includes a thermistor RT1 and an electrolytic capacitor EC1. The thermistor RT1 and the electrolytic capacitor EC1 are connected in series. The input end of the thermistor RT1 is connected to the output end of the rectifier circuit, and the other end of the electrolytic capacitor EC1 is connected to the other output end of the bridge rectifier circuit.

[0009] As a preferred implementation, the resistance value of the thermistor RT1 is in the range of 8Ω-15Ω.

[0010] As a kind of implementable preferred mode, the switching power supply further includes protection circuit, the input end of rectifier circuit is connected protection circuit, and protection circuit is used to realize electromagnetic interference protection and power on surge protection.

[0011] As a kind of implementable preferred mode, the protection circuit includes common mode choke, differential mode capacitor CX1, differential mode capacitor CX2, common mode capacitor CY1 and common mode capacitor CY2;

[0012] Two input ends of common mode choke are connected with live wire L and zero line N respectively, two output ends of common mode choke are connected with two input ends of bridge rectifier circuit respectively, differential mode capacitor CX1 and differential mode capacitor CX2 are arranged at input side and output side of common mode choke respectively, two ends of differential mode capacitor CX1 and differential mode capacitor CX2 are connected with live wire L and zero line N respectively, one end of common mode capacitor CY1 and common mode capacitor CY2 is connected with live wire and zero line respectively, and the other end is connected with ground wire.

[0013] As a kind of implementable preferred mode, pressure-sensitive resistor RV1 is connected between live wire L and zero line N, and pressure-sensitive resistor RV1 is connected in parallel across differential mode capacitor CX1, and pressure-sensitive resistor RV2 and pressure-sensitive resistor RV3 are connected between input end and output end of common mode choke respectively.

[0014] As a kind of implementable preferred mode, the output end of power-down holding circuit is connected with post-stage PWM circuit, and post-stage PWM circuit is used to convert the amplitude of input voltage into pulse with certain width, to realize the output of final voltage.

[0015] Compared with prior art, the utility model has the advantages that:

[0016] First, the circuit structure of the utility model is simple, and the device composition is less;By adopting power-down holding circuit, impact current is effectively reduced;After input power is powered off, diode D1 is used to discharge loop, to realize output delay power-down. At the same time, by changing parameter matching and device selection of power-down holding circuit, different power-down holding time is realized, and performance is reliable, so that design cost is greatly reduced.

[0017] Second, the protection circuit of the application adopts protection devices such as pressure-sensitive resistor, safety capacitor, common mode choke, etc., and common mode interference is suppressed by cross-connection Y safety capacitor on live wire, zero line and ground wire;Common mode choke is connected in series on live wire and zero line, which not only filters common mode electromagnetic interference, but also suppresses itself from emitting electromagnetic interference outward. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0019] Figure 1 is a circuit diagram of a power-down holding circuit for a switching power supply provided by the present application;

[0020] Figure 2 is a composition schematic diagram of a switching power supply provided by the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0022] As shown in Figure 1 , the present application provides a power-down holding circuit for a switching power supply. The power-down holding circuit comprises a thermistor RT2, a diode D1 and an electrolytic capacitor group. The thermistor RT2 is connected in parallel with the diode D1 and then connected in series with the electrolytic capacitor group. It should be pointed out that the electrolytic capacitor group is composed of a plurality of electrolytic capacitors connected in parallel, including an electrolytic capacitor EC2, an electrolytic capacitor EC3 and an electrolytic capacitor EC4. The thermistor RT2 is a large resistance thermistor, and its resistance range is 20Ω-50Ω. Thus, by selecting a large resistance thermistor, the electrolytic capacitor can be slowly charged, and the impact current can be effectively reduced. At the same time, after the input power is cut off, the diode D1 is used to discharge the loop, so as to realize output delay power-down. Moreover, by adjusting the capacitance value of the electrolytic capacitors in the electrolytic capacitor group, different delay requirements can be realized.

[0023] Therefore, as shown in Figure 2 , the present application further provides a switching power supply adopting the above power-down holding circuit. The switching power supply comprises a rectifier circuit 2, a filter circuit 3 and a power-down holding circuit 4 connected in sequence.

[0024] Preferably, the rectifier circuit is a bridge rectifier circuit composed of four diodes, which converts AC to DC to achieve conversion of alternating current to direct current; the filter circuit is used to smooth the rectified direct current, and the filter circuit includes a thermistor RT1 and an electrolytic capacitor EC2, the thermistor RT1 and the electrolytic capacitor EC2 are connected in series, the input end of the thermistor RT1 is connected with the output end of the rectifier circuit, and the output end of the electrolytic capacitor EC2 is connected with the input end of the power-down holding circuit. It should be pointed out that the thermistor RT1 adopts a small resistance value thermistor, and the resistance value range is 8Ω-15Ω. Thus, the small resistance value thermistor RT1 and the electrolytic capacitor EC1 can smooth the fluctuating direct current after rectification, and play a certain degree of energy storage effect.

[0025] Another implementable preferred embodiment should be pointed out that the switch circuit of the application is connected between the input end and the output end of the alternating current mains, i.e. between the live wire and the neutral wire, and the voltage of the alternating current is generally 220V. The switching power supply can also include a protection circuit 1, a rectifier circuit 2, a filter circuit 3, a power-down holding circuit 5 and a later-stage PWM circuit 5 connected in sequence. The output end of the power-down holding circuit is connected with the later-stage PWM circuit, and the later-stage PWM circuit is used to convert the amplitude of the input voltage into a pulse with a certain width to achieve the output of the final voltage.

[0026] The input end of the rectifier circuit 2 is connected with the protection circuit, and the protection circuit is used to realize electromagnetic interference protection and power-on surge protection. The protection circuit includes a common-mode choke, a differential-mode capacitor CX1, a differential-mode capacitor CX2, a common-mode capacitor CY1 and a common-mode capacitor CY2; the two input ends of the common-mode choke are connected with the live wire L and the neutral wire N respectively, the two output ends of the common-mode choke are connected with the two input ends of the bridge rectifier circuit respectively, the differential-mode capacitor CX1 and the differential-mode capacitor CX2 are arranged on the input side and the output side of the common-mode choke respectively, the two ends of the differential-mode capacitor CX1 and the differential-mode capacitor CX2 are connected with the live wire L and the neutral wire N respectively, and the differential-mode interference noise is filtered out to achieve the purpose of suppressing differential-mode high-frequency interference noise. One end of the common-mode capacitor CY1 and the common-mode capacitor CY2 is connected with the live wire and the neutral wire respectively, and the other end is connected with the ground wire. It should be pointed out that the capacitors in the application are differential-mode capacitors CX1 and CX2, which are safety capacitors. Thus, the two Y common-mode capacitors CY1 and CY2 play a filtering effect on common-mode interference noise, and the common-mode interference is obviously suppressed.

[0027] The live wire L and the neutral wire N are connected with a pressure-sensitive resistor RV1, and the pressure-sensitive resistor RV1 is connected in parallel with the differential-mode capacitor CX1. The input end and the output end of the common-mode choke are connected with a pressure-sensitive resistor RV2 and a pressure-sensitive resistor RV3 respectively.

[0028] Therefore, the protection circuit of the application adopts protection devices such as a pressure sensitive resistor, an AN protection capacitor, and a common mode choke coil, and uses the Y AN protection capacitor connected across the live wire, the zero wire and the ground wire to suppress common mode interference; meanwhile, the common mode choke coil is connected in series with the live wire and the zero wire to filter out common mode electromagnetic interference, and can also suppress itself from emitting electromagnetic interference outward.

[0029] In this document, relational terms such as and and or and the like are for the purpose of distinguishing one entity or action from another entity or action, and are not to be construed as necessarily dictating a particular order of execution or sequence of actions. Moreover, the terms "comprises" and "comprising," when used in this document, short for "comprising at least the recited elements," and do not exclude additional elements. In other words, "comprising" has the same meaning as "including" and "including" has the same meaning as "comprising."

[0030] Finally, it should be noted that the above embodiments are merely used to illustrate the technical solutions of the present application, rather than limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A power-down hold circuit for a switching power supply, characterized by, The power-off holding circuit comprises a thermistor RT2, a diode D1 and an electrolytic capacitor group, and the thermistor RT2 is connected in parallel with the diode D1 and then connected in series with the electrolytic capacitor group.

2. The power-down hold-up circuit for a switching power supply according to claim 1, wherein The electrolytic capacitor group comprises a plurality of electrolytic capacitors connected in parallel, including an electrolytic capacitor EC2, an electrolytic capacitor EC3 and an electrolytic capacitor EC4.

3. The power-down hold-up circuit for a switching power supply according to claim 2, wherein The resistance value of the thermistor RT2 ranges from 20Ω to 50Ω.

4. A switching power supply using the power-down holding circuit for a switching power supply according to any one of claims 1 to 3, characterized by, The switching power supply comprises a rectifier circuit, a filter circuit and a power-off holding circuit connected in sequence.

5. The switching power supply of claim 4, wherein The rectifier circuit is a bridge rectifier circuit comprising four diodes, which is used to convert alternating current into direct current; the filter circuit is used to smooth the direct current after rectification, and the filter circuit comprises a thermistor RT1 and an electrolytic capacitor EC1, the thermistor RT1 and the electrolytic capacitor EC1 are connected in series, the input end of the thermistor RT1 is connected with the output end of the rectifier circuit, and the other end of the electrolytic capacitor EC1 is connected with the other output end of the bridge rectifier circuit.

6. The switching power supply of claim 5, wherein The resistance value of the thermistor RT1 ranges from 8Ω to 15Ω.

7. The switching power supply of claim 4, wherein The switching power supply further comprises a protection circuit, the input end of the rectifier circuit is connected with the protection circuit, and the protection circuit is used to realize electromagnetic interference protection and power-on surge protection.

8. The switching power supply of claim 7, wherein The protection circuit comprises a common-mode choke, a differential-mode capacitor CX1, a differential-mode capacitor CX2, a common-mode capacitor CY1 and a common-mode capacitor CY2. The two input ends of the common-mode choke are connected with a live wire L and a neutral wire N respectively, the two output ends of the common-mode choke are connected with two input ends of the bridge rectifier circuit respectively, the differential-mode capacitor CX1 and the differential-mode capacitor CX2 are arranged on the input side and the output side of the common-mode choke respectively, the two ends of the differential-mode capacitor CX1 and the differential-mode capacitor CX2 are connected with the live wire L and the neutral wire N respectively, and one end of the common-mode capacitor CY1 and the common-mode capacitor CY2 is connected with the live wire and the neutral wire respectively, and the other end is connected with the ground wire.

9. The switching power supply of claim 8, wherein The pressure-sensitive resistor RV1 is connected between the live wire L and the neutral wire N, and the pressure-sensitive resistor RV1 is connected in parallel across the differential-mode capacitor CX1, and the input end and the output end of the common-mode choke are respectively connected with a pressure-sensitive resistor RV2 and a pressure-sensitive resistor RV3.

10. The switching power supply of claim 4, wherein The output end of the power-off holding circuit is connected with a later-stage PWM circuit, and the later-stage PWM circuit is used to convert the amplitude of the input voltage into a pulse with a certain width to realize the output of the final voltage.

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