CN113595375A

CN113595375A - Automatic discharge circuit for residual charge of switching power supply and control method thereof

Info

Publication number: CN113595375A
Application number: CN202111061379.3A
Authority: CN
Inventors: 梁小捷
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-09-10
Filing date: 2021-09-10
Publication date: 2021-11-02

Abstract

The invention discloses an automatic residual charge discharging circuit of a switching power supply, which relates to the technical field of switching power supplies and comprises an alternating current input rectifying and filtering unit, an alternating current voltage detection unit and a residual charge discharging unit; the alternating current input rectification filtering unit is respectively connected with the alternating current voltage detection unit and the residual charge discharging unit, and the alternating current voltage detection unit is connected with the residual charge discharging unit. The invention provides a control method suitable for an energy storage capacitor to automatically discharge residual charges after an alternating voltage of a switching power supply is cut off, which is characterized in that an alternating voltage detection unit is used for detecting the alternating voltage so as to control the residual charge discharge unit to automatically discharge the residual charges in the energy storage capacitor, so that the energy storage capacitor reaches safe voltage; the invention has the advantages of low power consumption, strong discharge capacity, high response speed, simple structure, low cost and the like.

Description

Automatic discharge circuit for residual charge of switching power supply and control method thereof

Technical Field

The invention relates to the technical field of switching power supplies, in particular to an automatic residual charge discharging circuit of a switching power supply and a control method thereof.

Background

A switching power supply, also called switching power supply, switching converter, is a high-frequency power conversion device, which is a kind of power supply. The function is to convert a level voltage into a voltage or current required by the user terminal through different types of architectures. The input of the switch power supply is mostly alternating current which is rectified and filtered into high-voltage direct current, and the required direct current power supply is output through the isolation converter.

Most of the schemes used by the switch power supply in the existing market do not have the function of automatically discharging the energy storage capacitor, the charge of the energy storage capacitor is difficult to discharge after the alternating current is switched off by the switch power supply, the energy storage capacitor needs to be manually discharged, and otherwise, the danger of electric shock of personnel after the alternating current is switched off is easily caused. .

Disclosure of Invention

The present invention is directed to an automatic discharging circuit for residual charge of a switching power supply, so as to solve the problems mentioned in the background art.

In order to solve the technical problems, the technical scheme of the invention is as follows: the utility model provides an automatic circuit of bleeding of switching power supply residual charge, includes alternating current input rectification filter unit, alternating current input rectification filter unit contains rectifier bridge BD100 and connects the energy storage capacitor C100 on rectifier bridge BD100, still includes alternating voltage detecting element and residual charge unit of bleeding. The alternating current input rectification filtering unit is respectively connected with the alternating current voltage detection unit and the residual charge discharging unit, and the alternating current voltage detection unit is connected with the residual charge discharging unit; when the alternating current is started to be input into the alternating current input rectifying and filtering unit, the energy storage capacitor C100 is fully charged; the alternating voltage detection unit detects that the alternating voltage is in an opening state, and the residual charge discharging unit stops discharging the charges; turning off the alternating voltage, and detecting the alternating voltage to be in a turn-off state by the alternating voltage detection unit; the residual charge discharging unit starts to discharge the charge until the charge discharging is finished.

Preferably, the residual charge discharging unit automatically discharges the residual charge by using a PN junction characteristic of a base electrode-an emitter electrode of the triode or by using a gate-source voltage characteristic of the MOS transistor.

Preferably, the residual charge draining unit is not limited to two triodes Q100 and Q101, and 1 to n triodes are connected in series according to the requirement of withstand voltage, and the number of the used resistors is n +3 corresponding to the number of the triodes connected in series.

Preferably, 1 to n of the triodes are all PNP-type triodes.

Preferably, the residual charge draining unit is not limited to 1 MOS transistor Q100, and may be formed by connecting 1 to n MOS transistors in series according to the requirement of voltage resistance, and the number of resistors used is n +3 corresponding to the number of triodes connected in series.

Preferably, 1 to n MOS tubes are all P-channel type MOS tubes.

Preferably, the alternating voltage detection unit includes 2 diodes D100 and D101, 1 resistor R104, and 1 capacitor C101, an anode of the diode D100 is connected to the alternating voltage L terminal, an anode of the diode D101 is connected to the alternating voltage N terminal, a cathode of the diode D100 is connected to a cathode of the diode D101, a cathode of the diode D100 is connected to one end of the capacitor C101 and one end of the resistor R104, a cathode of the diode D101 is connected to a cathode of the diode D103 of the residual charge draining unit, and the other end of the capacitor C101 and the other end of the resistor R104 are grounded.

Preferably, the residual charge discharging unit includes 2 PNP triodes Q100 and Q101, 4 resistors R100, R101, R102, R103, and 1 diode D103, one end of the resistor R100 is connected to the positive electrode of the energy storage capacitor of the ac input rectification filtering unit, the other end is connected to one end of the resistor R101 and the emitter of the triode Q100, the other end of the resistor R101 is connected to the base of the triode Q100 and one end of the resistor R102, the other end of the resistor R102 is connected to the base of the triode Q101 and one end of the resistor R103, the collector of the triode Q100 is connected to the emitter of the triode Q101, the collector of the triode Q101 is grounded, and the other end of the resistor R103 is connected to the anode of the diode D103.

Preferably, the residual charge draining unit includes 1P-type MOS transistor Q100, 3 resistors R100, R101, R103, 1 diode D103, and 1 zener diode ZD100, one end of the resistor R100 is connected to the positive electrode of the energy storage capacitor of the ac input rectification filter unit, the other end is connected to one end of the resistor R101 and the source of the MOS transistor Q100, the other end of the resistor R101 is connected to the gate of the MOS transistor Q100 and one end of the resistor R103, the gate of the MOS transistor Q100 is connected to one end of the resistor R103, the other end of the resistor R103 is connected to the anode of the diode D103, the drain of the MOS transistor Q100 is grounded, the anode of the zener diode ZD100 is connected to the gate of the MOS transistor Q100, and the cathode of the zener diode ZD100 is connected to the source of the MOS transistor Q100.

In another aspect, the present invention further provides a control method for an automatic discharging circuit of residual charge of a switching power supply, which is applied to the automatic discharging circuit of residual charge of a switching power supply, and includes the following steps:

the method comprises the following steps: starting AC input to an AC input rectification filtering unit to fully charge an energy storage capacitor;

step two: the alternating voltage detection unit detects that the alternating voltage is in an opening state, and the residual charge discharging unit stops discharging the charges;

step three: turning off the alternating voltage, and detecting the alternating voltage to be in a turn-off state by the alternating voltage detection unit;

step four: the residual charge discharging unit starts to discharge the charge until the charge discharging is finished.

Compared with the prior art, the invention has the beneficial effects that: the invention provides a control method suitable for automatic discharge of residual charges of an energy storage capacitor after the alternating voltage of a switching power supply is cut off, which is characterized in that an alternating voltage detection unit is used for detecting the alternating voltage so as to control the residual charge discharge unit to discharge the residual charges in the energy storage capacitor.

Drawings

Fig. 1 is a schematic diagram of the present invention.

Fig. 2 is a circuit diagram of a first embodiment of the present invention.

Fig. 3 is a circuit diagram of a second embodiment of the present invention.

Reference numerals: 100. an AC input rectification filter unit; 200. an alternating voltage detection unit; 300. and a residual charge discharging unit.

Detailed Description

The technical solutions 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, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1:

referring to fig. 1, in an embodiment of the present invention, a capacitor discharge control circuit includes an ac input rectifying and filtering unit 100, a residual charge discharging unit 300, and an ac voltage detecting unit 200;

referring to fig. 1 again, the input end of the input rectifying and filtering unit is connected to the ac voltage, and the output end of the input rectifying and filtering unit is connected to the input end of the residual charge draining unit 300;

thus, it should be noted that the input rectifying and filtering unit is used for rectifying and filtering the alternating voltage and the energy storage capacitor stores the charge.

Referring to fig. 1 again, the input end of the ac voltage detecting unit 200 is connected to the input end of the ac input filtering unit, and the output end of the ac voltage detecting unit 200 is connected to the control end of the residual charge draining unit 300;

thus, it should be noted that the ac voltage detecting unit 200 is configured to detect an ac input voltage and control the residual charge draining unit 300, so that the residual charge draining unit 300 can be controlled according to the ac input voltage.

Referring to fig. 1 again, the input terminal of the residual charge draining unit 300 is connected to the output terminal of the ac input rectifying and filtering unit 100, and the control terminal of the residual charge draining unit 300 is connected to the output terminal of the ac voltage detecting unit 200.

In this way, it should be noted that the residual charge draining unit 300 is configured to drain the residual charge of the ac input rectifying and filtering unit 100 when the ac voltage is disconnected, so that the residual charge voltage of the ac input rectifying and filtering unit 100 rapidly drops to the safety voltage.

Further, referring to fig. 1 and fig. 2, the ac input rectifying and filtering unit 100 includes a rectifying bridge BD100 and an energy storage capacitor C100, two ac input terminals of the rectifying bridge BD100 are respectively connected to ac voltages L and N, a positive output terminal of the rectifying bridge BD100 is connected to a positive electrode of the energy storage capacitor C100, and a negative output terminal of the rectifying bridge BD100 is connected to a negative electrode of the energy storage capacitor C100 and is grounded;

in this way, it should be noted that, when the ac input rectifying and filtering unit 100 starts to operate, that is, an ac voltage is input, the rectifier bridge BD100 rectifies the ac voltage into a dc voltage, and the energy storage capacitor C100 filters the dc voltage and stores electric charges.

Further, referring to fig. 1 and fig. 2 together, the ac voltage detecting unit 200 includes 2 diodes D100 and D101, 1 resistor R104, and 1 capacitor C101, wherein an anode of the diode D100 is connected to the ac voltage L terminal, an anode of the diode D101 is connected to the ac voltage N terminal, a cathode of the diode D100 is connected to a cathode of the diode D101, a cathode of the diode D100 is connected to one end of the capacitor C101 and one end of the resistor R104, a cathode of the diode D101 is connected to a cathode of the diode D103 of the residual charge discharging unit 300, and the other end of the capacitor C101 and the other end of the resistor R104 are grounded;

thus, it should be noted that, when the ac voltage detecting unit 200 starts to operate, the diodes D100 and D101 detect that there is an input ac voltage, the voltage of the capacitor C101 is higher than the voltage of the emitter of the transistor Q100, and the residual charge draining unit 300 temporarily stops operating; when the diodes D100 and D101 detect no input ac voltage, the capacitor C101 discharges through the resistor R104, so that the voltage of the capacitor C101 is lower than the voltage of the emitter of the transistor Q100, and at this time, the residual charge draining unit 300 starts to operate. Thereby achieving the function of automatically controlling the discharge of residual charge.

Further, referring to fig. 1 and fig. 2 together, the residual charge draining unit 300 includes 2 PNP transistors Q100 and Q101, 4 resistors R100, R101, R102, R103, and 1 diode D103, one end of the resistor R100 is connected to the positive electrode of the energy storage capacitor of the ac input rectification filtering unit 100, the other end is connected to one end of the resistor R101 and the emitter of the transistor Q100, the other end of the resistor R101 is connected to the base of the transistor Q100 and one end of the resistor R102, the other end of the resistor R102 is connected to the base of the transistor Q101 and one end of the resistor R103, the collector of the transistor Q100 is connected to the emitter of the transistor Q101, the collector of the transistor Q101 is grounded, and the other end of the resistor R103 is connected to the anode of the diode D103.

Thus, it should be noted that, when the residual charge draining unit 300 is started, i.e., the ac voltage is cut off, the cathode voltage of the diode D103 (i.e., the voltage of the capacitor C101) at the control end of the residual charge draining unit 300 is lower than the voltage of the emitter of the transistor Q100, so that the PN junction voltage of the base-emitter of the transistor Q100 reaches the conduction condition of the transistor Q100, and further the PN junction voltage of the base-emitter of the transistor Q101 reaches the conduction condition of the transistor Q101, so that the energy storage capacitor C100 drains the residual charge through the resistor R100, the transistors Q100 and Q101, and the voltage of the capacitor C100 reaches the safety voltage, i.e., the PN junction voltages of the bases-emitters of the transistors Q100 and Q101 do not satisfy the conduction condition of the transistor Q101, and the transistors Q100 and Q101 are cut off; when the residual charge discharging unit 300 stops working, that is, when alternating current voltage is input, the cathode voltage (that is, the voltage of the capacitor C101) of the diode D103 at the control end of the residual charge discharging unit 300 is higher than the voltage of the emitter of the triode Q100, so that the base-emitter voltage of the triode Q100 cannot meet the PN junction voltage to cut off the triode Q100, and meanwhile, the base-emitter voltage of the triode Q101 cannot meet the PN junction voltage to cut off, thereby reducing loss when alternating current is input;

therefore, it should be noted that the diode D103 plays a role in preventing a large current from passing through the resistors R103, R102, and R101 when the device is turned on, and also plays a role in protecting the triodes Q100 and Q101, that is, the voltage of the energy storage capacitor C100 is low when the device is turned on, that is, the voltage of the emitter of the triode Q100 is lower than the voltage of the capacitor C101, so as to prevent the base-emitter voltages of the triodes Q100 and Q101 from being damaged due to being too high;

thus, it should be noted that the residual charge draining unit 300 is not limited to the two transistors Q100 and Q101, and may be formed by connecting 1 to n transistors in series according to the requirement of voltage endurance, and the number of resistors used is n +3 corresponding to the number of transistors in series.

Thus, it should be noted that the 1 to n transistors are all PNP transistors.

In this way, it should be noted that the residual charge draining unit 300 automatically drains the residual charge by using the PN junction characteristic of the base-emitter of the transistor.

Example 2:

referring to fig. 1 and 3, the difference from embodiment 1 is that the residual charge draining unit 300 includes 1P-type MOS transistor Q100, 3 resistors R100, R101, R103, 1 diode D103, and 1 zener diode ZD100, one end of the resistor R100 is connected to the positive electrode of the energy storage capacitor of the ac input rectifying and filtering unit 100, the other end of the resistor R100 is connected to one end of the resistor R101 and the source electrode of the MOS transistor Q100, the other end of the resistor R101 is connected to the gate of the MOS transistor Q100 and one end of the resistor R103, the gate of the MOS transistor Q100 is connected to one end of the resistor R103, the other end of the resistor R103 is connected to the anode of the diode D103, the drain of the MOS transistor Q100 is grounded, the anode of the zener diode ZD100 is connected to the gate of the MOS transistor Q100, and the cathode of the zener diode ZD100 is connected to the source electrode of the MOS transistor Q100.

Thus, it should be noted that when the residual charge discharging unit 300 is started, i.e., the ac voltage is cut off, the cathode voltage of the diode D103 at the control end of the residual charge discharging unit 300 (i.e., the voltage of the capacitor C101) is lower than the source voltage of the MOS transistor Q100, so that the gate-source voltage of the MOS transistor Q100 reaches the threshold voltage to turn on the MOS transistor Q100, and thus the energy storage capacitor C100 discharges the residual charge through the resistor R100 and the MOS transistor Q100, so that the voltage of the capacitor C100 reaches the safe voltage, i.e., the gate-source voltage of the MOS transistor Q100 is lower than the threshold voltage, and the MOS transistor Q100 is turned off; when the residual charge discharging unit 300 stops working, that is, when an alternating voltage is input, the cathode voltage (that is, the voltage of the capacitor C101) of the diode D103 at the control end of the residual charge discharging unit 300 is higher than the source voltage of the MOS transistor Q100, and the gate-source voltage of the MOS transistor Q100 does not meet the threshold voltage to cut off the MOS transistor Q100, thereby reducing the power loss;

in this way, the diode D103 prevents a large current from passing through the resistors R103, R102, and R101 during power-on; the zener diode ZD100 is used to protect the MOS transistor Q100 and prevent the gate-source voltage from exceeding the breakdown voltage value and being damaged.

Thus, it should be noted that the residual charge draining unit 300 is not limited to 1 MOS transistor Q100, and may be formed by connecting 1 to n MOS transistors in series according to the requirement of voltage endurance, and the number of resistors used is n +3 corresponding to the number of series transistors.

In this way, it should be noted that all of the 1 to n MOS transistors are P-channel MOS transistors.

In this way, the residual charge draining unit 300 automatically drains the residual charge by using the gate-source voltage characteristic of the MOS transistor.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.

Claims

1. An automatic discharge circuit for residual charge of a switching power supply comprises an alternating current input rectifying and filtering unit (100), wherein the alternating current input rectifying and filtering unit (100) comprises a rectifying bridge BD100 and an energy storage capacitor C100 connected to the rectifying bridge BD100,

the device also comprises an alternating voltage detection unit (200) and a residual charge bleeder unit (300); the alternating current input rectifying and filtering unit (100) is respectively connected with the alternating current voltage detection unit (200) and the residual charge leakage unit (300), and the alternating current voltage detection unit (200) is connected with the residual charge leakage unit (300);

when the alternating current is started to be input into the alternating current input rectification filtering unit (100), the energy storage capacitor C100 is fully charged; the alternating voltage detection unit (200) detects that the alternating voltage is in an opening state, and the residual charge discharging unit (300) stops discharging the charges; the alternating voltage is turned off, and the alternating voltage detection unit (200) detects that the alternating voltage is in a turn-off state; the residual charge draining unit (300) starts to drain the charge until the charge draining is completed.

2. The automatic residual charge discharging circuit of switching power supply as claimed in claim 1, wherein: the residual charge discharging unit (300) automatically discharges residual charges by utilizing the PN junction characteristic of the base electrode-emitting electrode of the triode or automatically discharges the residual charges by utilizing the grid electrode-source electrode voltage characteristic of the MOS tube.

3. The automatic residual charge discharging circuit of switching power supply as claimed in claim 2, wherein: the residual charge discharging unit (300) is not limited to two triodes Q100 and Q101, 1 to n triodes are connected in series according to the withstand voltage requirement, and the number of used resistors is n +3 corresponding to the triodes connected in series.

4. The automatic residual charge discharging circuit of switching power supply as claimed in claim 3, wherein: and the 1-n triodes are PNP type triodes.

5. The automatic residual charge discharging circuit of switching power supply as claimed in claim 2, wherein: the residual charge discharging unit (300) is not limited to 1 MOS tube Q100, 1 to n MOS tubes can be connected in series according to the withstand voltage requirement, and the number of the used resistors is n +3 corresponding to the number of the series triodes.

6. The automatic residual charge discharging circuit of switching power supply as claimed in claim 5, wherein: and the 1-n MOS tubes are all P-channel MOS tubes.

7. The automatic residual charge discharging circuit of switching power supply as claimed in claim 1, wherein: the alternating voltage detection unit (200) comprises 2 diodes D100 and D101, 1 resistor R104 and 1 capacitor C101, wherein the anode of the diode D100 is connected with an alternating voltage L end, the anode of the diode D101 is connected with an alternating voltage N end, the cathode of the diode D100 is connected with the cathode of the diode D101, the cathode of the diode D100 is connected with one end of the capacitor C101 and one end of the resistor R104, the cathode of the diode D101 is connected with the cathode of a diode D103 of the residual charge discharging unit (300), and the other end of the capacitor C101 and the other end of the resistor R104 are grounded.

8. The automatic residual charge discharging circuit of switching power supply as claimed in claim 7, wherein: the residual charge discharging unit (300) comprises 2 PNP triodes Q100 and Q101, 4 resistors R100, R101, R102, R103 and 1 diode D103, one end of the resistor R100 is connected with the positive electrode of an energy storage capacitor of the alternating current input rectifying and filtering unit (100), the other end of the resistor R100 is connected with one end of the resistor R101 and the emitting electrode of the triode Q100, the other end of the resistor R101 is connected with the base electrode of the triode Q100 and one end of the resistor R102, the other end of the resistor R102 is connected with the base electrode of the triode Q101 and one end of the resistor R103, the collector electrode of the triode Q100 is connected with the emitting electrode of the triode Q101, the collector electrode of the triode Q101 is grounded, and the other end of the resistor R103 is connected with the anode of the diode D103.

9. The automatic residual charge discharging circuit of switching power supply as claimed in claim 7, wherein: the residual charge discharging unit (300) comprises 1P-type MOS tube Q100, 3 resistors R100, R101 and R103, 1 diode D103 and 1 voltage stabilizing diode ZD100, one end of the resistor R100 is connected with the anode of the energy storage capacitor of the alternating current input rectifying and filtering unit (100), the other end of the resistor R100 is connected with one end of the resistor R101 and the source electrode of the MOS tube Q100, the other end of the resistor R101 is connected with the grid electrode of the MOS tube Q100 and one end of the resistor R103, the grid electrode of the MOS tube Q100 is connected with one end of the resistor R103, the other end of the resistor R103 is connected with the anode of the diode D103, the drain electrode of the MOS tube Q100 is grounded, the anode of the voltage stabilizing diode ZD100 is connected with the grid electrode of the MOS tube Q100, and the cathode of the voltage stabilizing diode ZD100 is connected with the source electrode of the MOS tube Q100.

10. A control method of an automatic circuit for discharging residual charge of a switching power supply, which is applied to the automatic circuit for discharging residual charge of the switching power supply of any one of claims 1 to 9, and is characterized by comprising the following steps:

the method comprises the following steps: starting alternating current input to an alternating current input rectification filtering unit (100) to enable an energy storage capacitor to be fully charged;

step two: the alternating voltage detection unit (200) detects that the alternating voltage is in an opening state, and the residual charge discharging unit (300) stops discharging the charges;

step three: the alternating voltage is turned off, and the alternating voltage detection unit (200) detects that the alternating voltage is in a turn-off state;

step four: the residual charge draining unit (300) starts to drain the charge until the charge draining is completed.