CN113572348B - A switch circuit with the function of releasing residual voltage - Google Patents

Abstract

The invention relates to a switch circuit with the function of releasing residual voltage, comprising a filter capacitor located at the output end of the switch circuit, and a discharge circuit for forming a loop with the filter capacitor, the discharge circuit is composed of a discharge resistor and a switch connected in series; After the switching switch is closed, it is grounded, so that the quiescent current of the switching power supply and/or the residual voltage formed in the filter capacitor form a discharge loop to the ground. When the switch circuit supplies power to the load, the switch is turned off, so that the internal impedance or residual voltage discharge resistor does not participate in energy consumption, and the switch is closed only when the residual voltage needs to be released to consume static current.

Description

A switch circuit with the function of releasing residual voltage

technical field

The invention relates to a switch circuit with the function of releasing residual voltage.

Background technique

The switching circuit is a high-frequency power conversion device, which mainly uses power electronic switching devices, such as transistors, MOS tubes, thyristors, etc., to make the electronic switching devices "turn on" and "off" periodically through the control circuit. ", let the power electronic switching device perform pulse modulation on the input voltage, so as to realize the function of voltage conversion and output voltage adjustment and automatic voltage stabilization. After the switching circuit stops supplying power to the load, a residual voltage will be formed on the filter capacitor at the output end of the power supply. Figure 1 is a schematic diagram of the output terminal of a conventional switching power supply. The quiescent current is the internal current of the switching power supply without any output. The quiescent current is very small, generally ranging from several mA to tens of mA. But as long as the switching power supply input is powered, the quiescent current will always exist. After the switching power supply stops supplying power to the load, the filter capacitor C1 at the output terminal will slowly discharge through the internal impedance of the power supply. However, due to the existence of internal quiescent current, the voltage of the filter capacitor C1 cannot be released to 0V, and eventually a stable voltage is formed at both ends of the filter capacitor C1, which is usually called the residual voltage Ur.

At present, the way to eliminate the residual voltage Ur is to add a "dummy load" at the output end of the power supply to consume static current. As shown in Figure 1, the usual practice is to add a resistor R1 with an appropriate resistance value and a suitable package between the positive and negative poles of the power output terminal. After the switching power supply stops supplying power to the load, it forms a loop with the filter capacitor at the power output terminal and releases residual voltage. However, this way of releasing the residual voltage Ur has the following disadvantages:

(1) In order to improve the reliability of the dummy load resistor as much as possible, it is necessary to consider the derating of the resistor power consumption, which will easily lead to a larger resistor package and occupy a larger space for placement, and increase the PCB board of the switching power supply The difficulty of wiring layout;

(2) As an additional fixed load, the dummy load resistance will introduce an additional loss, which will reduce the output conversion efficiency of the switching power supply itself;

(3) As a special device, the dummy load resistor increases the production cost of the switching power supply itself to a certain extent.

Contents of the invention

The invention proposes a switch circuit with the function of releasing residual voltage.

The first aspect of the present invention is to provide a switch circuit with the function of releasing residual voltage, including a filter capacitor located at the output end of the switch circuit, and a discharge circuit for forming a loop with the filter capacitor, the discharge circuit consists of a discharge resistor and a switch The switches are connected in series; the switching switch is closed and grounded, so that the static current of the switching power supply and/or the residual voltage formed in the filter capacitor form a discharge loop to the ground.

As an implementation manner, the discharge resistor in the discharge circuit is a resistor with a certain resistance value, and the resistance value of the resistor is used to determine the residual voltage discharge time.

As an implementation manner, the discharge resistor in the discharge circuit is formed by the internal impedance of the switch circuit.

As an implementation manner, in the working state where the switch circuit outputs current to the load, the switch is turned off; in the non-working state where the switch circuit stops outputting current to the load, the switch is closed.

As an implementation manner, when the switch circuit stops outputting current to the load, it immediately closes the switch, turns on the discharge circuit and maintains it; when the switch circuit outputs current to the load again, it immediately turns off the switch.

As an implementation, after the switch circuit stops outputting current to the load, when the voltage on the filter capacitor is released to the voltage threshold Vo, the switch is immediately closed, and the discharge circuit is turned on and maintained; When the current is output, the switching switch is immediately turned off; the voltage threshold Vo is smaller than the output voltage when the switching circuit is working, and larger than the residual voltage of the filter capacitor.

As an implementation, after the switch circuit stops outputting current to the load, when the voltage on the filter capacitor is released to the residual voltage, the switch is closed, the discharge circuit is turned on and maintained; when the switch circuit outputs current to the load again , turn off the toggle switch immediately.

The second aspect of the present invention is to provide a control circuit for controlling the opening or closing of the switch, including a control circuit for controlling the opening or closing of the switch, and the control circuit includes a voltage sampling module, a control module and a driving module;

The voltage sampling module is used to collect the voltage data of the filter capacitor C1 at the output end of the switching circuit;

The control module is used to judge according to the voltage data of the filter capacitor C1 collected by the voltage sampling module, whether the voltage of the filter capacitor C1 meets the operation condition of the switching switch S1 being closed and conducting, and if so, sends a control signal to the drive module;

The drive module controls the switching switch to close according to the control signal.

As an implementation, the method for controlling the switch to be closed or disconnected is as follows:

Step S1: the control module determines whether the switch circuit stops outputting current to the load; if the switch circuit stops outputting current to the load, proceed to step S2; if the switch circuit is outputting current to the load, continuously detects whether the switch circuit stops outputting current to the load;

Step S2: The control module judges whether the voltage at both ends of the filter capacitor C1 meets the action condition for the switch S1 to be closed and turned on; when the voltage at both ends of the filter capacitor C1 meets the action condition for the switch S1 to be turned on and off, the control module sends a signal to the drive module control signal; the drive module closes the switch S1 according to the control signal;

Step S3: When the switch S1 is closed, the control module continues to judge whether the switch circuit starts to output current to the load, and if the switch circuit starts to output current to the load, it sends a control signal to the drive module; the drive circuit disconnects the switch according to the control signal .

As an implementation mode, the voltage of the filter capacitor C1 meets the action condition that the switching switch S1 is closed and turned on:

In the control mode where the switching power supply stops outputting current to the output load R2 and immediately closes the switching switch S1, when the voltage of the filter capacitor C1 is lower than the output voltage Vout of the switching power supply, the voltage of the filtering capacitor C1 meets the action condition that the switching switch S1 is closed and conducting ;

In the control mode where the voltage on the filter capacitor C1 is released to the voltage amplitude Vo and immediately closes the switch S1, when the voltage of the filter capacitor C1 drops to the voltage amplitude Vo, the voltage of the filter capacitor C1 conforms to the switch S1 closed conduction Common operating conditions;

In the control mode where the voltage on the filter capacitor C1 is released to the residual voltage Ur and immediately closes the switch S1, when the voltage of the filter capacitor C1 drops to the residual voltage Ur, the voltage of the filter capacitor C1 conforms to the switch S1 closed conduction action condition.

Compared with the prior art, the present invention has significant advantages and beneficial effects in that:

(1) The present invention proposes a switching circuit with the function of releasing the residual voltage. A freely controllable switch is set between the positive and negative poles of the output end of the switching power supply. When the switching power supply supplies power to the load, the switch is turned off, thereby The internal impedance or residual voltage discharge resistor does not participate in energy consumption, and the switch is closed only when the residual voltage needs to be released to consume static current. In this way, the problem of additional loss caused by using a dummy load is solved.

(2) The resistance used in the present invention for residual voltage discharge can be realized by the impedance of the existing electrical components in the switching circuit itself, and no additional electrical components are needed in the limited space of the switching power supply, avoiding the need to occupy PCB board space and increase costs question. Of course, additional electrical components can also be used to realize the residual voltage discharge resistor. At this time, because of its own working scene, there is no need to consider derating, and only a small space is needed, which also reduces the use of PCB board space and reduces the number of devices at the same time. cost.

(3) On the basis of releasing the residual voltage by the dummy load, the present invention solves the problem of the fixed loss caused by the dummy load discharge and reduces the efficiency of the switching power supply converter, and at the same time improves the problem of limited circuit space layout of the switching power supply PCB board. problem, and reduces the switching power supply hardware cost.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Description of drawings

The drawings are for the purpose of illustrating specific embodiments only and are not to be considered as limitations of the invention, and like reference numerals refer to like parts throughout the drawings.

FIG. 1 is a schematic circuit diagram of a switching power supply using a dummy load to release residual voltage in the prior art.

FIG. 2 is a schematic diagram of a working state circuit in Embodiment 1 of the present invention.

FIG. 3 is a schematic diagram of another working state circuit in Embodiment 1 of the present invention.

FIG. 4 is a schematic diagram of a working state circuit in Embodiment 2 of the present invention.

FIG. 5 is a schematic diagram of another working state circuit according to Embodiment 2 of the present invention.

Fig. 6 is a schematic diagram of logic control of a switch in the present invention.

Fig. 7 is a schematic diagram of the detection and control circuit in the present invention.

Fig. 8 is a schematic diagram of a specific embodiment of the control circuit in the present invention.

Detailed ways

It is easy to understand that, according to the technical solution of the present invention, those skilled in the art can imagine various implementations of the present invention without changing the essence and spirit of the present invention. Therefore, the following specific embodiments and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the entirety of the present invention or as a limitation or limitation on the technical solution of the present invention. Rather, these embodiments are provided to enable those skilled in the art to more thoroughly understand the present invention. Preferred embodiments of the present invention will be specifically described below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the application and are used together with the embodiments of the present invention to explain the innovative concept of the present invention.

Example 1

As shown in Figure 2 and Figure 3, the switching circuit has the internal impedance R3 of the power supply, the filter capacitor C1 at the output end, and the real load R2 powered by the output end. In Figure 2 and Figure 3, the state of the switch symbol S2 is used to indicate whether the switching power supply outputs current to its output load R2, which does not mean that there must be a physical switch in the circuit, S2 in the physical device sense can exist, or Can not exist.

Here, the switching circuit may be an isolated type or a non-isolated type, for example, a rectifier, a transformer, a DC-DC converter, a buck, a boost circuit, etc. may be mentioned.

Whether the switch circuit works or not is controlled by the indication signal. Specifically, for example, switching elements such as MOS transistors and triodes can be connected in series inside the converter, and an indication signal can be input to the control terminal of the switching element to control the on and off of the switching element, thereby controlling the operation of the converter. state.

After the switching power supply stops supplying power to the load R2 at the output end, the quiescent current of the switching power supply will slowly charge the filter capacitor C1 at the output end, eventually forming a residual voltage Ur. In order to eliminate the residual voltage Ur, in this embodiment, a discharge circuit for releasing the residual voltage Ur is provided between the positive and negative poles of the output terminal of the switching power supply. The discharge circuit includes a switch S1 and a discharge resistor R1 connected in series. The changeover switch S1 is a freely controllable switch.

When the switching power supply supplies power to the output load R2, that is, when the switching power supply carries the normal output current of the output load R2, the voltage across the filter capacitor C1 at the output end is the output voltage Vout of the switching power supply. At this time, the switch S1 in the discharge circuit is placed in an off state, the discharge circuit is not conducted, and the discharge resistor R1 is not connected to the working circuit as a discharge element. When the switching power supply stops supplying power to the output load R2, as shown in Figure 3, the switch symbol S2 is disconnected, and the switching power supply does not output current to the load R2. At this time, the filter capacitor C1 at the output terminal will slowly discharge through the internal impedance R3 of the power supply. However, due to the existence of the internal quiescent current, the voltage of the filter capacitor C1 cannot be released to 0V, and finally a stable voltage is formed at both ends of the filter capacitor C1, that is, the residual voltage Ur. At this time, as shown in Figure 3, the switch S1 is closed, the switch S1 and the discharge resistor R1 form a loop at both ends of the filter capacitor C1 at the output end, and the discharge circuit is grounded through the switch S1, so that the quiescent current and the residual voltage form a pair In the ground discharge loop, the residual voltage at both ends of the output filter capacitor C1 that could not be completely released will eventually be released to 0V. In short, when the switching power supply is not supplying external power, the discharge circuit makes the quiescent current and the residual voltage form a discharge circuit to the ground by switching the switch S1.

Example 2

Referring to FIG. 4 and FIG. 5 , the difference between Embodiment 2 and Embodiment 1 lies in that the composition of the discharge circuit arranged between the positive and negative poles of the output terminal of the switching power supply is different. In Embodiment 2, instead of forming a discharge circuit by adding an additional discharge resistor R1 as in Embodiment 1, the internal impedance R3 of the switching power supply and the switch S1 are used to form a discharge circuit, that is, after the internal impedance R3 is connected in series with the switch S1 A discharge circuit is formed. When the switch S1 is closed, the switch S1 and the internal impedance R3 form a loop at both ends of the filter capacitor C1 at the output end, and the discharge circuit is grounded through the switch S1, so that the quiescent current and the residual voltage Ur form a discharge circuit to the ground .

Specifically, as shown in FIG. 4 and FIG. 5 , in this embodiment, after the switching power supply stops supplying power to the output load R2 , the quiescent current of the switching power supply will slowly charge the filter capacitor C1 , finally forming a residual voltage Ur. In order to eliminate the residual voltage Ur, a discharge circuit is provided in this embodiment, and the discharge circuit includes a switch S1 and an internal impedance R3 of the switching power supply. The changeover switch S1 is a freely controllable switch.

When the switching power supply carries the normal output current of the output load R2, the voltage across the filter capacitor C1 at the output end is the output voltage Vout of the switching power supply. At this time, the switch S1 is placed in an off state. When the switching power supply stops outputting current to the output load R2, as shown in Figure 5, the switch symbol S2 is disconnected, indicating that the switching power supply does not output current to the outside. At this time, the filter capacitor C1 at the output end will slowly discharge through the internal impedance R3 of the power supply. However, due to the existence of the internal quiescent current, the voltage of the filter capacitor C1 at the output end cannot be released to 0V, and finally a stable residual voltage Ur is formed at both ends of the filter capacitor C1. At this time, the switch S1 is closed, the switch S1 and the internal impedance R3 form a loop at both ends of the filter capacitor C1 at the output end, and the discharge circuit is grounded through the switch S1, and the voltage on the filter capacitor C1 that cannot be fully discharged will pass through the switch S1 Grounded, so that the quiescent current and the residual voltage Ur form a discharge circuit to the ground, and the residual voltage Ur on the filter capacitor C1 is finally released to 0V.

It should be further explained that, due to the difference in the composition of the residual voltage discharge circuit in the embodiment 1 and the embodiment 2, the discharge time of the residual voltage corresponding to the embodiment 1 and the embodiment 2 is different. Therefore, Embodiment 1 and Embodiment 2 have different application scenarios. From the point of view of relative comparison, in Embodiment 1, since the discharge resistor R1 is a separately set resistor, its resistance value can be set as required. Specifically, the resistance value can be specifically selected according to the discharge time requirement of the residual voltage Ur. The discharge time t is approximately equal to R1*C1, where C1 is the size of the filter capacitor at the output end. Therefore, Embodiment 1 is suitable for application scenarios that have requirements on residual voltage discharge time.

In embodiment 2, the discharge resistance is formed by the internal impedance R3, but the internal impedance R3 is not a certain fixed resistance value, its impedance value is a dynamically changing value, which is related to the topology form of the switching power supply, the output filter parameters of the power supply, and the power supply The parameters of the internal components are related, generally ranging from several thousand ohms to hundreds of thousand ohms, so that the time when the residual voltage Ur is finally released to 0v cannot be determined. Therefore, Embodiment 2 is suitable for application scenarios where there is no requirement for residual voltage discharge time.

In addition, in Embodiment 1, the discharge resistor R1 is a separate resistance, so if the discharge circuit fails and the residual voltage Ur cannot be released as required, the cause of the fault can be easily found, which is convenient for circuit maintenance. In Example 2, since the discharge resistance is formed by the impedance of other internal components, if the discharge circuit fails and the residual voltage Ur cannot be released as required, it is difficult to find out which component fails and the discharge circuit cannot work normally. . Of course, the advantage of embodiment 2 over embodiment 1 is that no additional discharge resistor R1 is required, and the discharge resistor is formed by the impedance of other internal components, which eliminates the need for additional components and facilitates the packaging and miniaturization of switching power supplies.

In the drawings corresponding to Embodiment 1 and Embodiment 2, the switch symbol S2 is only used to indicate whether the switching power supply supplies power to the load or not. In practical applications, the user who uses the switching power supply controls the control pin on the switching power supply through a self-built circuit or digital commands to switch the output working state of the power supply. The working state includes outputting current for the load R2 and not outputting the current for the load R2 .

Example 3

As shown in Figure 2 and Figure 3, in Embodiment 1 and Embodiment 2, the same discharge circuit is used, that is, the quiescent current of the switching power supply forms a discharge circuit to the ground, and the residual voltage Ur of the filter capacitor forms a discharge to the ground circuit. Even if one discharge circuit is used, the quiescent current to ground discharge circuit and the residual voltage Ur to ground discharge circuit are realized at the same time. Embodiment 3 As an optional implementation mode, two discharge circuits shown in Embodiment 1 and Embodiment 2 are provided in the switch circuit to respectively realize the static current to ground discharge circuit and the residual voltage Ur to ground discharge circuit.

For example, the first discharge circuit includes a discharge resistor and a switch in series, and the switch in the first discharge circuit is grounded after being closed, so that the quiescent current of the switching power supply forms a discharge circuit to the ground. The second discharge circuit also includes a discharge resistor and a switch in series. The switch in the second discharge circuit is closed and then grounded, so that the residual voltage Ur formed in the filter capacitor forms a discharge circuit to the ground.

In the present invention, for different situations, the closing timing of the switch S1 is different, and the corresponding control mode of the switch S1 is as follows:

Method 1: After the switching power supply stops outputting current to the output load R2, that is, after the state switch S2 is turned off, immediately close the switch S1, turn on the discharge circuit and keep it until the switching power supply outputs current to the load R2 again, that is, the state switch S2 After closing again, immediately open the diverter switch S1.

Method 2: After the switching power supply stops outputting current to the load R2, that is, after the state switch S2 is turned off, the switch S1 is not closed immediately, and when the voltage on the filter capacitor C1 is released to a fixed voltage amplitude Vo, the switch is closed immediately switch S1, and keep it until the switching power supply outputs current to the load R2 again, that is, after the state switch S2 is closed again, then immediately turn off the switch S1. The voltage amplitude Vo here is smaller than the output voltage Vout of the power supply, but larger than the steady-state residual voltage Ur.

Method 3: After the switching power supply stops outputting current to the load R2, that is, after the state switch S2 is turned off, the voltage on the filter capacitor C1 will be released slowly by the internal impedance of the power supply. After a long period of discharge, it still cannot be placed at 0v, and finally forms a stable level, that is, the residual voltage Ur. After detecting that the voltage on the filter capacitor C1 is at a stable residual voltage, close the switch S1 and keep it there until the switching power supply outputs current to the load R2 again, that is, after the state switch S2 is closed again, then open the switch S1 .

The above three control methods have different advantages and disadvantages.

When the state of switch S1 is controlled according to method 1, its advantage is that it is equivalent to treating the output voltage of the switching power supply in a steady state directly as a residual voltage, which saves the process of slowly discharging the filter capacitor C1 itself through the internal impedance of the power supply. After the output current to the output load R2 is stopped, the switch S1 directly forms a discharge circuit to the ground. The disadvantage is that the components inside the power supply (forming the internal impedance R3) or the discharge resistor R1 need to withstand a large discharge current. It should be grounded in a short period of time, the discharge current is large, and there is a large inrush current. Some devices have requirements for the maximum inrush current. If the design of the components is not strong enough, such as a series of devices forming internal impedance, or the design of the discharge resistor R1 is not strong enough to withstand a large inrush current, it may damage the components of the power supply or the discharge resistor R1. Therefore, when the state of the switching switch S1 is controlled according to the first method, there is a higher requirement on the components of the switching power supply itself or the discharge resistor.

When controlling the state of the switching switch S1 according to the second method, the advantage is that a threshold value Vo is set for the output voltage of the switching power supply. The threshold value Vo is a value between the output voltage Vout and the residual voltage Ur. When the output terminal of the switching power supply When the voltage (that is, the voltage of the filter capacitor C1) drops to the threshold Vo, then close the switch S1, which can reduce the discharge current that the internal components of the power supply (forming the internal impedance R3) or the discharge resistor R1 need to bear. The robustness requirement of the discharge resistor R1 can be appropriately reduced. Its disadvantage is that it requires a longer discharge time than the first method.

When the state of the switching switch S1 is controlled according to the third mode, the advantage is that there is a small discharge current and the requirements for the robustness of the components are low. Its disadvantage is that it takes a certain amount of time to detect a stable voltage, and the overall discharge time is longer than that of the second method.

The above are three control modes for switching the switch S1 on and off according to different situations, and specific detection and control circuits are required to implement the above control modes. Referring to FIG. 7 , in the present invention, a detection and control circuit for realizing the control mode of the switch S1 includes a voltage sampling module, a control module and a driving module.

The voltage sampling module is used to collect the voltage signal at both ends of the filter capacitor C1, which can be implemented specifically by using the voltage division sampling method shown in FIG. 7 .

The control module judges the voltage state of the filter capacitor C1 according to the voltage signal of the filter capacitor C1 collected by the voltage sampling module, and sends a control command to the drive module to close or open the switch S1 according to the voltage state of the filter capacitor C1.

As shown in FIG. 8 , the control module further includes an analog-to-digital conversion sub-module (ADC) and a logic judgment unit. The analog-to-digital conversion sub-module converts the voltage signal collected by the voltage sampling module into a digital signal, and the logic judgment unit judges the voltage state of the filter capacitor C1 according to the digital signal.

According to the above-mentioned detection and control circuit, when the control module detects that the voltage state of the filter capacitor C1 meets the condition for the switch S1 to be closed and turned on, the control module sends a logic control high level or low level, which is controlled by the drive module. The signal becomes a high level with driving capability, and the switching switch S1 is driven to be closed and turned on. At this time, the discharge circuit provides a discharge path for the filter capacitor C1 to the ground to eliminate the residual voltage Ur. When the control module detects that the switching power supply is about to supply power to the output load, it also controls the switch S1 to be turned off through the driving circuit, and closes the discharge path, so that the switching power supply normally outputs current to the load.

The aforementioned three control modes of the switch S1 are introduced, and for these three different control modes, there are also three different forms of the action conditions for the switch S1 to be closed and turned on.

When the state of the switch S1 is controlled according to mode 1, the switching power supply stops outputting current to the output load R2 and immediately closes the switching switch S1. In this mode, when the control module detects that the voltage of the filter capacitor C1 is lower than the output voltage Vout of the switching power supply, That is, after determining that the voltage state of the filter capacitor C1 meets the condition for the switch S1 to be closed and turned on, the control module sends a logic control level to the drive module.

When the state of the switch S1 is controlled according to the second method, when the voltage on the filter capacitor C1 is released to a fixed voltage amplitude Vo, the switch S1 is immediately closed. In this mode, when the control module detects the voltage of the filter capacitor C1 When it drops to the voltage amplitude Vo, it is determined that the voltage state of the filter capacitor C1 meets the condition for the switch S1 to be closed and turned on, and the control module sends a logic control level to the drive module.

When the state of the switch S1 is controlled according to mode three, when the voltage on the filter capacitor C1 is released to the residual voltage Ur, the switch S1 is immediately closed. In this mode, when the control module detects that the voltage of the filter capacitor C1 drops to the residual voltage Ur, that is, it is determined that the voltage state of the filter capacitor C1 meets the action condition of the switching switch S1 being closed and conducting, and the control module sends a logic control level to the drive module.

In practical applications, the switching power supply will supply power to the output load. The user who uses the switching power supply controls the control pin on the switching power supply through a self-built circuit or digital command to switch the output working state of the power supply. The working state includes the load R2 output current and no output current for the load R2.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto.

Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in the present invention shall fall within the protection scope of the present invention.

It should be appreciated that in the foregoing description of exemplary embodiments of the invention, in order to streamline the present disclosure and to assist those skilled in the art in understanding its various aspects, various features of the invention are sometimes described in the context of a single embodiment, or with reference to A single graph is described. However, the present invention should not be interpreted that the features included in the exemplary embodiments are all essential technical features of the patent claims.

Those skilled in the art can understand that all or part of the processes of the methods in the above embodiments can be implemented by instructing related hardware through computer programs, and the programs can be stored in a computer-readable storage medium. Wherein, the computer-readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory, and the like.

It should be understood that the modules, units, components, etc. included in the device of one embodiment of the present invention can be adaptively changed so as to be arranged in a device different from that of the embodiment. Different modules, units or components included in the device of the embodiment can be combined into one module, unit or component, or they can be divided into multiple sub-modules, sub-units or sub-components.

The modules, units or components in the embodiments of the present invention may be implemented in hardware, software running on one or more processors, or a combination thereof. Those skilled in the art should understand that,

Embodiments according to the present invention may be implemented in practice using a microprocessor or a digital signal processor (DSP). The present invention can also be embodied on a computer program product or computer readable medium for performing some or all of the methods described herein.

Claims (8)

1. A switch circuit with a function of releasing residual voltage, characterized in that it comprises a filter capacitor positioned at the output end of the switch circuit, and a discharge circuit for forming a loop with the filter capacitor, after the discharge circuit is connected in series with a discharge resistor and a switch Composition; the switch is closed and grounded, so that the quiescent current of the switching power supply and/or the residual voltage formed in the filter capacitor form a discharge circuit to the ground; A discharge resistance in the discharge circuit is formed by an internal impedance of the switch circuit. 2. The switch circuit according to claim 1, characterized in that, in the working state of the switch circuit outputting current to the load, the changeover switch is turned off; in the non-working state in which the switch circuit stops outputting the load current, The toggle switch is closed. 3. The switch circuit according to claim 2, wherein, when the switch circuit stops outputting current to the load, it immediately closes the switch, turns on the discharge circuit and maintains it; when the switch circuit outputs current to the load again, Disconnect the toggle switch immediately. 4. The switch circuit according to claim 2, wherein after the switch circuit stops outputting current to the load, when the voltage on the filter capacitor is released to the voltage threshold Vo, the switch is closed immediately, the discharge circuit is turned on and kept ; When the switch circuit outputs current to the load again, immediately turn off the switch; the voltage threshold Vo is less than the output voltage when the switch circuit is working, and greater than the residual voltage of the filter capacitor. 5. The switch circuit according to claim 2, wherein after the switch circuit stops outputting current to the load, when the voltage on the filter capacitor is released to the residual voltage, the switch is closed, the discharge circuit is turned on and maintained; When the switch circuit outputs current to the load again, the switch is turned off immediately. 6. Any switch circuit according to claim 1-5, further comprising a control circuit for controlling the switch to be disconnected or closed, the control circuit comprising a voltage sampling module, a control module and a drive module; The voltage sampling module is used to collect the voltage data of the filter capacitor C1 at the output end of the switching circuit; The control module is used to judge according to the voltage data of the filter capacitor C1 collected by the voltage sampling module, whether the voltage of the filter capacitor C1 meets the operation condition of the switching switch S1 being closed and conducting, and if so, sends a control signal to the drive module; The drive module controls the switching switch to close according to the control signal. 7. The switch circuit according to claim 6, wherein the method for controlling the switching on or off of the switch is: Step S1: the control module determines whether the switch circuit stops outputting current to the load; if the switch circuit stops outputting current to the load, proceed to step S2; if the switch circuit is outputting current to the load, continuously detects whether the switch circuit stops outputting current to the load; Step S2: The control module judges whether the voltage at both ends of the filter capacitor C1 meets the action condition for the switch S1 to be closed and turned on; when the voltage at both ends of the filter capacitor C1 meets the action condition for the switch S1 to be turned on and off, the control module sends a signal to the drive module control signal; the drive module closes the switch S1 according to the control signal; Step S3: When the switch S1 is closed, the control module continues to judge whether the switch circuit starts to output current to the load, and if the switch circuit starts to output current to the load, it sends a control signal to the drive module; the drive circuit disconnects the switch according to the control signal . 8. The switch circuit according to claim 6, wherein the voltage of the filter capacitor C1 meets the operating conditions for the switching switch S1 to be closed and turned on: In the control mode where the switching power supply stops outputting current to the output load R2 and immediately closes the switching switch S1, when the voltage of the filter capacitor C1 is lower than the output voltage Vout of the switching power supply, the voltage of the filtering capacitor C1 meets the action condition that the switching switch S1 is closed and conducting ; In the control mode where the voltage on the filter capacitor C1 is released to the voltage amplitude Vo and immediately closes the switch S1, when the voltage of the filter capacitor C1 drops to the voltage amplitude Vo, the voltage of the filter capacitor C1 conforms to the switch S1 closed conduction Common operating conditions; In the control mode where the voltage on the filter capacitor C1 is released to the residual voltage Ur and immediately closes the switch S1, when the voltage of the filter capacitor C1 drops to the residual voltage Ur, the voltage of the filter capacitor C1 conforms to the switch S1 closed conduction action condition.

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