CN113572348B

CN113572348B - Switching circuit with residual voltage releasing function

Info

Publication number: CN113572348B
Application number: CN202110847289.0A
Authority: CN
Inventors: 李强
Original assignee: Jieyandi Electronic Technology Shanghai Co ltd
Current assignee: Jieyandi Electronic Technology Shanghai Co ltd
Priority date: 2021-07-27
Filing date: 2021-07-27
Publication date: 2023-05-09
Anticipated expiration: 2041-07-27
Also published as: CN113572348A

Abstract

The invention relates to a switching circuit with a residual voltage releasing function, which comprises a filter capacitor positioned at the output end of the switching circuit and a discharge circuit used for forming a loop with the filter capacitor, wherein the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; and the switching switch is grounded after being closed, so that the static current of the switching power supply and/or the residual voltage formed on the filter capacitor form a discharge loop to ground. When the switching circuit supplies power to the load, the change-over switch is opened, so that the internal impedance or the residual voltage discharging resistor does not participate in energy consumption, and the change-over switch is closed only when the residual voltage needs to be released, so that the static current is consumed.

Description

Switching circuit with residual voltage releasing function

Technical Field

The present invention relates to a switching circuit having a function of releasing a residual voltage.

Background

The switching circuit is a high-frequency electric energy conversion device, which mainly utilizes a power electronic switching device, such as a transistor, a MOS tube, a controllable thyristor and the like, and the electronic switching device is periodically turned on and off through a control circuit, so that the power electronic switching device carries out pulse modulation on input voltage, thereby realizing the functions of voltage conversion, adjustable output voltage and automatic voltage stabilization. After the switching circuit stops supplying power to the load, voltage residual voltage is formed on the filter capacitor at the output end of the power supply. Fig. 1 is a schematic diagram of an output end of a conventional switching power supply, and the quiescent current is an internal current of the switching power supply under the condition of no output, and is very small, and is generally different from a few mA to tens mA. However, as long as the input end of the switching power supply is supplied with power, the static current always exists. After the switching power supply stops supplying power to the load, the filter capacitor C1 at the output end slowly discharges through the impedance inside the power supply. However, due to the internal quiescent current, the voltage of the filter capacitor C1 cannot be released to 0V, and a stable voltage, commonly referred to as the residual voltage Ur, is formed across the filter capacitor C1.

Currently, the residual voltage Ur is eliminated by adding a "dummy load" to the power supply output to consume the quiescent current. As shown in fig. 1, a resistor R1 with a proper resistance value and proper encapsulation is added between the positive electrode and the negative electrode of the power output end, and is used for forming a loop with the filter capacitor of the power output end after the power supply of the switching power supply stops supplying power to the load so as to release the voltage residual voltage. However, this way of releasing the residual voltage Ur has the following drawbacks:

(1) In order to improve the reliability of the dummy load resistor as much as possible, great derating consideration needs to be made on the power consumption of the resistor, the resistor is easy to be packaged to be larger, occupies a larger space placement position, and increases the wiring layout difficulty of a PCB of the switching power supply;

(2) The dummy load resistor is used as an additional fixed load, so that a loss is additionally introduced, and the output conversion efficiency of the switching power supply is reduced due to the additional loss;

(3) The dummy load resistor is used as a special device, so that the manufacturing cost of the switching power supply is increased to a certain extent.

Disclosure of Invention

The invention provides a switching circuit with a residual voltage releasing function.

The first aspect of the invention provides a switching circuit with a residual voltage releasing function, which comprises a filter capacitor positioned at the output end of the switching circuit and a discharge circuit used for forming a loop with the filter capacitor, wherein the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; and the switching switch is grounded after being closed, so that the static current of the switching power supply and/or the residual voltage formed on the filter capacitor form a discharge loop to ground.

As one embodiment, the discharge resistor in the discharge circuit is a resistor having a resistance value for determining a residual voltage discharge time.

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

As one embodiment, the changeover switch is turned off in an operating state in which the switching circuit outputs a current to the load; and in a non-working state that the switching circuit stops outputting current to the load, the change-over switch is closed.

As one embodiment, when the switch circuit stops outputting current to the load, the switch circuit immediately closes the change-over switch, and turns on the discharge circuit and keeps; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.

As one implementation mode, 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 switching circuit outputs current to the load again, the change-over switch is immediately turned off; the voltage threshold Vo is smaller than the output voltage of the switching circuit during operation and is larger than the residual voltage of the filter capacitor.

As one implementation mode, 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, and the discharge circuit is conducted and maintained; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.

A second aspect of the present invention provides a control circuit for controlling the switch to be opened or closed, including a control circuit for controlling the switch to be opened or closed, where the control circuit includes a voltage sampling module, a control module, and a driving module;

the voltage sampling module is used for collecting voltage data of the filter capacitor C1 at the output end of the switch circuit;

the control module is used for judging whether the voltage of the filter capacitor C1 accords with the action condition of closing and conducting the change-over switch S1 according to the voltage data of the filter capacitor C1 acquired by the voltage sampling module, and if so, sending a control signal to the driving module;

and the driving module controls the switching switch to be closed according to the control signal.

As one embodiment, the method for controlling the switch to be turned on or off is as follows:

step S1: the control module judges whether the switching circuit stops outputting current to the load; if the switching circuit stops outputting current to the load, the step S2 is entered; if the switching circuit is outputting current to the load, continuously detecting whether the switching circuit stops outputting current to the load;

step S2: the control module judges whether the voltages at two ends of the filter capacitor C1 accord with the action condition of closing and conducting the change-over switch S1; after the voltages at two ends of the filter capacitor C1 enter the action condition of being in accordance with the closing and conducting of the change-over switch S1, the control module sends a control signal to the driving module; the driving module closes the change-over switch S1 according to the control signal;

step S3: under the state that the change-over switch S1 is closed, the control module continuously judges whether the switch circuit starts outputting current to the load, and if the switch circuit starts outputting current to the load, a control signal is sent to the driving module; the driving circuit turns off the change-over switch according to the control signal.

As an embodiment, the voltage of the filter capacitor C1 meets the action condition that the switch S1 is turned on and turned off:

in the control mode that the switching power supply stops outputting current to the output load R2 and then immediately closes the switch S1, when the voltage of the filter capacitor C1 is smaller than the output voltage Vout of the switching power supply, the voltage of the filter capacitor C1 accords with the action condition that the switch S1 is closed and conducted;

under the control mode that the voltage on the filter capacitor C1 immediately closes the switch S1 when being released to the voltage amplitude Vo, when the voltage of the filter capacitor C1 is reduced to the voltage amplitude Vo, the voltage of the filter capacitor C1 accords with the action condition that the switch S1 is closed and conducted;

in the control mode that the switch S1 is closed immediately when the voltage on the filter capacitor C1 is released to the residual voltage Ur, when the voltage of the filter capacitor C1 drops to the residual voltage Ur, the voltage of the filter capacitor C1 conforms to the action condition that the switch S1 is closed and turned on.

Compared with the prior art, the invention has the remarkable advantages and beneficial effects that:

(1) The invention provides a switching circuit with a residual voltage releasing function, wherein a freely controllable change-over switch is arranged between the positive electrode and the negative electrode of the output end of a switching power supply, and the change-over switch is opened when the switching power supply supplies power to a load, so that the internal impedance or a residual voltage discharging resistor does not participate in energy consumption, and the change-over switch is closed only when the residual voltage needs to be released so as to consume static current. Thus solving the problem of extra loss caused by using dummy load.

(2) The resistor for discharging residual voltage can be realized by the impedance of the existing electrical components in the switch circuit, and the electrical components are not additionally added in the limited space of the switch power supply, so that the problems of occupying the space of a PCB and increasing the cost are avoided. Of course, the residual voltage discharge resistor can be realized by using additional electric elements, and at the moment, the de-rating is not needed to be considered because of the working scene of the residual voltage discharge resistor, only a smaller space is needed, the space of the PCB is also reduced, and meanwhile, the cost of the device is reduced.

(3) The invention solves the problems that the fixed loss caused by dummy load discharge can reduce the efficiency of the switch power supply converter and simultaneously improves the problem that the space arrangement of the PCB circuit of the switch power supply is limited and reduces the hardware cost of the switch power supply on the basis of releasing the residual voltage by the dummy load.

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

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.

Fig. 1 is a schematic circuit diagram of a prior art switching power supply using dummy loads to discharge residual voltages.

Fig. 2 is a circuit schematic of an operating state of embodiment 1 of the present invention.

Fig. 3 is a circuit diagram illustrating another operation state according to embodiment 1 of the present invention.

Fig. 4 is a circuit schematic diagram of an operating state of embodiment 2 of the present invention.

Fig. 5 is a circuit diagram illustrating another operation state according to embodiment 2 of the present invention.

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

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

FIG. 8 is a schematic diagram of a control circuit according to an embodiment of the present invention.

Detailed Description

It is easy to understand that various embodiments of the present invention can be envisioned by those of ordinary skill in the art without altering the true spirit of the present invention in light of the present teachings. Accordingly, the following detailed description and drawings are merely illustrative of the invention and are not intended to be exhaustive or to limit or restrict the invention. Rather, these embodiments are provided so that this disclosure will be thorough and complete by those skilled in the art. Preferred embodiments of the present invention are described in detail below with reference to the attached drawing figures, which form a part of the present application and are used in conjunction with embodiments of the present invention to illustrate the innovative concepts of the present invention.

Example 1

As shown in fig. 2 and 3, the switching circuit has a power supply internal impedance R3, a filter capacitor C1 at the output terminal, and a real load R2 supplied from the output terminal. In fig. 2 and 3, the state of the switch symbol S2 is used to indicate whether the switching power supply outputs a current to its output load R2, and does not represent that there is a switch in the circuit in a physical sense that must actually exist, and S2 in the sense of a physical device may or may not exist.

The switching circuit may be an isolated circuit or a non-isolated circuit, and examples thereof include a rectifier, a transformer, a DC-DC converter, a buck circuit, and a boost circuit.

Whether the switch circuit works or not is controlled by the indication signal. Specifically, for example, a switching element such as a MOS transistor or a triode may be connected in series inside the inverter, and an instruction signal may be input to a control terminal of the switching element to control on/off of the switching element, thereby controlling the operation state of the inverter.

After the switching power supply stops supplying power to the output end load R2, the static current of the switching power supply slowly charges the output end filter capacitor C1, and finally, a residual voltage Ur is formed. In order to eliminate the residual voltage Ur, the present embodiment provides a discharge circuit for discharging the residual voltage Ur between the positive and negative electrodes of the switching power supply output terminal, the discharge circuit including a changeover 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, the switching power supply outputs current normally with the output load R2, the voltage across the filter capacitor C1 at the output end is the power supply output voltage Vout. At this time, the changeover switch S1 in the discharge circuit is placed in an off state, the discharge circuit is not turned on, and the discharge resistor R1 is not connected to the operation circuit as a discharge element. When the switching power supply stops supplying power to the output load R2, as shown in fig. 3, the switching symbol S2 is turned off, the switching power supply does not output current to the load R2, and at this time, the filter capacitor C1 at the output end slowly discharges through the impedance R3 inside the power supply. However, due to the internal quiescent current, the voltage of the filter capacitor C1 cannot be released to 0V, and a stable voltage, i.e., a residual voltage Ur, is formed at both ends of the filter capacitor C1. At this time, as shown in fig. 3, the switch S1 is closed, the switch S1 and the discharging resistor R1 form a loop at two ends of the output filter capacitor C1, and the discharging circuit is grounded through the switch S1, so that the static current and the residual voltage form a ground discharging loop, and the residual voltage which cannot be completely released originally at two ends of the output filter capacitor C1 will be finally released to 0V. In short, when the switching power supply does not supply power to the outside, the discharging circuit makes the static current and the residual voltage constitute a discharging loop to the ground by switching the switch S1.

Example 2

In combination with fig. 4 and 5, embodiment 2 differs from embodiment 1 in that the composition of a discharge circuit provided between the positive and negative electrodes of the output terminal of the switching power supply is different. In embodiment 2, instead of forming the discharge circuit by adding the additional discharge resistor R1 as in embodiment 1, the internal impedance R3 of the switching power supply and the switch S1 are utilized to form the discharge circuit, that is, the internal impedance R3 and the switch S1 are connected in series to form the discharge circuit, when the switch S1 is closed, the switch S1 and the internal impedance R3 form a loop at both ends of the output filter capacitor C1, and the discharge circuit is grounded through the switch S1, so that the quiescent current and the residual voltage Ur form a discharge loop to ground.

Specifically, as shown in fig. 4 and 5, in the present embodiment, after the switching power supply stops supplying power to the output load R2, the quiescent current of the switching power supply slowly charges the filter capacitor C1, and finally the residual voltage Ur is formed. In order to eliminate the residual voltage Ur, the present embodiment is provided with a discharge circuit including a changeover switch S1 and a switching power supply internal impedance R3. The changeover switch S1 is a freely controllable switch.

When the switching power supply outputs current with the output load R2 normally, the voltage across the output end filter capacitor C1 is the power supply output voltage Vout. At this time, the changeover switch S1 is placed in the off state. When the switching power supply stops outputting current to the output load R2, as shown in fig. 5, the switching symbol S2 is turned off, which indicates that the switching power supply does not output current externally, and the filter capacitor C1 at the output end slowly discharges through the impedance R3 inside the power supply, but 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 two 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 two ends of the filter capacitor C1 at the output end, and the discharging circuit is grounded through the switch S1, the voltage which cannot be discharged on the filter capacitor C1 originally is grounded through the switch S1, so that the static current and the residual voltage Ur form a discharging loop to the ground, and the residual voltage Ur on the filter capacitor C1 is finally released to 0V.

It should be further noted that, since the discharge loop compositions of the residual voltages in example 1 and example 2 are different, the discharge time of the residual voltages in example 1 and example 2 are different. Therefore, the embodiment 1 and the embodiment 2 have different application scenarios. In embodiment 1, the discharge resistor R1 is a resistor provided alone, and thus the resistance value thereof can be set as needed in view of comparison. In particular, the resistance value may be specifically selected according to the discharge time requirement of the residual voltage Ur. The discharge time t is approximately equal to R1 x C1, where C1 is the size of the output filter capacitor. Therefore, embodiment 1 is suitable for an application scenario requiring a discharge time of the residual voltage.

In embodiment 2, the discharge resistor is formed by the internal impedance R3, but the internal impedance R3 is not necessarily a fixed resistance value, and its impedance value is a dynamically changing value, which is related to the topology of the switching power supply, the output filter parameters of the power supply, the parameters of the components used inside the power supply, and the like, and is generally different from several kiloohms to several hundred kiloohms, so that the time for the residual voltage Ur to be finally discharged to 0v cannot be determined. Therefore, embodiment 2 is suitable for an application scenario where no residual voltage discharge time is required.

In addition, in embodiment 1, the discharge resistor R1 is a resistor which is separately set, so if the discharge circuit fails and the residual voltage Ur cannot be released as required, the failure cause can be very simply found, and the circuit maintenance is facilitated. In embodiment 2, since the discharge resistor is formed by impedance of other internal components, if the discharge circuit fails and the residual voltage Ur cannot be discharged as required, it is difficult to check which component fails and the discharge circuit cannot operate normally. Of course, embodiment 2 has an advantage over embodiment 1 in that the discharge resistor R1 is not additionally provided, the discharge resistor is formed by the impedance of other components inside, no additional components are required, and the switching power supply can be easily packaged and miniaturized.

In the drawings corresponding to embodiment 1 and embodiment 2, the switch symbol S2 is merely used to indicate whether the switching power supply supplies or does not supply power to the load. In practical applications, a user using the switching power supply controls a control pin on the switching power supply through a self-tapping circuit or a digital command to switch the output operating state of the power supply, where the operating state includes outputting a current for the load R2 and not outputting a current for the load R2.

Example 3

As shown in fig. 2 and 3, in embodiment 1 and embodiment 2, the same discharge loop is used, that is, the static current of the switching power supply is formed into a ground discharge loop, and the residual voltage Ur of the filter capacitor is formed into a ground discharge loop. I.e. one discharge loop is used, while a quiescent current discharge loop to ground and a residual voltage Ur discharge loop to ground are realized. Example 3 as an alternative embodiment, two discharge circuits shown in example 1 and example 2 are provided in the switching circuit, respectively realizing a quiescent current to ground discharge circuit and a residual voltage Ur to ground discharge circuit.

For example, the first discharging loop comprises a discharging resistor and a change-over switch which are connected in series, and the change-over switch in the first discharging loop is grounded after being closed, so that static current of the switching power supply forms a discharging loop to the ground. The second discharging circuit comprises a discharging resistor and a switching switch which are connected in series, and the switching switch in the second discharging circuit is grounded after being closed, so that the residual voltage Ur formed in the filter capacitor forms a grounding discharging circuit.

In the present invention, for different situations, the closing timing of the switch S1 is different, and the control mode of the switch S1 is further corresponding to that:

mode one: after the switching power supply stops outputting current to the output load R2, namely after the state switch S2 is opened, the switching switch S1 is immediately closed, and the discharge circuit is conducted and kept all the time; the changeover switch S1 is opened immediately until the switching power supply outputs current to the load R2 again, i.e., the status switch S2 is closed again.

Mode two: after the switching power supply stops outputting the current to the load R2, that is, after the state switch S2 is opened, the switch S1 is not immediately closed, and when the voltage on the filter capacitor C1 is released to a fixed voltage amplitude Vo, the switch S1 is immediately closed and kept until the switching power supply outputs the current to the load R2 again, that is, after the state switch S2 is closed again, the switch S1 is immediately opened. The voltage amplitude Vo here is smaller than the power supply output voltage Vout but larger than the steady-state residual voltage Ur.

Mode three: after the switching power supply stops outputting current to the load R2, i.e. after the state switch S2 is turned off, the voltage on the filter capacitor C1 is slowly released by the internal impedance of the power supply, but because of the existence of the quiescent current, the filter capacitor C1 still cannot be discharged to 0v after a long period of discharge, and finally a stable level, i.e. the residual voltage Ur, is formed. When it is detected that the voltage across the filter capacitor C1 is already at a stable residual voltage, the switch S1 is closed and maintained until the switching power supply outputs current to the load R2 again, i.e. the state switch S2 is closed again, and the switch S1 is opened again.

The three control modes have different advantages and disadvantages.

When the state of the switch S1 is controlled according to the first mode, the method has the advantages that the output voltage of the stabilized switching power supply is treated as residual voltage directly, the process that the filter capacitor C1 discharges slowly through the internal impedance of the power supply is saved, and a ground discharge loop is directly formed by the switch S1 after the switching power supply stops outputting current to the output load R2. The disadvantage is that components inside the power supply (forming the internal impedance R3) or the discharge resistor R1 need to withstand a large discharge current. Should be grounded in a short period of time, the discharge current is large, there is a large rush current, and some devices have a requirement for the maximum value of the rush current. If the component design is not strong enough, such as a series of devices forming an internal impedance, or the discharge resistor R1 is not strong enough to withstand large rush currents, the components of the power supply or the discharge resistor R1 may be damaged. Therefore, when the state of the switch S1 is controlled in the first mode, there is a high demand for components of the switching power supply itself or for the discharge resistance.

When the state of the switch S1 is controlled in the second mode, the advantage is that the threshold Vo is set for the output voltage of the switching power supply, the threshold Vo is a value between the output voltage Vout and the residual voltage Ur, and when the voltage at the output end of the switching power supply (i.e. the voltage of the filter capacitor C1) is reduced to the threshold Vo, the switch S1 is closed again, so that the discharge current required to be born by the components (forming the internal impedance R3) or the discharge resistor R1 in the power supply can be reduced, and the robustness requirement on the components or the discharge resistor R1 can be properly reduced. The disadvantage is that a longer discharge time is required than in the case of the first embodiment.

When the state of the switch S1 is controlled according to the third mode, there is an advantage in that there is a small discharge current and the requirement for robustness of the components is low. The disadvantage is that it takes a certain time to detect the stable voltage, the overall discharge time being longer than in mode two.

The above three control modes of switching on and off the switch S1 are specific to different situations, and specific detection and control circuits are needed to implement the control modes. Referring to fig. 7, in the present invention, a detection and control circuit for implementing 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 for collecting voltage signals at two ends of the filter capacitor C1, and can be specifically realized by adopting a partial pressure sampling mode 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 instruction for closing or opening the change-over switch S1 to the driving module 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 determination unit. The analog-to-digital conversion sub-module converts the voltage signal acquired 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 detection and control circuit, when the control module detects that the voltage state of the filter capacitor C1 accords with the closed conduction operation condition of the switch S1, the control module sends out logic control high level or low level, the logic level changes a logic signal into high level with driving capability through the driving module, the switch S1 is driven to be closed and conducted, and at the moment, the discharging circuit provides a discharging passage of the filter capacitor C1 to the ground to eliminate residual voltage Ur. When the control module detects that the switching power supply is about to supply power to the output load, the driving circuit controls the change-over switch S1 to be switched off, and the discharging passage is closed, so that the switching power supply outputs current to the load normally.

The foregoing describes three control modes of the switch S1, and for these three different control modes, the switch S1 has three different closing and conducting conditions.

When the state of the switch S1 is controlled in a mode one, the switch power supply stops outputting current to the output load R2 and then immediately closes the switch S1, in this mode, when the control module detects that the voltage of the filter capacitor C1 is smaller than the output voltage Vout of the switch power supply, namely, the voltage state of the filter capacitor C1 is determined to be in accordance with the closing and conducting action condition of the switch S1, the control module sends a logic control level to the driving module.

When the state of the switch S1 is controlled according to the mode II, the switch S1 is closed immediately when the voltage on the filter capacitor C1 is released to a fixed voltage amplitude Vo, in this way, when the control module detects that the voltage of the filter capacitor C1 is reduced to the voltage amplitude Vo, namely, the voltage state of the filter capacitor C1 is determined to be in accordance with the closed-on action condition of the switch S1, the control module sends a logic control level to the driving module.

When the state of the switch S1 is controlled according to the third mode, the switch S1 is closed immediately when the voltage on the filter capacitor C1 is released to the residual voltage Ur, 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 condition of closing and conducting the switch S1, the control module sends a logic control level to the driving module.

In practical applications, the switching power supply is to supply power to an output load, and a user using the switching power supply controls a control pin on the switching power supply through a self-tapping circuit or a digital command to switch the output working state of the power supply, wherein the working state includes outputting current for the load R2 and not outputting current for the load R2.

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

any changes or substitutions that would be easily recognized by those skilled in the art within the technical scope of the present disclosure are intended to be covered by the present invention.

It should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes described in the context of a single embodiment or with reference to a single figure in order to streamline the invention and aid those skilled in the art in understanding the various aspects of the invention. The present invention should not, however, be construed as including features that are essential to the patent claims in the exemplary embodiments.

Those skilled in the art will appreciate that all or part of the flow of the methods of the embodiments described above may be accomplished by way of a computer program to instruct associated hardware, where the program may be stored on 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, etc.

It should be understood that modules, units, components, etc. included in the apparatus of one embodiment of the present invention may be adaptively changed to arrange them in an apparatus different from the embodiment. The different modules, units or components comprised by the apparatus of the embodiments may be combined into one module, unit or component or they may be divided into a plurality of sub-modules, sub-units or sub-components.

The modules, units, or components of embodiments of the invention may be implemented in hardware, in software running on one or more processors, or in a combination thereof. As will be appreciated by those skilled in the art,

embodiments according to the present invention may be implemented in practice using a microprocessor or Digital Signal Processor (DSP). The present invention can also be implemented as a computer program product or a computer readable medium for carrying out a part or all of the methods described herein.

Claims

1. The switching circuit with the residual voltage releasing function is characterized by comprising a filter capacitor positioned at the output end of the switching circuit and a discharge circuit used for forming a loop with the filter capacitor, wherein the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; the switching switch is grounded after being closed, so that the static current of the switching power supply and/or the residual voltage formed on the filter capacitor form a ground discharge loop;

the discharge resistor in the discharge circuit is formed by the internal impedance of the switching circuit.

2. The switching circuit according to claim 1, wherein the changeover switch is turned off in an operation state of the switching circuit for outputting a current to a load; and in a non-working state that the switching circuit stops outputting current to the load, the change-over switch is closed.

3. The switching circuit according to claim 2, wherein when the switching circuit stops outputting the current to the load, the changeover switch is immediately closed, and the discharge circuit is turned on and held; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.

4. The switching circuit according to claim 2, wherein after the switching circuit stops outputting the current to the load, when the voltage on the filter capacitor is released to the voltage threshold Vo, the change-over switch is immediately closed, and the discharging circuit is turned on and held; when the switching circuit outputs current to the load again, the change-over switch is immediately turned off; the voltage threshold Vo is smaller than the output voltage of the switching circuit during operation and is larger than the residual voltage of the filter capacitor.

5. The switching circuit according to claim 2, wherein after the switching circuit stops outputting the current to the load, the switching circuit is turned on to turn on the discharge circuit and hold after the voltage on the filter capacitor is released to the residual voltage; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.

6. The switching circuit according to any one of claims 1 to 5, further comprising a control circuit for controlling the switching switch to be opened or closed, wherein the control circuit comprises a voltage sampling module, a control module and a driving module;

7. The switching circuit according to claim 6, wherein the method of controlling the switching switch to be turned on or off is:

8. The switching circuit according to claim 6, wherein the voltage of the filter capacitor C1 corresponds to the condition that the switch S1 is turned on by closing: