CN113572348A - Switch circuit with residual voltage releasing function - Google Patents
Switch circuit with residual voltage releasing function Download PDFInfo
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- CN113572348A CN113572348A CN202110847289.0A CN202110847289A CN113572348A CN 113572348 A CN113572348 A CN 113572348A CN 202110847289 A CN202110847289 A CN 202110847289A CN 113572348 A CN113572348 A CN 113572348A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention relates to a switch circuit with a function of releasing residual voltage, which comprises a filter capacitor and a discharge circuit, wherein the filter capacitor is positioned at the output end of the switch circuit, the discharge circuit is used for forming a loop with the filter capacitor, and the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; and after the change-over switch is closed, the change-over switch is grounded, 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. When the switch circuit supplies power to the load, the change-over switch is switched off, so that the internal impedance or the residual voltage discharge resistor does not participate in energy consumption, and the change-over switch is switched on only when the residual voltage needs to be released, so that the static current is consumed.
Description
Technical Field
The present invention relates to a switching circuit having a function of discharging a residual voltage.
Background
The switching circuit is a high-frequency electric energy conversion device, and mainly utilizes power electronic switching devices, such as transistors, MOS (metal oxide semiconductor) tubes, controllable thyristors and the like, and the electronic switching devices are periodically turned on and off through a control circuit, so that the power electronic switching devices perform pulse modulation on input voltage, and the functions of voltage conversion, output voltage regulation and automatic voltage stabilization are realized. After the switch circuit stops supplying power to the load, voltage residual voltage is formed on a 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 a quiescent current is an internal current of the switching power supply under the condition of no output, and is very small and generally varies from several mA to several tens of mA. However, as long as the input end of the switching power supply is supplied with power, the quiescent current exists all the time. After the switching power supply stops supplying power to the load, the filter capacitor C1 at the output end discharges slowly through the internal impedance of the power supply. However, due to the existence of the internal static current, the voltage of the filter capacitor C1 cannot be released to 0V, and finally a stable voltage, generally referred to as a residual voltage Ur, is formed across the filter capacitor C1.
Currently, the residual voltage Ur is eliminated by adding a "dummy load" at the power supply output to consume the quiescent current. As shown in fig. 1, a resistor R1 with a proper amount of resistance and suitable encapsulation is usually added between the positive and negative electrodes of the power output terminal to form a loop with the filter capacitor of the power output terminal after the switching power supply stops supplying power to the load, so as to release the 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, the power consumption of the resistor needs to be greatly reduced, so that the resistor is easily packaged in a larger manner and occupies a larger space, and the wiring layout difficulty of the switch power supply PCB is increased;
(2) the dummy load resistor is used as an extra fixed load, and a loss is additionally introduced, so that the extra loss can reduce the output conversion efficiency of the switching power supply;
(3) the dummy load resistor is used as a special device, and the manufacturing cost of the switching power supply is increased to a certain extent.
Disclosure of Invention
The invention provides a switch circuit with a residual voltage releasing function.
The invention provides a switch circuit with a function of releasing residual voltage, which comprises a filter capacitor and a discharge circuit, wherein the filter capacitor is positioned at the output end of the switch circuit, the discharge circuit is used for forming a loop with the filter capacitor, and the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; and after the change-over switch is closed, the change-over switch is grounded, 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.
In one embodiment, the discharge resistor in the discharge circuit is a resistor having a resistance value, and the resistance value is used for determining the residual voltage discharge time.
In one embodiment, the discharge resistor in the discharge circuit is formed by an internal impedance of the switching circuit.
In one embodiment, the switch is turned off in an operating state in which the switching circuit outputs a current to the load; and under the non-working state that the switch circuit stops outputting current to the load, the change-over switch is closed.
As an embodiment, when the switch circuit stops outputting current to the load, the switch is immediately 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.
As an embodiment, 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 switch is immediately closed, and the discharging circuit is turned on and maintained; when the switching circuit outputs current to the load again, the change-over switch is immediately switched off; the voltage threshold Vo is smaller than the output voltage of the switching circuit during working and larger than the residual voltage of the filter capacitor.
As an embodiment, after the switch circuit stops outputting the 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 turned on and maintained; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.
The second aspect of the invention provides a control circuit for controlling the on/off of a switch, which comprises a control circuit for controlling the on/off of the switch, wherein the control circuit comprises a voltage sampling module, a control module and a driving module;
the voltage sampling module is used for collecting voltage data of a 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 meets the action condition of switching on and off the switch S1 or not 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 switch to be switched on according to the control signal.
As an embodiment, the method for controlling the on or off of the switch includes:
step S1: the control module judges whether the switch circuit stops outputting current to the load or not; if the switching circuit stops outputting the current to the load, the flow proceeds to step S2; if the switch circuit is outputting current to the load, continuously detecting whether the switch circuit stops outputting current to the load;
step S2: the control module judges whether the voltage at the two ends of the filter capacitor C1 meets the action condition of switching on and off the switch S1; when the voltage at the two ends of the filter capacitor C1 enters the action condition which accords 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 switch S1 according to the control signal;
step S3: under the closed state of the change-over switch S1, the control module continuously judges whether the switch circuit starts to output current to the load, and if the switch circuit starts to output current to the load, the control module sends a control signal to the driving module; the drive circuit turns off the changeover switch according to the control signal.
In one embodiment, the voltage of the filter capacitor C1 meets the operating condition that the switch S1 is turned on and off as follows:
under the control mode that the switch power supply closes the change-over switch S1 immediately after stopping outputting current to the output load R2, when the voltage of the filter capacitor C1 is smaller than the output voltage Vout of the switch power supply, the voltage of the filter capacitor C1 meets the action condition of closing and conducting the change-over switch S1;
under the control mode that the voltage on the filter capacitor C1 immediately closes the switch S1 when the voltage is released to the voltage amplitude Vo, when the voltage of the filter capacitor C1 drops to the voltage amplitude Vo, the voltage of the filter capacitor C1 meets 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 the voltage 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 meets the action condition that the switch S1 is closed and conducted.
Compared with the prior art, the invention has the remarkable advantages and beneficial effects that:
(1) the invention provides a switch circuit with a residual voltage releasing function, wherein a freely controllable change-over switch is arranged between a positive electrode and a negative electrode of an output end of a switch power supply, when the switch power supply supplies power to a load, the change-over switch is switched off, so that internal impedance or a residual voltage discharging resistor does not participate in energy consumption, and the change-over switch is switched on only when the residual voltage needs to be released to consume quiescent current. Thereby solving the problem of extra loss increase caused by using the dummy load.
(2) The resistor for discharging the residual voltage can be realized by the impedance of the existing electrical components in the switch circuit, and the additional electrical components are not needed in the limited space of the switch power supply, so that the problems of occupying the space of a PCB (printed circuit board) and increasing the cost are avoided. Certainly, the residual voltage discharge resistor can also be realized by using an additional electrical element, and at the moment, the reduced-rate use is not needed to be considered due to the working scene of the residual voltage discharge resistor, and only a small space is needed, so that the use of the space of the PCB is reduced, and the cost of the device is reduced.
(3) On the basis that the dummy load releases the residual voltage, the invention solves the problems of fixed loss caused by dummy load discharge and reduced efficiency of the switching power supply converter, improves the problem of limited circuit space arrangement of the PCB board of the switching power supply and reduces the hardware cost of the switching power supply.
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 hereof 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, wherein like reference numerals are used to designate like parts throughout.
Fig. 1 is a circuit diagram illustrating a prior art switching power supply using a dummy load to discharge a residual voltage.
Fig. 2 is a schematic circuit diagram of an operating state according to embodiment 1 of the present invention.
Fig. 3 is a circuit diagram illustrating another operating state according to embodiment 1 of the present invention.
Fig. 4 is a schematic circuit diagram of an operating state according to embodiment 2 of the present invention.
Fig. 5 is a circuit diagram illustrating another operating state according to embodiment 2 of the present invention.
FIG. 6 is a logic control diagram of the switch of the present invention.
FIG. 7 is a schematic diagram of the detection and control circuitry of the present invention.
FIG. 8 is a diagram of a control circuit according to an embodiment of the present invention.
Detailed Description
It is easily understood that various embodiments of the present invention can be conceived by those skilled in the art according to the technical solution of the present invention without changing the essential spirit of the present invention. Therefore, the following detailed description and the accompanying drawings are merely illustrative of the technical aspects of the present invention, and should not be construed as all of the present invention or as limitations or limitations on the technical aspects of the present invention. Rather, these embodiments are provided so that this disclosure will be thorough and complete. The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the innovative concepts of the 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, and a real load R2 supplied by the output. In fig. 2 and 3, the state of the switch symbol S2 is used to indicate whether the switching power supply outputs current to its output load R2, and does not represent that there is actually a switch in the physical sense in the circuit, and S2 in the sense of a physical device may or may not exist.
The switching circuit may be of an isolated type or a non-isolated type, and examples thereof include a rectifier, a transformer, a DC-DC converter, a buck circuit, and a boost circuit.
The operation of the switch circuit is controlled by the indication signal. Specifically, for example, a switching element such as a MOS transistor or a transistor is connected in series inside the converter, and an instruction signal is input to a control terminal of the switching element to control on/off of the switching element, whereby the operating state of the converter can be controlled.
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 forms the residual voltage Ur. 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 poles of the output terminal of the switching power supply, and 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, the switching power supply carries the output load R2 to output current normally, the voltage across the filter capacitor C1 at the output terminal is the output voltage Vout of the off power supply. At this time, the changeover switch S1 in the discharge circuit is turned off, the discharge circuit is not turned on, and the discharge resistor R1 as a discharge element is not connected to the operating circuit. When the switching power supply stops supplying power to the output load R2, as shown in fig. 3, the switch symbol S2 is turned off, the switching power supply does not output current to the load R2, and the filter capacitor C1 at the output end discharges slowly through the internal impedance R3 of the power supply. However, due to the existence of the internal static current, the voltage of the filter capacitor C1 cannot be released to 0V, and finally a stable voltage, i.e., a residual voltage Ur, is formed across the filter capacitor C1. At this time, as shown in fig. 3, the switch S1 is closed, the switch S1 and the discharge resistor R1 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 static current and the residual voltage form a ground discharge loop, and the residual voltage that cannot be completely released at both ends of the output filter capacitor C1 is finally released to 0V. In short, when the switching power supply does not supply power to the outside, the discharge circuit makes the quiescent current and the residual voltage constitute a discharge loop to the ground by switching the switch S1.
Example 2
With reference to fig. 4 and 5, embodiment 2 differs from embodiment 1 in that the composition of the discharge circuit provided between the positive and negative poles of the output terminal of the switching power supply is different. In embodiment 2, instead of forming the discharge circuit by adding the extra discharge resistor R1 as in embodiment 1, the discharge circuit is formed by the internal impedance R3 and the switch S1 of the switching power supply, that is, the discharge circuit is formed by connecting the internal impedance R3 and the switch S1 in series, when the switch S1 is closed, the switch S1 and the internal impedance R3 form a loop across the output filter capacitor C1, and the discharge circuit is grounded through the switch S1, so that the static current and the residual voltage Ur form a ground discharge loop.
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 static current of the switching power supply slowly charges the filter capacitor C1, and finally forms the residual voltage Ur. 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 carries the output load R2 to normally output current, the voltage across the output end filter capacitor C1 is the output voltage Vout of the off-power supply. At this time, the changeover switch S1 is placed in the open 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 to the outside, and at this time, the filter capacitor C1 at the output end slowly discharges through the internal resistance R3 of the power supply, but due to the existence of the internal static 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 output-end filter capacitor C1, the discharge circuit is grounded through the switch S1, the voltage which cannot be discharged originally on the filter capacitor C1 is grounded through the switch S1, so that the static current and the residual voltage Ur form a ground discharge loop, and the residual voltage Ur on the filter capacitor C1 is finally discharged to 0V.
It should be further noted that the residual voltage discharge time of example 1 is different from that of example 2 due to the different discharge loop compositions of the residual voltage in example 1 and example 2. Therefore, the embodiments 1 and 2 have different application scenarios. In view of relative comparison, in embodiment 1, since the discharge resistor R1 is a separately provided resistor, the resistance value thereof can be set as desired. 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 × C1, where C1 is the size of the filter capacitor at the output. Therefore, embodiment 1 is suitable for an application scenario where a residual voltage discharge time is required.
In embodiment 2, the discharge resistor is formed by the internal impedance R3, but the internal impedance R3 is not a fixed resistance value, and its impedance value is a dynamically changing value, and generally varies from several thousand ohms to several hundred thousand ohms depending on the topology form of the switching power supply, the output filter parameters of the power supply, the parameters of the components used in the power supply, and the like, so that the time for the residual voltage Ur to be finally released to 0v cannot be determined. Therefore, example 2 is suitable for an application scenario in which there is no requirement for the residual voltage discharge time.
In addition, in embodiment 1, the discharge resistor R1 is a separately provided resistor, so if the discharge circuit fails, and the residual voltage Ur cannot be released as required, the cause of the failure can be found out very easily, and circuit maintenance is facilitated. In embodiment 2, since the discharge resistor 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 failed, so that the discharge circuit cannot operate normally. Of course, the advantage of embodiment 2 over embodiment 1 is that the discharge resistor R1 is not separately provided, and the discharge resistor is formed by the impedance of other internal components, so that additional components are not required, and the packaging and miniaturization of the switching power supply are facilitated.
In the drawings corresponding to embodiments 1 and 2, the switching symbol S2 is used to indicate whether the switching power supply supplies power or not to 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-contained circuit or a digital command to switch the output operation state of the power supply, wherein the operation state comprises that a current is output for a load R2 and a current is not output for a load R2.
Example 3
As shown in fig. 2 and 3, in embodiment 1 and embodiment 2, the same discharge circuit is used, that is, the static current of the switching power supply forms a ground discharge circuit, and the residual voltage Ur of the filter capacitor forms a ground discharge circuit. Namely, a discharge loop is used, and a static current to ground discharge loop and a residual voltage Ur to ground discharge loop are simultaneously realized. Example 3 as an alternative implementation, two discharge loops shown in example 1 and example 2 are provided in the switch circuit, and a quiescent current to ground discharge loop and a residual voltage Ur to ground discharge loop are respectively realized.
For example, the first discharge loop comprises a discharge resistor and a change-over switch which are connected in series, and the change-over switch in the first discharge loop is grounded after being closed, so that the static current of the switching power supply forms a discharge loop to the ground. The second discharging loop also comprises a discharging resistor and a change-over switch which are connected in series, and the change-over switch in the second discharging loop is grounded after being closed, so that the residual voltage Ur formed on the filter capacitor forms a ground discharging loop.
In the present invention, the closing timing of the changeover switch S1 differs for different cases, and the corresponding changeover switch S1 control method:
the first method is as follows: after the switching power supply stops outputting current to the output load R2, namely the state switch S2 is switched off, the change-over switch S1 is immediately closed, and the discharging circuit is conducted and kept; the switch S1 is opened immediately after the switching power supply outputs current to the load R2 again, i.e., the state switch S2 is closed again.
The second method comprises the following steps: 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 immediately closed, and when the voltage across the filter capacitor C1 is released to a fixed voltage magnitude Vo, the switch S1 is immediately closed and held until the switching power supply outputs current to the load R2 again, that is, after the state switch S2 is again closed, the switch S1 is immediately turned off. The voltage magnitude Vo here is smaller than the power supply output voltage Vout but larger than the steady-state residual voltage Ur.
The third method comprises the following steps: after the switching power supply stops outputting current to the load R2, that is, after the state switch S2 is turned off, the voltage across 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 set to 0v after a long period of discharge, and finally a stable level, that is, a 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 held until the switching power supply again outputs current to the load R2, i.e., after the state switch S2 is closed again, the switch S1 is opened.
The three control modes have different advantages and disadvantages.
When the state of the switch S1 is controlled according to the first mode, the advantage is that the output voltage of the switching power supply in the stable state is treated as the residual voltage directly, the process of slow discharging of the filter capacitor C1 through the internal impedance of the power supply is saved, and the ground discharging loop is formed directly by the switch S1 after the switching power supply stops outputting the current to the output load R2. This has the disadvantage that the components inside the power supply (forming the internal impedance R3) or the discharge resistor R1 need to withstand a large discharge current. The grounding is needed to be carried out within a short time, the discharge current is large, the impact current is large, and some devices have requirements on the maximum value of the impact current. If the components are not designed to be strong enough, such as a series of devices forming internal impedance, or the discharge resistor R1 is not designed to be strong enough to withstand large inrush currents, the components of the power supply or the discharge resistor R1 may be damaged. Therefore, when the state of the changeover switch S1 is controlled in the first mode, high requirements are placed on the components or the discharge resistance of the switching power supply itself.
When the state of the switch S1 is controlled according to the second mode, the switch power output voltage is set with the threshold value Vo, which is a value between the output voltage Vout and the residual voltage Ur, and when the voltage at the output end of the switch power (i.e. the voltage of the filter capacitor C1) is lowered to the threshold value Vo, the switch S1 is closed again, so that the discharge current that the components (forming the internal impedance R3) or the discharge resistor R1 in the power supply need to bear 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 compared to the first mode.
Controlling the state of the switch S1 in this manner has the advantage of a lower discharge current and lower component robustness requirements. The disadvantage is that a certain time is required for detecting the stable voltage, and the total discharge time is longer than that of the second method.
The above three control modes of switching the switch S1 on and off for different situations need specific detection and control circuits to implement the control modes. With reference to fig. 7, in the present invention, a detection and control circuit for implementing the control manner of the aforementioned switch S1 includes a voltage sampling module, a control module and a driving module.
The voltage sampling module is configured to collect a voltage signal at two ends of the filter capacitor C1, and may specifically be implemented by using a voltage division sampling manner 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 acquired by the voltage sampling module, and sends a control instruction for closing or opening the 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 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 detection and control circuit, when the control module detects that the voltage state of the filter capacitor C1 meets the condition of the switch S1 for closing and conducting, the control module sends out a logic control high level or low level, the level changes a logic signal into a 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 path of the filter capacitor C1 to the ground, so that the residual voltage Ur is eliminated. When the control module detects that the switching power supply is to supply power to the output load, the switch S1 is also controlled by the driving circuit to be switched off, and the discharging path is closed, so that the switching power supply normally outputs current to the load.
The foregoing describes three control modes of the switch S1, and the on/off operation condition of the switch S1 has three different modes for the three different control modes.
When the state of the switch S1 is controlled according to the first mode, the switch S1 is closed immediately after the switching power supply stops outputting current to the output load R2, in this mode, when the control module detects that the voltage of the filter capacitor C1 is less than the output voltage Vout of the switching power supply, that is, the voltage state of the filter capacitor C1 is determined to meet the condition of the switch S1 closed conducting action, the control module sends a logic control level to the driving module.
When the state of the switch S1 is controlled according to the second mode, the switch S1 is closed immediately when the voltage across the filter capacitor C1 is released to a fixed voltage magnitude Vo, and in this mode, when the control module detects that the voltage across the filter capacitor C1 drops to the voltage magnitude Vo, that is, the voltage state of the filter capacitor C1 is determined to meet the condition of the switch S1 being closed and conducting, the control module sends a logic control level to the driving module.
When the state of the switch S1 is controlled in a manner, the switch S1 is closed immediately when the voltage across the filter capacitor C1 is released to the residual voltage Ur, in this manner, when the control module detects that the voltage across the filter capacitor C1 drops to the residual voltage Ur, that is, the voltage state of the filter capacitor C1 is determined to meet the condition of the switch S1 being closed and conducting, the control module sends a logic control level to the driving module.
In practical applications, the switching power supply is to supply power to the output load, and a user using the switching power supply controls a control pin on the switching power supply through a self-contained circuit or a digital command to switch the output working state of the power supply, wherein the working state comprises the current output for the load R2 and the current output 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 may be easily made by those skilled in the art within the technical scope of the present disclosure are intended to be included within the scope of the present disclosure.
It should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes described in a single embodiment or with reference to a single figure, for the purpose of streamlining the disclosure and aiding in the understanding of various aspects of the invention by those skilled in the art. However, the present invention should not be construed such that the features included in the exemplary embodiments are all the essential technical features of the patent claims.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
It should be understood that the modules, units, components, and the like included in the device of one embodiment of the present invention may be adaptively changed to be provided in a device different from that of the embodiment. The different modules, units or components comprised by the apparatus of an embodiment 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 in the embodiments of the present invention may be implemented in hardware, or may be implemented in software running on one or more processors, or a combination thereof. As will be appreciated by those skilled in the art,
embodiments in accordance with the present invention may be implemented in practice using a microprocessor or Digital Signal Processor (DSP). The present invention may also be embodied as a computer program product or computer-readable medium for performing a portion or all of the methods described herein.
Claims (10)
1. A switch circuit with a function of releasing residual voltage is characterized by comprising a filter capacitor and a discharge circuit, wherein the filter capacitor is positioned at the output end of the switch circuit, the discharge circuit is used for forming a loop with the filter capacitor, and the discharge circuit is formed by connecting a discharge resistor and a change-over switch in series; and after the change-over switch is closed, the change-over switch is grounded, 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.
2. The switching circuit according to claim 1, wherein the discharge resistor in the discharge circuit is a resistor having a resistance value for determining the residual voltage discharge time.
3. The switching circuit of claim 1, wherein the discharge resistance in the discharge circuit is formed by an internal impedance of the switching circuit.
4. A switching circuit according to any one of claims 1 to 3, wherein in an operating state in which the switching circuit outputs current to the load, the change-over switch is turned off; and under the non-working state that the switch circuit stops outputting current to the load, the change-over switch is closed.
5. The switching circuit according to claim 4, 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.
6. The switch circuit of claim 4, 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 immediately closed, and the discharging circuit is turned on and maintained; when the switching circuit outputs current to the load again, the change-over switch is immediately switched off; the voltage threshold Vo is smaller than the output voltage of the switching circuit during working and larger than the residual voltage of the filter capacitor.
7. The switching circuit according to claim 4, wherein after the switching circuit stops outputting the current to the load and the voltage on the filter capacitor is released to the residual voltage, the switch is closed to turn on and hold the discharging circuit; when the switching circuit outputs current to the load again, the changeover switch is immediately turned off.
8. The switching circuit according to any of claims 1-7, further comprising a control circuit for controlling the switch to open or close, the control circuit comprising a voltage sampling module, a control module, and a driving module;
the voltage sampling module is used for collecting voltage data of a 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 meets the action condition of switching on and off the switch S1 or not 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 switch to be switched on according to the control signal.
9. The switching circuit according to claim 8, wherein the method of controlling the on or off of the change-over switch is:
step S1: the control module judges whether the switch circuit stops outputting current to the load or not; if the switching circuit stops outputting the current to the load, the flow proceeds to step S2; if the switch circuit is outputting current to the load, continuously detecting whether the switch circuit stops outputting current to the load;
step S2: the control module judges whether the voltage at the two ends of the filter capacitor C1 meets the action condition of switching on and off the switch S1; when the voltage at the two ends of the filter capacitor C1 enters the action condition which accords 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 switch S1 according to the control signal;
step S3: under the closed state of the change-over switch S1, the control module continuously judges whether the switch circuit starts to output current to the load, and if the switch circuit starts to output current to the load, the control module sends a control signal to the driving module; the drive circuit turns off the changeover switch according to the control signal.
10. The switch circuit as claimed in claim 8, wherein the voltage of the filter capacitor C1 meets the action condition of the switch S1 being turned on:
under the control mode that the switch power supply closes the change-over switch S1 immediately after stopping outputting current to the output load R2, when the voltage of the filter capacitor C1 is smaller than the output voltage Vout of the switch power supply, the voltage of the filter capacitor C1 meets the action condition of closing and conducting the change-over switch S1;
under the control mode that the voltage on the filter capacitor C1 immediately closes the switch S1 when the voltage is released to the voltage amplitude Vo, when the voltage of the filter capacitor C1 drops to the voltage amplitude Vo, the voltage of the filter capacitor C1 meets 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 the voltage 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 meets the action condition that the switch S1 is closed and conducted.
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