Low-loss high-efficiency power supply control and protection circuit and control method thereof

Abstract

The application discloses a low-loss high-efficiency power supply control and protection circuit, comprising a safety capacitor controllable discharge module, an output overvoltage protection module and a power-on soft start and current-limiting bypass module.The input end of the safety capacitor controllable discharge module is connected with an AC power supply input, and the output end is connected with the ground; the sampling end of the output overvoltage protection module is connected with a power supply output end, and the control end is connected with a main power drive loop; and the power-on soft start and current-limiting bypass module is connected in series in a power supply main power loop.The application realizes controllable access and cut-off of a resistor through a relay: the discharge resistor and the current-limiting resistor are cut off from the loop in normal working, so that the conduction heat loss is eliminated; the discharge resistor is automatically accessed to complete safety discharge when power failure occurs; the current-limiting resistor is accessed to suppress the impact current when power-on, and the output is bypassed after being established; and the main power loop is quickly turned off when the output is overvoltage.The scheme can significantly improve the efficiency, reduce the size and cost under the premise of meeting the safety protection.

Description

Technical Field

[0001] This application belongs to the field of power supply, specifically relating to a low-loss, high-efficiency power supply control and protection circuit that combines controllable discharge of safety capacitors, power-on soft-start current limiting, and output overvoltage protection. Background Technology

[0002] Conventional switching power supplies use a safety capacitor connected in parallel with a fixed discharge resistor and a fixed current-limiting resistor connected in series in the main circuit to achieve safety design. This has the following technical problems: the discharge resistor is connected in parallel across the safety capacitor for a long time, and there is continuous conduction heat loss during normal operation, which significantly reduces the overall efficiency of the power supply; the current-limiting resistor is continuously connected in series in the main power circuit, which generates additional losses during normal operation, and causes serious heat generation and low efficiency under high power applications. To meet the requirements of current limiting and discharge, large-size relays and capacitors are required, resulting in large product size and high cost; multiple protection functions are implemented separately, resulting in a large number of components, complex layout, high debugging difficulty, and low system reliability.

[0003] To address the aforementioned shortcomings, this application proposes a low-loss, high-efficiency power control and protection circuit. By using a relay to achieve controllable switching between the discharge resistor and the current-limiting resistor, it eliminates useless losses and improves efficiency while meeting safety regulations, protection requirements, and soft-start requirements. Summary of the Invention

[0004] This application discloses a low-loss, high-efficiency power supply control and protection circuit. A first relay K1 enables controllable switching out and connection of the discharge branch, a second relay K2 enables power-on connection and normal bypass of the current-limiting branch, and an output sampling module and a switch control module provide rapid overvoltage protection. The specific solution is as follows: A low-loss, high-efficiency power supply control and protection circuit, characterized in that it includes: The controllable discharge module is connected between the AC power input and ground. It is used to disconnect the discharge resistor when the power is on normally and connect the discharge resistor when the power is off to discharge the safety capacitor. The overvoltage protection module has its sampling terminal connected to the power output terminal and its control terminal connected to the main power drive circuit. It is used to shut down the main power circuit when the output voltage exceeds the threshold. The soft-start current limiting module is connected in series between the rectifier output terminal and the bus. It is used to suppress surge current by inserting a current limiting resistor in series during the power-on phase and to bypass the current limiting resistor after the output is established.

[0005] Preferably, the controllable discharge module includes a first relay, a first discharge resistor, and a first safety capacitor; the first end of the first safety capacitor is connected to the AC input live wire, and the second end is connected to the first end of the first discharge resistor; the second end of the first discharge resistor is connected to the normally closed contact end of the first relay; the common contact end of the first relay is grounded, one end of the coil is connected to the AC input detection terminal, and the other end of the coil is grounded; the first relay is a normally closed single-pole double-throw relay.

[0006] Preferably, the overvoltage protection module includes a first voltage divider resistor, a first reference voltage regulator, and a first switching transistor; one end of the first voltage divider resistor is connected to the high-voltage output terminal of the power supply, and the other end is connected to the reference electrode of the first reference voltage regulator; the anode of the first reference voltage regulator is grounded, and the cathode is connected to the control electrode of the first switching transistor; one end of the first switching transistor is connected to the main power transistor drive signal terminal, and the other end is connected to the bus terminal via the soft-start current limiting module.

[0007] Preferably, the first switching transistor is an NPN transistor or an NMOS transistor; the first reference voltage regulator is an adjustable precision reference voltage regulator; the resistance value of the first voltage divider resistor is configured such that when the output voltage is normal, the voltage divider sampling voltage is lower than the internal reference threshold of the first reference voltage regulator; when the output voltage abnormally rises and exceeds the protection threshold, the voltage divider sampling voltage is higher than the threshold.

[0008] Preferably, the soft-start current limiting module includes a first current limiting resistor and a second relay; one end of the first current limiting resistor is connected to the output terminal of the first switching transistor in the overvoltage protection module, and the other end is connected to the bus terminal; the two ends of the normally open contact of the second relay are connected in parallel with the two ends of the first current limiting resistor; one end of the coil of the second relay is connected to the power output terminal, and the other end of the coil is grounded; the second relay is a normally open single-pole relay.

[0009] Furthermore, this application also discloses a control method employing the above-described circuit topology, characterized by comprising: During power-on startup: the second relay disconnects, and the first current-limiting resistor is connected in series with the main circuit to suppress surge current; the first relay engages, and the first discharge resistor disconnects from the circuit. Normal operating phase: After output is established, the second relay is energized and the first current-limiting resistor is bypassed; the first relay remains energized and the first discharge resistor remains disconnected; the overvoltage protection module monitors the output voltage in real time. Output overvoltage stage: When the output voltage exceeds the threshold, the overvoltage protection module activates, the first reference voltage regulator is turned on, the first switching transistor is turned off, and the main power drive signal is cut off. Power-off discharge phase: AC input disappears, the first relay is released, the first discharge resistor is connected, and the first safety capacitor discharges rapidly through the first discharge resistor.

[0010] Preferably, during the power-on startup phase, when the output voltage is not established, the second relay coil has no driving voltage and the normally open contact remains open; during the normal operation phase, after the output voltage stabilizes, the second relay coil is energized and the normally open contact closes.

[0011] Preferably, during the output overvoltage stage, when the sampling voltage output by the first voltage divider resistor is higher than the internal reference threshold of the first reference voltage regulator, the first reference voltage regulator quickly turns on and pulls down the control electrode potential of the first switch transistor, and the first switch transistor immediately turns off.

[0012] Preferably, during the power-off discharge phase, the first relay coil is de-energized and released, and the normally closed contact returns to closure, forming a discharge path from the first safety capacitor to ground through the first discharge resistor.

[0013] During the power-on startup phase and normal operation phase, the coil of the first relay is energized and engaged when the AC input is normally powered, and the normally closed contact opens to completely disconnect the first discharge resistor; during the power-off discharge phase, the coil is de-energized and released.

[0014] During normal operation, the first relay K1 disconnects the discharge resistor from the circuit to eliminate conduction heat loss; when power is off, the first relay K1 releases, and the discharge resistor is connected to the circuit, allowing the safety capacitor to discharge quickly and meet safety requirements.

[0015] During the power-on phase, the second relay K2 is disconnected, and the current-limiting resistor is connected in series with the main circuit to suppress the surge current; after the output is established, the second relay K2 is energized, and the current-limiting resistor is bypassed to eliminate additional losses.

[0016] When the output voltage is overvoltage, the sampling circuit triggers the control switch to shut down the main power circuit, achieving rapid protection.

[0017] The beneficial effects of this application are as follows: 1. During normal operation, both the discharge resistor and the current-limiting resistor are disconnected, completely eliminating conduction heat loss and significantly improving power efficiency; 2. Automatic discharge upon power failure, current limiting upon power-on, and rapid shutdown under overvoltage provide triple safety protection, meeting safety standards; 3. The circuit structure is simple, the number of components is small, it is easy to debug, and it has low cost and small size; 4. The relay switching is smooth and shock-free, does not affect system reliability, and has strong versatility. Attached Figure Description

[0018] Figure 1 This is a circuit diagram of an embodiment of this application. Detailed Implementation

[0019] To make the present application clearer, the embodiments of the present application are described clearly and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application. Those skilled in the art can make other modifications, substitutions or changes to the present application without creative effort, and such modifications, substitutions or changes still fall within the protection scope of the present application.

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe the order or sequence of specific objects. It should be understood that such data can be used interchangeably where appropriate for describing embodiments of this application herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, systems, products, or apparatus.

[0022] like Figure 1 As shown, this application discloses a low-loss, high-efficiency power control and protection circuit, comprising: a controllable discharge module 100, an overvoltage protection module 200, and a soft-start current limiting module 300. The input terminal of the controllable discharge module 100 is connected to the AC power input, and the output terminal is connected to ground; the sampling terminal of the overvoltage protection module 200 is connected to the power output terminal, and the control terminal is connected to the main power drive circuit; the soft-start current limiting module 300 is connected in series between the rectifier output terminal and the bus VBUS.

[0023] The controllable discharge module 100 includes a first relay K1, a first discharge resistor R3, and a first safety capacitor C2. The first terminal of the first safety capacitor C2 is connected to the AC input live wire; the second terminal of the first safety capacitor C2 is connected to the first terminal of the first discharge resistor R3; the second terminal of the first discharge resistor R3 is connected to the normally closed contact terminal of the first relay K1; the common contact terminal of the first relay K1 is directly connected to ground; one end of the coil of the first relay K1 is connected to the AC input detection terminal, and the other end of the coil is connected to ground; the first relay K1 adopts a normally closed single-pole double-throw structure.

[0024] When the AC input is powered normally, the coil of the first relay K1 is energized and closed, the normally closed contact opens, the first discharge resistor R3 is completely disconnected from the circuit, no current flows through the circuit, and no conduction heat loss is generated; when the AC input suddenly loses power, the coil of the first relay K1 is de-energized and released, the normally closed contact returns to closed, the first discharge resistor R3 is connected to the circuit, and the first safety capacitor C2 forms a discharge path through the first discharge resistor R3, realizing fast and safe discharge and meeting the safety discharge requirements.

[0025] The overvoltage protection module 200 includes a first voltage divider resistor R7, a first reference voltage regulator U3, and a first switching transistor Q1.

[0026] In this circuit, one end of the first voltage divider resistor R7 is connected to the high-voltage output terminal of the power supply, and the other end of the first voltage divider resistor R7 is connected to the reference terminal of the first reference voltage regulator U3; the anode of the first reference voltage regulator U3 is directly grounded, and the cathode of the first reference voltage regulator U3 is connected to the control terminal of the first switching transistor Q1; one end of the first switching transistor Q1 is connected to the main power transistor drive signal terminal (i.e., Vin+), and the other end of the first switching transistor Q1 is connected to the bus VBUS terminal (corresponding to Vo+ in the figure) via the start-up current limiting module 300; the first switching transistor Q1 can be an NPN transistor or an NMOS transistor.

[0027] When the power supply output voltage is within the normal range, the sampling voltage output by the first voltage divider resistor R7 is lower than the internal reference threshold of the first reference voltage regulator U3. The first reference voltage regulator U3 remains off, the first switch Q1 remains on, the main power drive circuit works normally, and the power supply maintains a stable output. When the power supply output voltage rises abnormally and exceeds the protection threshold, the sampling voltage output by the first voltage divider resistor R7 is higher than the internal reference threshold of the first reference voltage regulator U3. The first reference voltage regulator U3 quickly turns on, pulling the control electrode potential of the first switch Q1 down to ground. The first switch Q1 immediately turns off, the main power drive signal is cut off, the main power circuit stops working, and output overvoltage protection is achieved.

[0028] The soft-start current limiting module 300 includes a first current limiting resistor R5 and a second relay K2. One end of the first current limiting resistor R5 is connected to the first switching transistor Q1, and the other end of the first current limiting resistor R5 is connected to the bus VBUS terminal; the two ends of the normally open contact of the second relay K2 are connected in parallel with the two ends of the first current limiting resistor R5; one end of the coil of the second relay K2 is connected to the power output terminal, and the other end of the coil is connected to ground; the second relay K2 adopts a normally open single-pole structure.

[0029] During the initial power-on phase, before the output voltage is established, the coil of the second relay K2 has no driving voltage, and its normally open contact remains open. The first current-limiting resistor R5 is connected in series with the main power circuit, effectively suppressing the surge current at the moment of power-on and protecting key components such as the rectifier bridge, bus capacitor, and power transistor. Once the output voltage is established and reaches a stable value, the coil of the second relay K2 is energized and the normally open contact closes. The first current-limiting resistor R5 is completely bypassed by the relay contact, and the main circuit current flows directly through the relay contact without passing through the first current-limiting resistor R5, thus completely eliminating the conduction heat loss caused by the current-limiting resistor and improving the overall efficiency.

[0030] The overall workflow of the low-loss, high-efficiency power control and protection circuit disclosed in this application is as follows: During power-on startup: before output is established, the second relay K2 is disconnected and the first current-limiting resistor R5 is engaged to suppress surge current; when AC input is normal, the first relay K1 is engaged and the first discharge resistor R3 is disconnected, resulting in no discharge loss; the output voltage is gradually established.

[0031] During normal operation: the output is stable, the second relay K2 is energized, and the first current-limiting resistor R5 is bypassed; the first relay K1 remains energized, and the first discharge resistor R3 remains disconnected; neither resistor generates any loss, and the overvoltage protection module monitors the output status in real time.

[0032] Output overvoltage stage: When the output voltage exceeds the threshold, the overvoltage protection module is activated, the first reference voltage regulator U3 is turned on, the first switching transistor Q1 is turned off, and the main power circuit stops outputting.

[0033] During the power-off discharge phase: AC input disappears, the first relay K1 is released, the first discharge resistor R3 is connected, and the first safety capacitor C2 discharges rapidly, meeting safety requirements.

[0034] This application minimizes losses through controllable relay switching, achieving high efficiency, low cost, small size, and high reliability while ensuring safety, protection, and soft-start functions. It is suitable for various AC-DC and DC-DC switching power supplies.

[0035] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A low-loss, high-efficiency power supply control and protection circuit, characterized in that, include: The controllable discharge module is connected between the AC power input and ground. It is used to disconnect the discharge resistor when the power is on normally and connect the discharge resistor when the power is off to discharge the safety capacitor. The overvoltage protection module has its sampling terminal connected to the power output terminal and its control terminal connected to the main power drive circuit. It is used to shut down the main power circuit when the output voltage exceeds the threshold. The soft-start current limiting module is connected in series between the rectifier output terminal and the bus. It is used to suppress surge current by inserting a current limiting resistor in series during the power-on phase and to bypass the current limiting resistor after the output is established.

2. The circuit according to claim 1, characterized in that, The controllable discharge module includes a first relay, a first discharge resistor, and a first safety capacitor; the first end of the first safety capacitor is connected to the AC input live wire, and the second end is connected to the first end of the first discharge resistor; the second end of the first discharge resistor is connected to the normally closed contact of the first relay; the common contact of the first relay is grounded, one end of the coil is connected to the AC input detection terminal, and the other end of the coil is grounded; the first relay is a normally closed single-pole double-throw relay.

3. The circuit according to claim 2, characterized in that, The overvoltage protection module includes a first voltage divider resistor, a first reference voltage regulator, and a first switching transistor; one end of the first voltage divider resistor is connected to the high-voltage output terminal of the power supply, and the other end is connected to the reference electrode of the first reference voltage regulator; the anode of the first reference voltage regulator is grounded, and the cathode is connected to the control electrode of the first switching transistor; one end of the first switching transistor is connected to the main power transistor drive signal terminal, and the other end is connected to the bus terminal via the soft-start current limiting module.

4. The circuit according to claim 3, characterized in that, The first switching transistor is an NPN transistor or an NMOS transistor; the first reference voltage regulator is an adjustable precision reference voltage regulator; the resistance value of the first voltage divider resistor is configured such that when the output voltage is normal, the voltage divider sampling voltage is lower than the internal reference threshold of the first reference voltage regulator; when the output voltage abnormally rises and exceeds the protection threshold, the voltage divider sampling voltage is higher than the threshold.

5. The circuit according to claim 1, characterized in that, The soft-start current limiting module includes a first current limiting resistor and a second relay; one end of the first current limiting resistor is connected to the output terminal of the first switching transistor in the overvoltage protection module, and the other end is connected to the bus terminal; the two ends of the normally open contact of the second relay are respectively connected in parallel with the two ends of the first current limiting resistor. One end of the coil of the second relay is connected to the power output terminal, and the other end of the coil is grounded; the second relay is a normally open single-pole relay.

6. A control method employing the circuit described in any one of claims 1 to 5, characterized in that, include: During the power-on startup phase: the second relay is disconnected, and the first current-limiting resistor is connected in series with the main circuit to suppress inrush current; The first relay is activated, and the first discharge resistor disconnects the circuit. Normal operating phase: After output is established, the second relay is energized and the first current-limiting resistor is bypassed; the first relay remains energized and the first discharge resistor remains disconnected; the overvoltage protection module monitors the output voltage in real time. Output overvoltage stage: When the output voltage exceeds the threshold, the overvoltage protection module activates, the first reference voltage regulator is turned on, the first switching transistor is turned off, and the main power drive signal is cut off. Power-off discharge phase: AC input disappears, the first relay is released, the first discharge resistor is connected, and the first safety capacitor discharges rapidly through the first discharge resistor.

7. The method according to claim 6, characterized in that, During the power-on startup phase, the second relay coil has no driving voltage before the output voltage is established, and the normally open contact remains open. During the normal operation phase, the second relay coil is energized and closed after the output voltage stabilizes, and the normally open contact closes.

8. The method according to claim 6, characterized in that, During the output overvoltage phase, when the sampling voltage output by the first voltage divider resistor is higher than the internal reference threshold of the first reference voltage regulator, the first reference voltage regulator quickly turns on and pulls down the control electrode potential of the first switch transistor, and the first switch transistor immediately turns off.

9. The method according to claim 6, characterized in that, During the power-off discharge phase, the first relay coil is de-energized and released, and the normally closed contact returns to closure, forming a discharge path from the first safety capacitor to ground through the first discharge resistor.

10. The method according to claim 6, characterized in that, During the power-on startup phase and normal operation phase, when the AC input is normally powered, the coil of the first relay is energized and the normally closed contact is opened, causing the first discharge resistor to be completely disconnected. During the power-off discharge phase, the coil loses power and releases.

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