Circuit for preventing overshoot during starting of input power supply

Abstract

The utility model relates to a circuit for preventing overshoot during starting of an input power supply, which comprises a power supply input circuit, a current limiting circuit, a driving circuit and a power supply output circuit, the power supply input circuit, the current limiting circuit and the power supply output circuit are sequentially connected, and the driving circuit is connected in parallel between the current limiting circuit and the power supply output circuit. The power output circuit comprises a power output end VOUT, the current limiting circuit comprises a current limiting resistor R1 and a relay K1 connected with the current limiting resistor R1 in parallel, a control end K1-B of the relay K1 is connected with the current limiting resistor R1 in parallel, a positive electrode of the current limiting resistor R1 is connected with a power input end VIN +, and a negative electrode of the current limiting resistor R1 is connected with the power output end VOUT. The RC delay circuit comprises a third divider resistor R3, a second divider resistor R2 and a variable capacitor C2, wherein the second divider resistor R2 and the variable capacitor C2 are connected in parallel. The driving end K1-A of the relay K1 is connected with the resistor R2 in parallel. The scheme is simple in structure, effectively suppresses the overshoot current when the input power supply starts, and is suitable for various electronic devices with input AC or DC power supplies.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supplies, and particularly relates to a circuit for preventing overshoot when an input power supply starts up. Background Technique

[0002] Since in electronic devices, the power supply is a key component for providing electrical energy, the stability and safety of its performance directly affect the normal operation of the device. During the startup process of the input power supply, due to the charging characteristics of capacitors and the energy storage characteristics of inductors, an input surge current is generated at the moment when the switching power supply is turned on. Since the initial voltage on the capacitor is zero, a very large current is formed during the instant charging of the capacitor. This surge current may damage the power supply and the circuit, and often generates a large overshoot current, which may not only damage the power supply itself, but also have an adverse impact on the load device connected thereto. Therefore, how to effectively suppress the overshoot current during power supply startup is a problem to be solved in the power supply technology field.

[0003] At present, there are already some circuit solutions for preventing power supply startup overshoot in the market, but most of them have problems such as complex structure, high cost, and great implementation difficulty, which are not conducive to popularization and application. Therefore, developing a circuit solution for preventing power supply startup overshoot with a simple structure and easy implementation has important practical significance and broad market prospects. Content of the Utility Model

[0004] In view of this, in view of the deficiencies of the existing technology, the utility model provides a circuit for preventing overshoot when an input power supply starts up, which has a simple structure and is easy to implement.

[0005] A circuit for preventing overshoot when the input power supply starts up includes a power input circuit, a current limiting circuit, a driving circuit, and a power output circuit. The power input circuit, the current limiting circuit, and the power output circuit are connected in sequence. The driving circuit is connected in parallel between the current limiting circuit and the power output circuit. The power input circuit includes a power input terminal VIN+ and a power input terminal VIN-. The power output circuit includes a power output terminal VOUT. The current limiting circuit includes a current limiting resistor R1 and a relay K1 connected in parallel with the current limiting resistor R1. The control terminal K1-B of the relay K1 is connected in parallel with the current limiting resistor R1, and the control terminal K1-B of the relay K1 is in an open state when the power supply is not connected to the power input circuit. The positive pole of the current limiting resistor R1 is connected to the power input terminal VIN+, and the negative pole is connected to the power output terminal VOUT. The driving circuit includes an RC delay circuit. The RC delay circuit includes a third voltage dividing resistor R3, a second voltage dividing resistor R2 and a variable capacitor C2 connected in parallel. One end of the parallel connection of the second voltage dividing resistor R2 and the variable capacitor C2 is connected to the power output terminal VOUT through the third voltage dividing resistor R3, and the other end is grounded. The driving terminal K1-A of the relay K1 is connected in parallel with the resistor R2, and the driving terminal K1-A of the relay K1 is used to control the open or closed state of the control terminal K1-B.

[0006] Further, a conversion circuit is further included. The conversion circuit is connected between the current limiting circuit and the driving circuit. The conversion circuit includes an AC / DC circuit and / or a DC / DC circuit. The positive pole of the input end of the conversion circuit is connected to the negative pole of the current limiting resistor R1, the negative pole is connected to the power input terminal VIN-, the positive pole of the output end of the conversion circuit is connected to the power output terminal VOUT, and the negative pole is grounded.

[0007] Further, the power output circuit further includes a polarized capacitor C1. The positive pole of the polarized capacitor C1 is connected to the positive pole of the output end of the conversion circuit, the negative pole of the polarized capacitor C1 is connected to the power output terminal VOUT, and is grounded.

[0008] Further, the driving circuit further includes a diode D1. The positive pole of the diode D1 is connected to the power output terminal VOUT, and the negative pole is connected to the third voltage dividing resistor R3.

[0009] Further, a common mode inductor LX1 is connected between the power input circuit and the current limiting circuit. The common mode inductor LX1 includes a coil LX1-B and a coil LX1-A. The coil LX1-B is connected in series between the power input terminal VIN+ and the positive pole of the current limiting resistor R1, and the coil LX1-A is connected in series between the power input terminal VIN- and the negative pole of the input end of the conversion circuit.

[0010] Further, a capacitor CX1 is connected in series between the positive pole of the coil LX1-B and the positive pole of the coil LX1-A, and a capacitor CX2 is connected in series between the negative pole of the coil LX1-B and the negative pole of the coil LX1-A.

[0011] The circuit for preventing overshoot when the above input power supply starts up limits the input current by connecting a relay in parallel with a current-limiting resistor when the power supply starts up. This reduces the current peak at the moment of startup, minimizes the impact of voltage on the power supply and the load, effectively suppresses the overshoot current when the input power supply starts up, reduces the failure rate of the power supply and load equipment, and improves the stability and safety of the power supply system. Since the current-limiting resistor is connected in series on the main circuit, it will cause power loss and result in low efficiency of the switching power supply. By setting a relay in parallel with the current-limiting resistor and keeping the relay in the open state when it is not powered, after the power supply operates stably, the drive circuit sends a high-level control signal to the relay to make it close. Due to the very small internal resistance of the relay, the current flows through the relay, thus reducing the power loss of the circuit. The control signal is delayed by an RC delay circuit to prevent the relay from conducting prematurely and the surge resistor from not functioning, which may damage other components. The delay time can also be controlled by changing the capacitance value in the RC delay circuit. This circuit is applicable to different topologies. Since the relay is controlled by a winding, the input and output are isolated, making it suitable for various circuits such as buck, boost, and flyback circuits. This solution has a simple structure and is easy to implement, and is applicable to electronic devices with various input AC or DC power supplies. Brief Description of the Drawings

[0012] Figure 1 It is a schematic diagram of a circuit for preventing overshoot when an input power supply starts up provided by an embodiment of the present invention. Detailed Embodiment

[0013] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0014] Please refer to Figure 1, showing a circuit for preventing overshoot during the startup of an input power supply according to an embodiment of the present invention. The circuit includes a power input circuit, a current limiting circuit, a driving circuit, and a power output circuit. The power input circuit, the current limiting circuit, and the power output circuit are connected in sequence. The driving circuit is connected in parallel between the current limiting circuit and the power output circuit. The power input circuit includes a power input terminal VIN+ and a power input terminal VIN-. The power output circuit includes a power output terminal VOUT. The current limiting circuit includes a current limiting resistor R1 and a relay K1 connected in parallel with the current limiting resistor R1. The control terminal K1-B of the relay K1 is connected in parallel with the current limiting resistor R1, and the control terminal K1-B of the relay K1 is in an open state when the power input circuit is not powered on. The positive electrode of the current limiting resistor R1 is connected to the power input terminal VIN+, and the negative electrode is connected to the power output terminal VOUT. The driving circuit includes an RC delay circuit for delaying the generation of a control signal. The RC delay circuit includes a third voltage dividing resistor R3, a second voltage dividing resistor R2 and a variable capacitor C2 connected in parallel. One end of the parallel connection of the second voltage dividing resistor R2 and the variable capacitor C2 is connected to the power output terminal VOUT through the third voltage dividing resistor R3, and the other end is grounded. The driving terminal K1-A of the relay K1 is connected in parallel with the resistor R2, and the driving terminal K1-A of the relay K1 is used to control the open or closed state of the control terminal K1-B.

[0015] Further, a conversion circuit is further included. The conversion circuit is connected between the current limiting circuit and the driving circuit. The conversion circuit includes an AC / DC circuit and / or a DC / DC circuit. The positive electrode of the input end of the conversion circuit is connected to the negative electrode of the current limiting resistor R1, and the negative electrode is connected to the power input terminal VIN-. The positive electrode of the output end of the conversion circuit is connected to the power output terminal VOUT, and the negative electrode is grounded.

[0016] Further, the power output circuit further includes a polarized capacitor C1. The positive electrode of the polarized capacitor C1 is connected to the positive electrode of the output end of the conversion circuit, and the negative electrode of the polarized capacitor C1 is connected to the power output terminal VOUT and grounded.

[0017] Further, the driving circuit further includes a diode D1. The positive electrode of the diode D1 is connected to the power output terminal VOUT, and the negative electrode is connected to the third voltage dividing resistor R3.

[0018] Furthermore, a common-mode inductor LX1 is connected between the power input circuit and the current-limiting circuit. The common-mode inductor LX1 includes a coil LX1-B and a coil LX1-A. The coil LX1-B is connected in series between the positive terminal of the power input VIN+ and the positive terminal of the current-limiting resistor R1, and the coil LX1-A is connected in series between the negative terminal of the power input VIN- and the negative terminal of the input of the conversion circuit. The common-mode inductor can also protect the circuit and equipment from external interferences such as lightning and electromagnetic pulses. The common-mode inductor LX1 can suppress electromagnetic interference, absorb or reflect most of its energy, prevent damage to the equipment caused by current fluctuations in the circuit, thereby protecting the safety of the circuit and equipment and improving the reliability of the power supply.

[0019] Furthermore, a capacitor CX1 is connected in series between the positive terminals of the coil LX1-B and the coil LX1-A, and a capacitor CX2 is connected in series between the negative terminals of the coil LX1-B and the coil LX1-A. The capacitors CX1 and CX2 can also be used to protect the circuit from transient voltage or current surges. When a transient overvoltage appears in the power supply, the capacitors can absorb the excess charge, thereby protecting other components in the circuit and further ensuring the stability of the output voltage.

[0020] The above circuit for preventing overshoot during the startup of the input power supply limits the magnitude of the input current due to the current-limiting resistor when the power supply starts up, reduces the current peak value at the moment of startup, decreases the impact of voltage on the power supply and the load, effectively suppresses the overshoot current during the startup of the input power supply, reduces the failure rate of the power supply and the load equipment, and improves the stability and safety of the power supply system. Since the current-limiting resistor is connected in series on the main path, it will cause losses and result in low efficiency of the switching power supply. By setting a relay in parallel with the current-limiting resistor and keeping the relay in the open state when it is not powered on, when the power supply operates stably, the drive circuit sends a high-level control signal to the relay to make the relay close. Since the internal resistance of the relay is very small, the current flows through the relay, thereby reducing the power loss of the circuit. By using the RC delay circuit, the control signal is delayed to be sent, avoiding the relay conducting in advance and the surge resistor not playing a role and causing damage to other devices. The delay time can also be controlled by changing the capacitance of the RC delay circuit. This circuit is applicable to different topologies. Since the relay is controlled by a winding, the input and output are isolated, and it is applicable to various circuits such as buck, boost, and flyback circuits. The structure of this solution is simple and easy to implement, and it is applicable to electronic devices with various input AC or DC power supplies.

[0021] It should be noted that the present utility model is not limited to the above embodiments. According to the creative spirit of the present utility model, those skilled in the art can also make other changes, and these changes made based on the creative spirit of the present utility model should be included within the scope of protection required by the present utility model.

Claims

1. A circuit for preventing overshoot when input power is started, characterized in that: The invention comprises a power input circuit, a current limiting circuit, a driving circuit and a power output circuit, wherein the power input circuit, the current limiting circuit and the power output circuit are connected in sequence, the driving circuit is connected in parallel between the current limiting circuit and the power output circuit, the power input circuit comprises a power input terminal VIN+ and a power input terminal VIN-, the power output circuit comprises a power output terminal VOUT, the current limiting circuit comprises a current limiting resistor R1 and a relay K1 connected in parallel with the current limiting resistor R1, the control terminal K1-B of the relay K1 is connected in parallel with the current limiting resistor R1, and the control terminal K1-B of the relay K1 is connected in parallel with the power input circuit. When the power is input, it is in the normally open state, the positive electrode of the current limiting resistor R1 is connected to the power input terminal VIN+, and the negative electrode is connected to the power output terminal VOUT, the driving circuit includes an RC delay circuit, and the RC delay circuit includes a third voltage-dividing resistor R3, a second voltage-dividing resistor R2 and a variable capacitor C2 connected in parallel, one end of the parallel connection of the second voltage-dividing resistor R2 and the variable capacitor C2 is connected to the power output terminal VOUT through the third voltage-dividing resistor R3, and the other end is grounded, the driving end K1-A of the relay K1 is connected in parallel with the resistor R2, and the driving end K1-A of the relay K1 is used to control the opening or closing state of the control end K1-B.

2. The circuit for preventing overshoot when input power is started as claimed in claim 1, characterized in that: It also includes a conversion circuit, which is connected between the current limiting circuit and the driving circuit, and the conversion circuit includes an AC / DC circuit and / or a DC / DC circuit; the positive electrode of the input end of the conversion circuit is connected to the negative electrode of the current limiting resistor R1, and the negative electrode is connected to the power input end VIN-; the positive electrode of the output end of the conversion circuit is connected to the power output end VOUT, and the negative electrode is grounded.

3. The circuit for preventing overshoot when input power is started as claimed in claim 1, characterized in that: The power output circuit further includes a polarity capacitor C1 , a positive electrode of the polarity capacitor C1 is connected to the power output terminal VOUT, and a negative electrode of the polarity capacitor C1 is grounded.

4. The circuit for preventing overshoot when input power is started as claimed in claim 1, characterized in that: The driving circuit further includes a diode D1 , wherein an anode of the diode D1 is connected to the power output terminal VOUT, and a cathode of the diode D1 is connected to the third voltage-dividing resistor R3 .

5. The circuit for preventing overshoot when input power is started as claimed in claim 2, characterized in that: A common-mode inductor LX1 is connected between the power input circuit and the current limiting circuit. The common-mode inductor LX1 includes a coil LX1-B and a coil LX1-A. The coil LX1-B is connected in series between the power input terminal VIN+ and the positive electrode of the current limiting resistor R1, and the coil LX1-A is connected in series between the power input terminal VIN- and the negative electrode of the input terminal of the conversion circuit.

6. The circuit for preventing overshoot when input power is started as claimed in claim 5, characterized in that: A capacitor CX1 is connected in series between the positive electrode of the coil LX1 -B and the positive electrode of the coil LX1 -A, and a capacitor CX2 is connected in series between the negative electrode of the coil LX1 -B and the negative electrode of the coil LX1 -A.

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