Power-off protection circuit of multi-input power supply

Abstract

The utility model discloses a power-down protection circuit of a multi-input power supply. The power-down protection circuit comprises a plurality of input power supply branches and a power-down protection circuit, the power-down protection circuit comprises a first switch tube and a second switch tube. A first output end of the first switch tube is connected with a first power supply through a resistor and is connected with a control end of the second switch tube, a second output end of the first switch tube is grounded, and a control end of the first switch tube is an input end of the power-down protection circuit and is grounded through a voltage stabilizing element and a resistor which are connected in parallel; the first output end of the second switching tube is the output end of the power-down protection circuit, and the second switching tube is connected with a second power supply through a resistor and outputs a power-down signal; the second output end is grounded; each input power supply is connected to the input end of the power-down protection circuit through a first diode and a resistor; the power supply module is connected to the input end of the power supply module through a second diode and supplies power to the power supply module; the first power supply and the second power supply are directly or indirectly generated by the power module.

Description

Technical Field

[0001] The utility model relates to the technical field of energy storage, in particular to a power-off protection circuit for multiple input power supplies. Background Art

[0002] Multi-power input protection circuits are commonly used in systems requiring multiple power supplies, such as communications equipment and industrial control devices. In these scenarios, multiple power inputs provide redundant backup and improve system reliability. This multi-power system can also be applied to power output scenarios, such as motor drives. The difference is that when all power inputs are disconnected, the drive output must be blocked to prevent the situation where PWM output continues even after the power input is disconnected. To achieve this, a multi-input power-off protection circuit is designed. When all input power supplies are disconnected, it can output a power-off signal to the MCU, allowing it to promptly save system configuration information and operating data, or shut down PWM output.

[0003] Existing power-off protection usually uses sampling and power-off detection circuits such as comparators. If power-off detection is performed on multiple inputs separately, there will be problems such as high cost and MCU resource occupation. Utility Model Content

[0004] The utility model aims to provide a power-off protection circuit for multiple input power supplies to solve the above technical problems. The technical solution is as follows:

[0005] A power-off protection circuit for multiple input power supplies, comprising multiple input power branches and a power-off protection circuit;

[0006] The power-off protection circuit includes a first switch tube and a second switch tube;

[0007] The first output terminal of the first switching tube is connected to the first power supply through a resistor and is connected to the control terminal of the second switching tube; the second output terminal of the first switching tube is grounded; the control terminal of the first switching tube is the input terminal of the power-off protection circuit and is grounded through a parallel voltage stabilizing element and a resistor;

[0008] The first output terminal of the second switch tube is the output terminal of the power-off protection circuit, connected to the second power supply through a resistor, and outputs a power-off signal; the second output terminal of the second switch tube is grounded;

[0009] Each input power supply branch includes a first diode, a second diode and a resistor; each input power supply is connected to the input end of the power-down protection circuit through a first diode and a resistor; and is connected to the input end of the power supply module through a second diode to supply power to the power supply module; the first power supply and the second power supply are directly or indirectly generated by the power supply module, and the voltage of the first power supply is not lower than the voltage of the second power supply.

[0010] Further, the first switching tube is an NMOS transistor or an NPN triode. When the first switching tube is an NPN triode, a current-limiting resistor is connected in series between the control end of the first switching tube and the input end of the power-down protection circuit.

[0011] Further, the second switching tube is an NMOS transistor or an NPN triode. When the second switching tube is an NPN triode, a current-limiting resistor is connected in series between the control end of the second switching tube and the first output end of the first switching tube.

[0012] Further, the voltage stabilizing element is a voltage stabilizing diode, a voltage stabilizing triode or an integrated voltage regulator.

[0013] Further, each input power supply branch further includes a power switch.

[0014] Further, the power switch is a self-locking button, a rocker switch or a relay.

[0015] Further, the power switch is a PMOS transistor or a PNP triode.

[0016] Further, the power-down protection circuit of the multi-input power supply is controlled by a multi-channel switch, and the power switch is a certain switch unit of the multi-channel switch.

[0017] The present invention achieves the following technical effects:

[0018] This power-down protection circuit is simple and reliable, and can realize the power-down detection of multiple input power supplies without using a sampling and power-down detection circuit such as a comparator. Description of the Drawings

[0019] Figure 1 It is the circuit diagram of the embodiment of the power-down protection circuit of the multi-input power supply of the present invention. Detailed Embodiment

[0020] To further illustrate each embodiment, the present utility model provides accompanying drawings. These drawings are part of the disclosure of the present utility model, mainly used to illustrate the embodiments and can be combined with the relevant descriptions in the specification to explain the operating principle of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present utility model.

[0021] The present utility model will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0022] As Figure 1 shown, the present utility model provides an embodiment of a power-down protection circuit for a multi-input power supply, which consists of three power input branches and a power-down protection circuit, etc. The power-down protection circuit consists of a zener diode Z1, switching transistors Q1, Q2, resistors R4, R5, R6, etc. Among them, Q1 and Q2 are NMOS transistors. The drain of Q2 is connected to the power supply VCC through the resistor R4 and is connected to the gate of Q1; the source of Q2 is grounded. The gate of Q2 is the input end of the power-down protection circuit and is grounded through the parallel-connected zener diode Z1 and resistor R5. The zener diode Z1 can stabilize the gate voltage of Q2 to ensure that the gate voltage of Q2 is within a safe voltage range. R5 plays a role in voltage division and current shunting, and can prevent the zener diode Z1 from overvoltage and overcurrent.

[0023] The drain of Q1 is the output end of the power-down protection circuit. The drain of Q1 is connected to the 3.3V power supply through the resistor R6 to output a power-down signal; the source of Q1 is grounded.

[0024] In this embodiment, there are three power input branches, and the circuit structures of each power input branch are the same. One of the power input branches consists of a power switch RLY1A, diodes D1, D2, and a resistor R1, etc. The switch RLY1A controls the conduction of the power input branch, and the diodes D1 and D2 use their unidirectional conductivity to play a role in circuit interruption, and the resistor R1 plays a current limiting role.

[0025] This circuit is particularly suitable for the power-down protection of multi-input power supplies. Its main principle is that when power is lost, the input power supply always drops faster than the system power supply VCC. VCC is the system power supply. When any one of the three front power input branches is closed (this switch can be an electronic switch or any other physical switch), and multiple inputs can be closed simultaneously, the system power supply VCC can be generated through the DC-DC power module. At the same time, through resistor voltage division and the voltage stabilization control of the zener diode Z1, the gate voltage of Q2 is pulled from low level to high level. Then, in the power-down protection circuit, when the gate voltage of Q2 is high level, Q2 conducts, the drain output of Q2 is low level, pulling the gate voltage of Q1 to low level. The gate-source voltage Vgs of Q1 cannot meet the conduction requirement, so Q1 is in the off state, and the drain of Q1 outputs a high-level POWER DOWN signal to the MCU or to the blocking circuit. According to the definition, the POWER DOWN signal is active low, so the power-down protection is not triggered at this time. When all input switches are disconnected, there is no energy storage element at the gate of Q2, and the gate voltage will quickly drop. The gate-source voltage Vgs of Q2 cannot meet the conduction requirement, so Q2 is in the off state. At this time, the gate voltage of Q1 connected to the drain of Q2 is determined by the system power supply VCC. Since there are energy storage elements such as the energy storage capacitor C1 connected to the system power supply VCC, the charge stored in the energy storage element will pull the gate voltage of Q1 to high level, driving Q1 to conduct and output a low-level POWER DOWN signal. When the MCU detects the low-level POWER DOWN signal, it blocks the drive to avoid the working condition where the power input has been disconnected but the PWM wave is still being output all the time, improving the reliability of the system; since the power supply 3.3V for the MCU always comes from the power supply VCC, this detection and protection is always effective.

[0026] In specific applications, the power input branch can be extended to N paths, where N is an integer greater than or equal to 2, not limited to the three paths in this embodiment.

[0027] In this embodiment, the power switches RLY1A, RLY1B, and RLY1C can be switch devices such as self-locking buttons, rocker switches, or relays. The power switch can also be an electronic switch, such as a PMOS transistor or a PNP bipolar transistor, controlled by the MCU or an external control signal.

[0028] In this embodiment, the power switches RLY1A, RLY1B, and RLY1C can also be a certain switch unit of a multi-channel switch device. The multi-channel switch device can be a switch device such as a self-locking button, a rocker switch, or a relay.

[0029] This power-down protection circuit is simple and reliable, and can achieve power-down detection for multiple input power supplies without using a sampling and power-down detection circuit such as a comparator.

[0030] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the form and details of the present invention without departing from the spirit and scope of the present invention as defined by the appended claims, and all of these changes are within the scope of protection of the present invention.

Claims

1. A power-down protection circuit for a multi-input power supply, characterized in that: It includes multiple input power branches and a power-off protection circuit; The power-off protection circuit includes a first switch tube and a second switch tube; The first output terminal of the first switching tube is connected to the first power supply through a resistor and is connected to the control terminal of the second switching tube; the second output terminal of the first switching tube is grounded; the control terminal of the first switching tube is the input terminal of the power-off protection circuit and is grounded through a parallel voltage stabilizing element and a resistor; The first output end of the second switch tube is the output end of the power-off protection circuit, connected to the second power supply through a resistor, and outputs a power-off signal; The second output terminal of the second switch tube is grounded; Each input power branch includes a first diode, a second diode and a resistor; each input power is connected to the input end of the power-off protection circuit through a first diode and a resistor; and is connected to the input end of the power module through a second diode to supply power to the power module; the first power supply and the second power supply are directly or indirectly generated by the power module.

2. The power-down protection circuit of the multi-input power supply according to claim 1, wherein: The first switch tube is an NMOS tube or an NPN transistor. When the first switch tube is an NPN transistor, a current limiting resistor is connected in series between the control end of the first switch tube and the input end of the power-off protection circuit.

3. The power-off protection circuit for a multi-input power supply according to claim 1, wherein: The second switch tube is an NMOS tube or an NPN transistor. When the second switch tube is an NPN transistor, a current-limiting resistor is connected in series between the control end of the second switch tube and the first output end of the first switch tube.

4. The power-off protection circuit for a multi-input power supply according to claim 1, wherein: The voltage stabilizing element is a voltage stabilizing diode, a voltage stabilizing transistor or an integrated voltage stabilizer.

5. The power-down protection circuit for a multi-input power supply according to claim 1, characterized in that: Each input power branch also includes a power switch.

6. The power-off protection circuit for a multi-input power supply according to claim 5, wherein: The power switch is a self-locking button, a rocker switch or a relay.

7. The power-off protection circuit for a multi-input power supply according to claim 5, wherein: The power switch is a PMOS transistor or a PNP transistor.

8. The power-down protection circuit of the multi-input power supply according to claim 5, characterized in that: The power-off protection circuit of the multi-input power supply is controlled by a multi-channel switch, and the power switch is a switch unit of the multi-channel switch.

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