Overvoltage protection circuit and input protection power supply

Abstract

The utility model provides an overvoltage protection circuit and an input protection power supply. The overvoltage protection circuit comprises a diode D13, a resistor R31, a resistor R32, a resistor R34, a triode Q3 and a switch relay. The anode of the diode D13 is connected with a power supply AC-N1, and the cathode of the diode D13 is connected to a grounding end after passing through the resistor R31 and the resistor R32 in sequence; the base electrode of the triode Q3 is connected to a connecting line between the resistor R31 and the resistor R32 through the resistor R34, the collector electrode of the triode Q3 is connected to a grounding end, and the emitter electrode of the triode Q3 is connected to a power supply AC-N2 through the switch relay. The overvoltage protection circuit can automatically jump to disconnect power supply input during overvoltage, thereby ensuring the safety of a power supply circuit and eliminating fire hazards; and meanwhile, a self-recovery overvoltage protection function is also realized.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply circuits, in particular to an overvoltage protection circuit and an input protection power supply. Background Art

[0002] With the development of society and the improvement of people's living standards, there are new requirements for product safety indicators, especially in certain specific application scenarios. For example, libraries, bedrooms, medical institutions, etc., all require extremely high safety requirements and require the equipment to be equipped with sufficient safety measures.

[0003] The existing power adapter frame structure is as follows Figure 1 As shown, the overvoltage protection device is only a MOV1 varistor. The overvoltage protection design of this varistor is mainly for instantaneous ms-level overvoltage. When abnormal high voltage continues to flow through the product, the varistor needs to continue to work, and the large current will cause the varistor to burn, posing a fire hazard.

[0004] Therefore, a more reliable overvoltage protection mechanism is urgently needed to ensure that the power supply voltage is always within the safety requirement range. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide an overvoltage protection circuit and an input protection power supply, which can automatically jump and disconnect the power input when overvoltage occurs, thereby ensuring the safety of the power circuit and eliminating the fire hazard.

[0006] In order to solve the above technical problems, the first technical solution adopted by the utility model is:

[0007] An overvoltage protection circuit includes a diode D13, a resistor R31, a resistor R32, a resistor R34, a transistor Q3, and a switch relay;

[0008] The anode of the diode D13 is connected to the power supply AC-N1, and the cathode is connected to the ground terminal via the resistor R31 and the resistor R32 in sequence; the base of the transistor Q3 is connected to the connecting line between the resistor R31 and the resistor R32 via the resistor R34, the collector is connected to the ground terminal, and the emitter is connected to the power supply AC-N2 via the switch relay.

[0009] In some embodiments, a resistor R33 is further included; the base of the transistor Q3 is also connected to the ground terminal via the resistor R33.

[0010] In some embodiments, a diode D8 is further included; the diode D8 is connected in parallel at both ends of the switch relay.

[0011] In some embodiments, a voltage regulator is also included; one end of the resistor R34 is connected to the ground via the voltage regulator; wherein one end of the resistor R34 is connected to one end of a connecting line between the resistor R31 and the resistor R32.

[0012] In some embodiments, the Zener diode includes a Zener diode D10 and a Zener diode D11; the cathode of the Zener diode D10 is connected to the resistor R34, and the anode is connected to the anode of the Zener diode D11; the cathode of the Zener diode D11 is connected to the ground terminal.

[0013] In some embodiments, the voltage regulation value of the voltage regulator tube D10 and the voltage regulator tube D11 is 1-3V.

[0014] In some embodiments, the transistor Q3 is a bipolar junction power transistor.

[0015] In some embodiments, the transistor Q3 has a model of 7N650VDC.

[0016] The second technical solution adopted by the utility model is:

[0017] An input protection power supply comprises a power input terminal, an input filter circuit and the above-mentioned overvoltage protection circuit; the power input terminal, the overvoltage protection circuit and the input filter circuit are connected in sequence.

[0018] In some embodiments, it also includes a rectifier filter circuit, an IC control circuit, a transformer, an output freewheeling control circuit, and an output voltage feedback circuit;

[0019] The input filter circuit is connected to the rectifier filter circuit and the IC control circuit respectively; the rectifier filter circuit and the IC control circuit are also connected to the primary end of the transformer respectively; the output freewheeling control circuit and the output voltage feedback circuit are respectively connected to the secondary end of the transformer; the output voltage feedback circuit is also connected to the output freewheeling control circuit and the IC control circuit respectively.

[0020] The beneficial effects of the utility model are: an overvoltage protection circuit is set at the input end of the power supply, and the overvoltage protection circuit can monitor the voltage difference between the power supply AC-N and AC-L. When the voltage difference is too large, the transistor Q3 will be turned on, and the current will generate a magnetic field after passing through the switch relay to drive the switch to jump, thereby disconnecting the AC-N circuit, thereby protecting the power supply circuit; and the overvoltage protection can be restored by simply changing the switch relay back to the normally closed state. Compared with the prior art, the utility model can not only automatically disconnect the circuit when overvoltage occurs, so that the power supply circuit is protected, and provide overvoltage protection longer than the ms level, thereby eliminating fire hazards; it also has a self-recovering overvoltage protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a circuit connection diagram of a power supply circuit in the prior art;

[0022] Figure 2 A circuit connection diagram of an overvoltage protection circuit provided by an embodiment of the utility model;

[0023] Figure 3 A circuit connection diagram of an overvoltage protection circuit provided for a specific implementation of the utility model;

[0024] Figure 4 A circuit connection diagram of an input protection power supply provided by an embodiment of the present invention.

[0025] Description of labels:

[0026] 1. Power input terminal; 2. Input filter circuit; 3. Overvoltage protection circuit;

[0027] 4. Rectification and filtering circuit; 5. IC control circuit; 6. Transformer; 7. Output freewheeling control circuit;

[0028] 8. Output voltage feedback circuit. DETAILED DESCRIPTION

[0029] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0030] Please refer to Figure 2 and Figure 3 , Embodiment 1 of the present utility model is:

[0031] The utility model provides an overvoltage protection circuit. The overvoltage protection circuit is arranged at a power input end, specifically before an input filter circuit.

[0032] like Figure 2 As shown, the overvoltage protection circuit includes a diode D13, a resistor R31, a resistor R32, a resistor R34, a transistor Q3, and a switch relay;

[0033] The anode of the diode D13 is connected to the power supply AC-N1, and the cathode is connected to the ground terminal via the resistor R31 and the resistor R32 in sequence; the base of the transistor Q3 is connected to the connection line between the resistor R31 and the resistor R32 via the resistor R34, the collector is connected to the ground terminal, and the emitter is connected to the power supply AC-N2 via the switch relay. The power supply AC-N1 and the power supply AC-N2 are two connection points on the power supply AC-N (i.e., the power supply neutral line).

[0034] Wherein, the diode D13 is a high voltage rectifier diode, which is used to rectify the AC sine wave into a positive half sine wave;

[0035] The resistor R31 and the resistor R32 are voltage-dividing sampling resistors connected to both ends of the power supply AC-L and AC-N;

[0036] The resistor R34 is a driving resistor of the transistor Q3 and is used to adjust the driving current of the transistor Q3;

[0037] The transistor Q3 is a high-voltage resistant switching transistor. When a sufficiently large current flows through the resistor R34, the transistor Q3 can be turned on. The conventional AC working voltage of the transistor Q3 is 220Vac, and the optional model is 7N650VDC, and a bipolar junction power transistor can be selected.

[0038] The switch relay RL1 is an electromagnetic switch relay, which generates magnetic flux after current passes through, and the electromagnetic flux generates stress to open its switch K1, thereby disconnecting the normally closed line (AC-N1 to AC-N2) on the circuit. A copper coil + switch combination is optional.

[0039] The working principle of the overvoltage protection circuit described in this embodiment is:

[0040] There is a voltage difference between the power supply AC-N and AC-L. Under normal conditions, the working voltage at both ends of AC-N and AC-L is 220VAC or other 110VAC, which is a normal working voltage; at the same time, the transistor Q3 is disconnected and the switch relay is normally closed.

[0041] When a high voltage exceeding the normal voltage appears, such as the working voltage at both ends of AC-N and AC-L continuously exceeding the rated voltage, the sampling voltage at the positions of resistors R31, R32 and R34 in the overvoltage protection circuit set at the input end of the power circuit will increase and exceed the starting voltage of transistor Q3. At this time, transistor Q3 will be turned on, and current will flow through the switch relay; after a large current passes through the switch relay, a magnetic field is generated, driving the switch to jump, so that the AC-N line is disconnected, the power circuit (adapter) is disconnected, and the large voltage is not allowed to flow into the power circuit, thereby protecting the power circuit.

[0042] When restoration is needed after troubleshooting, the overvoltage protection can be automatically restored by simply restoring the switch relay to the normally closed state, which is significantly different from the existing overvoltage protection method that uses a varistor that cannot be self-restored.

[0043] That is to say, the overvoltage protection circuit provided in this embodiment can automatically start overvoltage protection when abnormally high voltage is detected, and protect the power circuit by cutting off AC-N. Compared with the existing overvoltage protection using varistors, it is easy to burn after abnormally high voltage continues to flow, posing a fire hazard. The overvoltage protection circuit provided in this embodiment has the advantages of higher reliability, elimination of fire hazards, simple structure, and easy implementation.

[0044] In some specific embodiments, Figure 3 As shown, the overvoltage protection circuit further includes a resistor R33; the base of the transistor Q3 is also connected to the ground terminal via the resistor R33.

[0045] Here, the resistor R33 is used as a discharge resistor of the transistor Q3 to discharge the residual voltage after the transistor Q3 stops working, so as to protect the safety of components in the overvoltage protection circuit and avoid the risk of electric shock.

[0046] In some specific embodiments, Figure 3 As shown, the overvoltage protection circuit further includes a diode D8; the diode D8 is connected in parallel at both ends of the switch relay.

[0047] Here, the diode D8 is a freewheeling diode, which is used to allow the residual inductive current in the switch relay to form a loop, and consume the residual inductive current in the switch relay through freewheeling to avoid false triggering, thereby improving the reliability of shutdown control.

[0048] In some specific embodiments, the overvoltage protection circuit also includes a Zener diode; one end of the resistor R34 is connected to the ground terminal via the Zener diode; wherein one end of the resistor R34 is connected to one end of the connecting line between the resistor R31 and the resistor R32, that is, the end not connected to the base of the transistor Q3.

[0049] Here, the voltage regulator is used to stabilize the voltage across the resistor R32.

[0050] Alternatively, if Figure 3 As shown, the voltage regulator tube is specifically composed of a voltage regulator tube D10 and a voltage regulator tube D11. The cathode of the voltage regulator tube D10 is connected to the resistor R34, and the anode is connected to the anode of the voltage regulator tube D11; the cathode of the voltage regulator tube D11 is connected to the ground terminal. The voltage regulator values ​​of the voltage regulator tubes D10 and D11 can be selected in the range of 1-3V, preferably about 1V to meet the demand, and can also avoid the surge voltage being too high and damaging the transistor Q3.

[0051] Please refer to Figure 4 , Embodiment 2 of the present utility model is:

[0052] Based on the embodiment, this embodiment provides an input protection power supply, which provides overvoltage protection lasting longer than the ms level and a self-recovering overvoltage protection function by setting the overvoltage protection circuit described in embodiment 1 at the input end of the power supply circuit.

[0053] This embodiment provides an input protection power supply, such as Figure 4 As shown, it includes a power input terminal 1, an input filter circuit 2 and an overvoltage protection circuit 3 described in Example 1; the power input terminal 1, the overvoltage protection circuit 3 and the input filter circuit 2 are connected in sequence. The power input terminal is the power supply AC, which specifically includes AC-N and AC-L; the specific circuit structure of the overvoltage protection circuit is not repeated here, please refer to the description of Example 1 for details.

[0054] In some specific embodiments, Figure 4 As shown, the input protection power supply also includes a rectifier filter circuit 4, an IC control circuit 5, a transformer 6, an output freewheeling control circuit 7 and an output voltage feedback circuit 8; wherein the input filter circuit 2 is connected to the rectifier filter circuit 4 and the IC control circuit 5 respectively; the rectifier filter circuit 4 and the IC control circuit 5 are also connected to the primary end of the transformer 6 respectively; the output freewheeling control circuit 7 and the output voltage feedback circuit 8 are respectively connected to the secondary end of the transformer 6; the output voltage feedback circuit 8 is also connected to the output freewheeling control circuit 7 and the IC control circuit 5 respectively.

[0055] Here, the input filter circuit is responsible for filtering out the input voltage interference;

[0056] Rectification and filtering circuit, used to rectify AC power into DC output;

[0057] IC control circuit, responsible for the switch control of the power supply, as a protection control unit;

[0058] Transformer, which acts as an energy exchange unit between input primary and output secondary;

[0059] Output freewheeling control circuit, as a charging and discharging component for outputting electrical energy;

[0060] The output voltage feedback circuit, as an output voltage feedback unit, feeds back the secondary voltage signal to the primary IC control circuit, and adjusts the energy exchange between the primary and secondary to achieve the adjustment of the secondary voltage by controlling the primary switch unit through the IC.

[0061] Compared with the prior art that relies on varistors for overvoltage protection, the input protection power supply provided in this embodiment cannot cope well with continuous abnormally high voltages and has the disadvantage of fire hazards. The power supply product of this embodiment sets an overvoltage protection circuit at the input end, which can automatically start overvoltage protection when abnormally high voltage is detected, and protect the power supply circuit by cutting off AC-N. It can not only provide overvoltage protection for a longer time than the ms level and eliminate fire hazards, but also has a self-recovery overvoltage protection function.

[0062] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. An overvoltage protection circuit, characterized in that: It includes a diode D13, a resistor R31, a resistor R32, a resistor R34, a transistor Q3, and a switch relay; The anode of the diode D13 is connected to the power supply AC-N1, and the cathode is connected to the ground terminal via the resistor R31 and the resistor R32 in sequence; the base of the transistor Q3 is connected to the connecting line between the resistor R31 and the resistor R32 via the resistor R34, the collector is connected to the ground terminal, and the emitter is connected to the power supply AC-N2 via the switch relay.

2. An overvoltage protection circuit as claimed in claim 1, characterized in that: A resistor R33 is also included; the base of the transistor Q3 is also connected to the ground terminal via the resistor R33.

3. An overvoltage protection circuit as claimed in claim 1, characterized in that: A diode D8 is also included; the diode D8 is connected in parallel at both ends of the switch relay.

4. An overvoltage protection circuit as claimed in claim 1, characterized in that: It also includes a voltage regulator tube; one end of the resistor R34 is connected to the ground terminal via the voltage regulator tube; wherein one end of the resistor R34 is connected to one end of the connecting line between the resistor R31 and the resistor R32.

5. An overvoltage protection circuit as claimed in claim 4, characterized in that: The voltage regulator tube includes a voltage regulator tube D10 and a voltage regulator tube D11; the cathode of the voltage regulator tube D10 is connected to the resistor R34, and the anode is connected to the anode of the voltage regulator tube D11; the cathode of the voltage regulator tube D11 is connected to the ground terminal.

6. An overvoltage protection circuit as claimed in claim 5, characterized in that: The voltage stabilization value of the voltage stabilizing tube D10 and the voltage stabilizing tube D11 is 1-3V.

7. An overvoltage protection circuit as claimed in claim 1, characterized in that: The transistor Q3 is a bipolar junction power transistor.

8. An overvoltage protection circuit as claimed in claim 1, characterized in that: The model of the transistor Q3 is 7N650VDC.

9. An input protection power supply, characterized in that: It comprises a power input terminal, an input filter circuit and an overvoltage protection circuit as claimed in any one of claims 1 to 8; the power input terminal, the overvoltage protection circuit and the input filter circuit are connected in sequence.

10. An input protection power supply as claimed in claim 9, characterized in that: It also includes a rectifier filter circuit, an IC control circuit, a transformer, an output freewheeling control circuit, and an output voltage feedback circuit; The input filter circuit is connected to the rectifier filter circuit and the IC control circuit respectively; the rectifier filter circuit and the IC control circuit are also connected to the primary end of the transformer respectively; the output freewheeling control circuit and the output voltage feedback circuit are respectively connected to the secondary end of the transformer; the output voltage feedback circuit is also connected to the output freewheeling control circuit and the IC control circuit respectively.

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