High-voltage power supply personal protection circuit

Abstract

The utility model discloses a high-voltage power supply personal protection circuit which comprises a depletion type MOS tube and a first bleeder resistor, a drain electrode of the depletion type MOS tube is connected with an output positive electrode of a high-voltage power supply, a source electrode of the depletion type MOS tube is connected with one end of the first bleeder resistor, the other end of the first bleeder resistor is connected with an output negative electrode of the high-voltage power supply, and the other end of the first bleeder resistor is connected with an output positive electrode of the high-voltage power supply. The grid electrode of the depletion type MOS tube is connected with the output negative electrode of the high-voltage power supply, and when the high-voltage power supply outputs voltage, the depletion type MOS tube works until the output voltage of the high-voltage power supply is 0V. According to the utility model, the characteristic of the depletion type MOS tube is used as a constant current source, the structure is simple, the performance is stable, the space volume of a machine can be saved, and the problem that the existing constant current source does not work due to internal power failure of the machine is solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to high voltage power supply technical field, concretely relates to a high voltage power supply personal protection circuit. BACKGROUND

[0002] In high voltage power supply product, when local protection shutdown or external high voltage source is disconnected, there is a high voltage on the output port when the local machine is in shutdown state, and the staff will think it is safe when discovering that the power supply is shutdown, thereby touching the output port and causing electric shock, so a circuit or device that can quickly discharge voltage when the machine is shutdown and indicate that there is high voltage at this time is needed to protect personal safety.

[0003] At present, in the high voltage power supply part of the power supply industry, internal constant current source or external high voltage detection circuit is generally used to quickly reduce the port voltage when needed, but both of the two schemes have defects. Internal constant current source generally uses operational amplifier chip to control N-type MOS tube G pole, MOS tube D pole connects the positive end of output, MOS tube S pole connects the negative end of output in series with a current limiting resistor, and a constant current is used to pull the output voltage during work. The advantages of this circuit are small occupied volume and adjustable constant current, and the disadvantages are that operational amplifier power supply must be in working state, and once shutdown or machine failure occurs, the constant current source cannot work, so it cannot protect personal safety in the above specific conditions. In addition, constant current source will continuously consume power of fixed current value, and if the power supply is used for battery power supply, the battery will be continuously consumed, causing battery undervoltage.

[0004] There are many methods for using external high voltage detection circuit, which is generally externally connected to the power supply, and there is a relay or contactor inside to shut off voltage output, and the relay or contactor is immediately cut off when the output voltage of the local machine and the external voltage exist pressure difference, at this time, although the power supply output still has high voltage and cannot be discharged, the output of high voltage detection circuit has no high voltage. The advantages of this scheme are fast protection speed, no power consumption when connected to battery, and meeting the demand of personal safety protection. The disadvantage is that an external device needs to be hung, which occupies a large space. UTILITY MODEL CONTENTS

[0005] The utility model aims at overcoming the defects in the prior art, and provides a high voltage power supply personal protection circuit.

[0006] The utility model discloses a high voltage power supply personal protection circuit, including depletion MOS tube and first discharge resistance, the drain of depletion MOS tube connects the output positive pole of high voltage power supply, the source of depletion MOS tube connects one end of first discharge resistance, the other end of first discharge resistance connects the output negative pole of high voltage power supply, the gate of depletion MOS tube connects the output negative pole of high voltage power supply, when high voltage power supply output voltage, depletion MOS tube works, until high voltage power supply output voltage is 0V, and the constant current source will not work because of the machine internal power failure.

[0007] Further, it further includes a light emitting diode and a second discharge resistance, the light emitting diode is used as a high voltage indicator, the second discharge resistance is connected in series between the source of the depletion MOS tube and the first discharge resistance, and the light emitting diode is connected in parallel with the second discharge resistance.

[0008] Further, it further includes a relay, the normally open contact of the relay is connected to the negative pole of the internal power supply and the gate of the depletion MOS tube, the coil pin of the relay is connected to the ground and the positive pole of the internal power supply respectively, when the high voltage power supply works normally, the internal power supply works normally, the relay works, the normally open contact is closed, and the depletion MOS tube is cut off, so that no constant current loss occurs when the power supply works normally.

[0009] Further, it further includes a capacitor and a third resistance, the gate of the depletion MOS tube is connected to the output negative pole of the high voltage power supply through the third resistance, the first end of the third resistance is connected to the gate of the depletion MOS tube, the second end of the third resistance is connected to the output negative pole of the high voltage power supply, the first end of the capacitor is connected to the first end of the third resistance and the normally open contact of the relay, and the second end of the capacitor is connected to the second end of the third resistance. The capacitor is used for absorbing the transient voltage peak generated by the relay working and preventing the circuit from malfunctioning.

[0010] The utility model discloses the beneficial effect brought by technical scheme has:

[0011] 1, this circuit can practically drain the high voltage power supply output port voltage, need not external high voltage protection circuit, save space and cost, also can make up the shortcoming that general constant current source does not work after shutdown, unconditional, low -cost protection personal safety, prevent electric shock;

[0012] 2, by adding the normally open relay, the high voltage protection circuit and constant current source are combined into one, can drain voltage when the high voltage power supply is shutdown, protect personal safety, and can reduce output loss when the high voltage power supply works normally, improve output accuracy. DRAWINGS

[0013] Figure 1 A high voltage power supply personal protection circuit schematic diagram is provided for the utility model.

[0014] Figure 2 A schematic diagram of another high-voltage power supply personal protection circuit provided by this utility model. Detailed Implementation

[0015] The technical solution of this utility model will be described in detail below, but the protection scope of this utility model is not limited to the embodiments described.

[0016] like Figure 1 As shown, this utility model discloses a high-voltage power supply personal protection circuit, which is a novel constant current source circuit. It removes the operational amplifier circuit of the existing constant current source and uses a depletion-type MOSFET Q1 as the main conductor of the constant current source. It includes a depletion-type MOSFET Q1 and a first bleeder resistor R2. The drain of the depletion-type MOSFET Q1 is connected to the positive output of the high-voltage power supply, and the source of the depletion-type MOSFET Q1 is connected in series with the first bleeder resistor R2. The other end of the first bleeder resistor R2 is connected to the negative output of the high-voltage power supply, and the gate of the depletion-type MOSFET Q1 is connected to the negative output of the high-voltage power supply.

[0017] To indicate the presence of residual high voltage at the output port of the high-voltage power supply after shutdown, an LED D1 and a second bleeder resistor R1 are included. The second bleeder resistor R1 is connected in series between the source of the depletion-type MOSFET Q1 and the first bleeder resistor R2. The LED D1 is connected in parallel with the second bleeder resistor R1. When the voltage difference is sufficiently large, the LED D1 stops working once it falls below a certain voltage. If used in series with a resistor, the tail of the diode's voltage drop will remain in the power supply, preventing the power supply voltage from being cleared to zero and affecting its operation.

[0018] The values ​​of the first bleeder resistor R2 and the second bleeder resistor R1 are selected based on the highest voltage of the high-voltage power supply. The first bleeder resistor R2 is the main bleeder resistor, and the second bleeder resistor R1 is the auxiliary bleeder resistor. When the high-voltage power supply outputs voltage, because the gate of the depletion-type MOSFET Q1 is negatively charged relative to its source, and within the Vgs range of the depletion-type MOSFET Q1, Q1 conducts, reducing the voltage with a constant current. No matter how low the high-voltage power supply output voltage drops, the drive of the depletion-type MOSFET Q1 remains negative, allowing it to remain on and bleed the high-voltage power supply output voltage to 0V. Therefore, when the high-voltage power supply is turned off, as long as there is power at the high-voltage power supply port, this circuit can continue to work until the port voltage is reduced to 0V. Utilizing the inherent characteristics of the depletion-type MOSFET as a constant current source results in a simple structure, stable performance, and saves machine space, solving the problem of existing constant current sources failing to operate due to internal power outages.

[0019] Figure 2 Is Figure 1 An additional normally open relay was added to the basic design. For example...Figure 2 As shown, another high-voltage power supply personal protection circuit disclosed in this utility model is similar to... Figure 1 The disclosed high-voltage power supply personal protection circuit differs in that it also includes a relay K1, a third resistor R3, and a capacitor C1. The normally open contact 3 of relay K1 is connected to the negative terminal of the internal power supply, the normally open contact 4 of relay K1 is connected to the gate of the depletion-type MOSFET, the coil pin 2 of relay K1 is connected to the positive terminal of the internal power supply, and the coil pin 1 of relay K1 is grounded. The internal power supply is ±12V. When the high-voltage power supply is operating normally, with ±12V available, relay K1 operates, its normally open contact closes, and the negative 12V is connected to the gate of the depletion-type MOSFET Q1. Since the negative 12V voltage is lower than the turn-on voltage of the depletion-type MOSFET Q1, Q1 is turned off, and the constant current source does not start. When the high-voltage power supply is protected or shut down, the internal positive 12V power supply is lost, the normally open relay K1 is not connected, the normally open contact is open, and the negative 12V is disconnected. At this time, when the high-voltage power supply outputs voltage, since the gate of the depletion-type MOSFET Q1 is negatively charged relative to the source, and within the Vgs range of the depletion-type MOSFET Q1, the depletion-type MOSFET Q1 is turned on, and the voltage is reduced by a constant current.

[0020] The gate of the depletion-type MOSFET Q1 is connected to the negative output terminal of the high-voltage power supply through a third resistor R3. Specifically, the first terminal of the third resistor R3 is connected to the gate of Q1, and the second terminal is connected to the negative output terminal of the high-voltage power supply. R3 acts as a pull-down resistor for the MOSFET. The first terminal of capacitor C1 is connected to the first terminal of the third resistor R3, and the second terminal of capacitor C1 is connected to the second terminal of the third resistor R3. The normally open contact 4 of relay K1 is connected to the first terminal of capacitor C1. Capacitor C1 is used to absorb the instantaneous voltage spikes generated by the operation of relay K1, preventing circuit malfunction.

[0021] This circuit combines the advantages of a common constant current source and an external high-voltage detection circuit. When the high-voltage power supply is operating normally, there is no constant current loss, eliminating the need for current bias in control and preventing battery capacity depletion. During machine protection or shutdown, it provides constant current output voltage reduction protection, ensuring the constant current source will not fail to operate due to internal power outages.

[0022] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and detail may be made to the present invention without departing from the spirit and scope of the appended claims.

Claims

1. A high voltage power supply personal protection circuit, characterized by, It includes a depletion mode MOSFET, the drain of which is connected to the positive output of a high voltage power supply, the source of which is connected to one end of a first bleeder resistor, the other end of which is connected to the negative output of the high voltage power supply, and the gate of which is connected to the negative output of the high voltage power supply. When the high voltage power supply outputs a voltage, the depletion mode MOSFET operates until the output voltage of the high voltage power supply is 0V.

2. The high voltage power supply personal protection circuit according to claim 1, wherein, It also includes a light emitting diode as a high voltage indicator, and a second bleeder resistor connected in series between the source of the depletion mode MOSFET and the first bleeder resistor, and the light emitting diode is connected in parallel with the second bleeder resistor.

3. The high voltage power supply personal protection circuit of claim 1, wherein, It also includes a relay, the normally open contact of which is connected to the negative output of an internal power supply and the gate of the depletion mode MOSFET, and the coil pins of which are connected to ground and the positive output of the internal power supply, respectively. When the high voltage power supply is working normally and the internal power supply is working normally, the relay operates and the normally open contact is closed, and the depletion mode MOSFET is turned off.

4. The high voltage power supply personal protection circuit of claim 3, wherein, It also includes a capacitor and a third resistor, the gate of the depletion mode MOSFET being connected to the negative output of the high voltage power supply through the third resistor, the first end of the third resistor being connected to the gate of the depletion mode MOSFET, the second end of the third resistor being connected to the negative output of the high voltage power supply, the first end of the capacitor being connected to the first end of the third resistor and the normally open contact of the relay, and the second end of the capacitor being connected to the second end of the third resistor.

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