JP2014023300A - Overvoltage protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an overvoltage protection device capable of continuously blocking an AC power supply with certainty without human operations when an overvoltage of an AC power supply is detected, and that is small in size and light in weight.SOLUTION: An overvoltage protection device comprises: an input end AC_IN for an AC power supply; an output end AC_OUT for the AC power supply, connected to a protection target device; wires L1 and L2 coupling between the input end AC_IN and the output end AC_OUT; a normally-closed contact relay RY provided to the wire L1; an input state detector 2 connected to the wire L1, and configured to detect an overvoltage of the AC power supply; a relay drive circuit 3 coupled with the input state detector 2 in an electrically-insulated state, and configured to drive the relay RY; and a battery BAT supplying a power to the relay drive circuit 3. When the input state detector 2 detects the overvoltage, the relay drive circuit 3 drives and opens the normally-closed contact relay RY, and keeps the contact point of the relay in a released state by the power supply of the battery BAT.

Description

The present invention relates to an overvoltage protection device for protecting an electronic device by shutting off the power supply when an overvoltage is applied to the power supply in the electronic device.

  Since the voltage of the commercial AC power supply varies depending on the country or region, for example, when an electronic device using 100V is connected to a 220V power source, the electronic device is damaged by overvoltage. In order to protect an electronic device from such an overvoltage, an overvoltage protection device that is interposed between a commercial power source and the electronic device and protects the electronic device from the overvoltage is known.

  Conventionally, a transformer connected to an AC power supply, a normally closed contact (normally closed) relay provided on the primary side of the transformer, and a rectifier circuit, a smoothing capacitor, voltage detection means, and a drive circuit are provided on the secondary side of the transformer. An overvoltage protection device is known that is configured such that when the voltage detection means detects an overvoltage, the drive circuit drives a normally closed contact relay to cut off the AC power supply (see Patent Document 1).

  In the overvoltage protection device of Patent Document 1, when the voltage detection means detects an overvoltage, the normally closed contact relay is driven to cut off the AC power supply, but when the AC power supply is cut off, the power supply of the circuit on the secondary side of the transformer Is cut off and the drive circuit does not operate, so that the relay cannot be driven. For this reason, the normally closed contact once opened is closed again, and the AC power supply and electricity are connected again. The relay is repeatedly opened and closed unless a human operation such as removing the plug is performed. Moreover, since a low-frequency transformer is used as a transformer, the apparatus becomes heavy and large.

  Therefore, an overvoltage protection device using a normally open contact (normally open) relay has been proposed (see Patent Document 2). The overvoltage protection device of Patent Document 2 includes a normally open contact relay (energization holding relay) connected to the input side of the diode bridge, and a control unit that controls the voltage detection means and the normally open contact relay on the output side of the diode bridge. And a power supply unit for supplying power to the control unit. A non-holding switch (SW) is connected in parallel to the normally open contact.

  In the overvoltage protection device of Patent Document 2, since the relay contact is open in the initial state, no current flows. When the non-holding switch is operated, a current flows, a DC voltage is supplied from the power supply unit, and the control unit operates. A control part supplies with electricity to the coil of a relay, and the state where the contact of the relay was closed is held.

  When the overvoltage detection means detects an overvoltage, the control unit stops energization of the relay coil, the relay contact is opened, and the AC power supply is shut off. Since the relay is a normally open contact, the interruption state of the AC power supply is maintained.

JP-A-9-93941 JP 2011-120366 A

  However, even in the overvoltage protection device of Patent Document 2, if the non-holding type switch continues to be turned on for some reason, the overvoltage continues to be supplied to the load. Accordingly, there is a problem that the load cannot be protected from overvoltage unless a human operation is performed.

  An object of the present invention is to solve the above-mentioned problems and to provide a small and light overvoltage protection device that can reliably continue to cut off an AC power source even if no operation is performed when an overvoltage is detected. It is said.

In order to solve the above problems, an overvoltage protection device according to the present invention includes an input terminal of an AC power source, an output terminal of an AC power source to be protected, a wiring connecting the input terminal and the output terminal, and the wiring A normally-closed contact relay provided on the wiring, an input state detection unit that is connected to the wiring and detects an overvoltage of the AC power supply, and is electrically insulated from the input state detection unit and is coupled to drive the relay A relay driving circuit that supplies power to the relay driving circuit, and when the overvoltage is detected by the input state detection unit, the relay driving circuit holds the relay contact in the released state.

According to the above configuration, when an overvoltage is detected, the relay of the normally closed contact is held by the battery in a state where the contact is released (open), so that the relay is not repeatedly opened and closed and is not held. Since there is no type switch, it can be avoided that the non-holding type switch continues to be turned on by mistake and the alternating current continues to flow.

  In addition, the overvoltage protection device of the present invention includes a switching power supply connected to the wiring, a charge control circuit connected to the switching power supply for charging the battery, and detecting the voltage of the battery. In the case of a predetermined value or less, a battery voltage detection unit that drives the relay with a current from the switching power supply is further provided.

Even if the voltage of the battery drops, the battery is charged with the current of the switching power supply, and while the battery is charged, the contact of the relay is held open by the current of the switching power supply, so that it takes a long time. As a result, the power-off state can be maintained.

As described above, according to the present invention, the normally closed contact relay is not repeatedly opened and closed, and the contact open state is maintained. Further, since the non-holding type switch is not used, there is an advantage that the device to be protected can be reliably protected from overvoltage and safety can be improved without accidentally closing the relay. Furthermore, since a switching power supply is used as the power supply, the apparatus can be reduced in size and weight.

It is a block diagram explaining the overvoltage protection apparatus which concerns on embodiment of this invention. It is a circuit diagram explaining the input state detection part in FIG. 1, a relay drive circuit, and a battery voltage detection part. It is a circuit diagram explaining the charge control circuit in FIG. It is a circuit diagram explaining the switching power supply in FIG.

  An overvoltage protection device according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block diagram illustrating the overall configuration of the overvoltage protection device 1. The overvoltage protection device 1 is applied to a single-phase AC power supply, and includes an AC power supply input terminal AC_IN and an AC power supply output terminal AC_OUT. The AC power supply input terminal AC_IN can be constituted by a plug, and the AC power supply output terminal AC_OUT can be constituted by an outlet. The AC power supply input terminal AC_IN is connected to an AC power supply, and the AC power supply output terminal AC_OUT is connected to a protection target device.

  The AC power supply input terminal AC_IN and the AC power supply output terminal AC_OUT are connected by wirings L1 and L2. On the wiring L1, a fuse F1 and a normally closed contact (normally closed) relay (hereinafter simply referred to as a relay) RY are provided. D1 is a diode for preventing back electromotive force. Here, a single-pole single-throw relay is used, but a double-pole single-throw relay can be used so that a normally closed contact is inserted in each of the wirings L1 and L2.

  The overvoltage protection device 1 further includes an input state detection unit 2, a photo-coupler PC1, a relay drive circuit 3, a battery voltage detection unit 4, a lithium ion battery pack 5, a charge control circuit 6, and a switching power supply 7. . The input state detection unit 2 is connected to the point F of the wiring L1 and is connected to the LED (light emitting diode) 1 side of the photocoupler PC1. The input state detection unit 2 detects the voltage at the point F, and turns on the LED 1 of the photocoupler PC1 when the voltage at the point F exceeds a predetermined value. The reason why the photocoupler PC1 is interposed is to electrically insulate the AC power source (primary side) from the relay drive circuit 3 (secondary side).

  A phototransistor PTr1 side of the photocoupler PC1 is connected to the relay drive circuit 3. On the other hand, the relay drive wires B1 and B2 of the relay drive circuit 3 are connected to the coil of the relay RY. When a current flows through the phototransistor of the photocoupler PC1, the relay drive circuit 3 adds the current from the lithium battery ion pack 5 or the switching power supply 7 to the coil of the relay RY and opens the contact of the relay RY.

  The battery voltage detector 4 detects the voltage of the lithium ion battery (hereinafter simply referred to as the battery) BAT of the lithium ion battery pack 5. The battery voltage detector 4 supplies the current from the battery BAT to the relay drive circuit 3 when the voltage of the battery BAT is equal to or higher than a predetermined value. The battery voltage detection unit 4 drives the coil of the relay RY with the current from the switching power supply 7 when the voltage of the battery BAT is less than a predetermined value.

  The lithium ion battery pack 5 includes a battery BAT and a thermistor Th for detecting the temperature of the battery BAT. One end of the thermistor Th is connected to the charge control circuit 6. In this embodiment, a lithium ion battery is used as the battery, but a secondary battery such as a nickel cadmium battery or a nickel metal hydride battery can be used. In addition, an electric double layer capacitor can be used instead of the secondary battery.

  The charging control circuit 6 controls the charging of the battery BAT, and controls the charging current of the battery based on the temperature and the battery voltage detected by the thermistor Th. The battery voltage detected here is the voltage of the battery BAT detected by the charge control circuit 6 separately from the battery voltage detector 4.

  The switching power supply 7 has a primary side connected to the wirings L1 and L2. Note that power supply lines A1 and A2 to the input state detection unit 2 are drawn from the primary side of the switching power supply 7. V + and V− on the secondary side 7-2 of the switching power supply 7 are connected to the charge control circuit 6. V + is also connected to the battery voltage detector 4.

  Details of each circuit will be described below. FIG. 2 is a circuit diagram showing details of the input state detection unit 2, the relay drive circuit 3, and the battery voltage detection unit 4. The input state detection unit 2 includes a shunt regulator IC (Integrated Circuit) 1. The cathode K of the shunt regulator IC1 is connected to the power supply line A1 of the switching power supply 7 through the photocoupler LED1 and the resistor R1. The anode A of the shunt regulator IC1 is connected to the power supply line A2 of the switching power supply 7. The capacitor C1 is a bypass capacitor (hereinafter simply referred to as a bypass capacitor) of the shunt regulator IC1.

  The point F of the wiring L1 is connected to the power supply line A2 via the rectifier diode D2 and the resistors R2 and R3. The voltage divided by the resistors R2 and R3 is connected to the reference R of the shunt regulator IC1. The electrolytic capacitor C2 stabilizes the reference voltage. When the reference voltage becomes equal to or higher than a predetermined value (that is, when an overvoltage of the AC power supply occurs), a current flows between the cathode and the anode of the shunt regulator IC1, and the LED 1 is turned on.

  The relay drive circuit 3 includes resistors R4, R5, R6, and transistors Q1, Q2. The collector of the phototransistor PTr1 of the photocoupler PC1 is connected to the base of the transistor Q1, and the collector of the transistor Q1 is connected to the base of the transistor Q2. The collector of the transistor Q2 is connected to the relay drive wiring B2. When the LED of the photocoupler PC1 emits light, a current flows through the phototransistor PTr1 of the photocoupler PC1, the transistor Q1 is turned off, Q2 is turned on, and a current flows between B1 and B2. The relay RY is driven by this current, and the contact of the relay RY is opened.

Relay drive wirings B1 and B2 are connected to the battery voltage detection unit 4. The wiring B1 is also connected to the power supply line V + of the switching power supply 7 via the backflow prevention diode D3 and the transistor Q3. The base of the transistor Q3 is connected to the output of the comparator IC2 via the resistor R7.

The wiring B1 is further connected to the anode of the battery BAT via the backflow prevention diode D4 (E terminal). A voltage Vref obtained by dividing the voltage between the power supply lines V + and V− of the switching power supply 7 by the resistors R9 and R10 is applied to the inverting input of the comparator IC2. The voltage Ve obtained by dividing the voltage of the battery BAT by the resistors R11 and R12 is applied to the non-inverting input of the comparator IC2. When the battery voltage decreases and the voltage Ve becomes less than Vref, the output of the comparator IC2 becomes Low and the transistor Q3 is turned on. Then, the current of the switching power supply 7 is applied to the power supply line B1, and the relay RY is driven by the current from the switching power supply 7.

FIG. 3 is a circuit diagram showing details of the charge control circuit 3. The charge control circuit 3 includes a charge control IC 3 and a transistor Q4 and a resistor R13 are disposed on the power supply line V +. The base of the transistor Q4 is connected to the control terminal CONT of the charging control IC 3 via the resistor R16. The base and emitter of the transistor Q4 are connected via a resistor R17. The transistor Q4 is turned on / off by the control terminal CONT, and the charging current of the battery BAT is controlled.

A voltage from the power supply line V + is applied to the power supply terminal V (+) of the charging control IC 3. C3 is a bypass capacitor of the charging control IC3. The cathode of the LED 3 is connected to the terminal LED-G of the charging control IC 3, and the cathode of the LED 4 is connected to the terminal LED-R. The anode of the LED 3 is connected to the power supply line V + via the protective resistor R18. The anode of the LED 4 is connected to the power supply line V + via the protective resistor R19. LED3 and LED4 display the state of charge of the battery BAT. For example, LED3 is lit when fully charged, and LED4 is lit during charging.

  The charging current of the battery BAT flows through the resistor R13, the voltage drop is detected by the terminals CS1 and CS2, and the charging control IC 3 can monitor the charging current. A voltage obtained by dividing the battery voltage by R14 and R15 is applied to the terminal VS, and the charging control IC 3 charges the battery BAT based on the voltage of the terminal VS. The thermistor Th in the lithium ion battery pack 5 is connected to the TDET terminal of the charging control IC 3, detects the temperature of the battery BAT, and the charging control IC 3 controls the charging of the battery BAT.

  FIG. 4 is a circuit diagram illustrating details of the switching power supply 7. The switching power source 7 includes a primary side 7-1 connected to an AC power source, and a secondary side 7-2 coupled to the primary side 7-1 in an insulated state via a transformer T. The primary side 7-1 is connected to the AC power supply via the line filter 8 and the fuse F2. The alternating current from which noise has been removed through the line filter 8 is full-wave rectified by the diode bridge DB and smoothed by the capacitor C5.

The DC voltage smoothed by the capacitor C5 is applied to one end a11 of the primary side winding Tw11 of the transformer T. Further, the ground side of the DC voltage is connected to the GND terminal of the switching power supply IC 4. The switching power supply IC 4 is a so-called transistor built-in type, and performs a switching operation between the D terminal and the GND terminal by turning on / off the built-in transistor. The D terminal is connected to the other end b11 of the winding Tw11 of the transformer T. The Zener diode ZD and the diode D5 protect the switching power supply IC 4 from overvoltage.

One end a12 of the primary winding Tw12 of the transformer T is connected to the VDD terminal of the switching power supply IC4 and the power supply line A1 via the rectifying diode D7 and the resistor R21. The other end B12 of the primary winding Tw12 of the transformer T is connected to the GND terminal of the switching power supply IC4 and the power supply line A2. The capacitor C6 smoothes the voltage applied to the VDD terminal. The capacitor C7 is a bypass capacitor of the switching power supply IC4.

The anode of the diode D6 is connected to one end a12 of the primary winding Tw12. The voltage of the cathode of the diode D6 is connected to the CONT terminal of the switching power supply IC4 via the resistor R20 and monitored by the switching power supply IC4. The other end b12 of the primary winding Tw12 is connected to a brownout protection terminal BR.

The FB terminal of the switching power supply IC4 is connected to the collector of the phototransistor PTr2 of the photocoupler PC2. The emitter of the phototransistor PTr2 of the photocoupler PC2 is connected to the power supply line A2.

A terminal a2 of the secondary winding Tw2 of the transformer T is connected to the power supply line V + via a rectifying diode D8. The terminal b2 of the secondary winding Tw2 is connected to the power supply line V−. A voltage smoothing capacitor C8 is connected between the power supply lines V + and V−. Further, an LED 5 for confirming the operation of the switching power supply 7 and its protective resistor R25 are connected in series between the power supply lines V + and V−.

A shunt regulator IC5 is provided on the secondary side 7-2. A voltage between the power supply lines V + and V− is applied to the reference R of the shunt regulator IC5 by being divided by resistors R26 and R27. The anode A of the shunt regulator IC5 is connected to the power supply line V-. The cathode K of the shunt regulator IC5 is connected to the power supply line V + via the resistor R23 and the LED2 of the photocoupler PC2. The capacitor C9 is a bypass capacitor of the shunt regulator IC5.

When the voltage of V + increases, the voltage applied to the reference R of the shunt regulator IC5 increases, the current between the cathode K and the anode A increases, and the current of the LED 2 of the photocoupler PC2 also increases. When the current of LED2 increases, the current of phototransistor PTr2 of photocoupler PC2 also increases, the FB terminal voltage of switching power supply IC4 decreases, and the ON time of the transistor built in switching power supply IC4 decreases.

That is, when the shunt regulator IC 5 on the secondary side 7-2 detects a predetermined voltage, feedback control is applied so that the ON time of the transistor built in the switching power supply IC 4 on the primary side 7-1 changes. The photocoupler PC2 is used to electrically insulate the primary side 7-1 and the secondary side 7-2.

Next, the operation of the overvoltage protection device 1 will be described. In a normal state, the contact of the relay RY is closed, an alternating current flows through the input terminal AC_1 and the output terminal AC_2, and power is supplied to the protection target device connected to the output terminal AC_2. When the input terminal AC_1 is mistakenly connected to a high voltage AC power source, the voltage at the point F becomes abnormal. The input state detection unit 2 detects the abnormal voltage, a current flows between the cathode K and the anode A of the shunt regulator IC1, and the LED 1 of the photocoupler PC1 is turned on.

When the LED 1 of the photocoupler PC1 is turned on, the phototransistor PTr1 is turned on, the transistor Q1 is turned off, the Q2 is turned on, a current flows between the relay drive wires B1 and B2, and the normally closed contact relay RY is opened. The AC power supply at the output terminal AC_2 is cut off, and the protection target device is protected.

Current from the battery BAT is supplied to the relay drive wiring B1, but when the battery voltage decreases due to discharge, this is detected by the comparator IC2, and the transistor Q3 is turned on. When the transistor Q3 is turned on, the current from the power supply line V + of the switching power supply 7 is supplied to the relay drive wiring B1, and the contact of the relay RY is held in the open state.

The discharged battery BAT is charged by the charge control circuit 6. When the battery BAT is charged and the voltage rises, the comparator IC2 detects the voltage rise and turns off the transistor Q3. When the transistor Q3 is turned off, the current from the switching power supply 7 is cut off, and the contact of the relay RY is held open by the current from the battery BAT.

When the input terminal AC_IN and the AC power supply are shut off, for example, by removing the plug from the outlet, the current between the cathode K and the anode A of the shunt regulator IC1 of the input state detection unit 2 is shut off, and the LED 1 is turned off. When the LED 1 is turned off, the transistor Q1 is turned on, the Q2 is turned off, the current supply to the relay RY is cut off, and the contact of the relay RY returns to the closed state. Until then, the battery BAT or the switching power supply 7 maintains the open state of the contact of the relay RY.

In addition, when the overvoltage is temporarily exceeded due to the voltage fluctuation of the AC power supply, the relay RY is opened by the same operation as described above, and the device to be protected is protected, but the voltage of the AC power supply is normal. In the case of returning to, the contact of the relay RY returns to the closed state, and AC power is supplied again to the protection target device.

DESCRIPTION OF SYMBOLS 1 Overvoltage protection apparatus 2 Input state detection part 3 Relay drive circuit 4 Battery voltage detection part 5 Lithium ion battery pack 6 Charge control circuit 7 Switching power supply 8 Line filter AC_IN AC power supply input terminal AC_OUT AC power supply output terminal BAT Lithium ion battery IC1 Shunt regulator IC2 Comparator IC3 Charge control IC
IC4 IC for switching power supply
IC5 Shunt Regulator L1 Wiring L2 Wiring RY Normally Closed Contact Relay PC1 Photocoupler PC2 Photocoupler

Claims (2)

AC power input,
The output terminal of the AC power supply connected to the device to be protected;
Wiring connecting the input end and the output end;
A normally closed contact relay provided in the wiring;
An input state detection unit connected to the wiring and detecting an overvoltage of the AC power supply;
A relay driving circuit coupled to the input state detection unit in an electrically insulated state and driving the relay;
A battery for supplying power to the drive circuit;
When an overvoltage is detected by the input state detection unit, the relay drive circuit is driven to release the contact of the relay, and the relay drive circuit holds the contact of the relay in a released state by battery power. Features overvoltage protection device. The overvoltage protection device according to claim 1,
A switching power supply connected to the wiring;
A charge control circuit connected to the switching power supply for charging the battery;
An overvoltage protection device comprising: a battery voltage detection unit that detects a voltage of the battery and drives the relay with a current from the switching power supply when the battery voltage is equal to or lower than a predetermined value.

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