JP2007005086A - Rush current prevention circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rush current prevention circuit with a simple circuit structure of which a bypass circuit is free from false operation due to noise. <P>SOLUTION: The bypass circuit one 2 is structured of a resistor 9 and a photo coupler PC connected in series with it and is connected to a relay Ry1. Diodes D4 for reverse flow prevention are connected to either end of a relay Ry2 connected in parallel with the relay Ry1. The bypass circuit two 3 has a capacitor C8 and a resistor R11 structured for noise removal serially connected, with these and a thyristor SCR connected in parallel. A gate of the thyristor SCR is connected to a capacitor C9, and the capacitor C9 connected to the gate of the thyristor SCR, the resistor R11, a capacitor C6, and a contact switch ry2 are connected in parallel. Then, a resistor R8, the photo coupler PC, and these circuits (the capacitor C9, the resistor R10, the capacitor C6, and the contact switch ry2) are connected in series sequentially from a positive side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inrush current prevention circuit for protecting a relay from an inrush current generated when a power source for driving a load is turned on.

  Conventionally, when a power source for driving a load represented by a fluorescent lamp and a motor is turned on, a circuit is provided to drive the relay and supply the power source to the load by turning on a switch.

For example, a circuit using a fluorescent lamp 120 as a load is shown as follows.
In the conventional fluorescent lamp circuit 100 shown in FIG. 4, when the switch SW in the dimming side circuit unit 110 is closed, the voltage of the battery 140 is applied to the inverter circuit 130 in the lamp side circuit unit 105 as a power source of the fluorescent lamp 120. The fluorescent lamps 120 of the plurality of lamp-side circuit units 105 that are applied and connected in parallel are turned on. The inverter circuit 130 of the fluorescent lamp 120 is provided with a smoothing capacitor for stabilizing the power supply with respect to the input voltage. When the switch SW is closed, the relay Ry operates, and the relay Ry When the contact switch ry is closed, a large current (so-called inrush current) passes through the contact switch ry in order to pass a current through the fluorescent lamp 120 connected to the dimming circuit 104.

Then, due to the inrush current passing through the contact switch ry, a current exceeding the capacity that the contact switch ry can withstand flows, the surface of the contact switch ry becomes over, causing heat generation, and consequently failure of the fluorescent lamp circuit 100. It was a problem of being connected.
Therefore, in order to avoid an inrush current flowing through the relay when a power source for driving the load is turned on, a circuit that prevents an inrush current by providing a bypass circuit connected in parallel with the relay has been considered.

  For example, as described in Patent Document 1, when the power is turned on and the load is driven, a bypass circuit connected in parallel with the relay is provided in order to avoid an inrush current flowing through the relay. Thyristors are used. In this circuit, due to the difference between the mechanical operation of the relay and the electronic operation of the thyristor, the electronic operation is first activated earlier, and after the inrush current flows through the thyristor, the current related to the load flows through the electromagnetic relay. In this way, contact welding is prevented by bypassing the inrush current flowing through the relay to the thyristor and avoiding it.

JP 2004-111240 A (FIGS. 4 and 5)

However, this conventional inrush current prevention circuit has the following problems.
In the conventional inrush current prevention circuit, the gate for turning on the thyristor is susceptible to noise and may malfunction. Further, in order to prevent the influence of these noises, it is necessary to configure an extra complicated circuit such as a delay circuit or a synchronous circuit.

  Therefore, the present invention provides a bypass circuit for preventing inrush current from flowing to the contact switch for applying power to the load, so that the bypass circuit does not malfunction due to the influence of noise, and the noise An object of the present invention is to provide an inrush current prevention circuit that prevents an inrush current with a simple circuit configuration without providing a complicated circuit for avoiding the above.

  In order to solve the above-mentioned problem, the inrush current prevention circuit (1) according to claim 1 supplies a current to the load by the operation of the relay (Ry1) and the operation of the relay (Ry1). In an inrush current prevention circuit provided with a contact switch (ry1) to be connected and a bypass circuit connected in parallel with the contact switch (ry1) and allowing the current to pass through the contact switch (ry1). The bypass circuit (2, 3) has a faster response speed than the contact switch (ry1), and the contact is always closed, and the bypass relay (Ry2) is activated by the operation of the switch (SW) and the contact is made. An open bypass contact switch (ry2) and a thyristor (SCR) for passing the current are provided, and the bypass contact switch (ry2) and the cycle switch are provided. It is characterized in that by connecting the gate of the static (SCR).

  The inrush current prevention circuit (1) according to claim 2, wherein the bypass circuit (2, 3) is provided with a photocoupler (PC) driven by operation of the switch (SW), and the photocoupler (PC) and the A thyristor (SCR) gate is connected.

  In the inrush current prevention circuit according to the first aspect of the present invention, the bypass contact switch is configured with the b contact so that the contact is always closed, noise applied to the gate of the thyristor can be removed, and no malfunction occurs. Further, by utilizing the operating characteristics of the relay, it is not necessary to have a special circuit configuration, and a simple circuit configuration can be configured with general parts.

  Since the inrush current prevention circuit according to the second aspect uses a photocoupler to turn on the thyristor and is always insulated, it can be hardly affected by noise.

The present embodiment will be described below based on FIGS. 1 to 3.
FIG. 1 is an overall schematic diagram of an inrush current prevention circuit 1 mounted on a vehicle. FIG. 2 is a schematic diagram illustrating an example when the lamp-side circuit unit 5 and the dimming-side circuit unit 10 of the inrush current prevention circuit 1 of the present embodiment are connected. FIG. 3 is a circuit diagram showing the dimming side circuit unit 10 of the inrush current prevention circuit 1 of the present embodiment.

As shown in FIG. 1 or FIG. 2, an inrush current prevention circuit 1 for controlling lighting mounted on a vehicle includes a battery 40 as a power source mounted on the vehicle, and a dimming side connected to the battery 40. The light control side circuit unit 10 is connected in parallel with the plurality of lamp side circuit units 5.
The lamp side circuit unit 5 includes a fluorescent lamp 20 for lighting a vehicle and an inverter circuit 30 for converting a DC power source into an AC power source. The fluorescent lamp 20 is connected to the inverter circuit 30.

The dimming side circuit unit 10 is roughly divided into the following configurations.
The dimming side circuit unit 10 includes a contact switch ry1 connected in series to the positive side of the battery 40, a bypass 2 circuit 3 connected in parallel to the contact switch ry1, and a dimming connected in parallel to the battery 40. The circuit 4 is composed of a relay 1, a relay 2 and a bypass 1 circuit 2 connected in parallel, and a switch SW for turning on the fluorescent lamp 20.

Furthermore, each structure of the light control side circuit part 10 is explained in full detail below based on the circuit diagram shown in FIG.
The switch SW is configured by a switch function mounted on the function of the volume resistor VR described later. For example, the switch SW is turned on by rotating a volume knob.

  The contact switch ry1 that is activated by the operation of the relay Ry1 is called a contact (normally open contact), and has a structure in which the contact is normally opened and the contact is closed by applying a voltage to the coil of the relay Ry1. Conversely, the contact switch ry2 that is activated by the operation of the relay Ry2 is called a b contact (normally closed contact) and has a structure in which the contact is normally closed and the contact is opened by applying a voltage to the coil of the relay Ry1. ing.

  A surge absorber ZNR for absorbing surge is connected in parallel to the battery 40 at one end of the contact switch ry1, and a capacitor C7 for removing noise is also connected in parallel. The other end of the contact switch ry1 is connected to the dimming circuit 4 via a diode D7.

  The bypass 1 circuit 2 includes a resistor R9 and a photocoupler PC connected in series, and is connected to the relay Ry1. A backflow prevention diode D4 is connected to both ends of the relay Ry2 connected in parallel with the relay Ry1.

  In the bypass 2 circuit 3, a resistor R11 and a capacitor C8 configured for noise removal are connected in series, and these and a thyristor SCR are connected in parallel. The gate of the thyristor SCR is connected to the capacitor C9, and the capacitor C9, the resistor R11, the capacitor C6, and the contact switch ry2 connected to the gate of the thyristor SCR are connected in parallel. The resistor R8, the photocoupler PC, and these circuits (capacitor C9, resistor R10, capacitor C6, contact switch ry2) are connected in series in this order from the plus side.

One of the light control circuits 4 is connected to the inverter circuit unit 30 of the lamp side circuit unit 5, and the other end is connected to the negative side of the battery 40.
The resistor R1 in the dimming circuit 4 has one end connected to the plus side and the other end connected to the cathode of the Zener diode ZD. The anode of the Zener diode ZD is connected to the negative side of the battery, and the electrolytic capacitor C1 is connected in parallel with the Zener diode ZD. An IC 6 is connected in parallel with the Zener diode ZD and the electrolytic capacitor C1.

  And the 7th terminal of IC6 and resistance R2 are connected, and are connected to the variable terminal of volume resistance VR. The second terminal of the IC 6 is connected to the variable resistance side of the volume resistor VR, and both ends thereof are connected to the cathode of the diode D2 for backflow prevention and the anode of the diode D3. A capacitor C2 is connected between the second terminal and the diode D3, and the other end of the capacitor C2 is connected to the negative side of the battery 40. A capacitor C5 is connected to the fifth terminal of the IC6, and the other end of the capacitor C5 is connected to the negative side of the battery 40.

Further, the third terminal of the IC 6 and the resistor R3 are connected, and the other end of the resistor R3 is connected to the base of the transistor Tr. The collector of the transistor Tr is connected to the positive side of the battery 40 via the resistor R4. The emitter of the transistor Tr is connected to the ground point (G), and a resistor R5 connected to the negative side of the battery 40 and a capacitor C4 connected in series with the resistor R are connected in parallel between them.

  The volume resistor VR described above has a variable resistance value, and is provided with a rotary knob that can change the resistance value. When the volume resistance VR exceeds a certain rotation range, it functions as a switch and rotates further. The resistance value varies with the range of rotation.

(Operation and effect of this embodiment)
Hereinafter, the operation and effect of this embodiment will be described.
When the switch SW is operated and the switch SW is closed to turn on the fluorescent lamp 20 (load) for illumination, a current flows through the photocoupler PC in the bypass 1 circuit 2, and at the same time, the contact switch is operated by the operation of the relay Ry2. ry2 is opened. Then, a current flows through the photocoupler PC in the bypass 2 circuit 3, the gate of the thyristor SCR is turned on, and an inrush current flows through the thyristor SCR.

  The relay Ry1 starts to operate simultaneously with the relay Ry2, but the relay Ry1 has an a contact, the contact switch ry1 is always opened, and the contact switch ry1 is closed when operated. On the other hand, the relay Ry2 is a b contact, and the contact switch ry1 is always closed and when operated, the contact switch ry1 opens. The difference between these operations is that the closing operation is generally slower than the opening operation of the contact switch. By utilizing this characteristic, an inrush current is allowed to flow through the thyristor SCR of the bypass 1 circuit. After avoiding a large inrush current, the contact switch ry1 that has been operated late is closed and a current flows, and the power of the battery 40 can be supplied to the lamp side circuit unit 5.

  Therefore, when the power is turned on by operating the switch SW, an inrush current flows to the thyristor SCR of the bypass 1 circuit 2, and then a current flows to the contact switch ry1. The contact switch ry1 does not pass through, the surface of the contact switch ry1 is not damaged, and no heat is generated.

By using an insulating photocoupler PC for driving the thyristor SCR, the current passes only when the current passes and is constantly insulated, so that it is hardly affected by noise.
The contact switch ry2 has a function of removing noise applied to the gate of the thyristor SCR by always closing the contact by adopting the b contact and escaping noise applied to the gate of the thyristor SCR from the contact switch ry2. .
By utilizing the difference in the operation characteristics of the relays (Ry1, ry1, Ry2, ry2), a circuit configuration with general parts is possible without using a special circuit configuration, and it can be created with a simple circuit configuration. I can do it.

  Next, the dimming circuit 4 changes the current value by changing the duty ratio of the rectangular wave generated by the transistor Tr by controlling the voltage by the IC 6 by changing the resistance value of the volume resistor VR, so that the lamp side circuit unit It is possible to adjust the brightness of the illumination of the fluorescent lamp 20 in three stages: bright, medium and dark.

(Examples of changes to other embodiments)
The example which changed embodiment described above into other embodiment is shown below.
In the above-described embodiment, the volume resistance VR is described as a three-stage type of light, medium, and dark, but may be a stepless type.

In the above embodiment, the switch SW having a switch for the volume resistor VR is used. However, the switch SW and the volume resistor VR may be separated, and the switch SW may be provided individually.

In the above embodiment, the power source is constituted by a DC power source, but may be an AC power source.

In the above embodiment, a fluorescent lamp is used as a load. However, a load such as a motor, a solenoid, an incandescent lamp, or a heater may be used.

(Application example of this embodiment)
As an example of application of the present embodiment described above, the inrush current prevention circuit 1 used in a vehicle has been described. However, when supplying a current to a load by a relay, any circuit that prevents an inrush current can be used in other fields. Can also be applied.

1 is an overall schematic diagram of an inrush current prevention circuit 1 of the present embodiment. It is the schematic which shows an example when the lamp side circuit part 5 and the light control side circuit part 10 of the inrush current prevention circuit 1 of this embodiment are connected. It is a circuit diagram which shows the light control side circuit part 10 of the inrush current prevention circuit 1 of this embodiment. It is the schematic which shows an example when the lamp side circuit part 105 and the light control side circuit part 110 of the conventional fluorescent lamp circuit 100 are connected.

Explanation of symbols

R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11... Resistor, C1.
C2, C3, C4, C5, C6, C7, C8, C9 ... capacitors,
D1, D2, D3, D4 ... diode, ZD ... zener diode,
ZNR: Surge absorber, PC: Photocoupler,
SCR ... Thyristor, Ry, Ry1, Ry2 ... Relay,
ry, ry1, ry2 ... contact switch, SW ... switch,
VR: Volume resistance,
1 ... Inrush current prevention circuit, 2 ... Bypass 1 circuit,
3 ... Bypass 2 circuit 4,104 ... Dimming circuit,
5, 105 ... Lamp side circuit part, 6 ... IC, 10, 110 ... Dimming side circuit part,
20, 120 ... fluorescent lamp (load), 30, 130 ... inverter circuit,
40, 140 ... battery, 100 ... fluorescent lamp circuit.

Claims (2)

A relay that operates by operating the switch;
A contact switch for supplying current to the load by the operation of the relay;
A bypass circuit connected in parallel with the contact switch and passing the current through the contact switch;
In the inrush current prevention circuit provided with
The bypass circuit has a response speed higher than that of the contact switch, and the contact is always closed, and a bypass relay is activated by the operation of the switch to open the contact,
A thyristor for passing the current,
An inrush current prevention circuit, wherein the bypass contact switch and the gate of the thyristor are connected. The bypass circuit includes a photocoupler that is driven by operating the switch,
2. The inrush current preventing circuit according to claim 1, wherein the photocoupler and a gate of the thyristor are connected.

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