JPS6264256A - Relay driving circuit - Google Patents

Abstract

PURPOSE:To reduce loss due to rush current, by changing the first driving voltage applied to a relay driving coil on making and breaking a relay contact, over to the second voltage obtainable from stabilizing the first voltage after the completion of making and breaking the relay contact. CONSTITUTION:By turning a power source switch 2 ON, at the moment when the voltage of the input power source 1 of a DC-DC converter is applied, relay contacts 16, 17 are ON, and the value of the power source voltage 1 divided with resistances 5, 6 is applied to the coil 11 of a relay, delayed by the time constant of a voltage-dividing resistance 5 and a condenser 10. When current through the coil 11 exceeds the lowest working current, then the contacts 16, 18 are turned ON, and the relay through the power source 1 is not energized, but the relay is self-retained, and voltage is fed from a voltage source 13 on the output side of the stabilized DC-DC converter, and the relay is retained in a working state with little current. As a result, even if the input voltage of the DC-DC converter is extremely changed, the loss of a rush-current-proof circuit can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an inrush current prevention circuit often used in DC-DC converter circuits, and more particularly to a relay drive circuit in an inrush current prevention circuit using a relay.

Conventional inrush and current prevention circuits using relays used in DC-DC converter circuits, as shown in FIG. (, - By dividing the input voltage of the DC converter by the resistor 22 and the Zener diode 24, the transistor 25 is controlled (2Il voltage is obtained and the transistor is controlled, and the relay connected to the collector of the transistor 25 A circuit configuration in which the relay contacts (armature contact 16, break contact 17 and meter contact 18) are opened and closed by passing current through the drive coil 11, and the function as an inrush current prevention circuit is obtained by the action of the inrush current limiting resistor 3. It had become.

In the inrush current prevention circuit using the conventional relay described above,
Since both the bias voltage of the transistor 25 and the drive voltage of the drive coil 11 of the relay are supplied from the input voltage of the DC-DC converter, if the input voltage has a wide fluctuation range, the loss of the circuit becomes large at high input voltage. It has the disadvantage of becoming.

Purpose of the Invention The present invention has been made to eliminate the drawbacks of the conventional circuits described above, and provides a relay drive circuit in which the circuit loss is almost independent of changes in input voltage and is constant even when the input voltage changes significantly. The purpose is to provide dimensions.

Structure of the Invention The relay drive circuit according to the present invention applies a drive voltage based on a first DC voltage to the relay drive coil when the relay contacts are opened and closed, and stabilizes the first DC voltage after the relay contacts are opened and closed. The configuration is such that switching is performed to supply drive voltages based on the second DC voltages obtained by converting the voltages.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and parts equivalent to those in FIG. 2 are designated by the same symbols. In FIG. 1, the output voltage (first DC voltage) of one voltage source 1 is used as the input voltage of a DC-DC converter (not shown), and the second voltage source 1
The output voltage (second DC voltage) of No. 3 is the stabilized output voltage of the DC, -DC converter. At the moment when the input voltage of the OC-OC converter is applied by turning on the power switch 2, the armature contact 16 and the break contact 17 side of the relay contact are electrically connected, and at this time, the output voltage of the DC-DC converter is not yet generated. Not yet.

Therefore, the voltage determined by the ratio of the voltage dividing resistors 5 and 6 is applied to the relay coil 11 in a time period determined by the time constant of the voltage dividing resistor 5 and the capacitor 10. input).

When the current flowing through the relay coil 11 exceeds the minimum current of the relay, the relay contacts conduct between the armature contact 16 and the make contact 18. At this time, the voltage applied to the coil 11 of the relay through the voltage dividing resistor 5 disappears, but once the relay operates, it does not require current for the driving time to maintain the operating state. It is possible to maintain the relay in an operating state by supplying voltage from the second voltage source 13. Since the second voltage source 13 is the output voltage of the DC-DC converter and is stabilized as described above, the current flowing through the relay drive circuit is constant regardless of input voltage fluctuations, and the current flowing through the relay drive circuit is constant regardless of input voltage fluctuations. There is no increase in the amount of power used. Furthermore, a second voltage source 13
It is sufficient that the current supplied is about half that of driving, and this can be determined by the value of the resistor 9, so it is possible to reduce loss in this aspect as well.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention can be applied to cases where the input voltage of the DC-DC converter changes greatly by switching between the drive voltage applied to the relay drive coil when the relay contacts are opened and closed and that when the relay contacts have completed opening and closing. Even if there is, the loss of the inrush current prevention circuit does not depend on the input voltage, so it is possible to configure a relay drive circuit with low loss even when the input voltage is high.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional example. Explanation of symbols of main parts 1...First voltage source 3...Rush current limiting resistor 5.6...Voltage dividing resistor 11...Relay Drive coil 13...Second voltage source

Claims (1)

[Claims] A relay drive circuit that outputs an applied first DC voltage through a contact, the first DC voltage being applied to a drive coil of the relay at a predetermined time constant when the first DC voltage is applied. and means for supplying a second DC voltage obtained by stabilizing the first DC voltage passed through the contacts of the relay to the drive coil of the relay. A relay drive circuit characterized by: