| 摘要 |
PURPOSE:To purify an electromagnetic relay contact simply by enforcing the coil of an electromagnetic relay for a short time and then releasing the enforcement, when the electromagnetic relay contact is connected to a power supply, and applying a current to one load for a short time while the contact is changed from the connecting condition to the unconnected condition. CONSTITUTION:A pulse generating circuit 16 enforces the coil 7 of an electromagnetic relay 5 which is connected to a power supply (IGN) turning a semiconductor switch 12 once into the ON condition for a short time, then releasing the enforcement of the coil 7 by turning OFF, and again turning to the ON condition to maintain constant enforcing condition, depending on the input signal from a power supply application watching circuit, by closing and opening a contact 6 a little later than the input of the signal, and closing it again. On the other hand, a signal input to a delay circuit 17 is input to a pulse generating circuit 18, and the ON signal is delivered to a semiconductor switch 131 to apply a current to a wound wire 31 for a short time. As a result, the contact surface is purified in a short time, and since the contact is purified every time the group of loads 3 are prepared to link to the power supply by the electromagnetic relay, the material of the contact can be selected easily.
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