Patent ID: 7369392
Filing Date: 2008-05-06
Classification: H03K

Abstract:
1. A circuit for preventing simultaneous ON operations at a relay drive apparatus, which includes a first relay having a first drive unit receiving drive current through a first resistor from a power supply and a first switch device connected with a first signal line to be driven by the first drive unit, a second relay having a second drive unit receiving drive current through a second resistor from said power supply and a second switch device connected with a second signal line to be driven by the second drive unit, and a controller having a first control signal output terminal for outputting a control signal to control the first drive unit and a second control signal output terminal for outputting a control signal to control the second drive unit, comprising: a first diode; a second diode; a first transistor being connected through the first diode with the first drive unit for controlling ON/OFF operation by the control signal derived from the first control signal output terminal of the controller; a second transistor being connected through the second diode with the second drive unit for controlling ON/OFF operation by the control signal derived from the second control signal output terminal of the controller; a first junction point of the first resistor and the first drive unit; a second junction point of the second resistor and the second drive unit; a third junction point of the first diode and the first transistor; a fourth junction point of the second diode and the second transistor; a third diode, an anode of which is connected to the second junction point, a cathode of which is connected to the third junction point; and a fourth diode, an anode of which is connected to the first junction point, a cathode of which is connected to the fourth junction point.