摘要 |
PURPOSE:To easily detect the non-load state of large current load by a simple circuit, by detecting whether the large current load is in the non-load state on the basis of the output voltage waveform appearing at the load terminal of a semiconductive power circuit. CONSTITUTION:When the control signal from MPU is inputted to a signal input terminal 10, a drive circuit 11 drives an output stage semiconductive element 12 through a switch. The voltage waveform appearing at the output terminal 14 of the semiconductive element 12 is the same as the input waveform of the semiconductive element at the time of normal load but, at the time of non-load when load 15 is separated by disconnection, said voltage shows gentle change at the OFF-time of the semiconductive element 12. A non-load detection circuit 16 detects the change in the output waveform of said element 12 using an emitter follower 20, an inverter 21 and a NOR gate 22. By this method, as compared with a conventional one wherein a detection resistor is inserted in a load current route, the loss of power required in detection can be reduced and, therefore, the non-load state of large current load can be easily detected.
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