Load open state detection using h-bridge driving circuit

Abstract

A load open state detection circuit includes a driver having X and Y terminals between which an inductive load is connected and which receive drive signals, a first transistor whose base is connected to the X terminal and whose collector is connected to a terminal supplied with a predetermined voltage, a second transistor whose base is connected to the Y terminal and whose collector is connected to the terminal supplied with a predetermined voltage and third and fourth transistors having bases thereof connected to input terminals supplied with respective drive signals. A fifth transistor has a base connected to the base of the first transistor, a collector connected to a resistor which is in turn connected to the collector of the first transistor, and an emitter connected to a second resistor which is connected to the emitter of the first transistor. A sixth transistor is provided, having a base connected to the base of the fourth transistor and a collector and emitter connected through respective resistors to the collector and emitter of the fourth transistor, respectively. A logic gate circuit receives voltages of the collectors of the fifth and sixth transistors to determine whether or not a load current flows between X and Y terminals to thereby detect whether the load is in a normal or an open state.