Patent ID: 9660634
Date: 2017-05-23
CPC Classifications: H03K

Claim:
1. A load driving circuit, which controls power supply to a load connected to an output terminal by using a main power supply voltage supplied between two power supply nodes and a sub-power supply voltage generated from the main power supply voltage by a sub-power supply circuit, the load driving circuit comprising: an output transistor having a control terminal and two power supply terminals, which are connected to one power supply node of the two power supply nodes and the output terminal; a pre-driver circuit for applying a control signal corresponding to an input signal to the control terminal of the output transistor at normal time; and a malfunction prevention circuit including a simplified power supply circuit, which is provided at least partly in a power supply path connected in series with either one of the two power supply terminals of the output transistor, and which is activated in response to power supply to the two power supply terminals of the output transistor at activation time and earlier than activation of the sub-power supply voltage of the sub-power supply circuit by using the main power supply voltage at the activation time, wherein the malfunction prevention circuit sets the control terminal of the output transistor to a predetermined voltage, which turns off the output transistor, by using an output voltage generated by the simplified power supply circuit, and wherein the malfunction prevention circuit invalidates the predetermined voltage set at the control terminal of the output transistor, when the sub-power supply voltage of the sub-power supply circuit changes from a pre-activation voltage to a normal operation assurance voltage, which assures a normal operation of an entirety of the load driving circuit, after setting of the predetermined voltage at the control terminal of the output transistor.