Patent ID: 9526138
Filing Date: 2016-12-20
CPC Classification: G05F,H02J,H02M,H05B

Claim Text:
1. A load driving device comprising: a power supply circuit for supplying to a load an output voltage converted from an input voltage; a detection voltage generation circuit that is connected between the load and a ground, for generating a detection voltage that varies depending on a magnitude of a voltage drop across the load; and a control circuit for controlling the power supply circuit so that output feedback control of the output voltage is performed based on the detection voltage, wherein the detection voltage generation circuit includes a constant-current source connected in series with the load and flowing constant current that can be adjusted, the detection voltage generation circuit outputting a node voltage at a connection node between the load and the constant-current source as the detection voltage, the control circuit generates a control signal of the power supply circuit so that the detection voltage of a connecting point of the load and the constant-current source becomes a constant voltage, and the constant-current source includes: wherein the power supply circuit includes: an isolation transformer, the input voltage being applied to a primary side of the isolation transformer, and the output voltage being supplied from a secondary side of the isolation transformer to the load, and the power supply circuit feeds back, via a photocoupler to the primary side, a signal corresponding to the detection voltage, in order to control the output voltage according to an output signal of the photocoupler such that the node voltage remains constant.