Patent ID: 7256562

Claim:
A control circuit for a cooling fan, comprising: a temperature detector for detecting temperature variation; a power controller for controlling driving power to the cooling fan; a proportional electric power block for supplying control power to the power controller in proportion to variation in temperature; and a fixed electric power block for supplying control power to the power controller at a fixed level when the detected temperature is lower than a predetermined temperature, wherein the fixed electric power block is provided between the proportional electric power block and the cooling fan, the fixed electrical power block comprising a first comparator for supplying power at a fixed level to the power controller on the basis of a predetermined offset input voltage, and wherein the temperature detector comprises a thermistor connected to an input power source and configured to detect variation in temperature, and a compensation resistor connected in series with the thermistor and configured to supply a compensation voltage according to the temperature variation, wherein the proportional electric power block is provided on a bypath between the input power and the power controller, and comprises a pair of voltage division resistors provided in parallel with the temperature detector and providing a predetermined standard voltage; and a second comparator for comparing the compensation voltage according to the temperature variation of the temperature detector and the standard voltage, and applying the control power proportional to a difference voltage according to a difference resulted from comparison to the power controller.