MOTOR DRIVE CIRCUIT, DRIVE CIRCUIT BUILT-IN MOTOR WITH THE SAME INCORPORATED THEREIN, DRIVE CIRCUIT BUILT-IB PUMP MOTOR, AIR CONDITIONER WITH THE SAME MOUNTED THEREIN, VENTILATOR, HEAT PUMP HOT-WATER HEATER, AND BUILT-IN COLD/HOT WATER CIRCULATION TYPE AIR CONDITIONER

摘要

PROBLEM TO BE SOLVED: To provide a motor drive circuit capable of reducing a conduction loss regardless of a state of a load during operation, a drive circuit built-in motor with the same incorporated therein, a drive circuit built-in pump motor, an air conditioner with the same mounted therein, a ventilator, a heat pump hot-water heater, and a built-in cold/hot water circulation type air conditioner.SOLUTION: The motor drive circuit comprises: an inverter circuit 18 in which upper-stage-side switching elements 12-14 and lower-stage-side switching elements 15-17 are bridge-connected; and a gate signal generation part 6 in which, when generating a gate signal of the inverter circuit 18, during OFF periods of the upper-stage-side switching elements 12-14, synchronous rectification is performed for controlling ON of the lower-stage-side switching elements 15-17 synchronously to the timing in which a reflux current flows, under a condition satisfying a relation of IVf/Ron when the reflux current flowing through the lower-stage-side switching elements 15-17 is defined as I, a forward voltage of a parasitic diode is defined as Vf and ON resistance of a MOSFET is defined as Ron.SELECTED DRAWING: Figure 1