Patent ID: 6525506
Filing Date: 2003-02-25
Classification: H02P

Abstract:
A current limit circuit of an inverter refrigerator, comprising:a power unit for providing a DC power source to a BLDC motor by being inputted an AC power: an excess current detecting unit for detecting current flowed into the BLDC motor; a control limit unit for outputting a current limit signal when an excess current is detected from the excess current detecting unit, wherein the current limit unit includes a first diode and a second diode connected in series between a power voltage node and ground in a reversely biased direction, a common connection node A is connected to one side of a capacitor having its other side grounded with a current detecting signal applied through a first resistance to the one side of the capacitor connected to the node A, the node A is connected to a non-inverting input terminal of a comparator through a second resistance, a third resistance is connected between ground and an inverting input terminal of the comparator, and an output terminal of the comparator is also connected to the inverting input terminal through a fourth resistance, the output terminal of the comparator is also connected to a base of a NPN transistor through a fifth resistance, and a collector of the NPN transistor is connected through a sixth resistance to the power voltage node, a seventh resistance is connected between a grounded emitter and the base of the NPN transistor, and the current limit signal is outputted from a collector side of the NPN transistor; a position/speed detector for detecting a position and speed of a rotator of the BLDC motor and outputting a detecting signal in accordance therewith; a microcomputer for outputting a pulse width modulation signal in accordance with the current limit signal from the current limit unit, and by judging the position and speed of the rotator from the detecting signal of the position/speed detector and comparing it with a request phase angle and phase difference, changing a duty cycle of the outputted pulse width modulation signal to an OFF state whenever the current limit signal indicates that an excess current condition has been detected; and a gate driving unit for controlling the operation of the power unit in accordance with the pulse width modulation signal from the microcomputer.