STEP-DOWN SWITCHING REGULATOR, ITS CONTROL CIRCUIT, AND ELECTRONIC EQUIPMENT EMPLOYING IT

PROBLEM TO BE SOLVED: To provide the control circuit of a step-down switching regulator which can be protected by detecting overcurrent state. SOLUTION: A driver circuit 10 produces first and second gate voltages Vg1 and Vg2 to be applied on the gates of a switching transistor M1 and a synchronous rectification transistor M2 based on a pulse width modulation signal Vpwm subjected to duty ratio control such that the output voltage Vout from a switching regulator approaches a predetermined reference voltage. A comparing section 30 compares the voltage ΔV across the switching transistor M1 with a predetermined threshold voltage Vth and outputs a comparison signal of predetermined level when the voltage ΔV across the switching transistor M1 exceeds the threshold voltage Vth. A latch circuit 40 latches a comparison signal Vcmp outputted from the comparing section 30. The driver circuit 10 turns the switching transistor M1 off forcibly during a period when the comparison signal Vcmp is latched to high level at the latch circuit 40. COPYRIGHT: (C)2007,JPO&INPIT