| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching regulator which ensures switching with a stabilized Duty for all input voltages and output voltages. SOLUTION: The semiconductor device employing a switching regulator comprises an error amplifier 3 consisting of a diode 9, a capacitor 12, a choke coil 11 and a switching element 8 being turned on/off by a PWM controlled pulse and amplifying the differential voltage between an output voltage divided by resistor division circuits 2a, 2b and a reference voltage 1, a sense resistor 10 for detecting a current flowing through the choke coil 11, a comparator 4 for comparing output signals from the amplifier 3 and the sense resistor 10, oscillators 15-17 for varying the ON interval of oscillator based on the time ratio (Duty) of on/off period of the switching element 8, an SR latch circuit 5 for generating a switching control signal 19 from a pulse signal generated from the oscillator and the output signal from the comparator 4, and an output control circuit 6 consisting of a plurality of logic circuits wherein an oscillator select circuit 18 generates a pulse of short ON time when the switching Duty is small and generates a pulse of long ON time when the switching Duty is large. COPYRIGHT: (C)2007,JPO&INPIT
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