| 摘要 |
PURPOSE: A boost-up DC-DC converter is provided to improve efficiency by using a pulse frequency modulation in a light load and a pulse width modulation in a heavy load. CONSTITUTION: A boost-up DC-DC converter comprises an inductor(L) connected between a power voltage(V+) and the first node(Nd1); a diode(D) connected between the first node and an output terminal; a capacitor(C) connected between the diode and the output terminal; an NMOS transistor(Q) connected between the inductor and a ground; an amplifier for comparing and amplifying the voltage fed back from the output terminal and input to a negative terminal and the second reference voltage(Vref2) input to a positive terminal; and a comparing and pulse width modulation voltage generating unit(120) for comparing an output(Verr) of the amplifier, the first and third reference voltages(Vref1,Vref3), and a pulse signal of a ramp oscillator(110), generating a pulse width modulation voltage, and outputting the generated voltage to the NMOS transistor.
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