DC-to-DC CONVERTER

摘要

PROBLEM TO BE SOLVED: To provide a DC-to-DC converter which is applicable to a wide range of input voltage and controls wide ranges of output voltage and output power and is highly efficient and of small size. SOLUTION: Switching elements Q1 and Q2 are on/off-controlled by a controlling means not shown. The controlling means is so constituted as to be capable of controlling both the switching frequency and duty of the switching elements Q1 and Q2. A resonance circuit is composed of a choke coil L1, the leakage inductance of a transformer T, and a capacitor C21 (or C22). The controlling means is provided with two control modes for the switching elements Q1 and Q2: second mode in which the on-durations of Q1 and Q2 do not overlap and the switching elements are alternately turned on and off at a frequency close to the resonance frequency of the resonance circuit and first mode in which the duty is increased to a value higher than 50% when the switching elements Q1 and Q2 are alternately turned on and there is a duration when both the switching elements Q1 and Q2 are simultaneously on.