DC power supply apparatus

Abstract

The DC power supply of the invention is provided with conduction detecting circuits (17, 18) for outputting detected signals VP1, VP2during the conduction of rectifying MOS-FETs (15, 16), and timing circuits (19, 20) connected to the conduction detecting circuits (17, 18). The timing circuits (19, 20) measure the output periods of the detected signals VP1, VP2from the conduction detecting circuits (17, 18), until a current ID1flowing in the rectifying MOS-FET (15) becomes zero, turn off the rectifying MOS-FET (16) at a time, immediately before the measured period is ended, and surely turn off the rectifying MOS-FETs (15, 16) within a conduction period of a rectifying circuit. Accordingly, efficient and synchronous rectification can be conducted.

Description

technical field [0001] The invention relates to a DC power supply device such as a switching power supply, in particular to a DC power supply device capable of efficiently performing synchronous rectification. Background technique [0002] The DC power supply device of the current resonance type (SMZ method) is well known as a DC power supply device with high efficiency and low switching noise. For example, Figure 20 The present current resonant DC power supply unit shown has: [0003] The main MOS-FETs (2, 3) are connected in series to the DC power supply (1) as a pair of switching elements; [0004] A circuit and a voltage resonance capacitor (7) are connected in series, a resonance reactance (4) connected in parallel with one main MOS-FET (2), a primary winding (5a) of a transformer (5), and a current resonance capacitor ( 6); [0005] The first secondary winding (5b) of the transformer (5); [0006] the second secondary winding (5c), which has the same number of tur...

AI Technical Summary

Problems solved by technology

Therefore, for example, by using a current detection unit provided in the secondary side circuit to detect the current flowing from the transformer into the rectification switching element on the secondary side, when the current stops flowing, the rectification switching element can be turned off immediately, However, in this case, there is a problem that a loss occurs in the current detection part, and the conversion efficiency is low.

In particular, in the current resonance type switching power supply of Patent Document 1, since a choke coil is inserted into the secondary side circuit through which a large current flows, the size of the device is increased, and the conversion efficiency due to power loss in the choke coil low problem

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