D.C. Voltage conversion electric appliance

Abstract

In the DC voltage conversion circuit of the feedback type structure, the switching frequency is increased in frequency and the electrical efficiency is improved at the same time. Control is carried out so that the switching element (11) provided in the primary side of the transformer (10) constituting the direct current voltage conversion circuit (15) becomes a conduction period, the transformer (10) stores energy, and the energy is stored during the off period of the switching element. The energy is output from the secondary winding (10s), and at the same time when the output of the energy from the secondary winding (10s) is completed, the switching element (11) is brought into a conduction state. Therefore, the time from when the secondary side current Is of the transformer (10) becomes zero to when the primary side Ip of the transformer starts to flow is detected, and the switching frequency is changed by the control unit (16), so that the time is shortened.

Description

technical field [0001] The invention relates to a technique for improving circuit efficiency and reducing cost in a feedback DC voltage conversion circuit. Background technique [0002] Various configurations are known for a DC voltage conversion circuit (so-called DC-DC converter) that converts a DC input voltage into a desired DC voltage. [0003] For example, in an application to an ignition circuit of a discharge lamp (metal halide lamp, etc.), a feedback type structure can be cited as a DC-DC conversion circuit for converting a DC input voltage from a DC power supply into a desired DC voltage. That is, a structure is provided in which a semiconductor switching element is connected to the primary winding side of a conversion transformer to perform on / off control of the element, and a rectifying diode and a smoothing capacitor are provided on the secondary side of the transformer. [0004] As far as the operation of the feedback type circuit is concerned, for example, in...

AI Technical Summary

Problems solved by technology

[0006] First, when focusing on the power loss during the reverse recovery time of the rectifier diode provided on the secondary side of the transformer, the switching element is in the on state while the current flows into the diode, and the diode is in the reverse bias state. Power loss during recovery time

Also, the total amount of losses in the diode's reverse recovery time is proportional to the switching frequency, so in current continuous mode, the higher the frequency, the greater the power loss

[0007] In addition, when the switching element is turned on, the primary current of the transformer is generated, so the switching loss of the element occurs

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