A circuit for realizing switch changeover with zero-voltage switch power

Abstract

The invention advances a new method of realizing the zero-voltage-switching (ZVS) transition of a switch by unidirectional charge and discharge of an absorption capacitance and its control method. An absorption capacitance as well as other components composes a double end network, making the absorption capacitance work in a unidirectional charge-discharge state, i.e. the absorption capacitance makes charge and discharge at a top-positive and bottom-negative unidirectional voltage, and thus providing a condition for a switch tube to realize ZVS transition. The double end network cooperates with some components to largely reduce the variation rates of voltage waveform of a drain of the switch tube and current waveform of a transformer, radically reducing EMI, and also providing a full condition for the secondary side to adopt a simple circuit so as to realize synchronous rectification. It can by a large margin increase SPS converting efficiency and reduces the EMI, and can reduce the cost of SPS and realize a small-sized high-frequency SPS.

Description

(1) Technical field: [0001] The invention relates to a new circuit design for realizing zero-voltage switch conversion of switching power supply, which is realized by adopting one-way charging and discharging of absorbing capacitor and its control circuit. (two) background technology: [0002] Switching power supply (SPS) represents the development direction of DC power supply, has been widely used in all aspects of production and life, and is currently developing towards high frequency, high efficiency, miniaturization and better electromagnetic compatibility (EMC) effects. In order to meet the above requirements, zero-voltage switching (ZVS), zero-current switching (ZCS), the so-called resonant soft switching technology, and synchronous rectification technology in which field effect transistors replace diodes have become effective means. However, the current soft-switching technology and synchronous rectification technology have complex circuit structures, are difficult to...

AI Technical Summary

Problems solved by technology

Q 1 Rapidly changing Vd and i at turn-on and turn-off 1 i 2 The waveform is the direct cause of EMI, which increases the cost of SPS in terms of EMC and limits the scope of use of SPS; at the same time, it also increases the complexity of the secondary synchronous rectification circuit and reduces the reliability, making synchronous rectification technology unsuitable. Reality

These shortcomings prevent SPS from further improving operating frequency and efficiency, reducing volume, and reducing EMI

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