The feedback control method and the control method of the asymmetrical half-bridge flyback converter based on this method and the realization circuit of the two methods

Abstract

The invention aims to realize that a control mode of primary side feedback is added into an asymmetric half bridge type flyback converter in a non-complementary DCM mode. For the asymmetric half bridge type flyback converter working in the non-complementary DCM mode, primary side inductance is released and is not clamped by an output end at the moment of finishing primary side excitation energy resetting. At the time, the primary side inductance, resonant capacitance, leakage inductance, and parasitic capacitance between the drain and the source of an MOS transistor start resonance oscillation; and at the moment of oscillation starting, a voltage between the drain and the source of the MOS transistor forms an "inflection point", voltages on two ends of the primary side inductance reflect voltage changes of the output end, voltages ontwo ends of an auxiliary winding have similar changes, an oscillation starting direction is just opposite to the direction of the voltages on the two ends of the primary side inductance due to a dotted terminal winding relationship, and if the inflection point is detected through the auxiliary winding and inflection point information is transmitted to a controller, the detection and control of an output voltage can be realized. Compared with the prior art, relatively high output voltage precision, linear adjustment rate and load adjustment rate of the converter can be ensured; and meanwhile, zero voltage switching (ZVS) of a primary side switch tube can be realized, the working frequency of the converter can be increased, the efficiency of the converter can be improved, and the volume of a complete machine is reduced.

Description

technical field [0001] The invention belongs to a switch converter of an electric energy conversion device, in particular to an asymmetrical half-bridge flyback converter and its feedback control technology. Background technique [0002] With the development of science and technology, some power supplies require adjustable charging current and output voltage. When accurate output voltage is required, secondary side feedback (commonly used optocoupler + TL431 feedback and control method) is used, that is, output feedback, which is equivalent to A current detection circuit is added on the secondary side. This solution can guarantee high output voltage accuracy, but the product design is difficult, the cost is high, and the isolation withstand voltage strength is low, so the disadvantages are obvious. [0003] In recent years, electronic devices such as smartphones and IPADs that integrate entertainment and communication functions have become popular all over the world. This ...

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Problems solved by technology

[0006] In order to achieve a high isolation withstand voltage between the input and output, the existing IGBT drive power supply mostly adopts an open-loop scheme, and the most direct disadvantages of the open-loop scheme include: high output voltage at no-load, poor load regulation; output voltage Varies with input voltage, poor line voltage regulation

[0007] Other driving power schemes include two-stage architecture, the first stage realizes isolation and step-down, and the second stage realizes voltage regulation. This scheme can achieve higher isolation withstand voltage level, good line voltage regulation rate, and higher output voltage Accuracy, but the disadvantages of this solution are also obvious, the solution is complex, the design is difficult; the number of components is large, and the cost is unacceptable

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