Secondary side circuit for flyback power converter

Abstract

The invention relates to a secondary side circuit for a flyback power converter. The flyback power converter contains a capacitor and a secondary side coil of a transformer, wherein the capacitor is connected between an output end and a grounding end to supply output current; and the secondary side coil is used for supplying secondary side current to charge the capacitor. The invention is characterized in that the secondary side circuit comprises a resistance network and a bipolar junction transistor, wherein the resistance network is connected to the route of the output current and used for generating a voltage according to the output current; the bipolar junction transistor is provided with a base which is connected with the resistance network, and used for receiving the voltage to provide a collector signal as the output feedback; and the resistance network has a temperature-dependent resistance value to compensate the temperature effect on the output current from the base voltage of the bipolar junction transistor. The secondary side circuit for the flyback power converter and the method for stabilizing the output current of the flyback power converter has the advantages that stable fixed current output can be provided, and the replaceable structure with complex control mode and high cost can be replaced.

Description

technical field [0001] The invention relates to a power converter, in particular to a circuit and method for compensating temperature effects in a secondary side circuit of a flyback power converter. Background technique [0002] Bipolar junction transistor (BJT), its base-emitter voltage (V BE ) is typically 0.7 volts, but at elevated ambient temperatures, V BE It will decrease due to the increase of ambient temperature, resulting in system instability, so it can only be applied to systems that can tolerate large fluctuations. When designing systems that require stable current, BJT will be avoided in certain circuits. For example, in a flyback power converter, if the output current of the BJT reaction flyback power converter is used as output feedback, the output current will exceed the specification when the temperature fluctuates. Using a switching architecture to provide output current control can provide a more stable output current, but it uses more components, more ...

AI Technical Summary

Problems solved by technology

For example, in a flyback power converter, if the output current of the BJT reaction flyback power converter is used as output feedback, when the temperature changes, the output current will exceed the specification

Using a switchable architecture to provide output current control can provide a more stable output current, but it uses more components, more complex circuits, more difficult control methods, and higher costs

[0003] Therefore, the known BJT architecture has the above-mentioned inconveniences and problems in realizing the temperature compensation capability.

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