In the design and production of high-frequency transformer
, it is often encountered that all links have made enough efforts, but the heat of transformer working still can not be reduced.
At this time, there are some other related factors easy to be ignored, leading to transformer heating.
When the transformer design is not a problem, but the working temperature can not be reduced, it is necessary to shift attention from the transformer to the peripheral circuit equipment characteristics actually from the peripheral equipment caused by the interaction with the transformer working temperature caused by the high temperature rise, but also the transformer heating factor, after all, for the whole power supply, the original side switch tube also accounted for a considerable proportion.
Good, side rectifier tube or absorption compensation, resonant circuit (inductance or capacitance), even PFC and filter capacitor, PCB wiring, transformer equipment belongs to the same whole, its working state is bound to affect each other only affect the strength of the effect.
Secondary rectifier diode has the greatest influence on transformer operating temperature rise.
Taking the common high-power power supply as an example, analyze the working state of low-power flyback diode.) No matter the two full-wave rectifier diode pipelines on the side of the bridge topology, or the rectifier and continuous diode in the forward topology, instantaneous common-state on-off phenomenon will occur in the reverse recovery period. Therefore,
Sinusoidal (sometimes not completely) is sinusoidal) peak oscillation, much higher than the switching frequency, the voltage peak high wave will be coupled between the primary and secondary sides, increasing the various losses of the wire packet and the core, especially exponentially proportional to the frequency of the loss increase is more obvious.
Because in the first peak period of the common-state conduction moment of the bipolar pipeline, the excitation inductance of the original side drops to close: the leakage value of the original side measured by the short-circuit side, if not handled properly, the instantaneous peak current of the original side will exceed the normal operation of several times to ten times!
At this time, the magnetic swing of the magnetic core △B winding wire will also sharply increase the high frequency current density, and then attenuation vibration. In the process of fluctuation, although the loss is decreasing, the attenuation and oscillation of the entire peak value are generated with the working frequency. It is not difficult to imagine that the line temperature and iron temperature will rise again and again.
Such spikes can also adversely affect the reliability of the power supply.
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