Talk about switching transformer and working principle

Talk about switching transformer and working principle

switching transformer, also known as pulse transformer, is another name for it.It belongs to the transformer in the switching power supply, which also works in the switching state.Generally, it works in pulse state, and its frequency ranges from dozens of Hz to thousands of Hz.

On the classification of switching transformers, for the input voltage, there are single and double excitation type: for the output voltage, there are positive and fly back type.Single and double excited switching power supply, or forward and reverse switching power supply, they use the switching transformer, in the working principle is also very different.

When the input voltage of dc pulse voltage switching transformer, known as the single pulse input, the single polarity of the input pulse switching power supply is called single excitation transformer switching power supply: when the input voltage switching transformer for alternate positive and negative pulse voltage, called bipolar pulse input, the double polarity of the input pulse switching power supply is called double excitation transformer switching power supply;

When the primary coil of the transformer is being excited by dc pulse voltage, the secondary coil of the transformer has power output.When the primary coil of the transformer is excited by dc pulse voltage, the secondary coil of the transformer does not provide power output to the load, but only after the excitation voltage of the primary coil of the transformer is turned off to provide power output to the load. This type of transformer switching power supply is called fly back switching power supply.

Set switching transformer core section for S, when the amplitude for U, width for tau rectangular pulse voltage applied to the switching transformer primary winding, the switching of the transformer in the primary coil excitation current flow: at the same time, can produce magnetic field in the switching of the transformer core, transformer iron core will be magnetized, the magnetic field intensity H under the action of magnetic field and can produce magnetic induction intensity for magnetic flux of B, hereinafter referred to as flux, with ", says: "magnetic induction intensity B or flux phi is affected by the effect of magnetic field intensity H and change process, known as the magnetization process.The so-called excitation current is the current that makes the transformer core magnetize.

switching transformer working principle

220V ac, after rectification and filtering, becomes 310V dc.This dc voltage is applied to the collector of the switching tube through the primary of the switching transformer. At the same time, a certain bias is applied to the base of the switching tube, which will make the switching tube conduct.Because electricity momentary switching tube conduction, so in the switching tube collector switching transformer primary current, the result of the current magnetic field on the switching transformer core, the magnetic field produced in the feedback coil voltage, the voltage switching tube at base, the positive feedback voltage switching tube more conduction, magnetic field, the feedback voltage increase.

The switching tube is further conducted until saturated.The current through the collector of the switching tube is the maximum after saturation.But the current varies less.Until it doesn't change.The primary current of the switching transformer does not change, the induced magnetic field disappears, and the feedback voltage disappears.switching tube base due to the feedback voltage disappears, it consists of the saturated state of the deep, quickly returned to the conduction state, collector current rapidly decreases, and the decrease of current, make the magnetic core to produce a magnetic field, contrary to the foregoing the same instead of magnetic field on the feedback coil produces a contrary to the feedback voltage, the voltage on the base of the switching tube, speeding up the switching tube by the conduction deadline, the end of the switching tube, current disappear, disappear, the feedback voltage switching tube under the action of dc bias, began the next conduction, saturation, conduction, by the process.This process of continuous cycle, is the principle of switching power supply.

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