The basic composition of the switching power supply transformer and its good and bad judgement method
Switching power supply transformer and switching tube together constitute a self-excited (or other excitation) type of intermittent oscillator, so as to modulate the input DC voltage into a high-frequency pulse voltage. Play the role of energy transfer and conversion. In the flyback circuit, when the switching tube is on, the transformer converts the electrical energy into magnetic field energy storage, when the switching tube cut-off is released. In a forward circuit, when the switch is on, the input voltage is supplied directly to the load and the energy is stored in the energy storage inductor. When the switch is switched off, the energy storage inductor continues the flow to the load. The input DC voltage is converted into various low voltages as required.
Basic components of switching power supply transformer.
The main materials of the switching power transformer: magnetic materials, wire materials and insulation materials are the core of the switching transformer.
When it comes to verifying the switching transformer is good or bad, what induction method ah, ringing method / waveform method, etc., ah, there are always limitations of the method, relying on comparative data, relying on the experience of the inspector. experience of the tester. If there is a short and simple method, the test results are clear, it would be good. For example, feed a relatively safe low voltage to a switching power supply, so that the circuit is in an unregulated open loop. The circuit is in an unregulated open-loop state, and there is no harm to the load circuit, so you can safely and boldly add power to the switching power supply, it would be good. Then for How many volts DC is considered safe for the circuit?
Coincidentally, it happens to have a switching transformer winding data on hand, DC500V winding and 5V winding turns ratio of about 20:1, 5V winding 5 turns, 500V winding For 100 turns. Oscillator chip using 3844, the maximum duty cycle of the output pulse is 50%. By can be roughly estimated, when the circuit is open-loop work, the maximum switching tube It can be roughly estimated that when the circuit is open-loop, the maximum input voltage of the 500V winding is 200 V. From this, it can be seen that this switching power supply can ensure that the secondary load voltage will not be higher than the rated value when the input voltage is not higher than DC200V. secondary load voltage will not be higher than the rated value. It can be seen that, for this circuit, as long as the original power supply DC530V power input input below 200V DC power supply; for the 3844 directly provide higher than 16V (vibration voltage) such as 18V Voltage) such as 18V power supply, without changing the original voltage composition, you can directly verify the switching power supply circuit in the switching transformer and other components. In open-loop operation In open-loop operation, the switching transformer winding output voltage, and its turns ratio should be proportional/linear relationship, if this condition is met, the switching transformer is good, if the secondary winding output voltage is significantly lower than that of the switching transformer. If the output voltage of the secondary winding is significantly lower than this value, the switching transformer is bad.
