How to analyze the adjustable switching power supply?
The switching power supply has high efficiency. Adjustable voltage/current power supplies are novel tools for many applications such as Li-Ion/battery chargers or power supplies. The construction of this switching power supply requires an adjustable benchtop power supply. For this power, a linear topology (2400W = 2.4kW!) cannot be used, so two positive switches (half-controlled bridge) switching topology was chosen. IGBT transistors are used in switching power supplies and are controlled by chips.
The supply voltage is first passed through an EMI interference filter. It is then rectified with a bridge rectifier and smoothed with capacitors. Because of the high capacity, there is an inrush limiting circuit with relay contacts and R2 resistor. Relay coil and fan powered by 12V (via AT/ATXPC power supply), decompressed from 17V supply with resistor R1. Choose the value of R1 so that the voltage across the relay coil and the fan reaches 12V. TNY267 is used in the power circuit. This is pretty much the same power supply as described here. When it is below 230VDC, the undervoltage protection provided by R27 will not open. The output frequency of the control circuit is 50kHz, and the duty cycle is 47%. The power supply is supplied by the Zener diode, and the Zener diode converts the power supply voltage to 5.6. V (i.e. down to 11.4V) and the UVLO thresholds of 7.9V (low) and 8.5V (high) are moved to 13.5V and 14.1V. The chip then starts operating at 14.1V and does not operate below 13.5V, thereby protecting the IGBT transistors from saturation.
