![]() ![]() The threshold current of the overcurrent protection can be set by P2 potentiometer. ![]() Transformer TR3 into pin 3 of the UC3845 chip. Current feedback is fed through the current Galvanic isolation of the feedback is not necessaryīecause the control circuit is connected to the secondary SMPS side and isolated from the mains. The output voltage of the power supply can be set using the potentiometer P1. Is connected from the output to pin 2 of IO1. Its output is then rectified and finally averaged by inductor L1 and smoothed by capacitor bank C17. They then switch rectified mains voltage (325V) to power transformer Via shaping circuits with T3 and T4 it drives gates of IGBTs T5 and T6. It provides galvanic isolation and floating drive for upper IGBT. The chip controls the MOSFET T2, which drives the gate-drive transformer Tr2. The original UVLO thresholds of UC3845 are simply too low. The UC3845 chip then begins to work atġ4.1 V and never runs below 13.5 V, which protects the IGBT transistors from desaturation. It is powered through the zener diode, which reduces the supply voltageīy 5.6 V (ie to 11.4 V) and also shifts the UVLO thresholds of 7.9 V (lower) and 8.5 V (upper) to 13.5 V and 14.1 V. ![]() UC3845 control circuit has the output frequency of 50kHz and 47% maximum duty cycle. R27 provides undervoltage protection of auxiliary power - it will not turn on at less than 230V DC. It is similar toĪ power supply described here. The auxiliary power supply circuit uses TNY267. Select R1 value so that the voltage at the relay coil and the fan was 12V. Relay coil and fan (from an AT / ATX PC power supply)Īre powered from 12V, which is dropped from 17V aux supply using a resistor R1. It is then rectified using a bridge rectifier and smoothed using capacitor C4.ĭue to high capacity, there's an inrush limiting circuit with Re1 relay contact and R2 resistor. Mains voltage goes first through an EMI interference filter. The schematic of my switching power supply you can see below. The switching supply uses IGBT transistors and is controlled by UC3845 chip. In my article about SMPS's it is a topology II.D. (2400W = 2.4 kilowatts!), so I chose a switching topology of a two switch forward (half-controlled bridge). Linear topology would be unusable for this power This switching power supply was built because I needed a powerfull adjustable bench power supply. High power adjustable switching power supply (SMPS) 3-60V 40A ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2022
Categories |