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48V-12V DC to DC converter circuit

Published on Mar 16 2011 // Instrumentation and Tester Circuits

Due to the electric vehicle 48V – 12V of DC – DC converter is broken, could not find the relevant information online, especially for peer analysis of the maintenance or self-reference, I checked a number of schematic, foolproof, and extra I have experience in testing FET!
Work :
This figure was derived based on physical analysis, power supply via D2, R1 to IC1 to provide a voltage of about +12 V, 6 pin output pulse transformer coupled by C4 and Q1 after the drive oscillation, when Q1 turns on after the output current through L filtered by C9 power to the load when Q1 off, the transformer inductor B3 magnetic energy into electrical energy, and its negative polarity Left Right now, freewheeling diode D4 turns on the load current through the diode to continue to supply the load by smooth DC, When the output voltage is too low or too high, from the resistor R11, R10, R9 divider circuit formed by sampling the voltage to IC1 2 feet compared with the internal 2.5V reference voltage, Q1 turns on after the control pulse width, so that the output voltage be stable. When the load current when a short circuit or over 8A, IC1 3 pin voltage rise will control the pulse width of the Q1 off, to ensure the safety of Q1.
C8, and R7 form oscillation time constant, the circuit’s oscillation frequency 65KHz, which is calculated under the formula:

 48V-12V DC  to  DC converter circuit 1

3845 Internal structure and pin functions

① error amplifier output / compensation
② Voltage Feedback Input
③ current sampling input
④ oscillation circuit time constant
⑤ to
⑥ switch drive pulse output
⑦ Power
⑧ 5V reference voltage and oscillator phase generally

48V-12V DC  to  DC converter circuit 2

Appendix: Digital multimeter test FET method :
File with the red pen then the diode gate G, source black table pen then S, digital table shows the 1, the black pen then S does not move, will the red pen to move the drain D, this time about digital sheet should show the value of 150-300 will the red pen then source S, drain the black pen then D, then the data should be 60-100, and then change over, then black, S, D then red, then the data is about 150-300, with hand side of the connection D, while touches the gate G, or clamp the short circuit DS, then the data will gradually become infinite one, and then switching table pen, then red, S, D then the black, the data will be 500 or so, then prove The tube is good! (Purely personal insight, understanding of the inadequacies still hope)