The LM5020 PWM controller is used here to design a low cost, multi-output, flyback power supply. In this case there are three output voltage rails formed by the use of multiple secondary windings off of the transformer, T1. Regulation is typically better than 5% on the master output, 100V, which is sampled and fedback to the controller; whereas, the slave regulation, accomplished through cross coupling, is good to within +/-20% on the negative 36V and 52V outputs. The input voltage, Vin, charges up energy in the primary coil of the transformer during the on-time of the FET switch, M2; then, during the off-time this energy is coupled to the secondary to the three outputs through the diodes, D1,2,3, as part of what's known as a "flyback" action. Low cost is achieved by using small ceramic capacitors on the input, C4, and the outputs, C6,7,8. The feedback signal to complete the control loop and to provide transient compensation is provided by the resistor/capacitor combinations created by R6,7,10, and C9,10.
Notes:
1. T1 is an off-the-shelf part.
2. T1 in the schematic is shown as L1 in the PCB layout.
3. The MOSFET M2 in the schematic is shown as U2 in the PCB layout.
Schematic
Example Schematic Showing Connection for all Components.
Example Schematic Showing Connection for all Components.
