This is a a circuit from my Power Supplies Section. There may be some documentation errors in my circuits. If you are used to building and troubleshooting circuits then it is ok.
This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST Micro. U1A is wired as a differential amplifier and U1B a High Gain Comparator. C4 and C5 are parallel for lower ESR. Equivalent series resistanc Fast switching diode used is BYW80.
A Power Transistor which is having a drop of 4 Volts across it and passing 3 amps thru it, may dissipate around 12 Watts of Heat, This is the problem in Series Regulators.
While a Saturated Transistor or Mosfet with 1 Volts across and 3 Amps Thru will be just 3 Watts. But then a fully on transistor or mosfet cannot be controlled or regulated, for that we turn it ON and OFF very fast so that the right amount of current or voltage is delivered.
This circuit is derived from an application note of L296, It is a Power Switching Regulator from ST. The advantage of using a switching regulator is that there is not much Heat Dissipation in this circuit.
Switching Battery Charger with L296 - del20031
If you had to build the same with a series regulator, it would be very big due to external transistor and a huge heat sink. This circuit takes a small place on PCB, efficiency is high so power is saved and reliability of product improves, lastly the thermal gradients within the cabinet is avoided so that any form of drift or component specs variation can be avoided.
This is a SMPS Circuit improved over the Application Note in the book SGS Motion Control Application Manual. This worked well. It helps you learn more about High Frequency Power Supply Design. More details and PCB's Here SG3525 SMPS Project.
This was the Module that contained the smps chip. It was done to prevent easy replication by other firms. Also to Keep the Signals isolated from the Main board board currents and Corrosion Prevention by impregnating Module in Epoxy. Yet the main board suffered some corrosion even with some coating protection.