Method and Apparatus for Power Supply

This invention relates to supplying power to an input/output channel for an Industrial Process Control System. The invention provides a power supply comprising a primary voltage converter having a first voltage input and a second voltage output, and overvoltage protection components preventing said second voltage rising above a predetermined maximum; a first low dropout regulator connected to receive said second voltage and to generate a third voltage; a second low dropout regulator connected to receive said second voltage and to generate a fourth voltage; and a third low dropout regulator connected to receive said fourth voltage and to generate a fifth voltage. The invention also provides a power supply for a channel of an input module comprising a field programmable gate array for generating a pair of complementary square waves on two output pins or on two parallel groups of output pins for higher current capability; and a transformer comprising two inputs connected to receive each of said pair of complementary square waves.