In September of 2002， a new client approached Controltek requesting design services for a constant current power supply. This supply would receive a regulated 48-volt input and was required to generate a user adjustable constant current output in the range between 3 and 8 Amps. Current regulation including ripple was to be less then±10% of selected output level. This circuit had to operate over a varying load range between 1_ and 16_ and drive four such independent loads switched in one at a time. In addition the constant current supply is be followed by an H-bridge that switches the direction of current flow through the load at fixed intervals. Regulatory agency approval to UL 508 and CSA 22.2 was also required. The supply had to operate over a temperature range between -20°C to +70°C in a NEMA 4 enclosure with no ventilation or external heat sinking.