Power supply circuit and method of calibration therefor

Abstract

A power supply circuit ( ) for supplying power to a load ( ) comprises a regulator ( ), a switching transistor ( ) connected to the regulator; and a power transformer ( ) connected between the switching transistor and the load. The regulator is of a type that requires feedback regarding the amount of voltage supplied to the load. In accordance with the present invention, a feedback signal to the regulator is generated by monitoring an input to the power transformer. In particular, a voltage signal related to a voltage on the primary of the power transformer after a voltage spike is applied as the feedback signal to the regulator. A peak detector ( ) detects the to voltage spike and applies the voltage signal to the regulator. A peak detector reset circuit ( ) resets the peak detector. In one example context of usage, a variable air gap exists between a stationary primary of the power transformer and a secondary of the power transformer. For example, the secondary of the power transformer can be mounted with the load on a rotatable element, such as a rotating drum of a magnetic tape drive. A zener diode ( ) is connected in parallel across the secondary of the power transformer.