High efficiency linear power supply with a preregulator controlled by keeping constant R/sub DS/ of MOSFET

In Synchrotron Radiation Research Center (SRRC) more than ninety linear power supplies with 100 ppm long-term stability are served for correction magnets. To increase the well-known efficiency problem of linear power supply, inside a customer-made bipolar linear power supply a homemade pre-regulator circuitry is in series in front of power stage. By using constant V/sub DS/ controlled pre-regulator, the power consumption of linear power supply itself could be reduced and the efficiency changes with respect to the output power. On the other hand, with constant R/sub DS/ controlled pre-regulator, the efficiency is even higher and is the ratio of load resistance and R/sub DS/. Design and performance of the pre-regulator circuitry are demonstrated.