DER-172: 70V @ 130mA, 108 ~ 132VAC in

This engineering report describes a power supply utilizing the LinkSwitch-TN device LNK306PN in a buck-converter topology.

This power supply operates using input voltages ranging from 108 to 132 VAC. This ensures a DC bus voltage large enough to support a 70 V output. In a buck topology the output voltage is always smaller than the input voltage. The output voltage is limited by the maximum duty cycle of the LinkSwitch-TN, requiring the input voltage to be sufficiently larger than the required output voltage.

This particular design requires a minimum of 108 VAC input. This circuit utilizes a 22 μF DC bus filter capacitance which ensures the required output level given the constraints of the LNK306PN's duty cycle. To use a truly universal input range (90 to 132 VAC) either reduce the output voltage to 60 V or change the value of the input capacitor C2 to 68 μF.

This document contains the power supply specifications, schematic, bill of materials, inductor specifications, printed circuit layout, and performance data for the design.

* One build of this design had a 0.57 power factor using a Kill-A-Watt P3 (72V load).