This circuit has only eight low-cost components besides the transformer: two transistors, two resistors, two diodes, and two capacitors. The transistors TR1 and TR2 are alternately switched on and off in antiphase by the two feedback windings T1af and T1bf, and the secondary winding output is rectified by the diodes D1 and D2 before being smoothed by the output capacitor C2. For a full analysis of the Royer topology, refer to the
DC/DC Book of Knowledge.
A Royer topology DC/DC converter has many advantages: low BoM, compact size (down to <0.5cm
3) and high isolation (up to 4kVDC/1s). It is also very easy to create a dual +/- output by adding an extra capacitor and reversing D2, making it ideal for powering dual rail op-amps, A-to-D converters or bipolar sensor circuits. The main disadvantage is that the output is unregulated, but with a stable supply voltage and 10-100% load range, the output voltage is typically within ±10%, an acceptable figure for
cost effective designs.
For applications that need a low power, yet galvanically isolated supply, it is the most popular DC/DC converter solution on the market.