Push-pull HV Switcher
Traditional mains transformer-based power supplies are nice and quiet in terms of noise but they are also big and bulky. Another one of their down sides is the wasteful use of power. For example, in my linear high voltage supply project the dirty voltage (before the stabilizer) is about 240V. If I wanted 180V out at 200mA, this means 12W dissipating on the passing transistor alone. To that, add the losses in the circuit, in the transformer and the diode bridge. I admit I never actually measured it but I would ballpark the losses at 40%. As you can see, efficiency is not one of the virtues here.
What if tables were reversed and the size and efficiency were important. In some applications, one can tolerate some noise. A switch-mode power supply would then beat the competition hands down.
Happy switching, 73 de Brian