A power source delivers power from a main power source using switching by a normally on transistor. A driver switches on and off the normally on transistor under a control signal by a controller during regular operation. A housekeeping power supply delivers auxiliary power to the driver. The driver switches off the normally on transistor during irregular operation. Irregular operation occurs at least when the control signal is absent or no auxiliary power is available or during transients such a power up or down. Bridge block pairs thereof can be arranged to form a half bridge power switch, an H bridge switch, a three phase bridge switch, a multi-phase switch, a buck converter, a buck-boost converter, or a boost converter.