A three phase buck power converter having input power control is described. The power converter uses a three input buck converter comprising switches for each phase, a catch rectifier, an inductor and an output capacitor. The duty cycle of the three switches is constrained to have a sine function relationship that may be derived from the input voltage wave form or from a reference oscillator. When so constrained, the input currents have high power factor. The output is a precise, high quality dc voltage, comparable to the output of a dc--dc buck converter, and the dynamic response is comparable. Voltage mode and current mode controls are shown, as is a precise line regulation feed forward for the voltage mode embodiment. The three phase buck power converter may be operated in reverse as a three phase boost converter, as they are reciprocal. A three phase ac--ac converter may have a three phase buck converter as its input and a three phase boost converter as its output.