The present invention increases power efficiency in power FET applications with varying loads. A constant frequency mode can be used without detracting from efficiency. This is accomplished by reducing repetitive gate charge power losses. The present invention controls the channel impedance of the FET using a timed tri-state driver to drive a level of charge associated with the gate of the FET that is appropriate to the load requirements. When the voltage level at the FET gate reaches the appropriate level, the driver is tri-stated, so that the gate does not continue to charge.