Patent ID: 7432756

Claim:
A power stage for providing switched electrical power to a load, comprising: a normally on field-effect transistor (FET) having a gate node and having a high-current source-drain channel connected between the load and a ground reference of the power stage; a gate drive circuit having a negative supply input and a control output, the control output being coupled to the gate node of the normally on FET, the gate drive circuit including a low-side switching device coupled between the control output and a negative supply input, the low-side switching device being operative in response to a switching control signal to drive a voltage of the gate node of the normally on FET to substantially a value of a negative supply voltage appearing on the negative supply input, the negative supply voltage being sufficiently negative with respect to the ground reference of the power stage to substantially turn off the normally on FET; and a regulated charge pump circuit operative to generate the negative supply voltage from a fixed positive supply voltage of the power stage, the regulated charge pump circuit including (1) storage and switching circuitry operative to generate the negative supply voltage based on an oscillator signal, (2) oscillator circuitry operative to generate the oscillator signal based on a variable positive supply voltage derived from the fixed positive supply voltage such that fluctuations in the variable positive supply voltage result in corresponding changes of the negative supply voltage, and (3) a regulator operative to generate the variable positive supply voltage in response to the negative supply voltage to maintain the negative supply voltage at substantially a target regulated value.