1. Field of the Invention
The present invention relates to an integrated circuit, and more particularly to a high voltage integrated circuit.
2. Description of the Prior Art
A variety of power supplies and motor drivers utilize the bridge circuits to control a power source to the load. The bridge circuit normally has a high-side transistor connected to the power source and a low-side transistor connected to ground. A common node between the high-side transistor and low-side transistor is coupled to the load. As transistors are controlled to alternately conduct, the voltage of the common node swings between the voltage of the power source and the ground. Therefore the control of high-side transistor requires a charge pump circuit and/or a floating driver in order to fully turn on the high-side transistor. In recent development, many floating circuits are disclosed in U.S. Pat. No. 6,344,959 (Milazzo), U.S. Pat. No. 6,781,422 (Yang) and U.S. Pat. No. 6,836,173 (Yang).
FIG. 1 shows a high-side transistor drive circuit, in which a circuit 10 is the floating driver. A capacitor 40 provides a supply voltage to the floating driver 10. A voltage VD charges the capacitor 40 through a diode 45 once the low-side transistor 30 is switched on. The ground reference of the capacitor 40 is pulled to the level of the voltage source VIN when the high-side transistor 20 is turned on. This happens, because turning on the high-side transistor 20 shifts the bridge circuit into a low impedance state.