Patent ID: 8203815

Claim:
A transient overvoltage protection circuit for providing transient overvoltage protection, the transient overvoltage protection circuit comprising: a high-side input for connection to a positive terminal of an external power source; a high-side output for connection to a positive terminal of an internal power supply connected to supply power to a load; a low-side input for connection to a negative terminal of the external power source; a low-side output for connection to a negative terminal of the internal power supply; a transistor connected in series between the low-side input and the low-side output; a capacitor connected between the high-side output and the low-side output in parallel with the internal power supply such that when the transistor is turned OFF the capacitor supplies stored power to the internal power supply; and a control circuit connected to monitor voltage at the high-side input and in response to a detected overvoltage transient turns the transistor OFF to disconnect the internal power supply from the external power source, wherein the control circuit includes a voltage divider network connected between the high-side input and the low-side input for providing a divided voltage that is a function of voltage between the high-side input and the low-side input and a comparator connected to compare the divided voltage to a reference voltage, wherein an output of the comparator controls the state of the transistor.