Linear Technology has an overvoltage protection controller which operates from 9V to greater than 500V.

The LTC4366 floating surge stopper uses an adjustable floating topology to enable very high voltage operation independent of the voltage rating of the device’s internal circuitry.

Two internal shunt regulators coupled with the external voltage-dropping resistors generate the LTC4366’s internal supply rails. The maximum operating voltage is set by the breakdown of the external resistors and mosfets.

The chip monitors the voltage at its output and reacts quickly to input supply overvoltage by controlling the gate of an N-channel mosfet. It regulates the output to a user-defined voltage during an overvoltage transient allowing the load to remain operational while the overvoltage is dropped across a mosfet.

An adjustable fault timer ensures safe shutdown if the fault persists. 

Typical high voltage applications include protecting from motor transients, coupled overvoltage, incorrect input supplies or power supply failures.

While traditional protection circuitry relies on bulky inductors, capacitors, fuses and transient voltage suppressors to clamp the transient, the LTC4366 protects by series regulating the transient. It is packaged in a tiny 8-lead TSOT-23 and 3mm x 2mm DFN packages. During operation, the entire circuit consumes only a few milliamperes, and the device may be shut down to less than 20µA.

www.linear.com/product/LTC4366