Transient over voltage protection circuit for electrical power converters

摘要

A transient voltage protection circuit includes a normally closed switch connected between a rectifier circuit and a DC to DC converter. This switch is caused to switch to a current limit state when the voltage input to the DC to DC converter exceeds a first predetermined value, thereby protecting the DC to DC converter from voltages that exceed the converter's operational limits. The switch is returned to its normally closed state when the voltage input to the converter drops below a second predetermined lower value. A capacitor connected across the input terminals of the converter is charged up when the switch is closed and functions to supply power to the DC to DC converter when the switch is in its current limit state. The current limit state of the switch comprises the periodic switching of said switch between a normally closed state and an open state, said switch being caused to open when the voltage across said capacitor reaches said first predetermined value and to close when the voltage across the capacitor drops to said second predetermined lower value.