Patent ID: 9716380
Date: 2017-07-25
CPC Classifications: B60L,H02H,H02M

Claim:
1. A power supply circuit for a trip unit of a circuit interrupter, comprising: a current transformer structured to provide a voltage indicative of a primary current flowing through the circuit interrupter; a rectifier structured to rectify the voltage from the current transformer and output a rectified voltage; a regulator structured to: (i) provide a regulated voltage from the rectified voltage and (ii) supply energy to a trip actuator; a startup circuit structured to be powered by the regulated voltage; and a DC/DC converter coupled to an output of the startup circuit for receiving the regulated voltage, the DC/DC converter having a shutdown mode; wherein the startup circuit includes a burden impedance, a switch electrically connected in series with the burden impedance, and wherein the startup circuit is structured to: (i) burden the current transformer through the series combination of the switch and the burden impedance and cause the DC/DC converter to enter the shutdown mode when the regulated voltage is below a predetermined value, (ii) remove the burden and cause the DC/DC converter to exit the shutdown mode and provide power to the trip unit responsive to the regulated voltage reaching the predetermined value, and (iii) remove the burden and cause the DC/DC converter to exit the shutdown mode and provide power to the trip unit responsive to a rate of change of the regulated voltage being at least a predetermined level.