Patent ID: 8213134

Claim:
An apparatus to prevent smoke in a power supply, the apparatus comprising: a positive temperature coefficient device configured in parallel with a bypass switch and implemented at an input to a switching regulation stage of a switching power supply, the positive temperature coefficient device comprising a device that increases in electrical resistance in response to an increase in temperature, the switching regulation stage comprising a regulation switch that is switched on and off to maintain an output voltage of the switching regulation stage; a monitoring module that determines that a voltage across the regulation switch in the switching power supply is below a predefined threshold voltage for greater than a predefined threshold time period; and a control module that controls operation of the bypass switch, the control module opening the bypass switch in response to the monitoring module determining that the voltage across the regulation switch is below the predefined threshold voltage for greater than the predefined threshold time period such that substantially all of the current entering the switching regulation stage passes through the positive temperature coefficient device, wherein prior to opening the bypass switch, the control module maintains the bypass switch in a closed position such that substantially all of the current entering the switching regulation stage passes through the closed bypass switch.