Abstract: An apparatus is disclosed that provides an estimate of the semiconductor junction temperature of a semiconductor device as a function of the electrical current flowing across the corresponding semiconductor junction. The apparatus includes a current sensor that samples and measures the current flowing across the semiconductor junction and provides an output signal indicative of the measured value to a current-to-temperature converter. The current-to-temperature converter estimates the temperature of the semiconductor junction using equations that include constants empirically derived for the particular device configuration including cooling and mounting methods used with it. The current-to-temperature converter provides an output temperature signal that is compared to a predetermined temperature threshold value, and in the event that the output temperature signal exceeds the predetermined temperature threshold value, an alarm signal is set.

Abstract: A current sensor apparatus is disclosed for use with an inverter bridge that is controlled by a pulse width modulator (PWM) control apparatus and is connected to an inductive load. The current sensor apparatus includes a plurality of current sensors disposed in series with each of the low side switches in the inverter bridge. The PWM control apparatus samples the current sensors when the PWM control apparatus provides the necessary signals to open all of the high side switches in the inverter bridge and to close all of the low side switches. Due to the inductive nature of the load, the load current will continue to flow during the time in which the low side switches are closed and the high side switches are open. During this time, the current sensors are sampled and provide an output signal that is indicative of the magnitude of the current. The PWM control apparatus limits the duty cycle of the PWM signals to a predetermined value that is less than 100%.