Method for estimating a temperature of a transistor

A method for estimating junction temperature or die temperature of a transistor of an inverter system, the method comprising:

• measuring, by a detector, a turn-off change in voltage (dvce/dt) with respect to change in time between a collector and emitter of a transistor in a phase of an inverter;
• measuring, by the detector, a peak voltage (vcepeak) of the transistor between the collector and the emitter, where the measuring of the peak voltage (vcepeak) of the transistor is triggered by a drop in vge, or a voltage applied to a base or a gate of the transistor in an active state;
• and upon the triggering the peak voltage of a transient spike in a collector voltage of the transistor is measured via a series of cascaded multimode diodes and a resistive voltage divider;
• determining, by an electronic data processor, intermediate parameters of turn-off current (iceturnoff), the turn-on current (iceturnon) and on-state voltage drop (vceon) based on the turn-off voltage change (dvce/dt) and the peak voltage (vcepeak);
• determining, by the data processor, the power or energy loss for one switching cycle of the transistor based on the turn-off current (iceturnoff), the turn on current (iceturnon) and on-state voltage drop (vceon) between the collector and emitter of the transistor;
• and
• estimating, by the data processor, an associated average junction or die temperature for the transistor over the switching cycle based on the determined energy loss, observed inverter system temperature and thermal characteristic of the inverter system, where an inverter system temperature sensor measures a coolant temperature in a coolant system for cooling the inverter or a housing temperature of an inverter housing.

A method for estimating junction temperature or die temperature of a field effect transistor of an inverter system, the method comprising:

• measuring, by a detector, turn-off change in voltage with respect to change in time between a drain and source of a field effect transistor in a phase of an inverter;
• measuring, by the detector, peak voltage of the field effect transistor between the drain and the source, where the measuring of the peak voltage of the field effect transistor between the drain and source is triggered a drop in a voltage applied to gate of the field effect transistor in an active state;
• and where upon the triggering the peak voltage of a transient spike in a drain voltage of the field effect transistor is measured via a series of cascaded multimode diodes and a resistive voltage divider;
• determining, by an electronic data processor, intermediate parameters of turn-off current, the turn-on current and on-state voltage drop based on the turn-off voltage change and the peak voltage;
• determining, by the data processor, the power or energy loss for one switching cycle of the field effect transistor based on the turn-off current, the turn-on current and on-state voltage drop between the drain and source of the field effect transistor;
• and
• estimating, by the data processor, an associated average junction or die temperature for the transistor over the switching cycle based on the determined energy loss, observed inverter system temperature and thermal characteristic of the inverter system with an inverter system temperature sensor that measures a coolant temperature in a coolant system for cooling the inverter or a housing temperature of an inverter housing.