II. FEASIBILITY OF ON-LINE POWER MODULE
TEMPERATURE EXTRACTION
A. TSEP approaches for on-line power module
temperature measurement
Most physical parameters of silicon semiconductor
devices are a function of temperature. The intrinsic carrier
concentration and carrier lifetime increase with Si
temperature, but the mobility of electrons and holes decrease
with the temperature [9]. Because the relationships between
semiconductor physical parameters and temperature are
fixed, the inner chip temperature can be extracted from the
electrical characteristics without intruding into the package.
This means the thermal sensors or infrared instruments are
not required for simple non-invasive on-line chip
temperature extraction.
Although having a large number of passive P-i-N power
diodes without the need for a gate driver, TSEPs like
threshold voltage Vth and turn-on/off delay time Tdon/Tdoff are
usual for IGBT modules. In the case of high power P-i-N
diodes, the leakage current Ilk, which is relatively low and is
related to the chip temperature and the voltage across the
power module. Any milliampere level current sensor inserted
in series with the power module would suffer the large
operation current when the power module is in the
conducting on-state. The forward drop voltage under low
injection current Vsat is a common TSEP, which can be
adopted to predict the chip temperature and monitor wire
bonding lift-off [10]. However, precise current-injection
equipment is required to make sure that the current is low
enough to avoid self-heating effects. Moreover, the
measurement equipment requirements will be high for
utilizing the TSEPs of Ilk and Vsat.
During the turn-off transition of the high power P-i-N
diode, the maximum reverse recovery current rate di/dt and
the maximum voltage rate dv/dt can be taken into account as
TESPs [11]. Therefore, the temperature estimation of power
diodes can be carried out by monitoring the maximum dv/dt
during the turn-off transition, which is sensed by a shunt
connected capacitor. Similarly, temperature estimation of
power devices can also be achieved by measuring the
maximum di/dt using a series connected inductor. The
forward voltage drop under high current injection VF, or di/dt
and dv/dt dynamic parameters can be employed to indirectly
measure P-i- N diode chip temperature.