Gate drive devices such as the
TPS7H6003-SP have several different components that comprise the power losses. The
quiescent power losses PQCcan be determined using Equation 21 :
Equation 21.
where:
- IQLS is the
low-side quiescent current (selected for PWM mode in this design)
- IQHS is the high-side quiescent current (selected for PWM mode in
this design)
- VBOOT is the voltage at BOOT with respect to ASW
Leakage current power losses PBG
can be calculated using Equation 22 :
Equation 22.
where:
- VBG is the voltage
between BOOT and AGND
- IQBG is the BOOT
to AGND leakage current
There are losses that occur within the driver due to the charging and discharging of
the GaN FET gate charge. To determine these, first calculate PGATE
as:
Equation 23.
This loss is actually distributed amongst the resistances in the gate driver loop,
which includes the driver, the gate resistances and the GaN FET. The power
dissipated within the TPS7H6003-SP for both turn-on and turn-off can be
calculated:
Equation 24.
Equation 25.
Equation 26.
Equation 27.
In this instance, the high-side and low-side losses are the same:
Equation 28.
Equation 29.
Finally, the PGATE losses within the driver can be found:
Equation 30.
Equation 31.
Equation 32.
There is also a component power consumption associated with the operating current of
the driver itself, which is specified at no-load and frequency dependent. These can
be approximated using the operating current parameters in the Specifications section:
Equation 33.
where:
- IOP_PWM_LS is the low-side operating current (selected for PWM
mode at 500 kHz)
- IOP_PWM_HS is the high-side operating current (selected for PWM
mode at 500 kHz)