© by SEMIKRON / 2020-05-25 / Technical Explanation / SKYPER
®
12 PV
PROMGT.1026/ Rev.7/ Template Technical Explanation
Page 19/37
4.10
Gate resistors | Secondary side
Equipped with three output channels at each secondary side (TOP_ON/TOP_OFF/TOP_SOFTOFF and
BOT_ON/BOT_OFF/BOT_SOFTOFF) the SKYPER
®
12 PV driver offers the possibility to optimize turn-on and
turn-off behavior of the IGBT separately. By default, the driver uses the TOP_ON/TOP_OFF and
BOT_ON/BOT_OFF output to turn-on or turn-off the connected semiconductor. The SOFTOFF output will be
activated by the driver if a secondary side error event has been detected to turn-off of the connected
semiconductor slowly, which in turn shall prevent from excessive voltage overshoots to protect the
semiconductor against destruction by over voltage. It is mandatory to populate a suitable soft-off gate
resistor, otherwise the semiconductor will not be turned-off in case of a secondary side error. A detailed
explanation of when the driver is activating the soft-off path is referred in chapter 4.8.
The gate resistor influences the IGBT switching time, switching losses, reverse bias safe operating area
(RBSOA), short-circuit safe operating area (SCSOA), EMI, dV/dt, di/dt and reverse recovery current of the
freewheeling diode. The gate resistor essentially optimizes the safe operation of the power semiconductor
in accordance with the individual application parameters, e.g. IGBT technology, diode, switching frequency,
losses, application layout, inductivity / stray inductance, DC-link voltage and driver capability. The
complete design of an application must be viewed as a whole, with due considering of the above-mentioned
parameters at least. Interacting and interfering effects within the whole application must be considered,
evaluated and addressed. [4]
The minimum value of the gate resistors R
G(on)
and R
G(off)
could be calculated by the following equation:
𝑅
𝐺(min)
= 𝑅
𝐺
+ 𝑅
𝐺(𝑖𝑛𝑡)
+ 𝑅
𝐸
=
𝑉
𝐺(𝑜𝑛)
− 𝑉
𝐺(𝑜𝑓𝑓)
𝐼
𝑜𝑢𝑡(𝑝𝑒𝑎𝑘)
The minimum allowed value of the R
G(softoff)
is 1Ω. Additional hints how to determine the values of the gate
resistors are referred in [4].
Figure 14: SKYPER
®
12 PV | Secondary side | Gate resistors
Please note that some of SEMIKRON’s driver cores using an ASIC internal N-channel MOSFET for Soft Off.
To protect this MOSFET against stress when turning-off the TOP_ON/BOT_ON channel it is recommended to
place the R
G(softoff)
resistor in series with the R
G(off)
resistor.
Since each turn-on and turn-off of a semiconductor means charging or discharging the input capacitance of
the connected power semiconductor, the gate resistor has to be suitable for such pulse load. For this
reason, SEMIKRON recommends the use of pulse current suitable resistors. The following table provides
examples.
DC+
R
G(on)_TOP
R
G(softoff)_TOP
T1
SKYPER
®
12 PV
TOP_ON X100:05
TOP_OFF X100:06
TOP_SOFTOFF X100:09
PWR_GND_TOP X100:08
R
G(off)_TOP
AC
R
G(int)_TOP
R
E_TOP
IGBT
