
© by SEMIKRON / 2019-07-23 / Technical Explanation / SKYPER
®
42 LJ R
PROMGT.1026/ Rev.7/ Template Technical Explanation
Page 20/35
4.11
External boost capacitors | Secondary side
The SKYPER
42 LJ R allows driving of semiconductor power modules with a gate charge (Q
G
) of up to
20µC per output. To stabilize the gate voltages V
G(on)
and V
G(off)
during the semiconductor switches the use
of boost capacitors per channel are recommended, if the connected gate charge is larger than 2.5µC. These
capacitors has to be placed as close as possible to the driver, as shown in Figure 15.
Figure 15: SKYPER
®
42 LJ R | Secondary side | Boost capacitors
The external boost capacitors can be calculated by following equation:
𝐶
𝐵𝑆𝑇(𝑃)
= 𝐶
𝐵𝑆𝑇(𝑁)
= 4
µ𝐹
µ𝐶
∙ 𝑄
𝐺
− 10µ𝐹 𝑓𝑜𝑟 2.5µ𝐶 < 𝑄
𝐺
≤ 20µ𝐶
Please note, when assembling boost capacitors at the secondary side, also boost capacitors has to be
assembled at the primary side, as shown in Figure 9.
𝐶
𝐵𝑆𝑇
= 𝐶
𝐵𝑆𝑇(𝑃)
= 𝐶
𝐵𝑆𝑇(𝑁)
SKYPER
®
42 LJ R
C
B
S
T
(N
)_
T
O
P
C
B
S
T
(P
)_
T
O
P
PWR_VS_P_TOP X100:03
PWR_GND_TOP X100:08
PWR_VS_N_TOP X100:10