© by SEMIKRON / 2017-09-07 / Technical Explanation / SKiiP
4
Page 20/73
The left side shows the equivalent circuit diagram of the driver board with ground connections. The right
side shows an application example of the controller side.
5.2.3 External Power Supply
Table 5—2 shows the required features of an appropriate external power supply for a SKiiP
®
4.
Table 5—2: Requirements to the auxiliary power supply
Power supply
The maximum ratings for the supply voltage are given in the
SKiiP
®
4 data sheet on page 1 (refer to symbol Vs). The
supply voltage is defined at the SKiiP
®
4 input, not at the
controller output (voltage drop on connection cable)
Maximum rise time of 24V <2 s
Rated current 1,5 times of the maximum driver input current
Minimum peak current
2 times of the maximum driver input current
(At least 1,5A)
Please note: Do not apply switching signals during power up.
The external power supply requires the capability to feed a minimum inrush current into the SKiiP 4 at
start-up of the system without entering a fault state itself. Typically power supplies with fold-back
characteristic or hiccup-mode can create problems if insufficient over current margin is available. The
voltage has to rise continuously and without any plateau formation.
In order to ensure continuous operation and to have sufficient margin in case of overload it is
recommended to select the rated current of the external power supply sufficiently higher than the SKiiP’s
maximum specified input current (see symbol Is on page 2 of the corresponding SKiiP
®
4 datasheet).
If the power supply is able to provide a higher current, a peak current will flow in the first instant to mainly
charge the input capacitances on the driver. The peak current value will be limited only by the external
power supply and the effective impedances (e.g. cabling etc-) as present in the connection between power
supply and the SKiiP. It is recommended to avoid the paralleling of several customer side external power
supply units. Their different current limitations may lead to drops in the supply voltage and unpredictable
instable behaviour.
The formula given in the SKiiP
®
4 datasheet for calculating the supply current I
S
(page 2) consists of three
parts:
• The first part is the current consumption of the driver during standby. No switching signals are
applied. Consequently, no AC-current is flowing. The example below is given for a
SKiiP2414GB17E4 (I
SO
=260mA).
• The second part is the required current consumption of the driver during switching.
• The third part is the current consumption required by the integrated current sensor to compensate
the present value of the AC-current.
2
21
260
ACsws
IkfkmAI ⋅+⋅+=
consumption of integrated current sensor
Standby current consumption of the
driver
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