In-Rush Current Reduce Circuit
Original Publication Date: 1997-Jun-01
Included in the Prior Art Database: 2005-Apr-01
Publishing Venue
IBM
Related People
Abstract
In a Personal Computer (PC) Card, a small circuit is provided for effectively reducing in-rush current on a power supply line.
In-Rush Current Reduce Circuit
In a Personal
Computer (PC) Card, a small circuit is provided
for effectively reducing in-rush current on a power supply line.
In Fig. 1,
the area enclosed with the broken line shows the
in-rush current reduce circuit which is located between the input
power pin and the main circuit. The
differential circuit for the
input voltage (Vcc) is composed of C and
R, and Q is the P-channel
FET.
Referring to
Figs. 1 and 2, the signal (W1) is the differential
wave form of Vcc and is connected to the GATE of the FET. The
resistance between the SOURCE and the DRAIN of the FET (Rsd) depends
on the voltage between the SOURCE and
the GATE of the FET (Vsg = Vcc
- W1), as shown in Fig. 3. Therefore,
Rsd is high at the moment when
Vcc is supplied (Vsg = 0V), then decreases gradually according to
Vsg, and at last when Vsg = Vcc, it
becomes very low. The in-rush
current for the main circuit (I1) does
not flow at a time when Vcc
is supplied but flows gradually according to Vsg. The peak current
can be reduced effectively compared with
I2 that shows the in-rush
current without the circuit.