Browse Prior Art Database

Nchannel Mosfet Composed Charge/Discharge Circuit in a NotebooK PC

IP.com Disclosure Number: IPCOM000115373D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Narita, I: AUTHOR [+2]

Abstract

Disclosed is a charge/discharge circuit composed of Nchannel (Nch) MOSFET in a Notebook PC. Normally, the resistance of Nch MOSFET is lower than that of Pch MOSFET. So, with this circuit, it is possible to reduce the heat emission caused by the current flowing into the circuit.

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Nchannel Mosfet Composed Charge/Discharge Circuit in a NotebooK PC

      Disclosed is a charge/discharge circuit composed of Nchannel
(Nch) MOSFET in a Notebook PC.  Normally, the resistance of Nch
MOSFET is lower than that of Pch MOSFET.  So, with this circuit, it
is possible to reduce the heat emission caused by the current flowing
into the circuit.

      Fig. 1 shows the conventional charge/discharge circuit used in
a Notebook PC.  While the battery is charged by the AC/DC adapter,
SW1, SW2 and SW3 are switched on.  SW1 is used to block the current
from the battery to the AC/DC adapter.  SW3 is used to block the
current flow from the AC/DC adapter to the battery.  SW2 is used to
block the current supply from the AC/DC adapter during the discharge
mode while discharging the battery even if the AC/DC adapter is
plugged in.  And each FET has the body diode as shown in Figs. 1 and
2.  SW1 and SW3 are Nch MOSFETs and SW2 is a Pchannel (Pch) MOSFET.
The charge pump circuit is necessary to generate the high voltage
(V[g]) to switch on SW1 and SW3 Nch FET ON.  In order to switch on
these FETs, the V[g]'s voltages have to be positive.  The source
voltages of these FETs are nearly the same as the AC/DC adapter's
voltage, and the battery's voltage respectively.  So, to generate the
higher voltage than the power supplies, the charge pump circuit is
necessary.  In the conventional circuit,  SW2 had to be the Pch FET,
because the charge pump circuit is not powere...