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Browse Prior Art Database

Battery Charge Pump with N-CH Mos FET

IP.com Disclosure Number: IPCOM000115219D
Original Publication Date: 1995-Apr-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Narita, I: AUTHOR [+2]

Abstract

This article describes a battery charge pump unit controlled by N-channel MOS FET. By using N-channel MOS FET for battery charge pump circuit, power loss wasted by DC-DC converter can be reduced drastically in comparison with the conventional ones using P-channel FET and/or Diode. This unit contributes battery life extension and decreasing heat generation on DC-DC converter.

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Battery

Charge Pump with N-CH Mos FET

      This article describes a battery charge pump unit controlled by
N-channel MOS FET.  By using N-channel MOS FET for battery charge
pump circuit, power loss wasted by DC-DC converter can be reduced
drastically in comparison with the conventional ones using P-channel
FET and/or Diode.  This unit contributes battery life extension and
decreasing heat generation on DC-DC converter.

      Fig. 1 shows the circuit which implements the subject
invention.  VIN is the power supplied from the AC-DC adapter, and
VBATT is the power supplied from the battery.  In this circuit, the
transistor (1) is switched on when VIN is supplied, accordingly the
P-channel FET (2) is switched on.  At this moment, 1 chip MPU (4)
provides the gate of the P-channel FET (3) with Low level signal, and
then the battery charge operation starts.  The circuits composed of
(1) and (2) can be replaced by Diode.  In either case, power loss at
this circuit is fairly big due to using P-channel FET or Diode.

      Fig. 2 shows battery a charge pump unit and control circuit
using N-channel MOS FETs (5) and (6).  To switch on the N-channel MOS
FET, Gate voltage 'VG' has to be higher than source voltage VIN and
VBATT.  Existing VG satisfying VG > VIN, VBATT, the battery can be
charged by the power from the AC-DC adapter while 'charge #' signal
is active.  The block enclosed with the dotted line, as shown in Fig.
2, corresponds to the circuit which makes...