Apparatus for controlling battery discharge

• US 5,694,020 A
• Filed: 01/26/1996
• Issued: 12/02/1997
• Est. Priority Date: 09/26/1991
• Status: Expired due to Term

• Current Assignee: Braun GmbH (The Procter & Gamble Company)
• Original Assignee: Braun Aktiengesellschaft
• Inventors: Lang, Gerhard, Wolf, Jurgen
• Primary Examiner(s): TSO, EDWARD H
• Application Number:
  US08/592,113
• Time in Patent Office: 676 Days
• Field of Search: 320/13, 320/31, 320/39, 320/48
• US Class Current: 30/45
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02P 3/08 for stopping or slowing a dc motor
• CPC Class Codes: H02P 7/29 using pulse modulation
• CPC Class Codes: Y10S 388/937 Hand tool

Abstract

The invention is directed to an electrical device in which an electrical load is powered by a battery via an electronic switching device. A display means serves the function of indicating the charge status of the battery, and a time measurement means determines the connection time of the load to the battery. Following expiration of a predetermined connection time of the load to the battery, when the display means indicates the charge status "zero", the time measurement means will disconnect the electrical load from the battery by means of the electronic switching device.

Claims

1. Battery powered electrical shaver or hair cutter comprising cutter apparatus, a motor for driving said cutter apparatus, said motor being adapted to be powered by a battery, and circuitry operative upon detection of a defined discharging condition of said battery for reducing power to said motor in multiple steps or continually so that its rotational frequency is reduced down to zero in steps or continually to limit risk that hairs can be snagged.

2. The electrical shaver of claim 1, wherein said circuitry reduces said rotational frequency of said motor linearly with time.

3. The electrical shaver of claim 1 wherein said circuitry reduces said rotational frequency of said motor similarly to a curve of a falling battery voltage shortly before complete depletion.

4. The electrical shaver of claim 1, wherein said circuitry includes an electronic switching device and a pulse duration modulator for reducing the pulse duty factor of the control voltage for said electronic switching device, so that the rotational frequency of said motor is reduced in steps or continually down to zero.

5. The electrical shaver of claim 4, wherein said circuitry reduces said rotational frequency of said motor linearly with time.

6. The electrical shaver of claim 4 wherein said circuitry reduces said rotational frequency of said motor similarly to the curve of a falling battery voltage shortly before complete depletion.