Battery charging apparatus

• US 20050024017A1
• Filed: 07/20/2004
• Published: 02/03/2005
• Est. Priority Date: 07/31/2003
• Status: Abandoned Application

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Lohr, Guenter
• Application Number:
  US10/895,221
• Publication Number:
  US 20050024017A1
• Time in Patent Office: Days
• US Class Current: 320/128
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

The battery charging apparatus is made with small and low-cost components. It includes a first transistor (T1) with a control input through which the charging current flows into a battery (B) and a current source (T3, T4, R1, R2) for a control current flowing to the control input of the first transistor. The current source sets or adjusts the control current so that the first transistor is non-conducting or blocked and the charging current flowing into the battery is shut off when a predetermined maximum charging voltage is reached at the battery.

Claims

1. An apparatus for charging a battery, said apparatus comprising

a first transistor (T1) with a control input, through which a charging current flows to a battery (B) connected to the first transistor when said battery (B) is being charged;

and

a current source (T3, T4, R1, R2) for a control current for said first transistor, said current source being connected to the control input of the first transistor (T1) to supply said control current;

wherein said current source comprises means for adjusting or setting said control current, so that the first transistor is non-conducting or blocked and said charging current flowing into said battery is shut off when a predetermined maximum charging voltage at said battery is reached.

2. The apparatus as defined in claim 1, further comprising a Zener diode (ZD) connected to the control input of the first transistor (T1), said Zener diode having a Zener voltage that is exceeded so that the control current no longer flows from said current source (T3, T4, R1, R2) to the control input of the first transistor (T1) but flows away through the Zener diode (ZD), as soon as said predetermined maximum charging voltage at said battery is reached.

3. The apparatus as defined in claim 1, further comprising a second transistor (T2) connected to said first transistor (T1), and wherein said second transistor keeps said control input of the first transistor (T1) at a potential that is less than the charging voltage of said battery (B) connected to the first transistor (T1) after blocking the first transistor (T1).

4. The apparatus as defined in claim 3, further comprising R/C circuit means (R4,C) for delaying a switching on of the second transistor (T2) and wherein said R/C circuit means is connected to a control input of the second transistor (T2).

5. The apparatus according to claim 1, further comprising a series circuit branch comprising a plurality of diodes (D1, D2, D3) and said first transistor (T1) connected in series with each other, and wherein said current source (T3, T4, R1, R2) is connected across said series circuit branch so that a voltage drop across said diodes drives said current source (T3, T4, R1, R2).