Battery charger using a depletion mode transistor to serve as a current source

• US 20050275375A1
• Filed: 06/13/2005
• Published: 12/15/2005
• Est. Priority Date: 06/14/2004
• Status: Abandoned Application

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Liu, Jing-Meng, Pai, Chung-Lung, Su, Hung-Der
• Application Number:
  US11/150,191
• Publication Number:
  US 20050275375A1
• Time in Patent Office: Days
• US Class Current: 320/128
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries

Abstract

In a battery charger using a depletion mode transistor to serve as a current source, the depletion mode transistor is self-biased for generating a charging current to charge a battery, thereby requesting no additional control circuit to control the depletion mode transistor, reducing the circuit size, and lowering the cost.

Claims

1. A battery charger for supplying a charging current to charge a battery, the battery charger comprising:

a voltage detector for detecting a battery voltage to thereby determine a control signal;

a switch controlled by the control signal; and

a current source including a depletion mode transistor connected to the switch for being self-biased for generating the charging current.

2. The battery charger of claim 1, wherein the depletion mode transistor is a MOSFET.

3. The battery charger of claim 1, wherein the switch is an enhancement mode MOSFET.

4. The battery charger of claim 1, wherein the depletion mode transistor is a JFET.

5. The battery charger of claim 1, wherein the switch is an enhancement mode JFET.

6. The battery charger of claim 1, wherein the depletion mode transistor is a JFET, and the switch is an enhancement mode JFET.

7. The battery charger of claim 7, wherein the depletion mode transistor and switch are integrated in a chip.