Mode configurable DC power supply

• US 5,777,462 A
• Filed: 08/15/1996
• Issued: 07/07/1998
• Est. Priority Date: 08/15/1996
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Inventors: Yue, Jingxing
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): JARDIEU, DEREK
• Application Number:
  US08/689,864
• Time in Patent Office: 691 Days
• Field of Search: 323/284, 323/285, 323/286, 323/287, 323/282, 323/283
• US Class Current: 323/285
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit

Abstract

A dual mode external DC power supply system for supplying DC power to an electronic device and which operates under the control of the electronic device is provided. The disclosed embodiment of the power supply system includes a first input adapted to receive an input signal of unregulated DC power, a second input adapted to receive a control signal from the electronic device, and an output adapted to provide either a constant voltage DC output signal or a constant current DC output signal depending on the magnitude of the control signal. The control signal also determines the level of constant current delivered to the electronic device when the system is operating in the constant current mode. The disclosed embodiment of the DC power supply system includes a regulating circuit responsive for conditioning the input signal of unregulated DC power into a DC output signal, a voltage sensing circuit adapted to provide a first feedback signal to the regulating circuit, a current sensing circuit also adapted to provide a second feedback signal to the regulating circuit, and a switch responsive to the control signal, for operatively coupling the first feedback signal to the regulating circuit when the system is operating in the constant voltage mode and coupling the second feedback signal when the system is operating in the constant current mode.

Claims

1. An electronic system comprising:

an external DC power supply system comprising;

an AC to DC converter;

a control signal input; and

a regulating circuit coupled to the AC to DC converter and to the control signal input, the regulating circuit including a DC power output, and generating a DC output signal at the DC power output in response to unregulated DC power from the AC to DC converter and a control signal from the control signal input, the regulating circuit including;

a switching circuit coupled to the control signal input, for operating the regulating circuit in a constant voltage mode in the event a magnitude of the control signal is within a first prescribed range, and for operating the regulating circuit in a constant current mode in the event the magnitude of the control signal is within a second prescribed range, and for selecting a selected level of constant current, in the event the regulating circuit is being operated in the constant current mode, as a function of the magnitude of the control signal within the second prescribed range; and

a portable electronic device comprising;

a control signal output detachably coupled to the control signal input of the external DC power supply system, for providing the control signal to the control signal input; and

a DC power input detachably coupled to the DC power output of the external DC power supply system.

2. The DC power supply system of claim 1 further comprising means for limiting a voltage of said DC output signal to a prescribed maximum voltage.

3. The DC power supply system of claim 1 wherein said regulating circuit further comprises:

a series switch transistor coupled to said AC to DC converter for receiving said unregulated DC power;

a pulse width modulated controller coupled to the series switch transistor, for conditioning said unregulated DC power into a pulse width modulated signal; and

a filtering circuit coupled to said series switch transistor, for rectifying said pulse width modulated signal into said DC output signal.

4. The DC power supply system of claim 1 further comprising means for limiting a current of said DC output signal to a prescribed maximum current.

5. The DC power supply system of claim 4 further comprising means for limiting a voltage of said DC output signal to a prescribed maximum voltage.

6. The DC power supply system of claim 1 wherein said regulating circuit further includes:

a voltage sensing circuit coupled to said DC power output, for sensing a voltage of said DC output signal and providing a voltage feedback signal; and

a current sensing circuit coupled to said DC power output, for sensing a current of said DC output signal and providing a current feedback signal;

wherein said switching circuit operates said regulating circuit in said constant voltage mode in response to the voltage feedback signal, and wherein said switching circuit operates said regulating circuit on said constant current mode in response to the current feedback signal.

7. The DC power supply system of claim 14 wherein said switching circuit further comprises a switch responsive to said control signal for coupling said voltage feedback signal to said regulating circuit when said regulating circuit is operating in said constant voltage mode and for coupling said current feedback signal to said regulating circuit when said regulating circuit is operating in said constant current mode.

8. The DC power supply system of claim 7 wherein said switching circuit comprises a comparator circuit coupled to said switch, for comparing said control signal to a reference voltage.

9. The DC power supply system of claim 8 wherein said control signal is coupled to said current sensing circuit and wherein said regulating circuit generates said DC output signal in response to said current feedback signal when said regulating circuit is operating in said constant current mode.