Low drop-out voltage regulator apparatus

• US 5,510,697 A
• Filed: 06/01/1994
• Issued: 04/23/1996
• Est. Priority Date: 06/02/1993
• Status: Expired due to Term

• Current Assignee: VTech Telecommunications Limited (VTech Holdings Ltd.)
• Original Assignee: VTech Communications Incorporated (VTech Holdings Ltd.)
• Inventors: Dormer, Michael W.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US08/252,344
• Time in Patent Office: 692 Days
• Field of Search: 323/223, 323/226, 323/273, 323/274, 323/281, 323/282, 323/289, 323/312, 323/313
• US Class Current: 323/273
• CPC Class Codes: G05F 1/565 sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor G05F1/563 takes precedence

Abstract

A voltage regulator apparatus for regulating an unregulated voltage supply to in turn provide a regulated voltage. The voltage regulator apparatus includes a pass device, which has a control port, passes a portion of an unregulated voltage through to the regulated voltage output. The apparatus also includes a DC amplifier which provides a large closed loop gain to the regulated voltage output which is fed back to the pass device control port. The portion of the unregulated voltage passed to the regulated voltage output is a function of the output of the DC amplifier. The apparatus finally includes a voltage reference which provides a reference voltage to the DC amplifier. The DC amplifier voltage reference and pass device control port all draw the same operating current from the unregulated voltage supply. Thus, creating a sharp low-drop out characteristic for the voltage regulator apparatus.

Claims

1. A voltage regulator apparatus for regulating an unregulated voltage supply to in turn provide a regulated voltage, said voltage regulator apparatus comprising:

a pass device for passing a portion of said unregulated voltage supply through to said regulated voltage, said pass device having a control port;

DC amplification means for providing a large closed loop gain operably connected between said regulated voltage output and said control port, said portion of said unregulated voltage supply being passed to said regulated voltage output being a function of the output of said DC amplification means, as applied to said control port; and

voltage reference means operably connected to said DC amplification means for providing a reference voltage to said DC amplification means;

said DC amplification means, voltage reference means, and control port being driven by the same operating current from the unregulated voltage supply whereby when the unregulated voltage falls below the desired regulated voltage said voltage reference means sharply shuts off, in turn, shutting off said DC amplification means and said pass device.

2. The invention according to claim 1 wherein said pass device comprises an electrical valve.

3. The invention according to claim 1 wherein said pass device comprises a bipolar junction transistor.

4. The invention according to claim 1 wherein said voltage reference means is a band gap reference device.

5. The invention according to claim 1 wherein said voltage reference means is a zener diode.

6. The invention according to claim 1 wherein said voltage regulator apparatus is of the type constructed of bipolar junction transistors.

7. The invention according to claim 1 wherein said voltage regulator apparatus is of the type constructed of electrical valves.

8. The invention according to claim 1 wherein said voltage regulator apparatus is of the type constructed of field effect transistors.

9. A low drop-out voltage regulator apparatus for regulating an unregulated voltage supply to provide, in turn, a regulated voltage output, said voltage regulator apparatus comprising:

a first transistor having a first emitter, a first collector, and a first base, said first emitter being operably connected to said unregulated voltage supply, said first collector sourcing said regulator voltage output;

voltage divider means operably connected to said first collector for dividing said regulated voltage output into a setting voltage;

DC amplification means for providing a large closed loop gain, said DC amplification means operably receiving said setting voltage from said voltage divider means and providing an output to said first base of said first transistor; and

voltage reference means operably connected to said DC amplification means for providing a reference voltage to said DC amplification means;

said first base, DC amplification means and voltage reference means being in series and thus drawing the same operating current from the unregulated voltage supply whereby when the unregulated voltage falls below the desired regulated voltage said voltage reference means sharply shuts off, in turn, shutting off said DC amplification means and said first transistor.

10. The invention according to claim 9 wherein said voltage reference means is a band gap reference.

11. The invention according to claim 9 wherein said voltage reference means is a zener diode.