High bandwidth low dropout linear regulator

• US 5,191,278 A
• Filed: 10/23/1991
• Issued: 03/02/1993
• Est. Priority Date: 10/23/1991
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Carpenter, Brian A.
• Primary Examiner(s): Voeltz, Emanuel T.
• Application Number:
  US07/780,600
• Time in Patent Office: 496 Days
• Field of Search: 323/273, 323/274, 323/275, 323/276, 323/277, 323/278, 323/280
• US Class Current: 323/275
• CPC Class Codes: G05F 1/563 including two stages of regulation at least one of which is output level responsive, e.g. coarse and fine regulation
• 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
• CPC Class Codes: G05F 1/575 characterised by the feedback circuit

Abstract

A linear voltage regulator for regulating the voltage and current in a DC supply is described. The invention includes current and voltage sense elements. The outputs from the sensed elements are summed together as the gate input to an FET pass transistor which regulates the power supplied. The two feedback loops provide high bandwidth and improve dynamic response.

Claims

1. A linear regulator circuit for controlling the voltage applied from a power source to a load comprising:

a single reference voltage;

means, including a circuit element for sensing the current drawn by the load and generating a voltage across the circuit element proportional to the current, said current sensing means having an input connected to the source and, providing a first voltage output;

means for sensing voltage across the load said voltage sensing means having a first input connected to the load and a second input connected to the single reference source and providing a second voltage output;

means for summing the first and second voltage outputs from the current and voltage sensing means and providing a third output signal;

means for switching the first and second outputs as a function of frequency of the voltage sensing and current sensing means; and

means for regulating a power source, said regulating means responsive to the output of said summing means, whereby changes in the current drawn or voltage across a load change the resistance of said regulating means.

2. The linear regulator circuit as claimed in claim 1 wherein the regulating means is an FET pass device.

3. The regulator as claimed in claim 1 wherein said sensing means include operational amplifiers.

4. The circuit as claimed in claim 1 wherein said summing means include an operational amplifier.

5. The circuit as claimed in claim 1 wherein said regulating means and said current sensing means are integrated into a single integrated circuit.

6. The circuit of claim 1 wherein the voltage sensing means compares the voltage sensed across the load to the single reference voltage.

7. In a power supply for providing a voltage and current source to an electronic circuit, a circuit for regulating the voltage and current provided in the electronic circuit comprising:

a single reference voltage;

means for sensing the current drawn by the load and generating a voltage proportional to the load current, said current sensing means having an input across a resistor connected to the source and providing a first voltage output;

means for sensing the voltage across the load and generating a voltage proportional to the voltage across the load, said voltage sensing means having a first input connected to the load and a second input connected to the single reference voltage and providing a second voltage output;

means for summing the first and second voltage outputs from the current and voltage sensing means, respectively and providing an output signal;

means for switching the first and second outputs as a function of frequency of the voltage sensing and current sensing means; and

means for regulating a power source, said regulating means responsive to the output of said summing means, whereby changes in the current drawn or voltage across a load change the resistance of said regulating means.

8. The linear regulator circuit as claimed in claim 7 wherein the regulating means is an FET pass device.

9. The regulator as claimed in claim 7 wherein said sensing means include operational amplifiers.

10. The circuit as claimed in claim 7 wherein said summing means include an operational amplifier.

11. The circuit as claimed in claim 7 wherein said regulating means and said current sensing means are integrated into a single integrated circuit.

12. A high bandwidth, low dropout linear regulator for controlling the voltage applied from a power source to a load comprising:

a single reference voltage,

means including a first differential amplifier for sensing a voltage differential across a circuit element, which differential is proportional to the current drawn by the load, and providing a low constant gain to the voltage differential over a large bandwidth as a first output voltage,

means, including a second operational amplifier connected between the single reference voltage and the load for sensing the voltage across the load and providing a second voltage output, the amplifier having a first bandwidth at low frequencies which decreases with frequency so as to cross unity gain before the first amplifier crosses unity gain as a second output voltage,

means including a third operational amplifier for summing the first and second outputs and providing an increased third output voltage for increased current in the current sensing loop and reduced second output voltages,

means for switching the first and second outputs as a function of frequency of the voltage sensing and current sensing means; and

regulating means responsive to the third output for providing constant load voltages through large dynamic load current changes across a wide bandwidth and having a low dropout voltage.