Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-06-30
2001-11-27
Patel, Rajnikant B. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S313000, C327S513000
Reexamination Certificate
active
06323628
ABSTRACT:
TECHNICAL FIELD
The present invention relates, in general, to voltage regulators that develop a regulated output voltage in response to a bandgap voltage reference and, in particular, to a voltage regulator that establishes bandgap voltage reference and achieves output voltage regulation with a single feedback loop.
BACKGROUND OF THE INVENTION
A voltage regulator accepts an unregulated and noisy supply voltage as an input and generates an accurate and well-defined output voltage with a rated current capacity. Generally, conventional voltage regulators consist of two functional parts, namely a bandgap voltage reference generation circuit and a voltage regulation circuit.
FIG. 1
shows a conventional voltage regulator. In the
FIG. 1
voltage regulator, each of the two parts has a separate feedback loop, where the noise and inaccuracy of each part cumulatively degrades the final, regulated output voltage.
U.S. Pat. No. 5,686,821 to Brokaw discloses a voltage regulator that has a single feedback loop. A defined bandgap voltage is not required in this voltage regulator. Instead, a separate proportional to absolute temperature voltage sensing stage is included along with a high-gain transconductance amplifier having an input offset voltage that cancels the proportional to absolute temperature voltage generated in the proportional to absolute temperature voltage sensing stage. The voltage regulator of U.S. Pat. No. 5,686,821 relies heavily on the accurate cancellation in one stage of the proportional to absolute temperature voltage generated in a different stage. In addition, the design of the voltage regulator of U.S. Pat. No. 5,686,821 requires a very high-gain transconductance amplifier to achieve the strong feedback loop required for accurate voltage regulation.
SUMMARY OF THE INVENTION
To overcome the shortcomings of prior art voltage regulators, a new and improved voltage regulator is provided by the present invention. One object of the present invention is to provide a new and improved voltage regulator. Another object of the present invention is to provide a voltage regulator that has improved efficiency. A further object of the present invention is to provide a voltage regulator that has improved accuracy. Yet another object of the present invention is to provide a voltage regulator that does not suffer from error accumulation.
A voltage regulator, constructed in accordance with the present invention, includes a proportional to absolute temperature current mirror having first and second current branches for establishing a bandgap voltage when current flow through the first and second current branches is equal and a resistor string coupled to the proportional to absolute temperature current mirror and responsive to the bandgap voltage for developing a regulated voltage from the bandgap voltage that is supplied to a load. Also included in this voltage regulator are output means between the proportional to absolute temperature current mirror and the resistor string for supplying output current to the load while maintaining the regulated voltage constant and an inverting gain stage coupled to the proportional to absolute temperature current mirror for sensing relative current flow through the first and second current branches in the proportional to absolute temperature current mirror and for controlling the output means to maintain the regulated voltage constant. A voltage regulator, constructed in accordance with the present invention, further includes a start up circuit responsive to the regulated voltage and coupled to the proportional to absolute temperature current mirror for initiating current flow through the first and second current branches in the proportional to absolute temperature current mirror.
It is to be understood that the foregoing general description of the invention and the following detailed description of the invention are exemplary, but are not restrictive of the invention.
REFERENCES:
patent: 5241261 (1993-08-01), Edwards et al.
patent: 5309083 (1994-05-01), Pierret et al.
patent: 5424628 (1995-06-01), Nguyen
patent: 5559425 (1996-09-01), Allman
patent: 5686821 (1997-11-01), Brokaw
patent: 5731696 (1998-03-01), Pennisi et al.
patent: 5737170 (1998-04-01), Moyer
patent: 5796244 (1998-08-01), Chen et al.
Abate Esq. Joseph P.
International Business Machines - Corporation
Patel Rajnikant B.
Ratner & Prestia
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