Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2003-01-08
2003-12-09
Patel, Rajnikant B. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S274000, C363S097000, C327S538000
Reexamination Certificate
active
06661212
ABSTRACT:
FIELD OF INVENTION
The present invention relates to voltage regulators, and in particular, to wideband voltage regulators for use with microprocessor, microcontrollers or other like high-frequency devices in which suppression of current transients is desired.
BACKGROUND OF THE INVENTION
As the speed of high performance microprocessors increases, consistent with CMOS transistor feature size reductions, the required power supply voltage continues to shrink. Further, the increased load and higher processor speed results in more severe current transients on the microprocessor's power supply. For example, as microprocessors execute instructions, particularly at faster rates, severe transients can occur. These severe current transients, if not properly regulated, can cause noise on the power supply that can induce errors in the microprocessor.
Typically, extensive decoupling techniques, wherein capacitors are placed across the load between the supply and ground references, in combination with active voltage regulation, are used to supply the instantaneous charge required by the microprocessor under dynamic operation. On-chip decoupling, e.g., on the integrated die, generally takes excessive chip area and reduces reliability. Off-chip decoupling typically has limited effectiveness because of the parasitic inductance in the power supply leads. In addition, off-chip as well as on-chip active voltage regulation employing conventional circuit design approaches lacks the bandwidth to respond to fast load transients and typically has limited effectiveness because of the parasitic inductance in the power supply leads.
A conventional wideband voltage regulator
100
is illustrated in
FIG. 1
, wherein V
IN
is an input power supply, V
OUT
is a regulated output supply, V
CC
is a voltage source required to bias the regulator circuitry, and which may be common with input power supply V
IN
, V
REF
is a voltage reference which determines the regulated output voltage supply V
OUT
, and an amplifier
104
that comprises an output buffer amplifier having a gain G. During operation, load current supplied to regulated output supply V
OUT
is primarily drawn from the input power supply V
IN
. In addition, a closed loop differential transconductance amplifier
102
formed by transistors Q
1
and Q
2
senses the difference between output voltage V
OUT
and reference voltage V
REF
and, through its feedback arrangement, strives to minimize the difference between the two voltages, V
OUT
and V
REF
.
The effectiveness of a conventional wideband voltage regulator, such as regulator
100
, to respond to fast load transients is primarily a function of the small signal bandwidth of regulator
100
, the output impedance of output buffer amplifier
104
and the large signal slew rate performance of regulator
100
. With reference to
FIGS. 2 and 3
, which illustrates the response to fast load transients of regulator
100
, under severe fast load transients, e.g., state “B” in
FIG. 2
, input transconductance amplifier
102
formed by Q
1
and Q
2
can fully switch, and the reaction response of the voltage regulator
100
can then be initially limited by the large signal slew rate performance of amplifier
102
. Under this condition; the response of amplifier
102
becomes “slew rate limited” and the rate of change of the output voltage can react no faster than the ratio of I
0
/(2*C
COMP
). However, simply increasing the amplifier quiescent current (I
0
) will not allow improvement of the slew rate, since doing so will raise the open loop gain of amplifier
102
by the same factor. Thus, an equivalent increase in the compensation capacitor (C
COMP
) is required to achieve the same closed loop phase margin. Moreover, other techniques such as emitter degeneration, or the use of low g
m
FET devices, will slightly improve slew rate performance but at the cost of open loop gain required for regulation accuracy.
Accordingly, a need exists for a wideband voltage regulator which overcomes the problems of high current transients, and does not have the limitations of the prior art with respect to slew rate and regulation accuracy.
SUMMARY OF THE INVENTION
The method and circuit according to the present invention addresses many of the shortcomings of the prior art. In accordance with various aspects of the present invention, a wideband voltage regulator is provided which can provide suppression of fast transients. In accordance with an exemplary embodiment, a voltage regulator can include a boosting circuit and a sensing circuit. The boosting circuit can be suitably configured to boost the voltage regulator response, while the sensing circuit can determine when such a boost may be desired. Accordingly, the response of the voltage regulator can be accelerated to a fast load transient beyond the closed loop bandwidth limited response or the slew rate limited response of the voltage regulator.
In accordance with various exemplary embodiments, an exemplary voltage regulator can be configured with an active sensing circuit comprising a sensing amplifier with switch control outputs, and a boosting circuit comprising N stored charge sources and (3N−1) switches that are configured to accelerate the voltage regulators response to a fast load transient beyond the closed loop bandwidth limited or slew rate limited response of the voltage regulator. The stored charge sources can comprise various components, such as boost capacitors, additional power supplies, or actively biased devices.
In accordance with another aspect of the present invention, the sensing circuit can be configured in various manners. In accordance with an exemplary embodiment, a method for determining when the sensing circuit can switch the state of the stored charge sources can comprise a comparison of the output voltage of the regulator to a constant reference voltage. In accordance with another exemplary embodiment, the sensing circuit can switch the state of the stored charge sources by comparing the voltage drop across the parasitic inductance between the voltage regulator output and the load to a constant reference voltage, or by comparing the difference between the voltage drop across the parasitic inductance of the supply side and the ground return of the load. Further, the sensing circuit can be triggered on a one-shot basis with preset pulse width, or by any other suitable trigger methodology. Still further, a differential offset voltage can be added to the sense amplifier to suitably adjust or configure the sensitivity of the sensing circuit.
REFERENCES:
patent: 3908163 (1975-09-01), Gilmore
patent: 5471167 (1995-11-01), L'Hermite et al.
patent: 5479090 (1995-12-01), Schultz
patent: 5621627 (1997-04-01), Krawchuk et al.
patent: 5629608 (1997-05-01), Budelman
patent: 5847951 (1998-12-01), Brown et al.
patent: 5850113 (1998-12-01), Weimer et al.
patent: 5982156 (1999-11-01), Weimer et al.
patent: 6028417 (2000-02-01), Ang et al.
Patel Rajnikant B.
Primarion
Snell & Wilmer
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