Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1999-09-07
2001-05-29
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S284000
Reexamination Certificate
active
06239585
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to power supplies for electric and electronic circuits. More particularly, the invention relates to a self-oscillating, switch-mode, DC to DC converter for implementation of hysteretic current-mode control.
BACKGROUND OF THE INVENTION
As disclosed in Froeschle U.S. Pat. No. 4,456,872, hysteretic current-mode control offers significant advantages for many applications. Hysteretic current-mode control offers the tightest and most accurate control of inductor current, is unconditionally stable regardless of duty cycle, and offers excellent transient response to step loads. It is also inherently load-current limiting. Other advantages include short-circuit-proof operation in buck-derived topologies, easy loop-stability design, absence of subharmonic oscillation, instantaneous peak-to-average inductor-current ratio, and the absence of a need for slope compensation for duty cycles above 50%.
Although hysteretic current-mode control offers many advantages, it has not yet achieved the widespread use which might be anticipated given the advantages it offers. This may be due to the fact that most hysteretic current-mode control circuits of the present state of the art are complex, requiring numerous components, with an accompanying significant cost disadvantage with respect to simpler, non-hysteretic arrangements. A hysteretic current-mode control circuit requiring fewer and simpler components would naturally be less expensive to design and manufacture, and would make the advantages of this mode of control available in more applications.
The present invention recognizes the need for a circuit for achieving hysteretic current-mode control which can be manufactured using a small number of simple components to form a low cost unit suitable for use in applications such as a low cost battery charger, a regulated voltage source in a battery operated electronic device or any other application requiring a low cost DC-to-DC converter, as more fully described below.
SUMMARY OF THE INVENTION
A DC-to-DC converter circuit according to one aspect of the present invention includes only 4 transistors or switches and operates so as to utilize hysteresis around the current switching thresholds. Such a circuit may be readily implemented in a very low cost integrated circuit (“IC”). A circuit according to one aspect of the present invention operates as a current source in a BOOST topology, with the output voltage, V
out
, greater than, the input voltage, V
in
with V
out
and V
in
having the same polarity. In another aspect, the present invention operates as a current source in a BUCK topology, with V
out
less than V
in
, with V
out
and V
in
having the same polarity. A circuit according to a further aspect of the present invention operates as a current source in an INVERTING topology, with V
out
opposite in polarity to V
in
, and of any absolute value relative to V
in
. A circuit according to another aspect of the present invention includes additional components and can be operated as a regulated voltage source in any of the aforementioned topologies with or without negative feedback.
Among the advantages of switch mode-designs such as those of the present invention are that they are inherently more efficient than linear-mode designs because the main power switching component is either in one of two states, fully ON (saturated) or fully OFF. In an ideal sense, both of these two states dissipate no power. In other words, the power switch can experience high voltage or high current, but never both simultaneously. Therefore, the potential for high operating efficiency exists. In real-world practically realizable devices, neither of these two states is perfectly achieved, so there is still some power loss. There is also power lost during the actual switching transition time from one state to the other. However, these losses are much less than those in a linear design. A linear design is one in which the ON-state of the power transistor is continuously variable from fully ON to fully OFF. In this mode of operation, it is possible to simultaneously have high levels of current and voltage on the power transistor, and therefore high power dissipation, and low power conversion efficiency.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.
REFERENCES:
patent: 3435320 (1969-03-01), Lee et al.
patent: 4008429 (1977-02-01), Phalan
patent: 4242629 (1980-12-01), Shvey
patent: 4456872 (1984-06-01), Froeschle
patent: 4862013 (1989-08-01), Konopka
patent: 4961006 (1990-10-01), Pace et al.
patent: 5341085 (1994-08-01), Ettes
patent: 5389871 (1995-02-01), Otake
patent: 5825163 (1998-10-01), Pontarollo
patent: 5949222 (1999-09-01), Buono
Priest & Goldstein PLLC
Sterrett Jeffrey
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