Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-06-26
2002-11-26
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
Reexamination Certificate
active
06487093
ABSTRACT:
BACKGROUND
The invention generally relates to a voltage regulator, such as switching voltage regulator, for example.
A DC-to-DC voltage regulator typically is used to convert a DC input voltage to either a higher or a lower DC output voltage. One type of voltage regulator is a switching regulator that is often chosen due to its small size and efficiency. The switching regulator typically includes one or more switches that are rapidly opened and closed to transfer energy between an inductor (a stand-alone inductor or a transformer, as examples) and an input voltage source in a manner that regulates an output voltage.
As an example, referring to
FIG. 1
, one type of switching regulator is a synchronous Buck switching regulator
10
that receives an input DC voltage (called V
IN
) and converts the V
IN
voltage to a lower regulated output voltage (called V
OUT
) that appears at an output terminal
11
. To accomplish this, the regulator
10
may include a switch
20
(a metal-oxide-semiconductor field-effect-transistor (MOSFET), for example) that is operated (via a voltage called V
SW
) in a manner to regulate the V
OUT
voltage, as described below.
Referring also
FIGS. 2 and 3
, in particular, the switch
20
opens and closes to control energization/de-energization cycles
19
(each having a constant duration called T
S
) of an inductor
14
. In each cycle
19
, the regulator
10
asserts, or drives high, the V
SW
voltage during an on interval (called T
ON
) to close the switch
20
and transfer energy from an input voltage source
9
to the inductor
14
. During the T
ON
interval, a current (called I
L
) of the inductor
14
has a positive slope. During an off interval (called T
OFF
) of the cycle
19
, the regulator
10
deasserts, or drives low, the V
SW
voltage to open the switch
20
and isolate the input voltage source
9
from the inductor
14
. At this point, the level of the I
L
current is not abruptly halted, but rather, a diode
18
begins conducting to transfer energy from the inductor
14
to a bulk capacitor
16
and a load (not shown) that are coupled to the output terminal
11
. During the T
OFF
interval, the I
L
current has a negative slope, and the regulator
10
may close a switch
21
to shunt the diode
18
to reduce the amount of power that is otherwise dissipated by the diode
18
. The bulk capacitor
16
serves as a stored energy source that is depleted by the load, and additional energy is transferred from the inductor
14
to the bulk capacitor
16
during each T
ON
interval.
For the Buck switching regulator, the ratio of the T
ON
interval to the T
S
interval, called a duty cycle, generally governs the ratio of the V
OUT
to the V
IN
voltages. Thus, to increase the V
OUT
voltage, the duty cycle may be increased, and to decrease the V
OUT
voltage, the duty cycle may be decreased.
As an example, the regulator
10
may include a controller
15
(see
FIG. 1
) that regulates the V
OUT
voltage by using a pulse width modulation (PWM) technique to control the duty cycle. In this manner, the controller
15
may include an error amplifier
23
that amplifies the difference between a reference voltage (called V
REF
) and a voltage (called V
P
(see FIG.
1
)) that is proportional to the V
OUT
voltage. Referring also to
FIG. 5
, the controller
15
may include a comparator
26
that compares the resultant amplified voltage (called V
C
) with a sawtooth voltage (called V
SAW
) and provides the V
SW
signal that indicates the result of the comparison. The V
SAW
voltage is provided by a sawtooth oscillator
25
and has a constant frequency (i.e., 1/T
S
).
Due to the above-described arrangement, when the V
OUT
voltage increases, the V
C
voltage decreases and causes the duty cycle to decrease to counteract the increase in V
OUT
. Conversely, when the V
OUT
voltage decreases, the V
C
voltage increases and causes the duty cycle to increase to counteract the decrease in V
OUT
.
Significant power losses of the regulator
10
may be attributable to the power that is dissipated by the switch
20
. Ideally, the product of a voltage (called V
C
) across the switch
20
arid a current (called I
IN
) through the switch
20
should be zero because V
1
is ideally zero when the switch
20
is closed, and I
IN
is ideally zero when the switch is open. However, referring to
FIGS. 4 and 6
, significant switching losses typically occur in a time interval
30
when the switch
20
transitions from the closed state to the open state and a time interval
31
in which the switch
20
transitions from the open state to the closed state due to the overlapping nonzero V
1
voltage and I
IN
current during the time intervals
30
and
31
. A snubber circuit may be used for purposes of reducing the level of the V
1
voltage (to reduce power losses) during the time intervals
30
and
31
. However, the snubber circuit typically reduces the efficiency of the regulator
10
.
Also contributing to power losses across a switch (especially a switch that is coupled to a transformer) of a given regulator may be a voltage spike that occurs across the switch when the switch turns off. Besides introducing switching power losses, the voltage spike may also reduce the lifetime of the switch. Typically, the voltage spike is attributable to leakage inductances in the regulator. In this manner, when the switch opens, the currents through the effective leakage inductor is abruptly halted, giving rise to the voltage spike. A snubber circuit may be used for purposes of dampening the magnitude of the voltage spike. However, the snubber circuit may reduce the efficiency of the regulator.
For purposes of converting an AC wall voltage into regulated DC voltages for components
2
(see
FIG. 1
) of a computer system
1
, the regulator
10
may form the second of three stages of a power supply
3
for the computer system
1
. A boost switching converter, or voltage regulator
7
, may be used for the first stage. The boost voltage regulator
7
converts a rectified AC input voltage (received via input lines
5
) into a high DC voltage and shapes the input line current making its harmonic content compliant with various standards. The regulator
10
may be used to convert the high DC voltage that is generated by the boost voltage regulator
7
into comparatively low, isolated and regulated DC voltages (12V, 3.3V and 5V DC voltages, as examples) for power distribution in the computer system
1
. The third stage may be a DC-to-DC isolated voltage regulator, typically called a voltage regulator module (VRM), that converts the DC voltages that are furnished by the regulator
10
into lower voltages (1.2V to 2V voltages, as examples) that the VRM
17
tightly regulates and provides via power distribution lines
19
to the components
2
of the computer system
1
. Unfortunately, the above-described three stage design may introduce inefficiency; introduce reliability and size problems; and add significant costs that are associated with the power supply
3
.
Thus, there is a continuing need for an arrangement that addresses one or more of these problems.
REFERENCES:
patent: 5386359 (1995-01-01), Nochi
patent: 5694392 (1997-12-01), Faulk
patent: 5929606 (1999-07-01), Faulk
patent: 5982638 (1999-11-01), Tang et al.
Intel Corporation
Patel Rajnikant B.
Trop Pruner & Hu P.C.
LandOfFree
Voltage regulator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Voltage regulator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Voltage regulator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2921566