Electrical transmission or interconnection systems – Miscellaneous systems – For particular load device
Reexamination Certificate
2002-12-19
2003-09-02
Riley, Shawn (Department: 2838)
Electrical transmission or interconnection systems
Miscellaneous systems
For particular load device
C713S300000
Reexamination Certificate
active
06614136
ABSTRACT:
BACKGROUND
The invention generally relates to a voltage regulation system having an inductive current sensing element.
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 the output voltage.
As an example, referring to
FIG. 1
, one type of switching regulator is a 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 switch control signal 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 duration called T
S
) of an inductor
14
. In each cycle
19
, the regulator
10
asserts, (drives high, for example) the V
SW
signal 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 (drives low, for example) 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 (i.e., the summation of the T
ON
and T
OFF
intervals) is called a duty cycle of the regulator and generally governs the ratio of the V
OUT
voltage to the V
IN
voltage. Thus, to increase the V
OUT
voltage, the duty cycle of the regulator 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 current mode control technique. 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 to produce an error voltage (called V
CNTRL
) that is used to control the levels of the V
OUT
voltage and the I
L
inductor current.
The controller
15
uses the V
CNTRL
voltage and a voltage (called V
CS
) that indicates the I
L
inductor current to produce the V
SW
switch control signal to control the switch
20
. More specifically, referring also to
FIG. 5
, the controller
15
may include a comparator
26
that compares the V
CNTRL
and V
CS
voltages. The V
CS
voltage is provided by a differential amplifier
24
that senses the voltage difference (called V
R
) across a current sensing resistor
29
that is coupled in series with the inductor
14
.
The output terminal of the comparator
26
may be coupled to a switch circuit
27
that generates the V
SW
switch control signal. As an example of one type of current mode control, the switch circuit
27
may keep the T
OFF
time interval constant and use the positive incline of the V
CS
voltage to control the duration of the T
ON
time interval. Thus, the T
ON
time interval ends when the V
CS
voltage reaches the V
CNTRL
voltage and begins at the expiration of the constant T
OFF
interval.
Due to the above-described arrangement, when the V
OUT
voltage increases, the V
CNTRL
voltage decreases and causes the duty cycle of the regulator
10
to decrease to counteract the increase in V
OUT
. Conversely, when the V
OUT
voltage decreases, the V
CNTRL
voltage increases and causes the duty cycle to increase to counteract the decrease in V
OUT
. When the average value, or DC component, of the I
L
current increases, the DC component of the V
CS
voltage increases and causes the duty cycle to decrease to counteract the increase in the I
L
current. Conversely, when DC component of the I
L
current decreases, the DC component of the V
CS
voltage decreases and causes the duty cycle to increase to counteract the decrease in the I
L
current. The switching frequency (i.e., 1/T
S
) typically controls the magnitude of an AC ripple component (called V
RIPPLE
(see FIG.
4
)) of the V
OUT
voltage, as a higher switching frequency typically reduces the magnitude of the V
RIPPLE
voltage.
The regulator
10
is a single phase regulator. However, multiple regulators may be coupled in parallel to form a multiple phase voltage regulation system. In this manner, the input terminals of the regulators are coupled together, and the output terminals of the regulators are coupled together. The energization/de-energization cycles of the regulators are controlled so that the cycles are interleaved, or phased, with respect to each other. Such an arrangement is desirable because the phasing ensures that the entire voltage regulation system operates at a higher frequency than the frequency of any of the individual regulators.
The current sensing resistor
29
may occupy a substantial amount of printed circuit board space, may contribute significantly to the cost of the voltage regulation system, and may dissipate a significant amount of power especially in a multiple phase voltage regulator system that includes a multiple number of regulators and current sensing resistors
29
.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.
REFERENCES:
patent: 5572735 (1996-11-01), Tanikawa
patent: 5916313 (1999-06-01), Brown
patent: RE37738 (2002-06-01), Brkovic
Intel Corporation
Riley Shawn
Trop Pruner & Hu P.C.
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