Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-12-28
2002-08-13
Vu, Bao Q (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S274000, C323S303000
Reexamination Certificate
active
06433526
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of voltage regulators, and, more particularly, to voltage regulators of a type delivering a constant DC voltage while being supplied with a DC voltage prone to variation.
BACKGROUND OF THE INVENTION
Conventionally, a regulator which is required to output a voltage of 3.3 volts will be supplied with a DC voltage of about 5.1 to 9.5 volts. The upper limit of supply of a regulator depends essentially on the technology of the active components with which it is provided.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a voltage regulator which is not damaged when the voltage to which it is subjected exceeds the breakdown voltage of its active components.
A regulating device according to present the invention is supplied with a variable voltage V
v
and delivers a constant voltage for supplying consumer elements. The device may include a regulating element, a means or circuit for comparing the variable voltage V
v
with a reference voltage V
ref
, a means or circuit for dividing the variable voltage V
v
by a factor k
1
, and a switching means or circuit able to supply the regulating element with a voltage V
r
equal either to the variable voltage V
v
, or to the divided variable voltage V
v
/k
1
. The switching means may be controlled by the comparison means in such a way that the regulating element is supplied with the variable voltage V
v
if a voltage condition is satisfied and with the divided variable voltage V
v
/k
1
if the voltage condition is not satisfied. This is because the variable voltage V
v
is prone to take values greater than those which the active components of the device are capable of supporting.
Advantageously, the comparison means may include a means or circuit for dividing the variable voltage V
v
by a factor k
2
to obtain a comparison voltage V
comp
=V
v
/k
2
, and an amplifier arranged as a comparator receiving on one input the comparison voltage V
comp
and on another input the reference voltage V
ref
to output a control signal V
+
. The control signal V
+
may be of a conventional value
1
if the comparison voltage V
comp
is greater than the reference voltage V
ref
and of a conventional value
0
if the comparison voltage V
comp
is less than the reference voltage V
ref
.
The device may include an inverter at the output of the amplifier to obtain an inverse control signal V
−
. The means for dividing by the factor k
2
may include at least two resistors arranged in series between the variable voltage V
v
and ground. The means for dividing by the factor k
1
may include at least two resistors arranged in series between the variable voltage V
v
and ground. The means for dividing by the factor k
1
and the means for dividing by the factor k
2
may include at least one common resistor.
Advantageously, the switching means may include a first transistor, one terminal of which is connected to the input of the switching means and sees the variable voltage V
v
. Another terminal of the first transistor is connected to the output of the switching means and sees the voltage V
r
. A control terminal of the first transistor is linked to a control means or circuit generating a voltage able to turn on the first transistor if the voltage condition is not satisfied or to turn off the transistor if the voltage condition is satisfied. The first transistor may be a MOS transistor.
The switching means may also include at least one second transistor, one terminal of which is connected to the input of the switching means and sees the variable voltage V
v
. Another terminal of the second transistor is connected to the output of the switching means and sees the voltage V
r
. Furthermore, a control terminal of the second transistor sees a control voltage equal to the divided variable voltage V
v
/k
1
that is able to turn off the second transistor if the voltage condition is not satisfied and to turn on the second transistor if the voltage condition is satisfied. Thus, the voltage V
r
is equal to the divided variable voltage V
v
/k
1
. The second transistor may be replaced by a cascode arrangement of several transistors, for example bipolar transistors, to deliver more current at the output of the switching means.
Advantageously, the means for controlling the first transistor may include a third transistor controlled by an output voltage from the comparison means and a fourth transistor controlled by the inverse of the output voltage from the comparison means. The third transistor may be connected at one terminal to ground and at another terminal to the output of the switching means seeing the voltage V
r
by way of two resistors R
21
and R
22
in series. A common point shared by the two resistors sees the voltage V
r
if the voltage condition is not satisfied and a voltage equal to V
r
*R
21
/(R
21
+R
22
) if the voltage condition is satisfied.
The fourth transistor may be connected by one terminal to ground and by another terminal to the output of the switching means by a fifth transistor whose control terminal is connected to the common point shared by the two resistors. The fifth transistor may be on if the voltage condition is satisfied and off if the voltage condition is not satisfied so that the common point shared by the fourth and fifth transistors sees a voltage which is substantially
0
if the voltage condition is not satisfied and substantially equal to the voltage V
r
if the voltage condition is satisfied. The third and fourth transistors may be MOS transistors with their sources connected to ground. The fifth transistor may also be a MOS transistor with a source connected to the voltage V
r
.
Advantageously, the means for controlling the first transistor may furthermore include a sixth transistor having a terminal connected to the common point shared by the fourth and fifth transistors. The other terminal and the control terminal of the sixth transistor may be short circuited and linked to the output of the switching means seeing the voltage V
r
by two resistors R
27
and R
28
in series. The sixth transistor may be on if the voltage condition is not satisfied and off if the voltage condition is satisfied. The common point shared by the two resistors R
27
and R
28
sees the voltage V
r
*R
27
/(R
27
+R
28
) if the voltage condition is not satisfied and the voltage V
r
if the voltage condition is satisfied.
A seventh transistor is provided with a control terminal connected to the common point shared by the two resistors R
27
and R
28
. A terminal thereof may be connected to the common point shared by the fourth and fifth transistors. Another terminal of the seventh transistor may be connected to the common point shared by the fourth and fifth transistors by a resistor R
33
. Also, the remaining terminal of the seventh transistor may be connected to the control terminal of the first transistor of the switching means by a resistor R
32
. A resistor R
31
links the control terminal of the first transistor and the input of the switching means which sees the variable voltage V
v
.
This is done in such a way that the seventh transistor is on if the voltage condition is not satisfied (the control terminal of the first transistor being subjected to a voltage substantially equal to V
v
*R
32
/(R
31
+R
32
) able to turn it on) and that the seventh transistor is off if the voltage condition is satisfied (the control terminal of the first transistor being subjected to a voltage substantially equal to V
v
able to turn it off). The sixth transistor may be a bipolar transistor with short-circuited collector and base. The seventh transistor may be a bipolar transistor with the collector linked to the common point shared by the resistors R
32
and R
33
.
By way of example, a regulator may be embodied in HF
5
CMOS technology for which the breakdown voltage is about 15 volts. The general principle is to detect the voltage applied with respect to a threshold of 12.5 volts by a resistive bridge and a comparator, and to switch the regulating s
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Jorgenson Lisa K.
STMicroelectronics S.A.
Vu Bao Q
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