Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Reexamination Certificate
2002-06-24
2003-08-19
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
Reexamination Certificate
active
06608520
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to a regulator circuit which regulates an output voltage to a desired voltage. More specifically, it pertains to a regulator circuit that functions to regulate an overcurrent.
BACKGROUND OF THE INVENTION
FIG. 5
is an outlined circuit diagram showing an configuration of a conventional series regulator having an overcurrent regulator circuit.
In the series regulator shown in
FIG. 5
, negative output terminal of DC voltage source Vin is connected to a ground line, and positive output terminal is connected to terminal N
1
of current detection resistor
3
. The other terminal N
2
of current detection resistor
3
is connected to the drain of n-type MOS transistor
1
. Smoothing capacitor CL and current load IL are connected between source N
3
of n-type MOS transistor
1
and the ground line.
In addition, resistors
2
a
and
2
b
for voltage detection are connected in series between source N
3
of n-type MOS transistor
1
and the ground line, and midpoint N
4
between them is connected to positive input terminal + of differential amplifier circuit
4
a
. Negative terminal − of differential amplifier circuit
4
a
is connected to the ground line by way of the positive terminal of voltage source VR
1
via its negative terminal. The difference in the voltage between said positive input terminal + and negative input terminal − is amplified by differential amplifier circuit
4
a
and input into base N
5
of npn transistor
4
c.
The emitter of npn transistor
4
c
is connected to the ground line, and the collector is connected to power supply line Vcc via constant-current circuit
4
b
as well as to base N
6
of npn transistor
4
d
. The collector of npn transistor
4
d
is connected to power supply line Vcc, and the emitter is connected to the ground line via constant-current circuit
4
e
. Said emitter is also connected to gate N
7
of n-type MOS transistor
1
.
Terminal N
2
of current detection resistor
3
is connected to negative input terminal − of comparator
5
a
. Terminal N
1
of current detection resistor
3
is connected to positive input terminal + of comparator
5
a
by way of the positive output terminal of voltage source VR
2
via its negative output terminal. A high-level or a low-level voltage in accordance with the result of a comparison of the voltage levels of said positive input terminal + and negative input terminal − is generated by comparator
5
a
and input into the gate of n-type MOS transistor
5
b
. Base N
6
of npn transistor
4
d
is connected to the ground line via the drain source terminal of n-type MOS transistor
5
b.
In the series regulator with the aforementioned configuration, the error between the detected value of the output voltage and its target value is amplified by differential amplifier circuit
4
a
and fed back negatively to the gate of n-type MOS transistor
1
in order to regulate the output voltage supplied to current load IL.
For example, when the voltage at source N
3
of n-type MOS transistor
1
increases, the voltage at node N
4
where said voltage is divided by resistors
2
a
and
2
b
also increases. Accordingly, output voltage of differential amplifier circuit
4
a
also increases, and collector current of npn transistor
4
c
increases, so that base voltage of npn transistor
4
d
drops. Therefore, emitter voltage of npn transistor
4
d
drops, and gate voltage of n-type MOS transistor
1
drops. As the gate voltage drops, the current between the drain and the source of the n-type MOS transistor is lowered, and the voltage of source N
3
drops.
Similarly, when the voltage of source N
3
of n-type MOS transistor
1
drops, output voltage of differential amplifier circuit
4
a
drops, base voltage of npn transistor
4
d
increases, and gate voltage of n-type MOS transistor
1
increases, so that the voltage of source N
3
also increases.
As described above, negative feedback is applied to the voltage of source N
3
of n-type MOS transistor
1
in order for the voltage at node N
4
and the voltage of voltage source VR
1
to become almost equal.
On the other hand, the circuit comprising current detection resistor
3
, voltage source VR
2
, comparator
5
a
, and n-type MOS transistor
5
b
is a circuit for regulating overcurrent, and it shuts off n-type MOS transistor
1
when the current in current detection transistor
3
has exceeded a fixed level.
When the current in current detection resistor
3
is sufficiently low, and the difference in the potential between terminal N
1
and terminal N
2
is smaller than the difference in the potential related to voltage source VR
2
, the voltage of positive input terminal + of comparator
5
a
is lower than that of negative input terminal −. Therefore, the output of comparator
5
a
becomes low-level, and n-type MOS transistor
5
b
is turned off.
When the current in current detection resistor
3
increases, and the difference in the potential between terminal N
1
and terminal N
2
becomes greater than the potential related to voltage source VR
2
, the voltage of positive input terminal + of comparator
5
a
becomes higher than that of negative input terminal −, and the output of comparator
5
a
becomes high-level. As a result, n-type MOS transistor
5
b
is turned on, and the base voltage of npn transistor
4
d
drops to that of the ground line. Accordingly, the gate voltage of n-type MOS transistor
1
also drops to that of the ground line, and n-type MOS transistor
1
is turned off.
FIG. 6
is a diagram showing the changes in output voltage when the overcurrent regulating function of the series regulator in
FIG. 5
is activated.
FIG. 6A
shows an example of a simulated waveform of the current in current load IL, wherein the vertical axis represents load current level, and the horizontal axis represents time. In addition,
FIG. 6B
shows an example of a simulated waveform of the output voltage supplied to current load IL, wherein the vertical axis represents output voltage level, and the horizontal axis represents time.
As shown by the output voltage waveform in
FIG. 6B
, when the current in current load IL is increased from 0 A to 5 A to activate the overcurrent regulating function, the series regulator falls into an oscillating condition in which the output voltage vibrates between 0V and 900 mV repeatedly if the output voltage is set at 0.9V.
In other words, if the potential of gate N
7
of n-type MOS transistor
1
drops to that of the ground line due to the overcurrent regulating function while under said oscillating condition, n-type MOS transistor is turned off, and the voltage of current detection resistor
3
drops. When the overcurrent regulating function is cancelled as a result, the output voltage starts increasing again, and the output current increases until the overcurrent regulating function is activated. As described above, in the case of the series regulator shown in
FIG. 5
, the overcurrent regulating function and the normal voltage control are repeated, resulting in the oscillation shown in FIG.
6
B.
Once the voltage oscillation shown in
FIG. 6B
occurs, those circuits supplied with said voltage may start operating abnormally. In addition, a large pulse-like current flows into smoothing condenser CL, resulting in a problem of deteriorated condenser characteristics.
The present invention was formulated in light of said situation, and its objective is to present a regulator circuit capable of preventing output voltage oscillation when the overcurrent regulating function is activated.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned goal, the regulator circuit of the present invention has a voltage output circuit which outputs a voltage in accordance with the level of a voltage control signal input, a voltage detection circuit which outputs a voltage detection signal of the level in accordance with the output voltage of the aforementioned voltage output circuit, a voltage control signal output circuit which selects either a
Brady W. James
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
Zweizig Jeffrey
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