Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
1998-10-27
2001-04-10
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S349000
Reexamination Certificate
active
06215289
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switchable d.c. voltage regulation circuit.
2. Discussion of the Related Art
Such a circuit is schematically shown in FIG.
1
and is referred to with reference
1
. It is connected by its input to a d.c. voltage Vin and outputs a voltage Vout which must remain as constant as possible when Vin varies or when the current Iout in a load L varies. This circuit is provided with a control input CTRL to output either voltage Vout or a zero voltage. An application of such a circuit is, in the automobile field, to supply a light-emitting diode or a chain of light-emitting diodes. Such light-emitting diodes can, for example, be used as the third tail light of a car. Thus, voltage Vin is the battery voltage of the vehicle and can vary significantly.
In the following, it will be assumed for simplification that voltage Vin and voltage Vout are positive voltages referenced to the ground.
FIG. 2
shows an elementary voltage regulation circuit. The voltage regulation is performed by an avalanche diode Z, the anode of which is grounded and the cathode of which is connected on the one hand to a regulated output terminal Vout and on the other hand to an input terminal Vin via a resistor R
1
. A switch such as a transistor TR
1
is arranged between terminal Vout and the ground. The base of this transistor receives control voltage CTRL. Thus, when the transistor is off, a voltage Vout substantially equal to the avalanche voltage of avalanche diode Z is present at the output. This circuit has several drawbacks. A first drawback is the presence of power resistor R
1
. If, for example, output voltage Vout has to be regulated to 10 V and voltage Vin rises to a value of 30 V, the voltage drop across the resistor will be on the order of 20 V and for a resistance of 50 ohms, a dissipated power of 1 Watt is reached. Such power resistors are expensive. Another drawback of the circuit of
FIG. 2
is that the current in avalanche diode Z is likely to greatly vary when voltage Vin varies. As a result, the output voltage variation can be significant.
Another series resistor assembly is illustrated in
FIG. 3. A
resistor R
1
is connected between terminals Vin and Vout as in FIG.
2
. An avalanche diode Z is connected between the collector and the base of transistor TR
1
, itself connected between Vout and the ground. A biasing resistor R
2
is connected between the base and the emitter of transistor TR
1
. In this case, the nominal regulation voltage is the voltage of the avalanche diode plus the base/emitter voltage of transistor TR
1
. The same drawback of use of a series resistor in the main current circuit appears in this assembly. An advantage with respect to the assembly of
FIG. 2
is that voltage Vout varies less with the variations of voltage Vin.
To avoid the drawbacks of circuits with a series resistor, circuits in which a semiconductor component, generally less expensive than a power resistor, is arranged in the branch in series between input terminal Vin and output terminal Vout have also been provided in prior art. This semiconductor component further enables to interrupt the current in the power branch and thus to limit losses during phases where a zero output voltage is desired.
FIG. 4
shows an example of a circuit with a gate turn-off (GTO) thyristor. A GTO thyristor Th
1
is connected by its anode to terminal Vin and by its cathode to terminal Vout. A resistor R
3
is connected between the anode gate and the cathode gate. The cathode gate is grounded via an avalanche diode Z and possibly a forward-biased diode d to perform a temperature compensation function. A transistor TR
2
is connected between the cathode gate of thyristor Th
1
and the ground. The base of transistor TR
2
is connected to a control terminal CTRL. When the transistor is off, the thyristor is normally on under the effect of its gate biasing due to resistor R
3
. Output voltage Vout is regulated to the cathode/gate voltage drop plus the voltage of avalanche diode Z. When transistor TR
2
is turned on, the thyristor turns off and voltage Vout becomes substantially zero. The anode gate could also not be used, and resistor R
3
could be directly connected to the thyristor anode. The assembly shown has the advantage of ensuring protection in case of an inversion of the biasing of voltage Vin, which can occur when the voltage source corresponds to an automobile battery.
Another circuit with a semiconductor component is shown in FIG.
5
. Thyristor Th
1
is replaced with a transistor TR
3
. The other circuit elements are similar to those of FIG.
4
. This circuit notably has the disadvantage of requiring a transistor with a relatively high gain, which is relatively difficult to obtain in the case of a power transistor with a high direct breakdown voltage.
SUMMARY OF THE INVENTION
Thus, the present invention aims at implementing a circuit of the same family as those of
FIGS. 4 and 5
, that is, in which the connection between the input and output terminals is performed by a semiconductor component, but having a better voltage regulation than known circuits.
Another object of the present invention is to implement such a circuit which is simply integrable in the form of a single semiconductor component.
To achieve these and other objects, the present invention provides a switchable d.c. voltage regulation circuit having an input terminal, an output terminal, a reference terminal, and a control terminal, including a gate turn-off thyristor, the main terminals of which are connected to the input terminal and to the output terminal, respectively; a resistor connected between the input terminal and the cathode gate of the thyristor; a transistor, the main terminals of which are connected to the cathode gate of the thyristor and to the reference terminal, respectively; and an avalanche diode connected between the output terminal and the base of the transistor.
According to an embodiment of the present invention, the resistor is connected between the anode gate and the cathode gate of the thyristor.
The present invention also aims at a monolithic component to implement the above circuit, including an N-type substrate divided in two wells by P-type insulating walls, the thyristor being implemented in a first well in lateral form, the transistor being implemented in a second well in vertical form, and the avalanche diode being implemented by the junction between an N
+
-type region and the base region of the transistor.
According to an embodiment of the present invention, the rear surface of the well including the thyristor includes a P
+
-type diffused region.
According to an embodiment of the present invention, this component includes, on its rear surface side, an insulating layer under the insulating walls.
According to an embodiment of the present invention, the resistor is formed of a lightly-doped P-type layer in contact with the cathode gate region.
The foregoing objects, features and advantages of the present invention, will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings.
REFERENCES:
French Search Report from French Patent Application 97 13987, filed Oct. 31, 1997.
Sanchez, J.L.: “Light Triggered Thyristor With A MOS Amplifying Gate: An Example Of Functionally Integrated Vertical High Voltage Power Device” Proceedings Of The European Solid State Device Research Conference (ESSDERC), Leuven, Sep. 14-17, 1992, No. Conf. 22, Sep. 14, 1992, Maes H.E.; Mertens R.P.; Van Overstraeten R.J., pp 145-148.
Berriane R., et al. “MOS-Gated Optically Triggered Thyristor” A New Galvanially Insulated High Voltage Integrated Switch Solid State Electronics, vol. 39, No. 6, Jun. 1996, pp 863-869.
Galanthay Theodore E.
Morris James H.
Patel Rajnikant B.
STMicroelectronics S.A.
Wolf Greenfield & Sacks P.C.
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