US3067380A - Transistor-operated regulating system for low voltage generators - Google Patents

Description

Dec. 4, 1962 P. ROSS! TRANSISTOR-OPERATED REGULATING SYSTEM FOR LOW VOLTAGE GENERATORS Filed May 5, 1960 tatcs My inventionrelates to an arrangement for regulating, by means of transistors, the voltage produced by a low voltage generator provided with a shunt energization, chiefly in the case of automobile dynamos.

My invention has more particularly for its object improvements in arrangements wherein the regulating circuit includes chiefly a power transistor acting on the generator energization field and a pilot transistor controlling said power transistor and which is sensitive to the signals detecting a variation from the desired voltage.

voltage regulating meansare known for rotary generators, wherein the control of the voltage is obtained through semi-conductive elements, such as transistors. Normally, in the case of generators with a shunt energizetion, saidregulat-ion is-obtained by means of a circuit including inseries with the field winding of the generator, the emitter and collector circuit of a power transistor of the p-n-p type, the base of which transistor is connected with the collector electrode of a pilot transistor of the same. type, the base electrode of which is, in its turn, subjected to the action ofthe control signal depending in their turn on the value of the voltage across the terminals of the generator.

Said arrangements act on the energization current in a manner such as will return the generator voltage to its original normal value, with a view to providing independence'of the voltage produced with reference to the speed of rotation of the machines.

it is known, furthermore, that with a view to controlling generators having a regulation curve under constant voltage and limited'intensity conditions, there may be provided an arrangement limiting the intensity and having for its purpose a breaking of the feed circuit when loading conditions arise which cannot be allowed, since they would prevent proper operation. of the machine. Such intensity-limiting means formaunit which is separated from theactual voltage regulator of the transistor type and it is consequently necessary to provide two separate apparatus and alarger space for their housing when it is not desired to omit the intensityelimitingmeans by an oversizing of the dynamo. machine.

Orr-the other hand,.the difiiculty of resorting to such arrangements'whichincorporate at least partly vibrating contact pieces is well-known. Firstly, the-regulation is poor andthis'leads unavoidably to-peaks in the waveform of regulated voltage with reference to time and, fur-thermore, the maximumenergizingcurrent consistent with a proper operation ofthe vibrating. contact-pieces is limited.

Now, an object of the present invention consists in removing the above-*nentioned drawbacks by providing a single-arrangement of a completely static type, which, uses onlysemi-conductiveelements in the circuitdetecting voltage variations, as wellas in the voltage-regulating circuit, while, furthermore, such an arrangement acts as a voltage regulator and as an int nsity-limiting.device.

The use of'semi conductive elements in the regulating circuit and. inr the circuits detecting variations in voltage removes the necessity of using vibrating contact-pieces and it allows also a moreaccurate control of the voltage of the generatontogether with a deletion, in the design of the dynamo, of thelimitation consisting in reducing the energizing current, whichleads to economy, simplicity in structure and an improved efiiciency.

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3,ii7,330 Patented Dec. 4, 1962 The arrangement according to the main feature of the invention includes, in combination with the circuit regulating the voltage by means of transistors, two control circuits, of which the first circuit detects any variation in the voltage, while the second circuit is sensitive to the maximum value of the current intensity and these two circuits form an electrical system operating entirely through the agency of transistors and include in common at least one element operating under a constant voltage characteristic with reference to the intensity and subjected to the voltage of the generator and a loading resistance associated with said element. This arrangement is such that, upon applying the drop in voltage arising across said resistance to a pilot transistor, the first circuit produces a return of the voltage to its normal value, while the second circuit imits the current to a predetermined value, these circuits operating either separately or simultaneously.

T here will now be described a preferred embodiment of the improved regulator system, reference being made to the accom anying drawings, the single figure of which is a wiring diagram of such a regulator system.

in said figure, G designates the generator which may be the dynamo of an automobile with a shunt energization, while B and W designate respectively the storage battery and the load inserted in parallel with the latter.

The field winding L is connected at one end with the negative terminal of the dynamo generator G and is inserted in series with the emitter and collector circuit of a power transistor T1 of the p-n-p type. The emitter electrode E1 of said transistor is connected with the positive terminal of the generator, while a crystal diode D1 is inserted in parallel with the energizing winding L.

The base B3 of thetransistor T1 is connected'with the collector C2 of a second transistor T2, which is of the same type as Ti and has its emitter E2 connected directly to the positive terminal or" the dynamo generator G. The collector C2 is, in contradistinction, connected with the negative terminal through the resistance R1.

The compound system including the elements T1, T2, R1 andDi, which are interconnected in the manner described, form the actual regulating circuit and their action on the field-winding L depends on the signal transmitted by the control circuit to the base B2 of the pilot transistor T2.

Such regulating circuits, and, particularly the output circuit passing through the emitter and the collector of the power transistor T1 oscillate automatically'when the voltage-regulating procedurehas begun, betweengan operative condition under a high resistance and an operative condition under a low resistance. The transistor T1 behaves, in fact, after the manner of a relaxation oscillator and the diode D1 behaves as a resistance of a practically indefinite value when the transistor T2 shows a low resistance, while its conductivity is excellent when said transistor is inoperative; This prevents the production of an excess voltage in the field winding of the dynamo machine as a consequence of a sudden modification in the current fed by the collector of the transistor T2 during the voltage-regulating procedure.

The circuit detecting the variations in voltage according to my invention includes in series the circuit elements constituted by the resistance R2, by the Zener diodeDZ and the loading'resistance R3. The ends of theresistances which are not connected with the diode D2 are connected respectively with the negative and with the positive terminal of .the dynamo generator, while a condenser C is inserted in parallel with the resistance R3.

The base B2 of the transistor T2 is connected with the point P through which-anode of the Zener diode D2 is connected with the resistance-R3. The diode inserted in the circuit in a direction in which it provides for its looking against operation, is locked and cannot carry any current until the voltage applied across its terminals has reached the breakdown value or so-called Zener voltage, While it becomes highly conductive when the voltage rises above said value. This limit value is selected near the normal operative voltage, as previously described.

In combination with said circuit adapted to detect variations in voltage, there is provided a circuit sensitive to maximum intensity and including in common with the first-mentioned circuit said Zener diode and the loading resistance R3. Said second circuit acts as an intensitylimiting device and it supplies, in fact, to the transistor base B2 a suitable signal, whenever the intensity obtained for the load has a tendency to rise above the maximum value which is to be fed by the dynamo.

The intensity-limiting circuit includes, in addition to said elements which are in common with the circuit detecting the variations in voltage, a further transistor T3 which is also of the p-n-p type and two resistances R4 and R5.

The base 33 of the transistor T3 is connected with a point I beyond the resistance R5 which is inserted in a line leading from the positive terminal of the generator dynamo to the battery.

The emitter E3 of the transistor T3 is connected with the above-mentioned point F in the detecting circuit and the collector C3 is connected through the resistance R4 With the point H connecting the diode D2 with the resistance R2, in a manner such that the output circuit, passing through the emitter and the collector of the transistor T3 and in series with resistance R4, lies in parallel with the Zener diode D2. The resistance R5 forms the intensity sensitive element and produces the biasing of the base B3.

Beyond the resistance R5 and between the point I and the positive terminal of the battery is inserted a current-making and breaking element D3 constituted, preferably, by a crystal diode and having for its object to prevent the battery from supplying current to the dynamo and regulating circuit, when the electromotive force of the battery rises above that of the dynamo.

The condenser C and the resistance R3, which are the elements common to both the control circuits which have just been described, form a low-pass filter adapted to damp any sudden modification in the signals, as may arise in the closed regulating mesh circuit and which may be propagated as waves in the voltage to be regulated. Furthermore, the condenser C supplies the circuit with a time constant which is more capable of ensuring a regulation of the voltage with a satisfactory accuracy within the entire range of the speeds possibly assumed by the dynamo.

The diagram is completed by a compensating circuit constituted by the transistor T4, which is also of the p-u-p type and by the voltage distributor constituted by the resistances R6 and R7 inserted in series.

This last circuit has for its object to compensate the drop in voltage arising through the load current, which drop is applied across the terminals of the system including the resistance R5 and the diode D3 inserted in series. The emitter electrode E of the transistor T4 is connected with the point M inserted between the resistances R6 and R7 of the voltage distributor, so that it is connected with the positive terminal of the dynamo through the resistance R6 and to the negative terminal of said dynamo through the resistance R7. The collector C4 is connected with the negative terminal through the resistance R2 and the base B4 is connected with the positive terminal of the battery.

The operation of the voltage-regulating arrangement thus described is as follows:

When starting and as long as the dynamo rotates at a low speed, the value of the voltage produced is lower than the desired predetermined running value of the voltage and, as already mentioned, the Zener diode D2 prevents the passage of current in the circuit R3D2 R2, which serves for detecting variations in voltage.

Consequently, the base B2 and the emitter E2 of the transistor T2 are at the same potential and thus, obviously, the circuit passing through the emitter and collector of the pilot transistor T2 has a conductivity reduced to a minimum, said minimum conductivity corresponding to blocking conditions. Therefore, the transistor T2 is locked against operation and the resistance Rll is the seat of only the current passing through the base of the transistor T1.

The value of the resistance R1 is selected in a manner such that the transistor T1 may be saturated, so as to provide a maximum conductivity in the emitter and collector circuit of the latter and, consequently, the dynamo is practically subjected to full energization.

The consequence thereof is that, during the dynamo starting procedure, and, generally speaking, for a rotation at a low speed, the detecting circuit is not fed with current and, consequently, the regulating circuit behaves in a manner such as to produce favorable conditions for the rapid obtaining of a stabilized voltage across the terminals of the dynamo.

Assuming now that the voltage at the brushes of the dynamo generator assumes a value larger than the predetermined value, for instance under the action of an increased speed of rotation of the dynamo armature, the Zener diode becomes then conductive and there is obtained across its terminals F and H, by reason of the characteristic properties of the diode, a voltage which is substantially constant, in spite of the modifications in the intensity of the current passing through said diode. Consequently, there is applied at the point P and thereby on the base B2 of the pilot transistor T2 a signal which depends on the excess voltage produced by the dynamo above the predetermined voltage value.

In fact, the greater the excess voltage the greater the current passing through the detecting circuit and the greater the drop in voltage across the resistance R3, Said drop in voltage corresponding to the difference in voltage arising between the emitter E2 and the base B2 of the transistor T2. As mentioned hereinabove, said conditions lead to operation of the transistor T2 in a manner such that the current from the collector C2 flowing through the resistance R1 biases the base B1 of the tran sistor Tl, so as to reduce the energizing current and thereby the voltage produced by the dynamo. This starts the voltage-regulating procedure.

The current-limiting means operate as follows: for the allowable values of the current delivered, the transistor T3 is biased so that it prevents the passage of the current and this leads to an absence of any control action on the regulating circuit. When, in contradistinction, the current produced by the dynamo reaches the predetermined limit value, the drop in voltage across the terminals of the resistance R5 is such that it releases the transistor T3 and leads it rapidly to its saturation point. Thus, the branch circuit lying in parallel with the Zener diode D2 and constituted by the emitter and collector circuit E3- C3 in series with the resistance R4 is now fed with current. This produces a sudden drop in voltage between the points F and H of the detecting circuit and to an increase in the drop in voltage across the resistances R2 and R3, while the voltage of the dynamo remains at its predetermined value.

The signal applied to the base B2 of the transistor T2 increases suddenly and its action is transmitted to the base B1 of the transistor T1 and, consequently, to the field Winding L, so as to reduce the energizing current and thereby the voltage at the brushes of the dynamo. The current produced cannot increase above the predetermined limit value and there is obtained a characteristic curve under constant voltage conditions with a bend corresponding to maximum load.

The compensating means ensure a compensation for the drop in voltage which varies with the load and which appears across the terminals of the system including the diode, D3 and the resistance R5. This compensation is obtained through the application of said drop in voltage to the circuit passing through the emitter and the base of the transistor T4, which is biased so as to be nonconductive in the absence of any generation of current.

When, in contradistinction, the dynamo produces current, said drop in voltage across R6D3 biases the base B4-of the transistor T4 in a manner such as to provide for a how of current in the circuit passing through the emitter E4 and the collector C4 of said transistor. Said current passes through the resistance R2 and produces a shifting of the potential at the point H towards the values which are less negative. The consequence is that the potential at the point P, which varies with reference to that at H by an amount equal to the unvarying voltage across the terminals of the Zener diode D2, is shifted in the. same direction. Finally, this means that the current passing through R3 is reduced and thereby the drop in voltage between E2 and B2 in the pilot transistor T2, while the current increases in the collector C2 of T2 and thereby the energization of the dynamo. This increased energization compensates perfectly the drop in voltage across the terminals-of D3R5 and thus the output voltage applied to the battery and to the utilizaion circuit remains constant, in spite of the variations of the current generated by the dynamo.

In. the case where the variation-detecting circuits act simultaneously, it is obvious that the voltage-regulating circuit, which forms always, as disclosed, the executive circuit, takesint-o account the difierent signals received by it, Which ensures a perfect regulation of the voltage as a function of the number of revolutions of the generator, or as .a function of the current intensity generated, or again, ofthe drop in voltage.

Another feature of the invention consists in the possibility of modifying thegauging of the voltage to be obtained, byv acting simply on the value of the resistance R3. Consequently,.if such aresistance is modified, it is possible to adjustthe regulated valuezofthe voltage as desired.

Aturther improvement with a view to increasing'the accuracy of such agauging is obtained through the incorporation of a potentiometric arrangement for regulating the bias applied to the base B2.of the pilottransistor T2.

Althoughthe invention has been described with reference to the accompanyingdiagram, it is obvious that various modifications and additions are possible Within the scope of the invention as defined in the accompanying claims. Thus, for instance, the resistance R3 defining the drop in voltage may be, in :all cases, associated With other elements, provided'the arrangement obtained forms alowpass filter. Furthermore, it is possible to substitute for the resistance R5 .a non-linear element.

What I claim is:

1. A-transistor-operated regulating system for a voltage generator provided with a shunt energization and connected with a battery comprising a power transistor, an energizing circuit for the generator controlled by said power transistor, a pilot transistor adapted to control the power transistor, control circuit means including a common section constituted by a resistance in series with an element adapted to -provide,"aoros-s-its terminals, a constant voltage, whatever may be the variations in the intensity fed to it, means for subjecting said common section to the output voltage of said generator, whereby the changes in voltage across said loading resistance are fed to the pilot transistor to return the voltage produced by the dynamo to its predetermined value, current flow sensitive means for subjecting said control circuit means to the current generated by the generator, and means for connecting said current fiow sensitive means to said resistance whereby control circuit means acts on the pilot transistor to limit said current to less than a predetermined value.

2. A transistor-operated regulating system for voltage generators provided with a shunt energization and connected with a battery comprising a power transistor, an

energizing circuit for the generator controlled by said power'transistor, a pilot transistor adapted to control the power transistor, two control circuits including a common section constituted by a loading resistancein series with a Zener diode and a second resistance, said diode being connected, through the loading resistance and through the second resistance, with the positive and negative terminals of the generator respectively and the diode terminal connected with the loading resistance being also connected with the base of the pilot transistor, means associated with the loading resistance to form a low-pass filter, static means whereby the drops in voltage across said loading resistance are fed through one control circuit to the pilot transistor to return the voltage produced by said generator to its predetermined value, means subjecting the other control circuit to the current generated by the generator, and staticmeanswhereby said other control circuit acts on the pilot transistor to limit said current below a predetermined'value.

3. A transistor-operated regulatingsystem'for low voltage generators provided'wi-th ,a'shunt energization and connected with a battery, chiefly 'fordynamos on'board automobiles, comprising a power'transistor, an energizing circuit forthe generator controlled'by said'power transistor, a pilot transistor adapted to control the power transistor, two control circuits including'a'common section constituted by a loading resistanceinserieswith a Zener diode and a second resistance, said diode being connected, through the loading resistance and through the second resistance, with the positive and negative terminals of the generator respectively and the diode'terminal connected to the loading resistance being alsoconnected to the base of the pilot transistor; acondenser inserted in parallel with the loading resistance to form a low-pass filter, means whereby the drops in voltage across said loading resistance arefed'through one control circuit to the pilot transistor to return the voltage produced'by said generator-to its predetermined'valne, means'subjecting the other control circuit to the current generatedby the generator, and

means whereby the said other control'circuit acts'onthe pilot transistor-to limit said current below a predetermined value.

4. A transistor-operatedregulating system forlow voltage generators provided With a shunt energization and connected witha battery, chiefly for dynamos on board automobile, comprising a power transistor, an energizing circuit for the generator controlled by said power transistor, a pilot transistor-adapted to control the power transistor, two controlcircuits including a common section constituted by a'loading resistance in series with-a Zener diode and a second resistance, said diode being connected, through the loading resistance and through the second resistance, with the positive and negative terminals of thegeneratorrespectivelyand thediode terminal connected with theloading-resistance being also connected with the base of the pilot transistor, static means whereby-thedrops in-voltage across said loading resistance are fed throughone-controlcircuit to the pilot transistor to return thevoltage produced by' said generator-to'its predetermined value, a further transistor inserted in'the other control circuit, a resist-ance'adapted to bias said transistor and inserted between the base of said further transistor and the positive terminal of the battery, on the one hand, and the positive terminal of the generator, on the other hand, the emitter of said further transistor being connected with the end of the Zener diode connected with the loading resistance, and a further resistance connecting the collector of said further transistor with the other terminal of the Zener diode connected with the second resistance of the common section, said further transistor acting on the pilot transistor to limit the generator current below a predetermined value.

5. A transistor-operated regulating system for low voltage generators provided with a shunt energization and connected with a battery, chiefly for dynamos on board automobiles, comprising a power transistor, an energizing circuit for the generator controlled by said power transistor, two control circuits including a common section constituted by a loading resistance in series with a Zener diode and a second resistance, said diode being connected, through the loading resistance and through the second resistance, with the positive and negative terminals of the generator respectively and the diode terminal connected with the loading resistance being also connected with the base of the pilot transistor, static means whereby the drops in voltage across said loading resistance are fed through one control circuit to the pilot transistor to return the voltage produced by said generator to its predetermined value, a further transistor inserted in the other control circuit, a resistance adapted to bias said transistor and inserted between the base of said further transistor and the positive terminal of the battery, on the one hand, and the positive terminal of the generator on the other hand, the emitter of said further transistor being connected with the end of the Zener diode connected with the loading resistance, and a further non-linear resistance connecting the collector of said further transistor with the other terminal of the Zener diode connected with the second resistance of the common section, said further transistor acting on the pilot transistor to limit the generator current below a predetermined value.

6. A transistor-operated regulating system for low voltage generators provided with a shunt energization and connected with a battery, chiefly for dynamos on board automobiles, comprising a power transistor, an energizing circuit for the generator controlled by said power transistor, a pilot transistor adapted to control the power transistor, two control circuits including a common section constituted by a loading resistance in series with a Zener diode and a second resistance, said diode being connected through the loading resistance and through the second resistance, with the positive and negative terminals of the generator respectively and the diode terminal connected with the loading resistance being also connected with the base of the pilot transistor, static means whereby the drops in voltage across said loading resistance are fed through one control circuit to the pilot transistor to return the voltage produced by said generator to its predetermined value, a further transistor inserted in the other control circuit, a biasing resistance adapted to bias said transistor and inserted between the base of said further transistor and the positive terminal of the battery, on the one hand, and the positive terminal of the generator, on the other hand, the emitter of said further transistor being connected with the end of the Zener diode connected with the loading resistance, a further resistance connecting the collector of said further transistor with the other terminal of the Zener diode connected with the second resistance of the common section, said further transistor acting on the pilot transistor to limit the generator current below a predetermined value, a semiconductor inserted between said biasing resistance and the base of the further transistor, on the one hand, and the positive terminal of the battery, on the other hand, to prevent discharge of the latter into the generator and its control circuits.

7. A transistor-operated regulating system for low voltage generators provided with a shunt energization and connected with a battery, chiefly for dynamos on board automobiles, comprising a power transistor, an energizing circuit for the generator controlled by said power transistor, a pilot transistor adapted to control the power transistor, two control circuits including a common section constituted by a loading resistance in series with a Zener diode and a second resistance, said diode being connected, through the loading resistance and through the second resistance, with the positive and negative terminals of the generator respectively and the diode terminal connected with the loading resistance being also connected with the base of the pilot transistor, static means whereby the drops in voltage across said loading resistance are fed through one control circuit to the pilot transistor to return the voltage produced by said generator to its predetermined value, means subjecting the other control circuit to the current generated by the generator, static means whereby said other control circuit acts on the pilot transistor to limit said current below a predetermined value, a voltage distributor provided with a medial tap and fed by the generator, and a compensating circuit for drops in voltage comprising a compensating transistor having a base, an emitter and a collector, the base of which is connected with the positive terminal of the battery, the collector of which is connected to the point of connection between the Zener diode and the second resistance in the common section and the emitter of which is connected with the medial tap.

8. A transistor-operated regulating system for a voltage generator provided with a shunt energization circuit and connected with a battery and a load comprising a power transistor, said energization circuit of said generator controlled by said power transistor, a pilot transistor adapted to control said power transistor, and a compensating transistorresponsive to load variations, first and second control circuits and a compensating circuit having a common section constituted by a loading resistance, in series with an element adapted to provide, across its terminals, a constant voltage, and another resistance, said element being connected through said loading resistance and through said another resistance to the terminals of said generator, said common section cooperating with said three circuits for detecting the voltage variations to be transferred to said pilot transistor, first static means whereby the drops in voltage across said loading resistance are fed through said first circuit to the pilot transistor to return the voltage produced by the generator to its predetermined value, means subjecting said second control circuit and said compensating circuit to the current generated by said generator, second static means whereby said second control circuit acts on the pilot transistor to limit said current below a predetermined value, and means whereby said compensating circuit acts through said common section on said pilot transistor to compensate for changes in voltage with load.

References Cited in the file of this patent UNITED STATES PATENTS 2,892,143 Sommer June 23, 1959

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