US3808467A

US3808467A - Effective voltage stabilizer

Info

Publication number: US3808467A
Application number: US00314456A
Authority: US
Inventors: Y Kawashima
Original assignee: NipponDenso Co Ltd
Current assignee: Denso Corp
Priority date: 1971-12-14
Filing date: 1972-12-12
Publication date: 1974-04-30
Anticipated expiration: 1991-04-30
Also published as: JPS5320100B2; JPS4864454A

Abstract

An effective-voltage stabilizer including an output transistor for switching an input DC voltage, the stabilizer comprising a charging - discharging circuit connected to the output side of said output transistor and consisting of a capacitor and resistors, and a switching controlling circuit for detecting a voltage appearing across the capacitor in said charging discharging circuit and on-off controlling said output transistor according to the detected voltage, thereby generating a squarewave output from said output transistor and stabilizing the effective-voltage of said square-wave output.

Description

United States Patent [19 Kawashima [75] Inventor:

[73] Assignee: Nippondenso Co., Ltd., Kariya-shi, Aichi-ken, Japan 22 Filed:. noo.12,1972

211 Appl. No.: 314,456

30 Foreign Application Priority. Data 3,571,626 3/1971 Reif .fi 307/290 3,582,762 6/1971 Mori 317/234 H 3,671,852 6/1972 Ritzenthaier 307/297 3,707,635 12/1972 Kawashima 307/297 Primary Examiner Andrew J. James Attorney, Agent, or FirmCushman, Darby &

Cushman [57] ABSTRACT Dec. 14, 1971 Japan 46-101718 An effectivewoltge stabilizer including an output transistor for switching an input DC voltage, the stabi- [52] US. C1 307/297, 307/234, lizer comprising a charging discharging circuit com Int CI p 3 03k v nected to the output side of said output transistor and l consisting ofa capacitor and resistors and a switching [58] Flew of Search 7 2515 3 controlling circuit for detecting a voltage appearing across the ca acitor in said char 'n dischar in cir- P 3 g g g cuit and on-off controlling said output transistor ac- {561 References cued cording'to the detected voltage, thereby generating 21 UNITED STATES PATENTS square-wave output from said output transistor and 3,265,956 8/1966 Schlabach.....- 308/297 X stabilizing the effective-voltage of said square-wave 3,286,157 11/1966 output. 3,321,698 5/1967 3,368,139 2/1968 Wuerflein 307/297 x 8 Claims, 7 Drawing Figures PATENTEDAPRBU mm SHEET 1. OF 2 F I I PRIOR ART I &3 5 71:1 8 5 FIG. 2 PRICXR ART EFFECTIVE VOLTAGE STABILI'ZER FIELD OF THE INVENTION This invention relates to a voltage stabilizer and more particularly to an effective-voltage regulator for generating a square-wave output which has a regulated effective-voltage.

SUMMARY OF THE INVENTION An object of the present invention is to provide a voltage stabilizer in which the effective-voltage of a square-wave output is controlled constant and hence the power consumption in an output transistor for controlling an input voltage is decreased.

Another object of the present invention is to provide a voltage stabilizer which is easily fabricated in an IC circuit form and have long service life.

A further object of the present invention is toprovide a voltage stabilizer capable of stabilizing the effectivevoltage of a square-wave output with practical accuracy.

According to an embodiment of the present invention, there is provided an effective-voltage stabilizer comprising an output transistor for on-off controlling an input voltage to generate a square-wave output, an

output voltage compensating circuit for voltagecompensating, the effective-voltage of said squarewave output to be constant by generating a compensating voltage across a capacitor, and a switching circuit for detecting a voltage across said capacitor and on-off controlling said output transistor. v

Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electrical circuit diagram of a conventional bimetal-type voltage stabilizer.

FIG. 2 is an electrical circuit diagram of a conventional transistor-type voltage stabilizer used in a meter.

FIG. 3 is an electrical circuit diagram of an embodiment of the present invention.

FIG. 4 is an electrical circuit diagram to be used for comparison to the present invention.

FIG. 5 is a schematic electrical connection diagram of the-present device to be used in the description of the effective-voltage of a square-wave output according to the present device.

FIG. 6 is a diagram of an output voltage waveform to be used in the description of the present invention.

FIG. 7 is an experimental characteristic curve of an example of the present device.

In the figures, similar reference numerals indicate similar or equivalent parts.

DESCRIPTION OF THE PREFERRED EMBODIMENT Description is first made on voltage stabilizers according to the prior art for facilitating the understanding of the present invention.

FIG. 1 shows a simple bimetal-type voltage regulator indicated in block A, which comprises contacts 1, a bimetal strip 2, a heater wire 3, a resistance wire 4, an indicator formed of a bimetal strip 5, a thermistor 6, an

input terminal 7, an output terminal 8, and a grounded terminal 9. Output is derived from the output terminal 8. Voltage regulators of this type have such a drawback that they often cause malfunction and have poor service life. There have been also proposed transistortype voltage stabilizers in which said contacts 1 are reformed or modified in contactless continuous type, such as shown in FIG. 2. The voltage stabilizer shown in FIG. 2 comprises a transistor 10, a resistor 11, a Zener diode 12, and a diode 13. An output is derived from the output terminal 8. Voltage stabilizers of this type have such a drawback that the power consumption in the transistor 10 is large and thus requires a larger power transistor which increases costs.

Now, description isrnade on the embodiment of the present invention shown in the drawings.

In the embodiment of FIG. 3, a voltage stabilizer (regulator) is indicated by A and includes a switching circuit B and a constant current circuit C for stabilizing an input current of the switching circuit B. The constant current circuit C consists of a resistor 14, a Zener diode 15, and a transistor 16. An output transistor circuit 10 consists of a Darlington connection of two

transistors

10a and 17 and is controlled by the circuit consisting of a Darlington connection of two transistors 18 and '19.

Numerals

20 and 21 are biassing resistors. A I

level shifting circuit D is formed of level-shifting

diodes

22,23 and 24 and a transistor 25. A switching voltage detecting circuit E is formed of a Schmitt circuit comprising two transistors 27.and 28, two

collector resistors

26 and 29, and a common emitter resistor 30. Further, a temperature compensating circuit F is formed of a transistor 32 provided with an emitter resistor 31, two diodes 33 and 34, and two

bias resistors

35 and 36. An impedance transforming circuit G for detecting voltage G is formed of a Darlington connection of two

transistors

37 and 38 provided with an emitter resistance 39, and forms an emittenfollower circuit for the abovementioned Schmitt circuit. An output voltage compensating circuit H is formed of a diode 40, four

resistors

41, 42, 43 and 44, and a capacitor 45. Here, the switching circuit B can be formed by various methods.

The operation of the present device will be described with respect to the above structure. A charging current is allowed to flow by a voltage appearing at the output terminal 8 through the diode 40 and the resistor 41 in the output voltage compensating circuit H to the capacitor 45. When the voltage of this capacitor 45 reaches a predetermined value, the transistor 28 of the switching voltage detecting circuit E becomes conductive and this transistor 27 becomes of a high level, i.e., its cut-off state. Then, through the level shifting circuit D including the three

diodes

22, 23 and 24 and the transistor 25, the voltage at the interconnection of the

resistors

20 and 21 is increased and the

transistors

18 and 19 connected in Darlington connection are turned into their conductive states. Thus, the output transistor circuit 10 is rendered to be cut off.

When the output transistor circuit 10 is cut off, the voltage at the output terminal 8 becomes zero. Then, in the output voltage compensating circuit the capacitor 45 discharges through two

resistors

42 and 43. When the voltage across the capacitor 45 decreases below a predetermined value, said switching voltage detecting circuit E is reversed and the output transistor circuit 10 returns to the conductive state.

The above cycle is repeated. Thus, a DC voltage applied to the input terminal 7 is transformed into a square-wave output having a stabilized effective voltage, which operates the load resistor 4, the indicator 5 formed of a bimetal strip and the thermistor 6, with high precision.

Further, the line voltage (power source voltage) for said switching voltage detecting circuit E is fixed by the constant current circuit C comprising the resistor 14, the Zener diode l5 and the transistor 16. Therefore, it does not vary even when a DC voltage applied between the

terminals

7 and 9 is varied. Further, the temperature compensation of this switching voltage detecting circuit E can be achieved by the temperature compensating circuit F in which the forward voltage drop of the two diodes 33 and 34 varies depending on the temperature and hence the base current of the transistor 32 is varied to achieve the temperature compensation. Further, the emitter-follower circuit G comprising two

transistors

37 and 38 and the emitter resistor 39 func tions to isolate the impedance on the Schmitt circuit side from that on the output voltage compensating circuit side and accordingly, the impedance on the switching voltage detecting circuit E side does not influence the charging and discharging time constant of the capacitor 45 in the output voltage compensating circuit I-I.

Next, the constancy of the effective-voltage of the square-wave output will be discussed in detail referring to the electrical connection diagram of FIG 5 of the present voltage stabilizer provided with an output voltage compensating circuit 1-! in comparison to the elec trical connection diagram of FIG. 4. The effectivevoltage of the present voltage stabilizer will be calculated. It is assumed that the voltage between input terminals'7 and 9 is V (volts), the resistances of the five

resistors

41, 42, 43, 44 and 47 are R (ohms), r1 (ohms), r2 (ohms), p (ohms) and r (ohms), the capacitance of the capacitor 45 is C (Farads), that the switching circuit B drives the output transistor circuit to be cut off when the voltage at a terminal 48 is V,, (volts) and to be conductive when the voltage at the terminal 48 is (V, AV), and that V, AV and the saturation voltage of the output transistor 10 and the voltage drop in the diode 40 are negligible First, the efi'ective-voltage at the terminal 8 of the voltage stabilizer of FIG. 4 Val is calculated. If the time periods during which the output transistor circuit 10 is conductive andcut ofiare set t and t as shown in the output voltage waveform of FIG. 6, respectively,

The charging current I flowing into the capacitor 45 when the voltage at the terminal 48 is in the neighborhood of V, is

provided that the output, transistor circuit 10 is conductive. Further, the discharging current I flowing from the capacitor 45 when the output transistor circuit 10 is cut off, is'

provided that a resistor of a sufficiently small resistance compared to .R is connected between the

terminals

8 and 9. Here, 1 and t are the time periods required for the voltage at the terminal 45 to rise from V, A V) to V and to drop from V,, to (V AV) by the charge and discharge of the capacitor 45. In this case, AV is sufi'iciently small in comparison to V and thus a (V0 cl' am 1 AV- C/I,

Further,

t AV-C/I I s From

equations

2, 3, 4 and 5, equation 1 becomes V g VI /I i- (6) Thus, in the output voltage controlling circuit of FIG. 4 when the input voltage is changed, the output effective-voltage V is also varied and the output squarewave does not have a stabilized effective-voltage.

Next, the effective-voltage of the square-wave output appearing at the output terminal 8 in the output voltagecompensating circuit of FIG. 5 V is calculated in the similar manner. When the voltage at the terminal 48 is in the neighborhood of V and the output transistor circuit 10 is conductive, the charging current I flowing into the capacitor 45 is f o)/ [(m p)' n "2' l/ 1' a (n- The discharging current 1, 5 flowing from the capacitor 45 when the output transistor circuit 10 is cut off, is

1, [(r +p)' V,,r 'V]/[r,'r +(r +r p] 3 W= o a) V2 Differentiation of W with respect to V gives dW/dV= o) 0 Thus, W has a flexion point at V 3 V,,.

In the neighborhood of V 3V,, the variation of W is extremely small and the effective-voltage of the squareoutput efiective-voltage V became almost constant. This range corresponds to the practical range of the effective-voltage stabilizer of the present example.

According to this effective-voltage stabilizer, a contactless transistor type voltage stabilizer capable of providing a square-wave output can be achieved, power consumption in a transistor can be decreased to reduce the cost, and loads such as a meter connected to this stabilizer can be operated with high precision by stabilizing the effective-voltage of the square-wave output.

I claim:

1. An effective-voltage stabilizer device comprising input terminal means for receiving an input voltage, output terminal means for connection to a load, an output transistor circuit coupling the input terminal means to the output terminal means, said output transistor circuit having a control input and having a conductive and a non-conductive condition responsive to said control input, an output voltage compensating circuit coupled to said output terminal means, said output voltage compensating circuit including a capacitor adapted to charge through said output transistor circuit when said output transistor circuit is in a conductive state and to discharge when said outputtransistor circuit is in said non-conductive state, and a switching controlling circuitresponsive to the state of chargeon said capacitor for generating a switching control signal, coupling means for coupling said switching control signal to said control input of said output transistor circuit for controlling the conductive state thereof, and in which said output voltage compensating circuit includes a series resistance circuit connected in parallel across said capacitor, in series connection circuit of a diode and a resistor, connected between the output terminal means and said series resistance, and a resistor connected between one connection point in said series resistance circuit and the input terminal means.

2. An effective-voltage stabilizer device according to claim 1, in which said series resistance circuit comprises a series connection of first and second resistors, and in which the resistance of said resistor connected in series with said-diode between the output terminal means being relatively large compared to that of the load, and the resistance of the'resistor connected between one connection point in said series resistance circuit and the input terminal means being larger than that 4. An effective-voltage stabilizer device according to claim 3, including an emitter follower circuit and in which said emitter follower circuit is connected between said capacitor and said Schmitt circuit for maintaining the time constant of charging or discharging of said capacitor constant. I

5. An effective-voltage stabilizer device according to claim 3, including a constant current source provided between said input terminal means and said output transistor circuit and in which said constant current source is coupled to said switching controlling circuit for supplying an output voltage to said switching controlling circuit as the power voltage source.

6. An effective-voltage stabilizer device according to claim 1, in which said output transistor circuit includes a Darlington circuit.

7. A constant effective-voltage power source circuit comprising a constant current circuit, an output transistor circuit connected to said constant current circuit for on-off controlling an input voltage, an output voltage compensating circuit connected to both .said constant current circuit and said output transistor circuit, a switching circuit connected to said output voltage compensating circuit for controlling the on-off state of said transistor circuit according to a voltage established in said compensating circuit, and output terminals connected to said compensating circuit whereon the effective voltage across said output terminals is maintained substantially constant.

8. A constant effective-voltage power source circuit according to claim 7, in which said output voltage compensating circuit comprises a capacitor, a series resistance circuit connected in parallel across said capacitor, a series connection circuit of a diode and a resistor, connected between the output side of said output semiconductor circuit and series resistance circuit, and a resistor connected between one connection point in said series resistance circuit and the'input side of said output semiconductor circuit.

Claims

1. An effective-voltage stabilizer device comprising input terminal means for receiving an input voltage, output terminal means for connection to a load, an output transistor circuit coupling the input terminal means to the output terminal means, said output transistor circuit having a control input and having a conductive and a non-conductive condition responsive to said control input, an output voltage compensating circuit coupled to said output terminal means, said output voltage compensating circuit including a capacitor adapted to charge through said output transistor circuit when said output transistor circuit is in a conductive state and to discharge when said output transistor circuit is in said non-conductive state, and a switching controlling circuit responsive to the state of charge on said capacitor for generating a switching control signal, coupling means for coupling said switching control signal to said control input of said output transistor circuit for controlling the conductive state thereof, and in which said output voltage compensating circuit includes a series resistance circuit connected in parallel across said capacitor, in series connection circuit of a diode and a resistor, connected between the output terminal means and said series resistance, and a resistor connected between one connection point in said series resistance circuit and the input terminal means.

2. An effective-voltage stabilizer device according to claim 1, in which said series resistance circuit comprises a series connection of first and second resistors, and in which the resistance of said resistor connected in series with said diode between the output terminal means being relatively large compared to that of the load, and the resistance of the resistor connected between one connection point in said series resistance circuit and the input terminal means being larger than that of the second resistor.

3. An effective-voltage stabilizer device according to claim 1, in which said switching controlling circuit includes a Schmitt circuit for generating a binary signal corresponding to the charging and discharging level of said capacitor.

4. An effective-voltage stabilizer device according to claim 3, including an emitter follower circuit and in which said emitter follower circuit is connected between said capacitor and said Schmitt circuit for maintaining the time constant of charging or discharging of said capacitor constant.

7. A constant effective-voltage power source circuit comprising a constant current circuit, an output transistor circuit connected to said constant current circuit for on-off controlling an input voltage, an output voltage compensating circuit connected to both said constant current circuit and said output transistor circuit, a switching circuit connected to said output voltage compensating circuit for controlling the on-off state of said transistor circuit according to a voltage established in said compensating circuit, and output terminals connected to said compensating circuit whereon the effective voltage across said output terminals is maintained substantially constant.

8. A constant effective-voltage power source circuit according to claim 7, in which said output voltage compensating circuit comprises a capacitor, a series resistance circuit connected in parallel across said capacitor, A series connection circuit of a diode and a resistor, connected between the output side of said output semiconductor circuit and series resistance circuit, and a resistor connected between one connection point in said series resistance circuit and the input side of said output semiconductor circuit.