US3696311A

US3696311A - Long-cycle transistor astable multivibrator

Info

Publication number: US3696311A
Application number: US18169A
Authority: US
Inventors: Takayoshi Oushige; Kikuo Iizuka
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1969-03-10
Filing date: 1970-03-10
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03
Also published as: GB1286372A; DE2011337B2; DE2011337A1; BR7017354D0

Abstract

A long cycle oscillator comprising a first and a second transistor, and a charge-discharge circuit including a capacitor and a resistor which are connected in parallel to each other, in which the said components are so constructed that a base current of the first transistor is controlled by a collector voltage of the second transistor, an applied voltage to the second transistor is controlled by the collector voltage of the first transistor, the base current of the second transistor being controlled by the collector voltage of the first transistor and the charge-discharge circuit.

Description

United States Patent Oushige et al.

[54] LONG-CYCLE TRANSISTOR ASTABLE MULTIVIBRATOR [72] Inventors: Takayoshi Oushige; Kikuo Iizuka,

both of Hitachi, Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: March 10, 1970 [21] Appl. No.: 18,169

[30] Foreign Application Priority Data March 10, 1969 Japan ..44/l7517 [52] US. Cl ..33l/l13 R, 318/227, 331/185 [51] Int. Cl. ..H03k 3/282 [58] Field of Search....331/l l3 R, 144, 185; 318/227 [56] References Cited UNITED STATES PATENTS 3,240,989 3/1966 Grunwaldt ..331/ll3X 3,061,742 10/1962 Harrison ..33l/ll3X [4 1 Oct. 3, 1972 3,253,234 5/1966- Kretzmer .331/113 FOREIGN PATENTS OR APPLICATIONS 1,030,824 5/1966 GreatBritain ..331/113 Primary Examiner-Roy Lake Assistant Examiner-Siegfried H. Grimm AttorneyCra.ig, Antonelli and Hill [5 7] ABSTRACT A long cycle oscillator comprising a first and a second transistor, and a charge-discharge circuit including a capacitor and a resistor which are connected in.parallel to each other, in which the said components are so constructed that a base current of the first transistor is controlled by a collector voltage of the second transistor, an applied voltage to the second transistor is controlled by the collector voltage of the first transistor, the base current of the second transistor being controlled by the collector voltage of the first transistor and the charge-discharge circuit.

7 Claims, 10 Drawing Figures PATENTEDncra m2 3.696.311

sum 1 BF 6 FIG. 2 $2 5? 5 M A OD 0 I1 B I T0 T1 T2 T3 5 TIME T INVENTORS TAKAYOSHI ouSHIGE and Klkua IIZMKA ATIYMNEYJ PATENTEDnms I972 CYCLE OF THE PULSATION (second) SHEET 2 OF 6 3 4 5 6 7 89 Iowa) RESISTANCE IN VENTOR 5 TAKAYDSHI ousuzsg m! Kl-kaa IIZMKA /M flwwu iw M ATTORNEY PATENTEU 0013 I972 3.696 31 1 sum 6 or 6 A 8% FIG. 8

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5 IO I S RISING TIME (second) FIG. 9 A9 902 F9 E9 INVENTORS TAKAYO$HI MSHIG'E a d K KMO IIZHKA ATTORNEYj LONG-CYCLE TRANSISTOR ASTABLE MULTIVIBRATOR BACKGROUND OF THE INVENTION This invention relates to an oscillator utilizing the charging and discharging characteristics of a capacitor for control thereof.

There is as a typical oscillator, the astable multivibrator, which utilizes the charging and discharging characteristics of a capacitor for control. Because in accordance with the astable multivibrator very desirable rectangular waves are produced easily by circuits which are simple, they have been used widely in the field of digital controls. Recently, astable multivibrator have been used in many fields including electric fans, for example, because of their low-cost, easy manufacture and high reliability in operation.

A conventional astable multivibrator is provided with a pair of transistors, and the collector of each of the transistors is respectively connected through a resistor to the power supply. Since the collector currents of the respective transistors are controlled only by their base currents and the operating point of each of the transistors lies on a straight load line which can be determined by values of the supply voltage and the resistors connected between the power supply and the respective collectors, only the initial part of the chargedischarge characteristics of the capacitors contributes to oscillation. Therefore, the cycle of the conventional astable multivibrator necessarily is shorter than the time constant which is determined by the capacitor and the resistor in the charge-discharge circuits. Because the conventional astable multivibrator has a pair of charge-discharge circuits and the charge and discharge of respective charge-discharge circuits are caused by mutual interferences, the. transistors necessarily are turned on or off, alternatively. Therefore, from its turn off-tum on characteristics, the output voltage cannot be controlled. If the resistance of the resistor for discharging is made too large, the base current considerably decreases, so that the transistor cannot switch on to stop the oscillation of the oscillator. Though, in order to lengthen the cycle of the oscillation, it may be thought to increase the capacity of the capacitor, a sufficiently large capacitance within its limited size cannot be obtained from the practical view point of manufacturing the capacitors.

Since a pair of charge-discharge circuits are employed in the conventional astable multivibrator, the relationship between the respective charge-discharge circuits is disturbed by fluctuation of the supply voltage to stop the oscillation. In addition, when the supply voltage is applied to the oscillator circuit, it is impossible to determine which transistor will switch on first between the pair of transistors. In a long cycle oscillator, to know which transistor will switch on first is very important in order to operate the devices or apparatus employing the oscillator without wasting operation time.

SUMMARY OF THE INVENTION capable of changing the oscillating cycle over very wide ranges.

It is another object of the present invention to provide an oscillator of the type described in which very long cycles can be generated, in spite of its use of a small capacity capacitor.

It is a further an object of the present invention to provide an oscillator which can continue to provide good oscillation, even if the supply voltage is not stable.

It is still another object of the present invention to provide such oscillator which is capable of continuously changing the output wave fonns.

It is still a further object of the present invention to provide an oscillator having a simple circuit.

An oscillator in accordance with the invention has first and second transistors. Since the collector of the first transistor is connected to the supply through a resistor, if the supply voltage is constant, the load line on which an operating point of the first transistor lies is almost linear. On the other hand, since the collector of the second transistor is connected to the collector of the first transistor, its load line on which the operating point of the second transistor lies can be controlled by the collector voltage of the first transistor. By changing the base current of the second transistor, the operating point of the second transistor can be optionally selected over the whole load line controllable by the collector voltage of the first transistor. In addition, as the base of the first transistor is connected to the collector of the second transistor, the collector voltage of the first transistor returns to the base of the first transistor. As a result, the operation of the first and second transistors can be controlled only by the charge-discharge circuit; and, even if the supply voltage frequently changes, the oscillator of the invention continues to provide good oscillation. In addition, good oscillation is continued only by the tum-off of the second transistor, without turning off and turning on the first transistor and the first and second transistors. Therefore, over the very wide range of the resistance of the resistor a variation in the discharging time can be expected to change the oscillation cycles over a very wide range, in accordance with the present invention. As the oscillation can be continued without turning on the first transistor, the output wave form is also changed continuously. In the case where the charge voltage of the charge-discharge circuit is nearly equal to zero, the collector current of the first transistor can be decreased instantly and the collector current of the second transistor is increased. The above-mentioned characteristics can also be observed in the case where the supply voltage is applied to the oscillator circuit.

BRIEF DESCRIPTION OF THE DRAWING The present invention is hereinafter particularly described with reference to the accompanying drawing, in which:

FIG. 1 is a principle circuit embodying the present invention;

FIG. 2 shows wave forms relative to voltage and current obtained by the circuit shown in FIG. 1;

FIG. 3 is a circuit diagram of a modified form of the circuit of FIG. 1;

FIG. 4 is a graph showing a relationship between oscillating cycles diagram and the resistance of the resistor in charge-discharge circuit in FIG. 3;

FIG. 5 is a circuit diagram whose oscillator circuit in FIG. 3 is used for controlling a motor of an electric fan;

FIG. 6 shows a variation in speeds of outdoor wind;

FIG. 7 shows a wave form of the variation in wind speeds produced by the motor circuit of the electric fan shown in FIG.

FIG. 8 is a graph showing the starting characteristics of the motor of electric fan shown in FIG. 5; and

FIG. 9 and FIG. 10 are diagrams of circuits to be used as a rectifier circuit in the oscillator circuit shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, there is shown a principle circuit for explaining an oscillator of the invention; in which the collector, emitter and base electrodes of a transistor 1 are respectively connected to a positive terminal A of a supply 5 through a resistor 3 and a switch 4, to a negative terminal B and to the collector of a transistor 2. The collector, emitter and base electrodes of the transistor 2 are respectively connected to the collector of transistor 1 through a variable resistor 6, to the negative terminal B and to the collector of transistor 1 through a'charge-discharge circuit 7 which comprises a capacitor 8 and a variable resistor 9. Though in FIG. 1 n-P-n transistors are used as the transistors 1 and 2, it goes without saying that the transistors can be replaced by P-n-P transistors with suitable change in the polarity of the bias.

FIG. 2 shows the waveforms generated by the unstable multivibrator shown in FIG. 1, in which the waveform A represents the collector voltage of first transistor 1, waveform B represents the charge voltage of capacitor 8, and waveform C shows the base current of transistor 2. When the switch 4 is turned on, the supply voltage is applied to the collectors of transistor 1 and transistor 2. The collector current i of transistor 1 begins to flow due to the base current i of the transistor 1 flowing from the supply 5 through the resistor 3 and variable resistor 6, and consequently, the collector voltage of the transistor 1 decreases. The collector current i of the transistor 2 will begin to flow also due to the base current i, of the transistor 2 flowing from the supply 5 through the resistor 3 and the chargedischarge circuit 7, and consequently, the collector voltage of the transistor 2 decreases.

The relationship between the collector current i of the transistor 2 and base current i of the transistor 1 is usually given by i5 i3 i2 where the current i is a current flowing through the variable resistor 6. With the decreasing of the collector voltage of the transistor 1 and the base current i., of the transistor 2 as capacitor 8 charges, the collector current i of the transistor 2 decreases. Since the current i is decreased by decreasing the collector voltage of the transistor 1, the base current i necessarily decreases, but this causes the collector voltage of the transistor 1 to increase. The rate of increase in the collector current i entering the transistor 2 is larger than that of the current i As a result, the collector current i of the transistor 2 becomes very large, but the collector current i of the transistor 1 becomes very small. When the value of the base current i, entering the transistor 2 is large enough to saturate the collector current i entering the transistor 2, the transistor 2 is turned on and the transistor 1 is turned off.

Due to the base current i., flowing through the' capacitor 8, the capacitor 8 is charged and the base current i, begins to decrease exponentially. The base current i., is decreased by the charging of the capacitor 8, and the collector current 1}, of the transistor 2 decreases, while the base current i of the transistor 1 increases. With increasing current i the collector voltage of transistor 1 decreases to cause a suppressing of the increase of current i with slow decrease in the collector voltage of transistor 1.

Up to the time of complete charging of capacitor 8, the base potential of the transistor 2 is lower than the collector voltage of transistor 1. The charging voltage of the capacitor 8 corresponds to the difference between the collector voltage of transistor 1 and base voltage of transistor 2. When the potential at the base J of the transistor 2 becomes negative, the base current i,

and collector current i of the transistor 2 are equal to zero. The current i through the variable resistor 6 is equal to the base current i of the transistor 1 and its collector voltage becomes low level.

In FIG. 2, T and T, respectively show the times of switching on and turning off, wherein the collector voltage A of transistor 1 reaches the maximum value. If the base current i., flowing into the transistor 2, as denoted by the line C in FIG. 2, is a large enough value to saturate the collector current of the transistor 2, the collector voltage of transistor 2 will be constant until the base current i flowing into the transistor 2 reaches a valve smaller than the value sufficient to saturate the collector current, as denoted by the line D in FIG. 2. The charge voltage of the capacitor 8 increases toward the level of the collector voltage of the transistor 1, so that the base current flowing into the transistor 2 decreases towards zero. If no collector current i of transistor 2 flows at the point T the collector voltage of transistor 1 becomes low level, as denoted by the line A in FIG. 2.

The base current i entering the transistor 1 is changed by adjustment of variable resistor 6 and therefore, the level of the collector voltage of the transistor 1 can be controlled by adjusting the resistance of variable resistor 6.

When the emitter-to-base voltage of the transistor 2 is negative, the capacitor 8 beingsto discharge through the variable resistor 9. As the charge of the capacitor 8 decreases, the potential at the base of transistor 2 increases toward the collector voltage of the transistor 1. On the other hand, when at the time T2 the emitter-tobase voltage of the transistor 2 is positive, both the base current i entering transistor 2 and the collector current i of the transistor 2 begin to flow, and the base current i flowing into the transistor 1 decreases. Decrease in the base current i flowing into the transistor 1 causes an increase in the collector voltage of the transistor 1. The base current i., flowing into the transistor 2 through the capacitor 8 considerably increases concurrently with the increase of collector current i;, entering the transistor 2 and the considerable decrease of base current i entering the transistor 1. When the collector current i flowing into the transistor 2 has a very small value, the base current i flowing into the transistor 2 charges the capacitor 8 again. In this way the oscillation of the oscillator can be continued.

Referring to the FIG. 2, the length of time between the T1 and T2 is controlled by changing the value of the variable resistor 9. The value of the collector voltage of transistor 1 is constant until the base current flowing into the transistor 2 begins to flow again, i.e., in the region between T1 and T2. At time T2, when the charge voltage of the capacitor 8 represented by curve B is nearly equal to zero and the emitter-to-base voltage becomes positive, the base current i., flowing into the transistor 2 instantaneously increases (line C) concurrently with increase of the collector voltage of the transistor 1. At the same time, the collector voltage of the transistor 1 considerably changes again over a very wide range.

FIG. 3 shows an oscillating circuit of the invention, in which the collector electrode of a transistor 304 is connected to a positive terminal A3 of a supply 301 through a load resistor 303 and switch 302, the base electrode of the transistor 304 is connected to the collector of a transistor 305, the emitter of the transistor 304 is connected to a negative terminal B of the supply 301 through a resistor 306, and the collector of the transistor 305 is connected to the collector of the transistor 304 through the resistor 307 and variable resistor 308. The base of the transistor 305 is connected through a charge-discharge circuit 309, resistor 310, and diode 311 to a point C3 which is connected to the variable resistor 308 and the resistor 307. A capacitor 312 which is connected between the collector and the base of the transistor 305, and the resistor 313 is connected between the base of the transistor 304 and the negative terminal B of the supply 301. Said chargedischarge circuit 309 employs a capacitor 315 and a variable resistor 314. The capacitor 315 is connected at the points D and E in parallel with the variable resistor 314.

As stated above, when the switch 302 turns on, the supply voltage is applied to the collectors of the

transistors

304 and 305, so that the base current of the transistor 30S begins to flow through the resistor 303, the variable resistor 308, diode 311, resistor 310, and the charge-discharge circuit 309 from the supply. As a result, the collector voltage of the transistor 304 reaches the maximum value, the collector voltage of the transistor 305 reaches a minimum value, and the base current entering the transistor 305 begins to charge the capacitor 315. The charging of the capacitor 315 will continue until the base potential at the transistor 305 becomes negative.

When the base potential of transistor 305 becomes negative, the transistor 305 is switched to the off stage and the collector voltage at the transistor 304 reaches minimum value. As the current flowing through the variable resistor 308 is almost equal to the base current entering the transistor 304, the minimum value of voltage at the collector of the transistor 304 may be regulated by changing the value of the variable resistor. When the base current flowing into the transistor 305 cannot flow through the charge-discharge circuit 309 because the capacitor 315 is fully charged, the electric charge of the capacitor 315 begins to discharge through the variable resistor 314. The discharging period of the capacitor 315 is therefore controlled by variation of the value of the variable resistor 314; the larger the value of the variable resistor 314 is made, the longer will be the discharging period produced. In case the charge voltage of the capacitor 315 becomes very small, the base potential at the transistor 305 becomes positive, and the collector voltage at the transistor 304 can be suddenly shifted to the high level, and consequently, the base current flowing into the transistor 305 begins to flow through the charge-discharge circuit again. The diode 311 prevents the transistor 305 from breakdown due to the inverse-directional application of the charge voltage of capacitor 315. The resistor 310 permits only flow of a small amount of the base current entering the base of transistor 305, and determines the value of the charging current of the capacitor 315. If the resistor 310 is large, charging current for the capacitor 315 will be small. Furthermore, since the capacitor 315 is charged very slowly, the flow of the collector current of the transistor 305 is prolonged thereby to lengthen the operating time of the transistor 305. If the resistor 310 is small, the charging of the capacitor 315 will be performed rapidly and the operating time of the transistor 305 becomes short. Since the value of the base current flowing into the transistor 305 is determined by the resistor 310, irrespective of any variation of the variable resistor 314, the value of the variable resistor 314 is changable over a wide range from large values to small values, and the repetition number of the pulses per unit time can be continuously changed over a wide range. Since the capacitor 312 is connected between the base and the collector of the transistor 305, even if the supply voltage changes frequently in the manner of a pulsating voltage, the oscillator of the invention will continue to oscillate and the capacitor 312 will rapidly absorb the noise produced by the changing collector voltages of the transistors 1 and 2.

FIG. 4 shows the variation of the oscillation cycle produced by the variable resistor 314, in which the horizontal axis shows resistances of variable resistor 314 and the vertical axis shows cycles of pulsation. In the example, the supply voltage was a pulsating voltage with V and a frequency of Hz produced by rectifying the alternating voltage, the load resistor 303 was 1.0 k 0 the resistor 306 was 22 Q, the resistor 307 is 4.0 k (I, the resistor 313 was 10 k 0, the resistor 310 was 300 k 0, and the capacitor 315 was 10 p. F. The value of the variable resistor 308 was selected to be zero 0, and transistor 304 and transistor 305 respectively had low frequency amplifications of about 100 and had a large backward resistance. These transistors were made of silicon, and the diode 311 had a large value of backward resistance. Though FIG. 4 shows only the range where the value of the variable resistor is from 10 M Q to about 0.7 M Q, if the value of the variable resistor 314 is larger than 10 M Q, the cycle of the oscillation becomes longer still, and if the value of the variable resistor 314 is smaller than 700 k 0, the cycle of the oscillator becomes shorter still.

As one embodiment of the invention, a circuit using a motor substituted for the resistor 303 shown in FIG. 3 is illustrated in FIG. 5. A main winding 501 is connected to the line through a switch 505 at a pair of input terminals A5 and B5, and an auxiliary winding 502 and a capacitor 503 which are connected in series with each other and are respectively connected in parallel with the main winding 501. A motor circuit comprises the main winding 501, the auxiliary winding 502 and the capacitor 503. Input terminals C5 and D5 of a full-wave rectifier 501 comprising four diodes are connected in parallel with the auxiliary winding 502 of the motor, and output terminals G and H5 of the fullwave rectifier 507 are connected to an oscillator circuit 511 through a surge absorber 525 comprising a diode 508, a capacitor 509, and a varistor 510. The oscillator 511 corresponds to the circuit shown in FIG. 3 except for the switch 512.

In the oscillator circuit 511, a transistor 515 is connected between two output terminals G5 and H5 of the full-wave rectifier 507, so that the collector is connected to the positive terminal GS of the rectifier 507 and the emitter is connecter to the negative terminal H5 of the rectifier. A resistor 516 is connected between the emitter of the transistor 525 and the negative terminal H5 of the rectifier. One end of a variable resistor 517 is connected to the collector of the transistor 515 and the other end is connected to a resistor 519 and a diode 522. One end of the resistor 519 is connected to the variable resistor 517 and the other end is connected to the collector of the transistor 518. The diode 522 is connected from the variable resistor 517 and the resistor 519 to the resistor 521. One end of the resistor 521 is connected to the diode 522 and the other end is connected to the charge-discharge circuit 523 employing a capacitor 526, a variable resistor 527 and the switch 512. The variable resistor 527 is connected in parallel with the capacitor through the switch 512. A capacitor 524 is connected between the collector and the base of the transistor 518, of which the collector is connected to the base of the transistor 515 and the emitter is connected to the negative terminal H, of the rectifier and the resistor 516, respectively. Both the motor circuit 504 and the full-wave rectifier correspond to the load resistor 303 shown in FIG. 3.

FIG. 6 shows wind speed variation of natural outdoor wind v.s. time. From this FIG. 6, it will be found that there is a constant cycle in the complicated variation of the wind speed. It is said that the natural outdoor wind makes people feel more comfortable than artificial wind since there are delicate changes of the wind speeds in the natural wind. According 'to the circuit shown in FIG. 5, in which an electric fan motor is used for the motor circuit, the rotation speed of the electric fan motor can be controlled by using the oscillator of the invention, and by the electric fan using the oscillator of the invention the same wind as the natural outdoor wind can be produced. It is essential for producing such a variable wind that the rotation speed of the electric fan motor can be changed with a considerably long .cycle.

Referring to FIG. 5, the motor is provided with the auxiliary winding 502 and the main winding displaced 90 electrical degrees from each other. The main winding 501 is connected directly to the alternating supply through the switch 505, and the auxiliary winding 502 having a capacitor 503 connected in series therewith is connected in parallel with the main winding. The phase of current in the main winding 501 lags from that of the supply voltage, while the current in the auxiliary winding 502 precedes that of the supply voltage. As a result, the currents in the two windings are displaced nearly 90 in phase from each other and therefore, a uniform rotating magnetic field can be produced. The torque of the motor will be developed by the electromagnetic action caused between the current in the rotor and the uniform rotating magnetic field. Accordingly, it is possible to control the motor speed of the electric fan by changing the value of the current into the main winding or auxiliaryv winding, or of the phase difference between the currents in the stator windings.

The circuit shown in FIG. 5 provides the way to control the torque of the motor by changing the current in the auxiliary winding. When both the switch 512, employed in the charge-discharge circuit, and the switch 505 are switched on, the alternating current flows into the two stator windings and the capacitor from the supply through the switch 505, and the terminal voltage of the auxiliary winging is applied to the oscillator circuit through the full-wave rectifier 507 and the surge absorber 525. As already explained, in conjunction with FIG. 3, if the voltage is applied to the oscillator circuit 511, the collector voltage at the transistor 518 becomes low, and the collector voltage at the transistor 515 becomes high. Thus, the current entering the oscillator circuit 511 becomes minimum and the current into the auxiliary winding becomes maximum. As a result, when the rotor of the motor begins to rotate, the starting torque also becomes maximum.

With charging of the capacitor 526 employed in the charge-discharge circuit, the current flowing into the oscillator circuit 511 through the full wave rectifier becomes large and finally, the current flowing into the oscillator circuit 511 becomes maximum. As a result, the rotating speed of the motor becomes minimum. During discharging of the capacitor 526 employed in the charge-discharged circuit 523, the rotating speed of the motor is minimum. In this case, as the transistor 518 is cut off, the current flowing through the variable resistor 517 is nearly equal to the base current flowing into the transistor 515. The base current of the transistor 515 will be controlled by changing the value of the variable resistor 517. As a result, since the current entering the oscillator circuit will be controlled by changing the value of the variable resistor 517, the minimum level of the rotating speed of the motor is controlled by changing the variable resistor 517. The variation of the wind produced by the electric fan shown in FIG. 5 is illustrated in FIG. 7.

In this embodiment, components employed in FIG. 5 were as follows, the transistor 515 was 2SC454C, transistor 518 was 2SC685A, the value of the variable resistor 517 was zero, the value of the resistor 516 was 22 Q, the value of the resistor 519 was 4 k 0, the value of the resistor 520 was 12 k (I the diode 522 was 185313, the value of the capacitor 509 was 3.3 p. F, the varistor 510 was S-TDlOO, and the diodes 506 being employed in the full-wave rectifier were BS-4. The voltage supply has a value in the order of volts with 50 Hz frequency. In spite of application of the pulsating voltage produced by rectifying the alternating voltage which tends to deteriorate the oscillation, as the oscillator of the invention is not controlled by plural chargedischarge circuits but only by one charge-discharge circuit, good oscillation can be expected. Furthermore, because the capacitor is connected between the base and collector of the transistor 518, the above characteristic is improved, if the oscillating cycle is much longer than the time during which the current flowing in the oscillator is nearly equal to zero.

In case the switch 512 is opened, the switch 505 is also opened. The pulsating current being produced by rectifying the alternating current enters the oscillator circuit 511, and at the same time the base current of the transistor 518 flowing into the capacitor 526 lowers the collector voltage of the transistor 518 and the collector current flowing into the transistor 515. Contrary to the decrease in the current entering the oscillator, the values of the current flowing into the auxiliary winding and the starting torque become large. When the charging voltage between the terminals of the capacitor 526 is of large value, the base current flowing into the transistor 518 will be almost equal to zero. Therefore, the transistor 518 is cut off and the rotating speed of the motor is reduced to a minimum. As already explained, the current flowing into the resistor 519 will be nearly equal to the base current flowing into the transistor 515 and the minimum level of the rotating speed of the motor can be controlled by changing the variable resistor 517. If the leakage current of the capacitor 526 and the backward current through the transistor 515, the transistor 518 and diode 522 are almost zero, theoscillation does not take place. Therefore, in this case the wind strength produced by the electric fan is not changable. If the rotationspeed of the motor isset at 400 rpm by adjusting the variable resistor 517, the characteristics of the starting speed can be shown in FIG. 8, in which example the supply voltage was 100V with a frequency of 50 Hz as defined by curve A, and in another example the supply voltage was 100V with a frequency of 60 Hz as defined by curve B. In FIG. 5, if full-wave rectifier 507 is connected in parallel with the capacitor 503, it can be expected that an effect similar to the above will be obtained. In the case when the current flowing into the oscillator 511 through the full-wave rectifier is of small value, the currents in the two windings are respectively displaced nearly 90 in phase and the rotating speed of the motor is increased.

On the other hand, with increasing of the current flowing into the oscillator 511, the phase difference between the two currents in the two windings becomes small, then the rotating speed is decreased. Instead of the full-wave rectifier, a half-wave rectifier can be employed in the oscillator of the invention. An oscillator using the circuit shown in FIG. 9, which is substituted for the surge absorber and the full wave rectifier, will also cause good results. The terminals A9 and B9 are connected to the oscillator 511 and the tenninals C9 and D9 are connected to the motor, respectively. A resistor 902 is connected between the terminal A9 and the anode F9 of a silicon controlled rectifier 905 of which the anode and cathode are respectively connected to output terminals E9 and F9 of a full-wave rectifier. A resistor 903 is connected between the terminals A9 and B9, and a capacitor 904 is connected between the terminal B9 and the cathode G9 of the silicon-controlled rectifier 905. A bi-directional diode thyristor 906 is connected between the terminal B9 and a gate terminal E7 of the silicon-controlled rectifier 905. As stated already, the pulsating current is produced by rectifying the alternating current which flows into the oscillator circuit from the motor through the terminals A9 and B9, to bring about the oscillation, and the amount of the current flowing into the oscillator is changed with the oscillation cycle. The resistance between the terminals A9 and B9 is changed with the cycle of the oscillation. The voltage at the terminal B9 rises with the increasing of the supply voltage, and the conduction of the silicon controlled rectifier starts at the angle, where the applied voltage at the terminal B9 becomes equal to the critical switching voltage of the bi-directional diode thyristor 905. When the resistance between the terminals A9, B9 becomes large, the angle where the conduction of the silicon controlled rectifier starts becomes large and the conduction angle of the silicon controlled rectifier becomes small. As a result, the rotating speed of the motor increases. On the other hand, as the resistance between terminals A9, B9 is decreased, it is possible to lengthen the time during turning-on of the silicon controlled rectifier in one cycle of the pulsating voltage produced by rectifying the alternating voltage. As a result, the torque of the motor becomes low in value to decrease the rotating speed of the motor.

In FIG. 5, the circuit shown in FIG. 10 which is substi tuted for the full-wave rectifier 507, can also cause good results. Input terminals A10 and'BlO are connected to the motor, both anode and cathode of a bi directional triode thyristor are respectively connected to terminals A10 and B10. A resistor 1001 is connected between two terminals A10 and C10, and a resistor 1002 is connected between a pair of input terminals C10, D10 of the full-wave rectifier. A capacitor 1003 is connected between the terminal D10 and a cathode terminal B10 of the bi-directional triode thyristor, and a bi-directional diode thyristor 1004 is connected between the terminal D10 and a gate terminal E10 of the bi-directional triode thyristor. Output terminals F10 and G10 of the full-wave rectifier are respectively connected to the terminals of the oscillator circuit.

In FIGS. 9 and 10, the conduction angle of the thyristor 1005 and the silicon controlled rectifier 905 are controlled by the oscillation. When the conduction angle is large, the rotating speed decreases. When the conduction angle is small, however, the rotating speed increases.

Though the transistors are used in the oscillators shown in FIGS. 1, 3 and 5, the transistors can be replaced with other switching components, provided that they have an amplification function, and their main current can be controlled by controlling current in which the main current and controlling current respectively correspond to the collector current and the base current of the transistors in the above examples. For example, vacuum tubes, field effect transistors and silicon controlled rectifiers may be used as well as the transistors. It will be understood that examples shown in FIGS. 9 and 10 can be employed for the oscillator to be utilized with considerably large loads.

Although the present invention has been described with reference to but a single embodiment, it is to be understood that the scope of the invention is not limited to the specific details thereof, but is susceptible of numerous changes and modifications as would be apparent. to one with normal skill in the pertinent technology.

What we claim is:

1. An oscillator comprising a first and a second switching component, respectively, each having an amplification function, first and second main current electrodes, and being capable of controlling its main current in response to an applied controlling current at a control input thereof, -a load and a supply voltage source connected in .series between said first and 7 second electrodes of said firstswitching component,

and a charge-discharge circuit connected between said first electrode of said first switching component and the control input of said second switching component and having a predetermined time constant through which said controlling current of said second switching component is changed by said main current of said first switching component, whereby a voltage to be applied to said second switching component is controlled by said main current of said first switching component, and means connecting the first electrode of said second switching component to the junction of said load and said first electrode of said first switching component, said control input of said first switching component being connected to said first electrode of said second switching component whereby said controllingcurrent of said first switching component is controlled directly by said main currents of said first and second switching components and the second electrodes of said first and second switching components being directly connected together.

2. An oscillator according to claim 1, in which said first and second switching components are a first and a second transistor, respectively, whereby the collector current of said second transistor is controlled by the collector voltage of the first transistor, the base of the second transistor being connected through said chargedischarge circuit to the collector of the first transistor, the collector of said second transistor being connected through a variable resistance to the collector of said first transistor, the emitters of said first and second transistors being connected together and the base of the first transistor being connected to the collector of the second transistor.

3. An oscillator comprising a first transistor having a collector and an emitter; a voltage supply; a first resistor connected between the collector of the first transistor and one side of said voltage supply; a second transistor having a collector connected to the base of the first transistor and an emitter connected to the emitter of the first transistor; a second resistor connected between the collectors of the first and second transistors; a first capacitor connected between the collector of the first transistor and the base of the second transistor; and a third resistor connected in parallel to said first capacitor.

rectifier circuit and said load, and a base; a second transistor having a collector connected to the collector of said first transistor through a first resistor, an emitter connected to said alternating current supply through said rectifier and said load and a base connected to the collector of said first transistor through a chargedischarge circuit; the base of said first transistor being connected to the collector of said second transistor.

6. An oscillator according to claim 5, including a first capacitor connected between the collector and base of said second transistor, a second resistor connected between the base and emitter of said first transistor and a third resistor connected between the emitter of said first transistor and said rectifier circuit.

7. An oscillator as defined in claim 5, wherein said rectifier circuit is connected to a circuit comprising a silicon controlled rectifier of which an anode and a cathode are respectively connected to output terminals of said rectifier circuit, a second resistor connected between said anode of said silicon controlled rectifier and a third resistor, a first capacitor connected between said third resistor and said cathode of said silicon controlled rectifier, a bi-directional diode thyristor connected between a gate of said silicon controlled rectifier and both said first capacitor and said third resistor, and the third resistor connected between two input terminals of said oscillator.

Claims

1. An oscillator comprising a first and a second switching component, respectively, each having an amplification function, first and second main current electrodes, and being capable of controlling its main current in response to an applied controlling current at a control input thereof, a load and a supply voltage source connected in series between said first and second electrodes of said first switching component, and a charge-discharge circuit connected between said first electrode of said first switching component and the control input of said second switching component and having a predetermined time constant through which said controlling current of said second switching component is changed by said main current of said first switching component, whereby a voltage to be applied to said second switching component is controlled by said main current of said first switching component, and means connecting the first electrode of said second switching component to the junction of said load and said first electrode of said first switching component, said control input of said first switching component being connected to said first electrode of said second switching component whereby said controlling current of said first switching component is controlled directly by said main currents of said first and second switching components and the second electrodes of said first and second switching components being directly connected together.

2. An oscillator according to claim 1, in which said first and second switching components are a first and a second transistor, respectively, whereby the collector current of said second transistor is controlled by the collector voltage of the first transistor, the base of the second transistor being connected through said charge-discharge circuit to the collector of the first transistor, the collector of said second transistor being connected through a variable resistance to the collector of said first transistor, the emitters of said first and second transistors being connected together and the base of the first transistor being connected to the collector of the second transistor.

4. An oscillator according to claim 3, including a second capacitor which is connected between the base and the collector of said second transistor, a fourth resistor connected between the other side of said voltage supply and the base of said first transistor and a fifth resistor connected between the emitter of the first transistor and the other side of said voltage supply.

5. An oscillator comprising a first transistor having a collector connected through a rectifier circuit and a load to an alternating current supply, an emitter connected to the alternating current supply through said rectifier circuit and said load, and a base; a second transistor having a collector connected to the collector of said first transistor through a first resistor, an emitter connected to said alternating current supply through said rectifier and said load and a base connected to the collector of said first transistor through a charge-discharge circuit; the base of said first transistor being connected to the collector of said second transistor.