DE1053036B - Arrangement for amplifying an electrical quantity, in particular audio frequency oscillations, by means of an astable trigger circuit formed from controllable semiconductor elements (transistors) with controllable trigger times - Google Patents

Description

There are already formed from controllable semiconductor elements astable trigger circuits with controllable Tilt times have been proposed in which, by adjusting the duty cycle (i.e., the ratio the passage time to the blocking time) the halves it elements a power control of to the Toggle switching connected consumers takes place.

According to the invention, such trigger circuits for amplifying electrical quantities are arbitrary used over time and for this purpose the duty cycle of the semiconductors as a function of the control brought by the electrical magnitude, while the pulse repetition frequency of the semiconductor elements - that is the time span between two successive switch-on times - greater than dife 'highest component (according to the Fourier decomposition) of the electrical quantity is selected. That way you can before All · Speech frequency vibrations can be amplified in a simple manner by removing these vibrations can be used as a control variable for influencing the pulse duty factor of the semiconductor elements.

Further details of the invention are explained below with reference to the drawing.

In Fig. 1 is an already proposed astable trigger circuit with which the consumer power controlling semiconductor elements in foam of transistors 1 and 2 shown. The emitters of both transistors are grounded while the collectors are across Resistors 3 and 4 are connected to a common supply voltage 5, with which via resistors 6 and 7 also connect the bases of both transistors. About capacitors 8 and 9 are the collectors and. Bases of the two transistors each mutually connected.

The duty cycle of transistors 1 and 2 is controlled by transistor 11, which via the resistors 12 and 13 to an auxiliary DC voltage source 14 is connected, the voltage of which - as already proposed ■ - · of at most double Size, but opposite polarity as that of the voltage source 5 is. Emitter and collector of Transistors 11 are each connected to the bases of transistors 1 and 2 via a diode 16 and 17, respectively. Another auxiliary DC voltage source is switched on between 18, the potential of which is in size corresponds approximately to that of the voltage source 5. The control dos transistor 11 is carried out by a Control voltage 15 which, depending on its level, opens transistor 11 to a greater or lesser extent. Ever The more the transistor 11 is open, the higher the potential at the collector of this transistor, so that the transistor 2 is blocked the longer, the transistor 1 stays open the longer. Depending on the size of the voltage sources15 Arrangement for amplifying an electrical quantity,

in particular of audio frequency oscillations, by means of a controllable Semiconductor elements (transistors) formed astable trigger circuit with controllable trigger times

Applicant:

Siemens-Schuckertwerke

Corporation,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Dipl.-Ing. Dr. Georg Sichling, Erlangen,

and Dipl.-Phys. Helmut Schwab, Nuremberg,

have been named as inventors

the opening and blocking times of the transistors 1 and 2 and thus the lengths of the current pulses flowing in resistors 3 and 4 are controlled in such a way that that with increasing length of the pulses in resistor 4, the length of the pulses in resistor 3 decays or the other way around.

If now according to the invention for the control voltage 15, a voltage with any time Profile is used, the length of the current pulses fluctuates in the resistors 3 and 4 according to the timing of the control voltage 15. Man thus receives a pulse length modulation known per se. Such an arrangement can preferably used to amplify audio frequencies. In this case, 3 and / or 4 or in series with these resistors in the collector circuit of the transistors 1 and 2 Be connected winding 20 of a loudspeaker. This loudspeaker is then excited by impulses whose duty cycle corresponds to the frequency of the control voltage 15, d. H. the modulation frequency, fluctuates.

In the above-described arrangement, the transistor 11 becomes zero from the control voltage with increasing positive control voltage, more

809 770/344

opens. However, since it is already completely blocked at zero, a further blocking with increasing negative control voltage cannot take place, so that when an alternating voltage is used as control voltage 15, the breakover times of transistors 1 and 2 are not controlled during the negative half-cycle. Man. So only in the positive half-wave of the alternating voltage 15 receives a modulation of the current impulses in the resistors 3 and 4 and thus the superimposed modulation frequency at the loudspeaker winding 20 in a form that would result from using a half-wave rectifier. In order to obtain a modulation with the positive and negative half-wave of the control voltage 15, the transistor 11 can, for. B. be set by a corresponding DC bias to an operating point which is approximately in the middle of the characteristic curve of this transistor, so that the transistor 11 is half open at the control voltage value zero. In this case, the transistor is opened more widely with increasing positive control voltages and less with increasing negative control voltages. So you get a modulation in both positive and negative direction. In the collector circuit of transistors 1 and 2, i.e. in resistors 3 and 4, current pulses are then obtained that are modulated with a voltage that is made up of a DC voltage component - caused by the DC bias voltage of transistor 11 - and the superimposed modulation frequency of control voltage 15 composed.

To compensate for the DC voltage component the loudspeaker winding can be connected to the collector potentials instead of in series in the KoUektorkreis be connected to the two 'transistors', as indicated in FIG. 1 by the loudspeaker winding 20 α is. The pure modulation frequency without DC voltage components is then obtained in the loudspeaker winding.

Another possibility for compensating for the DC voltage component is shown in FIGS. In the embodiment according to FIG. 2, in which the same reference numerals are chosen as in FIG. 1, a voltage source 21 is used to supply the bias voltage. The primary winding 22 α of a transformer 22 is arranged in the collector circuit of the transistor 2. The secondary winding of this transformer which feeds the loudspeaker 23 and which, if necessary, can also be the excitation winding of the loudspeaker, is denoted by 22 b. The transformer is provided with an additional compensation winding 22c, through which a compensation current that can be set at the resistor 24 flows, which can be set proportionally to the bias current supplied by the voltage source 21 and causes the magnetization of the transformer and thus the compensation of this direct voltage component. In addition, a favorable adaptation of the loudspeaker can be achieved by the transformer in a manner known per se.

Another possibility for modulation with two half-waves of the modulation voltage results from two push-pull control devices according to FIG. 3. The excitation winding 30 of the loudspeaker 23 is inductively connected to a collector circuit as shown. In this case, the two control transistors 11 and 11 b are connected in such a way that one is closed during the negative and the other during the positive half-cycle of the modulation frequency. As a result, the breakover times of transistors 1 α and 2 a, for example, are controlled by the positive half-wave of the modulation frequency, and the break-over times of transistors Ib and 2 b are controlled by the negative half-wave. Since the excitation winding 30 of the loudspeaker 23 is _{inductively connected to a collector circuit each via the primary windings 22 O 1} and 22O ₂ , the loudspeaker is influenced by both half-waves of the modulation frequency.

ίο Finally results in compensation of the DC component still the possibility of the excitation winding of this loudspeaker via a pulse converter to feed the DC impulses in Converts alternating current impulses. Such a pulse converter, which has already been proposed elsewhere can for example consist of buckets of a transformer, the primary winding of which has a center tap is provided .and in which a suitable control device sends the pulses alternately to the an oiler connects the other half of the winding.

The invention is not limited to the illustrated embodiments limited. Depending on the type of used; Toggle switching can be used instead of the one described Pulse length modulation method also a pulse position modulation method ears are used. Likewise, both the modulated pulses can be the two transistors 1 and 2 are used to control the consumer as well as the pulses both transistors in common. In each case, the mean value of the pulse voltage or the Pulse current fluctuate according to the modulation frequency.

It is useful to set the pulse repetition frequency of transistors 1 and 2 above that for human Ears to choose perceptible frequency range, for example above 25 kHz. Heard in the case you only get the modulation frequency from the loudspeaker, d. H. that is, the one controlling the transistor 11 Audio frequency.

Claims (9)

Patent claims: 1. Astable trigger circuit formed from controllable semiconductor elements (e.g. transistors) with controllable tilt times, in which by setting the duty cycle (i.e. the ratio the passage time to the blocking time) of the semiconductor elements a power control of to the Flip-flop connected consumers takes place, characterized in that for amplification an electrical variable (15) of any time course, in particular of audio frequency oscillations, the duty cycle brought into control dependence on this electrical variable and the pulse repetition frequency of the semiconductor elements - this is the time span between two consecutive stopping times - greater than 'the highest frequency component of the electrical variable is selected (Fig. 1). 2. Arrangement according to claim 1, characterized in that that the pulse repetition frequency is above the perceptible frequency range for the human ear, e.g. B. above 25 kHz. 3. Arrangement according to claim 1, characterized in that the electrical to be amplified Size a direct current or voltage component (21) is superimposed (Fig. 2). 4. Arrangement according to claims 1 to 3, characterized in that the consumer Excitation winding of a loudspeaker is used. 5. Arrangement according to claim 4, characterized in that the excitation winding to the Output voltages of the controlled semiconductor elements is connected. 6. Arrangement according to claims 4 and 5, characterized in that the excitation winding is coupled to the semiconductor elements via a transformer. 7. Arrangement according to. Claim 6, characterized in that that the transformer has a winding that compensates for the direct current component (22 c), which is traversed by a corresponding current (Fig. 2). 8. Arrangement according to one or more of the preceding claims, characterized in that that two trigger circuits working in push-pull are provided and the excitation winding of the loudspeaker inductive with one output circuit each of a Hailbler elemenite is (Fig. 3). 9. Arrangement according to one or more of the preceding claims, characterized in that that to compensate for the direct current component, a pulse converter in front of the loudspeaker is arranged, which converts the DC pulses into Weehselistrominipulse. 1 sheet of drawings ® 809 770/344 3.59