DE1537931B2 - CIRCUIT FOR GENERATING SAW-TOOTH-SHAPED VIBRATIONS - Google Patents

Description

shows. In Fig. 6, the main path of the thyristor Ty is parallel to the charging capacitor C. The control electrode S of the thyristor is at the center of the

the control electrode 5 practically at reference potential, so that the emitter potential of the transistor T is lowered. This lowering must take place to block the transistor T below the value of the base bias - L / _o .

The invention thus ensures .that the current flowing through the thyristor during discharge of the capacitor will certainly fall below the holding current of the thyristor, and thus the thyristor can return to the high-resistance state.

F i g. 7 shows a circuit arrangement which is basically the same, in which two complementary transistors T ₁ and T ₂ are used instead of a thyristor. The transistors are connected in such a way that the emitter of transistor T ₂ with the reference potential, the base of transistor T ₂ with the collector of transistor T ₁ , the collector of transistor T ₂ with the base of transistor T ₁ and the midpoint of voltage divider R. ₁ , R _{2 is} connected. The emitter of transistor T ₁ is at the collector of the constant current supplying transistor Γ. In this circuit arrangement, the control electrode S of the thyristor accordingly corresponds to the connection point of the collector of transistor T ₂ and the base of transistor T ₁ .

In a further development of the invention, a diode D can be provided which is either in series with the cathode or the control electrode of the thyristor or in series with an electrode of the circuit arrangement formed _{from the complementary transistors T 1} and T _2.

This diode is used to protect one of the pn junctions of the thyristor or the equivalent connected one Transistors and prevents the permissible reverse voltage from being exceeded in one of these pn junctions will.

It is also advantageous if a thyristor is used that only requires a very low control current and / or that with a very low holding current clears. In particular, thyristors in the proposed circuit arrangement have proven their Control current less than 5 mA and whose holding current is less than 10 mA.

In a further development of the invention, the voltage divider A ₁ , R ₂ can be made adjustable. With this measure, the amplitude of the sawtooth voltage can be selected.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Circuit arrangement for generating sawtooth-shaped Oscillations in which a capacitor is charged via a power source and, after the capacitor pairing has reached a maximum value, controlled by a bistable Component (thyristor, thyratron etc.) or Capacitor can be discharged is the controlled rectifier known as a thyristor. In Fig. 2 the structure of a thyristor is shown schematically. Like the four-layer diode, the thyristor Ty basically contains a semiconductor crystal with four consecutive layers of alternating conductivity types and can be ignited via the control electrode S , ie from a high-resistance state to a low-resistance state an equivalent circuit arrangement can be brought back io. This switching behavior of the thyrient charging is characterized, as is known, as shown in FIG. 3 shown, too that the capacitor (C) is connected in a known manner as a constant current source with two complementary transistors T ₁ , T ₂ and possibly some additional resistors The transistor (T) is charged, which is used to form. Discharging the capacitor in parallel bi- 15 From the German Auslegeschrift 11 86 496 it is known to connect a voltage divider R ₁ , R _{2 in} parallel to the capacitor in a sawtooth generator with a thyristor, at the center of which the control electrode of the thyristor, as shown in FIG. 4 ge stable controlled component (Ty) with its control electrode (5) is connected to a voltage divider (R ₁ , R ₂ ) , one end of which is connected to the emitter of the transistor (T). 2. sawtooth generator according to claim 1, da- 20 shows, is connected. The main route of the thyristor is characterized by the fact that in series with the box Ty is also parallel to the capacitor C. thode or the control electrode of the thyristor known, the control electrode of the condensate ^. valent transistor circuit arrangement of a thyristor serving as a capacitor discharge, as shown in Fig. & ode (D) to protect one of the pn junctions, to be connected to a fixed bias voltage. ie the voltage divider from the resistors R ₁ 3. Sawtooth generator according to claim 1 or 2, and R ₂ between the positive and negative poles, characterized in that a thyristor is to be connected to the operating voltage source U ₀ , which has only a very low control current, preferably less than 5 mA is required and / 30 nism-tightly tolerated components are used or those with a very low holding current, preferably. The current flowing through the thyristor drops by less than 10 mA. namely in the controlled state, i.e. in the low 4. sawtooth generator according to one of the claims ohmic state of the component not to zero before 1 to 3, characterized in that the voltage divider (A ₁ , R ₂ ) for setting the 35 but now via the from, since the charging current of the capacitor continues Thyristor flows, so that the amplitude of the sawtooth voltage can be adjusted. does not tilt back into the high-resistance state inevitably takes place. This is only the case when the current in the bistable controlled component is as follows is small that its minimum holding current is below -40. A sawtooth-shaped oscillation can according to the invention relates to a circuit arrangement Book "INTERMETALL-Schaltungsbeispiele", switching to generating sawtooth-shaped vibrations enttung 32, edition April 1962 thereby generated speaking the preamble of claim 1, and it is that a capacitor via a power source is based on the task, the above-described charged and after reaching a certain 45 th, in the known circuit arrangements on-voltage value is discharged again. This can avoid the disadvantages and create a scarf according to FIG. 1 as a current source for charging the Konk- tungsanordnunng, which are used to generate saw capacitor C a transistor T, whose base tooth-shaped oscillations are independent of the voltage at a fixed potential - U _B and allows tolerances of the bistable component and in its emitter branch a resistor R switched 50 in which the bistable controlled component is safely in, which when connected to the operating voltage - U ₀ flips back its high-resistance state. This is. The capacitor C is charged with an approximately constant task, according to the invention, by means of the current. The four-layer diode V is used to discharge the capacitor
their switching voltage ignites and the capacitor 55 In the further F i g. 6 and 7 of the drawing are discharged until the two circuit arrangements according to the invention flowing through the four-layer diode fall below their holding current. However, four-layer diodes are mainly produced with switching voltages greater than 15 V. and have relatively large holding current tole- 60 voltage dividers R ₁ , R ₂ connected, one of which is connected, so that they are always suitable for such applications not connected to the emitter of the transistor T at the end. In addition, the charging current must be. The voltage divider resistors R ₁ , R ₂ as well as being smaller than the holding current of the four-layer diode, emitter resistor R are, according to the characteristics, otherwise not back into their high-resistance state of the thyristor used and with respect to the state. This limits the usage level of the constant voltage -U 65 _B so as to dimenmöglichkeit the four-layer diode for generating sionieren that the transistor T is cut off when the Thysägezahnförmiger vibrations forth. ristor Ty ignites, i.e. in its low-resistance Another semiconductor component with which the stand switches. In this state lies namely men of the characterizing part of claim 1 solved.