DE1438647B2 - Circuit arrangement for controlling an actuator containing at least one thyristor, via which a consumer is fed from an alternating current source - Google Patents

Description

40

The invention relates to a circuit arrangement for controlling at least one Thyristor containing actuator via which a consumer is fed from an alternating current source is, containing a pulse generator for generating ignition pulses for the thyristor or thyristors in such a way, that the firing frequency of the thyristor or thyristors is equal to the simple or an integral multiple the frequency of the alternating current source and the phase position of the ignition times corresponding to the Phase position of a control signal can be changed.

A circuit arrangement of the aforementioned type is known in which the actual value of the consumer voltage fed to a voltage regulator with integral behavior and there with the constant Voltage of a Zener diode is compared. The difference is after reinforcement in one Transistor amplifier in the pulse generator in a single pulse per half-wave with a certain lead angle transformed in the cycle of the mains frequency. These individual pulses serve as ignition pulses for the thyristors (Journal "ETZ-B" issue 19 of September 19, 1960, pp. 455 to 457).

When using short pulses it can happen that a pulse occurs just when there is no forward voltage on the thyristor so that it does not ignite. Even if a forward voltage is present, it may happen that the current flowing in the forward direction is not one reaches such a height at which it holds itself. This can result from too short a duration required Energy level at the ignition electrode, especially when the current is in the forward direction slowly builds up in an inductive load.

As is known, this disadvantage can be eliminated by increasing the pulse duration and thereby increasing the the total energy supplied to the ignition electrode is increased.

In the known circuit arrangements, the individual pulses are synchronized with the mains frequency generated. For such low-frequency impulses, especially for impulses of long duration, one needs but for their generation and transmission to the thyristor ignition electrodes large capacities and Transformers, which make the arrangement difficult and complex. Has a great transformer It also has a high leakage inductance, which means that the pulse rise time is short low winding capacity can only be achieved with difficulty.

The invention is based on the object of providing a circuit arrangement of the type mentioned at the beginning create that can be produced with relatively small components in a simple and inexpensive manner and which can generate not only short but also long ignition pulses.

According to the invention, this object is achieved in that the pulse generator is free has running blocking oscillator, the repetition frequency of which is large compared to the frequency of the AC source is, and the blocking oscillator can be triggered by the control signal so that it each time generates a series of pulses at the repetition frequency when the control signal occurs, either as such or after passing through an integrating circuit of the firing electrode of the thyristor or the ignition electrodes of the thyristors are fed.

The pulse series is preferably sent to the ignition electrode of the thyristor or the thyristor via a transformer. the trigger electrodes of the thyristors are applied.

A "free-running blocking oscillator" is to be understood as an oscillation circuit in which only Current flows in half a period before the oscillation is caused by a self-generated bias of the tube or the transistor is interrupted, and which continues after it is switched on, in alternating half-cycles to provide outputs at a frequency determined by its own components and is determined by the supply voltage. It should also be noted here that the exit of the blocking oscillator has no relation to the frequency or phase of the alternating feed current.

As a result of the pulse train generated in the arrangement according to the invention with a high pulse frequency In particular, the required capacitors and transformers can be kept considerably smaller than when generating single pulses with mains frequency.

The pulse series can be fed to the trigger electrodes of the thyristors as such. At a inductive consumer it can happen that after successful ignition of the thyristor the current builds up so slowly that the minimum

3 4

Holding current, which keeps the thyristor ignited, at the end in the usual manner in the circuit arrangement 4 the pulse series has not yet been reached. In are generated, and Fig. 2b shows pulses6, which are to In this case, the pulse trains go through an inter- at the end of each half-period are lengthened, which green circuit, whereby a long lasting pulse may be required under certain circumstances, which is the current rise time in the 5, for example, when the consumer 3 is inductive. inductive loads are bridged until the minimum In F i g. 3 is an example of a useful one current is reached, in which the thyristor is conductive embodiment according to the invention is absent. Here, too, the circuit arrangement formed with the generation remains for a high frequency Impulse-connected, above-described AC actuator feeding the consumer is shown Get benefits. posed io.

The integrating circuit preferably consists of the circuit arrangement is fed by an alternating diode, a charging capacitor and a discharging resistor connected in parallel to the power source synchronously with the alternating current supply to the actuator. A rectifier bridge stood. which consists of four rectifiers MR 1 to MR 4,

It should also be noted that a circuit 15 is designed in such a way that, on the one hand, it feeds the circuit arrangement for controlling the mercury vapor arrangement with direct current and, on the other hand, it supplies control voltages for a transistor TV 1 to converters in the form of a transistor control unit. It is known, in which the output stage has a trans parallel to the direct current output of the rectifier-formative feedback for steepening the bridge, a capacitor C1 is connected. The Tran-individual ignition impulses, whereby the saturation of the 20 sistor TV 1 is contained in an oscillating circuit, output transformer the width of the generated which determines an output of sawtooth form in the following individual impulses (»VDE-Fachberichte« 1958, generated the way.
Vol. 20, pp. 102 to 108). For most of each half period of the

■ The invention is explained below on the basis of the alternating feed current is either the \ drawing, for example, explained in more detail. 25 anode of the rectifier MR 2 or the anode of the

F i g. 1 a shows schematically an AC power rectifier MR 4 with reference to the positive

■ member with an assigned circuit arrangement DC supply line on a negative j and a connected consumer; Potential, and the transistor TV1 is through the! Fig. Ib illustrates the alternating current flow resulting base current, the through a counter; by the consumer under two conditions; 30 stood Rl or a resistor R 2 flows, switched on, 'FIGS. 2a and 2b show two forms of ignition switched on. Pulses parallel to the base-emitter path, as is the case with conventional circuit arrangements of the transistor PT 1, there is a resistor i? 3. The genes are generated; The collector of the transistor VT 1 is located on a] F i g. 3 schematically shows a circuit arrangement potential approximately equal to that of the positive lead and voltage according to the invention; 35 is connected to a rectifier MR 5 .

j F i g. 4, 5, 6 and 7 show waveforms which in Under these conditions the equation

) the circuit arrangement according to FIG. 3 occur; current a capacitor C2 through a resistor

; F i g. 8 shows schematically a modified Aus R 6 charged, and a decoupling is through a

j implementation of a circuit arrangement according to the resistor R 5 and a capacitor C 3

Invention; 4 ° see. The potential at the junction between

F i g. 9 a to 9 e show different waveforms, see the capacitor C 2 and the resistor R 6

in the circuit arrangement according to FIG. 8 assumes a negative value and builds up

will hold; exponentially in the positive direction with a value of i? 6

FIGS. 10 and 11 show a further modified and C2 determined time constant.
Embodiment of a circuit arrangement according to FIG. 45 When the supply voltage at the end of each half of the invention. period drops to zero, the transistor VTl Das in F i g. 1 shown in schematic form switched off, and the capacitor C 2 discharges AC control element 1 contains two thyristors 2, via the rectifier MR 5 and a resistor which are connected in parallel in opposite directions. The R 4. In this way, the end of the resistor connected to the Kon actuator 1 is fed by an alternating current source 5 ° capacitorC2 and supplies energy to a consumer 3. R 6 a voltage of exponential sawtooth shape. A circuit arrangement 4 is provided which is generated via (indicated in FIG. 4 at 7) which has a return line a, b, c and d firing pulses for the firing frequency that supplies twice the free electrodes of the thyristors 2. sequence of the alternating feed current (in FIG. 4 at 8 A control of the flow through the consumer 3 indicated) and is in phase with it. The alternating current is obtained by changing the phase. In the absence of any other input to j of the leading edge of the firing pulses with respect to the base of a transistor VT2 , its base] the alternating feed current is achieved. In Fig. 1b shows current always negative, and this transistor will therefore be the upper waveform in the event that the firing pulses are kept conducting. However, when supplied to the j early in each half cycle, which DA-60 connectors and e / a of the circuit Steuergleich-; leads to a relatively large proportion of the voltage being applied (positive line at the available output energy to consumer 3), then it is passed through a resistor R 14, while the lower waveform is a positive voltage to the base of the transistor The case shows that the firing pulses are applied in each half- VT 2 , so that a base current is supplied period late at one point, which results in 65 being cut off in the half-period at which a relatively small proportion of the output of the through the Resistor R 14 passing energy to the consumer 3 is supplied. Current approximately equal to that through the resistor R 6. Fig. 2a shows individual short pulses 5 as it is the current passing through. The phase of this

Point can be changed by changing the amplitude of the DC control voltage, so that by this means the transistor VT 2 can be switched off at a controllable point in each half cycle.

A transistor VT 3, a transformer T1, a capacitor C 4 and a resistor R 9 are arranged so that they form a free-running blocking oscillator, which free-runs as long as the base of the transistor VT 3 is at a sufficiently negative potential with respect to its emitter is held. The circuit arrangement is designed such that when the transistor VT 2 is switched off, the base of the transistor VT 3 is supplied with current through a resistor R 7, which causes the blocking oscillator to operate, and when the transistor VT 2 is switched on, the The base of the transistor VT 3 is held at the potential of the positive supply line, as a result of which the blocking oscillator is kept in the idle state. A resistor R 8 and a rectifier Mi? 6 bias the transistor VT 3 to ensure that the "on" voltage at the transistor VT 2 turns the transistor VT 3 off.

In this way, as shown in FIG. 5, the blocking oscillator is activated in each half cycle at a point 9, the phase of which can be changed by changing the DC control voltage at the terminals e and /, to deliver a series 10 of pulses which extend almost to the end continue the half-period. It is a property of the barrier oscillator that the amplitude peak is reached as soon as it is switched on, thereby avoiding undesirable gradual build-up.

To feed an inductive load 3, it is preferable to rectify and smooth the individual pulses of the pulse series 10 with the aid of rectifiers MR 7 and Mi? 8, capacitors C 5 and C 6 and resistors i? 10 and i? 11, with resistors i? 12, i? 13 serving to limit the current in the control electrode circuits. In this way, the output pulses in each pulse train can be given a triangular shape, as shown in FIG. 6 is shown at 101, or they can be smoothed more completely as shown in FIG. 7 is shown at 102.

If necessary, the generator of the sawtooth voltage can be modified so that the pulse trains once, twice or more times in each Period of the alternating supply current can be generated, and two or more blocking oscillators can be used be provided together with associated control electrode circuits, such that the various Blocking oscillator during successive periods of the sawtooth voltage supplied by the generator are switched on one after the other, so that the output pulses are sent to different Output connections appear.

A circuit arrangement in which the series of out-going pulses in alternating half-periods of the alternating supply current appear at two pairs of output connections is shown in FIG. 8 shown.

The circuit arrangement according to FIG. 8 works in a manner similar to that according to FIG. 3, but it has the following changes:

A part of the circuit arrangement according to FIG. 8 feeding alternating current is fed to the base circuit of the transistor VT 2 during the half-cycle during which the series or series of output pulses are not required. This part of the alternating feed current can be taken from one or the other supply line, depending on the half-period in which the pulse series or the pulse series are to be suppressed.

As shown in FIG. 8 can be seen, is a line from the junction of the rectifiers MR 3 and MR 4 via a resistor i? 15 led to the base of transistor VT2 .

Which the transistor VT 2 through the resistor i? 15 is indicated in Fig. 9a at 11, and in the half cycle indicated at 12, in which the rectifier MR 4 is reverse biased, a negative peak is generated.

A voltage that is similar to voltage 11, but of opposite phase, is applied across a resistor i? 20 is applied to the base of a transistor VT 4, which with a transistor VT 5 and associated components (resistors i? 18, i? 19, i? 21) forms a circuit similar to that of the transistors VT 2 and VT 3.

The sawtooth voltage generated by the transistor VT 1 and its associated components is shown in FIG. 9 b shown at 13. The combined voltage resulting from the voltage 11 and the sawtooth voltage 13, which is shown in FIG. 9 c is shown at 14, enables a current to flow in the collector circuit of the transistor VT 2, as shown in FIG. 9d is shown at 15, with the resultant generation of rows 10 of output pulses only in alternating half-periods, as shown in FIG. 9 e is shown, which also shows the influence of the control voltage applied to terminals e and /.

Diodes MR 10 and MR 11 isolate the bases of the transistors VT 2 and VT 4 from one another while allowing the control voltage to pass through.

A capacitor C 9 is added, which prevents a small pulse from occurring when the voltage 11 is shown in FIG. 9 a falls to the switching level 16 and the sawtooth voltage 13 according to FIG. 9 b has not risen above the switching level. A capacitor C1 provides the same result in the circuit assigned to the transistor VT 4.

The output of the transistor VT 3 is taken from connections g and h of the transformer Tl and the output of the transistor VTA is taken from connections / and k of a transformer T 2 . These two outputs can then be fed to the ignition electrode circuits of two thyristors in the actuator. Resistors i? 16 and i? 17 form current limiters for the ignition electrode circuits.

Another modified embodiment of the circuit arrangement is shown in two sections in FIGS. 10 and 11, in which the AC input is rectified by diodes D1, D2, D 3 and D 4 and smoothed by the capacitor C1 in order to generate a direct current feeding the circuit arrangement . The transistor VTl is designed so that it is usually turned on by one of the input waves which is negative with respect to the positive DC supply line.

When the AC input passes through zero, transistor VT 1 is turned off and the voltage on its collector tries to assume the potential of the negative feed line. The amplitude of this voltage is limited by a Zener diode D 7 and a diode D 6 connected in series with it, and the capacitor CI is charged to this limited negative potential during the period during which the transistor VT 1 is switched off.

When the transistor VTl is in the conductive state, a diode D 5 isolates the capacitor C 2 from the negative feed line. The values of the capacitor C 2 and of resistors R 115 and R 126 can be changed by adding additional components, as is indicated in FIG. 10 in dashed lines. Both the capacitor C 2 and the resistors R 115 and R 126 and the additional components can be plugged in. When transistor VTl is turned back on, capacitor C 2 discharges through resistor R 126 to produce a sawtooth waveform.

The DC control voltage applied to the terminals e and / and the sawtooth voltage generated at the capacitor CI are mixed with one another and compared with the direct current flowing from the positive feed line via the base-emitter circuit of a transistor VT 14, and the sawtooth voltage generated in this way is further amplified by means of a transistor VT 15 in order to obtain a faster rise time.

The output from the emitter of the transistor VT 15 is split and via two resistors R 112 and R 114 at Xl and X1 to the base circuits

ίο applied by output transistors VT 16 and VT 17 (Fig. 11), which with their associated components form a free-running blocking oscillator. The base circuits of the transistors VT 16 and VT 17 are kept positive with respect to their emitters in alternating half-cycles by means of transistors VT 12 and VT13 , which are kept switched on by the incoming alternating current wave via resistors A108 and R 111, respectively. Resistors R 109 and RUO hold the transistors

ao VTlI and VT13 switched on during the transition period at the beginning and at the end of each half-period (for example over 5 °). Transformers T 11 and Γ12 supply two groups of synchronized separate outputs via their individual secondary windings and limiting resistors R 116 to R 118 or i? 120 to i? 123.

For this purpose 2 sheets of drawings

209 581/119

Claims (3)

Patent claims: 1. Circuit arrangement for controlling an actuator containing at least one thyristor, via which a consumer is fed from an alternating current source, containing a pulse generator for generating firing pulses for the thyristor or thyristors in such a way that the firing frequency of the thyristor or thyristors is equal to the simple or an integer Multiples of the frequency of the alternating current source and the phase position of the ignition times can be changed according to the phase position of a control signal, characterized in that the pulse generator (4) has a free-running blocking oscillator (VT3, Tl, C 4, R9) whose repetition frequency is large compared to the frequency the alternating current source, and the blocking oscillator (VT 3, Tl, C4, R9) can be triggered by the control signal in such a way that each time the control signal occurs, it generates a series of pulses with the repetition frequency, which either as such or after passing through an integrating circuit ( MR1, MR8, C5, C6, R 10, R 11) are fed to the ignition electrode of the thyristor or the ignition electrodes of the thyristors (2). 2. Circuit arrangement according to claim 1, characterized in that the pulse train is applied to the ignition electrode of the thyristor or the ignition electrodes of the thyristors (2) via a transformer (Tl, Tl). 3. Circuit arrangement according to claim 1 or 2, characterized in that the integrating circuit consists of a diode (MR 7 or Mi? 8), a charging capacitor (C 5 or C 6) and a discharge resistor connected in parallel to the charging capacitor (R 10 or R 11) exists.