DE2031439C3 - Circuit arrangement for current limitation in an alternating current switch that clocks depending on the control voltage - Google Patents

Description

a Schmitt current switch for power control with a thyristor alternately charged capacitor through the FR-PS 1354318 known trigger controls, which in a known manner over After that, with the help of a control capacitor, synchronization comparison elements and a bidie Thyristors are switched and an ignition pulse generator for the chip-stable trigger stage tion of the control capacitor synchronous ignition pulses S thyristors of the AC switch downstream The clock ratio of each is only one tet

Current half-cycle through-switching alternates from- Furthermore, according to a further embodiment, the

switch can through the consumer current or invention to limit the current in a first can be influenced by the consumer voltage. Current limiting stage to a load resistor

The influence of the clock ratio through the io dem the actual value of the consumer current as pulsed current has the advantage that the rectified voltage rende through load changes with one of the above and due to fluctuations in the alternating voltage averaging a clock period of the consumer current Current fluctuations with a regulated value proportional to the effective value is present, a the and the thyristors of the AC switch from an ohmic resistor, a diode and in intermittent switching operation thermally favorable 15 that of the control voltage and the feedback ger can be exploited. Taking into account consumer voltage charged capacitor bestegiing the maximum permissible effective value of the series connection connected in parallel, in which Consumers switched alternating current periods, with the diode when the nominal current strength is exceeded which the thyristors with a small clock ratio and the AC circuit as well as when reaching a correspondingly low modulation are loaded, 20 specific charging voltage of the capacitor in the Applying this method is a limit on the conduction state is controlled and the condensation is set. In addition, even with a normal clock, charging is carried out in the opposite direction to the control voltage ratio as a result of the alternating current switch.

returned actual current value depending on the level of the

Current end value the control characteristic of the switch as tion of the invention for limiting the current in changed unfavorably. the second current limiting stage to the burden

The invention is based on the object of a resistance to the first current limiting stage a circuit arrangement to limit the current of the ÄC element to smooth the pulsating DC voltage input the type described the limit, the voltage and the capacitor of the ÄC member on subordinate current control with a small pulse ratio - an ohmic resistor and a zener diode nis is set, as well as that in parallel with a normal clock ratio composed constant voltage divider ratio unfavorable change in the control characteristic switched from which the DC voltage at the ohmdes To bypass the AC switch. see resistance of a phase angle

The solution to this problem consists of the sawtooth chip generated according to the invention in a known manner with the actual value of the load voltage, and there are voltage subordinate, influencing the clock ratio - the in the intersection of the sawtooth voltage and the voltage regulation as well as in two current limits. Synchronization stages obtained from the direct voltage, namely a first pulse via a separate synchronization Verder rated current intensity of the alternating current circuit in the DC link to the ignition pulse generator for the thyristor-subordinate voltage control and a 40 ren of the alternating current switch,
second when reaching the depending on the chosen- An embodiment of the invention is in the

th clock frequency smallest possible clock ratio drawing and is shown in more detail below and that for the intermittent cycle operation of the described. It shows

Thyristors permissible effective current value intervene- F i g. 1 is a block diagram of an alternating current

fende, the current through phase control of the changeover switch with a circuit arrangement according to the self-voltage-time area at this value limit the invention, which is used as a power control element for an elekzende Current limit level. fresh radiator (consumer) for temperature

With a sound control designed according to the invention can be used,

arrangement with control voltage-dependent clock- F i g. 2 the circuit of the first and the second

With the AC switch, it is now possible to set 50 current limiting stages in one circuit arrangement Power supply also for consumer rejection according to the invention.

would have a large cold-to-warm ratio in order to simplify the explanation of the invention

to control and regulate according to the clock principle. Up is in FIG. 1 the block diagram of a single phase a scheme has been proposed for this, alternating current switch, consisting of two opposite the two thyristors 1 and 2 connected in parallel to a thyratron-Steil 55, for example, element acting control voltages, the actuator is accordingly a Zündweils for these thyristors Adjust only by voltage cut-off or pulse generator 3 provided, which is activated by a Synnur switch clocked, but this scheme is controlled chronizing circuit so that it increases is used to limit the current (DT-OS at least in every positive zero crossing of the means 2,018,830). 60 of the alternating current switch 1, 2 to a consumer 4

In the subordinate voltage regulation, 1% single-phase alternating voltage to be switched takes place according to an embodiment of the invention, which generates a back-ignition pulse, in which case the timing of the actual value of the consumer voltage exists as a ratio of one. The pulse ratio is in the pulsating rectified voltage in such a way, remaining dependent on the size of the input, that the voltage is one of the control voltage over 65 of the in the FIG. 1 framed control part S to a KC combination, which determines the clock frequency, is guided control voltage U _R , which is taken from a temperature-loaded controller 6 and from the pulsating rectifier 6. The elements 4, 6, S, th voltage via an ohmic resistor ent- (1, 2), 4 together form a temperature control

circuit, in which the power-applied multi-pulse ignition pulse generator 3 is put into operation at a constant load. of the consumer 4 with a corresponding one. This is designed in a known way, pulse ratio, constant at a certain value - that it can be regulated at every zero crossing of the alternating voltage. The control voltage sends an ignition pulse to the thyristors of the alternator, first the capacitor 7 and then the condenser switch. The AC switch 1, 2 gate 8 at the input of the control part 5 is then closed, and when connected, the RC capacitor 8, which determines the clock frequency, can be activated by the pulsating DC voltage of the combination? ', Tj 8V 8 in the displayed Polarity of the rectifier bridge ΪΓ across the resistor 10 and load. Using a circuit consisting of a rectifier bridge 11 ', a reloading process unohmical resistor 10 and a rectifier io set, in which the capacitor 8 is discharged 11' so that the consumer voltage is rectified until the lower response voltage of the Schmitttet and is reached as a pulsating DC voltage in the trigger 12. Then the Schmitt circuit is impressed, the capacitor 8 trigger 12 resumes its initial state, and it discharges again until the thyristors 1, 2 go out, disappears at the inputs I, Γ the comparison and the AC switch is opened. Charging elements 13, 13 'represent the control potential. The input Γ and discharge time determine the clock ratio and the comparison element 13 'is, as an inverting one, the clock frequency of the AC switch. gear so that the next positive

The temperature control circuit is subordinated to the actual value of the control pulse of the clock generator 14 ', a control _{potential consumer voltage M 4,} a voltage control circuit to the input II "of the bistable flip-flop 15, in which the actual value of the consumer voltage 20 is switched, the bistable flip-flop so back M ₄ as a pulsating rectified voltage U _9. This also puts the multi-pulse pulse at a load resistor 9 and further via the transmitter 3 out of operation again and terminates the closing resistor 10 at the capacitor 8 at the time of the AC switch 1, 2. The now AC combination riickge ^ Unrt is, the rectified voltage in the opposite as lasts from the next opening time of the switch as long, until the clamping polarity is loaded at the input of the control part. 5 the consumer voltage M ₄ planning l / ₈ the threshold of the Schmitt trigger 12 is detected with a voltage converter 11 and exceeded again.

rectified by the bridge rectifier 11 '. In the block diagram of FIG

at the output of the load resistor 9 connected current limiter 20 is indicated with a tet at the input. Through this voltage control loop, the current transformer pulse ratio connected to the consumer circuit 30 is also influenced in the sense that the 16 current for the detection of the actual value of the consumer effects of fluctuations in the alternating voltage and with two outputs. When the power supply to the consumer is first switched off, an ohmic resistor 17 and a diode 18 are regulated. As will be shown below, the already mentioned capacitor 8 is tuned in series, which switches on the basis of the control voltage U _R 35. The second output is with a one and the fed back actual value of the transition I '"one between the bistable multivibrator 15 user voltage K ₄ resulting curve of the comparator voltage connected to the pulse generator 3 on the capacitor 8 in cooperation of the 19, which is controlled at the second input ΙΓ "by the two response values of one of the condenser flip-flop 15, capacitor voltage U ₈ controlled Schmitt trigger 12 40 To describe the current limiting stage 20, the clock ratio and also the clock frequency. Reference is made to FIG. 2 below. The latter can be seen from the dimensioning of the EIe that the detected consumer elements 7, 7 ', 8, 8' can be specified. The Schmitt trigger 12 current by means of a bridge rectifier 21 are equal to two synchronization comparator members 13,13 'and connected downstream as pulsating rectified, each having two inputs I, Π; Γ, II 'up- 45 voltage IZ ₈₂ is applied to a burden 22 The burden point. The trigger output is connected to the inputs I 22 as the first limiting stage, the aforementioned comparator 13 and 13 '. A series connection of a resistor 17, a diode of the alternating voltage u _w controlled clock 14 18 and of the control voltage U _K and the returns with each positive zero crossing of the alternating voltage B ₄ charged capacitor 8 voltage U _n , a positive control pulse to the so connected in parallel. The Sroadler 1 <> and the EIe input Π of the comparison element 13 and a similar element of this circuit are dimensioned so that the clock 14 'at each positive zero crossing that the diode 18 is sufficiently far into the passage, e.g. also a positive control pulse at the input was controlled so that the entire resistance gaag W of the comparison element 13 '. The output of the comparison element 13 is considerably venaiadert «rad of the comparison element 13 is charged with a first input I" 55 capacitor 8 opposite to the polarity of the Re- and the output of the comparison element 13 'is additionally charged with a voltage voltage, because the branched input II " a bistable flip-flop 15 braecherstroni i ₄ the current strength of the alternating · connected. Circuit exceeds this zis / fice charge

The larger the requested control of the capacitor 8 at the input of the control part 5 as eracatBca, the result is voltage, the faster the condensation increases so that the existing Verbrancherstrom by Verriasatorspannung CZ to _8, the earlier the delay of Taktverbältnisses speaks is reduced . Schmitt trigger 12 and switches a control potential The F i g. 2 it can also be seen that the Börde

As the input I of the comparison device 13. As long as 22 further em GBttmigSHRC-GEed 23, 24 and da6 this control potential is ordered at input I, the capacitor 24 of the "C-Göedes" is re & eamit each control pulse of the clock 14 darcfa the 65 circuit of a Vorwio ^ rstaades 25 rad of a Zener diode Vergfetchsglied 13 is connected in parallel to the input I "of the flip-flop 26 Am Knnsar 2 4 sweeps 15 up, the bean first control pulse of a nearly gglä Gh d

Clock 14 is tilted and thus the subsequent large value is over one

· ■: now If.nge Span -..- 12

user current I _{4 is} proportional to the mean effective value. The polarity of the Zener diode 26 is such that it is biased by this DC voltage in the Zener device. If the DC voltage exceeds a certain limit value, a Zener current / _2e flows through the Zener diode, and a DC voltage U ₂ is created across the resistor 25 - with a magnitude that increases linearly with the DC voltage across the capacitor 24. This DC voltage l / ₂₅ is superimposed on a sawtooth C _27, which is generated at a synchronized with the AC voltage multivibrator 27th The flip-flop 27 switches a control potential having a phase angle to the input V "of the sync comparing section 19 with the voltage l / results from the comparison of the voltage LZ _{27 25th}

The circuit described above works as a second current limiting stage 23, 24, 25, 26 of the AC switch. As long as the consumer _{current / 4} does not exceed the nominal current strength of the AC circuit or has only exceeded it so far that the first current limiting stage is effective,

but the clock ratio has not yet reached the lowest possible value, the zener current I _{26 is} so low that the positive output potential of the bistable flip-flop 15 each time the zero crossings of the

S AC voltage is switched through to the ignition pulse generator 3, so that the thyristors 1 and 2 are also ignited at the zero crossings of the AC voltage. The Zener voltage of the Zener diode 26 is provided so high that the capacitor _{voltage U 24} exceeds the Zener voltage t / _2e when the load _{current i 4} still rises after it has been reduced to the smallest possible clock ratio. With the consumer current then increasing further, the DC voltage t / _{85 increases} accordingly

and it results in a phase shift of the ignition pulses of the pulse generator 3, the one Reduction of the consumer current through phase control of the alternating voltage and can go up to the complete blocking of the thyristors.

ao The intervention of the second current limiting stage is essentially determined by the level of the Zener voltage t / _ge .

1 sheet of drawings

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Claims (4)

1 2 second current limiting stage the burden claims: resistance (22) an ÄC element (23, 24) for smoothing the pulsating DC voltage (U1J) and 1. Circuit arrangement to limit the current of the capacitor (24) of the ÄC element a constant-thyristor per load circuit consisting of a voltage divider that is clocked depending on the control voltage, an ohmic resistor (25) and at least one counter-parallel connection of two Zener diodes (26) per load circuit is, of which the AC switch, in which the clock voltage (U ₂₅ ) superimposed on the ohmic resistance by one of the control voltage, stood (25) an actual value generated by means of a phase connection from the consumer circuit in the synchronization flip-flop (27) is influenced (subordinated Control) and with tooth voltage in a known manner superimposed on which the thyristors are superimposed depending on the and which are controlled in the intersection of the saw voltage of a capacitor, which tooth voltage and the direct voltage (U _x ) are also used to limit the current of the synchroaisierimpulse a separate means of the alternating current holder controlled 15 th synchronization comparator (19) the alternating current is influenced, marked ignition pulse generator (3) for the thyristors (1,2) rich net by one with the Isfwert that of the alternating current holder are supplied.
Load voltage (u ₄ ) subordinate voltage regulation influencing the pulse ratio and through two current limiting levels, namely an ao first when the rated current is exceeded
of the AC circuit in the subordinate
Voltage regulation intervening and a second when reaching the selected depending on the The invention relates to a circuit arrangement Clock frequency of the smallest possible clock ratio as for current limitation with a control voltage and the intermittent clock operation of the dependent clocking, permissible current effective value (l _tll ) from at least one counter-thyristor, parallel connection of two thyristors per user intervening, the current through phase control circuit existing alternating current switch, the alternating voltage time area at this value at which the pulse ratio is superimposed by a current limiting stage (23, 24, 25, 30 voltage from the consumer circuit 26) that limits the rule. feedback actual value is influenced (subordinate 2. Circuit arrangement for the subordinate control) and in which the thyristors in dependent voltage control in an arrangement according to speed of the voltage of a capacitor controlled according to claim 1, characterized in that the voltage are also used to limit the actual value of the consumer voltage (U ₄ ) than pulsie- 35 of the rende rectified voltage (IZ ₉ ) controlled by means of the alternating current holder, in which alternating current is influenced. Such an alternating current switch is known to be controlled by the control voltage (U _H ) via a control circuit in such a way that it alternates between one or one switching frequency determining ßC combination (7, several whole alternating voltage periods long ge-T, 8, 8 ') charged and closed or opened by the pulsating 40. During the closing time rectified voltage via an ohmic voltage, the thyristors are ignited in the oppositely charged cones of the alternating capacitor (8) to be switched to the consumer, a Schmitt trigger (12). An ignition pulse generator (3) is used as the clock ratio, which in a known manner via the synchronization ratio of the closing time to the sum of the Schherungs comparison elements (13, 13 ') and a flip-flop (15) that is stable to the bi- 45 ßungs- and the opening time of the clock period and as the clock frequency the number of clocks · the thyristors (1, 2) of the alternating current switching periods per second,
ters is connected downstream. By the US-PS 3,458,726, Fig. 2, a line is 3. Arrangement according to claim 1, characterized in that gestungssteuerungsstromkreis with a thyristor is known that in the first current limiting 50 AC switch, in which the clock stage has a load resistor (22) on which the ratio by a square-wave control signal and actual value of the Veibraucherstromes (Z ₄ ) as pulsed not by an electrical quantity, z. B. a Rende rectified voltage (U ₂₂ ) with a voltage is influenced. On the other hand, through US Pat. No. 3,337,773, Fig. 5, a power control circuit with a Geeen value is applied, a power control circuit with an ohmic resistance parallel connection of two thyristors, which as an alternation ( 17), a diode (18) and which are operated by the self-current control element. Here the control voltage and the riiek-guided consumption is controlled by a subordinate current control of the overvoltage charged capacitor (8) the temperature controller changes so that the power connected to a nominal current (/ ") of the AC circuit load changes accordingly as well as when a certain charge voltage is reached and, if necessary, the load capacity of the capacitor (8) can be limited to the forward AC current. The firing angle is controlled and the capacitor opposite the thyristors is charged to the control voltage (U _R ) depending on the voltage set. tion of a control capacitor, which is itself through the 4. Arrangement according to claim 1 and partially influenced control voltage, changed. Des expanse 3, characterized in that the ren are arrangements of the type mentioned