DE102018009494A1 - Method and control circuit for driving elnes thyristors or triacs - Google Patents

Abstract

A triac (1) is ignited by a control circuit (4) after a zero voltage crossing (tN0) of an AC voltage source (3) by means of a gate current pulse (IP1). In an adjustment phase (P10), the control circuit (4) determines an ignition pulse duration (TL) of the gate current pulse (IP1) for igniting the triac (1) so that the current (IR) through the triac (1) after the end of the gate current pulse (IP1) reached at least one latching current value (IL). In an operating phase (P20), the control circuit (4) controls the triac (1) after a voltage zero crossing (tN0) of the AC voltage source (3) with a gate current pulse (IP1) with the determined ignition pulse duration (TL) and then monitors a current flow through the triac (1) to adjust the determined ignition pulse duration (TL) if necessary.

Description

The present invention relates to a method for driving a thyristor or triac, the thyristor or triac being ignited by a control circuit after a voltage zero crossing of an AC voltage source by means of a gate current pulse, and to a corresponding control circuit.

Thyristors and triacs are ignited by a current at the gate electrode, i.e. switched to conductive and remain conductive after switching on even without gate current until the current flow through the thyristor or triac falls below a so-called holding current. While thyristors can only switch in one direction and thus act like a diode when switched on, triacs functionally represent an anti-parallel connection of two thyristors and can thus switch alternating current. In principle, it is possible to keep the thyristor or triac permanently switched on by means of a continuous gate current. On the other hand, the thyristor or triac can also be ignited by gate current pulses after a zero voltage crossing of the AC voltage source, as a result of which the energy consumption of the control can be reduced.

It is the object of the invention to provide improved control of a thyristor or triac with reduced energy consumption and high reliability.

This problem is solved by the teaching of the independent claims. Particularly advantageous refinements and developments of the invention are the subject of the dependent claims.

According to a first aspect of the invention, the method for driving a thyristor or triac, wherein the thyristor or triac is ignited by a control circuit after a voltage zero crossing of an AC voltage source by means of a gate current pulse, has an adjustment phase in which the control circuit has an ignition pulse duration of the gate current pulse for igniting the Thyristors or triacs are determined so that the current through the thyristor or triac reaches at least one latching current value after the end of the gate current pulse, and an operating phase in which the control circuit drives the thyristor or triac with a gate current pulse with the determined ignition pulse duration after a voltage zero crossing of the AC voltage source and then monitors a current flow through the thyristor or triac.

By automatically determining a suitable ignition pulse duration by the control circuit in the setting phase, an optimally possible ignition pulse duration can be set, with which reliable and energy-saving control for firing the thyristor or triac can be achieved. By monitoring the current flow through the thyristor or triac in the operating phase, correct and energy-saving control for triggering the thyristor or triac can be achieved. The monitoring also enables an adaptive adaptation of the control of the thyristor or triac in order to achieve a reliable and energy-saving function. The energy saving effect is particularly evident with thyristors and triacs, which require high gate currents to ignite. The reduced energy consumption can also reduce the heat generation of the thyristor or triac.

The control circuit preferably adjusts the set ignition pulse duration if the monitoring shows that there is no current flow through the thyristor or triac after the end of the gate current pulse.

The current flow through the thyristor or triac is preferably monitored using a gate voltage between the gate connection and the cathode connection of the thyristor or triac. If the gate voltage exceeds a predetermined limit value, there is a current flow through the thyristor or triac.

In one embodiment of the invention, the control circuit controls the thyristor or triac with a further gate current pulse with a hold pulse duration in the operating phase before the voltage source crosses zero. With this configuration, the control circuit preferably also determines a hold pulse duration for the further gate current pulse before the zero voltage crossing of the AC voltage source in the setting phase, so that the current through the thyristor or triac does not fall below a hold current value before the start of the further gate current pulse. The control circuit preferably adjusts the set holding pulse duration if the monitoring shows that there is no current flow through the thyristor or triac before the start of the further gate current pulse.

In one embodiment of the invention, the thyristor or triac is only after one predetermined phase angle after a zero voltage crossing of the AC voltage source is ignited by means of a gate current pulse. With such a phase control, the control circuit determines the ignition pulse duration in dependence on the predetermined phase angle in the setting phase and controls the thyristor or triac in the operating phase only after the predetermined phase angle after a zero voltage crossing of the AC voltage source with a gate current pulse with the determined ignition pulse duration.

In this configuration, the control circuit preferably determines several different ignition pulse durations for different phase angles in the setting phase.

In a further embodiment of the invention, the control circuit repeats the adjustment phase regularly. In this way, the setting of the ignition pulse duration and / or the holding pulse duration can be adapted to possibly changing operating conditions or functional properties of the thyristor or triac.

According to a second aspect of the invention, the control circuit for driving a thyristor or triac includes a pulse generator for generating a gate current pulse at a gate terminal of the thyristor or triac, a current flow monitoring device for monitoring a current flow through the thyristor or triac, and a controller which is connected to the pulse generator and the Current flow monitoring device is connected, wherein the controller is designed to carry out the method described above for driving a thyristor or triac according to the invention.

In one embodiment of the invention, the current flow monitoring device has a voltage detection device for detecting a gate voltage between the gate connection and the cathode connection of the thyristor or triac.

The control circuit preferably also has a memory connected to the controller for storing the determined ignition pulse duration, the adapted ignition pulse duration, the determined hold pulse duration and the adapted hold pulse duration.

• 1 ein Schaltbild einer Triac-Schaltung mit einer Steuerschaltung gemäß der vorliegenden Erfindung;
• 2 ein Strom-Zeit-Diagramm zum Erläutern des Funktionsprinzips einer Steuerschaltung gemäß der vorliegenden Erfindung;
• 3 ein Ablaufdiagramm eines Verfahrens zum Ansteuern eines Triacs gemäß einem Ausführungsbeispiel der vorliegenden Erfindung;
• 4 ein Ablaufdiagramm einer Einstellphase zum Einstellen der Zündimpulsdauer für das Verfahren von 3; und
• 5 ein Ablaufdiagramm einer Einstellphase zum Einstellen der Halteimpulsdauer für das Verfahren von 3.

The above and further features and advantages of the invention can be better understood from the following description of preferred, non-limiting exemplary embodiments with reference to the accompanying drawing. It shows, mostly schematically:

• 1 a circuit diagram of a triac circuit with a control circuit according to the present invention;
• 2nd a current-time diagram for explaining the principle of operation of a control circuit according to the present invention;
• 3rd a flowchart of a method for driving a triac according to an embodiment of the present invention;
• 4th a flowchart of an adjustment phase for adjusting the ignition pulse duration for the method of 3rd ; and
• 5 a flowchart of an adjustment phase for adjusting the hold pulse duration for the method of 3rd .

Referring to 1 and 2nd First of all, the structure and the mode of operation of a triac circuit with a control circuit according to the invention are explained as examples.

The triac circuit contains a series connection from a triac 1 and a burden 2nd working on an AC voltage source 3rd connected. The triac 1 is controlled by a control circuit 4th controlled.

The control circuit 4th has a pulse generator 6 for generating gate current pulses IP1 , IP2 with a gate current value IG connected to the gate electrode of the triac 1 be placed. The pulse generator 6 is controlled by a controller 5 operated. To recognize the correct times of the gate current pulses IP1 , IP2 is a phase synchronization 7 with the AC voltage source 3rd intended. The control 5 is also with a memory 8th for storing various parameter values, a timer 9 and a current flow monitoring device for monitoring a current flow through the triac 1 connected. In this exemplary embodiment, the current flow monitoring device has a voltage detection device 10th for detecting a gate voltage Basement between the gate electrode and the cathode of the triac 1 on.

The triac is in the switched off or blocked state 1 high impedance and corresponds to an open switch and thus blocks the current IR through the triac 1 and thus also through the load 2 ( IR = 0). At the gate electrode of the triac 1 there is no gate current (IG = 0). In this operating state, the load falls 2nd no voltage from (UR = 0) and falls over the triac 1 the AC voltage U.N. from (UT = UN). Due to the lack of current flow through the triac, the gate voltage UG = 0.

After a voltage zero crossing tN0 becomes the triac 1 with a gate current pulse IP1 with a gate current value IG ignited. The triac is in the ignited or switched on state 1 low impedance and corresponds to a closed switch that has a current IR through the triac 1 and by the load 2nd according to the AC voltage U.N. enables. In this operating state, the load falls 2nd about the AC voltage U.N. from (UR = UN) and falls over the triac 1 no voltage from (UT = 0). Because of the current flow IR through the triac 1 is a gate voltage Basement detectable which is a limit UGM exceeds.

The ignition pulse duration TL of the gate current pulse IP1 is chosen so that the current IR through the triac after the end of the gate current pulse IP1 a lock current value IL exceeds, so the triac 1 even without gate current IG remains switched on. To prevent the triac 1 turns off when the electricity IR through the triac 1 a holding current value IH falls below, then before the next voltage zero crossing tN0 another gate current pulse IP2 to the gate electrode of the triac 1 placed to the triac 1 keep on. The hold pulse duration TH the further gate current pulse IP2 is chosen so that the current IR through the triac at the beginning of the further gate current pulse IP2 still above the holding current value IH lies. Is the phase duration of a voltage half-wave with TP is referred to as the further gate current pulse IP2 started at a time tn0 + TP - TH.

This basic functioning of a triac and its control are known to the person skilled in the art. A more detailed explanation can therefore be dispensed with.

Referring to 3rd to 5 is now an example of an embodiment of an inventive control of the triac 1 explained in more detail.

As in 3rd or in the 3A and 3B illustrated, contains the inventive method for driving the triac 1 an adjustment phase P10 and an operational phase P20 , with the operating phase in an ignition phase P22 , a monitoring phase P24 and a hold phase P26 can be broken down.

In the adjustment phase P10 are from the control circuit 4th an ignition pulse duration TL for the gate current pulse IP1 after a voltage zero crossing tN0 and a hold pulse duration TH for the further gate current pulse IP2 before a voltage zero crossing tN0 determined as in 4th respectively. 5 illustrated. The adjustment phase P10 can also be referred to as the learning phase, since the pulse durations TL , TH not set by a user, but by the control circuit 4th be determined automatically.

As in 4th illustrated by way of example, includes setting the ignition pulse duration TL in the setting phase P10 through the control circuit 4th the steps S120 to S126 .

In the first step S120 becomes the ignition pulse duration TL initially to a low initial value TL0 set. Then up to voltage zero crossing tN0 waited (step S121 ). When the voltage zero crossing is reached tN0 ("J" in S121 ) will be in the next step S122 a gate current pulse IP1 with a gate current value IG and the ignition pulse duration TL to the gate electrode of the triac 1 placed to the triac 1 turn on. After the ignition pulse duration has expired TL will in step S123 the gate current pulse IP1 ended (IG = 0).

The controller then checks 5 with the help of the voltage detection device 10th whether the gate voltage Basement a predetermined limit UGM has reached out on the presence or absence of a current flow through the triac 1 close. Exists after the end of the gate current pulse IP1 a current flow through the triac 1 ("J" in S124 ) is the ignition pulse duration TL long enough for the current IR through the triac the latching current value IL exceeds and the triac 1 even without gate current IG remains switched on. In this case, the current value of the ignition pulse duration TL In the storage room 8th the control circuit 4th saved (step S125 ) to in the ignition phase P22 the operating phase P20 for the gate current pulse IP1 to be used.

Exists after the end of the gate current pulse IP1 no current flow through the triac 1 ("N" in S124 ) is the ignition pulse duration TL too short, so electricity IR through the triac not the latching current value IL reached and the triac 1 without gate current IG turns off. In this case, step S126 the current value of the ignition pulse duration TL increased by a pulse duration difference dt and the method from step S122 (or alternatively from step S121 ) repeated until the increased ignition pulse duration TL is sufficient ("J" in S124 ).

As in 5 illustrated by way of example, includes setting the hold pulse duration TH in the setting phase P10 through the control circuit 4th the steps S140 to S144 .

In the first step S140 becomes the hold pulse duration TH initially to an initial value TH0 set. The initial value can be, for example, the determined ignition pulse duration TL be. Then in step S141 checked whether at the beginning of the further gate current pulse IP2 , ie current at time tN0 + TP - TH IR through the triac 1 flows. If this is not the case ("N" in S141 ), the hold pulse duration TH in step S142 be increased so that the further gate current pulse IP2 starts earlier. The increased hold pulse duration TH is then in memory 8th saved (step S143 ) in the holding phase P26 the operating phase P20 for the further gate current pulse IP2 to be used. Exists against Start of the further gate current pulse IP2 another flow of electricity IR through the triac 1 ("J" in S141 ), the hold pulse duration TH in step S144 shortened by dT and the process goes back to step S141 .

In an alternative embodiment of the invention, it is also possible to adjust the holding pulse duration TH through the control circuit 4th to be dispensed with. In this case the hold pulse duration TH for example on the value of the determined ignition pulse duration TL set so that the further gate current pulse IP2 is certainly long enough so that the triac before the next voltage zero crossing tN0 remains switched on.

After completing the adjustment phase described P10 the control circuit goes 4th in the operating phase P20 about where the triac 1 controlled according to the settings and the proper and energy-saving functioning of the triac 1 be monitored.

The ignition phase P22 the operating phase P20 starts at a voltage zero crossing tN0 (Step S220 ). To zero voltage crossing tN0 becomes the gate current pulse IP1 started (step S222 ) and for the determined ignition pulse duration TL maintain (step S224 ).

After the ignition pulse duration has expired TL ("J" in S224 ) becomes the gate current IG switched off (step S240 ) and the monitoring phase begins P24 . In step S241 is by the voltage detection device 10th the control circuit 4th the gate voltage Basement detected. In step S242 becomes the detected gate voltage Basement with a predetermined limit UGM compared. Reaches the gate voltage Basement the limit UGM ("J" in S242 ), the control recognizes 5 a current flow IR through the triac 1 . This means that the ignition pulse duration TL for igniting the triac 1 is sufficient.

Reaches the gate voltage Basement however, the limit UGM not ("N" in S242 ), the control recognizes 5 that no current flow IR through the triac 1 exists. This means that the ignition pulse duration TL for igniting the triac 1 was too short and the triac 1 after the gate current pulse has ended IP1 turns off. In step S243 therefore the gate current pulse is immediately again IP1 activated the triac 1 turn on. Then the monitoring phase with step S240 continued. Optionally, after reactivating the gate current pulse IP1 in step S243 also the ignition pulse duration TL be adjusted. This adjustment is carried out, for example, analogously to the setting phase 4th .

That leaves the triac 1 after the gate current pulse has ended IP1 with the ignition pulse duration TL or the extended gate current pulse IP1 is switched on, until the time tN0 + TP - TH of the planned further gate current pulse IP2 waited. As long as this time has not yet been reached ("N" in S245 ), is by the voltage detection device 10th the control circuit 4th the gate voltage Basement captured (step S246 ). In step S247 becomes the detected gate voltage Basement with a predetermined limit UGM compared. Reaches the gate voltage Basement the limit UGM ("J" in S247 ), the control recognizes 5 a current flow IR through the triac 1 . This means that the triac 1 is still in the switched-on state and the further gate current pulse IP2 correctly had not yet to be started. Monitoring of the current flow then continues.

Reaches the gate voltage Basement however, the limit UGM not ("N" in S247 ), the control recognizes 5 that no current flow IR more through the triac 1 exists. This means that the hold pulse duration TH is too short and the triac 1 even before the start of the further gate current pulse IP2 has switched off. In step S248 therefore becomes a gate current immediately IG to the triac 1 placed to the triac 1 turn on again. Optionally, after activating the gate current IG in step S248 also the hold pulse duration TH be adjusted. This adjustment is carried out, for example, analogously to the setting phase 5 .

That leaves the triac 1 however, until the planned start time of the further gate current pulse IP2 switched on ("J" in S247 ), the holding phase then begins P26 . In step S260 then the further gate current pulse IP2 started the flow of electricity IR through the triac 1 maintain even when the current IR falls below the holding current value ICH. The further gate current pulse IP2 then remains until the next voltage zero crossing tN0 + TP (step S261 ).

The operating phase P20 is then for the next voltage half-wave with the same steps S220 to S261 continued.

While the invention is based on the above 1 to 5 The example of a triac control without phase angle has been explained, the present invention can also be implemented in connection with a so-called leading edge control. In the case of a phase control, the gate current pulse IP1 only after a certain phase angle W after the voltage zero crossing tN0 started as in 2nd indicated. Likewise, in the case of a phase control, the further gate current pulse IP2 already a certain phase angle before the voltage zero crossing tN0 be ended.

In the case of such a leading edge control, the adjustment phase P10 from the control circuit 4th different ignition pulse durations TL and possibly also different holding pulse durations TH for different phase angles W determined. In the operating phase P20 selects the control 5 then the determined pulse durations TL , TH for the desired phase angle W out to the operational phase P20 with these pulse durations TL , TH perform.

While the invention is based on the above 1 to 5 Using the example of a triac circuit, the person skilled in the art can also transfer the concept of the present invention to the control of a thyristor.

Reference symbol list

1

Triac

2nd

load

3rd

AC voltage source

4th

Control circuit

5

control

6

Pulse generator

7

Phase synchronization

8th

Storage

9

timer

10th

Voltage detection device

I.

electricity

IG

Gate current (worth)

IH

Holding current value

IL

Snap current value

IP1

Gate current pulse after voltage zero crossing

IP2

Gate current pulse before voltage zero crossing

IR

Current through load or triac

t

time

dT

Pulse duration difference

TH

Hold pulse duration

TH0

Initial value holding pulse duration

TL

Firing pulse duration

TL0

Initial value of the ignition pulse duration

tN0

Time of zero voltage crossing

TP

Phase duration voltage half-wave

Basement

Gate voltage

UGM

Gate voltage limit

U.N.

AC voltage

UR

Voltage drop over load

Subtitles

Voltage drop across triac

W

Phase angle

Claims (11)

Method for controlling a thyristor or triac (1), the thyristor or triac (1) being triggered by a control circuit (4) after a zero voltage crossing (tN0) of an AC voltage source (3) by means of a gate current pulse (IP1), comprising: a setting phase (P10) in which the control circuit (4) has an ignition pulse duration (TL) of the gate current pulse (IP1) for igniting the thyristor or triac (1), so that the current (IR) through the thyristor or triac (1) after the end the gate current pulse (IP1) reaches at least one latching current value (IL), determined (S120 - S125); and an operating phase (P20) in which the control circuit (4) controls the thyristor or triac (1) after a zero voltage crossing (tN0) of the AC voltage source (3) with a gate current pulse (IP1) with the determined ignition pulse duration (TL) (S222, S224) and then monitors a current flow through the thyristor or triac (1) (S241, S242, S246, S247). Procedure according to Claim 1 , in which the control circuit (4) adjusts the ignition pulse duration (TL) (S244) if the monitoring (S241, S242) shows that after the end of the gate current pulse (IP1) there is no current flow through the thyristor or triac (1). Procedure according to Claim 1 or 2nd , in which the current flow through the thyristor or triac (1) is monitored using a gate voltage (UG) between the gate connection and the cathode connection of the thyristor or triac (1) (S241, S242, S246, S247). Method according to one of the preceding claims, in which the control circuit (4) in the setting phase (P10) furthermore a hold pulse duration (TH) for a further gate current pulse (IP2) before a voltage zero crossing (tN0) of the AC voltage source (3), so that the current (IR ) by the thyristor or triac (1) before the start of the further gate current pulse (IP2) does not fall below a holding current value (IH), determined (S140 - S144); and the control circuit (4) in the operating phase (P20) before a zero voltage crossing (tN0) of the AC voltage source (3) the thyristor or triac (1) with a further gate current pulse (IP2) with the determined hold pulse duration (TH) controls (S260, S262). Procedure according to Claim 4 , in which the control circuit (4) adjusts the hold pulse duration (TH) (S249) if the monitoring (S246, S247) shows that before the start of the further gate current pulse (IP2) there is no current flow through the thyristor or triac (1) . Method according to one of the preceding claims, in which the thyristor or triac (1) is ignited only after a predetermined phase angle (W) after a voltage zero crossing (tN0) of the AC voltage source (3) by means of a gate current pulse (IP1); the control circuit (4) determines the ignition pulse duration (TL) as a function of the predetermined phase angle (W) in the setting phase (P10); and the control circuit (4) the thyristor or triac (1) in the operating phase (P20) only after the predetermined phase angle (W) after a zero voltage crossing (tN0) of the AC voltage source (3) with a gate current pulse (IP1) with the determined ignition pulse duration (TL) activated (S222, S224). Procedure according to Claim 6 , in which the control circuit (4) determines several different ignition pulse durations (TL) for different phase angles (W) in the setting phase (P10). Method according to one of the preceding claims, in which the control circuit (4) repeats the setting phase (P10) regularly. A control circuit (4) for driving a thyristor or triac (1), comprising: a pulse generator (6) for generating a gate current pulse (IP1, IP2) at a gate connection of the thyristor or triac (1); a current flow monitoring device (10) for monitoring a current flow through the thyristor or triac (1); and a controller (5) connected to the pulse generator (6) and the current flow monitoring device (10), the controller (5) for performing a method for driving a thyristor or triac (1) according to one of the Claims 1 to 8th is designed. Control circuit after Claim 9 , in which the current flow monitoring device has a voltage detection device (10) for detecting a gate voltage (UG) between the gate connection and the cathode connection of the thyristor or triac (1). Control circuit after Claim 9 or 10th , further comprising: a memory (8), which is connected to the controller (5), for storing the determined ignition pulse duration (TL), the adapted ignition pulse duration (TL), the determined hold pulse duration (TH) and the adapted hold pulse duration (TH).

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