WO2020114767A1

WO2020114767A1 - Method and control circuit for actuating a thyristor or triac

Info

Publication number: WO2020114767A1
Application number: PCT/EP2019/081865
Authority: WO
Inventors: Jerzy Kurek
Original assignee: Diehl Ako Stiftung & Co. Kg
Priority date: 2018-12-04
Filing date: 2019-11-20
Publication date: 2020-06-11
Also published as: DE102018009494A1; EP3891892A1

Abstract

A triac (1) is triggered by a control circuit (4) by means of a gate current pulse (IP1) after a voltage zero crossing (tN0) of an alternating voltage source (3). In a setting phase (P10), the control circuit (4) determines a triggering pulse duration (TL) of the gate current pulse (IP1) for triggering the triac (1) such that the current (IR) through the triac (1) reaches at least a latching current value (IL) after the end of the gate current pulse (IP1). In an operating phase (P20), the control circuit (4) actuates the triac (1) by means of a gate current pulse (IP1) having the determined triggering pulse duration (TL) after a voltage zero crossing (tN0) of the alternating voltage source (3) and subsequently monitors a current flow through the triac (1) in order to adjust the determined triggering pulse duration (TL) if necessary.

Description

METHOD AND CONTROL CIRCUIT

FOR DRIVING A THYRISTOR OR TRIAC

The present invention relates to a method for driving a thyristor or tri acs, 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 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 circuit of two thyristors and can thus switch alternating current. In principle, it is possible to keep the thyristor or triac permanently switched on by a continuous gate current. On the other hand, the thyristor or triac can also be ignited by gate current pulses after a voltage zero 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 task 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 after a voltage zero crossing gang of an AC voltage source by means of a gate current pulse is ignited by a control circuit having an adjustment phase in which the control circuit determines an ignition pulse duration of the gate current pulse for igniting the thyristor or triac, since with the current through the thyristor or triac after the end of the gate current pulse at least one Einraststromwert reached, and an operating phase in which the control circuit controls the thyristor or triac after a voltage zero crossing of the AC voltage source with a gate current pulse with the determined ignition pulse duration and then monitors a current flow through the thyristor or triac.

By automatically determining a suitable firing pulse duration by the control circuit in the setting phase, the most optimal firing 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, a correct and energy-saving control for firing the thyristor or triac can be achieved. The monitoring also enables adaptive adaptation of the control of the thyristor or triac in order to achieve a reliable and energy-saving mode of operation. 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 AC voltage source crosses zero. In this embodiment, the control circuit preferably also determines in the setting phase a hold pulse duration for the further gate current pulse before a voltage zero crossing of the AC voltage source, 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 ignited only after a certain phase angle after a voltage zero crossing of the AC voltage source by means of a gate current pulse. In such a phase control, the control circuit determines the ignition pulse duration in the setting phase as a function of the predetermined phase angle 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 firing 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 to 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 Stromflußüberwachungsein direction is connected, wherein the controller for performing the above-described method for driving a thyristor or triac is designed 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.

The above and other 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:

Figure 1 is a circuit diagram of a triac circuit with a control circuit according to the vorlie invention.

Fig. 2 is a current-time diagram for explaining the principle of operation of a control circuit according to the present invention;

3 shows a flowchart of a method for driving a triac according to an exemplary embodiment of the present invention;

FIG. 4 shows a flow chart of an adjustment phase for adjusting the ignition pulse duration for the method of FIG. 3; and FIG. 5 shows a flowchart of an adjustment phase for adjusting the hold pulse duration for the method from FIG. 3.

With reference to FIGS. 1 and 2, the structure and mode of operation of a triac circuit with a control circuit according to the invention are first explained by way of example.

The triac circuit contains a series connection of a triac 1 and a load 2, which is connected to an AC voltage source 3. The triac 1 is controlled by a control circuit 4. The control circuit 4 has a pulse generator 6 for generating gate current pulses IP1, IP2 with a gate current value IG which are applied to the gate electrode of the triac 1. The pulse generator 6 is operated by a controller 5. In order to recognize the correct times of the gate current pulses IP1, IP2, a phase synchronization 7 with the AC voltage source 3 is provided. The controller 5 is also connected to a memory 8 for storing various parameter values, a timer 9 and a current flow monitoring device for monitoring a current flow through the triac 1. In this exemplary embodiment, the current flow monitoring device has a voltage detection device 10 for detecting a gate voltage UG between the gate electrode and the cathode of the triac 1.

When switched off or blocked, the triac 1 has a high resistance 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). There is no gate current (IG = 0) at the gate electrode of triac 1. In this operating state, no voltage drops across the load 2 (UR = 0) and the AC voltage UN drops across the triac 1 (UT = UN). Due to the lack of current flow through the triac, the gate voltage UG = 0.

After a voltage zero crossing tNO, the triac 1 is ignited with a gate current pulse IP1 with a gate current value IG. In the ignited or switched-on state, the triac 1 has a low resistance and corresponds to a closed switch which enables a current IR through the triac 1 and through the load 2 in accordance with the AC voltage UN. In this operating state, the alternating voltage UN drops approximately across the load 2 (UR «UN) and no voltage drops across the triac 1 (UT = 0). Due to the current flow IR through the triac 1, a gate voltage UG can be detected which exceeds a limit value UGM.

The ignition pulse duration TL of the gate current pulse IP1 is selected such that the current IR through the triac after the end of the gate current pulse IP1 exceeds a latching current value IL, so that the triac 1 remains switched on even without a gate current IG. Should be prevented that the triac 1 turns off when the current IR through the triac 1 falls below a holding current value IH, then before the next voltage zero crossing tNO a further gate current pulse IP2 is applied to the gate electrode of the triac 1 by the Keep triac 1 on. The holding pulse duration TH of the further gate current mimpulses IP2 is chosen so that the current IR through the triac at the beginning of the further gate current pulse IP2 is still above the holding current value IH. If the phase duration of a voltage half-wave is designated TP, the further gate current pulse IP2 is started at a time tnO + TP-TH.

This basic functioning of a triac and its control are known to the person skilled in the art. There is therefore no need for a more detailed explanation.

3 to 5, an exemplary embodiment of an inventive control of the triac 1 will now be explained in more detail.

As illustrated in FIG. 3 or in the partial figures 3A and 3B, the method according to the invention for actuating the triac 1 contains an adjustment phase P10 and an operating phase P20, the operating phase comprising an ignition phase P22, a monitoring phase P24 and a holding phase P26 can be broken down.

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

As shown by way of example in FIG. 4, the setting of the ignition pulse duration TL in the setting phase P10 by the control circuit 4 comprises the steps S120 to S126.

In the first step S120, the ignition pulse duration TL is first set to a low initial value TL0. Then it waits for voltage zero crossing tNO (step S121). When the voltage zero crossing tNO (“J” in S121) is reached, in the next step S122 a gate current pulse IP1 with a gate current value IG and the ignition pulse duration TL are applied to the gate electrode of the triac 1 in order to switch on the triac 1. After the ignition pulse duration TL has elapsed, the gate current pulse IP1 is ended in step S123 (IG = 0). The controller 5 then uses the voltage detection device 10 to check whether the gate voltage UG has reached a predetermined limit value UGM in order to conclude from this that there is or does not exist a current flow through the triac 1. If after the end of the gate current pulse IP1 there is a current flow through the triac 1 (“J” in S124), the ignition pulse duration TL is long enough for the current IR through the triac to exceed the latching current value IL and for the triac 1 to be switched on even without a gate current IG remains. In this case, the current value of the ignition pulse duration TL is stored in the memory 8 of the control circuit 4 (step S125) in order to be used for the gate current pulse IP1 in the ignition phase P22 of the operating phase P20.

If, on the other hand, there is no current flow through triac 1 (“N” in S124) after the end of the gate current pulse IP1, the ignition pulse duration TL is too short, so that current IR through the triac does not reach the latching current value IL and the triac 1 is without gate current IG turns off. In this case, the current value of the ignition pulse duration TL is increased by a pulse duration difference dt in step S126 and the process from step S122 (or alternatively from step S121) is repeated until the increased ignition pulse duration TL is sufficient (“J” in S124).

As shown by way of example in FIG. 5, the setting of the holding pulse duration TH in the setting phase P10 by the control circuit 4 comprises the steps S140 to S144.

In the first step S140, the holding pulse duration TH is first set to an initial value TH0. The initial value can be the determined ignition pulse duration TL, for example. It is then checked in step S141 whether at the beginning of the further gate current pulse IP2, i.e. at the time tNO + TP - TH current IR still flows through the triac 1. If this is not the case (“N” in S141), the holding pulse duration TH must be increased in step S142, so that the further gate current pulse IP2 begins earlier. The increased hold pulse duration TH is then stored in the memory 8 (step S143) in order to be used for the further gate current pulse IP2 in the hold phase P26 of the operating phase P20. If, on the other hand, there is still a current flow IR through the triac 1 (“J” in S141) at the beginning of the further gate current pulse IP2, the holding pulse duration TH is shortened by dT in step S144 and the method goes back to step S141.

In an alternative embodiment of the invention, the setting of the holding pulse duration TH by the control circuit 4 can also be dispensed with. In this case the holding pulse duration TH is set, for example, to the value of the determined ignition pulse duration TL, so that the further gate current pulse IP2 is certainly long enough for the triac to remain switched on before the next voltage zero crossing tNO.

After completion of the described setting phase P10, the control circuit 4 goes into the operating phase P20, in which the triac 1 is controlled according to the settings and the proper and energy-saving functioning of the triac 1 is monitored.

The ignition phase P22 of the operating phase P20 begins at a voltage zero crossing tNO (step S220). At the voltage zero crossing tNO, the gate current pulse IP1 is started (step S222) and maintained for the determined ignition pulse duration TL (step S224).

After the ignition pulse duration TL (“J” in S224), the gate current IG is switched off (step S240) and the monitoring phase P24 begins. In step S241, the voltage detection device 10 of the control circuit 4 detects the gate voltage UG. In step S242, the detected gate voltage UG is compared with a predetermined limit value UGM. If the gate voltage UG reaches the limit value UGM (“J” in S242), the controller 5 detects a current flow IR through the triac 1. This means that the ignition pulse duration TL is sufficient to ignite the triac 1.

If, however, the gate voltage UG does not reach the limit value UGM (“N” in S242), the controller 5 knows that there is no current flow IR through the triac 1. This means that the ignition pulse duration TL was too short for the ignition of the triac 1 and the triac 1 switches off after the gate current pulse IP1 has ended. In step S243, the gate current pulse IP1 is therefore immediately activated again in order to switch on the triac 1. The monitoring phase then continues with step S240. Optionally, after reactivating the gate current pulse IP1 in step S243, the ignition pulse duration TL can also be adjusted. This adjustment takes place, for example, analogously to the adjustment phase according to FIG. 4.

If the triac 1 remains switched on after the end of the gate current pulse IP1 with the ignition pulse duration TL or the extended gate current pulse IP1, then until the point in time tNO + TP - TH of the planned further gate current pulse IP2. As long as this point in time has not yet been reached (“N” in S245), the gate voltage UG is detected by the voltage detection device 10 of the control circuit 4 (step S246). In step S247, the detected gate voltage UG is compared with a predetermined limit value UGM. If the gate voltage UG reaches the limit value UGM (“J” in S247), the controller 5 detects a current flow IR through the triac 1. This means that the triac 1 is still switched on and the further gate current pulse IP2 has not yet started correctly had to become. Monitoring of the current flow then continues.

If, however, the gate voltage UG does not reach the limit value UGM (“N” in S247), the controller 5 knows that the current flow IR through the triac 1 no longer exists. This means that the holding pulse duration TH is too short and the triac 1 has already switched off before the start of the further gate current pulse IP2. In step S248, a gate current IG is therefore immediately applied to the triac 1 in order to switch the triac 1 on again. Optionally, after the gate current IG has been activated in step S248, the holding pulse duration TH can also be adapted. This adjustment takes place, for example, analogously to the setting phase according to FIG. 5.

If, on the other hand, the triac 1 remains switched on until the planned start time of the further gate current pulse IP2 (“J” in S247), the holding phase P26 then begins. In step S260, the further gate current pulse IP2 is then started in order to maintain the current flow IR through the triac 1, even if the current IR falls below the holding current value ICH. The further gate current pulse IP2 is then retained until the next voltage zero crossing tNO + TP (step S261).

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

While the invention has been explained above with reference to FIGS. 1 to 5 using the example of a triac control without phase angle, 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 is only started after a certain phase angle W after the voltage zero crossing tNO, as shown in FIG. 2 indicated. Likewise, with a phase gating control, the further gate current pulse IP2 can already be ended a certain phase angle before the voltage zero crossing tNO. In the case of such a phase gating control, in the setting phase P10 the control circuit 4 determines different ignition pulse durations TL and, if appropriate, also different holding pulse durations TH for different phase angles W. In the operating phase P20, the controller 5 then selects the determined pulse durations TL, TH for the respectively desired phase angle W in order to carry out the operating phase P20 with these pulse durations TL, TH.

While the invention has been explained above with reference to FIGS. 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 NUMBER LIST

1 triac

2 load

3 AC voltage source

4 control circuit

5 control

6 pulse generator

7 phase synchronization

8 memories

9 timers

10 Voltage detection device I current

IG gate current (worth)

IH holding current value

IL lock 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

THO initial value holding pulse duration

TL ignition pulse duration

TLO initial value of ignition pulse duration

tNO time zero voltage crossing

TP phase duration voltage half-wave

UG gate voltage

UGM gate voltage limit

UN AC voltage

UR voltage drop over load

UT voltage drop across triac

W phase angle

Claims

PATENT CLAIMS

Method for driving a thyristor or triac (1), the thyristor or triac (1) being ignited by a control circuit (4) after a zero voltage crossing (tNO) of an alternating 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 (I P1) for igniting the thyristor or triacs (1), so that the current (IR) through the thyristor or triac (1) after reached at the end of the gate current pulse (IP1) 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 voltage zero crossing (tNO) of the AC voltage source (3) with a gate current pulse (IP1) with the determined ignition pulse duration (TL) (S222, S224 ) and then a current flow through the thyristor or triac (1) is monitored (S241, S242, S246, S247).

The method of claim 1, wherein

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).

The method of claim 1 or 2, wherein

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) also a hold pulse duration (TH) for a further gate current pulse (IP2) before a voltage zero crossing (tNO) of the AC voltage source (3), so that the current (IR) through 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 voltage zero crossing (tNO) of the AC voltage source (3) controls the thyristor or triac (1) with a further gate current pulse (IP2) with the determined holding pulse duration (TH) (S260, S262) .

The method of claim 4, wherein

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 (I P2) 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 (tNO) of the AC voltage source (3) by means of a gate current pulse (IP1);

the control circuit (4) in the setting phase (P10) determines the ignition pulse duration (TL) as a function of the predetermined phase angle (W); 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 (tNO) of the AC voltage source (3) with a gate current pulse (IP1) with the determined ignition pulse duration (TL) activated (S222, S224).

The method of claim 6, wherein

the control circuit (4) in the setting phase (P10) determines several different ignition pulse durations (TL) for different phase angles (W).

Method according to one of the preceding claims, in which

the control circuit (4) repeats the setting phase (P10) regularly.

Control circuit (4) for controlling 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 of a method for driving a thyristor or triac (1) according to one of Claims 1 to 8.

10. A control circuit according to claim 9, wherein

the current flow monitoring device comprises 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).

1 1. Control circuit according to claim 9 or 10, 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 holding pulse duration (TH) and the adjusted holding pulse duration (TH).