EP1332647A1

EP1332647A1 - Circuit device for reducing or increasing an alternating voltage in an approximately sinusoidal manner

Info

Publication number: EP1332647A1
Application number: EP01994045A
Authority: EP
Inventors: Günther Pritz; Werner Hanke
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-09
Filing date: 2001-11-09
Publication date: 2003-08-06
Anticipated expiration: 2021-11-09
Also published as: WO2002039789A1; DE10055576A1; ATE290763T1; AU2002217015A1; DE50105558D1; EP1332647B1

Abstract

A circuit device for reducing or increasing an alternating voltage in an approximately sinusoidal manner is comprised of an autotransformer, to which the alternating voltage is applied and which has at least one tap, whereby one end of the winding of the autotransformer is connected to the output of the circuit device via a first switch, whereas the tap is connected to the output of the circuit device via a second switch. When opening or closing the first switch, the second switch is alternately closed or opened. The first and the second electronic switch are, for each half-wave of the alternating voltage, provided in the form of transistor switches each having a diode that is connected in parallel. The transistor switches of the first electronic switch, which can be alternately switched through by the half-phases of the alternating voltage, can be controlled by a microprocessor. The microprocessor supplies, according to a phase zero recognition circuit, a firing angle signal for a phase section control and/or phase-fired control of the transistor switch of the first electronic switch. When the first electronic switch is in an non-conducting state, the transistor switch of the second electronic switch is alternately switched by the half-waves of the alternating voltage into the conducting or non-conducting state.

Description

CIRCUIT DEVICE FOR APPROXIMATELY SINUS-LOWERING REDUCTION OR Raising an AC VOLTAGE

The invention relates to a circuit device for approximately sinusoidal lowering or raising of an alternating voltage, consisting of an autotransformer with at least one tap, which is acted upon by the alternating voltage, the one end of the winding of the autotransformer being connected to the output (L ¹ ) via a first switch (ESI) Switching device and the tap is connected to the output (L ¹ ) of the switching device via a second switch (ES2) and the second switch is alternately closed or opened when the first switch is opened or closed.

When controlling fluorescent tube systems or high-pressure gas tubes, it is desirable to trigger the electron flow or ion flow that begins after the phase change with as high a voltage as possible, with only a low voltage being necessary for maintaining this electron or ion flow for the rest of the phase. ie the lamps require a higher inrush current than operating current. If a starting voltage of 230 V is assumed as the inrush current, the operating current can be maintained at much lower voltages, the level of the operating current depending on other switching components and in particular the transformer, so that a voltage drop of the order of about 2/5 to 1/3 of the output voltage is in the range of appropriate sizes.

From DE 195 41 341 C2 and DE 195 43 249 AI autotransformers for uninterrupted voltage control are known for such control systems, the voltage control being carried out with the aid of many taps that are able to control a narrow voltage range with the help of contactors. The contactors must be switched over at the same time, if possible, in order to avoid brief twitches of the light, but care must be taken to ensure that the contactors are not closed at the same time, otherwise a short circuit will occur. Because such short-circuit currents Chokes that limit the short-circuit current for a short time can hardly be avoided.

A control transformer with taps is also described in the magazine "Control engineering", January 1964, pages 84 to 86, which is switched over to the desired output voltages without interruption. The individual switching combinations are carried out with the aid of semiconductors, which, however, lead to problems since the load current flows over all switching elements and therefore the semiconductor elements must be correspondingly large and complex.

The invention has for its object to provide a switching device that allows the power control of fluorescent tube systems or high pressure gas tubes with electronic switches that are relatively simple and inexpensive despite the power requirement and the known power switch from a higher inrush current to a lower operating current in allows every half phase of the AC voltage without overload. The circuit device should also offer the possibility, by appropriate modification, of generating a constant voltage above the input voltage. The circuit device should be usable in both compensated and non-compensated systems.

Starting from the switching device mentioned at the outset, this object is achieved according to the invention in that the two switches (ESI, ES2) can be switched on and off alternately electronically with the frequency of the alternating voltage, the first electronic switch (ESI) being in the form of a phase gating and / or There are phase switch control transistor switches, which can be controlled alternately depending on the phase zero crossing, and wherein the second electronic switch (ES2) is also built up alternately depending on the phase conductive transistor switches, of which one transistor switch in the positive phase and the second transistor switch is conductive in the negative phase of the AC voltage when the first electronic switch (ESI) is not conductive; that the transistor switches of the first and second electronic switches (ESI; ES2) comprise at least one field effect transistor (MOS-FET or IGBT) with a parallel diode for each half-wave of the AC voltage; that the transistor switch of the first electronic switch (ESI), which can be switched through alternately by the half-phases of the AC voltage, is operated by a microprocessor are controllable which, depending on a phase zero detection circuit, supplies an ignition angle signal (ZW) for the phase control and / or phase control of the transistor switches; and that the transistor switches of the second electronic switch (ES2) can be switched to the conductive or non-conductive state via a control circuit semi-periodically selectively in the case of a non-conductive first electronic switch (ESI).

Electronic switches are already known from DE 197 31 700 AI and DE 198 31 603 AI. However, it has been found that these known electronic switches cannot readily be used for circuit devices which are to be used both in compensated systems and in non-compensated systems at AC voltage frequencies of 50 Hertz or 60 Hertz.

Under these conditions, it is necessary for the control of the electronic switches that they are controlled exactly in phase. Therefore, the invention provides that the phase-shifted phase zero-crossing signal of the alternating voltage tapped by a low-pass filter acts as a trigger signal (Tr) on a monostable multivibrator, whose RC element is tuned to the alternating voltage frequency at the end of the metastable state and is in phase with the next phase zero crossing Output signal (Q) delivers.

This trigger signal and the in-phase output signal of the monostable multivibrator are used to control a microprocessor, which determines the AC voltage frequency by counting and calculates the desired ignition angle signal for the first electronic switch.

The invention further provides that the microprocessor delivers a changeover signal when the frequency of the AC voltage changes, with which it adapts the time constant of the RC element to the changed frequency.

According to a further embodiment of the invention, it is provided that the ignition angle signal for actuating the transistor switch of the first electronic switch (ESI) as a function of the ignition angle can be applied to the transistor switch via an optocoupler on the input side and a Schmitt trigger circuit, and that the transistor switch has this first electronic switch (ESI) switch on or off in accordance with the desired phase control and / or phase control. For the control of the second electronic switch, it is also provided that the ignition angle signal for triggering the transistor switch of the second electronic switch (ES2) as a function of the ignition angle can be applied to these transistor switches via a flip-flop and, if appropriate, a further optocoupler, and these alternately when the first electronic switch is switched off (ESI) leads.

The invention further provides that the firing angle-dependent control of the first and second electronic switches can be suppressed if a current transformer (SW) detects an overcurrent at the output (L ¹ ) of the circuit device.

This overcurrent-dependent voltage at the current transformer (SW) is comparable to a reference voltage at a resistor, a voltage exceeding the reference voltage on the one hand suppressing the transmission of the ignition angle signal (ZW) to the first electronic switch (ESI) and on the other hand resetting the flip-flop in order to use the Optocoupler to control the second electronic switch (ES2) in the non-conductive state.

This circuit device designed according to the invention advantageously fulfills all requirements in compensated and non-compensated networks of lighting systems with fluorescent tubes or high-pressure gas tubes, the electronic switches being constructed in a very stable manner with relatively inexpensive electronic elements.

The advantages and features of the invention also result from the following description of exemplary embodiments in conjunction with the claims and the drawing. Show it

1 shows a basic circuit diagram of the circuit arrangement according to the invention for sinusoidally lowering an AC voltage;

2 shows a basic circuit diagram of a further embodiment of the invention for sinusoidally raising the AC voltage;

3 shows a basic circuit diagram of the first electronic switch according to FIGS. 1 and 2;

4 shows a basic circuit diagram of the second electronic switch according to FIGS. 1 and 2; Fig. 5 is a schematic diagram for the phase zero detection and the adjustment of the

Firing angle signal at different network frequencies;

6 shows a basic circuit diagram for the firing angle-dependent control of the first and second electronic switches according to FIGS. 1 and 2.

In the following description, the same reference numerals are used for the same parts.

The basic circuits shown in FIGS. 1 and 2 consist of an autotransformer 10, the upper winding end of which is connected to the phase voltage L and the lower winding end of which is connected to the neutral conductor N. The upper winding end is also located above a first electronic switch ESI at the output L ', a tap 11 is also connected to the output L' via a second electronic switch ES2.

The two electronic switches ESI and ES2 are coupled or synchronized with one another in such a way that they have a two-way switch function. It is important that the two electronic switches are not simultaneously conductive to avoid a short circuit.

Under these conditions, it follows that when the electronic switch ESI is closed and the electronic switch ES2 is open, the phase voltage L is present at the output L ¹ , whereas when the electronic switch ESI is open and the electronic switch ES2 is closed, the voltage corresponding to the turns ratio of the two winding sections is present at the output L ¹ ,

For the phase-accurate switching of the electronic switches ESI and ES2, it is necessary to carry out a phase zero detection with the aid of the circuit 15 in order to generate an ignition angle signal ZW and to control the electronic switches ESI and ES2 with the signals required for the half-wave selective switching.

Depending on the output current, a current transformer SW supplies a supply voltage via the electronic switch ES2 for triggering the two electronic switches ESI and ES2 as a function of the ignition angle, as will be explained in more detail below with reference to FIG. 6. The circuit for phase zero detection and possibly for frequency switching according to FIG. 5 is used to generate the ignition angle signal ZW. A voltage supply 20 supplies an alternating current signal with 50 or 60 Hertz to a low-pass filter 22, which is constructed symmetrically from resistors 23 and capacitors 24. This low-pass filter 22 also has the purpose of filtering out the tone frequencies modeled on the mains voltage for switching operations. The output signal of the low-pass filter controls two transistors 26 connected in series with one another, which provide a pulse signal sequence for the transistor 27 corresponding to the AC voltage on the output side. This transistor 27 is switched to the conductive state by the positive half-wave pulse and transmits a positive trigger signal to a monostable multivibrator 28 on the output side 31 counts the period or frequency of the AC signal and recognizes the correct phase zero of the AC signal based on a delayed output signal of the monostable multivibrator.

By the trigger signal, the monostable multivibrator 28 is switched from its stable state to the metastable state, in which it remains until the capacitor 33 of the connected RC element with the resistors 34, 35 is charged to the threshold voltage at which the switches the monostable multivibrator from the metastable state back to the stable state. By setting the RC element, the switching delay of the monostable multivibrator is set to the AC voltage frequency with the aid of the adjustable resistor 35, so that a time delay occurs when switching back from the metastable state to the stable state and the output signal Q exactly to the phase zero crossing over the line 31 for the microprocessor 30 is available.

If the microprocessor 30 determines that the counted period over the two lines 29 and 31 is different, a switching signal UMS is applied to a transistor 36 so that it becomes conductive and the resistors 37, 38 switch in parallel with the resistors 34, 35. These resistors are selected such that the delay in the monostable multivibrator 28 is adapted to the respective frequency when the AC frequency is switched from 50 Hz to 60 Hz. The microprocessor 30 now calculates the ignition angle signal ZW according to the desired phase angle or the desired phase angle on the basis of the output signal Q, which characterizes the correct phase zero position, via the line 31.

A basic circuit diagram of the first electronic switch ESI is shown in FIG. 3. When the ignition angle signal ZW supplied by the microprocessor 30 is present at the electronic switch, the AC voltage supplied by the voltage supply 20 is applied via an optocoupler 41 to a Schmitt trigger circuit 42 which converts the sinusoidal voltage into a square-wave AC voltage. To the two output lines for the positive half-wave and the negative half-wave of the square-wave AC voltage are connected via the coupling resistors 43 and 44, MOS-FETs 46 and 47, to which a diode 48 and 49 is connected in parallel, which is not must act discrete diodes, but those that result from the semiconductor structure inside the semiconductor.

The optocoupler 41 is preferably used to provide a potential separation with respect to the various necessary power supplies.

When the firing angle signal ZW supplied by the microprocessor 30 is present and thus the conductive optocoupler 41 supplies the AC voltage to the Schmitt trigger circuit 42, the positive square-wave signal applied via the decoupling resistors 43 switches the transistor switches 46 into the conductive state, the diodes 48 being blocked. At the same time, the diodes 49 in the transistor switch 47 are conductive, thus establishing the conductive connection between the phase voltage L and the output L '. The same applies to the negative pulse of the square-wave alternating voltage, which switches the transistor switches 47 into the conductive state via the decoupling resistors 44, so that when the diodes 49 are blocked, the conductive connection from the phase voltage L to the output L 'takes place via the transistor switches 47 and the diodes 48.

As soon as the ignition angle signal ZW is no longer present, the connection between the phase voltage L and the output L 'is interrupted.

The structure of the second electronic switch ES2 is shown in FIG. 4. Then an alternating voltage is applied from the voltage supply 20 via an optocoupler 51, which also serves for electrical isolation, which is used for the positive Half wave makes the transistor in the optocoupler conductive and blocks the transistor 53 in the downstream network. The resulting increase in collector voltage is applied to the base of transistor 55 through resistor 54, which thereby receives a positive bias and becomes conductive.

The resulting potential at the collector of transistor 55 causes transistor 57 to be blocked while at the same time transistor 56, which has the same base bias, becomes conductive and ensures that a positive voltage is present on line Ghl for the positive half-wave, whereas ground potential for negative half-waves is effective on this line. Correspondingly, the transistor 53, which is blocked by the positive half-wave via the optocoupler 51, drives the transistors 58 and 59 with its collector potential and causes the transistor 58 to become conductive and the transistor 59 to block, thus providing ground potential and for the positive half-wave on the output line Gh2 a positive potential is effective for the negative half-wave.

Via the decoupling resistors 60 and 61, these potentials control the downstream transistor switches 62 and 63, to each of which a diode 64 or 65 is connected in parallel, which may also be diodes integrated in the semiconductors.

This combination of circuits results in that a positive half-wave of the alternating voltage effective between the tap 11 and the output L 'is transmitted via the transistor switches 63 and the diodes 64 to the output L ¹ , whereas for the negative half-wave of the alternating voltage the tap 11 is transmitted via the transistor switches 62 and the diodes 65 is connected to the output L ¹ .

In order to open the electronic switch ES2 for the time of the ignition angle signal ZW from the microprocessor 30, i.e. While the electronic switch ESI is closed, the connections A and B are short-circuited according to FIG. 4 by the conductive optocoupler 75 and are thus effective at the ground potential on the lines Ghl and Gh2.

This bridging of the connections A and B takes place with the aid of the ignition angle-dependent control of the electronic switches ESI and ES2 according to FIG. 6. For this purpose, the ignition angle signal ZW is applied to the circuit 16 for controlling the electronic switches ESI and ES2. This circuit comprises two inverting Schmitt triggers 70 and 71, which are connected in series and transmit the ignition angle signal directly to the electronic switch ESI. The circuit also includes a flip-flop 72, which is set when the firing angle signal is applied from the output signal of the Schmitt trigger 70 via the line 73 such that the light-emitting diode in the optocoupler 75 lights up and the transistor on the output side short-circuits the terminals A and B. This opens the electronic switch ES2.

In order to keep the connection terminals A and B in the open state when the ignition angle signal is not present, it is necessary that the diode in the optocoupler 75 is switched off. This is done by switching the flip-flop as a result of actuation via line 76. For this purpose, a signal is derived from the current flowing through output L ¹ via a current converter SW, which signal is used to measure the output current. The low voltage supplied by the current transformer SW is first amplified with the aid of operational amplifiers 78 and 79 with respect to the negative half-wave and the positive half-wave, and is fed to two further operational amplifiers 80 and 81 in order to compare the voltage from the current transformer with a reference voltage at the resistor 82. If the amplified voltage is greater than the reference voltage, the two operational amplifiers 80 and 81 are switched through to apply a maximum or minimum supply voltage to the capacitor 83, whereupon the output voltage at the inverting Schmitt trigger 84 goes to ground. On the one hand, the flip-flop 71 is set in such a way that the light-emitting diode in the optocoupler 75 lights up and controls the internal transistor into the conductive state, ie short-circuits the connection terminals A and B. As already mentioned, this short circuit causes the electronic switch ES2 not to become conductive.

The ground signal at the output of the inverting Schmittt trigger 84 also serves as a basic control via the resistor 86 on the transistor 85, which thus becomes conductive and pulls the input of the inverting Schmitt trigger 71 against positive potential. This results in ground potential at its output, which causes the electronic switch ESI to be switched to the non-conductive state via the optocoupler 41 according to FIG. 3.

This structure protects against overcurrents, on the one hand, but in normal operation, if no overcurrents occur, transistor 85 is blocked and the output signal of Schmitt trigger 70 is used as an inverted ignition angle signal Output the inverting Schmitt trigger 71 in phase to the electronic switch ESI.

If no overvoltage is effective, in the absence of an ignition angle signal ZW, the signal effective at the output of the inverting Schmitt trigger 70 is applied to the diode 88 via the also inverting Schmitt trigger 87, as a result of which the diode 88 becomes conductive and discharges the capacitor 83.

The measures of the invention provide a circuit device for the approximately sinusoidal lowering or raising of an alternating voltage, which in the operating state is extremely stable and can also be used in a variety of ways for different network frequencies, even if tone frequencies are modulated onto the network voltage for switching processes, which cause phase shifts. The stability of the circuit is also favored in that overcurrent-sensitive semiconductor elements are not exposed to excessive load currents due to the integrated overcurrent shutdown.

Claims

claims

1. Circuit device for approximately sinusoidal lowering

AC voltage, consisting of an autotransformer with at least one tap, the one end of the winding of the autotransformer via a first switch (ESI) with the output (L ¹ ) of the switching device and the tap via a second switch (ES2) is connected to the output (L ¹ ) of the switching device and the second switch is alternately closed or opened when the first switch is opened or closed,

characterized in that the two switches (ESI, ES2) can be switched on and off alternately electronically with the frequency of the alternating voltage, the first electronic switch (ESI) consisting of transistor switches (46, 47) operating as phase control and / or phase control, which can be controlled alternately depending on the phase zero crossing, and wherein the second electronic switch (ES2) is likewise constructed from transistor switches (62, 63) that conduct alternately depending on the phase, of which one transistor switch (46; 62) is in the positive phase or the second transistor switch (49; 63) is conductive in the negative phase of the AC voltage when the first electronic switch (ESI) is not conductive; that the transistor switches (46, 47; 62, 63) of the first and second electronic switches (ESI; ES2) have at least one field effect transistor (MOS-FET or IGBT) with a parallel diode (48, 49; 64,) for each half-wave of the AC voltage. 65) include; that the transistor switches (46, 47) of the first electronic switch (ESI) which can be switched through alternately by the half-phases of the AC voltage can be controlled by a microprocessor (μP) which is dependent on a phase a zero detection circuit supplies an ignition angle signal (ZW) for the phase control and / or phase control of the transistor switches (46, 47); and that the transistor switches (62, 63) of the second electronic switch (ES2) can be switched to the conductive or non-conductive state via a control circuit (16) semi-periodically selectively when the first electronic switch (ESI) is non-conductive.

2. Circuit arrangement according to claim 1,

characterized in that the phase-shifted zero-crossing signal of the AC voltage tapped by a low-pass filter (22) acts as a trigger signal (Tr) on a monostable multivibrator (28) whose RC element (33,34,35; 33,37) is tuned to the AC voltage frequency , 38) at the end of the metastable state supplies an output signal (Q) which is in phase with the next phase zero crossing.

3. Circuit arrangement according to claim 2,

characterized,

that the trigger signal (Tr) and the in-phase output signal (Q) on the

Microprocessor (μP) acts, which determines the AC voltage frequency by counting and calculates the desired ignition angle signal (ZW) for the first electronic switch (ESI).

4. Circuit arrangement according to claim 3,

characterized,

that the microprocessor (μP) delivers a changeover signal (UMS) when the frequency of the AC voltage changes, with which it adapts the time constant of the RC element (33, 34, 35; 33, 37, 38) to the changed frequency.

5. Circuit arrangement according to claims 1 to 4,

characterized in that the ignition angle signal (ZW) can be applied to the transistor switches (46, 47) via an input-side optocoupler (41) and a Schmitt trigger circuit (42) for actuating the transistor switches (46, 47) of the first electronic switch (ESI) as a function of the ignition angle and that the transistor switches (46, 47) switch this first electronic switch (ESI) on or off in accordance with the desired phase control and / or phase control.

6. Circuit arrangement according to claims 1 to 4,

characterized in that the ignition angle signal (ZW) for triggering the transistor switches (62, 63) of the second electronic switch (ES2) as a function of the ignition angle via a flip-flop (72) and possibly a further optocoupler (72) to these transistor switches (62, 63 ) can be applied and alternately makes it conductive when the first electronic switch (ESI) is switched off.

7. Circuit arrangement according to claims 5 and 6,

characterized in that the firing angle-dependent control of the first and second electronic switches (46, 47; 62, 63) can be suppressed if a current transformer (SW) detects an overcurrent at the output (L ¹ ) of the circuit device.

8. Circuit arrangement according to claim 7,

characterized,

that the overcurrent-dependent voltage at the current transformer (SW) is comparable to a reference voltage at a resistor (82); and that a voltage exceeding the reference voltage on the one hand suppresses the transmission of the ignition angle signal (ZW) to the first electronic switch (ESI) and on the other hand resets the flip-flop (72) in order to use the optocoupler (75) to switch the second electronic switch (ES2) into the controls non-conductive state.