EP2421334A2 - Switch system and method for operating a gas discharge lamp - Google Patents

Abstract

The arrangement has a switch connected parallel to a gas discharge lamp, and an inductor serially connected to the switch. An igniter e.g. switchable superimposed-pulse igniter, is controlled by a control device i.e. microcontroller, and utilizes a capacitor as a takeover capacitor in an upstream direct current (DC) supply unit. A detection unit detects zero-crossing voltage, and is connected with a comparator input and an input/output (I/O) output of the control unit. A reference part is attached to a negative input of a differential analog-to-digital (A/D) converter at the control unit.

Description

Technical area

The invention relates to a circuit arrangement and a method for operating a gas discharge lamp, in particular a high-pressure discharge lamp or low-pressure discharge lamp, which is operated on an inductive ballast and is connected in parallel to the lamp and serves to ignite the lamp and operate at a certain power.

background

Retro-fit lamps replace less efficient lamps, such as high-pressure mercury vapor lamps, with a luminous efficacy of about 50 lm / W. Retro-fit lamps contain more efficient lamps, such as metal halide high-pressure lamps or high-pressure sodium vapor lamps with luminous efficiencies of 100 lm / W and more. The Retro-Fit lamp uses the magnetic ballast required to operate high pressure mercury vapor lamps. In order to reduce the power consumption of the higher-efficiency lamp at the same luminous flux, it has been proposed ( Fig. 1 ) [ WO 2008/104431 A1 ], the average lamp current and thus the lamp power by a switch connected in parallel to the lamp switch, which is closed at the end of each half-wave for a certain time to reduce. This circuit has the characteristic that the harmonic mode according to IEC 61000-3-2 is fulfilled in the reduced-power operation. In Fig. 2 an embodiment of the circuit is shown in which the controllable switch is realized by a symmetrically switching triac. In the drive circuit, the resistors, and the capacitor are selected so that after a certain time after a current zero crossing, for example 7 ms, a sufficient voltage is applied to the capacitor that the Diac X5 breaks through and ignites the triac X4. The ignited triac closes the circuit for a short time and allows the impressed inductor current to flow almost loss-free, while the lamp is short-circuited and does not absorb any power. At the next current zero crossing, the triac X4 opens automatically, whereby in the following half-wave again a current flows through the lamp, this takes up a power and generates light until the triac is closed again. Cons to the in Fig. 2 Circuit arrangements shown are that the network of the resistors, diodes and diac has a strong temperature dependence, whereby it is not possible to set a constant lamp power. Another disadvantage is that the lamp power is dependent on the voltage applied in each case. By this circuit arrangement also can not be provided, the ignition voltage required for the operation of a metal halide high-pressure lamp or high-pressure sodium vapor lamp.

task

It is the object of the present invention to provide a circuit arrangement for a retro-fit lamp, the ignition and a reduced-power operation of the High-pressure discharge lamp, allows for a given performance, especially at higher temperatures on the electronic components.

In addition, various control options, e.g. with a twilight switch, a light sensor and external control via radio signals. In the following embodiments, the function of the circuit according to the invention will be explained.

Presentation of the invention

The circuit arrangement according to the invention is suitable for a high-efficiency discharge lamp of high efficiency of 100 lm / W and more, which is connected to the magnetic ballast of a high-pressure mercury vapor lamp, e.g. a 125W lamp, so that the resulting lamp power is adjusted according to the preset value, e.g. 65 W, regardless of the temperature of the circuit of the mains voltage. Likewise, the circuit must include a device which can ignite the high pressure discharge lamp.

Short description of the drawing (s)

Fig. 1

Simplified circuit for reduced-power operation of a lamp with a switch in parallel with the lamp of the prior art.

Fig. 2

Circuit with drive circuit for reduced-power operation of a lamp according to the prior art.

Fig. 3

Schematic diagram of the circuit.

Fig. 4

First embodiment of the circuit arrangement according to the invention with microcontroller, DC voltage supply, short-circuit switch, ignitor, voltage zero-crossing detector, voltage and current measuring device for operating a high-pressure discharge lamp.

Fig. 5

Ignition and acceptance of the HCI 100 W / WDL lamp at a mains voltage of 200 V.

Fig. 6

Quasipeak spectra and mean value spectra on a network simulation with and without choke L3 and capacitor C14 and the limit values according to DIN EN 55015.

Fig. 7

Device for detecting the voltage zero crossing with a microcontroller according to the prior art.

Fig. 8

Time-dependent voltage signals, for the voltage UD at the inductor, Uzero at the voltage divider, a constant reference voltage Uconst on which one can not trigger, and the reference signal URefS-hift that can be used to trigger the microcontroller.

Fig. 9

Device for detecting the voltage zero crossing with a microcontroller, wherein the reference voltage of the internal comparator with a I / O output is fed back, whereby a switching threshold is formed, whereby the voltage zero crossing at the rising or falling edge of the voltage is detected.

Fig. 10

Second embodiment of the circuit arrangement according to the invention with microcontroller, DC power supply, short-circuit switch, ignitor, voltage zero-crossing detector, voltage and current measuring device for operating a high-pressure discharge lamp.

Preferred embodiment of the invention

In Fig. 3 the schematic diagram for such a circuit is shown. In the classic circuit for high-pressure discharge lamps, the lamp is connected via the magnetic ballast and the ignition unit with the AC voltage source, eg 230 V. For setting the reduced power, a controllable switch is arranged parallel to the lamp, which is controlled by the control unit, for example a microcontroller. With the ignitor, for example, a superimposed ignitor, high voltage pulses are generated, causing the lamp a voltage breakdowns and a takeover. The ignitor is also controlled by the control unit. The DC power supply supplies the control unit with a current. The UI measuring unit provides the control unit with signals that are proportional to the lamp voltage and the lamp current. Likewise, the supplies UI measuring unit, a signal proportional to the lamp voltage with which the voltage zero crossings can be detected very accurately. The control unit has the task of the ignition at the appropriate time when the lamp is not burning to control. The control unit evaluates the lamp power from the voltage and current signal. A certain time after the lamp is taken over, when the lamp power exceeds a certain value, eg 90 W, the control unit activates the controllable switch a few milliseconds before the end of each half-cycle, causing the lamp to short-circuit for a certain time and the lamp power on average is reduced. The detection unit provides a signal for the lamp voltage zero crossing. The control unit evaluates this signal. A certain time after the voltage zero crossing, eg 7 ms, the control unit generates a signal which closes the controllable switch. The control unit evaluates the lamp power from the signals of the U / I measuring unit within one or more periods and changes the delay time Td such that the available lamp power approaches the rated power, eg 65 W, with each period.

example

For a 65 W plug-in EL lamp, a first embodiment of a possible circuit arrangement in FIG Fig. 4 shown. Here, the AC power supply is connected to contacts L and N and the lamp is connected to contacts X5-1 and X5-2. The magnetic ballast is located between the contacts L and X1-1 and is preferably for the operation of a 125 W high pressure mercury vapor lamp.

DC power supply

The control unit, here the microcontroller D1 (Atmel ATiny44), requires a DC voltage source for operation, which can supply a sufficient large current of about 5 mA. In the case of the DC power supply, during the negative voltage half cycle the capacitor C4, e.g. 470 μF, 10V, via diode N1, e.g. 1N4007, the current limiting capacitor C3, e.g. 220 nF, 400 V, and the resistor R1, e.g. 68Ω, 2W, with the zener diode V3 in parallel with the capacitor, e.g. BZV85, the voltage limited to 5.1V. During the positive voltage half-wave, a current flows through C3, R1 and the diode N4, whereby the current flow in both half-waves is about the same, and hereby no DC voltage builds up in the supply voltage. During the ignition phase, a current of up to 10 A flows through this current path for a time of approximately 1 μs. All components, in particular the Zener diode, must be selected so that they can handle this current. The storage capacitor C4 receives the capacitors C6, e.g. 10 μF and C5, e.g. 0.1 μF, connected in parallel to avoid a voltage increase during the ignition phase.

The microcontroller used requires a stable and accurate voltage as a reference for the internal voltage measurement. For this purpose, starting from the DC supply voltage via the resistor R2, the constant voltage source V1 is supplied with a voltage of 2.5 V with with an accuracy of 0.1%, eg ADR5041. This voltage is connected to the reference input of D1.

ignition

The ignition unit is essentially an electronic controlled superposition ignitor as described in EP 0847 681 B1 ] is proposed. In the application example ( Fig. 4 ), the switch is implemented in the superimposed ignition device by a triac T2, eg BTA201W-800E, which is ignited by the microcontroller with voltage pulses. When the triac is closed, the surge capacitor C2, for example 47 nF, is charged, the charging current being limited by the resistor R7, for example 18 kΩ / 2 W. Exceeds the voltage applied to the capacitor C2, the ignition voltage of the voltage-controlled switch, the Sidacs V2, eg ONSemi, MKP3V240, this is closed, bringing the capacitor C2 via the secondary winding of the high voltage transformer L1, eg 6 turns on ferrite core, material EPCOS N87, and the throttle L2, eg 10 μH, is discharged. The current flowing through the secondary winding of the high voltage transformer generates at the output of the primary winding, eg 62 turns, of the transformer a high voltage pulse which leads to a voltage breakdown in the high pressure discharge lamp. After the voltage breakdown, the capacitor C3 is still a voltage, which here represents the transfer voltage for the lamp and maintains the arc current in the high pressure discharge lamp for a short time, and voltage applied to the output of the throttle can take over the arc.

During the ignition phase, the microcontroller generates over many periods until complete acceptance at regular intervals, e.g. Every 100 μs, voltage pulses, which short-circuit triac T2 during the ignition phase. After the ignition phase during stationary lamp operation of the triac T2 is open and thus the ignition unit is not in operation, which has the advantage that in particular the resistor R7 during steady-state operation does not absorb power and Sidac because of the high Wiederzündspitzen not permanently short-circuits.

In Fig. 5 Voltage and current measurements of the ignition unit are shown on an HCI-T 100 W lamp, showing the different phases in the ignition process, the applied mains voltage being 200V.

Circuit for reduced-power operation

For the reduced-power operation of the lamp according to the prior art, a switch, such as a triac, connected in parallel with the lamp ( Fig. 1 ) [ WO 2008/104431 A1 ]. This circuit has the disadvantage that due to the rapid current changes during switching on the triac at the end of the half-wave and because of the relatively low impedance of the choke for higher frequencies, the limits for radio interference according to DIN EN 55015 are exceeded ( Fig. 6 , without choke L3 and capacitor C14). In the circuit according to the invention, in series with the triac T1, a choke L3 is switched, for example with 330 μH, whereby the current increase during the switching on of the triac T1 is reduced. In addition, a capacitor C14, for example 10 nF, is connected in parallel through the parallel to the triac T1 and the inductor L3, whereby the voltage breakdown occurring during switching is somewhat slowed down. This function is also supported by capacitor C3. Overall, this new circuit for power reduction meets the limit values according to DIN EN 55015 ( Fig. 6 )

In the new circuit design, triac T1 is fired by microcontroller D1, resistor R23, e.g. 39 Ω limits the current and the capacitor C12, e.g. 10 nF prevents interference, e.g. is ignited during the ignition phase of the triac T1. In this circuit, the microcontroller D1 needs only a short voltage pulse, e.g. of 20 μs duration to ignite the triac, which advantageously results in that the current to be supplied by the DC power supply remains very small.

Detection of the voltage zero crossing

The microcontroller D1 must turn on the triac T1 at the appropriate time so that the lamp can burn stably without flicker. For this purpose, the microcontroller must detect the time of voltage zero crossing and after a certain time, eg 7 ms generate a signal that ignites the triac T1.

In Fig. 7 For example, a voltage zero crossing detector of the prior art is shown. In this case, the signal is applied via a high-resistance resistor R1 and the capacitor C1 to the positive input of a comparator in the microcontroller MC, wherein the likewise connected voltage parts of R4 and R5 generates a DC voltage component of 2.5 V, for example. The negative input of the comparator is also connected to a voltage divider made up of R2 and R3, which generates a reference voltage of 2.5 V as well. When zero voltage passes from the neutral input, the signal at the plus input changes, causing the comparator to switch, thus generating a voltage zero crossing signal. In the circuit used with the switch in parallel with the lamp, the voltage is short-circuited shorted by the triac before the voltage zero crossing, so that only the forward voltage of the triac 0.5 V is present as a voltage. The existing voltage zero crossing results from a small voltage change of 0.5 V whereby the voltage zero crossing can not be detected cleanly even by small disturbances. In Fig. 8 the upper diagram shows the lamp voltage and the lower diagram shows the signal of the voltage divider UZero, which is connected to the plus input of the comparator. Uconst shows the voltage at the negative input of the comparator. When voltage zero crossing between Uzero and Uconst no clean threshold is present.

Since the voltage zero crossing itself is not clearly detectable, the voltage is proposed shortly after the zero crossing at the rising or falling edge at a threshold of, for example, ± 50 V to detect.

In one possible embodiment, the constant voltage applied to the negative input of the comparator is connected to a resistor R6 to an I / O output of the microcontroller ( Fig. 9 ). The microcontroller knows from the voltage measurement which half-wave is currently available. If the triac T1 is closed in the positive half-cycle, the zero voltage is to be detected at the following drop in voltage at -50 V, which is achieved by the I / O output being switched to low a certain time after the triac T1 has been triggered which reduces the voltage at the minus input of the comparator to about - 3 V (see URefShift in Fig. 8 ) and thus the comparator switches about 190 μs after the voltage zero crossing. If the triac T1 is ignited in the negative half-wave, then the I / O output is switched to high, whereby the reference voltage is increased to approximately -2 V ( Fig. 8 ).

A modified form of this circuit is in the application example ( Fig. 4 ). In this case, via the resistor network of R8, R9, R6, R10, in each case eg 100 kΩ, R11, eg 680 kΩ, a signal with a DC voltage component of approximately - 2.5 V is generated, that via R15, eg 120 kΩ, to the I / O output connected. By switching the I / O output to "high" or "low" at appropriate times, the signal is increased or decreased, whereby the comparator generates a trigger signal when the lamp voltage, the threshold value, eg +/- 50 V below or exceeds.

This circuit produces a delay of approximately 190 μs between the real voltage zero crossing and the detected voltage zero crossing. This value is the same for the positive and negative half wave. It represents a time delay, which is numerically corrected in the microcontroller.

Another possibility to realize different switching thresholds is to select an I / O input from the microcontroller. At a supply voltage of 5 V, the I / O input is set to "high" when a threshold voltage of 3.5 V is exceeded, and the I / O input is set to "low" when the threshold voltage falls below 1.5 V. With this, different thresholds are present, which leads to the generation of a trigger signal at a lamp voltage of +/- 50 V by a suitable dimensioning of the voltage divider. An advantage of this device is that with a change in the supply voltage of the control unit, the switching threshold voltage adapt linearly, whereby a change in the input voltage is partially compensated by the resistor divider.

Power measurement and control to constant power

The control unit evaluates the power from a voltage and current measurement. The microcontroller used in the application example, Atmel ATiny44, has ADC inputs that can measure differential voltages and are capable of amplifying the applied voltage by a factor of 20, so the signal only has to have a small dynamic range of 200 mV.

With the resistor divider made of R16, e.g. 1kΩ and R18, e.g. 47 kΩ and the capacitor C11, e.g. 220 pF, a reference voltage of about - 100 mV is generated, and applied to the negative input of the differential ADC from the microcontroller. With the voltage divider of R21, R22, e.g. 200 kΩ, R25, e.g. 2kΩ and R20, e.g. 100 Ω, a small voltage is generated, which is shifted with R17 and R18 and the capacitor C10 with the same values as the resistance divider, the reference voltage to -100 mV, for example, which is then connected to the positive input of the ADC from the microcontroller.

With the shunt resistor R3, e.g. 0.05 Ω, a voltage is generated proportional to the lamp current. With the network of R4, R5 and C7 having the same values as the reference voltage resistor divider, this voltage signal is shifted to -100 mV and connected to a second positive ADC input of the microcontroller. The difference between the signal for voltage and current to the reference signal is amplified by a factor of 20 and digitized with the internal AD converter. The instantaneous power value is calculated from the product of the digitized voltage and current value. This measurement is repeated at constant time intervals, e.g. every 100 μs. The performance itself is calculated as the average of these instantaneous performances over one or more periods.

The measured power is compared with the nominal power every few periods. Is the measured power greater than the nominal power plus a threshold or less the rated power minus a threshold, then the predetermined Tastpause is increased or decreased. This is repeated until the available power corresponds to the nominal power.

light sensor

In the circuit arrangement for operating a lamp, a light sensor can be integrated which generates a voltage signal that is proportional to the luminance and is measured by the control unit. In order that the light signal is not disturbed by the light of the lamp, the control unit preferably detects the light signal at the times when the lamp is shorted by the triac T1 and the lamp does not generate light. With the aid of the light sensor, the control unit, when it is dark in the vicinity of the lamp, and the light signal falls below a certain threshold turn on the lamp and when it gets bright again and the light signal exceeds another threshold, be turned off again, by closing the triac T1 for a while, eg 1 half-wave, is possible. Of course, the light sensor can also be used to adjust the lamp power so that, depending on the ambient luminance, the lamp power is continuously reduced further, e.g. to 50 W, which can save additional energy.

The object is achieved in that the controllable switch for the ignition device, when the lamp is off and cold by a control unit, such as a microcontroller, is driven, and indeed for so long until the lamp has ignited that the controllable switch parallel to the lamp, after starting the lamp, from a certain lamp power consumption, is controlled by the control unit, in such a way that the Tastpause is slowly increased until reaching the rated power and then continue to operate is that the power is either constant or set to a predeterminable value. To accomplish these tasks, the control unit must receive appropriate measures such as the voltage zero crossing.

temperature resistance

The circuit for operating the lamp should preferably be integrated in a housing that is attached to the lamp. As a result, high temperatures of up to 110 ° C occur in electronics. In order for the circuit to have a sufficiently long life of e.g. 16000 has, only components are selected for the circuit, which have sufficiently small temperature-dependent failure rates. These failure rates are supplied by the manufacturers of electronic components. The total failure rate can be calculated from the sum of the failure rates of the individual components. For the given circuit it was estimated that at 16000 h and 110 ° C the failure rate is less than 2%.

Further applications of the circuit arrangement

The application example of the circuit arrangement is for operation on the magnetic ballast of a 125 W high-pressure mercury vapor lamp in which the lamp power is preferably set to 65 W. When operating on this ballast, it is possible any Lamp power between about 30 W and the maximum power without operating the short-circuit switch, which is a little 110 W to set. In this case, the power is preferably adjusted so that the resulting luminous flux of the lamp operated with this circuit is similar to the luminous flux of the lamp to be replaced. For a 125 W high-pressure mercury vapor lamp, the lamp output would be 65 W for a new light output of 100 lm / W.

This circuit arrangement can also be used for operation on magnetic ballasts for other lamps, for example on a magnetic ballast, which is provided for the operation of a high-pressure 80 W mercury vapor lamp. For this circuit then the lamp power can also be adjusted arbitrarily up to a maximum power without the operation of the short-circuit switch.

Fig. 10 shows a second embodiment of the circuit arrangement according to the Fig. 4 , This embodiment is similar to the embodiment according to the Fig. 4 , therefore, only the differences between the two embodiments will be explained.

In this embodiment, the resistor R7 is looped in the input and charges the capacitor C2. The losses over the power resistor R7 are some 10 mW, which is acceptable. The microcontroller measures the voltage applied and generates an ignition pulse for the triac T2, preferably at the maximum voltage (90 °, 50 Hz) and preferably once per half-wave. A further improvement of the ignition behavior is achieved when several Ignition pulses are generated per half-wave, eg 3 pulses, which have a distance of about 300 microseconds. The triac must be dimensioned so that this pulse currents of 20 A can withstand, which is ensured here by a 4 A triac.

Claims (21)

Circuit arrangement for operating a gas discharge lamp on a magnetic ballast comprising: a switch (T1) parallel to the gas discharge lamp (1, L2), a throttle (L3) in series with the switch (T1), a control unit (D1), an ignition device which can be controlled by means of the control unit (D1). Circuitry according to claim 1, further comprising: a DC power supply, a voltage zero crossing detection unit, and - a device for voltage and current measurement. Circuit arrangement according to claim 1, characterized in that the control unit is a microcontroller. Circuit arrangement according to claim 1, characterized in that the ignition device is a switchable superimposed ignitor. Circuit arrangement according to claim 4, characterized in that the superimposed ignition device has a bipolar switch, in particular a triac. Circuit arrangement according to claim 4 or 5, characterized in that the superimposed ignition device uses as a takeover capacitor a capacitor in an upstream DC voltage supply unit. Circuit arrangement according to claim 1, characterized in that the circuit arrangement for detecting the voltage zero crossing is connected to a comparator input and an I / O output of the control unit. Circuit arrangement according to claim 1, characterized in that the circuit arrangement for detecting the voltage zero crossing is connected to an I / O input of the control unit. Circuit arrangement according to claim 1, characterized in that the circuit arrangement for voltage and current measurement uses a reference divider which is connected to the negative input of the differential AD converter to the control unit. Circuit arrangement according to claim 1, characterized in that the circuit arrangement for voltage and current measurement, the voltage signal from the voltage divider coupled with the voltage shift at the positive input of the differential AD converter to the control unit. Circuit arrangement according to claim 1, characterized in that the current signal for the voltage and current measurement by a shunt resistor is generated, which is shifted and is coupled to the positive input of a differential AD converter to the control unit. Circuit arrangement according to Claim 1, characterized in that the control unit has two parallel AD converters, both of which use the same input for the reference voltage. Circuit arrangement according to claim 1, characterized in that a fuse in the current path is connected in series with the input of the circuit arrangement. Circuit arrangement according to claim 1, characterized in that a series circuit of a backup capacitor and the fuse is connected to the input terminals. Circuit arrangement according to claim 14, characterized in that the backup capacitor serves at the same time as a current limit for the internal power supply of the circuit arrangement. Circuit arrangement according to claim 13, characterized in that the fuse is smaller than the short-circuit current of the magnetic ballast. Circuit arrangement according to claim 16, characterized in that the fuse is 20% smaller than the short-circuit current of the magnetic ballast. Circuit arrangement according to claim 16, characterized in that the fuse 5% to 50% smaller is considered the short circuit current of the magnetic ballast. Circuit arrangement according to claim 16, characterized in that the fuse is 5% to 75% smaller than the short-circuit current of the magnetic ballast. Circuit arrangement according to claim 1, characterized in that the control unit when not burning the gas discharge lamp pulse-shaped repetitive control signals to the ignition unit until by exceeding the lamp power above a certain minimum value, the control unit outputs a signal to the controllable switch in parallel to the lamp, wherein the Tastpause becomes longer from period to period until the measured power is equal to the rated power of the gas discharge lamp. Circuit arrangement according to claim 7 or 8 in conjunction with claim 20, characterized in that after receiving a signal for the voltage zero crossing, the control unit waits a predetermined time, which is determined as the difference of half the period minus the Tastpause and the delayed arrival of the voltage zero crossing signal.

Images