Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
  • H05B41/14—Circuit arrangements
  • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
  • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
  • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
  • H05B41/292—Arrangements for protecting lamps or circuits against abnormal operating conditions
  • H05B41/2928—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the lamp against abnormal operating conditions

Definitions

• the present invention relates to an electronic ballast for driving at least one Lichtquel- Ie, wherein the electronic ballast has an input for connecting a supply voltage, an output for connecting the at least one light source, an oscillator which is designed at its output an oscillator output signal with a to provide the first frequency fosc, wherein the oscillator has a caliber ⁇ input to change the first frequency f osc ; and a microcontroller for providing a drive signal having at least one spectral component at a second frequency f signal for the at least one light source, wherein the microcontroller is coupled to the Oszilla ⁇ gate output and adapted to the second Fre acid sequence f sig nai function of the first frequency f to create osc . It also relates to a method for driving ⁇ at least one light source by means of a corresponding electronic ballast.
• a PWM pulse width modulation
• this problem occurs, for example, in the ignition of a discharge lamp.
• a high voltage is required, which is generated by resonance.
• the resonance frequency or a harmonic frequency of the resonant frequency of a resonant circuit is excited.
• the Fre acid sequence is varied, that is swept.
• the resolution of the frequency steps must be correspondingly high.
• the switching frequency of the lamp current is varied to avoid resonance effects in the lamp.
• the switching frequency is varied in an electronic circuit to make the electromagnetic interference broader bandwidth than at a fixed switching frequency.
• Time-dependent periodic signals are often generated by means of a microcontroller.
• the microcontroller is often clocked by an oscillator with a fixed frequency fosc.
• PWM units By means of internal counters, for example so-called PWM units, periodic signals with an adjustable frequency f signa i or an adjustable on and off time can be generated therefrom and output by the microcontroller.
• the relative frequency resolution of the to be generated periodic signal is smaller, the higher the frequency of a fsignai to be generated signal at a fixed stationary to Ver ⁇ addition oscillator frequency f sc is O.
• the Oszillatorfre acid sequence fosc amounts to 10 MHz, ie a period ⁇ be carrying 100 ns.
• the default already provided in a microcontroller oscillator with the frequency f sc is O ver ⁇ applies to produce by the microcontroller, a signal with the frequency f i signa. Accordingly, when selecting the microcontroller, the integrated oscillator is turned off. To provide signals with a ner high frequency f ai sign at the output of the microcontroller and, moreover, with high resolution, so often dodging well-equipped and therefore expensive microcontroller needed.
• the frequency f sc of the Sig O ⁇ Nals which provides the oscillator available iststel ⁇ len on the Calib ⁇ riereingang an oscillator. This is carried out once and before commissioning of a provided there ⁇ electronic ballast and serves to ensure that different e- lektronische ballasts provide at its output comparable ⁇ bare signals for the light sources to be connected thereto.
• DE 43 01 184 A1 discloses a control device for at least one discharge lamp which has an inverter connected to a DC voltage source for the low-frequency change of the direction of current flow through the discharge lamp and a current regulator which is connected to a current sensor.
• the oscillator for the high frequency can be changed during operation by a control signal in its high frequency, whereby the current flowing through an inductance and the discharge lamp can be switched on and off, and the resulting current can be kept constant by regulating the pulse width.
• the oscillator is a standard VCO (Voltage Controlled Oscillator) in which the frequency output by it can be changed by varying the voltage applied to its control input.
• a VCO has a calibration input, with which the dependence between applied voltage and output frequency can be set.
• the present invention is therefore based on the object switching device an aforementioned electronic pre- or an aforementioned Ver ⁇ drive further develop such a way that using a given oscillator with an oscillator frequency f O sc by the coupled thereto microcontroller, a signal having a high frequency as possible f signal and / or the highest possible frequency resolution can be generated.
• the present invention is based on the finding that the calibration input of the oscillator can be used optimally to achieve the above-described object if it is correspondingly activated during operation of the electronic ballast.
• the electronic ballast further comprises a drive circuit which is coupled to the calibration input, wherein the drive circuit is designed to vary the first frequency f o sc in lau ⁇ fenden operation of the electronic ballast via the calibration input.
• This sets the frequency f signa of the periodic signal generated by the microcontroller during operation. represents, changed or finely adjusted by changing, ie recalibration, the frequency f o sc of the oscillator in lau ⁇ fenden operation.
• the resolution thereby achievable in the adjustment of the frequency f signa i of periodic signals is in particular independent of the ratio of the frequency fosc of the oscillator to the frequency f sign ai of the signal to be generated by the microcontroller. It is now only dependent on the resolution with which the frequency f O sc of the oscillator itself can be changed.
• the present invention allows the use of the internal RC oscillator of a microcontroller instead of an external oscillator in the prior art may be required to provide higher oscillator frequencies f o sc than those possible with the internal RC oscillator.
• the present invention can be implemented with the internal oscillator of a microcontroller or with an external oscillator of a microcontroller.
• the current ⁇ recording of the oscillator can be reduced, since this usually increases with the frequency f O sc.
• the tolerance of the frequency of a calibratable oscillator is usually higher than that of an oscillator, ie quartz or resonator, with a fixed frequency. Therefore, the present invention is particularly advantageously applicable if the exact absolute value of a set frequency f signal may have the appropriate tolerance, but it must be ensured that a certain frequency range is swept over by a specific time resolution signal with a specific resolution ( as is the case in the aforementioned application examples play ⁇ ).
• the oscillator is coupled to the microcontroller in such a way that it clocks the microcontroller.
• the microcontroller environmentally summarizes a timer device, in particular a pulse width modulation device, which is designed to provide the drive signal legizu ⁇ , the oscillator being so coupled to the microcontrollers roller that he tactical the timer device tet.
• the output compare value or the prescaler value of the timer device is changed.
• the electronic ballast comprises a calibration register which is coupled to the oscillator. It is further preferred if a prescribable value is adjustable in Kalibrati ⁇ onsregister, wherein the Kalibrationsregister is designed for changing the predetermined value during operation of the electronic pre-switching device.
• the frequency f O sc and thus the frequency fsignai can be changed in a particularly simple manner.
• the predefinable value can preferably be changed in steps of 0.5% to 10%. This allows a sufficiently fine frequency resolution to be achieved in most applications.
• the calibration register can be designed to store at least one predefinable value. Alternatively or additionally, it may also be provided to store the value of the calibration register in which a resonance has been detected, for example in order to avoid this (acoustic resonance) or to adjust it (ignition resonance).
• the ratio of f to f ai sign O sc is between 1.
• the oscillator is provided in the microcontroller as mentioned. According to a second preferred embodiment, however, the oscillator may also be provided outside the microcontroller. Further preferred embodiments emerge from the subclaims.
• Fig. 1 shows a schematic representation of the structure of an electronic ballast according to the invention.
• This comprises a block 10, in which the less prominent in view of the present invention ⁇ the elements that are well known in the art, are summarized.
• This is beispielswei ⁇ se to elements for radio interference suppression, for rectification, power factor correction, a bridge circuit coupling and resonance capacitors, a lamp inductor and the like.
• a light source ⁇ La here a discharge lamp, is Schlos ⁇ sen.
• the invention is readily applicable to other types of light sources.
• the electronic ballast shown in FIG. 1 comprises a supply voltage terminal U v , which is coupled on the one hand with the block 10, on the other hand with a microcontroller 12.
• the microcontroller 12 comprises an interface 14, via which access to a drive circuit 16 is made possible.
• the drive circuit 16 is coupled to a calibration register 18 and designed to vary the entry in the calibration register 18 during operation of the electronic ballast.
• the Kalibra ⁇ tion register 18 is coupled to the calibration input 20 of an oscillator 22 which provides a function of the voltage applied to input 20 is ⁇ nem signal, a signal having a frequency f 0Sc to a timer device 24th
• the timer device can in particular represent a pulse width modulation device.
• the timer device 24 provides at its output, which is coupled to the output of the microcontroller 12, a drive signal with at least one spectral component at the frequency f signa i for the at least one light source ⁇ beit, the timer device, the frequency f signa i as a function of Frequency f O sc generated, which is well known to the skilled person.
• the oscillator 22 may also be arranged outside the microcontroller 12, however, in order to control the microcontroller 12th While in the illustrated embodiment, the Os ⁇ zillator 22, the timer device 24 is clocked, can also be provided that the oscillator 22 clocks the microcontroller ler 12 itself, for example, via a clock input of the microcontroller 12th Accordingly, it is possible via the interface 14, using the drive circuit 16, which is coupled via the calibration register 18 with the calibration input 20 of the oscillator 22, during operation of the electronic ballast, the frequency f signa i at the output of the microcontroller 12 to change the signal provided.
• the signal provided at the output of the microcontroller 12 may for example be used to drive the switches of one half bridge circuit the half-bridge center point is ge ⁇ coupled to the output of A to drive the lamp La.
• the invention also finds application in setting a sequence of light changes in high temporal resolution, for example via a color wheel in projection lamps.
• the different light levels can be controlled with high temporal resolution and using an extremely cost-effective microcontroller.
• the microcontroller shown in FIG. 1 may, for example, be an ATMEL microcontroller of the AVR family.
• This includes an RC oscillator, via a calibration register 18 individual capacitors and ohmic resistors of the oscillator can be switched on or off. This is effected according to the invention during operation via the calibration input 20 of the oscillator 22.

Landscapes

• Circuit Arrangements For Discharge Lamps (AREA)
• Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

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• 2008
  • 2008-01-24 WO PCT/EP2008/050812 patent/WO2009092448A1/de active Application Filing
  • 2008-01-24 JP JP2010543391A patent/JP5595285B2/ja not_active Expired - Fee Related
  • 2008-01-24 US US12/864,253 patent/US8410719B2/en not_active Expired - Fee Related
  • 2008-01-24 CN CN200880125799.XA patent/CN101926230B/zh not_active Expired - Fee Related
  • 2008-01-24 EP EP08708151A patent/EP2232956A1/de not_active Withdrawn
  • 2008-01-24 KR KR1020107018798A patent/KR20100114100A/ko active IP Right Grant
• 2009
  • 2009-01-22 TW TW098102356A patent/TWI461112B/zh active

Non-Patent Citations (1)

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