Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
  • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
  • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
  • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/53—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M7/537—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
  • H02M7/5383—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
  • H02M7/53846—Control circuits
  • H02M7/53862—Control circuits using transistor type converters
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
  • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
  • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
  • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/53—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M7/537—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
  • H02M7/5383—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a self-oscillating arrangement
  • H02M7/53846—Control circuits
• • 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
  • H05B41/282—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
  • H05B41/2821—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 by means of a single-switch converter or a parallel push-pull converter in the final stage
  • H05B41/2824—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 by means of a single-switch converter or a parallel push-pull converter in the final stage using control circuits for the switching element
• • 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
  • H05B41/36—Controlling
  • H05B41/38—Controlling the intensity of light
  • H05B41/39—Controlling the intensity of light continuously
  • H05B41/392—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor
  • H05B41/3921—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations
  • H05B41/3927—Controlling the intensity of light continuously using semiconductor devices, e.g. thyristor with possibility of light intensity variations by pulse width modulation

Definitions

• the field of the invention is mainly that of light boxes used for illuminating visual display and display screens with an optical valve, in particular for liquid crystal matrix screens, also called LCD, which stands for “Liquid Crystal”. Displays ".
• the field of application is more particularly that of onboard visualizations on aircraft which require, for daytime use under strong sunlight and at night in low light, a great dynamic of adjustment of the amount of light emitted.
• This function of adjusting the light emitted is called in English terminology "dimming".
• the invention can also be applied to the consumer field of flat-screen displays used either as televisions or as microcomputer monitors and requiring a high luminance dynamics.
• the light sources of the light boxes are fluorescent tubes. These tubes are most often so-called cold cathode tubes that do not require preheating of the cathode filament. They are still called CCFL, acronym for "CoId Cathod Fluorescent Light". These light sources have many advantages such as their high brightness, their good conversion efficiency, their small size and their high reliability.
• FIG. 1 shows the schematic diagram of such a feeding device. It includes a device 1 of the inverter type. This device 1 is powered by a low voltage DC supply 2 of a few volts. The alternating high voltage is delivered to the fluorescent tubes 3 through so-called ballast capacitors C B , the latter limiting the current in the lamps.
• a "dimming" control 4 makes it possible to adjust the luminance emitted by the fluorescent tubes.
• a transformer comprising: a first primary magnetic coil comprising two parts P1 and P2, this coil is associated with a capacitor placed in parallel C A , a second secondary coil S HT and a third coil S R , said coils being conventionally wound around a magnetic circuit T, the voltage rise is substantially proportional to the ratio of the number of turns of the primary coil to the number of turns of the secondary coil;
• the transformer coil S H ⁇ provides the voltage rise and delivers a high voltage signal HT to the fluorescent lamps via the ballast capacitors C B which are associated with each fluorescent lamp.
• the transformer coil S R delivers a feedback signal to the tuned circuit for sustaining the oscillation.
• the self-induction L ⁇ makes it possible to polarize in high impedance the midpoint of the transformer, between the portions P1 and P2 of the first primary coil, to enable it to evolve in voltage.
• Q1 and Q2 controlled by an electronic device 10 placed across the coil S R. This device is supplied through the resistor R P by the power supply 2. Said switches each in turn turn the current supplied by the self-induction L ⁇ to the ground .
• Q1 and Q2 may be MOSFET transistors or bipolar transistors. Their control is then by the superposition of a common polarization fixed at the threshold of their conduction and the return voltage from the coil S R and applied in differential between the two switches.
• the dimming function realizes the modulation of the luminance. This is done by time modulation. This type of command is called PWM command, an acronym for Maise Width Modulation.
• PWM command an acronym for Maise Width Modulation.
• the duration of the active state is controlled over a fixed period of modulation time. The frequencies corresponding to this fixed period are generally between 100 and 300 Hz so as to be beyond the maximum frequencies perceptible by the human eye. Retinal persistence thus incorporates rapid variations in pulsed luminance and the eye perceives only an average luminance proportional to the ratio of the duration of the active state over the modulation period.
• the possible luminance dynamics are usually from 1 to 50, rarely beyond 1 to 100.
• the luminance dynamic requirement is from 1 to 1000 at the minimum.
• the control of the duration of the inactive state can be carried out on the Royer structure in two different ways: • Blocking of the two maintenance switches Q1 and Q2 as shown in Figure 3 where this function is performed by the switch QS T O P controlled by the "dimming" command. This blocking is obtained by grounding the polarization of the controls of the switches Q1 and Q2.
• This method has the disadvantage of introducing breaks of rhythm in the oscillation, when acts the protection against the overvoltage inherent in the flow of the energy stored in the self-induction L ⁇ . These breaks then create random response hazards of the low-cycle lamps or low PWM dimming lamps. We then observe beats of emitted light energy called in English terminology "flicker".
• the control of the active state starts at the time TO N and ends at the time T O FF. As can be seen, after the time T O FF, the tubes continue to emit for a certain time.
• the object of the invention makes it possible to overcome a large part of this defect.
• the object of the invention is to control more broadly the luminance modulation from lamps called CCFL and to allow the adjustment of luminance to a much lower minimum level than allowed by the usual basic structures.
• This invention can be applied, of course, to any device comprising a Royer oscillator requiring a rapid stop oscillation and is not limited to the fields of fluorescent lamps.
• the subject of the invention is an electronic oscillator known as Royer for generating, from a low DC voltage, high AC volts modulated temporally by cutting, comprising:
• a first circuit comprising a voltage transformer with primary and secondary coils and
• a second electronic feedback circuit for maintaining the frequency of the modulated alternating high voltage characterized in that it comprises an electronic device for controlling the discharge of the electrical energy stored in the first circuit, said discharge control device being controlled by an electronic control device by modulation by cutting.
• the electronic feedback circuit comprises two regulation switches arranged in series on either side of the primary coils of the transformer and the electronic device for controlling the discharge comprises means making it possible to bring said switches into simultaneous conduction.
• said regulation switches are connected to a common point, itself connected to the low voltage supply source through a so-called freewheeling diode, said common point being able to be grounded by a third switch controlled by the electronic control device by modulation by switching.
• the electronic device for controlling the discharge is controlled by the voltage of said common point.
• the transformer has an additive circuit comprising at least one secondary coil arranged in series between two switches connected to ground, the discharge device controlling the opening or closing of said switches.
• the additive circuit may further comprise at least two resistors placed in series between said coil and said switches.
• the additive circuit may also include an additional circuit comprising in series a capacitance and two switches connected to ground.
• the invention also relates to a power supply device for fluorescent tubes, characterized in that it comprises an electronic oscillator according to one of the characteristics defined above. It also relates to a flat-panel display device comprising at least one lighting source powered by the preceding power supply device.
• FIG. 1 represents the diagram of a high voltage power supply device controlled by "dimming"; • Figure 2 shows the electrical diagram of a Royer oscillator;
• FIG. 3 represents a first "dimming" control mode of a Royer oscillator
• FIG. 4 represents a second "dimming" control mode of a Royer oscillator
• Figure 5 shows the variations as a function of time of the main parameters in a Royer oscillator
• FIG. 6 represents the variations as a function of the "dimming" control of the emitted luminance
• FIG. 7 represents the electrical diagram of a Royer oscillator according to the invention
• FIG. 8 represents a variant of the Royer oscillator according to the invention.
• FIGS. 9, 10 and 11 represent 3 different embodiments of this variant
• FIG. 12 represents the variations as a function of time of the main parameters in a Royer oscillator according to the invention.
• FIG. 13 represents the variations as a function of the "dimming" control of the luminance emitted in a Royer oscillator according to the invention.
• the symbolic used on the different electrical diagrams corresponds to the one usually used for this type of diagrams.
• the junction nodes are represented by black circles.
• the invention consists in: stifling the oscillation at each stimulation train lamps. This amounts to discharging the energy stored in the resonant circuit automatically using simple electronics and synchronous operation.
• the discharge of the energy of the head inductor L ⁇ and of the parallel resonant circuit comprising the transformer and the tuning capacitor C A is achieved by short-circuiting the transformer.
• a first embodiment is shown in FIG. 7.
• the electronic device for controlling the discharge 11 of the electrical energy stored in the first circuit is controlled by the electronic modulation control device 4 by means of the QSTOP- switch
• the simultaneous conduction of the two maintenance switches of the oscillation Q1 and Q2 performs the function.
• This conduction is performed by acting on the electronic device 10 by the control 12 from the electronic control device 11.
• the dosage of the effect is to be adjusted to avoid fugitive returns in oscillation due to the residual energy of the self induction L ⁇ , the electronic components not being ideal. Even very short, these asynchronous oscillations can induce flicker of fluorescent lamps, detrimental to light stability.
• the advantage of this embodiment is that the original transformer is retained, only simple electronic components are added.
• the circuit comprises an additive circuit 13 comprising an additive winding S E in the transformer, which is then short-circuited by the electronic switches Q E 1 and Q E 2 as shown in Figure 9.
• These switches can be either MOS or bipolar transistors. It is interesting to arrange them in pairs to overcome the possible mono polarity defects inherent in their respective structure. These switches can be easily controlled because the additional coil being floating, it is possible to reference it to the electrical ground. Unlike the first embodiment, this therefore requires the addition of the additional winding S E to the original transformer and the set of switches Q E 1 and Q E 2.
• the effect of the The system can be dosed indifferently, and a partial effect can also be envisaged with series dissipation resistors R E 1 and R E 2 with the switches Q E 1 and Q E 2 as indicated in FIG.
• Boost tuning capacitor
• FIG. 12 illustrates the action of the electronic device for controlling the discharge of the stored electrical energy. This figure represents as a function of time the variations
• the control of the active state starts at the time TO N and ends at the time T O FF.
• the tubes continue to emit for a shorter time than the absence. of this circuit. It is possible to draw the curve of variation of the amount of light according to the duration of the active state of the PWM.
• the curve in FIG. 13 is obtained. This curve shows that it is now possible to reach the low luminances by this principle.
• the excitation time T MIN below which no light is emitted being considerably reduced, therefore, the minimum light emitted L MIN is also greatly reduced corresponding to the desired effect.

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• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
• Circuit Arrangements For Discharge Lamps (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=35149058

Family Applications (1)

Country Status (5)

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• 2005
  • 2005-03-01 FR FR0502064A patent/FR2882870B1/fr not_active Expired - Fee Related
• 2006
  • 2006-02-27 US US11/817,784 patent/US7893630B2/en not_active Expired - Fee Related
  • 2006-02-27 JP JP2007557487A patent/JP2008536459A/ja active Pending
  • 2006-02-27 EP EP06708538A patent/EP1854200A2/de active Pending
  • 2006-02-27 WO PCT/EP2006/060308 patent/WO2006092390A2/fr not_active Ceased

Non-Patent Citations (1)

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