WO2005117505A1 - 放電灯用点灯装置 - Google Patents
放電灯用点灯装置 Download PDFInfo
- Publication number
- WO2005117505A1 WO2005117505A1 PCT/JP2005/002851 JP2005002851W WO2005117505A1 WO 2005117505 A1 WO2005117505 A1 WO 2005117505A1 JP 2005002851 W JP2005002851 W JP 2005002851W WO 2005117505 A1 WO2005117505 A1 WO 2005117505A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- tube current
- discharge lamp
- circuit
- control circuit
- switching
- Prior art date
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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
- H05B41/282—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
- H05B41/2825—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 bridge converter in the final stage
- H05B41/2828—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 bridge converter in the final stage using control circuits for the switching elements
-
- 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
Definitions
- the present invention relates to a lighting device for a discharge lamp such as a cold cathode tube or a fluorescent lamp.
- the discharge lamp requires a high voltage at the time of starting (at the time of the first lighting), but can be lit at a lower voltage than the starting at the time of continuous lighting. Therefore, it is inefficient to boost the voltage to the voltage required at the time of starting only by the winding transformer. Therefore, the boosting ratio of the winding transformer is set to a level necessary for continuous lighting, and the voltage shortage at the time of startup is reduced. To compensate for this, a capacitor that performs series resonance with the leakage inductance of the secondary winding is provided on the secondary side of the transformer, and startup is performed using the characteristic that the boost ratio near the resonance point of this series resonance increases. The configuration is generally adopted.
- a PWM pulse width control
- a switching duty ratio is used as a method of performing switching control by detecting a current (tube current) flowing through a discharge lamp. The method is generally adopted.
- Fig. 8 shows a configuration of a discharge lamp lighting device including a full bridge circuit.
- a full bridge circuit 11 is constituted by four switch elements Q1 Q4 and a transformer T (primary winding L1 of the transformer T).
- the switching control circuit 20 for driving the first and second switching elements Ql and Q2 is composed of a switching circuit 21 and a PWM control unit 23.
- the third and fourth switch elements Q3 and Q4 are similarly controlled by the switching control circuit 20, but the connection relation is not shown in FIG. [0006]
- resonance is caused by the leakage inductance of the secondary winding L2 and the resonance capacitor Cr so that a driving voltage is applied to the discharge lamp 3.
- the current detection unit 4 detects the tube current of the discharge lamp 3 and feeds it back to the PWM control unit 23.
- FIG. 9 shows the voltages V, V at points A and B at both ends of primary winding L1 of transformer T shown in FIG.
- FIG. 7 is a waveform diagram of a voltage between both ends of a primary winding L1 of a transformer T.
- Ql and Q2 are turned on and off alternately at a duty ratio of 50%.
- Q3 and Q4 are alternately turned on and off at a duty ratio of 50%.
- the phase is shifted and the voltage is applied to the primary winding of the transformer shown in the figure.
- Tba time is PWM controlled.
- Patent Document 1 Japanese Patent Application Laid-Open No. 8-162280
- a voltage waveform applied to the discharge lamp has a ternary staircase waveform, so that many harmonic currents flow. As a result, there is a problem that the brightness of the discharge lamp is reduced.
- a full-bridge switching circuit has a disadvantage in that it is expensive because it requires four switch elements using FETs. Therefore, it is conceivable to configure a half-bridge switching circuit as shown in Patent Document 1.
- FIG. 6 shows a configuration example of a discharge lamp lighting device including a half-bridge circuit. Unlike the circuit shown in FIG. 8, the primary winding L1 of the transformer T is connected between the connection points of the series circuit of the two switch elements Ql and Q2 and the series circuit of the two capacitors C1 and C2.
- the half bridge circuit 1 is configured.
- FIG. 7 is a waveform diagram showing states of the first and second switch elements Ql and Q2 of the circuit shown in FIG. 6 and a voltage between both ends of the primary winding L1 of the transformer T.
- FIG. 7A shows a state where the on-duty ratios of Ql and Q2 are relatively large
- FIG. 7B shows a state where the on-duty ratios are relatively small.
- the duty was fixed at 50% and the phase was changed to control the effective PWM control of the voltage applied to the transformer.
- the switch was actually switched. By changing the on / off duty ratio of the element Performs PWM control.
- An object of the present invention is to provide a lighting device for a discharge lamp in which a cost reduction is achieved by providing a half-bridge circuit, and a problem caused by a current flowing through a body diode of a switch element is eliminated to enhance power conversion efficiency. Is to provide.
- a series circuit of first and second switch elements each composed of an FET and a series circuit of two capacitors are connected between both ends of an input power supply.
- a half-bridge circuit in which a primary winding of a transformer is connected between the connection point of the two capacitors and the connection point of the first and second switch elements, and the first and second switch elements alternately.
- a switching control circuit for turning on and off is provided, and a driving voltage is supplied from the secondary side of the transformer to the discharge lamp.
- the switching control circuit includes approximately 50 first and second switch elements. / o It is characterized by providing a tube current control circuit for switching at a duty ratio and controlling a tube current by controlling a variation factor of a tube current flowing through the discharge lamp.
- the lighting device for a discharge lamp according to the present invention further includes a tube current detection circuit for directly or indirectly detecting a tube current flowing through the discharge lamp, and the tube current control circuit.
- a tube current detection circuit for directly or indirectly detecting a tube current flowing through the discharge lamp
- the tube current control circuit for directly or indirectly detecting a tube current flowing through the discharge lamp
- the tube current control circuit controls the tube current by controlling a switching frequency of the switching control circuit.
- the tube current control circuit controls the tube current by controlling a voltage of the input power supply.
- the first and second switch elements are switched at a duty ratio of about 50%, there is almost no period in which current flows through the body diodes of the first and second switch elements, and the on-state voltage is small.
- Transformers and discharge lamps can be driven by conduction between the drain and source, reducing overall loss and increasing power conversion efficiency.
- the switching is performed at a duty ratio of 50%, the main component of the driving frequency is larger than the harmonic component, and the secondary current waveform becomes closer to a sine wave, and the brightness of the discharge lamp increases.
- the tube current detection circuit detects the current flowing through the discharge lamp and the tube current control circuit controls the tube current based on the tube current detection signal, the lamp current becomes stable, for example, the brightness of the discharge lamp becomes constant. Lighting control can be performed.
- the tube current control circuit controls the switching frequency based on the tube current detection signal to maintain the tube current at a predetermined value, the tube current control circuit is not affected by fluctuations in the input power supply voltage or fluctuations in the discharge lamp temperature. And stable lighting control can be performed.
- the tube current control circuit controls the voltage of the input power supply based on the tube current detection signal to maintain the tube current at a predetermined value, the switching frequency and the discharge lamp temperature vary. Irrespective of the above, stable lighting control can be performed.
- FIG. 1 is a circuit diagram of a lighting device for a discharge lamp according to a first embodiment.
- FIG. 2 is a diagram showing ON / OFF periods of first and second switch elements Ql and Q2 of the same device and waveforms of a voltage across a primary winding L1 of a transformer.
- FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a second embodiment.
- FIG. 4 is a circuit diagram of a discharge lamp lighting device according to a third embodiment.
- FIG. 5 is a circuit diagram of a discharge lamp lighting device according to a fourth embodiment.
- FIG. 6 is a circuit diagram of a discharge lamp lighting device including a conventional half-bridge circuit.
- FIG. 7 is a waveform chart of each part of the device.
- FIG. 8 is a circuit diagram of a conventional lighting device for a discharge lamp including a full bridge circuit.
- FIG. 9 is a waveform chart of each part of the device.
- Figure 1 is the circuit diagram. Input power supply Vin A series circuit of two switch elements Ql and Q2 and a series circuit of two capacitors CI and C2 are connected respectively.
- the primary winding L1 of the transformer T is connected between the connection point of the two capacitors CI and C2 and the connection point of the first and second switch elements Ql and Q2.
- the half bridge circuit 1 is configured by this configuration.
- the switching control circuit 2 includes a switching circuit 2 that alternately turns on and off the first and second switch elements Ql and Q2, and a PFM control unit 22 that controls the switching frequency with a duty ratio of approximately 50%. .
- a resonance capacitor Cr and a discharge lamp 3 are connected between both ends of the secondary winding L2 of the transformer T.
- a current detection unit 4 for detecting the tube current is provided in the tube current supply path of the discharge lamp 3.
- the current detection unit 4 directly detects the tube current by inserting a resistor having a low resistance value into a path through which the tube current flows, and detecting the voltage drop.
- the tube current may be detected indirectly by detecting the intensity of a magnetic field generated around a line through which the tube current flows. Further, the tube current may be detected indirectly by detecting another meter that changes in response to the change in the tube current.
- the resonance capacitor Cr and the secondary winding L2 of the transformer T form a series resonance circuit.
- the resonance frequency is determined by the secondary leakage inductance of the transformer T, the capacitance of the resonance capacitor Cr, the parasitic capacitance and impedance of the discharge lamp 3, and the line capacitance on the secondary side of the transformer T.
- the inductance of the primary winding L1 of the transformer T is about 60 ⁇ m, and the primary-side leakage inductance is 15 ⁇ m (the primary-side leakage inductance is not shown as a symbol in the figure.)
- the inductance of the secondary winding L2 is about 600mH, and the secondary leakage inductance L2 'is about 150mH.
- the voltage of the input power supply Vin is 24V, and the output voltage is about lkVrms.
- FIG. 2 shows the on / off periods of the two switch elements Ql and Q2 shown in FIG. The waveform of the voltage between both ends of the next winding LI is shown.
- T1 is the ON period of Q1
- T2 is the ON period of Q2
- T3 and T4 are the periods (dead time) in which both Ql and Q2 are off.
- the current detection unit 4 shown in Fig. 1 detects the tube current flowing through the discharge lamp 3, and the PFM control unit 22 switches the switching circuit 21 based on the tube current detection signal so that the tube current is stabilized. Control the tuning frequency. For example, when using a characteristic region in which the applied voltage to the discharge lamp 3 increases as the switching frequency increases, the feedback control is performed so that the switching frequency decreases as the tube current detected by the current detector 4 increases. Do.
- the relationship between the switching frequency and the voltage applied to the discharge lamp 3 is determined by the resonance characteristics of the series resonance circuit including the secondary leakage inductance of the transformer T and the resonance capacitor Cr and the like. That is, the applied voltage to the discharge lamp 3 becomes the maximum at the resonance frequency of the series resonance circuit, and the applied voltage decreases even if the switching frequency becomes higher or lower than that.
- the configuration of the discharge lamp lighting device according to the second embodiment will be described with reference to FIG. 3.
- the difference from the first embodiment is that the primary winding L1 of the transformer T is different from the first embodiment. This is the point where the inductor Lp is connected in series.
- the secondary side leakage inductance of the transformer T is equivalently increased.
- the secondary side leakage inductance can be adjusted with an external coil. For example, if an inductor Lp of about 10 ⁇ H is introduced, the secondary leakage inductance can be equivalently increased by about 60 mH. Other effects are the same as those of the first embodiment.
- a lighting device for a discharge lamp according to a third embodiment will be described with reference to FIG. 4.
- two transformers Ta and Tb are used, and their primary windings Lla and Lib are connected to each other. Are connected in parallel and driven by a half-bridge circuit, the secondary windings L2a and L2b are connected in series, and a driving voltage is output to the discharge lamps 3a and 3b.
- a series circuit of resonance capacitors Cra and Crb is connected in parallel to the series circuit of discharge lamps 3a and 3b.
- the connection point of the resonance capacitors Cra and Crb is connected to the ground of the input power supply Vin.
- the current detection unit 4 is provided in a path where the tube current of the discharge lamps 3a and 3b flows.
- two discharge lamps can be driven using a single switching control circuit 2 and a single current detection unit 4.
- the power conversion efficiency can be increased by shortening the time for which the body diodes of the switching elements Ql and Q2 are energized while keeping the tube current flowing through the two discharge lamps 3a and 3b uniform.
- the switching frequency is controlled as a variable factor of the tube current.
- the tube current is controlled by controlling the input power supply voltage as a variable factor of the tube current.
- the switching circuit 2 turns on and off the first and second switch elements Ql and Q2 alternately at a duty ratio of almost 50%.
- the self-excited oscillation frequency becomes the switching frequency of Ql and Q2.
- the switching circuit 2 When the switching circuit 2 generates a rectangular wave signal in synchronization with a synchronization signal input from the outside as shown by a broken line in the figure, the switching frequency is determined by the external synchronization signal.
- the switching circuit 2 may be configured to output a rectangular wave signal having a switching frequency from the outside and drive the Ql and Q2 on and off with the signal.
- the power supply circuit 5 receives an AC power supply AC and outputs a predetermined DC voltage V.
- the power supply circuit 5 has a tube current of a predetermined value.
- the voltage value of DC voltage V is controlled so as to be constant. Therefore, the power supply circuit 5 reduces the DC voltage V when the tube current is larger than a predetermined value, and conversely, when the tube current is smaller than the predetermined value, the DC voltage V To rise.
- the amplitude of the AC voltage applied to the primary side of the transformer T decreases, and the amplitude of the voltage on the secondary side, that is, the amplitude of the voltage applied to the discharge lamp 3 correspondingly decreases.
- the tube current decreases.
- the DC voltage V rises the tube current increases due to the opposite effect.
- the first and second switch elements are switched at a duty ratio of approximately 50%, the overall loss is reduced and the power conversion efficiency is reduced, as in the first to third embodiments. Increase.
- the secondary current waveform becomes closer to that of a sine wave, and the brightness of the discharge lamp increases.
- the tube current is maintained at a predetermined value, so that the following effects are obtained.
- Stable lighting control can be performed, for example, by keeping the luminance constant irrespective of the fluctuation of the switching frequency or the fluctuation of the temperature of the discharge lamp.
- the switching frequency can be set arbitrarily, for example, the switching frequency can be set to a frequency other than the frequency that should be avoided as unnecessary radiation noise.
- the switching frequency and the ON / OFF timing can be synchronized in synchronization with the external synchronization signal. This allows the synchronous operation to be performed when a plurality of discharge lamp lighting devices are operated in parallel. It becomes possible. As a result, it is possible to avoid the problem of generation of a beat signal due to different switching frequencies of the individual lighting devices for discharge lamps.
- power supply circuit 5 receives AC input voltage AC and
Abstract
Description
Claims
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2004162420 | 2004-05-31 | ||
JP2004-162420 | 2004-05-31 | ||
JP2004264076 | 2004-09-10 | ||
JP2004-264076 | 2004-09-10 |
Publications (1)
Publication Number | Publication Date |
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WO2005117505A1 true WO2005117505A1 (ja) | 2005-12-08 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2005/002851 WO2005117505A1 (ja) | 2004-05-31 | 2005-02-23 | 放電灯用点灯装置 |
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Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07194142A (ja) * | 1993-12-28 | 1995-07-28 | Isao Takahashi | 放電灯点灯装置 |
JPH11111475A (ja) * | 1997-09-30 | 1999-04-23 | Toshiba Lighting & Technology Corp | 放電ランプ点灯装置および照明装置 |
-
2005
- 2005-02-23 WO PCT/JP2005/002851 patent/WO2005117505A1/ja active Application Filing
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH07194142A (ja) * | 1993-12-28 | 1995-07-28 | Isao Takahashi | 放電灯点灯装置 |
JPH11111475A (ja) * | 1997-09-30 | 1999-04-23 | Toshiba Lighting & Technology Corp | 放電ランプ点灯装置および照明装置 |
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