US20080106220A1 - Discharge lamp lighting apparatus - Google Patents
Discharge lamp lighting apparatus Download PDFInfo
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- US20080106220A1 US20080106220A1 US11/953,951 US95395107A US2008106220A1 US 20080106220 A1 US20080106220 A1 US 20080106220A1 US 95395107 A US95395107 A US 95395107A US 2008106220 A1 US2008106220 A1 US 2008106220A1
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- discharge lamp
- voltage
- capacitor
- discharge
- current
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- 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
- H05B41/16—Circuit arrangements in which the lamp is fed by dc or by low-frequency ac, e.g. by 50 cycles/sec ac, or with network frequencies
-
- 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
- H05B41/382—Controlling the intensity of light during the transitional start-up phase
- H05B41/388—Controlling the intensity of light during the transitional start-up phase for a transition from glow to arc
-
- 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
- H05B41/2881—Load circuits; Control thereof
-
- 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
- H05B41/2881—Load circuits; Control thereof
- H05B41/2882—Load circuits; Control thereof the control resulting from an action on the static converter
- H05B41/2883—Load circuits; Control thereof the control resulting from an action on the static converter the controlled element being a DC/AC converter in the final stage, e.g. by harmonic mode starting
-
- 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
- H05B41/2885—Static converters especially adapted therefor; Control thereof
- H05B41/2886—Static converters especially adapted therefor; Control thereof comprising a controllable preconditioner, e.g. a booster
-
- 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
- H05B41/2885—Static converters especially adapted therefor; Control thereof
- H05B41/2887—Static converters especially adapted therefor; Control thereof characterised by a controllable bridge in the final stage
- H05B41/2888—Static converters especially adapted therefor; Control thereof characterised by a controllable bridge in the final stage the bridge being commutated at low frequency, e.g. 1kHz
-
- 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
- H05B41/382—Controlling the intensity of light during the transitional start-up phase
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Circuit Arrangements For Discharge Lamps (AREA)
Abstract
A discharge lamp lighting apparatus includes a DC-DC converter for outputting voltages having respective different potentials from two wirings, a switching circuit having input terminals connected to the two wirings, an output terminal connected to one electrode of a discharge lamp, and a capacitor having one electrode terminal connected to a second electrode of the discharge lamp and a second electrode terminal connected to one of the two wirings of the DC-DC converter. The switching circuit includes a switching element for controlling connections between one of the two wirings and the output terminal. The other wiring is connected to the output terminal.
Description
- This invention relates to a discharge lamp lighting apparatus used for an automobile or a light source of a projection display.
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FIG. 18 is a circuit configuration diagram showing a conventional discharge lamp lighting apparatus disclosed in the Unexamined Japanese Patent Application Publication No. Hei 12-82592. In the drawing,numeral 1 is a direct current power source such as a battery, andnumeral 2 is a DC-DC converter for regulating and outputting electric power supplied from the directcurrent power source 1 and in the DC-DC converter 2,numeral 2 a is a transformer andnumeral 2 b is an FET (Field Effect Transistor) andnumeral 2 c is a diode.Numeral 3 is a ground, andnumeral 4 is a shunt resistor for detection of a discharge lamp current IL, andnumeral 50 is a full bridge circuit (hereinafter called “H bridge”) which is formed ofFETs 50 a to 50 d in H shape and converts direct current electric power regulated by the DC-DC converter 2 into alternating current electric power, andnumeral 6 is a discharge lamp driven by the alternating current electric power converted by theH bridge 50. - Also,
numeral 7 is an interface (thereinafter called “I/F”) which inputs a discharge lamp voltage VL from the side of a cathode of output of the DC-DC converter 2 and also inputs the discharge lamp current IL from the side of theH bridge 50 of theshunt resistor 4, andnumeral 8 is a microcomputer for controlling theFET 2 b of the DC-DC converter 2 so that electric power supplied to thedischarge lamp 6 based on the discharge lamp voltage VL, the discharge lamp current IL and a preset circuit impedance fixed value sequentially detected through the I/F 7 is made to a predetermined value. - Next, operations will be described. In the case of starting to light the
discharge lamp 6, the electric power supplied from the directcurrent power source 1 is regulated and outputted by the DC-DC converter 2 and further the DC electric power is converted into the AC electric power by theH bridge 50 to drive thedischarge lamp 6. Here, the discharge lamp voltage VL detected from the side of the cathode of the output of the DC-DC converter 2 is increased to −400 V as shown inFIG. 19 and is further increased to about 20 kV in the peak and then thedischarge lamp 6 lights and thereafter becomes in a stable state of lighting at −90 V. Such control is performed by controlling theFET 2 b of the DC-DC converter 2 so that the electric power supplied to thedischarge lamp 6 based on the discharge lamp voltage VL and the discharge lamp current IL sequentially detected through the I/F 7 is made to the predetermined value by means of themicrocomputer 8. - After
discharge lamp 6 lights, an AC voltage is applied to thedischarge lamp 6 by repeating the switch state with theFETs H bridge 50 turned on and theFETs FETs FETs - By the way, it is desirable that the discharge lamp electric power supplied to the
discharge lamp 6 in the stable state of lighting be 34 W. However, in case of merely controlling the electric power supplied to thedischarge lamp 6 based on the discharge lamp voltage VL and the discharge lamp current IL at 34 W by themicrocomputer 8, there is a loss due to a voltage drop by ON resistance of theFETs 50 a to 50 d of theH bridge 50, so that the electric power supplied to thedischarge lamp 6 actually becomes lower than 34 W. Thus, the circuit impedance fixed value is set previously in expectation of the drop by ON resistance of theFETs 50 a to 50 d of theH bridge 50 and on the basis of the discharge lamp voltage VL, the discharge lamp current IL and the preset circuit impedance fixed value by themicrocomputer 8, control is performed so that the electric power supplied to thedischarge lamp 6 is made to 34 W even in case where there is the power loss due to the drop by ON resistance of theFETs 50 a to 50 d of theH bridge 50. - The conventional discharge lamp lighting apparatus is configured as described above and a high voltage of a maximum of 400 V is applied to the
H bridge 50, so that the FETs constructing theH bridge 50 need to have high withstand voltage properties capable of withstanding 400 V. Such FETs having the high withstand voltage properties are high in unit price and also the four FETs with such a high unit price are used in the conventional configuration. Therefore, a configuration of an inverter circuit by the H bridge as described above has become one bad effect in the case of achieving miniaturization and cost reduction, and a reduction in the number of FET elements of theH bridge 50 or a decrease in the voltage applied to the H bridge has become problems of the discharge lamp lighting apparatus. - The invention is implemented to solve such problems, and it is an object of the invention to achieve miniaturization and cost reduction by performing a reduction in the number of elements constructing discharge lamp drive means (inverter circuit portion) for converting a direct current voltage into an alternating current voltage to drive a discharge lamp or a decrease in the voltage applied to the discharge lamp drive means.
- A discharge lamp lighting apparatus according to a first configuration of the invention comprises electric power regulating means for regulating electric power supplied from a power source and outputting voltages having respective different potentials from two wirings, a switching circuit part formed of one switching element in which input terminals are connected to the two wirings of the electric power regulating means and also one input terminal of the input terminals is connected to one electrode of a discharge lamp and an output terminal is connected to the other electrode of the discharge lamp, and a capacitor connected in series with the discharge lamp in a circuit for making connections of one input terminal of the switching circuit part, the discharge lamp and the output terminal of the switching circuit part.
- Also, with a discharge lamp lighting apparatus according to a second configuration of the invention, in the first configuration, the discharge lamp is driven with alternating current by repeating a process of supplying a current from the electric power regulating means to the discharge lamp and performing charge to the capacitor and a process of stopping actuation of the electric power regulating means and supplying a reverse directional current from the capacitor to the discharge lamp.
- Also, with a discharge lamp lighting apparatus according to a third configuration of the invention, in the first or second configuration, a standby period for making preparations for lighting, an electrode heating period for detecting at least a voltage VC of the capacitor to heat the electrodes of the discharge lamp by a discharge lamp current until the voltage VC reaches a predetermined voltage after the discharge lamp is lighted, and an AC discharge period for passing an AC current through the discharge lamp to sustain discharge are provided.
- Also, with a discharge lamp lighting apparatus according to a fourth configuration of the invention, in one of the first to third configurations, one input terminal of the switching circuit part is connected to the output terminal through the switching element and the other input terminal of the switching circuit part is directly connected to the output terminal.
- Also, with a discharge lamp lighting apparatus according to a fifth configuration of the invention, in one of the first to fourth configurations, the switching element comprises means for regulating a control voltage so that a discharge lamp current becomes a predetermined value.
- Also, with a discharge lamp lighting apparatus according to a sixth configuration of the invention, in one of the first to fifth configurations, voltage smoothing and initial current supply means for smoothing a voltage outputted by the electric power regulating means and supplying a current to the discharge lamp at the time of discharge start is provided.
- Also, with a discharge lamp lighting apparatus according to a seventh configuration of the invention, in the sixth configuration, a dead period overlaying a period of stopping actuation of the electric power regulating means on an OFF period of the switching element is provided when performing AC drive of the discharge lamp.
- Also, with a discharge lamp lighting apparatus according to an eighth configuration of the invention, in the sixth configuration, the voltage smoothing and initial current supply means is formed by placing a second capacitor in parallel with a circuit in which a parallel circuit of a resistor and a diode is connected in series with a first capacitor.
- Also, a discharge lamp lighting apparatus according to a ninth configuration of the invention comprises electric power regulating means for regulating electric power supplied from a power source and outputting positive and negative binary voltages from two wirings, and a switching circuit part formed of first and second switching elements for controlling connections between the two wirings of the electric power regulating means and one electrode of a discharge lamp, and it is constructed so that the other electrode of the discharge lamp becomes a center voltage level of the positive and negative binary voltages.
- Also, with a discharge lamp lighting apparatus according to a tenth configuration of the invention, in the ninth configuration, a third switching element is placed between one wiring of the two wirings of the electric power regulating means and the switching circuit part, and the third switching element is made in the OFF state during a standby period for making preparations for lighting.
- Also, with a discharge lamp lighting apparatus according to an eleventh configuration of the invention, in the ninth configuration, the electric power regulating means has three terminals for outputting a positive voltage, a ground voltage and a negative voltage, and a voltage clamping element is connected between a ground terminal for outputting the ground voltage and a voltage terminal for outputting the positive or negative voltage.
- Also, with a discharge lamp lighting apparatus according to a twelfth configuration of the invention, in the eleventh configuration, three voltage levels consisting of the positive voltage, the ground voltage and the negative voltage are formed by using two transformers.
- Also, with a discharge lamp lighting apparatus according to a thirteenth configuration of the invention, in the eleventh configuration, three voltage levels consisting of the positive voltage, the ground voltage and the negative voltage are formed by using an integral transformer in which a primary winding and a secondary winding are placed in one end of a core and another primary winding and a tertiary winding are placed in the other end.
- Also, a discharge lamp lighting apparatus according to a fourteenth configuration of the invention comprises electric power regulating means for regulating electric power supplied from a power source and outputting voltages having respective different potentials from four wirings, a switching circuit part formed of four switching elements for controlling connections between the two wirings of the four wirings of the electric power regulating means and electrodes of a discharge lamp, and a capacitor which is connected between output terminals of the switching circuit part and supplies a current to the discharge lamp at the time of discharge start, and the residual two wirings of the four wirings of the electric power regulating means are connected to respective electrodes of the capacitor and the four switching elements are made in the OFF state during a standby period for making preparations for lighting.
- Also, with a discharge lamp lighting apparatus according to a fifteenth configuration of the invention, in one of the first to fourteenth configurations, the discharge lamp has an igniter circuit.
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FIG. 1 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a first embodiment of the invention; -
FIG. 2 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the first embodiment of the invention; -
FIG. 3 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a second embodiment of the invention; -
FIG. 4 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the second embodiment of the invention; -
FIG. 5 is a chart showing timing of a signal waveform during an AC discharge period of a discharge lamp lighting apparatus according to a third embodiment of the invention; -
FIG. 6 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a fourth embodiment of the invention; -
FIG. 7 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a fifth embodiment of the invention; -
FIG. 8 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a sixth embodiment of the invention; -
FIG. 9 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the sixth embodiment of the invention; -
FIG. 10 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a seventh embodiment of the invention; -
FIG. 11 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the seventh embodiment of the invention; -
FIG. 12 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to an eighth embodiment of the invention; -
FIG. 13 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the eighth embodiment of the invention; -
FIG. 14 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a ninth embodiment of the invention; -
FIG. 15 is a configuration view of a transformer according to the ninth embodiment of the invention; -
FIG. 16 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a tenth embodiment of the invention; -
FIG. 17 is a waveform chart showing a signal waveform, a voltage waveform and a discharge lamp current waveform of the discharge lamp lighting apparatus according to the tenth embodiment of the invention; -
FIG. 18 is a circuit configuration diagram of a conventional discharge lamp lighting apparatus; and -
FIG. 19 is a waveform chart showing a voltage waveform at the time of starting in the conventional discharge lamp lighting apparatus. - A first embodiment will be described below using the accompanying drawings.
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FIG. 1 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to the first embodiment of the invention. InFIG. 1 ,numeral 1 is a direct current power source such as a battery, andnumeral 2 is a DC-DC converter (electric power regulating means) for regulating and outputting electric power supplied from the directcurrent power source 1, and the DC-DC converter 2 comprises atransformer 2 a, anFET 2 b, adiode 2 c and acapacitor 2 d. Thecapacitor 2 d has functions of flowing a current into a discharge lamp at the time of starting an electric discharge and smoothing an output voltage (voltage smoothing and initial current supply means).Numeral 3 is a ground, andnumeral 4 is a shunt resistor for detection of a discharge lamp current IL, andnumeral 5 is a switching circuit and in theswitching circuit 5, input terminals of the switching circuit are connected to two wirings of the DC-DC converter and one input terminal is connected to an output terminal through a switching element (FET) 5 b and the other input terminal is directly connected to the output terminal and the output terminal is connected to one electrode of adischarge lamp 6.Numeral 7 is an I/F, andnumeral 8 is a microcomputer.Numeral 9 is an igniter circuit having a function of applying a high voltage of the order of 20 kV to the discharge lamp at the time of starting the discharge, and theigniter circuit 9 comprises apulse transformer 9 a with a winding ratio of 1:100, acapacitor 9 b for storing energy of discharge starting, agap switch 9 c for conduction with 400 V, a 10kΩ resistor 9 e for determining time from switch on to discharge starting, adiode 9 f for reverse flow prevention, and acapacitor 9 d for flowing a high peak and short pulse current into thedischarge lamp 6 at the time of the discharge starting.Numeral 10 is a capacitor of electrolytic type with a sufficiently large capacity and thecapacitor 10 is a capacitor for DC pulse to AC pulse conversion for converting a DC pulse voltage into an AC voltage pulse between electrodes of thedischarge lamp 6. Thecapacitor 10 is placed in series with thedischarge lamp 6 in a circuit for connecting one input terminal (input terminal of the side of theFET 5 b) of theswitching circuit 5 to theigniter circuit 9. Also, thecapacitor 10 is connected in parallel with adiode 12 constructed so that a reverse polarity voltage is not applied to thecapacitor 10 and a 10 kΩ to 1MΩ resistor 11 for protection. - Next, connections of each the circuit element will be described.
- In
FIG. 1 , the plus side of theDC power source 1 is connected to the winding end side of a primary winding of thetransformer 2 a and the winding start side of the primary winding is connected to a drain of theFET 2 b. Theground 3 is connected to a source of the FET 2 b and the minus side of theDC power source 1. A signal Sig.3 from themicrocomputer 8 is inputted to a gate of theFET 2 b. The winding start side of a secondary winding of thetransformer 2 a is connected to an anode of thediode 2 c and the winding end side is connected to theground 3. A cathode of thediode 2 c is connected to one electrode of thecapacitor 2 d and the other input terminal of theswitching circuit 5. The other input terminal of theswitching circuit 5 is directly connected to the output terminal and also is connected to a drain of theFET 5 b and further a source of theFET 5 b is connected to theground 3 through theshunt resistor 4. A signal Sig.2 from the microcomputer is inputted to a gate of theFET 5 b. The output terminal of theswitching circuit 5 is connected to one electrode of thedischarge lamp 6 and is further connected to anodes of thecapacitor 9 d and thediode 9 f of theigniter circuit 9. A cathode of thediode 9 f is connected to one electrodes of thecapacitor 9 b and thegap switch 9 c through theresistor 9 e. The other electrode of thegap switch 9 c is connected to the other electrodes of thecapacitors pulse transformer 9 a and is further connected to the other electrode of thedischarge lamp 6 through a secondary winding of thepulse transformer 9 a. An anode of thecapacitor 10, theresistor 11 and a cathode of thediode 12 are connected to thecapacitors pulse transformer 9 a, and a cathode of thecapacitor 10, the other electrode of theresistor 11 and an anode of thediode 12 are connected to theground 3 through theshunt resistor 4. - Also, a voltage VL of the other input terminal (input terminal directly connected to the output terminal) of the
switching circuit 5, a discharge lamp current IL detected from theshunt resistor 4 and a voltage VC of thecapacitor 10 for DC pulse to AC pulse conversion are inputted to themicrocomputer 8 through the I/F 7. TheFETs microcomputer 8. - Then, operations will be described.
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FIG. 2 is a timing chart showing input signals of the control signals Sig.2, Sig.3 and output waveforms of the voltages VL, VC and the discharge lamp current. First, when a switch of thepower source 1 is turned on, a pulse signal is generated in the signal Sig.3 and thereby, the DC-DC converter 2 operates, and the signal Sig.2 becomes low and thereby, theFET 5 b is turned off. The Sig.3 is a pulse signal with 100 kHz and the pulse signal is controlled while comparing a value of the voltage VL with a preset voltage value, and a gate signal of theFET 2 b of the DC-DC converter 2 is controlled and thereby, the voltage VL monotonously increases to 400 V and thecapacitor 2 d is charged. Since the other input terminal of theswitching circuit 5 is directly connected to the output terminal, at the same time, thecapacitor 9 b connected in parallel with thegap switch 9 c as well as thecapacitor 9 d are charged. This period is a period for making lighting preparations and is called a standby period. - When a voltage stored in the
capacitors gap switch 9 c conducts and a large current flows in the primary winding of thepulse transformer 9 a and a high voltage of about 20 kV is generated in the secondary winding of thepulse transformer 9 a and a current (breakdown current) with a high peak and a short pulse width flows in thedischarge lamp 6 and a gas discharge starts. While a voltage between electrodes of thedischarge lamp 6 sharply drops by the gas discharge, an electric charge stored in thecapacitor 2 d of the DC-DC converter 2 flows into thedischarge lamp 6 through the other input terminal and the output terminal of theswitching circuit 5, and the gas discharge is held (gas discharge growth current). Thereafter, a current of the order of 1 A continues to be supplied to thedischarge lamp 6 by the DC-DC converter 2. When thedischarge lamp 6 starts to discharge, thecapacitor 10 is charged through thedischarge lamp 6 and the voltage VC starts to increase. Until the voltage VC increases to the order of 140 V of a value set in the microcomputer B, the process of continuing to pass a current through thedischarge lamp 6 in this DC manner. This period is called an electrode heating period. This electrode heating period is provided for heating the electrodes of the discharge lamp to sufficiently decrease a discharge voltage and also is provided for increasing to a sufficient value to discharge a voltage applied to thedischarge lamp 6 at the time of reversing a switching state of theFET 5 b. The voltage is found to be preferably 100 V or higher from the experiment. - When the voltage VC reaches 140 V of the internal setting value of the
microcomputer 8, a pulse signal of the Sig.3 is stopped and the DC-DC converter 2 is stopped and the Sig.2 is made high and theFET 5 b is made in the ON state and an electric charge stored in thecapacitor 10 is supplied to thedischarge lamp 6. A current flows through thedischarge lamp 6 in a direction reverse to the previous period. For the electrode heating period, the voltage of as high as 140 V is applied to the discharge lamp under the condition that the discharge voltage decreases to 40 V to 90 V, so that a current larger than that of the previous period flows, but a capacity value of thecapacitor 10 for DC pulse to AC pulse conversion is enough large, so that a voltage drop of the voltage VC is not much large. When a current is fed from thecapacitor 10 to thedischarge lamp 6 for a certain time period, the pulse signal of the Sig.3 is again turned on and the Sig.2 is made low and the DC-DC converter 2 is actuated and theFET 5 b is made in the OFF state and an electric charge is supplied from the DC-DC converter 2 to thedischarge lamp 6. This cycle is 200 Hz or more. This period is called an AC discharge period. By comparing the current output IL and the voltage output VL with the setting value of themicrocomputer 8, electric power control is performed, and theFET 2 b of the DC-DC converter 2 is controlled by the signal Sig.3 so as to hold the electric power 34 W speedily after entering the AC discharge period. - In the embodiment as described above, use of one FET will suffice in comparison with use of four FETs in the H bridge configuration of the conventional switching circuit, so that it is found that cost reduction and miniaturization can be achieved even in the case that the
capacitor 10 is added including a gate control circuit of each the FET. - Also, in the embodiment, timing of switching in the switching circuit part is controlled by detecting the voltage VC of the capacitor, so that a stable discharge emission can be obtained. That is, after the discharge lamp is lighted, it is controlled so as to heat the electrodes of the discharge lamp by the discharge lamp current until the voltage VC of the capacitor reaches a predetermined voltage, so that at the time of reversing a switching state, the voltage applied to the discharge lamp increases to a sufficient value and thereby the stable discharge emission can be obtained.
- Incidentally, in the embodiment shown in
FIG. 1 , a position of thecapacitor 10, theresistor 11 and thediode 12 provided in parallel with thecapacitor 10 is arranged in series with thedischarge lamp 6 in a circuit of connecting one input terminal (input terminal of the side of theFET 5 b) of theswitching circuit 5 to theigniter circuit 9, but the position may be arranged in series with thedischarge lamp 6 in a circuit of connecting the side of the output terminal of theswitching circuit 5, namely the output terminal of theswitching circuit 5 to theigniter circuit 9. -
FIG. 3 is a circuit configuration diagram showing a switching circuit part according to a second embodiment of the invention. A capacity value of acapacitor 10 for DC pulse to AC pulse conversion is in the order of 1/10 compared with the first embodiment. This is because thecapacitor 10 with the smaller capacity value is better when considering further miniaturization and cost reduction. In this second embodiment, a circuit configuration and a control method in the case of reducing the capacitor capacity will be described. - As shown in
FIG. 3 , the second embodiment differs from the first embodiment in a configuration of aswitching circuit 5. In the embodiment, aresistor 5 d is connected between a gate and a source of anFET 5 b, and avariable resistor 5 c is placed between a connection point between the gate of theFET 5 b and theresistor 5 d and an I/F 7. A gate voltage of theFET 5 b can be regulated by varying a resistance value of thevariable resistor 5 c. A current with a certain value or larger does not flow by throttling the gate voltage of theFET 5 b. Though the capacitor with a sufficiently large capacity is used in the first embodiment, this capacity value is small in the second embodiment of the invention, so that a voltage drop becomes large in case that a large current flows in a short time and a discharge runs out due to lack of a discharge voltage. The reason why such a circuit configuration is formed is because by regulating the gate voltage so that a current with 2.5 A or larger does not flow, the voltage drop generated during a period of passing a current from thecapacitor 10 for DC pulse to AC pulse conversion to adischarge lamp 6 is made as small as possible. - Incidentally, a
diode 12 for prevention of a reverse polarity voltage is connected in parallel with thecapacitor 10 for DC pulse to AC pulse conversion, but it goes without saying that thediode 12 is not necessary in case of using a capacitor with no polarity such as a film capacitor as thecapacitor 10. - Next, operations will be described.
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FIG. 4 shows signal waveforms of Sig.2, Sig.3 and output waveforms of voltages VL, VC and a discharge lamp current. A period different from the first embodiment is starts of an electrode heating period and an AC discharge period. A standby period is identical to the first embodiment. When the electrode heating period starts, a breakdown current and a discharge growth current flow in like manner. Then, thecapacitor 10 is charged through thedischarge lamp 6 by actuating a DC-DC converter 2. When the voltage VC of thecapacitor 10 reaches a voltage (the order of 140 V) preset in amicrocomputer 8, the actuation of the DC-DC converter 2 is stopped and theFET 5 b is turned on and a reverse directional current is passed through thedischarge lamp 6. An electric charge of thecapacitor 10 is discharged to thedischarge lamp 6 and the discharge lasts. Also at that time, a switch state is held until the voltage VC reaches the discharge voltage of the lamp (the VL−VC value stored in themicrocomputer 8 while theFET 5 b is turned off in the previous discharge cycle) by control of themicrocomputer 8. If a condition of VC=the discharge voltage of the lamp is satisfied, the DC-DC converter 2 is actuated and theFET 5 b is turned off and the electric charge is supplied from the DC-DC converter to thedischarge lamp 6 again and the discharge is lasted. Also at this time, the switch state is held until the voltage VC reaches 140 V. This cycle is repeated until an integral value of the discharge lamp current IL detected by ashunt resistor 4 reaches 60 mAs (60 mC). The reason why this cycle is repeated plural times during the electrode heating period is because the capacity value of thecapacitor 10 is small relative to the first embodiment, and this means that plural tomes are necessary to attain the total amount of electric charge to be applied to the discharge lamp for electrode heating to a defined value set by the microcomputer B. - Also, in the second embodiment, the gate voltage of the
FET 5 b is throttled and the current flowing in the case of turning on theFET 5 b is limited, so that the voltage drop of thecapacitor 10 is suppressed, and time for supplying a current from thecapacitor 10 to thedischarge lamp 6 can be made even though the capacity value of thecapacitor 10 is small in the order of 1/10 of that of the first embodiment. - After the electric charge amount of 60 mAs is supplied to the
discharge lamp 6, an operation proceeds to the AC discharge period. In the case that the DC-DC converter 2 is actuated and theFET 5 b is shifted in the OFF state, an operation proceeds to the AC discharge period when the voltage VL becomes equal to a value doubling the discharge voltage of the lamp stored in themicrocomputer 8 in the previous discharge cycle. In the case that the DC-DC converter 2 is stopped and theFET 5 b is shifted in the ON state, an operation proceeds to the AC discharge period when the voltage VC becomes equal to the discharge voltage of the lamp stored in themicrocomputer 8 in the previous discharge cycle. The AC discharge period is driven at 200 Hz or higher in a manner similar to the first embodiment, and thedischarge lamp 6 is lighted in an AC discharge by repeating a process of actuating the DC-DC converter 2 and turning off theFET 5 b and a process of stopping the DC-DC converter and turning on theFET 5 b in a manner similar to the electrode heating period. Electric power at the time of steady-state discharge is controlled at 34 W in like manner. - In the first and second embodiments shown in
FIGS. 1 and 3 , thecapacitor 2 d acting as voltage smoothing and a current source at the time of discharge start is placed in the DC-DC converter 2. In case of performing switching operation without idea, when theswitch FET 5 b is turned on, all the electric charges stored in thecapacitor 2 d at the time of actuating the DC-DC converter is consumed by ON resistance of theswitch FET 5 b and a large loss of electric power is caused. The loss of electric power in that case is estimated. A voltage applied to thedischarge lamp 6 at the actuation by 34 W in a steady state is about 85 V and for example, in case that an AC discharge is performed at a capacitor capacity value with 1 μF and 1 kHz, a loss P of electric power becomes the value P=(½)×(1 μF)×(85V×2)2×(1 kHz)=14.45 W. - In a third embodiment, switching is devised and it is formed so as to suppress this loss of electric power, and
FIG. 5 is a chart showing timing of a signal waveform during an AC discharge period of a discharge lamp lighting apparatus according to the third embodiment. In the AC discharge period, immediately before theFET 5 b at the time of switch shift is turned on, both the OFF periods (a dead period shown inFIG. 5 ) overlaying a stop period of the DC-DC converter on an OFF period of theFET 5 b are provided. The dead period of this switch is a period of supplying the electric charge stored in thecapacitor 2 d until a discharge lamp voltage becomes a value close to zero of the extent to which a discharge does not run out. For example, if a period in which a VL voltage of 170 V (85 V×2) becomes 100 V forward from 85 V which is a VC voltage is considered as the dead period and the conditions described above are used, a loss P′ of electric power can be reduced to the value P′=(½)×(1 μF)×(100V)2×(1 kHz)=5 W. -
FIG. 6 is a circuit configuration diagram of a discharge lamp lighting apparatus according to a fourth embodiment of the invention and is the discharge lamp lighting apparatus of a circuit configuration for reducing a loss of electric power other than the third embodiment described inFIG. 5 . - A
capacitor 102 d (second capacitor) is provided in a position in which thecapacitor 2 d within the DC-DC converter is placed and further, aresistor 102 f and adiode 102 g are connected in parallel and acapacitor 102 e (first capacitor) is connected in series, and thecapacitor 102 e, theresistor 102 f and thediode 102 g are connected in parallel with thecapacitor 102 d. A cathode of thediode 102 g is connected to a cathode of adiode 2 c and an anode is connected to thecapacitor 102 e. Operations are identical to that of the second embodiment. - Functions of the
capacitor 2 d having roles of voltage smoothing and a current supply source at the time of discharge start in the first to third embodiments are separated, and the role of the smoothing is shared in thecapacitor 102 d and the role of the current supply source at the time of discharge start is shared in thecapacitor 102 e. In the embodiment, a capacity value of thecapacitor 102 d is set to a value in which the loss of electric power does not become large too and the voltage smoothing can be performed to some extent, and a capacity value of thecapacitor 102 e is set to a value capable of supplying the current at the time of discharge start similar to thecapacitor 102 d of the first to third embodiments, and a resistance value of theresistor 102 f is set to a value made so that a time constant defined by the capacity value of thecapacitor 102 e becomes large sufficiently compared with a cycle of an AC discharge period. By forming such a circuit configuration, the loss of electric power in the case of turning on anFET 5 b can be reduced. Charge to thecapacitor 102 e is performed only for a standby period (sufficiently longer than the cycle of the AC discharge period) in which time is taken slow to 400 V. Since charge and discharge (with 200 Hz or higher) very faster than the standby period is performed in the AC discharge period, the charge is little performed due to the presence of theresistor 102 f, so that the loss of electric power becomes very small. Also, the capacity value of thecapacitor 102 d for smoothing is reduced to a small value, so that the loss of electric power due to this capacitor is small. For example, in case where an AC discharge frequency is 1 kHz and a discharge lamp discharge voltage is 85 V and an electric charge until a VL voltage becomes 100 V from 170 V is supplied to the discharge lamp and a capacity value of thecapacitor 102 d is 0.1 μF, a loss P of electric power due to thecapacitor 102 d becomes the value P=(½)×(0.1 μF)×(100V)2×(1 kHz)=0.5 W assuming that the stored electric charge is usefully used in a discharge lamp current as described above. Since a loss of electric power due to thecapacitor 102 e is close to zero, the loss can be controlled to 0.5 W. - Incidentally, in the fourth embodiment, when using a capacitor with a large capacity value as described in the first embodiment as a
capacitor 10, it goes without saying that thedischarge lamp 6 can be lighted without problems even in case of removingresistors FET 5 b and performing the operations as shown inFIG. 2 in a manner similar to the first embodiment. - Also, the case of providing the dead period is indicated in the embodiment, but there is the effect of reducing the loss of electric power even by the configuration of
FIG. 6 without providing the dead period. - In lighting of a discharge lamp, the discharge lamp may be grounded to make an applied voltage minus in order to avoid a diffusion of sodium ions to a tube wall (a loss of sodium). The lighting of such a discharge lamp can be implemented very easily in the first to fourth embodiments. The circuit configuration is indicated by way of example with reference to the fourth embodiment.
FIG. 7 shows a circuit configuration in the case of lighting adischarge lamp 6 by a minus pulse using a ground potential as a reference in the fourth embodiment. In the circuit configuration, plus is only shifted to minus. - In
FIG. 7 , points different from the fourth embodiment shown inFIG. 6 will be described. An output voltage of the high side of a DC-DC converter 2 is connected to aground 3, and anFET 5 b andresistors switching circuit 5 are placed to output of the high side of the DC-DC converter 2 and the low side is connected to an output terminal of theswitching circuit 5. Since an output pulse of theswitching circuit 5 is a minus voltage pulse using a ground as a reference, a direction of adiode 12 connected in parallel with acapacitor 10 for DC pulse to AC pulse conversion is a reverse direction. Output voltages VL, VC only become a minus direction, and a discharge lamp current and input signals Sig.2, Sig.3 are similar to the waveforms shown inFIGS. 4 and 5 . Thus, operations are identical to that of the fourth embodiment. -
FIG. 8 is a circuit configuration diagram of a discharge lamp lighting apparatus according to a sixth embodiment of the invention. - While an output voltage of the DC-
DC converter 2 of the first to fifth embodiments is only two levels of voltage with high and low such as a positive or negative voltage value and a ground, it is constructed so that ternary values with high, low and their center level such as positive and negative binary voltage values and a ground voltage can be outputted in the sixth embodiment. Thus, the sixth embodiment differs from the embodiments described above in a configuration of the DC-DC converter 2. The need for a capacitor for DC pulse to AC pulse conversion is also eliminated. - In the circuit configuration shown in
FIG. 8 , anigniter circuit 9, adischarge lamp 6, aDC power source 1, an I/F 7, amicrocomputer 8 and ashunt resistor 4 are identical to that of the first to fifth embodiments. A configuration of aswitching circuit 5 is a half bridge circuit comprising two switching elements having anFET 5 a (first switching element) and anFET 5 b (second switching element), and signals Sig.1 and Sig.2 from the microcomputer are inputted to gates of theFETs FET 5 a using a ground as a reference and a low voltage VK is supplied to a source of theFET 5 b using the ground as the reference. An output terminal of theswitching circuit 5 is connected to one electrode of thedischarge lamp 6, and the other electrode of thedischarge lamp 6 is connected to aground 3 through apulse transformer 9 a of theigniter circuit 9 and theshunt resistor 4, and it is formed so that the other electrode becomes a center voltage level of the high voltage VH and the low voltage VK. - A
transformer 202 a of the DC-DC converter 2 is formed of a primary winding, a secondary winding and a tertiary winding unlike the first to fifth embodiments. An anode of adiode 2 c is connected to one side of the secondary winding for outputting a high voltage and theground 3 is connected to the other side of the secondary winding. A cathode of thediode 2 c is connected to the drain of theFET 5 a and acapacitor 2 d functioning as voltage smoothing and a current supply source at the time of discharge start, and the other side of thecapacitor 2 d is connected to theground 3. Also, an anode of adiode 202 h is connected to one side of the tertiary winding for outputting a voltage of the low side of thetransformer 202 a and the source of theFET 5 b is connected to the other side of the tertiary winding. A cathode of thediode 202 h is connected to theground 3 and acapacitor 202 i functioning as voltage smoothing, and the other side of thecapacitor 202 i is connected to the source of theFET 5 b. In the sixth embodiment, a voltage VH of the high side, a voltage VK of the low side and a discharge lamp current IL are detected and comparison processing is performed by themicrocomputer 8 and thereby, lighting of thedischarge lamp 6 is controlled. - Next, operations will be described.
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FIG. 9 shows gate input waveforms of theFETs FET 5 a is in the ON state and theFET 5 b is in the OFF state, acapacitor 9 b within theigniter circuit 9 is also charged to 400 V and agap switch 9 c conducts and a pulse voltage of about 20 kV is applied across thedischarge lamp 6 to start discharge. When the discharge is started, a breakdown current flows through thedischarge lamp 6, and electric charges equivalent to 400 V stored in thecapacitor 2 d are supplied to thedischarge lamp 6 as a current at the time of discharge start. - During an electrode heating period, a switching state holds a state of the standby period and a one-way current continues to be supplied to the
discharge lamp 6. When the amount of flowing electric charge reaches 30 mC by detecting the current IL, theFET 5 a is made in the OFF state and theFET 5 b is made in the ON state, and a reverse directional current is passed through thedischarge lamp 6. Also, when the amount of flowing electric charge reaches 30 mC, an operation proceeds to an AC discharge period. - During the AC discharge period, lighting of the
discharge lamp 6 is controlled by AC drive of 200 Hz to 20 kHz. The absolute value of output voltages of the secondary winding and the tertiary winding of thetransformer 202 a in that case is 40 V to 90 V. In a steady state, the electric power, of 34 W is maintained as described above. - The merit of the sixth embodiment is that two FETs will suffice relative to use of four FETs in the conventional switching circuit. Also, the need for the capacitor for DC pulse to AC pulse conversion used in the first to fifth embodiments is eliminated. Thus, there are merits in miniaturization and cost reduction.
- In the sixth embodiment, during the standby period as shown in
FIG. 9 , a voltage of a maximum of 800 V is applied between the drain and the source of theFET 5 b. Since high withstand voltage parts are large in size and are high cost, the merits in miniaturization and cost reduction is obtained even if adding another switch in case that an applied voltage can be reduced. -
FIG. 10 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a seventh embodiment of the invention. The seventh embodiment differs from the sixth embodiment only in that anFET 302 j is placed between the tertiary winding of thetransformer 202 a and theFET 5 b. A signal Sig.4 from amicrocomputer 8 is inputted to a gate of theFET 302 j. - Next, operations will be described.
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FIG. 11 shows FET gate input waveform operations Sig.1, Sig.2, Sig.3, Sig.4 and output waveform voltages VH, VK and a discharge lamp current waveform. The seventh embodiment differs from the sixth embodiment (FIG. 9 ) only in a standby period, and during the standby period, the voltage VK is zero since theFET 302 j is made in the OFF state. By making theFET 302 j in the OFF state during the standby period, the voltage applied to theFET 5 b becomes a maximum of 400 V, so that a switching element with a withstand voltage lower than that of the switching element used in the sixth embodiment can be used, with the result that miniaturization and cost reduction can be achieved. -
FIG. 12 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to an eighth embodiment of the invention, and a problem of applying the voltage of a maximum of 800 V to theFET 5 b of the sixth embodiment is solved without adding a switch in a manner similar to the seventh embodiment. - The eighth embodiment is similar to the sixth and seventh embodiments except for a DC-
DC converter 2. - The eighth embodiment differs from the sixth embodiment in that a transformer having a primary winding, a secondary winding and a tertiary winding is replaced with two
transformers capacitor 202 i in the DC-DC converter 2. A resistor or a Zener diode is considered as the clamping element 402 l. In the embodiment, the Zener diode with 150 V is used as the clamping element 402 l. - Next, operations will be described.
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FIG. 13 shows FET gate input waveforms Sig.1, Sig.2, Sig.3 and output voltage waveforms VH, VK and a discharge lamp current waveform. The eighth embodiment differs from the sixth embodiment (FIG. 9 ) in a period during which theFET 5 b is turned on (a standby period and the first half of an electrode heating period), and during the period, the clamping element 402 l acts and the voltage VK is kept at −150 V. Thus, a voltage of a maximum of 550 V is applied to theFET 5 b and it is found that a switching element with a withstand voltage lower than that of the sixth embodiment can be used. -
FIG. 14 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a ninth embodiment of the invention. The ninth embodiment is similar to the eighth embodiment except for a transformer of a DC-DC converter 2. Atransformer 502 a has an integral structure as shown inFIG. 15 .Numeral 601 is a core, andnumerals - Next, operations will be described.
- Input and output waveforms are similar to that of the eighth embodiment shown in
FIG. 13 and the operations are also similar. - In the sixth to ninth embodiments, the transformer structure is complicated or withstand voltage property of the FET element is required, but the number of switching elements is decreased to two in comparison with the need of four switching elements in the conventional switching circuit, so that there are merits in miniaturization and cost reduction.
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FIG. 16 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to a tenth embodiment of the invention. In the first to ninth embodiments, the number of FETs forming theswitching circuit 5 is decreased, but in the tenth embodiment, a withstand voltage of each the element is reduced to achieve miniaturization and cost reduction while the number of FETs is four equal to the conventional type. - A
discharge lamp 6, anigniter circuit 9, ashunt resistor 4 and an I/F 7 are identical to that of the first to ninth embodiments. In amicrocomputer 8, the number of FETs to be controlled increases, so that five signals Sig.1 to Sig.5 are outputted. - A
transformer 702 a of a DC-DC converter 2 comprises three windings of one input and two outputs. In a primary winding, a current is passed by anFET 2 b in a manner similar to the first to ninth embodiments. One side of a secondary winding is connected to an anode of adiode 2 c and the other side of the secondary winding is connected to a source of an FET 5 f of aswitching circuit 5. A voltage of the source of this FET 5 f is a voltage VL to be detected. A cathode of thediode 2 c is connected to acapacitor 2 d for voltage smoothing and also is connected to an anode of a diode 5 i of theswitching circuit 5 through theshunt resistor 4 and is connected to aground 3. A current IL is detected by theshunt resistor 4. Also, one side of a tertiary winding is connected to an anode of adiode 702 m and the other side of the tertiary winding is connected to the side of apulse transformer 9 a of an output terminal of theswitching circuit 5. Acapacitor 702 n for voltage smoothing is connected between thediode 702 m and the tertiary winding, and a cathode of thediode 702 m is connected to the other output terminal of theswitching circuit 5 through a resistor 702 o. The winding ratio of the secondary winding to the tertiary winding of thetransformer 702 a is 1:4, and the tertiary windingoutputs 400 V when the secondary winding outputs −100 V. Since only a function of the voltage smoothing is required, thecapacitors - The
switching circuit 5 is a H bridge circuit similar to the conventional example. AnFET 5 a and an FET Se act to shift a high voltage, and anFET 5 b and the FET 5 f act to shift a low voltage. A cathode of the diode 5 i is connected to a drain of theFET 5 a and a cathode of the diode 5 j is connected to a drain of the FET 5 f. Also, a resistor 5 g of 100 kΩ is connected in parallel with theFET 5 b and aresistor 5 h of 100 kΩ is connected in parallel with theFET 5 e. A connection point between a source of theFET 5 a and a drain of theFET 5 b becomes the output terminal of theswitching circuit 5 and is connected to one electrode of thedischarge lamp 6. Also, a connection point between a source of theFET 5 e and an anode of the diode 5 j becomes the other output terminal and is connected to the primary winding of thepulse transformer 9 a. - A
capacitor 13 is connected between the output terminals of theswitching circuit 5. This acts as initial current supply means for supplying a current to the discharge lamp at the time of discharge start. In this embodiment, thecapacitor 13 has 1 μF. In the tenth embodiment thus, a current supply source (capacitor 13) at the time of discharge start is placed in the output terminals of theswitching circuit 5, and charge to 400 V of thecapacitor 13 and acapacitor 9 b during a standby period is performed using the tertiary winding of thetransformer 702 a. - Next, operations will be described.
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FIG. 17 shows gate input signal waveforms Sig.1 to Sig.5 and a voltage of thecapacitor 13 and a voltage waveform of VL and a discharge lamp current waveform. During a standby period, Sig.1, Sig.2, Sig.4 and Sig.5 are in the OFF state and only the DC-DC converter is controlled by pulse width control. In this case, the voltage VL is controlled at 150 V and the voltages of thecapacitor 13 and thecapacitor 9 b are increased to 400 V. In this case, only a voltage of a maximum of 275 V is applied between the drain and the source of theFETs - When the voltage reaches 400 V, a
gap switch 9 c conducts and a pulse voltage of about 20 kV is applied to thedischarge lamp 6 to start discharge. When the discharge is started, a breakdown current flows through thedischarge lamp 6, and electric charges stored in thecapacitor 13 are supplied to thedischarge lamp 6 as a current at the time of discharge start. - When the breakdown is detected by a current IL, the
FET 5 a and the FET 5 f are made in the ON state and theFET 5 b and the FET Se are made in the OFF state, and a current continues to be passed in a certain direction by the DC-DC converter 2 (electrode heating period). When the amount of mobile electric charge (integral value of the current IL) reaches 30 mC, theFET 5 a and the FET 5 f are made in the OFF state and theFET 5 b and theFET 5 e are made in the ON state, and a current continues to be passed in a reverse direction. Also in this direction, when the amount of electric charge of 30 mC is supplied, an operation proceeds to an AC discharge period During the AC discharge period, an AC current of 200 Hz to 20 kHz is passed through thedischarge lamp 6 and lighting is maintained. The electric power at the time of steady discharge is controlled at 34 W. - The amount of electric charge charged and discharged to the
capacitor 13 during the AC discharge period is uselessly consumed due to ON resistance of the FET (loss of electric power). In order to reduce this, the method described in the third embodiment is also used in the tenth embodiment. In the embodiment, the electric charge stored in thecapacitor 13 is supplied to thedischarge lamp 6 and then the switch is shifted. That is, a dead period of the switch is provided in the ON-OFF shift of theFETs 5 a, 5 f and theFETs - In the tenth embodiment, the number of FETs forming the
switching circuit 5 is four equal to the conventional type, but only the voltage of a maximum of 275 V is applied to each the element, so that the FET used in the conventional type can be replaced with a low withstand voltage element. The low withstand voltage element is cheap compared with a high withstand voltage element, so that cost reduction can be achieved. - Incidentally, a type in which the
discharge lamp 6 has theigniter circuit 9 is shown in each the embodiment, but theigniter circuit 9 may be eliminated. - As described above, according to a first configuration of the invention, a discharge lamp lighting apparatus comprises electric power regulating means for regulating electric power supplied from a power source and outputting voltages having respective different potentials from two wirings, a switching circuit part formed of one switching element in which input terminals are connected to the two wirings of the electric power regulating means and also one input terminal of the input terminals is connected to one electrode of a discharge lamp and an output terminal is connected to the other electrode of the discharge lamp, and a capacitor connected in series with the discharge lamp in a circuit for making connections of one input terminal of the switching circuit part, the discharge lamp and the output terminal of the switching circuit part, so that one switching element forming the switching circuit part will suffice and thereby, cost reduction and miniaturization can be achieved.
- Also, according to a second configuration of the invention, in the first configuration, the discharge lamp is driven with alternating current by repeating a process of supplying a current from the electric power regulating means to the discharge lamp and performing charge to the capacitor and a process of stopping actuation of the electric power regulating means and supplying a reverse directional current from the capacitor to the discharge lamp, so that the discharge lamp can be driven with alternating current even when the number of switching elements forming the switching circuit part is small and thereby, the cost reduction and miniaturization of the discharge lamp lighting apparatus can be achieved.
- Also, according to a third configuration of the invention, in the first or second configuration, a standby period for making preparations for lighting, an electrode heating period for detecting at least a voltage VC of the capacitor to heat the electrodes of the discharge lamp by a discharge lamp current until the voltage VC reaches a predetermined voltage after the discharge lamp is lighted, and an AC discharge period for passing an AC current through the discharge lamp to sustain discharge are provided, so that a stable discharge emission without lighting failure can be obtained.
- Also, according to a fourth configuration of the invention, in one of the first to third configurations, one input terminal of the switching circuit part is connected to the output terminal through the switching element and the other input terminal of the switching circuit part is directly connected to the output terminal, so that one switching element forming the switching circuit part will suffice and thereby, the cost reduction and miniaturization can be achieved.
- Also, according to a fifth configuration of the invention, in one of the first to fourth configurations, the switching element comprises means for regulating a control voltage so that a discharge lamp current becomes a predetermined value, so that the maximum discharge current value can be reduced and even in case of using a capacitor with the small capacity value, a voltage drop is small and thereby, the capacitor can also be miniaturized in addition to an increase in stability of lighting.
- Also, according to a sixth configuration of the invention, in one of the first to fifth configurations, voltage smoothing and initial current supply means for smoothing a voltage outputted by the electric power regulating means and supplying a current to the discharge lamp at the time of discharge start is provided, so that there is the effect of stably sustaining discharge.
- Also, according to a seventh configuration of the invention, in the sixth configuration, a dead period overlaying a period of stopping actuation of the electric power regulating means on an OFF period of the switching element is provided when performing AC drive of the discharge lamp, so that an electric charge stored in the capacitor used as the voltage smoothing and initial current supply means can be usefully utilized for discharge and thereby, reactive power can be reduced.
- Also, according to an eighth configuration of the invention, in the sixth configuration, the voltage smoothing and initial current supply means is formed by placing a second capacitor in parallel with a circuit in which a parallel circuit of a resistor and a diode is connected in series with a first capacitor, so that the amount of electric charge necessary for the discharge start can be stored to the first capacitor during the standby period, and charge and discharge to the first capacitor becomes very small due to the high repetitive frequency during the AC discharge period, with the result that a loss of electric power during the AC discharge period can be reduced while ensuring the current necessary at the time of the discharge start.
- Also, according to a ninth configuration of the invention, a discharge lamp lighting apparatus comprises electric power regulating means for regulating electric power supplied from a power source and outputting positive and negative binary voltages from two wirings, and a switching circuit part formed of first and second switching elements for controlling connections between the two wirings of the electric power regulating means and one electrode of a discharge lamp, and it is constructed so that the other electrode of the discharge lamp becomes a center voltage level of the positive and negative binary voltages, so that two switching elements forming the switching circuit part will suffice and thereby, the cost reduction and miniaturization can be achieved.
- Also, according to a tenth configuration of the invention, in the ninth configuration, a third switching element is placed between one wiring of the two wirings of the electric power regulating means and the switching circuit part, and the third switching element is made in the OFF state during a standby period for making preparations for lighting, so that a voltage applied to the switching elements forming the switching circuit part becomes lower than that of a type without providing the third switching element, with the result that a switching element with low withstand voltage can be used to achieve the cost reduction and miniaturization.
- Also, according to an eleventh configuration of the invention, in the ninth configuration, the electric power regulating means has three terminals for outputting a positive voltage, a ground voltage and a negative voltage, and a voltage clamping element is connected between a ground terminal for outputting the ground voltage and a voltage terminal for outputting the positive or negative voltage, so that a voltage applied to the switching elements forming the switching circuit part becomes lower than that of a type without providing the voltage clamping element, with the result that a switching element with low withstand voltage can be used to achieve the cost reduction and miniaturization.
- Also, according to a twelfth configuration of the invention, in the eleventh configuration, three voltage levels consisting of the positive voltage, the ground voltage and the negative voltage are formed by using two transformers, so that one voltage can be kept constant while the other voltage can be increased to a predetermined voltage during the standby period.
- Also, according to a thirteenth configuration of the invention, in the eleventh configuration, three voltage levels consisting of the positive voltage, the ground voltage and the negative voltage are formed by using an integral transformer in which a primary winding and a secondary winding are placed in one end of a core and another primary winding and a tertiary winding are placed in the other end, so that one voltage can be kept constant while the other voltage can be increased to a predetermined voltage during the standby period.
- Also, according to a fourteenth configuration of the invention, a discharge lamp lighting apparatus comprises electric power regulating means for regulating electric power supplied from a power source and outputting voltages having respective different potentials from four wirings, a switching circuit part formed of four switching elements for controlling connections between the two wirings of the four wirings of the electric power regulating means and electrodes of a discharge lamp, and a capacitor which is connected between output terminals of the switching circuit part and supplies a current to the discharge lamp at the time of discharge start, and the residual two wirings of the four wirings of the electric power regulating means are connected to respective electrodes of the capacitor and the four switching elements are made in the OFF state during a standby period for making preparations for lighting, so that the maximum voltage applied to the switching elements can be reduced, with the result that a switching element with a withstand voltage lower than that of a conventional type can be used to achieve the cost reduction.
- Also, according to a fifteenth configuration of the invention, in one of the first to fourteenth configurations, the discharge lamp has an igniter circuits so that there is the effect of stably starting discharge.
Claims (11)
1. A discharge lamp lighting apparatus comprising:
electric power regulating means for regulating electric power supplied from a power source and outputting voltages having respective different potentials at first and second wirings,
a switching circuit including a switching element having first and second input terminals connected to the first and second wirings of said electric power regulating means, said first input terminal being connected to a first electrode of a discharge lamp, and an output terminal being connected to a second electrode of the discharge lamp, and
a first capacitor connected in series with the discharge lamp in a circuit for making connections to one of said first input terminal of said switching circuit, the discharge lamp, and said output terminal of said switching circuit.
2. The discharge lamp lighting apparatus as defined in claim 1 , wherein the discharge lamp is driven with alternating current by repeatedly supplying a current from said electric power regulating means to the discharge lamp and charging said capacitor, and by stopping actuation of said electric power regulating means and supplying a reverse direction current from said first capacitor to the discharge lamp.
3. The discharge lamp lighting apparatus as defined in claim 1 , wherein the discharge lamp is operative in periods including
a standby period preparing for lighting of the discharge lamp,
an electrode heating period for detecting at least a voltage of said capacitor for heating electrodes of the discharge lamp with a discharge lamp current until the voltage reaches a threshold voltage after the discharge lamp is lighted, and
an AC discharge period for passing an AC current through the discharge lamp to sustain a discharge in the discharge lamp.
4. The discharge lamp lighting apparatus as defined in claim 1 , wherein
one of said first and second input terminals of said switching circuit is connected to said output terminal through said switching element, and
the other of said first and second input terminals of said switching circuit is directly connected to said output terminal.
5. The discharge lamp lighting apparatus as defined in claim 1 , wherein said switching element comprises means for regulating a control voltage so that a discharge lamp current becomes a fixed current.
6. The discharge lamp lighting apparatus as defined in claim 1 , including voltage smoothing and initial current supply means for smoothing a voltage output by said electric power regulating means and supplying a current to the discharge lamp upon starting of a discharge.
7. The discharge lamp lighting apparatus as defined in claim 1 , wherein operation of the discharge lamp includes a dead period overlaying a period of stopping actuation of said electric power regulating means in an OFF period of said switching element when driving the discharge lamp with AC.
8. The discharge lamp lighting apparatus as defined in claim 1 , wherein said voltage smoothing and initial current supply means includes
a resistor and a diode connected in parallel in a parallel circuit, said parallel circuit being connected in series with said first capacitor, and
a second capacitor connected in parallel with said parallel circuit.
9-14. (canceled)
15. The discharge lamp lighting apparatus as defined in claim 1 , including an igniter circuit.
16-17. (canceled)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US11/953,951 US20080106220A1 (en) | 2000-05-24 | 2007-12-11 | Discharge lamp lighting apparatus |
Applications Claiming Priority (4)
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JP2000-153072 | 2000-05-24 | ||
JP2000153072 | 2000-05-24 | ||
US09/729,089 US7327095B2 (en) | 2000-05-24 | 2000-12-05 | Discharge lamp lighting apparatus |
US11/953,951 US20080106220A1 (en) | 2000-05-24 | 2007-12-11 | Discharge lamp lighting apparatus |
Related Parent Applications (1)
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US09/729,089 Division US7327095B2 (en) | 2000-05-24 | 2000-12-05 | Discharge lamp lighting apparatus |
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US20080106220A1 true US20080106220A1 (en) | 2008-05-08 |
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US09/729,089 Expired - Fee Related US7327095B2 (en) | 2000-05-24 | 2000-12-05 | Discharge lamp lighting apparatus |
US11/953,951 Abandoned US20080106220A1 (en) | 2000-05-24 | 2007-12-11 | Discharge lamp lighting apparatus |
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US09/729,089 Expired - Fee Related US7327095B2 (en) | 2000-05-24 | 2000-12-05 | Discharge lamp lighting apparatus |
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US (2) | US7327095B2 (en) |
KR (1) | KR100380506B1 (en) |
DE (1) | DE10064039B4 (en) |
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Also Published As
Publication number | Publication date |
---|---|
US7327095B2 (en) | 2008-02-05 |
DE10064039A1 (en) | 2001-12-20 |
KR100380506B1 (en) | 2003-04-18 |
US20060061299A1 (en) | 2006-03-23 |
KR20010107517A (en) | 2001-12-07 |
DE10064039B4 (en) | 2007-08-30 |
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Legal Events
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STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |