JP2007179869A - Discharge lamp lighting circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting circuit attaining secure lighting properties of a discharge lamp at start capable of synchronizing frequency of a cyclic voltage application means even in the case where the resonance circuit varies in resonance frequency and restarting a resonance assist at a high speed even in the case where return to glow discharge from arc discharge or dying-out occurs, in the discharge lamp lighting circuit for lighting a high voltage discharge lamp especially a high intensity discharge lamp such as a high-pressure mercury lamp, a metal halide lamp and a xenon lamp. <P>SOLUTION: In a start sequence of the discharge lamp Ld of the discharge lamp lighting circuit, a frequency control circuit Uf conducts a sweep action to change a frequency control signal Sf starting from either an upper limit frequency or a lower limit frequency of a frequency variable oscillator Vco in a range not exceeding the frequency of the other limit. After the sweep action, the frequency control circuit Uf determines a value of frequency control signal Sf and inputs it to the frequency variable oscillator Vco. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting circuit for lighting a high-intensity discharge lamp, particularly a high-intensity discharge lamp such as a high-pressure mercury lamp, a metal halide lamp, or a xenon lamp.

  For example, a high-intensity discharge lamp (HID lamp) is used in a light source device for an optical device for image display such as a liquid crystal projector or a DLP (TM) projector. In the projector described above, the three primary colors R, G, and B are separated by a dichroic prism or the like, an image for each primary color is generated by a spatial modulation element provided for each color, and the optical path is recombined by the dichroic prism or the like. Some systems display color images. On the other hand, a color filter having three primary colors of R, G, and B is rotated, and light from the light source is passed through the filter to sequentially generate light beams of the three primary colors. There is also a method of displaying a color image by sequentially generating images for each of the three primary colors by time division by controlling.

  When starting this type of lamp, a high voltage is applied to the lamp in a state in which a voltage called a no-load open circuit voltage is applied to cause a dielectric breakdown in the discharge space, and a glow discharge is performed to shift to an arc discharge. As a method of applying a high voltage to the lamp, a method of superimposing a high voltage on an electrode for main discharge using an igniter, that is, in addition to the series trigger method, an auxiliary electrode other than the electrode for main discharge is provided in the discharge space. There is a method of applying a high voltage to the auxiliary electrode, that is, an external trigger method. The external trigger method has various advantages over the serial trigger method. Especially when the high voltage generation unit including the high voltage transformer is separated from the power supply circuit unit and installed in the vicinity of the discharge lamp, the discharge lamp lighting circuit Advantages that are advantageous for reducing the size and weight, reducing noise, improving safety, and reducing costs can be maximized.

  On the other hand, as a driving method of the discharge lamp during steady lighting, there are a direct current driving method and an alternating current driving method in which an inverter is further provided to perform periodic polarity inversion. In the case of the direct current drive system, the luminous flux from the lamp is also direct current, that is, does not change with time, so that there is basically a great advantage that it can be applied in exactly the same manner in both systems of the projector described above. . On the other hand, in the case of the AC driving method, there is an advantage that there is a possibility that the consumption and growth of the electrodes of the discharge lamp may be controlled by utilizing the degree of freedom that the polarity inversion frequency does not have in the DC driving method. As will be described later, there is a disadvantage caused by the existence of polarity reversal.

  In order to ensure reliable lighting performance of the discharge lamp at the start, no load is applied to the lamp when dielectric breakdown occurs in the discharge space by applying a high voltage by the above-described series trigger method or external trigger method. It is known that increasing the open-circuit voltage is effective. In order to achieve this in the case of the AC drive system, a series resonant circuit comprising a resonant inductor and a resonant capacitor is provided after the inverter, and the inverter is set in series so that the polarity frequency of the inverter matches the resonant frequency of the resonant circuit. 2. Description of the Related Art Conventionally, resonance assist is performed by a series resonance method that generates a resonance phenomenon and increases a voltage applied to a lamp.

  FIG. 22 is a diagram for explaining the principle of resonance assist by conventional series resonance. The discharge lamp lighting circuit in this figure includes a power supply circuit (Ux ′) for supplying power to the discharge lamp (Ld) and switch elements (Q1 ′, Q2 ′, Q3 ′, Q4 ′) for reversing the polarity of the output voltage. A full-bridge inverter (Ui ′), a resonance coil (Lr), a resonance capacitor (Cr), and a starter circuit (Ut ″), and at the start, the inverter (Ui ′) is connected to the resonance coil. Polarity inversion drive is performed at a resonance frequency determined by the product of the inductance of (Lr) and the capacitance of the resonance capacitor (Cr) or a frequency close thereto, and both ends of the resonance capacitor (Cr) are caused by an LC series resonance phenomenon caused thereby. A high voltage is generated between the elements, and a high voltage is applied to the discharge lamp (Ld) together with the starter circuit (Ut ″) connected in parallel to this portion. It is intended to pressure.

  By the way, in the case of the AC driving method, every time the polarity is inverted for AC driving, fluctuations such as instantaneous interruption, overshoot, and vibration of the light flux from the lamp are included. When trying to apply to an image, the difference between the timing at which images are sequentially generated by time division and the polarity inversion timing of AC drive of the lamp, that is, fluctuations appear in the displayed image at the beat frequency, and depending on the beat frequency, Since there is a problem that it becomes annoying, it is necessary to devise measures such as synchronizing the polarity inversion timing of the inverter with respect to the rotation of the color filter, and there is a disadvantage that the discharge lamp lighting circuit becomes complicated.

  Furthermore, in the DLP projector, the luminance for each color of each pixel of the display image is controlled by the duty cycle ratio of the operation of each pixel of the spatial modulation element. Even when taking a long time, if the fluctuation period such as the overshoot or vibration of the light beam at the time of polarity reversal is long, it is devised not to use the light of that period, or each pixel of the spatial modulation element so as to cancel the fluctuation. It is necessary to devise to control the operation. In the case of the former device, there is a drawback that the effective use efficiency of light is lowered, and in the case of the latter device, there is a defect that the control of the spatial modulation element in the projector device becomes very complicated.

  However, the presence of the resonant inductor of the series resonant circuit provided in the subsequent stage of the inverter tends to further promote the disadvantages of these AC drive systems. In order to prevent excessive resonance current flowing through the inverter as a periodic voltage application means when series resonance occurs, it is necessary to reduce the capacitance of the resonance capacitor and increase the inductance of the resonance inductor. This is because the larger the inductance is, the more easily the instantaneous interruption, overshoot, and vibration of the lamp light beam described above occur.

  As a resonance assist that avoids this problem, a primary side winding of a transformer having a secondary side winding with a small inductance is used as a resonance inductor, and this and a resonance capacitor constitute a parallel resonance circuit, which is generated by this parallel resonance circuit. There is a parallel resonant transformer system in which a high voltage is applied to the lamp via the secondary winding of the resonant transformer. In the case of this method, since the inductance of the secondary winding of the resonant transformer is small as described above, it is possible to make it difficult to cause the instantaneous interruption, overshoot, and vibration of the lamp luminous flux. However, in this method, since the inductance of the primary winding of the resonance transformer is also small, the resonance current tends to increase. However, because of the parallel resonance, the current of the periodic voltage applying means for driving the resonance is kept small. be able to. This parallel resonant transformer method can also be applied to a DC drive method.

  In any of the series resonance system and the parallel resonance transformer system described above, in order to obtain a sufficient increase in the voltage applied to the lamp, the frequency of the periodic voltage application means or the frequency of its harmonic component is set to the resonance circuit. It is necessary to set so as to match, that is, to tune to the resonance frequency. However, there are variations in parts, and the influence of the length of the cable to be connected and the degree of proximity between the cable and other conductors is added, so it is difficult to set the resonance frequency strictly in advance. There's a problem. In order to solve this problem, various techniques have been proposed for lighting devices for high-frequency discharge lamps and low-pressure discharge lamps as well as high-intensity discharge lamps.

  In Japanese Patent Laid-Open No. 02-215091, the condition that the drive frequency matches the resonance frequency is generated at least for a moment. The automatic sweep is described.

  Japanese Patent Laid-Open No. 03-102798 includes high frequency means for applying a high voltage to the lamp so that the lamp ignites in the LC circuit, and the high frequency means is a frequency that changes with time or higher than the resonance frequency. What is applied to the LC circuit at a frequency that decreases with time from the frequency is described.

  Further, in Japanese Patent Laid-Open No. 04-017296, when changing the oscillation frequency of the inverter means to a high frequency, the oscillation frequency is changed within a predetermined range in accordance with the output voltage of the sawtooth wave generation means or the triangular wave generation means. The constituents are described.

  Furthermore, in Japanese Patent Laid-Open No. 04-272695, at the time of starting, the inverter is controlled so that the output frequency of the inverter continuously changes from the resonance frequency of the LC circuit to a frequency below the frequency region where the acoustic resonance phenomenon can occur. Or the one that controls the inverter so that the frequency is lower than the frequency region where the acoustic resonance phenomenon can occur in a steady state.

  Further, in Japanese Patent Application Laid-Open No. 04-272698, when starting or restarting a discharge lamp, a rectangular wave is formed between the fundamental resonance frequency associated with the impedance value of the resonance circuit and the resonance frequency due to its harmonics. In this example, the waveform is alternately changed or swept in a sine wave form.

  Further, Japanese Patent Application Laid-Open No. 10-284265 discloses that the frequency of the AC voltage output from the output connection portion in the start period is swept within a range including the resonance frequency of the resonance circuit, or the high frequency AC voltage is output and connected in the start period. Output from the unit and supplies only a low-frequency AC operating voltage to the discharge lamp during a steady lighting period after the start of the discharge lamp.

  Further, Japanese Patent Laid-Open No. 2003-257687 discloses that a high-pressure discharge lamp is operated at a high frequency. During steady lighting, the control circuit sets the output frequency of the high-frequency power supply circuit to a non-resonant frequency band of the high-pressure discharge lamp. In this frequency band, it is repeatedly changed up and down.

  Furthermore, Japanese Patent Application Laid-Open No. 2005-038813 describes one that changes the frequency of the high-frequency switching operation at the time of start-up continuously or in multiple stages.

  Furthermore, Japanese Patent Application Laid-Open No. 2005-050661 describes one in which the switching frequency is continuously changed in the vicinity of the resonance frequency of the first resonance circuit.

  In order to maintain the resonance state in a self-excited manner, Japanese Patent Application Laid-Open No. 55-148393 discloses that when the rate of change of the current flowing through the resonance circuit is maximum or close to the maximum when the gas-containing discharge lamp is started, It describes what allows the inverter to be kept at the resonant frequency of the resonant circuit by commutating the applied voltage.

  Japanese Patent Application Laid-Open No. 52-121975 discloses that an inverter searches for a resonance frequency and operates at that frequency before the lamp is turned on, as the operation frequency is swept and the operation frequency is fixed when the resonance condition is detected. What to do is described.

  Japanese Patent Application Laid-Open No. 2004-127656 gradually increases the frequency of the output voltage after starting the frequency of the output voltage of the inverter circuit at a frequency lower than the resonance frequency of the resonance circuit in order to light the discharge lamp. Alternatively, the frequency of the output voltage of the inverter circuit is set to the frequency of the output voltage when the amplitude of the oscillating voltage of the resonant circuit exceeds a predetermined value, or the resonance voltage is resonated within a predetermined time. If the amplitude of the output voltage of the circuit does not exceed the predetermined value, after the frequency of the output voltage reaches the upper limit, the initial frequency, which is the frequency at startup, is targeted at the same speed as when the frequency is increased. In the process of lowering the frequency, if the amplitude of the output voltage of the resonant circuit exceeds a predetermined value, the frequency is set to a frequency several percent lower than the current frequency, In the process of lowering, when the amplitude of the output voltage of the resonance circuit does not exceed the predetermined value and reaches the initial frequency, the operation of increasing the frequency again is turned on until the predetermined maximum time elapses. , What is repeated is described.

  Furthermore, in Japanese Patent Application Laid-Open No. 2004-327117, the operating frequency of the high-frequency voltage generated in the inverter circuit unit is set in the vicinity of the resonance frequency of the resonance circuit or an odd multiple thereof so that a high-voltage pulse can be output. The frequency sweep is performed so that the pulse can be output substantially constant, and the resonant boost voltage is detected. When the target voltage value is reached, the resonant boost voltage is stopped, or the operating frequency is fixed and the target voltage value is maintained for a certain period. The output continues at the target voltage value, or when the operating frequency is swept in the opposite direction to the previous sweep direction and the output continues for a certain period of time below the target voltage value, or the resonance voltage The detection means is constituted by a secondary winding of the inductance of the resonance circuit, or the resonance voltage detection means is connected to both ends of the capacitance of the resonance circuit. Those constituted by voltage dividing resistors, or have been described which control a control of the frequency sweep by the microcomputer.

  Japanese Patent Application Laid-Open No. 2005-071842 has a plurality of resonance circuits for generating a starting voltage, and outputs the resonance circuit or control circuit when it is lit. There is described a means for holding a signal and generating a starting voltage by an output signal of the resonance circuit or control circuit immediately after the power is turned on next time.

  Japanese Patent Application Laid-Open No. 62-229791 discloses that the operating frequency is changed according to the lighting state and non-lighting state of the lamp. There is described a circuit that oscillates at a frequency that is substantially equal to the voltage resonance frequency of the configured resonance circuit and that oscillates at a frequency that deviates from the resonance frequency after lighting.

  Japanese Patent Application Laid-Open No. 03-167795 describes that when the discharge start of the discharge lamp is detected, the operating frequency of the switching element is gradually moved from the frequency at no load to the frequency at lighting. .

  Further, in Japanese Patent Laid-Open No. 03-167796, when it is determined that the discharge lamp is not in a lighting state, the operating frequency of the switching element is set to be higher than the resonance frequency, higher than the resonance frequency, and higher than the first frequency. Are switched alternately to the lower second frequency, and the transition speed from the second frequency to the first frequency is set sufficiently higher than the transition speed from the first frequency to the second frequency. Things are listed.

  Furthermore, in Japanese Patent Laid-Open No. 04-342990, when starting or restarting a discharge lamp, the output frequency is set to a frequency close to the resonance frequency of the LC series resonance circuit, and the output of the lamp current detection means is set to a predetermined value. If it exceeds, the output frequency is switched to the lighting frequency.

  Further, Japanese Patent Application Laid-Open No. 07-169583 is provided with a frequency control means for changing the frequency of the output voltage of the DC-AC conversion circuit, and the frequency control means when the non-lighting state of the discharge lamp is determined by the lighting determination means. Increases the frequency of the output voltage of the DC-AC conversion means to a value sufficient to cause series resonance by the inductor and the capacitor, and when the lighting state of the discharge lamp is determined by the lighting determination means, the frequency control means is DC-AC A device that lowers the frequency of the output voltage of the conversion circuit is described.

  Furthermore, the special table 2001-501767 has detection means configured to detect the state of the gas discharge lamp, and the control circuit means controls the frequency of the inverter as a function of the output of the detection means, Alternatively, feedback circuit means for effectively changing the frequency of the inverter in response to the power detection means is provided, and the power supplied to the gas discharge lamp is maintained near a predetermined level, or the inverter is gas discharge It is configured to operate continuously at a frequency that decreases to approach the resonant frequency until and after the lamp is started, and the inverter is at least until the operation of the gas discharge lamp changes from glow mode to arc mode. The inverter is configured to operate at a frequency that decreases to approach a frequency near a specific frequency. After the operation of the gas discharge lamp changes from the glow mode to the arc mode, the gas discharge lamp is started and transitions from the glow mode to the arc mode by being configured to operate at a frequency higher than other resonance frequencies. And a step of operating the inverter at a frequency that decreases from a specific frequency to approach the resonance frequency until the gas discharge lamp starts, and a transition from a glow to an arc of the gas discharge lamp. And further comprising operating the inverter at a frequency that increases towards near a particular frequency until it occurs and operating the inverter at a frequency higher than other resonant frequencies at which the gas discharge lamp is in a stable operating state. Are listed.

JP-A-02-215091 Japanese Patent Laid-Open No. 03-102798 Japanese Patent Laid-Open No. 04-017296 JP 04-272695 A Japanese Patent Laid-Open No. 04-272698 JP-A-10-284265 JP2003-257687A JP 2005-038813 A JP-A-2005-050661 JP 55-148393 A JP 52-121975 JP 2004-127656 A JP 2004-327117 A JP-A-2005-071842 JP 62-229791 Japanese Patent Laid-Open No. 03-167795 Japanese Patent Laid-Open No. 03-167796 JP 04-342990 A JP 07-169583 A Special table 2001-501767

  However, there has been a problem that has not been solved by the prior art as described above. In the case of a high-intensity high-intensity discharge lamp, there is a large difference in the behavior of the resonance circuit between a state where no discharge is generated in the lamp and a glow discharge state or an arc discharge state, and the tuning of the frequency of the periodic voltage applying means is identified This has the limitation that it can only be carried out in the absence of any discharge in the lamp. During the occurrence of glow discharge or arc discharge, the voltage between the two poles of the lamp becomes a voltage specific to the discharge state of the lamp and power is consumed by the lamp, as if it were a Zener diode. This is because the value is very low.

  After the glow discharge or arc discharge has occurred, it may be considered that the need for resonance assist is lost after that, but the discharge disappears until all the discharge material enclosed in the lamp is vaporized. There is always the possibility to do. For example, in the case of a high-pressure mercury lamp in which mercury is sealed, arc discharge called field emission occurs from liquid mercury adhering to the cathode electrode, and when liquid mercury is depleted, it tries to return to glow discharge. Since the glow discharge has a higher voltage than the arc discharge, the discharge will be extinguished unless the power supply circuit immediately supplies a voltage sufficient to maintain the glow discharge. At this time, if the resonance assist is resumed immediately, the probability of the discharge disappearing can be reduced. Therefore, it is important to wait in a state where the resonance assist can be resumed at high speed in preparation for the return to the glow discharge. Become.

  In addition, dielectric breakdown in the discharge space of the discharge lamp and the start of discharge may occur accidentally, so if there is a fact that the discharge of the lamp started, Even if resonance assist is performed under the same conditions as described above, the start of discharge is not necessarily reproduced.

  The problem to be solved by the present invention is that even if the resonance frequency of the resonance circuit varies, the frequency of the periodic voltage applying means can be tuned, and even when the return from the arc discharge to the glow discharge or the disappearance occurs. Another object of the present invention is to provide a discharge lamp lighting circuit that can achieve resonance assist at a high speed and ensure reliable lighting performance at the time of starting.

  A discharge lamp lighting circuit according to claim 1 of the present invention is a discharge lamp lighting circuit for starting and lighting a discharge lamp (Ld) in which a pair of main discharge electrodes (E1, E2) are arranged to face each other. A resonance circuit comprising a power feeding circuit (Ux), a resonance inductor (Lh) and a resonance capacitor (Ch) for increasing the supply voltage to the discharge lamp (Ld) when the discharge lamp (Ld) is started (Nh), a periodic voltage applying means (Uj), a periodic driving circuit (Ug) for driving the periodic voltage applying means (Uj), a frequency of the periodic voltage applying means (Uj), and the resonance circuit (Nh) And a tuning degree detecting means (Un) for generating a tuning degree signal (Sn) corresponding to a difference from the resonance frequency of the first and second periodic drive circuits (Ug) receiving the input of the frequency control signal (Sf) Oscillation frequency is controlled And a frequency control circuit (Uf) for generating the frequency control signal (Sf). In the starting sequence of the discharge lamp (Ld), the frequency control circuit (Uf) The frequency control signal starts from one of the upper limit frequency and the lower limit frequency of the frequency variable oscillator (Vco) and sweeps to a range not exceeding the other frequency while monitoring the tuning degree signal (Sn). A sweep operation for changing (Sf) is performed, and after the end of the sweep operation, the frequency control circuit (Uf) sets the value of the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh). It operates so as to be determined and input to the variable frequency oscillator (Vco).

  The discharge lamp lighting circuit according to claim 2 of the present invention is the discharge lamp lighting circuit according to claim 1, wherein the frequency control circuit (Uf) inputs the frequency control signal to the frequency variable oscillator (Vco) after the end of the sweep operation. The value of (Sf) corresponds to the lower limit frequency from the upper limit frequency of the frequency variable oscillator (Vco) in the vicinity of the value of the frequency control signal (Sf) corresponding to the determined resonance frequency of the resonance circuit (Nh). The sweeping is performed over a narrower range than the range to be performed.

  The discharge lamp lighting circuit according to claim 3 of the present invention further comprises discharge generation detecting means (Ud) for detecting presence or absence of occurrence of discharge of the discharge lamp (Ld) in the invention of claims 1 to 2. Before the end of the sweep operation, when the discharge occurrence detection means (Ud) detects a discharge occurrence state, the frequency control circuit (Uf) interrupts the sweep operation, and then the discharge occurrence detection means ( When Ud) detects a non-discharge occurrence state, the sweep operation is retried from a frequency within the range in which the sweep operation has been performed previously.

  A discharge lamp lighting circuit according to a fourth aspect of the present invention further comprises a starter circuit (Ut) for applying a high voltage pulse to the discharge lamp (Ld) according to the first to third aspects of the invention, and the starter circuit (Ut) is controlled to be operable after the end of the sweep operation.

  The discharge lamp lighting circuit according to claim 5 of the present invention has a resonant transformer (Th) having a primary side winding (Ph) and a secondary side winding (Sh) in the invention of claims 1 to 4, The resonant inductor (Lh) is the primary winding (Ph), and the periodic voltage applying means (Uj) is connected to the resonant circuit (Nh) so as to excite parallel resonance, and the discharge lamp ( One end of Ld) is connected to one end of the secondary winding (Sh).

  According to the first aspect of the present invention, in the starting sequence of the discharge lamp (Ld), the frequency control circuit (Uf) monitors the tuning degree signal (Sn) and monitors the upper limit frequency of the frequency variable oscillator (Vco). Alternatively, a sweep operation is performed in which the frequency control signal (Sf) is changed so that the frequency control signal (Sf) is swept to a range that does not exceed the other frequency starting from one of the lower limit frequencies, and the frequency control is performed after the sweep operation is completed. The circuit (Uf) is configured to operate so as to determine a value of the frequency control signal (Sf) corresponding to a resonance frequency of the resonance circuit (Nh) and input the value to the frequency variable oscillator (Vco). Therefore, even if the resonance frequency of the resonance circuit varies, the frequency of the periodic voltage applying means can be tuned and the return from the arc discharge to the glow discharge can be performed. Even if the or extinction has occurred, fast can the resonance assisted resumed, it is possible to provide a discharge lamp lighting circuit that achieved to ensure reliable lighting of the discharge lamp at startup.

  According to the invention of claim 2, after the end of the sweep operation, the frequency control circuit (Uf) is determined as the value of the frequency control signal (Sf) input to the frequency variable oscillator (Vco). Sweep over a range narrower than the range corresponding to the lower limit frequency from the upper limit frequency of the frequency variable oscillator (Vco) in the vicinity of the value of the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh). With this configuration, there is an error in the value of the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh) determined by the sweep operation, or the resonance frequency due to a temperature change of the resonance circuit element. Even when there is a drift, it is possible to provide a discharge lamp lighting circuit that achieves a sufficient increase in the voltage applied to the lamp.

  According to a third aspect of the present invention, the apparatus further comprises discharge generation detection means (Ud) for detecting whether or not the discharge lamp (Ld) has generated discharge, and before the end of the sweep operation, the discharge generation detection means. When (Ud) detects a discharge occurrence state, the frequency control circuit (Uf) interrupts the sweep operation, and then when the discharge occurrence detection means (Ud) detects a non-discharge occurrence state, Since the sweep operation is retried from a frequency within the range where the sweep operation is performed first, discharge starts in the middle of the sweep operation, and the frequency corresponding to the resonance frequency of the resonance circuit (Nh) It is possible to provide a discharge lamp lighting circuit that achieves proper handling even when the value of the control signal (Sf) cannot be determined.

  According to a fourth aspect of the present invention, the starter circuit (Ut) is controlled to be operable after the end of the sweep operation, so that the discharge lamp (Ld) is in the middle of the sweep operation. In addition, it is possible to provide a discharge lamp lighting circuit that suppresses the start of the main discharge and reduces the probability of the retry of the sweep operation described above.

  According to invention of Claim 5, it has the resonance transformer (Th) which has a primary side winding (Ph) and a secondary side winding (Sh), and the said resonance inductor (Lh) is the said primary side winding. (Ph), and the periodic voltage applying means (Uj) is connected to the resonance circuit (Nh) to excite parallel resonance, and one end of the discharge lamp (Ld) is connected to the secondary winding (Sh). ), It is possible to realize resonance assist that enjoys the excellent advantages of the present invention even in a DC drive type discharge lamp lighting circuit, and further, an AC drive type discharge lamp lighting. In the circuit, by reducing the inductance of the secondary winding (Sh) of the resonance transformer (Th), it is possible to reduce the occurrence of instantaneous interruption, overshoot, and vibration of the lamp luminous flux. It is possible to provide a lamp lighting circuit.

  As described above, according to the present invention, even when the resonance frequency of the resonance circuit varies, the frequency of the periodic voltage application means can be tuned, and when the return from the arc discharge to the glow discharge or the disappearance occurs. However, it is possible to provide a discharge lamp lighting circuit capable of resuming resonance assist at high speed and achieving reliable lighting performance of the discharge lamp at start-up.

  First, the form for implementing this invention is demonstrated using FIG. 1 which is a block diagram which simplifies and shows one form of the discharge lamp lighting circuit of this invention. In the present embodiment, the winding of the transformer functions as the resonant inductor (Lh).

  A power supply circuit (Ux) including a switching circuit of a method such as a step-down chopper or a step-up chopper outputs a suitable voltage / current according to the state of the discharge lamp (Ld) or the lighting sequence. An inverter (Ui) composed of a full bridge circuit or the like converts the output voltage of the power feeding circuit (Ux) into, for example, a periodically inverted AC voltage and outputs it, and outputs a pair of mains of the discharge lamp (Ld). It is applied to the electrodes (E1, E2) for discharging via the secondary winding (Sh) of the resonant transformer (Th).

  When starting the lamp, the voltage output from the power supply circuit (Ux) for a no-load open circuit voltage is typically about 200 to 300 V, the lamp voltage during glow discharge is typically 100 to 200 V, and arc discharge. The lamp voltage immediately after the transition is about 10 V, and it is desirable that the power feeding circuit (Ux) be controlled so that the flowing current does not exceed a specified limit current value during glow discharge and arc discharge.

  A resonance capacitor (Ch) is connected in parallel to the primary side winding (Ph) as the resonance inductor (Lh), and the resonance capacitor (Ch) and the primary side winding (Ph) cause parallel resonance. A resonant circuit (Nh) is formed. The resonance frequency at this time is calculated mainly depending on the product of the capacitance of the resonance capacitor (Ch) and the inductance of the primary winding (Ph). However, if the secondary winding (Sh) side includes any capacitor component such as stray capacitance, correction is added to the calculation result of the resonance frequency.

  At start-up, a periodic voltage is applied from the periodic voltage applying means (Uj) to the resonance circuit (Nh). When the resonance frequency described above has a relationship of fundamental resonance, higher-order resonance, or a relationship close thereto with respect to the frequency of the voltage of the periodic voltage applying means (Uj), the resonance circuit (Nh) has a resonance current. Flows, and a high voltage is generated in the primary winding (Ph). With respect to the voltage generated in the primary winding (Ph), a voltage transformed in accordance with the turn ratio is induced in the secondary winding (Sh).

  For example, if the voltage of the node (T31) with respect to the node (T32) is 200V and the AC voltage generated in the secondary winding (Sh) is ± 800V in peak-peak value, the node (T42) A voltage of −600 to 1000 V is applied to the electrodes (E1, E2) for the main discharge of the discharge lamp (Ld), between the first and second nodes (T41).

  Resonance occurs in the presence of variations in the resonance frequency due to variations in the resonance circuit, specifically, variations in capacitance of the resonance capacitor (Ch) and inductance of the primary winding (Ph). In order to satisfy the condition, in the present invention, the drive frequency of the periodic voltage applying means (Uj) can be changed. Therefore, the periodic drive circuit (Ug) that generates the periodic voltage application drive signal (Sj) for driving the periodic voltage application means (Uj) constitutes a frequency variable oscillator (Vco) that is an oscillator having a variable oscillation frequency. Contains as an element. The variable frequency oscillator (Vco) receives an input of the frequency control signal (Sf) and controls the oscillation frequency. The relationship between the voltage level of the frequency control signal (Sf) and the oscillation frequency level is For example, a positive correlation can be used. Of course, it may be negatively correlated.

  On the other hand, in order to tune the oscillation frequency of the variable frequency oscillator (Vco) to the resonance frequency, it is necessary to detect how much the resonance condition is satisfied, and the tuning degree detection means (Un) for that purpose includes: A tuning degree signal (Sn) whose magnitude changes corresponding to the difference between the frequency of the periodic voltage applying means (Uj) and the resonance frequency of the resonance circuit (Nh) is generated. For example, as shown in FIG. 1, the voltage generated at both ends of the primary winding (Ph) is acquired and used as the tuning signal (Sn) by an analog signal holding a voltage corresponding to a peak value, for example. What to do. Moreover, it can also be comprised by what acquires the alternating voltage which generate | occur | produces at the both ends of the said secondary side winding (Sh).

  The frequency control circuit (Uf) changes the frequency control signal (Sf) from a lower limit value to an upper limit value of the frequency control signal (Sf) determined in advance corresponding to the lower limit and the upper limit of the variation in the resonance frequency. That is, by performing the sweep operation, the oscillation frequency of the frequency variable oscillator (Vco) starts from the upper limit frequency and is swept to the lower limit frequency. Naturally, conversely, it may sweep from the lower limit frequency to the upper limit frequency, and is not limited to a continuous sweep, and may be a stepwise change.

  The frequency control circuit (Uf) monitors the tuning degree signal (Sn) when performing the sweep operation, and this value is maximum, that is, the frequency of the periodic voltage applying means (Uj) and the resonance. It operates to store the generation condition of the frequency control signal (Sf) when the difference from the resonance frequency of the circuit (Nh) is minimum. Then, after the sweep operation is completed, the frequency control circuit (Uf) has a minimum difference between the frequency of the periodic voltage application means (Uj) and the resonance frequency of the resonance circuit (Nh). By reproducing and fixing the generation condition of the frequency control signal (Sf), the value of the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh) is determined and the frequency variable oscillator (Vco) is determined. ).

  FIG. 10 is a timing chart conceptually showing the operation of FIG. 1 described here. (A) is a waveform of a voltage (Vnh) generated in the resonance circuit (Nh), and (b) is the tuning degree signal. (Sn) waveform, (c) represents the waveform of the frequency control signal (Sf). In the initial period of the starting sequence of the discharge lamp (Ld), a lower limit value (VSf1) of the frequency control signal (Sf) in a period (Ta) immediately before the voltage application for starting the discharge to the discharge lamp (Ld) is performed. ) To the upper limit value (VSf2).

  At that time, the maximum value of the tuning signal (Sn) correlated with the voltage (Vnh) generated in the resonance circuit (Nh) is obtained, that is, the generation condition of the frequency control signal (Sf) at time (ta), that is, the The conditions for generating the optimum frequency control signal value (VSfr) of the frequency control signal (Sf) are stored. Then, after expiration of the period (Ta), the stored conditions for generating the optimum frequency control signal value (VSfr) are reproduced, and the discharge lamp (Ld) in the starting sequence of the discharge lamp (Ld) is started to discharge. Therefore, the optimum resonance assist is realized in the period during which the voltage is applied.

  FIG. 11 is a further timing chart conceptually showing the operation of FIG. 1 described here. (A) is a waveform of the voltage (Vnh) generated in the resonance circuit (Nh), and (b) is The waveform of the tuning signal (Sn) and (c) represent the waveform of the frequency control signal (Sf). This figure shows a state in which arc discharge occurred in the discharge lamp (Ld) at time (tb) and the state was maintained for a while, but discharge disappeared at time (tc).

  In the present invention, once the optimum frequency control signal value (VSfr) can be determined once in the period (Ta), it is not necessary to perform automatic tuning again thereafter. Therefore, when the extinction occurs, the resonance phenomenon immediately reoccurs and the increase in the voltage applied to the discharge lamp (Ld) is recovered, and the optimum resonance assist is reproduced.

  With the configuration as described above, the discharge lamp lighting circuit of FIG. 1 has the smallest difference between the frequency of the periodic voltage applying means (Uj) and the resonance frequency of the resonance circuit (Nh) by the sweep operation. Since the generation condition of the frequency control signal (Sf) at the time, that is, the generation condition of the resonance frequency can be found, the frequency of the periodic voltage applying means can be tuned even if the resonance frequency of the resonance circuit varies. In addition, since the found conditions can be reproduced and fixed, resonance assist can be resumed at high speed even when the arc discharge returns to the glow discharge or disappears. As a result, reliable lighting performance of the discharge lamp can be ensured at the start.

  The sweep operation does not necessarily need to sweep from the upper limit frequency to the lower limit frequency, or from the lower limit frequency to the upper limit frequency, and the frequency control circuit (Uf) has passed the resonance frequency during the sweep operation. If this is detected, the sweep operation may be interrupted, thereby saving an extra time for the sweep operation and speeding up the start-up of the discharge lamp (Ld).

  Further, when finding the optimum frequency control signal value (VSfr) at which the value of the tuning level signal (Sn) is maximum, the value of the tuning level signal (Sn) is increased to an appropriately determined value VSnx. The value VSfA of the frequency control signal (Sf) and the value VSfB of the frequency control signal (Sf) when exceeding the maximum value of the tuning degree signal (Sn) and further decreasing to the value VSnx are stored. In addition, the optimum frequency control signal value (VSfr) can be determined by calculating an intermediate value between the value VSfA and the value VSfB.

  Here, processing when main discharge, particularly glow discharge, occurs in the discharge lamp (Ld) during the sweep operation will be described. During the discharge of the discharge lamp (Ld), since the impedance between the electrodes (E1, E2) is low, the Q value of the resonant circuit (Nh) is lowered, and the resonant transformer (Th) generates a high voltage. Instead, the lamp voltage is a voltage specific to glow discharge. Therefore, it is difficult to determine the optimum value of the frequency control signal (Sf) according to the condition that gives the maximum value of the tuning level signal (Sn). In such a case, the problem can be avoided by temporarily interrupting the sweep operation and retrying.

  In addition to the method of temporarily interrupting and retrying the sweep operation, there is also a method of determining the optimum frequency control signal (Sf) from the value of the tuning degree signal (Sn) before and after the occurrence of glow discharge. FIG. 13 is a further timing chart conceptually showing an operation when a glow discharge is generated during the sweep operation, wherein (a) is a waveform of a voltage (Vnh) generated in the resonance circuit (Nh), b) represents the waveform of the tuning degree signal (Sn), and (c) represents the waveform of the frequency control signal (Sf).

  As described above, the lamp voltage is clamped to a specific value during the glow discharge. Therefore, as shown in this figure, the tuning signal (Sn) includes the frequency control signal (Sf). A flat portion (Snp) that does not correspond to the sweep appears. The value of the frequency control signal (Sf) corresponding to the start and end of the flat portion (Snp), that is, the glow lower and upper limit frequency control signal values (VSf3, VSf4) are stored, and the optimum frequency control signal value ( VSfr) can also be determined by calculating an intermediate value between them.

  FIG. 15 is a timing chart conceptually showing the operation when the discharge lamp (Ld) starts to disappear after starting the main discharge, and (a) shows the voltage (Vnh) generated in the resonance circuit (Nh). (B) represents the waveform of the tuning degree signal (Sn), (c) represents the waveform of the frequency control signal (Sf), and (d) represents the waveform of the periodic voltage application drive signal (Sj).

  In the figure, the frequency control signal (Sf) is determined by the sweep operation in the period (Ta), and then the main discharge in the discharge lamp (Ld), particularly the arc discharge, is started at the subsequent time (tb). In the period (Tu, Tu ′), the frequency control signal (Sf) is held and the driving of the periodic voltage applying means (Uj) based on the periodic voltage applying drive signal (Sj) is continued. is there. After the main discharge of the discharge lamp (Ld) is started, if there is no concern about the extinction of the discharge, the periodic on / off operation of the resonant drive switch element (Kh) may be stopped. .

  However, under the condition or period (Tv) in which the discharge may be extinguished, the resonance drive switch element (Kh) is periodically turned on / off even after the main discharge of the discharge lamp (Ld) starts. The operation may be continued. In this case, as described above, during the main discharge of the discharge lamp (Ld), since the impedance between the electrodes (E1, E2) becomes low, the Q value of the resonance circuit (Nh) decreases, and the resonance transformer (Th) does not generate a high voltage, but when the extinction of discharge occurs, the resonance circuit (Nh) immediately grows in resonance because the resonance circuit (Nh) recovers to a high Q value. Thus, a high AC voltage is generated in the resonant transformer (Th), and the operation is performed so that restart is attempted.

  Alternatively, since the discharge state of the discharge lamp can be identified by the lamp voltage detection signal (Sv), the operation of the resonance drive switch element (Kh) is stopped during discharge, and when the extinction is detected, the resonance drive switch You may make it control to restart operation | movement of an element (Kh).

  The form for implementing this invention is demonstrated using FIG. 2 which is a block diagram which simplifies and shows the other form of the discharge lamp lighting circuit of this invention. This figure is an example more specifically showing the configuration of the periodic voltage applying means (Uj) and the tuning degree detecting means (Un) shown in FIG.

  The periodic voltage applying means (Uj) is configured by connecting a resonance driving power source (Mh) and a resonance driving switch element (Kh) in series, and in parallel resonance when the resonance driving switch element (Kh) is in an ON state. A voltage is applied to the resonance circuit (Nh). However, at the moment when the resonant drive switch element (Kh) is turned on, a surge current may be mixed into the resonant drive current through the resonant capacitor (Ch). It is desirable to insert Zh) in series with the resonant drive switch element (Kh).

  The tuning degree detection means (Un) is connected to one end of the resonance circuit (Nh) in order to detect an increase in voltage generated in the resonance circuit (Nh), and the resonance driving power source (Mh) Obtained by adding the voltage generated at both ends of the resonance circuit (Nh) to the tuning degree detection means (Un). Since the signal input to the tuning degree detecting means (Un) has a high voltage, it is converted into a low voltage signal by the voltage dividing resistors (Rn, Rm). The signal obtained after the voltage division has a waveform including a sine wave component due to a resonance phenomenon. Therefore, the signal is rectified by a diode (Dn) so as to be a signal that can be easily handled by a frequency control circuit (Uf), which will be described later, and input to the frequency control circuit (Uf) as a tuning signal (Sn).

  FIG. 3 is an example showing another configuration of the tuning degree detection means (Un). In this figure, the tuning degree detecting means (Un) is provided with a tertiary winding (Ah) in the resonant transformer (Th) in order to detect an increase in voltage generated in the resonant circuit (Nh). The voltage generated from the line (Ah) is acquired.

  Thereby, a signal corresponding to the voltage across the resonance circuit (Nh) can be obtained. However, the voltage signal generated from the tertiary winding (Ah) has a sine waveform due to the resonance phenomenon. Similarly, the signal is rectified by a diode (Dl) so as to be a signal that can be easily handled by a frequency control circuit (Uf), which will be described later, and is input to the frequency control circuit (Uf) as a tuning signal (Sn).

  Since the tuning degree detection means (Un) shown in FIG. 2 detects the voltage including the voltage of the power feeding circuit (Ux), the voltage of the power feeding circuit (Ux) varies depending on the operation of the resonance circuit. In this case, there may be some error in detecting an increase in voltage generated in the resonance circuit (Nh). However, in the tuning degree detection means (Un) shown in FIG. 3, the resonance circuit (Nh) Since only the AC component in is detected, there is an advantage not including such an error.

  An embodiment for carrying out the present invention will be described with reference to FIG. 4 which is a diagram showing a simplified form of one embodiment of a discharge lamp lighting circuit of the present invention. This figure is an example specifically showing the frequency control circuit (Uf) and the variable frequency oscillator (Vco) constituting the periodic drive circuit (Ug) shown in FIG.

  The frequency control circuit (Uf) includes a microprocessor unit (Mpu). In order to generate a frequency control signal (Sf) corresponding to the sweep operation, the microprocessor unit (Mpu) has, for example, a step shape in 1 LSB increments. Frequency data (Sdf) is generated as a digital signal whose value increases or decreases. The frequency control signal (Sf) is output in the form of an analog signal via a DA converter (Dao). The microprocessor unit (Mpu) includes a CPU, a program memory, a data memory, a clock pulse generation circuit, a time counter, an IO controller for inputting / outputting digital signals, and the like.

  As an example, the variable frequency oscillator (Vco) in this figure is configured using a multivibrator circuit. The block (Uw) in the frequency variable oscillator (Vco) can be easily configured using a timer IC such as NE555 manufactured by Texas Instruments.

  In this circuit, assuming a simple case where current does not flow in and out through the resistor (Ra), first, a capacitor (from a reference power source (Vcc) through a resistor (Rc) and a resistor (Rd) ( Cs) is charged, and the voltage of the capacitor (Cs) increases according to the time constants of the capacitor (Cs), the resistor (Rc), and the resistor (Rd). When the capacitor (Cs) voltage exceeds a predetermined voltage, the comparator (Adr) resets the flip-flop (Ff) and turns on the transistor (Trr).

  Next, the electric charge accumulated in the capacitor (Cs) is discharged through the resistor (Rd) and the transistor (Trr), and the voltage of the capacitor (Cs) is changed between the capacitor (Cs) and the resistor (Rd). ) And the time constant. When the capacitor (Cs) voltage falls below a predetermined voltage, the comparator (Ads) sets the flip-flop (Ff) to turn off the transistor (Trr). Then, the capacitor (Cs) is again charged and the above-described operation is repeated.

  In the figure, a frequency control signal (Sf) is connected to the capacitor (Cs) via the resistor (Ra). As a result, current flows into and out of the capacitor (Cs) through the resistor (Ra) depending on the voltage level of the frequency control signal (Sf), and thus the capacitor (Cs) as described above. The oscillation frequency can be increased or decreased by the frequency control signal (Sf) with respect to a simple oscillation operation according to the time constants of the resistor (Rc) and the resistor (Rd), and functions as a frequency variable oscillator. Can be made.

  Incidentally, in the frequency variable oscillator (Vco) of this figure, when a low voltage such as 0 volts is output from the DA converter (Dao) as the frequency control signal (Sf), the capacitor (Cs ) Cannot exceed the threshold voltage determined from the values of the resistors (Ru1, Ru2, Ru3), so that the oscillation can be stopped and the periodic voltage application drive signal (Sj) can be stopped. Any mechanism for stopping the periodic voltage application drive signal (Sj) may be used.

  The output signal of the flip-flop (Ff) is matched in polarity, for example, via an inverter (Inv) as necessary, and then the resonant drive switch element (Kh) is used as the periodic voltage application drive signal (Sj). Connected to its gate terminal for driving. With such a configuration, a periodic voltage applying means (Uj) that operates at a frequency based on a command from the frequency control circuit (Uf) is realized.

  On the other hand, the tune degree signal (Sn) from the tune degree detecting means (Un) is AD converted into tune degree data (Sdn) as a digital signal by the AD converter (Adi), and this is converted into the microprocessor unit (Mpu). ) Is read, the frequency control circuit (Uf) can monitor the state of the resonance circuit.

  By configuring the frequency control circuit (Uf) as described above, the discharge lamp lighting circuit of FIG. 4 starts the discharge lamp (Ld) based on the program control of the microprocessor unit (Mpu). In the sequence, the frequency control circuit (Uf) starts from one of the upper limit frequency and the lower limit frequency of the frequency variable oscillator (Vco) while monitoring the tuning degree signal (Sn) and sets the other frequency. A sweep operation is performed to change the frequency control signal (Sf) so as to sweep to a range not exceeding, and after the sweep operation is completed, the frequency control circuit (Uf) corresponds to the resonance frequency of the resonance circuit (Nh). Determining a value of the frequency control signal (Sf) to be operated and inputting the value to the frequency variable oscillator (Vco) It can be realized.

  In addition, although the example using the said block (Uw) by timer IC was mentioned about implementation | achievement of the said frequency variable oscillator (Vco), you may comprise an oscillator with general purpose logic IC or an operational amplifier. In the figure, the frequency control circuit (Uf) includes the AD converter (Adi), the microprocessor unit (Mpu), and the DA converter (Dao), and the frequency variable oscillator (Vco). However, since the variable frequency oscillator can be configured using a programmable counter or the like that can set the frequency division ratio by digital data, the periodic drive circuit (Ug) in the discharge lamp lighting circuit of the present invention is: A peripheral LSI built-in type microprocessor LSI can be used to integrate the function of the frequency control circuit (Uf) and the function of the frequency variable oscillator (Vco).

  FIG. 5 is an example showing another configuration of the frequency variable oscillator (Vco). The block (Uv) in the variable frequency oscillator (Vco) in the figure can be easily configured using a switching regulator IC such as M51995 manufactured by Renesas Technology.

  In this circuit, the capacitor (Cs ′) is charged from the reference voltage source (Vref) through the resistor (Rc ′) based on the time constants thereof, and the capacitor (Cs ′) is charged by the oscillator controller (Osc). By monitoring the charging voltage and discharging the capacitor (Cs ′), an oscillator that outputs the sawtooth wave oscillation signal (Ss) is configured. A frequency control signal (Sf) is connected to the capacitor (Cs ′) via a resistor (Ra ′). As a result, current flows into and out of the capacitor (Cs ′) via the resistor (Ra ′) depending on the voltage level of the frequency control signal (Sf), and therefore the capacitor (Cs ′) and the resistor With respect to a simple oscillation operation according to the time constant (Rc ′), the frequency control signal (Sf) can increase or decrease the oscillation frequency, and can function as a frequency variable oscillator.

  Incidentally, in the frequency variable oscillator of this figure, as in the case of FIG. 4, when a low voltage such as 0 volts is output from the DA converter (Dao) as the frequency control signal (Sf), Oscillation can be stopped.

The output of the reference power source (Vc) and the oscillation signal (Ss) of the sawtooth wave from the oscillator controller (Osc) are compared by a comparator (Cmg) to generate a PWM signal (Pwm).
By setting the value of the reference power source (Vc), the duty ratio of the PWM signal (Pwm) can be set, and the PWM signal (Pwm) having the duty ratio set in this way is resonantly driven. The switch element (Kh) may be driven. However, particularly when a parallel resonance circuit is used as shown in this figure, when the drive frequency and the resonance frequency do not match, a large current may flow through the resonance drive switch element (Kh), and the resonance drive switch element (Kh) There is a problem that creates the risk of damage.

  In order to avoid this problem, in the circuit shown in this figure, the periodic voltage application drive signal (Sj) is forcibly turned off when the current flowing through the resonance drive switch element (Kh) reaches a specified current value. A so-called pulse-by-pulse current limiting function for limiting the on-time width of the resonance driving switch element (Kh) in a state is provided. A current detection resistor (Rs) is provided in series with the resonance drive switch element (Kh), and a voltage signal and a reference voltage generated in the current detection resistor (Rs) according to a current flowing through the resonance drive switch element (Kh). The voltage of the source (Ve) is compared with a comparator (Cmi), and if the signal detected by the current detection resistor (Rs) is higher than the voltage of the reference voltage source (Ve), a flip-flop (Ffc) ) No Q output (Q bar) signal (Sfc) is latched low.

  As a result, the logical product gate (And) for effectively transmitting the PWM signal (Pwm) to the output buffer circuit composed of the transistors (Tr5, Tr6) is invalidated by this signal, so that the PWM signal (Pwm) Even if the width of the high level is longer than necessary, the ON time width is set so that a current exceeding the current value defined by the size of the current detection resistor (Rs) does not flow to the resonance drive switch element (Kh). Can be limited.

  The latch state of the signal (Sfc) to the low level is maintained while the PWM signal (Pwm) is at the high level, and is automatically released by returning to the low level. Strictness is not required for setting the duty ratio of the PWM signal (Pwm) by setting (Vc), and it may be set sufficiently larger than the assumed duty ratio of the resonance drive switch element (Kh).

  Next, a mode for carrying out the invention will be described with reference to an example drawing showing a more specific configuration. FIG. 6 shows a specific example of a power feeding circuit (Ux) that can be used in the discharge lamp lighting circuit of the present invention. A power supply circuit (Ux) based on a step-down chopper circuit operates by receiving a voltage supplied from a DC power source (Mx) such as a PFC, and adjusts the amount of power supplied to the discharge lamp (Ld). In the power supply circuit (Ux), the current from the DC power source (Mx) is turned on / off by a switching element (Qx) such as an FET, and the smoothing capacitor (Cx) is charged via the choke coil (Lx). This voltage is applied to the discharge lamp (Ld) so that a current can flow through the discharge lamp (Ld).

  During the period when the switch element (Qx) is in the ON state, the smoothing capacitor (Cx) is directly charged and the discharge lamp (Ld) as a load is directly charged by the current through the switch element (Qx). While current is supplied, energy is stored in the choke coil (Lx) in the form of magnetic flux. During the period when the switch element (Qx) is in the off state, energy is stored in the choke coil (Lx) in the form of magnetic flux. A current is supplied to the discharge lamp (Ld) through the flywheel diode (Dx).

  In the step-down chopper-type power supply circuit (Ux), power is supplied to the discharge lamp according to a ratio of a period during which the switch element (Qx) is in an on state, that is, a duty cycle ratio, to an operation cycle of the switch element (Qx). The amount can be adjusted. Here, a gate drive signal (Sg) having a certain duty cycle ratio is generated by the power supply control circuit (Fx), and the gate terminal of the switch element (Qx) is controlled via the gate drive circuit (Gx). The on / off of the current from the DC power source (Mx) is controlled.

  The lamp current flowing between the electrodes (E1, E2) of the discharge lamp (Ld) and the lamp voltage generated between the electrodes (E1, E2) include a lamp current detecting means (Ix) and a lamp voltage detecting means ( Vx). The lamp current detecting means (Ix) can be easily realized by using a shunt resistor, and the lamp voltage detecting means (Vx) can be easily realized by using a voltage dividing resistor.

  The lamp current detection signal (Si) from the lamp current detection means (Ix) and the lamp voltage detection signal (Sv) from the lamp voltage detection means (Vx) are input to the power supply control circuit (Fx). The power supply control circuit (Fx) outputs the gate drive signal (Sg) so as to output a predetermined voltage in order to apply a no-load open voltage to the lamp during a period when the lamp current does not flow when the lamp is started. Is generated in a feedback manner. When the lamp starts and discharge current flows, the gate drive signal (Sg) is generated in a feedback manner so that the target lamp current is output.

  Here, the target lamp current is based on such a value that the electric power supplied to the discharge lamp (Ld) becomes a predetermined electric power depending on the voltage of the discharge lamp (Ld). However, immediately after starting, since the voltage of the discharge lamp (Ld) is low and the rated power cannot be supplied, the target lamp current is controlled so as not to exceed a certain limit value called an initial limit current. As the temperature rises, the voltage of the discharge lamp (Ld) rises, and when the current required for predetermined power input becomes equal to or less than the initial limit current, the state smoothly shifts to a state where the predetermined power input can be realized.

  FIG. 7 shows a simplified example of an inverter (Ui) that can be used in the discharge lamp lighting circuit of the present invention. The inverter (Ui) is configured by a full bridge circuit using switching elements (Q1, Q2, Q3, Q4) such as FETs. Each switch element (Q1, Q2, Q3, Q4) is driven by a respective gate drive circuit (G1, G2, G3, G4), and the gate drive circuit (G1, G2, G3, G4) In the phase in which the switch element (Q1) and the switch element (Q3) of the diagonal element are in the ON state, the switch element (Q2) and the switch element (Q4) of the other diagonal element are maintained in the OFF state. Conversely, in the phase where the switch element (Q2) and the switch element (Q4) of the other diagonal element are in the ON state, the switch element (Q1) and the switch element (Q3) of one diagonal element are It is controlled by inverter control signals (Sf1, Sf2) generated by the inverter control circuit (Uc) so as to be maintained in the off state. When the two phases are switched, a period called a dead time is inserted in which all of the switch elements (Q1, Q2, Q3, Q4) are turned off.

  When the switch elements (Q1, Q2, Q3, Q4) are MOSFETs, for example, a parasitic diode that is forward from the source terminal toward the drain terminal is built in the element itself (not shown). In the case of an element that does not have the parasitic diode, such as a bipolar transistor, an induced current caused by an inductance component present in the subsequent stage of the inverter (Ui) during the phase switching or dead time period described above. Therefore, it is desirable to connect the diodes corresponding to the parasitic diodes in antiparallel.

  FIG. 8 shows the discharge lamp lighting of the present invention in which the resonance drive power source (Mh) and the resonance drive current limiting means (Zh) are replaced with another form, and an example of the form of the starter circuit is specifically shown. It is a figure which simplifies and shows one form of a circuit.

  A resonance driving power source (Mh) of the periodic voltage applying means (Uj) is composed of a current supply diode (Dm) and a smoothing capacitor (Cm) that receive power from the power feeding circuit (Ux), and a resonance transformer (Th). A voltage is applied to a parallel resonance resonance circuit (Nh) including a primary winding (Ph) and a resonance capacitor (Ch). The resonant drive switch element (Kh) using a MOSFET or the like is periodically turned on and off under the control of the gate drive circuit (Gkh).

  Here, the current limiting regenerative transformer (Tz) and the regenerative diode (Dsz) which are part of the periodic voltage applying means (Uj) will be described. The current limiting regenerative transformer (Tz) functions as the resonance driving current limiting means (Zh) by the inductance of the primary side winding (Pz), and during the period when the resonance driving switch element (Kh) is in the ON state. Current is passed from the resonance driving power source (Mh) to the primary winding (Pz) of the current limiting regenerative transformer (Tz), and magnetic energy is stored in the current limiting regenerative transformer (Tz).

  When the resonant drive switch element (Kh) is turned off, the current-limited regenerative transformer (Tz) is converted into a current from the secondary winding (Sz) through the regenerative diode (Dsz) by a so-called flyback operation. ) Is regenerated in the resonance driving power source (Mh) and a voltage is applied to the resonance circuit (Nh). The voltage of the smoothing capacitor (Cm) is effectively boosted by the cooperation of the current supply diode (Dm), the smoothing capacitor (Cm), and the regenerative diode (Dsz), and the resonance circuit (Nh) The growth of the resonance phenomenon is further promoted.

  Due to the operation of the periodic voltage applying means (Uj), the resonance phenomenon of the resonance circuit (Nh) grows, and the voltage amplitude of the primary winding (Ph) of the resonance transformer (Th) increases. Therefore, a high AC voltage is generated in the secondary winding (Sh). This high voltage is superimposed on the no-load open-circuit voltage from the power feeding circuit (Ux) appearing at the output nodes (T31, T32) of the inverter (Ui), and is connected to the nodes (T41, T42). Applied to the electrodes (E1, E2) for the main discharge of the lamp (Ld).

  In the external trigger type discharge lamp (Ld), auxiliary electrodes (Et) other than the electrodes (E1, E2) for main discharge are provided so as not to contact the discharge space. The auxiliary electrode (Et) is configured to be applied with a high voltage pulse generated in the secondary winding (St) of the starter transformer (Tt) of the starter circuit (Ut).

  The starter circuit (Ut) receives a no-load open-circuit voltage from the power supply circuit (Ux) as a DC power supply, and sets a resistance (Rt) and a primary winding (Pt) of the starter transformer (Tt). The capacitor (Ct) is charged relatively slowly. When the charging voltage of the capacitor (Ct) reaches a predetermined voltage, a switch element (Qt) composed of a voltage sensitive element such as Sidac is turned on, and the voltage of the capacitor (Ct) A pulse is applied to the winding (Pt), and a high voltage pulse is generated in the secondary winding (St) of the starter transformer (Tt). As the switch element (Qt), an element having a trigger terminal such as an SCR as described in a starter circuit (Ut) part of FIG. 18 described later can be used.

  As described above, when the high AC voltage from the resonant transformer (Th) is applied to the electrodes (E1, E2) for main discharge of the discharge lamp (Ld), the discharge is performed as described above. By applying a high voltage pulse from the starter transformer (Tt) to the auxiliary electrode (Et) of the lamp (Ld), it is possible to start the main discharge of the discharge lamp (Ld) with very high accuracy. It becomes.

  In addition, since the path from the secondary winding (St) of the starter transformer (Tt) to the auxiliary electrode (Et) of the discharge lamp (Ld) is a high voltage, the shorter the path, the more advantageous. It is advantageous to separate the portion on the lamp side from the alternate long and short dash line connecting the nodes (T41, T4a, T4b, T42) from the discharge lamp lighting circuit to constitute one unit.

  FIG. 9 is a conceptual diagram of an example of a waveform relating to the embodiment of the discharge lamp lighting circuit of the present invention. The present invention is not limited to fundamental resonance, that is, the case where the resonance frequency of the resonance circuit (Nh) is the same as the frequency of the periodic voltage applying means (Uj). Can be applied even in the case of a condition that becomes an integral multiple of the frequency of the periodic voltage applying means (Uj).

  This figure shows an example in which the discharge lamp lighting circuit shown in FIG. 8 is operated under the condition of the third resonance, where (a) is the voltage across the terminals of the resonant capacitor (Ch), and (b) is the periodic voltage. This represents the state of the applied drive signal (Sj), and in the period (Ti) of one cycle of the periodic voltage applied drive signal (Sj), the vibration between the terminals of the resonant capacitor (Ch) has three cycles. I know that.

  Increasing the frequency of resonance assist makes the zero cross of the lamp applied voltage steep, so it is difficult for the discharge to extinguish at the zero cross, and this is effective in improving the startability of the lamp. The resonant drive switch can be realized without using a high-order resonance without increasing the drive frequency of the resonant drive switch element (Kh), that is, by reducing the conduction time of the resonant drive switch element (Kh) and reducing the switching loss. Increasing the frequency of resonance assist can be achieved while reducing the heat loss of the element (Kh).

  The further form for implementing this invention is demonstrated using FIG. 12 which is a timing diagram which shows one form of the discharge lamp lighting circuit of this invention. (A) of this figure represents the waveform of the voltage (Vnh) generated in the resonance circuit (Nh), and (b) represents the waveform of the frequency control signal (Sf).

  In order to generate a strong resonance phenomenon in the resonance circuit, it is necessary to accurately determine the frequency control signal (Sf). However, the determined frequency control signal (Sf) depends on a time delay such as the evaluation processing of the tuning degree signal (Sn) in the periodic drive circuit (Ug) or restrictions on the resolution of the frequency control circuit (Uf). The resonance inductor (Lh) generates heat by continuously flowing a current through the resonance inductor (Lh) even after being determined to be slightly out of the optimum value or even after the frequency control signal (Sf) is determined. As a result, when the inductance value changes, the resonance frequency may drift slightly.

  In order to avoid such a phenomenon, after the sweep operation in the period (Ta) is terminated and the value of the frequency control signal (Sf) is determined, the determined value of the frequency control signal (Sf) is It is effective to continue the sweep operation over a narrow range including. By operating in this way, even if the determined value of the frequency control signal (Sf) slightly deviates from the optimum value or the resonance frequency changes, the frequency control signal described above is used. By the operation of continuing the sweep operation over a narrow range including (Sf), the optimum frequency control signal (Sf) is always realized at a high frequency, and the period is out of the optimum frequency control signal (Sf) However, since the amount of deviation is very small, the voltage is not lowered so as to be harmful to the voltage applied to the discharge lamp (Ld) as shown in FIG.

  Therefore, when there is an error in the value of the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh) determined by the sweep operation, or there is a resonance frequency drift due to a temperature change of the resonance circuit element. However, a sufficient increase in the voltage applied to the lamp can be ensured.

  The further form for implementing this invention is demonstrated using FIG. 14 which is a timing diagram which shows one form of the discharge lamp lighting circuit of this invention. (A) of this figure is the waveform of the voltage (Vcx) of the smoothing capacitor (Cx) of the power feeding circuit (Ux), (b) is the waveform of the voltage (Vnh) generated in the resonance circuit (Nh), and (c) is the tuning. The waveform of the degree signal (Sn), (d) represents the waveform of the frequency control signal (Sf). The sweep operation of the frequency control signal (Sf) is performed in order to determine the frequency control signal (Sf) in the period (Tk), but arc discharge occurs in the discharge lamp (Ld) at a time (tk) in the middle thereof. It depicts the situation.

  On the other hand, the discharge generation detecting means (Ud) for detecting whether or not the discharge lamp (Ld) has generated a discharge generates a signal when, for example, the voltage of the tuning degree signal (Sn) is equal to or lower than a predetermined threshold voltage (Vth). What is necessary is just to comprise as what is output. Then, in response to this signal, the frequency control circuit (Uf) can detect the occurrence of discharge of the discharge lamp (Ld). The discharge generation detecting means (Ud) is configured to detect the voltage (Vcx) of the smoothing capacitor (Cx), that is, the lamp voltage detection signal (Sv), the current flowing through the discharge lamp (Ld), that is, the lamp current detection signal ( The occurrence of discharge may be detected by Si).

  In this case, the frequency control circuit (Uf) corresponds the value of the frequency control signal (Sf) when the discharge occurrence detection means (Ud) detects the discharge occurrence state to the resonance frequency of the resonance circuit (Nh). Whether the sweep operation is temporarily interrupted during the discharge generation period (Tm) and the discharge is continued to complete the start-up or the extinction occurs. To monitor.

  After that, when the discharge occurrence detection means (Ud) detects a non-discharge occurrence state at time (tm), the frequency control circuit (Uf) is within the range in which the sweep operation is performed previously in the period (Tn). Retry the sweep operation from the frequency. When retrying the sweep operation, it is not always necessary to restart the sweep operation from the beginning. From the value of the frequency control signal (Sf) when the discharge occurrence detection means (Ud) detects the discharge occurrence state, etc. The sweep operation may be performed from the middle.

  In this figure, the value of the frequency control signal (Sf) performed halfway in the period (Tk) is held, and slightly smaller than the value of the frequency control signal (Sf) held in the period (Tn). The sweeping operation of the frequency control signal (Sf) is resumed from the value returned by only this. With such a device, it is possible to save time spent for a part of the sweep operation that is greatly deviated from the resonance condition.

  The value of the frequency control signal (Sf) when the discharge occurrence detecting means (Ud) detects the discharge occurrence state is set to the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh). In the period from when the extinction occurs until the frequency control circuit (Uf) starts the retry of the sweep operation, the resonance phenomenon immediately reoccurs and the discharge lamp (Ld) is used. This is because the increase in the applied voltage is recovered and the resonance assist is reproduced, and for example, the possibility of shifting to glow discharge is increased.

  An embodiment for carrying out the present invention will be described with reference to FIG. 16, which is a diagram showing one embodiment of a discharge lamp lighting circuit of the present invention. Since the output voltage from the power supply circuit (Ux) during the sweep operation is a no-load open voltage, as described above, when the charging voltage of the capacitor (Ct) reaches a predetermined voltage, a voltage sensitive element such as Sidac is used. The configured switch element (Qt) is turned on, and a high voltage pulse is generated in the secondary winding (St) of the starter transformer (Tt). As a result, as described in the description of FIG. 14, the discharge lamp (Ld) starts the main discharge even during the sweep operation of the frequency control signal (Sf), and the frequency control signal (Sf) is accurately determined. May interfere.

  Therefore, the discharge lamp lighting circuit of this figure is provided with a switch element (Kt) for short-circuiting the switch element (Qt), and the frequency control circuit (Uf) operates as a starter at least during the period (Ta) during the sweep operation. The inhibition signal (Sk) is activated to activate the switch element (Kt). Then, the charging voltage of the capacitor (Ct) does not reach a predetermined voltage, the switch element (Qt) does not operate, and the discharge lamp starts main discharge during the sweep operation of the frequency control signal (Sf). To prevent. After the sweep operation is completed, the starter operation inhibition signal (Sk) is controlled to be deactivated so that the starter circuit can operate.

With this configuration, it is possible to suppress the main discharge from starting in the discharge lamp (Ld) during the sweep operation and to reduce the probability of the retry of the sweep operation occurring. . In this figure, the case of the external trigger system has been described, but the same applies to a discharge lamp lighting circuit using a series trigger system starter circuit (Ut ') as shown in FIG.

  Another embodiment for carrying out the present invention will be described with reference to FIG. 17 which is a flowchart showing one embodiment of the discharge lamp lighting circuit of the present invention. This figure is an example of a flowchart of a microprocessor program for a part of the operation described based on FIG. 10 to FIG. 14 when the frequency control circuit (Uf) is configured including the microprocessor unit.

  A drive frequency determination flag (SfValid) indicating that the frequency control signal (Sf) corresponding to the resonance frequency of the resonance circuit (Nh) has been determined is first processed when automatic tuning is started assuming that the initial state is FALSE. In block (B10), the highest tuning degree data (DsnMax) indicating the past highest value of the tuning degree signal (Sn) during tuning is set to zero. Further, a frequency control data lower limit value (DsfMin) corresponding to the lower limit frequency of the drive frequency sweep is set for the frequency control data (Dsf) corresponding to the value of the frequency control signal (Sf), and the starter operation inhibition signal ( Sk) is activated and the starter is not operated.

  In the processing block (B11), the lamp voltage detection data (Dsv) is obtained by AD conversion of the lamp voltage detection signal (Sv). In the determination block (B22), it is determined that no arc discharge has occurred in the lamp. The lamp voltage detection data lower limit (DsvMin) that is a threshold value to be compared is compared. If it is determined that arc discharge has occurred, the execution of the automatic tuning sequence is stopped, and the processing block In (B19), the frequency control signal (Sf) is set to 0 to stop the variable frequency oscillator (Vco), and the starter operation inhibition signal (Sk) is deactivated so that the starter circuit can be operated.

  When executing the automatic tuning sequence, the processing block (B12) acquires the tuning level data (Dsn) by AD conversion of the tuning level signal (Sn). In the processing block (B13), when this data is higher than the maximum tuning data (DsnMax) acquired in the past, the data is rewritten with the current tuning data (Dsn), and the optimum frequency control data (DsfOptim) is changed. Rewrite with the current frequency control data (Dsf).

  Next, in the processing block (B14), the current frequency control data (Dsf) value is increased by 1LSB, and the drive frequency is changed. If the frequency control data (Dsf) has not reached the frequency control data upper limit value (DsfMax), the process returns to the processing block (B11), and the loop processing from the processing block (B11) to the determination block (B24) is executed.

  If the frequency control data (Dsf) finally reaches the frequency control data upper limit value (DsfMax), the maximum tuning degree data (DsnMax), which is the maximum during the sweep operation, is determined in the decision block (B24). 13 is compared with the tuning data lower limit (DsnMin), which is a threshold value for determining that no glow discharge has occurred, and if it is determined that glow discharge has occurred, the optimum frequency Assuming that the control signal (Sf) has not been determined, the processing block (B10) is returned to and tuning is attempted from the lower limit frequency. If it is determined that no glow discharge has occurred, it is considered that the tuning has been completed normally, and TRUE is set in the drive frequency confirmation flag (SfValid) in the processing block (B15). The optimum frequency control data (DsfOptim) is actually reflected in the frequency control signal (Sf), and the starter operation inhibition signal (Sk) is deactivated to activate the starter circuit.

  As described above, it is possible to continuously realize the operation at the optimum driving frequency satisfying the resonance condition in the resonance circuit (Nh). However, when it is determined that arc discharge has occurred in the lamp, the lamp voltage detection signal (B26) and the determination block (B26) are stopped so that the operation of the periodic drive circuit (Ug) can be stopped immediately. In order to monitor Sv), the loop processing from the processing block (B17) to the determination block (B26) is continued.

  Another embodiment for carrying out the present invention will be described with reference to FIG. 18, which is a diagram showing a simplified form of one embodiment of the discharge lamp lighting circuit of the present invention. Up to this point, an AC drive type discharge lamp lighting circuit has been described, but this figure shows an example of a DC drive type discharge lamp lighting circuit. Basically, an AC drive type discharge lamp lighting circuit is shown. Since the inverter (Ui) is removed from the above, the present invention operates well even with a DC type discharge lamp lighting device.

  In this figure, the case of the external trigger system has been described, but the same applies to a discharge lamp lighting circuit using a series trigger system starter circuit (Ut ') as shown in FIG.

  Another embodiment for carrying out the present invention will be described with reference to FIG. 19, which is a simplified diagram showing one embodiment of the discharge lamp lighting circuit of the present invention. So far, the embodiment in which the resonance circuit (Nh) is a parallel resonance circuit has been mainly described. However, the discharge lamp lighting circuit of this figure includes a resonance circuit (Nh), a resonance capacitor (Ch), and a resonance inductor (Lh). Is a series resonance circuit in which are connected in series.

  In this embodiment, the inverter (Ui) also serves as the periodic voltage applying means (Uj). Therefore, the periodic drive circuit (Ug) is operated by the sweep operation as described above in the starting sequence of the discharge lamp (Ld). A condition for generating a resonance frequency when the difference between the frequency of the periodic voltage application means (Uj) and the resonance frequency of the resonance circuit (Nh) is minimum, and a periodic voltage application drive from the frequency variable oscillator (Vco) is found. After generating the signal (Sj) and shifting to the steady lighting state, the stationary polarity inversion signal (Srs) is generated, and these signals are respectively the polarity inversion signals selected by the signal selector (Us). (Sr) is input to the inverter (Ui). The signal selector (Us) may be controlled by the frequency control circuit (Uf) that controls the starting sequence, or by the microprocessor unit (Mpu).

  In the drawing, an example in which a series trigger type starter circuit (Ut ′) is used is shown. In this circuit, a high voltage from the resonance circuit (Nh) as an AC power supply is received, and a diode (Dq) is passed through a resistor (Rq) and a primary winding (Pq) of a starter transformer (Tq). While being rectified, the capacitor (Cq) is charged relatively slowly.

  When the charging voltage of the capacitor (Cq) reaches a predetermined voltage, the switch element (Qq) configured by a voltage sensitive element such as a discharge gap is turned on, and the voltage of the capacitor (Cq) A pulse is applied to the side winding (Pq) so that a high voltage pulse is generated in the secondary winding (Hq) of the starter transformer (Tq) and applied to the electrode (E1). To work. The starter transformer (Tq) may be configured such that the secondary winding is divided into two, and high voltage pulses of opposite polarity are applied to both electrodes (E1, E2). Good.

  The present invention exhibits the above-described effects satisfactorily even in such a form. The starter circuit (Ut ') is the same as an external trigger type starter circuit (Ut) as shown in FIG. 18, and the effect of the present invention is irrelevant to the trigger type.

  Further, as shown in FIG. 20, the resonance transformer (Th) is included, the resonance inductor (Lh) is the primary winding (Ph), and the resonance circuit (Nh) is the primary circuit. A side winding (Ph) and the resonance capacitor (Ch) are included, and the inverter (Ui) can be connected to the resonance circuit (Nh) so as to excite series resonance. The present invention exhibits the above-described effects satisfactorily even in such a form.

  Of course, in the case where the resonance circuit (Nh) is a series resonance circuit, the inverter (Ui) is provided as shown in FIG. 21 in addition to the inverter (Ui) also serving as the periodic voltage applying means (Uj). It may be. In the case of the discharge lamp lighting circuit of this figure, the resonance capacitor (Ch) is composed of two capacitors (Ch1, Ch2). Thus, the present invention can obtain the same effect even if the resonance circuit is a series resonance system or a parallel resonance system.

  The circuit configuration described in this specification describes the minimum necessary components for explaining the operation, function, and operation of the discharge lamp lighting circuit of the present invention. Therefore, the details of the circuit configuration and operation described, such as signal polarity, selection, addition, omission of specific circuit elements, or ingenuity such as changes based on the convenience of obtaining elements and economic reasons Is assumed to be performed at the time of designing the actual device.

  In particular, a mechanism for protecting circuit elements such as FETs and other switch elements from damage factors such as overvoltage, overcurrent, and overheating, or generation of radiation noise and conduction noise generated by the operation of circuit elements of the power feeding device Mechanisms to reduce or prevent generated noise, such as snubber circuit, varistor, clamp diode, current limit circuit (including pulse-by-pulse method), common mode or normal mode noise filter choke coil, noise It is assumed that a filter capacitor or the like is added to each part of the circuit configuration described in the embodiment as necessary. The configuration of the discharge lamp lighting circuit according to the present invention is not limited to the circuit system described in this specification.

The block diagram which simplifies and shows the discharge lamp lighting circuit of this invention is represented. The block diagram which simplifies and shows one form of a part of discharge lamp lighting circuit of this invention is represented. The block diagram which simplifies and shows one form of a part of discharge lamp lighting circuit of this invention is represented. The block diagram which simplifies and shows one form of a part of discharge lamp lighting circuit of this invention is represented. The block diagram which simplifies and shows one form of a part of discharge lamp lighting circuit of this invention is represented. 1 represents a simplified configuration of one form of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of one form of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 2 represents a simplified waveform of an embodiment of a discharge lamp lighting circuit of the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. Fig. 2 represents a simplified timing diagram of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 2 represents a simplified flowchart of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 represents a simplified configuration of an embodiment of a discharge lamp lighting circuit according to the present invention. 1 shows a simplified configuration of one form of a conventional discharge lamp lighting circuit.

Explanation of symbols

Adi AD converter Adr Comparator Ads Comparator Ah Tertiary winding And AND gate B01 Entrance block B02 Exit block B10 Processing block B11 Processing block B12 Processing block B13 Processing block B15 Processing block B16 Processing block B17 Processing block B19 Processing block B21 decision block B22 decision block B23 decision block B24 decision block B25 decision block B26 decision block Ch resonance capacitor Ch1 capacitor Ch2 capacitor Cm smoothing capacitor Cmg comparator Cmi comparator Cq capacitor Cr resonance capacitor Cs capacitor Cs' capacitor Ct capacitor Cx smoothing capacitor Dao DA converter Dl Diode Dm Current supply diode Dn Diode D Diode Dsf Frequency control data DsfMax Frequency control data upper limit value DsfMin Frequency control data lower limit value DsfOptim Optimum frequency control data Dsn Tuning degree data DsnMax Maximum tuning degree data DsnMin Tuning degree data lower limit value Dsv Lamp voltage detection data DsvMin Lamp voltage detection data lower limit value Dsz Regenerative diode Dx Flywheel diode E1 Electrode E2 Electrode Et Auxiliary electrode Ff Flip-flop Ffc Flip-flop Fx Feed control circuit G1 Gate drive circuit G2 Gate drive circuit G3 Gate drive circuit G4 Gate drive circuit Gkh Gate drive circuit Gx Gate drive circuit Hq Secondary Side winding Inv Inverter Ix Lamp current detection means Kh Resonance drive switch element Kt Switch element Ld Discharge lamp Lh Resonant inductor r Resonant coil Lx Choke coil Mh Resonant drive power supply Mpu Microprocessor unit Mx DC power supply Nh Resonant circuit Osc Oscillator control unit Ph Primary side winding Pq Primary side winding Pt Primary side winding Pwm PWM signal Pz Primary side Winding Q1 Switch element Q1 'Switch element Q2 Switch element Q2' Switch element Q3 Switch element Q3 'Switch element Q4 Switch element Q4' Switch element Qq Switch element Qt Switch element Qx Switch element Ra Resistor Ra 'Resistor Rc Resistor Rc' Resistor Rd Resistor Rm voltage dividing resistor Rn voltage dividing resistor Rq resistor Rs current detection resistor Rt resistor Ru1 resistor Ru2 resistor Ru3 resistor Sdf frequency data Sdn tuning data Sf frequency control signal Sf1 inverter control signal Sf2 inverter control signal SfValid drive frequency determination Sfc signal Sg gate drive signal Sh secondary winding Si lamp current detection signal Sj periodic voltage application drive signal Sk starter operation inhibition signal Sn tuning signal Snp flat part Sr polarity inversion signal Srs steady polarity inversion signal Ss oscillation signal St 2 Secondary winding Sv Lamp voltage detection signal Sz Secondary winding T31 Node T32 Node T41 Node T42 Node T4a Node T4b Node Ta Period Th Resonant transformer Ti Period Tk Period Tm Period Tn Period Tq Starter transformer Tr5 Transistor Tr6 Transistor Trr Transistor Tt Starter transformer Tu period Tu 'period Tv period Tz Current limit regenerative transformer Uc Inverter control circuit Ud Discharge generation detecting means Uf Frequency control circuit Ug Periodic drive circuit Ui Inverter Ui' Inverter Uj Periodic voltage applying means U Tuning degree detection means Us Signal selector Ut Starter circuit Ut ′ Starter circuit Ut ”Starter circuit Uv Block Uw Block Ux Feed circuit Ux ′ Feed circuit VSf1 Lower limit value VSf2 Upper limit value VSf3 Frequency control signal value VSf4 Frequency control signal value VSfr Optimal frequency control signal Value Vbg Voltage source Vc Reference power source Vcc Reference power source Vco Frequency variable oscillator Vcx Voltage Ve Reference voltage source Vnh Voltage Vref Reference voltage source Vth Threshold voltage Vx Ramp voltage detection means Zh Resonance drive current limiting means ta Time tb Time tc Time tk Time tm time

Claims (5)

A discharge lamp lighting circuit for starting and lighting a discharge lamp (Ld) in which a pair of electrodes (E1, E2) for main discharge are arranged to face each other,
A resonance circuit (U) having a resonance inductor (Lh) and a resonance capacitor (Ch) for increasing the supply voltage to the discharge lamp (Ld) when starting the discharge lamp (Ld) Nh), a periodic voltage applying means (Uj), a periodic driving circuit (Ug) for driving the periodic voltage applying means (Uj), the frequency of the periodic voltage applying means (Uj), and the resonance circuit (Nh) A tuning degree detecting means (Un) for generating a tuning degree signal (Sn) corresponding to the difference from the resonance frequency, and the periodic drive circuit (Ug) oscillates upon receiving an input of the frequency control signal (Sf) In a starting sequence of the discharge lamp (Ld), a variable frequency oscillator (Vco) whose frequency is controlled and a frequency control circuit (Uf) for generating the frequency control signal (Sf) are provided.
The frequency control circuit (Uf) starts from one of the upper limit frequency and the lower limit frequency of the frequency variable oscillator (Vco) while monitoring the tuning degree signal (Sn) and does not exceed the other frequency. A sweep operation is performed to change the frequency control signal (Sf) so that the frequency control signal (Sf) is swept until the frequency control circuit (Uf) has a frequency corresponding to a resonance frequency of the resonance circuit (Nh). A discharge lamp lighting circuit which operates to determine a value of a control signal (Sf) and input the value to the frequency variable oscillator (Vco).   After the sweep operation is completed, the frequency control circuit (Uf) sets the determined resonance frequency of the resonance circuit (Nh) as the value of the frequency control signal (Sf) input to the variable frequency oscillator (Vco). The sweeping is performed over a range narrower than the range corresponding to the lower limit frequency from the upper limit frequency of the frequency variable oscillator (Vco) in the vicinity of the value of the corresponding frequency control signal (Sf). The discharge lamp lighting circuit described.   It further has a discharge generation detecting means (Ud) for detecting whether or not the discharge lamp (Ld) has generated a discharge, and the discharge generation detecting means (Ud) detects a discharge occurrence state before the end of the sweep operation. When this occurs, the frequency control circuit (Uf) interrupts the sweep operation, and then, when the discharge occurrence detection means (Ud) detects a non-discharge occurrence state, the frequency control circuit (Uf) is within the range in which the sweep operation was performed first. 3. The discharge lamp lighting circuit according to claim 1, wherein the sweeping operation is retried from the frequency of the above.   It further has a starter circuit (Ut) for applying a high voltage pulse to the discharge lamp (Ld), and the starter circuit (Ut) is controlled to be operable after the sweep operation is completed. The discharge lamp lighting circuit according to claim 1, wherein: A resonant transformer (Th) having a primary winding (Ph) and a secondary winding (Sh), wherein the resonant inductor (Lh) is the primary winding (Ph); The application means (Uj) is connected to the resonance circuit (Nh) so as to excite parallel resonance, and one end of the discharge lamp (Ld) is connected to one end of the secondary winding (Sh). The discharge lamp lighting circuit according to claim 1, wherein:

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