TW595266B - Lighting circuit and its control method of discharge lamp - Google Patents

Abstract

In the invented lighting circuit of discharge lamp, smoothing capacitor (C2) and a switch (SW3) are serially connected at one terminal of the reactor (L1) discharge lamp (LMP) and converter (COMV). The smoothing capacitor (C2) is disconnected by turning off the switch (SW3) at the initial stage of the discharge lamp (LMP) lighting. When the discharge lamp (LMP) current is cut in the midway, a connection point voltage of the reactor (L1) and smoothing capacitor (C2) is increased to early respond the load variation. At the same time, when the discharge lamp (LMP) current is stable, the switch (SW3) is turned on to insert the smoothing capacitor into the circuit.

Description

595266 V. Description of the invention (0 [Technical Field] The present invention relates to a discharge lamp lighting circuit and a control method for lighting the lamp in order to stabilize the discharge lamp that does not extinguish midway during startup. [Background Art] In the will When the discharge lamp is turned on, for example, as disclosed in Utility Model Publication No. 2 52 93 1 2, first, a high voltage is applied between the electrodes of the discharge lamp by an initiator (ignitor) to cause insulation damage. And make the electrodes be turned on for an instant 'at the same time, by releasing the stored energy (energy) of the capacitors provided between the power supply side and the discharge lamp, a large instantaneous current flows (tens of A / number " S)' From the white light discharge (giow discharge), the arc (arc) is discharged, and then the current flows between the electrodes through the main lighting circuit connected to the power source, and it is converted into a stable arc. At the beginning of this arc discharge, the distance between the electrodes that are short-circuited by the arc (arc discharge distance or arc length) is unstable, so when the discharge distance is long, the voltage between the electrodes rises, and when the discharge distance is short Time, The voltage between the electrodes decreases. When the arc discharge distance is long and the impedance between the electrodes is large, 'Although the voltage between the electrodes is higher than the power supply side voltage (the output voltage of the main lighting circuit)', it is set because There is a time constant in the smoothing reactor and capacitor between the main lighting circuit and the discharge lamp, so that the voltage between the electrodes does not follow the voltage on the power supply side, and the current is extinguished midway. However, the arc discharge distance is short. In the case, the output of the power supply becomes a short-circuit state. There is an overcurrent flowing between the electrodes for a period of time, which causes the electrodes to lose power and causes discharge.

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^ 5266 V. Description of the invention (2) " — ---- can be shortened. Immediately after the overcurrent flows, the medium-to-electrode voltage drops, and the voltage of the capacitor decreases. Therefore, as described above, the current is always off 'and there is a problem of causing no lighting. The energy stored in the initial stage of the lighting is discharged in an instant, so a large current flows between the electrodes, and the electrode is damaged, because this large current generates the electrical vibration of the discharge lamp current, and at the same time It has a bad influence on the surrounding control power, and it causes the problem that the discharge lamp goes out halfway. It is therefore an object of the present invention to provide a discharge lamp lighting circuit and a method for controlling the same that prevent the lamp from being extinguished halfway during the initial lighting period. ^ Another object of the present invention is to provide a discharge lamp lighting circuit and a method for controlling the discharge lamp, which can make the discharge lamp longer. [Summary of the Invention] The discharge lamp lighting circuit of the present invention includes: a switching element that switches a DC power supply voltage; a reactor connected between the switching element and an electrode of one side of the discharge lamp; Capacitor's smoothing capacitor for smoothing; to generate a south voltage from the DC power supply voltage, and apply it to the starter of the discharge lamp; a current measuring device that measures the current flowing through the discharge lamp; A voltage measuring device for applying a voltage to a discharge lamp; a power computing device that uses the above current measuring device and voltage measuring device to calculate the power consumption of the discharge lamp; and the rotation of this power computing device, as necessary As a feedback signal, it is inputted to generate a PWM circuit that outputs pWM pulses that drive the above-mentioned switching elements; wherein a smoothing capacitor and a switching element are connected in series between one end of the discharge lamp side of the reactor and one end of a DC power source. At the beginning of the discharge lamp lighting

Page 5 595266 V. Description of the invention (3) In the period of (3), the smoothing capacitor is removed from the circuit by making the above-mentioned switching element open, so as not to accumulate in the smoothing as in the early stage of lighting. The energy of the capacitor is discharged in an instant to prevent damage to the electrode. At the same time when the current of the discharge lamp is cut off, the voltage of the connection point between the reactor and the smoothing capacitor is increased to respond to the load change earlier. Speed, and after the current flowing through the discharge lamp is stabilized, the switching element is closed, and the smoothing capacitor is inserted into the circuit.

Regarding the control method of the discharge lamp lighting circuit of the present invention, the above-mentioned control method of the discharge lamp lighting circuit is taken as an object. In the initial stage of the discharge lamp lighting, the frequency of the PWM pulse is increased, and after the discharge lamp current is stabilized, To reduce the frequency of the above PWM pulses. Regarding the control method of the discharge lamp lighting circuit of the present invention, the above-mentioned control method of the discharge lamp lighting circuit is taken as an object. When the constant current control is performed at the initial stage of the discharge lamp lighting, the determination of the above-mentioned reactor is determined. Inductance value, duty cycle ratio and frequency of PWM pulses, so that when the above-mentioned switching elements ~ pieces are turned on and off, the current of the above-mentioned reactor continuously flows. Discharge ί = Controlling method of the discharge lamp lighting circuit of the Ming & is the control method of taking the road as the object, in the discharge lamp lighting:

Absence— = i i During the period when the operating voltage is unstable, the above pwm circuit is switched off. 'Control method of feedback control of force and control of the discharge lamp current to a discharge circuit' is to control the above-mentioned reactor peacefully "two :: control method, including the reference for setting the connection point for the electric connection on q Voltage while connected in the above

2146-5182-PF (N) .ptd Page 6 595266 V. Description of the invention (4) When the voltage of the contact is smaller than the above-mentioned reference electricity charge and electricity setting value and the above-mentioned reference, the value is below, but at the above-mentioned connection point voltage To control the drop, the voltage of the power consumption of the discharge lamp is lower than the above-mentioned method. 'Control in the above-mentioned elimination of the discharge lamp of the present invention from the discharge lamp lighting circuit as the control of the lamp circuit at the beginning of the lighting, the application of high control method, insulation between the electrodes, and bow I The method is to perform a thermo-optical discharge from the connection point 2 of the electric lifting and smoothing capacitor of the discharge lamp, and then perform the arc discharge method. Above and below, the control method of the discharge lamp lighting circuit is described from the aspect of the control of the discharge lamp lighting circuit of the present invention. When the initial lighting is included, the reactor and the smoothing capacitor voltage are gradually increased. During this period, by applying a high voltage to the discharge chamber, insulation damage between the electrodes is generated, and the white heat is caused to be converted into an arc discharge by the thermo-optical discharge at the connection point of the reactor and the smoothing valley. [Best Embodiment of the Invention] In order to make the present invention clearer, an embodiment according to the attached drawings. First, FIG. 1 is a diagram showing Embodiment 1 of the present invention. An AC power supply is connected to a direct-k-to-k converter equipped with an AC- and a chop (ch pppp), and a discharge lamp is used. [The case where the lamp current is large at a certain L voltage ^ The set value of the electric power is based on the above method, which is to convert the above-mentioned reactor thermo-optical discharge into electricity by generating electricity between the discharge lamps, which is included in the discharge lamp. The electrode of the electric lamp at the connection point is light-discharged, and then the voltage is used to explain the circuit diagram of the present invention in white. The first DC converter circuit

2146-5182-PF (N) .ptd Page 7 595266 V. Description of the invention (5) CONV, on its output side, the field effect transistor "^^ channel" and the pulse transistor ρτι are connected. However, the pulse The secondary side of the transistor PT1 is connected between the output terminal of the PWM circuit 10 described below and the negative-side output terminal of the converter c0NV, and the secondary side of the pulse transistor PT1 is connected to the transistor FET. Between the gate and source of 1. The diode D1 is connected between the source of transistor FET1 and the negative output terminal of converter c0NV. At the same time, the cathode and anode of this diode D1 The reactor L1, the diode D2, the discharge lamp LMP, and the current measuring resistor R0 are connected in series. The reaction lamp L1 is relatively small between one end of the LMP side of the discharge lamp and one end of the resistor r0. Capacitor C1 is connected, and a series circuit of this capacitor (^, a large-capacity smoothing capacitor C2 (C1 < C2)) and switch SW3 is connected in parallel. Although not shown, a buffer can also be used. A snubber resistor 'is connected in series to the capacitor C1. On the series circuit of the capacitor C 2 and the switch SW 3, Resistance for voltage division

The series circuits of R1 and R2 are connected in parallel, and the capacitor C3 is connected in parallel to the resistor R2. The high voltage drive switch Sfi and the series circuit of the resistor and the capacitor are connected between the drain of the transistor FET1 and the negative output of the converter C0NV, and on both ends of the capacitor C4, a switching element (SIDAC 4DIAC The two-way thyristor (SSD) and the primary coil of the high-voltage transformer 1 as a starter are connected in series. On the primary side of this high-voltage transformer TF1, a capacitor C5 is connected through the diode D3, and on both ends of this capacitor C5, the above-mentioned discharge lamp LMP is connected.

2146-5182-PF (N) .ptd

Page 8 595266 V. Description of the invention (6) — Here, the converter c0NV, high-voltage drive switch SW1, resistor R3, electric @OFF t1 SSD, high-voltage transistor m, diode ⑽, and capacitor C5 constitute A high-voltage DC-DC conversion circuit in order to cause insulation damage between the electrodes of the discharge lamp Up at the initial stage of lighting. The connection point i between the electric valley C1 and the resistor r0 is connected to one terminal of the resistor R6 through the current amplifier AMP, and the connection Ϊ 爻 L of the resistor ^ and the capacitor 被 is connected to the-terminal of the comparison circuit CMP. Here, the resistor R6 and the electric U 2 are divided into circuits. ❿The other-terminal of the comparison circuit CMP is connected to the reference voltage E1. The comparison circuit comp. The circuits from SW4 and SW5 are used to control the start-up training. The input signal 'amplified β AMP' is input as the current value t. On the input terminal, the anode is connected to the above-mentioned partial voltage ^ two points: the cathode of the body D4, and the cathode of the anode body D5 with a pseudo-base R = 2 = E2 is connected to this anode._ The output voltage of D5 is the voltage value v. In the electric power calculation, please use the current value ί and the electric value MV as input to calculate the force of the discharge lamp _ and input it to the inverse *, F / B of the PWM circuit 10 through the resistor R11 ′. In the PWM circuit 10, the value of the electric power which is fed in by feedback is one, and the value of the sub-value is used to control the pulse width or duty cycle (du) to generate a PWM pulse. At the time of the above-mentioned pulse transistor pn, the PWM pulse is produced. The above is turned on. However, the feedback input terminal f / b ground of the PWM circuit 10 is, as described later, by turning on the switch SW4 through the switch SW4 at the initial stage of lighting.

595266

This causes the power feedback control of the PWM circuit 10 to fail to operate. On the PWM circuit 1 〇, Rft ^ 嫂 + motor limit benefit input terminal CL, the above resistance n is connected through resistor R4, and between the input terminals: resistor R5 and capacitor C6. Parallel circuits are connected. In order to determine the frequency of the pfM pulse, the resistors R9 and R10 are connected to the PWM circuit 10, and a switch sw5 is connected between the resistor R10 and the ground. By turning on and off the switch SW5, the combined resistance value of the resistors R9 and R10 is changed. As a result, the time constant of the capacitor ⑶ is changed, and the frequency can be changed. V. Description of the invention (7) The SW 2 is a switch for slow start. The resistors R7, R8, and capacitor C7 are time constant components used to make the PWM pulse turn-on pulse width smaller at the initial stage of lighting to prevent the slow current from starting from the burst current to the capacitor c. Next, the operation of this embodiment will be described with reference to FIG. 5. First, at time ti in Figure 5, once the high-voltage drive switch sw 1 is turned on, the oscillating circuit formed by the primary coil of the resistor R3, capacitor C4, thyristor SSD, and high-voltage transistor TF 1 is driven. Through the diode D3 on the secondary side of the transistor TF1, the voltage VI of the capacitor C5 rises. Here, the switches SW4 and SW5 are turned on from time tQ, and the switches SW3 are turned off. At time t2 when the voltage VI reaches, for example, 5 kV, the insulation of the discharge lamp LMP is broken and the white light photo-discharge current ιΜρ starts to flow. After that, at time t3, SW2 is turned on, and a PWM pulse is output from the PWM circuit 10, and this pulse is applied to the primary side of the pulse transistor ρτ1. borrow

2146-5182-PF (N) .ptd Page 10 595266 V. Description of the invention (8) A pulse voltage is generated on the secondary side of this 'pulse transistor PT 1 and is applied to the gate and source of the transistor FET1' Therefore, the transistor FET1 starts to perform a switching operation. By this, through the reactor L1, on the resistance pi and the series circuit therewith, the current starts to flow, and the voltage V2 on the anode side of the one pole M starts to increase. This voltage V 2 is, for example, picked up at a time. As soon as the white light photodischarge voltage (for example, 200 to 350V) is reached, it causes white light photodischarge, and then turns into arc discharge, and the current IUP increases rapidly all the time. At this time, the 'switch SW3 is turned off as usual, and the capacitor C2 is not connected to the reactor [1's output side], but only ci is connected. At present, when changing from white light discharge to arc discharge, the flying position of the arc between the electrodes is not stable, and if it is cut off midway in an instant, this is the case. If the terminal voltage of the electric eC1 before the arc is cut off halfway is V2, if the energy stored in the reaction line L1 is stored by the current until the arc is cut off halfway, the circuit loss is ignored and it moves to the capacitor c 丨Therefore, the terminal voltage V2 of the capacitor C1 is roughly expressed as' V2 = νΛ {(Ll / Cl) Ilmp2} + V2 ,. As described above, at the initial stage of lighting, the capacitor C2 is removed from the circuit, and because the capacity of the capacitor C1 is small, the above-mentioned voltage V2 becomes a maximum value. It is assumed that even if the discharge lamp LMP is turned off midway in an instant, then V2 increases and then Arc discharge begins. And because the capacity of the electric valley C 1 is very small, the accumulated energy to the capacitor c 1 also becomes small. When the arc discharge restarts, even if the energy is discharged, the current flowing through the LMP of the discharge lamp 2 will not cause an overcurrent. Don't worry about electrode damage

595266 V. Description of Invention (9) Injury. The voltage between the electrodes of the discharge current of the capacitor C 1 has risen a little bit.]: The intermediate voltage has risen back to the voltage V2, and there is no halfway again. However, although the capacitor C1 can be omitted, the load current is very small at the initial stage of lighting. As for the high-voltage driving circuit of the capacitor, in order to remove the noise or ripple interference (rippie) contained in the voltage V2, the capacitor port is yes, then the switch SW3 is turned on, and the capacitor ㈡ is inserted into the circuit / = valley Cl, C2 The combined capacitance becomes a good smoothing action for the voltage V2. In the initial stage of the arc discharge, even if the voltage between the electrodes of the discharge lamp LMp drops sharply, it is appropriate to continuously supply the current [M?]. Set the inductance value of the reactor Li or the frequency of the pwM pulse and the duty cycle ratio when the t is turned on. It is hoped that the energy accumulated in the reaction L1 when the PWM pulse is turned on can be maintained until the next turn on. The current iLMp of the discharge lamp LMP is input to the current limiter input terminal of the pWM circuit 10 through the resistor R4 (^, at the initial stage of the lighting, the PWM circuit 10 performs pulse width control to make the discharge lamp LMP operate at a constant current to So that the current Ilmp does not exceed the limit value of Fig. 5. In this way, once the current 込 ㈣ of the discharge lamp LMP stabilizes at the limit value L, then at time Ϊ 5 'the comparison circuit COMP operates and the high-voltage drive switch SW1 is turned off' in the arc discharge After the time t6 when the current ILMP is stable, a relatively large-capacity capacitor c2 is turned on by turning on the switch SW3 ′ to the output side of the reactor L1 to perform the smoothing of the voltage V2.

595266 V. Description of the invention (10) At time I: 5 ', the switches SW4 and SW5 are turned on. Among them, the switch “SW5” is turned on, and as described above, at the initial stage of lighting, a higher frequency of the PWM pulse is set, thereby helping to keep the voltage V2 at the time when the current of the discharge lamp goes out in the middle. Early rise. In order to reduce the switching frequency of transistor FET1 after the arc discharge has stabilized,

To reduce the switching loss, the switch SW5 is closed and the resistor R10 is removed to reduce the frequency of the pwM pulse, that is, the switching frequency of the transistor FET1i. The timing of turning off the switch SW5 may be, for example, after the timing (time%) of turning on the switch SW3. On the other hand, the switch SW4 is used to control the discharge lamp LMP indefinitely at the initial stage of lighting, and the switch for constant current control is turned off after time%, for example, after t7 '. This switch is turned on until t? In advance, because the voltage V2 (its divided voltage value V3) is unstable at this time, and the power value fed back to the PWM circuit 1G changes greatly, because this has a large impact on the pwM pulse , So enter the feedback as $. That is to say, during this period, the above-mentioned becomes constant current control. After time t7, the switch SW4 is turned off, and the output signal of the computing power and the feedback signal of the expected power are input to the PWM circuit 10.懕 F?: = Must: The idea is that after transferring from constant power control, the reference power i Αν * 体 D5 '' is often input to the arithmetic circuit 0p, and when the voltage (〃 'voltage value V3) is greatly reduced, Iwp does not increase extremely. Example 1 Set the power consumption of the discharge lamp LMP to Ϊ 20 20 circuit of 20W and set ^ " Let's set the reference voltage E2 at 60V in advance, even if the input voltage of the calculation circuit OP is greatly reduced by 3 In the root 2146-5182-PF (N) .ptd Page 13 595266 V. Description of the invention (11) According to the reference voltage E2 of 60V, the current ILMP does not exceed 2A. It is also assumed that even if the voltage V2 becomes equal to or higher than the reference voltage E2, since the power consumption of the discharge lamp LMP can be limited to 120 W by the arithmetic circuit oop, there is no need to worry about damaging the discharge lamp LMP. 'As above' According to this embodiment, by removing the capacitance from the circuit at the initial stage of lighting as described earlier, and the high-frequency switching of transistor FET1 4 'Even if the arc is in an unstable state, because the voltage is established early y 2 and the current of the discharge lamp is continuously supplied, so that it is possible to surely prevent the non-lighting from being stopped due to the current midway, and to prevent the loss of the electrode due to the overcurrent. In short, in this embodiment, the switch SW1 is turned on. By applying a high voltage V1 between the electrodes of the discharge lamp LMP at the initial stage of the discharge lamp evaluation, an insulation discharge occurs between the electrodes and an arc discharge is caused. When the switch is turned on, the voltage V2 at the connection point between the reactor L1 and the smoothing capacitor C2 rises and changes from white light discharge to arc discharge. Therefore, the current ILMP is gradually increased from time 1: 2 in FIG. 5. Therefore, when switching to arc discharge ', there is no need to worry about excessive sudden current flowing into the discharge lamp LMp, and there is no need to worry about generating noise due to large current. ° Figure 2 is a modified example of the circuit in Figure 1. The field effect transistor FET2 and diode D6 are used to implement the switch SW3 in Figure i, and a bipolar transistor can also be used. TR1 and resistor R12. However, the operation of this embodiment is basically the same as that of the circuit in Fig. 丨, so the description is omitted. Next, Fig. 3 is a circuit diagram showing a second embodiment of the present invention.

2146-5182-PF (N) .ptd Zhe < page 14 595266 V. Description of the invention (12) The same reference numerals are attached to the same components as in Figs. 1 and 2. In this embodiment, the high-voltage drive switch SW1 in Figs. 1 and 2 is removed, and one end of the resistor R3 is connected to the output side of the reactor L1. The other structures are the same as those in Fig. 1. In this embodiment, an element with a lower operating start voltage is used as the switching element SSD. On the other hand, the output-side voltage V 2 of the reactor [1] is gradually increased, and the white light discharge is converted into an arc discharge. The operation of this embodiment will be described below along FIG. 6. First, adjust the time constant for slow start according to the resistors R7, R8 and capacitor C7, and set the ON pulse width of the output of the PWM circuit 10 to be shorter. The transistor FET1 is switched by turning on the start switch SW2 so that the voltage V2 gradually increases from time t !. In addition, the time constant according to the resistance 3 and the valley C 4 is appropriately set. For example, when the time & voltage v 2 reaches 150 V, if the switching element SSD starts to operate in advance, the switching element is included after time Ϊ2. The operation of the oscillation circuit of the SSD starts, and the voltage V1 of the discharge lamp LMp increases sharply all the time. In the same manner as in the case of FIG. 5, the insulation is destroyed from the moment when the voltage v 1 reaches, for example, 5 kV, and a white light discharge is started, and the voltage VI decreases. At this time, the voltage V2 has not reached the white-hot 'photodischarge voltage. After that, at a time t when the voltage V2 reaches, for example, 20 to 350 V, a white light discharge is caused, and the arc discharge is quickly turned. 4 Although not shown, the timing of turning on or off the switches SW3 and SW4 is the same as in Figure 5. After the current ILMP is stabilized, the switch SW3 is turned on, and the capacitor C 2 is input to the output side of the reactor L 1. Turn off switch sW4,

2146 * 5182-PF (N) .ptd Page 15 595266 V. Description of the invention (13) Switched to constant power control. Regarding the switch SW 5, the frequency of the PWM pulse can be increased by turning it on at the initial stage of lighting, as shown in FIG. 5, and then closing the switch to reduce the frequency. In this embodiment, at the initial stage of lighting the discharge lamp LMP, the voltage V2 at the connection point between the reactor L1 and the smoothing capacitor C2 is gradually increased, and a high voltage V1 is applied between the electrodes of the discharge lamp LMP during this period. In order to cause insulation damage 'and cause white light photodischarge, the discharge lamp LMP is then changed from white light photodischarge to arc discharge. Therefore, as shown in FIG. 6, since the incandescent photodischarge current flows out from time t3 and turns into an arc discharge current at the current IL M of the discharge lamp LMP, it is transferred to the same as in FIG. 5. At the time of arc discharge, there is no need to worry about excessive sudden current flowing into the discharge lamp LMp, so there is no fear of noise due to large current. Next, Fig. 4 shows a third embodiment of the present invention. This embodiment is an embodiment in which the discharge lamp LMP 'is turned on by a high-voltage pulse. In Figure 4, between the connection point of the diode D3 and the capacitor C5 connected to the secondary side of the high-voltage transistor TF1 and one end of the discharge lamp LMP, the primary coil and the varistor of the high-voltage transistor TF2 (Varistor) SG1 is connected in series. The secondary coil of this transistor TF2 is connected in series between the output side of the inverter L1 and the other end of the discharge lamp LMp. However, α0 is a by-pass capacitor for high-voltage pulses, and other structures are roughly the same as those in FIG. 3. The operation of this embodiment will be described with reference to FIG. 7. First, the start switch SW2 is turned on at time ti. However, from the beginning, the switch SW3 is turned off, and the switches SW4 and SW5 are turned on. 〇

After the time t〗, φ θ # p p τ to grasp i + electric sun solar FET1 straw by the ancient fighting sound of the pulse transistor PT1 ίΓί. With this, the voltage V2 starts to increase, and the voltage at the connection point of the second electric valley C4 reaches the switching s electric voltage, which switches the plant Mη »Qiu W begins Β 曰 TF], M opens, and starts to oscillate, and passes through the high voltage Electricity: & J-1. Capacitor C5 is charged. The voltage of this capacitor C5 exceeds the operating voltage of the varistor SG1, that is, as shown in Fig. 7, a pulse current flows on the primary side of the thyristor TF2. At time t2 immediately after the high-voltage piezoelectric crystal TF2 is turned on, the insulation between the electrodes is broken ', and after time h, the current ILMP starts to flow through the discharge lamp LMP. At this time, the flying position of the arc between the electrodes of the discharge lamp LMP is not stable, and even if the arc is cut off halfway, it is the same as above because the capacitor C2 is removed from the circuit, so the capacity of the circuit C1 is small. , The voltage V2 increases immediately, so the arc restarts momentarily, and the current Iyip then flows. Therefore, there is no need to worry about the discharge lamp LMP going out halfway. After time t2, the voltage of the integrating circuit formed by the resistor R6 and capacitor C9 on the input side of the comparison circuit coMP gradually rises. Once this voltage exceeds the reference voltage E1, the output of the comparison circuit coMP becomes the high level. Bit, and the states of switches SW3, SW4, and SW5 are reversed. That is, since the switch SW 3 is turned on from time t3, and the capacitor C2 is inserted on the output side of the reactor L1, the voltage V2 is smoothed, and by the switch SW4 being closed, according to the power calculation circuit 0P The fixed power control is started, and by turning off the switch SW 5, the frequency of the PWM pulse is reduced, and it turns to the normal state. In this way, even in this embodiment, it is possible to prevent

2146-5182-PF (N) .ptd Page 17 595266 V. Description of the invention (15) The discharge lamp goes out halfway, and at the same time is limited by the small capacity of capacitor C1, or the current limiter is activated at the beginning of lighting. Discharge lamp current, etc., without worrying about excessive current flowing on the discharge lamp LMP and damaging the electrodes. However, in the above-mentioned embodiment, although the case where the lighting is performed by a high-voltage DC voltage or a pulse voltage has been described, the lighting may also be performed by an AC voltage of an inverter. As described above, according to the present invention, it is possible to sorrow the arc instability at the initial stage of lighting. By establishing the voltage applied to the discharge lamp early and increasing the response speed to load changes, the arc discharge continues to flow. A current is applied to release the discharge lamp from being extinguished midway to achieve a stable lighting state. Since no excessive current flows through the discharge lamp, the electrode can be prevented from being worn out, and the life of the discharge lamp can be greatly extended. In addition, even in the circuit structure, compared with the conventional lighting circuit, there is no major factor of complexity, so there is no need to worry about increasing manufacturing costs.

595266 Brief Description of Drawings Figure 1 is a circuit diagram showing the first embodiment of the present invention. Fig. 2 is a circuit diagram showing a modification of the first embodiment of the present invention. Fig. 3 is a circuit diagram showing a second embodiment of the present invention. Fig. 4 is a circuit diagram showing a third embodiment of the present invention. Fig. 5 is an operation waveform diagram showing the first embodiment of the present invention. FIG. 6 is an operation waveform diagram illustrating the second embodiment of the present invention. Fig. 7 is an operation waveform diagram showing the third embodiment of the present invention. [Symbol description] A C parent current power supply, CONV converter, FET1, FET2 field effect transistor, PT1 pulse transistor, TF1 high voltage transformer,

Dl, D2, D3, D4, D5, D6 diodes,

Cl, C2, C3, C4, C5, C6, C7, C8, C9 capacitors, L1 reactors, SSD switching elements,

El, E2 reference voltage, 0P power calculation circuit, COMP comparator, LMP discharge lamp,

Rl, R2, R3, R4, R5, R6, R7, R8, R9, RIO, R11 resistors, SW1, SW2, SW3, SW4, SW5 switching elements,

2146-5182-PF (N) .ptd page 19 595266 Simple illustration of the diagram 10 PWM circuit mi 2146-5182-PF (N) .ptd page 20

Claims (1)

5 releases f month γ%: jE '^ Case No. 91120563_13 仏 月 巧巧 修 #_ VI. Patent application scope 1. A discharge lamp lighting circuit includes: a switching element to switch a DC power supply voltage; a reactor, It is connected between this switching element and one electrode of the discharge lamp. The capacitor for smoothing is used to smooth the pulsating current due to the reactor. The starter is applied to the discharge lamp to generate a high voltage from the DC power supply voltage. The current measuring device measures the current flowing through the discharge lamp; the voltage measuring device measures the voltage applied to the discharge lamp; the electric power computing device uses the above current measuring device and voltage measuring device to calculate the discharge lamp Power consumption; and a PWM circuit, the output of this power computing device is input as a feedback signal according to necessity to generate a PWM pulse that drives the switching element; and is characterized in that: The smoothing capacitor and the switching element are connected in series between one end and one end of the DC power supply. The switching element becomes an open circuit, and the smoothing capacitor is removed from the circuit, and when the current of the discharge lamp is cut off in the middle, the voltage at the connection point between the reactor and the smoothing capacitor is increased, so that the load variation can be reduced earlier. In response to the speed, and after the current flowing through the discharge lamp is stabilized, the switching element is closed, and the smoothing capacitor is inserted into the circuit. 2. —A control method of the discharge lamp lighting circuit, which is used for applying for 2146-5182-PFl (N) .ptc Page 21 595266 --- ^-911205 ^ _ year, month, day amend 6. The scope of patent application for the discharge lamp lighting circuit described in item 1 above, in which the discharge lamp In the initial lighting period, the frequency of the PWM pulse is increased, and after the discharge lamp current is stabilized, the frequency of the PWM pulse is reduced. 3. A control method for a discharge lamp lighting circuit, which is used in the discharge lamp lighting circuit as described in the scope of item 1 of the patent application, wherein, when the constant current control is performed at the initial stage of the discharge lamp lighting, Determine the inductor value, duty cycle ratio and frequency of the PWM pulses so that the current in the reactor continuously flows when the switching element is turned on and off. 4. A control method for a discharge lamp lighting circuit, which is used in the discharge lamp lighting circuit as described in item 1 of the scope of patent application, wherein during the initial period of the discharge lamp lighting operation period and the operating voltage of the discharge lamp is unstable The above-mentioned pwM circuit does not perform feedback control of power consumption, but controls the discharge lamp current to a certain current. 5. · A control method for a discharge lamp lighting circuit, which is used in the discharge lamp lighting circuit as described in item 1 of the scope of patent application, wherein a reference voltage is set for the connection point of the reactor and the smoothing capacitor, In the case where the voltage at the connection point is smaller than the reference voltage, the set value of the power consumption of the discharge lamp and the reference voltage are used to control the discharge lamp current below a certain value, but the voltage at the connection point is higher than the reference voltage In a large case, the power consumption of the discharge lamp is controlled below the above-mentioned set value of the power consumption. 6-A control method for a discharge lamp lighting circuit, which is used in the discharge lamp lighting circuit as described in item 1 of the scope of patent application, wherein a high voltage is applied to the discharge at the initial stage of the discharge lamp lighting. Between the electrodes of the lamp 2146-5182-PFl (N) .ptc Page 22 595266 η VI. Patent application scope Insulation damage between the electrodes, causing and smoothing the connection point of the capacitor for "electricity" to cause the above reactor to perform arc discharge. &Amp; 上幵, and switched from incandescent light discharge to 7.-A control method of the discharge lamp lighting circuit, used for: The discharge lamp lighting circuit described in the round! Item ..., in the discharge application month special ",, During the initial stage of the lamp, the pressure at the connection point between the reactor and the smoothing capacitor is gradually increased. During this period, high voltage is applied to the electricity between the discharge lamps to cause insulation damage between the electrodes, which causes White light photodischarge. The voltage at the connection point between the reactor and the smoothing capacitor is used to convert the heat light discharge into an arc discharge. Let k white 2146-5182-PFl (N) .ptc Page 23