JPH10326691A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device to make high frequency lighting of a discharge lamp, in which a malfunction is prevented such as to output an abnormality sensing signal in association with changing input voltage of a high frequency conversion part or a changing duty of a switching element. SOLUTION: An inverter circuit converts the voltage obtained by rectifying AC power v1 into high frequency v3 and supplies it to a discharge lamp LAMP, and the voltage V4 in the DC separation part 6 of the inverter circuit is sensed and compared with the reference voltage V6 so that any abnormality in the discharge lamp is sensed. In this discharge lamp lighting device, a means is furnished to correct the change in the output voltage V5 of the sensing part 7 relative to the voltage change in the DC separation part 6 if the discharge lamp operates normally.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for illuminating a discharge lamp at a high frequency, and more particularly to an abnormality detection of a discharge lamp.

[0002]

[Prior art]

(Conventional Example 1) Conventional Example 1 will be described with reference to FIGS. In the conventional example 1, when the lamp becomes emiless at the end of the lamp life (in a state where the number of emitters as thermionic emission material of the filament is reduced), the discharge lamp generates a half-wave discharge, and the difference between the maximum value and the minimum value of the lamp voltage vla. Is higher than normal, and the abnormality of the discharge lamp is detected.

Hereinafter, the circuit configuration will be described. The lighting device includes an input AC power supply unit 1 such as a commercial power supply having an AC voltage v1, a rectifying unit 2 such as a diode bridge for rectifying the AC voltage, a smoothing unit 3 including an electrolytic capacitor C1, and a switching element. A high-frequency converter 4 including Q1 and Q2, a load 5 including an inductor L1, a capacitor C2, and a discharge lamp LAMP, a DC separator 6 including a capacitor C3, diodes D1 and D2, capacitors C4 and C5, a resistor R1, Detector 7 composed of R2 and R3
A reference voltage section 8 for generating a constant DC reference voltage V6;
It comprises a discharge lamp abnormality detection circuit section 9 and a switch control section 10. The discharge lamp abnormality detection circuit unit 9 includes, for example, a comparator, and detects a detection voltage V5 output from the detection unit 7.
Outputs a low-level signal if is lower than the reference voltage V6, and outputs a high-level signal if is higher than the reference voltage V6.

The detecting unit 7 detects the difference vla (pp) between the maximum value vla (max) and the minimum value vla (min) of the voltage vla applied to the discharge lamp by a series circuit of the capacitor C4 and the diode D1. The voltage v applied to the discharge lamp
When la is negative, the diode D1 conducts, so that the capacitor C4 is charged to vla (min). When the voltage vla applied to the discharge lamp becomes positive, the diode D1 becomes non-conductive, so that the voltage V4 at the connection point between the capacitor C4 and the diode D1 becomes the voltage Vv already charged in the capacitor C4.
Since the sum of la (min) and the positive voltage vla is obtained, the maximum value of the voltage V4 is vla (pp) = | vla (max) |
+ | Vla (min) |.

[0005] When the discharge lamp is normal, the lamp equivalent resistance is constant, so that LCR resonance including the resistance always occurs. Therefore, the diode D1,
The detection voltage V5 obtained by dividing the envelope of vla (pp) obtained by D2, the resistors R1, R2, R3, and the capacitor C5 is given by:
It becomes lower than the reference DC voltage V6. Therefore, the output of the discharge lamp abnormality detection circuit section 9 becomes Low level.

Next, when a negative half-wave discharge occurs in the discharge lamp with one-sided emission, the lamp current ila flows when the voltage vla applied to the discharge lamp is negative, and the lamp equivalent resistance has a certain value. However, when the voltage vla applied to the discharge lamp is positive, the lamp current ila does not flow, and the lamp equivalent resistance becomes infinite. Therefore, the resonance becomes strong, and the capacitor C2
Since the voltage vla at both ends becomes large, vla (pp)
Also increases. Therefore, the detection voltage V5 is equal to the reference DC voltage V6.
Higher, and the output of the discharge lamp abnormality detection circuit section 9 becomes High.
h level.

(Conventional Example 2) Conventional Example 2 will be described with reference to FIGS. FIGS. 22 and 23 show a circuit configuration of the second conventional example. The lighting device includes an input AC power supply unit 1 such as a commercial power supply having an AC voltage v1, a rectifying unit 2 such as a diode bridge for rectifying the AC voltage, a smoothing unit 3 including an electrolytic capacitor C1, and a switching element. Q
1 and Q2, and an inductor L1,
A load portion 5 including a capacitor C2 and a discharge lamp LAMP;
DC separation unit 6 including a capacitor C3 and resistors R2 and R
3, a reference voltage section 8 for generating a constant DC reference voltage V6, a discharge lamp abnormality detection circuit section 9, and a switch control section 10. The second conventional example utilizes the fact that the lamp has a rectifying action when the lamp becomes one-sided at the end of the lamp life, and that the voltage of the capacitor C3 of the DC separator 6 is different from the normal state.

FIG. 24 shows the switching timing of the switching elements Q1 and Q2. Hereinafter, the duty ratio given by the following equation is defined as Duty. Duty = (T1 / (T1 + T2)) (1) Next, the operation of Conventional Example 2 will be described. When the lamp is normal, the lamp has no rectification effect, and the inductor L1, the capacitor C2, the lamp resistance when the capacitor C3 is charged, and the inductor L1, when the capacitor C3 is discharged.
The capacitor C2 and the lamp resistance are the same, and the voltage V4 of the capacitor C3 is equal to the voltage V2 of the capacitor C1 and Dut.
It can be expressed by the following equation using y. V4 = V2 × Duty (2) Accordingly, the output V5 of the detection unit 7 is a value obtained by dividing the voltage V4 of the capacitor C3 by the resistors R2 and R3, and is given by the following equation. V5 = V2 × Duty × (R3 / (R2 + R3)) (3) The output V5 of the detector 7 is within the range of the reference voltage V61 set above the reference voltage V6 and the reference voltage V62 set below. , The output of the abnormality detection circuit unit 9 becomes Low level.

FIG. 25 shows waveforms at various points during half-wave discharge.
Only the charging current to the capacitor C3 flows through the lamp, and the above equation (2) does not hold. Therefore, the output V of the detection unit 7
5 also rises above the reference voltage V61 set above the reference voltage V6. Then, the output of the abnormality detection circuit unit 9 becomes High level. When the other filament of the lamp becomes abnormal, the output V5 of the detecting section 7 falls to become equal to or lower than the reference voltage V62 set below the reference voltage V6, and the output of the abnormality detecting circuit section 9 becomes High level. Becomes

FIG. 26 shows waveforms at various parts when the duty ratio is increased. As shown in equation (3), the output voltage V5 of the detection unit 7 changes with the duty, and as a result,
Although the lamp is normal, the output V5 of the detection unit 7
Exceeds the reference voltage V61 set above the reference voltage V6, and the output of the abnormality detection circuit unit 9 becomes High level. Similarly, when the duty is reduced, the output V5 of the detection unit 7 is set to the reference voltage V6 set below the reference voltage V6.
2, the output of the abnormality detection circuit unit 9 becomes High level. A similar problem occurs when the output voltage V2 of the smoothing unit 3 changes.

(Conventional Example 3) Conventional Example 3 will be described with reference to FIGS. 27 to 30 (see Japanese Patent Application Laid-Open No. 1-167986).
FIGS. 27 and 28 show the circuit configuration of the third conventional example. The lighting device includes an input AC power supply unit 1 such as a commercial power supply having an AC voltage v1, a rectifying unit 2 such as a diode bridge for rectifying the AC voltage, a smoothing unit 3 including an electrolytic capacitor C1, and a switching element. A high-frequency converter 4 composed of Q1 and Q2, a load 5 composed of an inductor L1, a balancer L2, capacitors C21 and C22, discharge lamps LAMP1 and LAMP2, a DC separator 6 composed of a capacitor C3, diodes D11 and D12, resistors R11, R2
, R12 and R22, and a diode D
2, D3, operational amplifiers OP1, OP2, Zener diodes ZD1, ZD2, resistors R3, R4, capacitor C4
Lamp abnormality detection circuit unit 9 comprising a switch control unit 1
0.

Next, the operation will be described. When the lamp is normal, both LAMP1 and LAMP2 show the same characteristics, so that the lamp voltages vla1 and vla2 have the same value.
Therefore, the absolute value Va of the difference between the lamp voltages vla1 and vla2 expressed by the following equation becomes zero. Va = | vla1−vla2 | (4) As a result, the output of the abnormality detection circuit unit 9 including the differential detection circuit including the operational amplifiers OP1 and OP2 becomes Low level. Even if the duty ratios of the switching elements Q1 and Q2 are changed, the lamp voltages vla1 and vla2 change at the same time, so that the output of the abnormality detection circuit section 9 remains normal and no malfunction occurs.

Referring to FIG. 29, an operation when an abnormality occurs in one of the lamps LAMP1 will be described. When ila1 becomes a half-wave discharge, a no-load LC resonance occurs temporarily, so that the lamp voltage vla1 increases. As a result, V in equation (4)
a increases. If this state continues and exceeds the time determined by the resistors R3 and R4 and the capacitor C4, the output of the discharge lamp abnormality detection circuit section 9 goes high.

Next, both lamps LAM will be described with reference to FIG.
The operation when a one-sided Emiless lamp abnormality occurs in the same direction in both P1 and LAMP2 will be described. Lamp LAMP
1 and LAMP2 generate one-sided emires in the same direction, so that the lamp voltages vla1 and vla2 have the same waveform.
Therefore, Va in equation (4) becomes zero. As a result, the output of the discharge lamp abnormality detection circuit 9 remains at the low level,
A malfunction will occur.

[0015]

In the prior art 1, since the high-frequency lamp voltage is directly detected, the diode and the capacitor of the detecting section need to operate at high speed. Further, since a high voltage is directly applied at the time of starting the discharge lamp, high withstand voltage is required. In order to satisfy these demands, expensive elements must be used for the detection unit. In the second conventional example, when the rectified DC voltage and the duty ratio are changed, there is a problem that a malfunction occurs in which an abnormal detection signal is output even though the lamp is normal. In Conventional Example 3, a plurality of parallel-lit lamps are required to compare lamp voltages. Therefore, it cannot be used for a discharge lamp lighting device that lights one lamp or a plurality of lamps in series. Further, the lamps to be compared need to have the same characteristics. Further, when the same lamp abnormality occurs in the lamps being compared, there is a problem that a malfunction occurs.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and converts a rectified voltage of an AC power supply to a high frequency and detects a voltage of a DC separation section in an inverter circuit for supplying the discharge lamp with a reference voltage. In a discharge lamp lighting device that can detect the abnormality of the discharge lamp by comparing with
An object of the present invention is to prevent a malfunction that outputs an abnormality detection signal in response to a change in the input voltage of the inverter circuit or a change in the duty of the switching element.

[0017]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, an input AC power supply v1 and a rectifying unit 2 for rectifying the input AC power supply v1.
A high-frequency converter 4 that converts the output voltage of the rectifier 2 into a high-frequency voltage v3; a DC separator 6 that separates a DC component from the output v3 of the high-frequency converter 4; A load unit 5 including a discharge lamp LAMP, a control unit 10 of a high-frequency conversion unit 4, a detection unit 7 for detecting a voltage V4 of a DC separation unit 6, a reference voltage generation unit 8 for generating a reference voltage V6, In the discharge lamp lighting device having the means 9 for detecting abnormality of the discharge lamp from the output voltage V5 of the unit and the reference voltage V6, when the discharge lamp is normal, the output voltage of the detection unit 7 with respect to the voltage fluctuation of the DC separation unit 6 It is characterized by having a means for correcting the fluctuation of V5.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment corresponding to claim 1 of the present invention is shown in FIG.
It will be described based on. This lighting device includes an input AC power supply unit 1 composed of an AC voltage v1 such as a commercial power supply, and a rectifying unit 2 such as a diode bridge for rectifying the AC voltage.
A smoothing section 3 composed of an electrolytic capacitor C1, a high-frequency converting section 4 composed of switching elements Q1 and Q2, a load section 5 composed of an inductor L1, a capacitor C2 and a discharge lamp LAMP, and a DC separating section 6 composed of a capacitor C3. A detection unit 7 including variable impedances VR2 and VR3,
It comprises a reference voltage section 8 having a constant DC voltage V6, a discharge lamp abnormality detection circuit section 9, and a switch control section 10. The discharge lamp abnormality detection circuit unit 9 is configured by, for example, a window comparator, and outputs a Low level signal when the output voltage V5 of the detection unit 7 is within a range between threshold values V61 and V62 set above and below the reference voltage V6. , Hi if out of range
gh level signal is output.

FIG. 2 shows the switching timing of the switching elements Q1 and Q2. The ON period of the switching element Q1 is T1, and the ON period of the switching element Q2 is T.
Assuming that 2, the ratio of the ON period of the switching element Q1 to one cycle of the switching, that is, the duty is given by the following equation. Duty = T1 / (T1 + T2) (5) When the lamp is normal, the voltage V4 of the capacitor C3 is the second conventional example.
As described above, the voltage varies with the voltage V2 and the duty, and is given by the following equation. V4 = V2 × Duty (2) Therefore, when changing the output voltage V2 of the smoothing unit 3 or the duty ratio of the switching element by dimming or the like, the voltage V2
The variable impedances VR2 and VR3 of the detection unit 7 are changed so as to cancel the change in the detection voltage V5 between and Duty, and the detection voltage V5 is made equal to the reference voltage V6.
Therefore, if the lamp is normal, V5 is given by the following equation. V5 = V6 (constant) (6) Note that V6５V5 may be used depending on the sensitivity of the abnormality detection circuit.

FIG. 3 shows operation waveforms of various parts when the lamp is normal. Since V6 = V5, the detection voltage V5 falls within the range of the thresholds V61 and V62 set above and below the reference voltage V6, and the output of the abnormality detection circuit unit is a low-level signal. At the time of one-sided emission, since the lamp has a rectifying action, the voltage V4 of the capacitor C3 rises or falls as compared with the normal state. However, the variable impedances VR2, V2
The correction of the detection voltage V5 by R3 is a correction of only the voltage V2 and the duty, and does not include a change of the voltage V4 due to one-sided emission. Therefore, the detection voltage V5 is out of the range between the thresholds V61 and V62, and the output of the abnormality detection circuit unit is at the high level.

FIG. 4 shows operation waveforms of each part when the duty is changed. Variable impedance VR2, VR3 is Du
The detection voltage V5 is kept constant because it changes so as to satisfy the expression (6) in accordance with ty. Therefore, if the lamp is normal, the abnormality detection signal becomes Low level. However, if the lamp is one-sided Emiless, the correction of the detection voltage V5 is not included in the change of the voltage V4 due to the one-sided Emiless, so that the abnormality detection signal becomes High level.

FIG. 5 shows operation waveforms of the respective parts when the voltage V2 of the smoothing capacitor C1 is changed. Since the variable impedances VR2 and VR3 change so as to satisfy Expression (6) according to the voltage V2, the detection voltage V5 is kept constant. Therefore, similarly to the case where the duty is changed, the abnormality detection signal becomes High level only when the lamp is abnormal. It should be noted that when both the duty and the output voltage V2 of the smoothing unit 3 are changed, only the lamp abnormality can be detected for the same reason. Therefore, it is not necessary to use a high-speed and high-voltage element as in Conventional Example 1. Further, unlike the conventional example 2, a malfunction in which the abnormality detection signal becomes the high level even though the lamp is normal does not occur.

(Embodiment 2) An embodiment according to claim 2 of the present invention will be described with reference to FIGS. In this embodiment, a main circuit similar to that of the first embodiment shown in FIG. 1, a detection unit 7 including switching elements Q3 and Q4, resistors R1, R2, R3, and a capacitor C4, and a reference voltage unit that generates a reference voltage V6 8, a discharge lamp abnormality detection circuit section 9, and a driver 1
A driver 2 that performs the same input / output operation as the driver 1;
Switch control unit 1 including inversion buffer P1 and control circuit
It consists of 0. The discharge lamp abnormality detection circuit unit 9 is configured by, for example, a window comparator, and the output voltage V5 of the detection unit 7 is set to a threshold value V61 and a threshold value V61 set above and below the reference voltage V6.
If it is within the range of 62, a low-level signal is output, and if it is out of the range, a high-level signal is output.

As described in the second conventional example, the voltage V4 of the capacitor C3 is equal to the voltage V2 and the duty when the lamp is normal.
To change. Here, the maximum value of the output voltage V3 of the high-frequency converter 4 is the voltage V2 of the capacitor C1. V4 = V2 × Duty (2) Then, the voltage V2 and the duty, the voltage V of the capacitor C3,
4 changes, the transistors Q3, Q3
4, the detection voltage V5 exerted by the voltage V2 and Duty
Less change.

In the switch controller 10, the signal V8 obtained by inverting the input signal V7 of the driver 1 of the switching elements Q1 and Q2 using the inversion buffer P1 is used as the input signal of the driver 2. Since the driver 1 and the driver 2 perform the same input / output operation, the switching elements Q1 and Q4 are simultaneously turned on and off. Further, the switching elements Q2 and Q3 are turned on / off at the same time. Therefore, the detection voltage V5 can be expressed by the following equation using the voltage V4 and the duty. However, Duty is replaced by T1 / (T1 + T2) in equation (5). V5 = V4 × (T2 / (T1 + T2)) × (R3 / (R2 + R3)) = V2 × T1 × T2 × R3 / {(T1 + T2) ² × (R2 + R3)}

When the duty is changed by light control or the like, if the ON period T1 of the switching element Q1 increases, the ON period T2 of the switching element Q2 decreases.
A region where the change in the detection voltage V5 due to the duty decreases around ty = 0.5 is generated. FIG. 7 shows a change in duty and a detection voltage V5 normalized on the basis of a case where Duty = 0.5. In the region where the change is reduced, when the lamp is normal, the difference between the reference voltage V6 and the detection voltage V5 is smaller than in the second conventional example. Therefore, even if the threshold width is narrow, the abnormality detection signal is high even though the lamp is normal as in Conventional Example 2.
A malfunction such as a high level does not occur.

(Embodiment 3) An embodiment corresponding to claim 3 of the present invention will be described with reference to FIGS. In this embodiment, a main circuit similar to that of the first embodiment shown in FIG.
2, a detection unit 7 comprising R3, a reference voltage unit 8 for generating a constant DC reference voltage V6, a discharge lamp abnormality detection circuit unit 9, a switch control unit 10, resistors R4, R5, R6, R7, a differential amplifier. It comprises a correction unit 11 composed of OP1 and OP2. The discharge lamp abnormality detection circuit unit 9 is configured by, for example, a window comparator, and outputs a Low level signal when the output voltage V5 of the detection unit 7 is within a range between threshold values V61 and V62 set above and below the reference voltage V6. H if out of range
It outputs a high-level signal.

As described in the conventional example 2, the voltage V4 of the capacitor C3 is equal to the voltage V2 and Dut when the lamp is normal.
It changes with y. Therefore, the detection voltage V5 output from the detection unit 7 is obtained by dividing the voltage V4 of the capacitor C3 by the resistances R2 and R3.
, The equation (3) is obtained. V5 = V2 × Duty × (R3 / (R2 + R3)) (3)

Therefore, in the present embodiment, the correction unit 11 is provided which suppresses a change in the detection voltage V5 due to a change in the voltage V2. First, the reference voltage V6 is set so that the discharge lamp is normal and equal to the detection voltage at the time of rated lighting.
The correction unit 11 includes a resistor R that satisfies R4 / R5 = R2 / R3.
4, R5 and the time during which the switching element Q1 is turned on is T.
1. When the ON time of the switching element Q2 is T2, the resistors R6 and R7 satisfy T1 / T2 = R7 / R6.
And differential amplifiers OP1 and OP2 having a gain of 1. Note that the resistors R6 and R7 are sufficiently larger than the resistor R5. Thus, when the lamp is normal, V8 = V5.

Since V5 = V6 at the time of rated lighting, there is no need for correction. At this time, V8 =
Since V5, V8 = V6. Therefore, the differential amplifier O
The output V9 of P1 is 0, and the output V10 of the differential amplifier OP2 is
= V5, and the correction does not work.

Next, a smoothing capacitor C1 is used for dimming.
When the voltage V2 is decreased, the correction unit 11 operates. Due to the decrease in the voltage V2, the detection voltage V5 decreases from Expression (3), and since V8 = V5, V8 also decreases. At this time, the output V9 of the differential amplifier OP1 becomes (V8−V6). The output V10 of the differential amplifier OP2 becomes V5− (V8−V6). If the discharge lamp is normal, V8 = V5, so that the output V10 of the correction unit 11 = V6, and no malfunction of the abnormality detection unit 7 occurs. On the other hand, when the discharge lamp is one-sided Emiless, the value of V8 is not affected by Emiless, so that V8 ≠ V5
Becomes Therefore, V10 ≠ V6, and abnormality of the discharge lamp can be detected.

FIG. 10 shows the operation waveforms of the respective parts when the lamp is operating normally and at the rated lighting. The corrected detection voltage V10 is V6 = V
10, the threshold values V61 and V6 set above and below V6.
2, and the abnormality detection signal becomes a low level.
At the time of one-sided emission, since the lamp has a rectifying action, the voltage V4 of the capacitor C3 rises or falls as compared with the normal state. Therefore, the corrected detection voltage V10 is equal to the reference voltage V
The value falls outside the range of the threshold values V61 and V62 set above and below 6, and the abnormality detection signal becomes a high level.

FIG. 11 shows operation waveforms of the respective parts when the voltage V2 of the smoothing capacitor C1 is changed. Since the correction value V9 of the correction circuit 11 changes in accordance with the change of the voltage V2, if the discharge lamp is normal, the detected voltage after correction is V10 = V
It becomes 6. Further, at the time of one-sided emission, the correction operation does not include the correction for the change of the voltage V4 due to the one-sided emission, so that the abnormality of the discharge lamp can be detected. Therefore, although the lamp is normal as in Conventional Example 2, the abnormality detection signal is Hi.
No malfunction such as the gh level occurs.

(Embodiment 4) An embodiment according to claim 4 of the present invention will be described with reference to FIGS. This embodiment has a configuration in which a differentiating circuit of the detection voltage V5 and a window comparator are added to the circuits of FIGS. 5 and 6 of the second embodiment. FIG. 13 shows operation waveforms of the respective units when the lamp state changes from normal to Emiless on one side. When the lamp is normal, the voltage V4 of the DC separator 6 has a value determined by the voltage V2 of the smoothing capacitor C1 and the duty. However, since the lamp has a rectifying effect when the lamp becomes Emiless on one side, the lamp current ila
Flows only in one direction. Therefore, the charging current to the capacitor C3 becomes larger than the discharging current, so that the capacitor C3
Voltage V4 rises. Since the capacitor C3 is a coupling capacitor having a relatively large capacity, the change in the voltage V4 is slower than the inverter cycle. Therefore,
There is a time delay in comparing the detection voltage V5 with the reference voltages V61 and V62 and outputting a signal V7 indicating a lamp abnormality.

Therefore, in the present embodiment, focusing on the fact that the change in the voltage V4 of the capacitor C3 is largest at the moment when one side becomes Emiless, the differential value of the detection voltage V5 is also used for lamp abnormality detection. The differential value V8 of the detection voltage V5 is compared by a window comparator, and when it exceeds a certain value, an abnormality detection signal V9 is output. The input to the control circuit goes high when the signal V7 or V9 goes high. Therefore, lamp abnormality can be detected quickly.

(Embodiment 5) An embodiment according to claim 5 of the present invention will be described with reference to FIGS. In this embodiment, a main circuit similar to that of the first embodiment shown in FIG.
2, a detection unit 7 including R3, a reference voltage unit 8 for generating a constant reference voltage V6, a discharge lamp abnormality detection circuit unit 9, a switch control unit 10, and a detection unit for detecting the sum of the lamp voltage vla and the voltage V4. And a window comparator to which the output V8 of the voltage dividing circuit is input.

As described in the fourth embodiment, the change in the voltage V4 after the occurrence of the lamp abnormality is gentle compared to one cycle of the inverter. Therefore, a short-time lamp abnormality such as a loose contact cannot be detected from the voltage V4. Therefore, in this embodiment, the sum of the lamp voltage vla and the voltage V4 is divided by the resistors R8 and R7 to detect V8. Since the voltage V4 can be regarded as constant in a short time range, (vla + V
The instantaneous state of the lamp can be estimated from the detected value V8 of 4). Therefore, when the detected value V8 becomes equal to or more than a certain value or less than a certain value, the output of the abnormality detecting circuit unit 9 is set to High level by the output V9 of the window comparator to detect instantaneous lamp abnormality. In addition, for one-sided Emiless having a long duration, a lamp abnormality is detected by the method described in claims 1 to 4 (for details, see Examples 1 to 4).

As described above, in this embodiment, a sudden lamp abnormality and a continuous lamp abnormality are detected by different methods, so that a reference value of the comparison voltage suitable for each abnormality can be set. The method of detecting the lamp voltage vla may be another method. Further, as shown in FIGS. 15 and 16, an ila detecting section including a current transformer CT, resistors R8 and R7, a capacitor C5 and a diode D1 is provided to provide a lamp current i.
Even if la is detected, a sudden lamp abnormality can be detected, and the same effect can be obtained.

(Embodiment 6) An embodiment according to claim 6 of the present invention will be described with reference to FIGS. In the present embodiment, an input AC power supply unit 1 including an AC voltage v1 such as a commercial power supply, a rectifying unit 2 including a diode bridge,
A smoothing section 3 composed of an electrolytic capacitor C1, a high-frequency conversion section 4 composed of switching elements Q1 and Q2, a load section 5 composed of an inductor L11, a capacitor C21, a discharge lamp LAMP1, an inductor L12, a capacitor C22, and a discharge lamp LAMP2; DC separation unit 6 composed of C31 and C32, and resistors R11, R21, R31, R12,
R22, R32, capacitors C41, C42, a detection unit 7 including switching elements Q31, Q41, Q32, Q42, a reference voltage unit 8 for generating a constant reference voltage V6, a discharge lamp abnormality detection circuit unit 9, a switch control unit 10 Consists of

In this embodiment, the detection voltages V51 and V52 are determined by the voltage V2 of the smoothing capacitor C1 and the duty ratio even if the characteristics of the lamp voltages vla1 and vla2 during lamp dimming are different as shown in FIG. Therefore, irrespective of the lamp characteristics, when the detection voltages V51 and V52 are compared with the reference voltage, the one-sided emission can be detected by the same abnormality detection circuit as in the case of one lamp. Further, even if the filaments in the same direction of both lamps become single-sided emissive, lamp malfunction can be detected without causing a malfunction as in Conventional Example 3.

[0041]

According to the first to third aspects of the present invention, when the discharge lamp is normal, there is provided a means for correcting the fluctuation of the output voltage of the detection section with respect to the fluctuation of the voltage of the DC separation section. This has the effect of preventing malfunction. Further, according to the invention of claim 4 or 5, there is an effect of quickly detecting a lamp abnormality. Furthermore, according to the invention of claim 6, there is an effect that one-sided Emiless detection can be performed without malfunction when a plurality of lamps having different characteristics are turned on in parallel.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a configuration of a main circuit according to a first embodiment of the present invention.

FIG. 2 is an operation waveform diagram when the lamp is normal according to the first embodiment of the present invention.

FIG. 3 is an operation waveform diagram when the duty is changed according to the first embodiment of the present invention.

FIG. 4 is an operation waveform diagram when the smoothed output voltage of the first embodiment of the present invention is changed.

FIG. 5 is a circuit diagram showing a configuration of a main circuit according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram illustrating a configuration of a control circuit according to a second embodiment of the present invention.

FIG. 7 is an operation explanatory diagram of Embodiment 2 of the present invention.

FIG. 8 is a circuit diagram illustrating a configuration of a main circuit according to a third embodiment of the present invention.

FIG. 9 is a circuit diagram illustrating a configuration of a control circuit according to a third embodiment of the present invention.

FIG. 10 is an operation waveform diagram when the lamp is normal according to the third embodiment of the present invention.

FIG. 11 is an operation waveform diagram when the smoothed output voltage is changed according to the third embodiment of the present invention.

FIG. 12 is a circuit diagram illustrating a configuration of a control circuit according to a fourth embodiment of the present invention.

FIG. 13 is an operation explanatory diagram of the fourth embodiment of the present invention.

FIG. 14 is a circuit diagram illustrating a configuration of a control circuit according to a fifth embodiment of the present invention.

FIG. 15 is a circuit diagram showing a configuration of a main circuit according to a modification of the fifth embodiment of the present invention.

FIG. 16 is a circuit diagram showing a configuration of a control circuit according to a modification of the fifth embodiment of the present invention.

FIG. 17 is a circuit diagram illustrating a configuration of a main circuit according to a sixth embodiment of the present invention.

FIG. 18 is a circuit diagram illustrating a configuration of a control circuit according to a sixth embodiment of the present invention.

FIG. 19 is an operation explanatory diagram of the sixth embodiment of the present invention.

FIG. 20 is a circuit diagram showing a configuration of a main circuit of Conventional Example 1.

FIG. 21 is a circuit diagram showing a configuration of a control circuit of Conventional Example 1.

FIG. 22 is a circuit diagram showing a configuration of a main circuit of Conventional Example 2.

FIG. 23 is a circuit diagram showing a configuration of a control circuit of Conventional Example 2.

FIG. 24 is a waveform chart showing switching timings in Conventional Example 2.

FIG. 25 is a waveform chart showing the operation of each part during half-wave discharge in Conventional Example 2.

FIG. 26 is a waveform chart showing the operation of each unit when the duty ratio of Conventional Example 2 is increased.

FIG. 27 is a circuit diagram showing a configuration of a main circuit of Conventional Example 3.

FIG. 28 is a circuit diagram showing a configuration of a control circuit of Conventional Example 3.

FIG. 29 is a waveform chart showing the operation of each section when a lamp on one side is abnormal in Conventional Example 3.

FIG. 30 is a waveform chart showing the operation of each unit when both lamps are abnormal in Conventional Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input AC power supply part 2 Rectification part 3 Smoothing part 4 High frequency conversion part 5 Load part 6 DC separation part 7 Detection part 8 Reference voltage part 9 Discharge lamp abnormality detection circuit part 10 Switch control part

Claims (6)

[Claims] 1. An input AC power supply, a rectifier for rectifying the input AC power, a high frequency converter for converting an output voltage of the rectifier into a high frequency voltage, and a DC separator for separating a DC component from an output of the high frequency converter. Unit, a load unit including a discharge lamp to which a high frequency power separated from a direct current component is applied, a control unit of a high frequency conversion unit, a detection unit for detecting a voltage of the direct current separation unit, and a reference voltage generation for generating a reference voltage Unit, in a discharge lamp lighting device having means for detecting abnormality of the discharge lamp from the output voltage of the detection unit and the reference voltage, when the discharge lamp is normal, the output voltage of the detection unit with respect to the voltage fluctuation of the DC separation unit A discharge lamp lighting device comprising means for correcting fluctuation. 2. The high-frequency conversion unit includes a switching element that is turned on and off at a high frequency, and the correction unit includes a unit that suppresses a change in an output voltage of a detection unit with respect to an increase and a decrease in the on-duty of the switching element. The discharge lamp lighting device according to claim 1. 3. The apparatus according to claim 1, wherein the correction unit includes a unit that suppresses a change in an output voltage of the detection unit with respect to an increase or a decrease in the maximum value of the voltage output from the high-frequency conversion unit.
The discharge lamp lighting device as described in the above. 4. The discharge lamp lighting device according to claim 1, further comprising a differentiating circuit for detecting a change in a DC voltage separated from a high-frequency output. 5. The discharge lamp lighting device according to claim 1, further comprising at least one of a lamp voltage detecting unit and a lamp current detecting unit. 6. The discharge lamp lighting device according to claim 1, wherein the load includes discharge lamps having different characteristics.