JPH02162696A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To surely detect a life end to be coped with no regard to an assortment of an inverter by detecting a lighting state by means of a discharge lamp current or voltage. CONSTITUTION:When a discharge lamp causes half-wave discharge at its life end so that a current is generated only in the solid line arrow direction, a transistor Q3 does not turn ON, and when the current flows in the broken line arrow direction, Q1 remains OFF, while capacity C0 indicates the states (a) and (b) respectively. That is, deterioration of the discharge lamp starts, the current in one direction grows large, a difference is generated in the constant of C0 at the time charge of and discharge due to a charging a circuit 6 and a discharge circuit 7 showing a voltage waveform in the middle of the states (a) and (b). When this is detected by an output control circuit 4, an action of an inverter I can be controlled in a proper state in the state where deterioration is started.

Description

[Detailed Description of the Invention] [Field of Application in JI Industry] The present invention relates to a discharge lamp and a high-frequency lighting device for lighting a discharge lamp at a high frequency.

1 Jubei's technology 1 This type of discharge lamp lighting device is shown in Fig. 8. This discharge lamp lighting device was proposed in Japanese Patent Application No. 61-5243, in which switching cables Q, Q2 connected in series to both ends of a DC power source E are alternately turned on and off by a drive circuit 1. The discharge lamp 1 is lit at high frequency. In addition, the discharge lamp
is connected to both ends of the switching element Q via a capacitor C1 and a choke coil L1, and the choke coil L constitutes a resonant circuit together with a capacitor c2 connected to both ends of the discharge lamp l. Note that capacitor C is a capacitor for DC cut.
Reference numeral 3 is also used as a power source for causing a lamp current to flow through the discharge lamp 1 when the switching cable Q is on. This discharge lamp lighting device was devised to detect the end of the lifespan of the discharge lamp and shift the operation of the switching element Q + +Q2 to a safe range. A circuit for shifting the operation of the switching elements Q, Q2 to a safe area is connected between the connection point of the capacitor C1 and the discharge lamp l and the negative electrode of the DC power supply E, and includes the switching element Q2, the choke coil L, and the negative electrode of the DC power supply E. A voltage detection@2 that detects the voltage across the series circuit of the discharge lamp l (capacitor C2), and a comparison section 3 that detects that the output state of the voltage detection section 2 is at the end of its life by comparing it with a reference value. and the switching element Q according to the output of this comparator 3.
, , an output control g4 that controls the drive circuit 1 to perform the switching operation of Q2.

In the discharge lamp lighting device, when the discharge lamp l is lit normally, an alternating current flows through the discharge lamp l, so that
The voltage of capacitor C5 is approximately half of the power supply voltage E (E/2
), so a voltage of (E/2) is applied to both ends of the voltage detection section 2.

Here, when the discharge lamp l reaches the end of its life, the discharge lamp l causes a half-wave discharge phenomenon. The discharge lamp p at this time can be equivalently represented by a resistor RNa and a diode Dea, as shown in FIGS. 9(a) and 9(b). Here, the discharge lamp l is the ninth
In the half-wave discharge state shown in Figure (a), the charging voltage of capacitor CI reaches E due to the difference in the charging and discharging time constant of capacitor C1 when switching element Q is turned on and when switching element Q2 is turned on. Therefore, the voltage applied to the voltage detection section 2 becomes almost zero. Also, Figure 9 (
When the half-wave discharge state shown in h) is reached, the capacitor C is charged to E in the opposite direction to the above case. For this reason,
At this time, the voltage applied to the voltage detection section 2 is 2E.

Note that the above is true when C, >> C2. Therefore, by detecting this difference in voltage with the comparator 3, the lighting state of the discharge lamp l can be detected, and the output controller 4 controls the operation of the drive circuit 1 according to the output of the comparator 3. By doing so, it is possible to perform appropriate switching control of the switching elements Q, , Q, depending on the lighting state of the discharge lamp I.

In addition, a discharge lamp! Another discharge lamp 7α lamp arrangement that detects the end of its lifespan and moves the operation of switching elements Q, Q2 to a safe area is the There is a device that detects the end of life of a discharge lamp by using a thermistor or the like to detect the temperature of a component that generates heat due to half-wave discharge (for example, a switching element, an inductance, etc.).

[Problem to be Solved by the Invention 1] However, the circuit shown in FIG. 8 requires the condition that C, >> C2, and if this condition is not met, it is difficult to realize appropriate operation. There is. Furthermore, even if the push-pull inverter has the same circuit configuration as shown in FIG. 8 above, the capacitor C as shown in FIG.
The above-mentioned circuit cannot be applied if the connection points of 1 are different, and furthermore, it cannot be applied to a seven-bar bridge inverter shown in FIG. 11 or a one-stone inverter shown in FIG. 12. In other words, the scope of application of this circuit of FIG. 8 is extremely narrow. Note that in the 1E, capacitor 01□C12 functions similarly to capacitor CI.

In addition, with the method of detecting the end of a discharge lamp's life from the temperature of its heat-generating parts, it takes time to detect that it is at the end of its life. If the device is installed at a low temperature, there is a problem in that it becomes difficult to detect the temperature.

The present invention has been made in view of the above points, and its purpose is to provide a discharge lamp lighting system that can reliably detect the end of life and take appropriate measures, and that can be applied regardless of the type of inverter. The goal is to provide equipment.

1 Means for Solving the Problems 1 In order to achieve the above object, the present invention provides a charging circuit for charging a capacitor, a discharging circuit for discharging the charge of the capacitor, and a lamp current flowing through a discharge lamp or a discharge lamp. A detection circuit detects the lighting state of the discharge lamp from the lamp voltage generated at both ends, and controls the operation of the charging circuit and the discharge circuit according to the lighting state of the discharge lamp, and a detection circuit detects the lighting state of the discharge lamp from the voltage waveform at both ends of the capacitor. The inverter is provided with an output control circuit that determines the state and controls the operation of the inverter to an appropriate operating state according to the lighting state of the discharge lamp.

[Operation J] As described above, the detection circuit detects the lighting state of the discharge lamp from the lamp current flowing through the discharge lamp or the lamp voltage generated at both ends of the discharge lamp, so that the discharge lamp can be operated regardless of the configuration of the inverter. The detection circuit controls the operation of the charging circuit and the discharging circuit according to the lighting state of the discharge lamp, and the output control section detects the discharge lamp's lighting state from the voltage waveform across the capacitor. By determining the ζ lamp status, the output control unit directly detects the end of the discharge lamp's life from the output of the detection circuit, making it easier to detect the discharge lamp's lamp-like state. be.

[Embodiment 11] As shown in FIG. 1, this embodiment includes a charging circuit 6 for charging the capacitor co, a discharging circuit 7 for discharging the charge of the capacitor C0, and a lamp current flowing through the discharge lamp l. A detection circuit 5 detects the lighting state of the discharge lamp l from the lamp voltage generated at both ends of the electric lamp l, and controls the operation of the charging circuit 6 and the discharging circuit 7 according to the lighting state of the discharge lamp l, and the capacitor C8. From the voltage waveform at both ends of the discharge lamp l
The output control circuit 4 determines the lighting state of the discharge lamp I and controls the operation of the inverter I to an appropriate operating state according to the lighting state of the discharge lamp I. Note that the lighting device A in the figure is composed of the inverter I and a rectifier circuit that rectifies the commercial power supply AC.

FIG. 2 shows a specific circuit of the circuit shown in FIG. The charging circuit 6 is composed of transistors Q, , Q and resistors R, -R, and the discharging circuit 7 is composed of diodes D,, D2 that output detection signals to the circuit 6 and the discharging circuit 7, respectively. is composed of a transistor Q and a resistor R4.

When the discharge lamp l is lit normally, an alternating current flows through the current transformer CT, so depending on the direction of the lamp current, the transistors Q, Q, are turned on and off alternately via the diode DI-D2. repeat. here,
When transistor Q is on, transistor Q2 is also on, so resistor R.

Capacitor C0 is charged by control power supply Vec via. Further, when the transistor Q is turned on, the charge stored in the capacitor C0 is discharged. In other words,
When the discharge lamp 1 is normally lit, the capacitor C0 is repeatedly charged and discharged as shown on the left side of FIG.

On the other hand, when the discharge lamp 1 reaches the end of its life and undergoes half-wave discharge, a large amount of lamp current will flow in either direction of the arrows shown by the solid line or the broken line in FIG. 2 only in either direction of the dashed arrow
A current will flow. Now, if current flows only in the direction shown by the solid arrow in Figure 2, diode D2
Since the detection signal is no longer output from the transistor Q, the transistor Q is no longer turned on. Therefore, the capacitor c0 is maintained in a charged state as shown by A on the right side of FIG. Conversely, if current flows only in the direction of the dashed arrow in Figure 2, no detection signal is output from diode D, transistor Q remains off, and capacitor C0 is turned off as shown in Figure 3. It is kept in a discharge state as shown by the mouth on the right. Therefore, if the output control circuit 4 detects whether the Contin'fCo(pWJ\II voltage continues to be at zero level or remains charged), it can be detected that the discharge lamp l is at the end of its life. It becomes possible to shift the operation of the inverter I to a control state suitable for the state of the discharge lamp I.The above explanation is based on the case where the discharge lamp I is completely half-wave discharged. In a state where the deterioration of l has started, the following occurs.In other words, in this state, the current flowing in either direction to the discharge lamp l becomes large, and therefore the capacitor C8 by the charging circuit 6 and the discharging circuit 7
This causes a difference in the charging and discharging time constants. Therefore, capacitor C
The voltage waveform at both ends of 0 is in an intermediate state between the left and right waveforms in Figure 3, and if this is detected by the output control circuit 4, the operation of the inverter (■) can be controlled to an appropriate state in the state where deterioration has begun. .

[Embodiment 2] Fig. 4 shows another embodiment, in which the detection circuit 5 is composed of a humpator CP2, diodes D, . series circuit with diode D2 and resistor RI2
The lamp current is detected every half wave in a series circuit with the Note that the charging circuit 6 and the discharging circuit 7 have the same configuration as the circuit in FIG. 2. Now, when a current flows through the discharge lamp l in the direction of the solid arrow in Figure 4, a positive voltage is generated across the resistor R, □, and this voltage is referred to as the reference voltage determined by the resistors R, 3, R, . Compare with comparator CP. Further, when a current flows in the direction of the dashed arrow in FIG. 4, a negative voltage is generated across the resistor R11, and this voltage is compared with a reference voltage determined by the resistor RISSR+6 by the comparator CP2. In other words, in the case of this embodiment, if the reference voltages of the comparators cp, cP2 are set to values that indicate that the discharge lamp l has deteriorated, the output control circuit 4 can detect that the discharge lamp l is at the end of its life. This can be easily determined. Note that this detection circuit 5
The operation control of the charging circuit 6 and the discharging circuit 7 by the output of is substantially the same as that of the circuit shown in FIG. 2, so the explanation thereof will be omitted.

[Embodiment 31] FIG. 5 shows still another embodiment, which differs from each of the above-mentioned embodiments in that the detection circuit 5 detects the waveform of the voltage across the discharge lamp l to detect the end of its life. Different from the example. In this embodiment, the present invention is applied to a discharge lamp lighting device including a push-pull inverter. The detection circuit 5 is connected to a humpparator cp, -cp, . . . a latch circuit 8.
, 9, transistor Q, , Q, , diode D21-D
26 and resistors R2, -R3g, and the charging circuit 6 and discharging circuit 7 are the same as those in the above embodiment.

In the detection circuit 5 of this embodiment, a series circuit of a diode D21 and resistors R2, , R22 and a series circuit of a diode D2□ and resistors R, , R, 4 are used to control the discharge lamp L every half wave. The voltage is detected, and the voltages generated across the resistor R2□ and the resistor R24 every half wave are detected by the comparators CP, ..., CP, and the comparators cp, ..., cp, respectively.
, are compared. Here, the reference voltages of the comparator CP1□ and the comparators cp and 3 are set so that the output becomes high level when a voltage (in absolute value) higher than the normal lamp voltage is generated across the discharge lamp l. ,
The comparators Cp, . . . cp, are designed so that the output becomes high level when the discharge lamp r reaches the end of its life.

Discharge lamp now! When the lamp is lit normally, the lamp voltage has a symmetrical waveform in positive and negative directions as shown in FIG. 6(a). In this case, the voltages shown in FIGS. 6(b) and 6(d) are generated across the resistors R2□ and R2 every half wave. Here, the reference voltages Vr+ to Vr4 of the comparators cp, , -cp, are the sixth
Since the settings are as shown in Figures (b) and (d), the outputs of the comparators CP + 2- CP I3 are
As shown in Figures (e) and (e), the transistor Q,
, Q are turned on alternately as shown in (f) and (g) of the figure. Therefore, the voltage across the capacitor C0 is shown in Figure 6 (h).
The waveform is shown in . Note that during this normal lighting, the outputs of the comparators cp, . . . , cp, . remain at a low level.

Next, a case will be described in which the discharge lamp 1 exhibits a half-wave discharge phenomenon at the end of its life.

The lamp voltage at this time has a positive and negative asymmetric waveform as shown in FIG. 7(a). When the lamp voltage becomes asymmetrical in this way, the voltage across the resistor R22 increases as shown in FIG. 7), and this voltage rises above the reference voltage Vr of the comparator CP.

Therefore, there is a period in which the comparators CP, , CP, 2 are both at high level. The respective output states are shown in Figure 7 (
Shown in e) and (d). When the output of the comparator CP becomes high level in this way, this output is held in the latch circuit 9 as shown in FIG. 7(g), and by turning on the transistor Q4 with the output of the latch circuit 9, (f
) The charging circuit 6 stops operating regardless of the output of the comparator CP3 shown in ).

Therefore, the voltage across capacitor C0 is maintained at zero level. On the other hand, when the lamp voltage becomes negative or large, contrary to FIG. 7(,), the discharge circuit 7 stops operating, and the voltage across the capacitor C6 is maintained approximately at the voltage of the control power supply Vcc. Therefore, in the case of this embodiment as well, it is possible to detect that the discharge lamp l is at the end of its life as in the above-mentioned embodiment, and it is possible to shift the operation of the inverter to a control state suitable for the state of the discharge lamp l. Become.

[Effect of the Invention 1] As described above, the present invention includes a charging circuit that charges a capacitor, a discharging circuit that discharges the charge of the capacitor,
a detection circuit that detects the lighting state of the discharge lamp from the lamp current flowing through the discharge lamp or the lamp voltage generated at both ends of the discharge lamp, and controls the operation of the charging circuit and the discharging circuit according to the lighting state of the discharge lamp; It is equipped with an output control circuit that determines the lighting state of the discharge lamp from the voltage waveform across the capacitor and controls the operation of the inverter to an appropriate operating state according to the lighting state of the discharge lamp. Since the lighting state of the discharge lamp is detected from the lamp current flowing through the lamp or the lamp voltage generated at both ends of the discharge lamp, there is an advantage that the lighting state of the discharge lamp can be detected regardless of the configuration of the inverter.

In addition, the detection circuit controls the operation of the charging circuit and the discharging circuit according to the 7σ lamp state of the discharge lamp, and the output control section determines the lighting state of the discharge lamp from the voltage waveform across the capacitor. It is possible to use a signal that makes it easier to detect the lighting state of the discharge lamp than when the output control unit directly detects the end of the life of the discharge lamp from the output of the output control circuit. This has the effect of making it possible to accurately control the operation of the inverter. Furthermore, if the detection circuit detects the lamp current or lamp voltage every half wave and drives the charging circuit and discharging circuit individually every half wave, it is possible to determine which filament has the lifespan based on the voltage waveform across the capacitor. It also has the advantage of being able to detect what is happening.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the basic configuration of the present invention, Fig. 2 is a specific circuit diagram showing one embodiment, Fig. 3 is an explanatory diagram of the same operation as above, and Fig. 4 is a specific circuit diagram showing another embodiment. , FIG. 5 is a specific circuit diagram showing still another embodiment, FIG. 6 is an operating waveform diagram of the above discharge lamp during normal lighting, FIG. 7 is an operating waveform diagram of the above discharge lamp at the end of its life, and FIG. Figure 8 is a circuit diagram of a conventional example.
FIGS. 9(a) and 9(b) are equivalent circuit diagrams of a discharge lamp at the end of its life, and FIGS. 10 to 12 are circuit diagrams showing a discharge lamp lighting device having a different configuration from the above. 2 is an inverter, l is a discharge lamp, 4 is an output control circuit, 5 is a detection circuit, 6 is a charging circuit, 7 is a discharge circuit, and C0 is a capacitor. Agent Patent Attorney Ishi 1) Chief 7C 薯寥8 figure Neck 11 figure: J12 figure

Claims (2)

[Claims] (1) In a discharge lamp lighting device that lights a discharge lamp at high frequency using an inverter, there is a charging circuit that charges a capacitor, a discharge circuit that discharges the charge of the capacitor, and a lamp current that flows through the discharge lamp or both ends of the discharge lamp. a detection circuit that detects the lighting state of the discharge lamp from the lamp voltage generated in the lamp voltage and controls the operation of the charging circuit and the discharging circuit according to the lighting state of the discharge lamp; and a detection circuit that detects the lighting state of the discharge lamp from the voltage waveform across the capacitor. A discharge lamp lighting device comprising: an output control circuit that determines the lighting state of the discharge lamp and controls the operation of an inverter to an appropriate operating state according to the lighting state of the discharge lamp. (2) The discharge lamp lighting device according to claim 1, wherein the detection circuit detects the lamp current or the lamp voltage every half wave, and drives the charging circuit and the discharging circuit individually every half wave.