JP2004303520A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device preventing the generation of defects in a device or a lamp such as abnormal rising of voltage of the lamp in rectifying lighting or non-rectifying lighting, or abnormality of the lamp such as impossible lighting. <P>SOLUTION: The discharge lamp lighting device is equipped with an inverter circuit IV converting DC voltage of a DC power source into high frequency voltage; a discharge lamp load circuit LAC having a ballast choke T1 and coupling capacitor C4 connected to the ballast choke T1 through the lamp LA; a rectifying lighting protection means NP1A detecting asymmetry of lamp current in rectifying lighting with the coupling capacitor C4 and controlling oscillation of the inverter circuit IV based on the detected asymmetry current; and a lamp voltage abnormal rising protection means NP1B detecting lamp voltage in the non-rectifying lighting with the voltage of the lamp LA and controlling the oscillation of the inverter circuit IV based on the detected voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a discharge lamp lighting device for lighting a discharge lamp with a high-frequency current generated by a switching element.
[0002]
[Prior art]
In the conventional discharge lamp lighting device, a DC power supply E, switching elements Q1 and Q2 for switching a DC current supplied from the DC power supply E to generate a high-frequency current, a discharge lamp LA and a coupling capacitor C4 are connected in series. A discharge lamp lighting device including a discharge lamp load circuit LAC for lighting the discharge lamp LA with a high-frequency current generated by the switching elements Q1 and Q2, and a switching element control circuit IC1 for controlling the switching elements Q1 and Q2, A protection circuit NP2 is provided for detecting an abnormality in the discharge lamp LA by detecting a voltage generated in the coupling capacitor C4 and outputting a control signal to the switching element control circuit IC1 (for example, Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-15289 A (paragraphs 0035 to 0047, FIGS. 1 to 8)
[0004]
[Problems to be solved by the invention]
In the conventional discharge lamp lighting device, the discharge lamp LA is started and lights up in a non-rectified manner due to a defect such as the inability of the electrodes F1 and F2 to emit thermoelectrons. In this case, the discharge lamp current is symmetric and the discharge lamp impedance is not much different from the normal state, so that the lamp abnormality protection circuit NP2 does not operate. There was a problem that occurred.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a first object of the present invention is to provide a simple circuit for rectifying lighting which may be caused by the end of lamp life or lamp failure. An object of the present invention is to provide a discharge lamp lighting device capable of preventing occurrence of a failure of a device or a lamp by avoiding the continuation of the abnormal state with respect to a lamp abnormality such as an abnormal voltage rise of a non-rectified lighting lamp and a failure to start.
[0006]
A second object of the present invention is to provide a discharge lamp lighting device capable of preventing a lamp abnormality protection circuit from being operated unnecessarily due to temporary rectification lighting and high voltage generation at the time of starting a lamp, thereby preventing the lamp from lighting normally. That is.
[0007]
Further, a third object of the present invention is to provide a lamp having a function of preheating a lamp electrode at the time of starting a lamp, in which a high voltage required for starting the lamp can be obtained and an abnormal high voltage generated when the lamp does not start is generated. It is another object of the present invention to provide a discharge lamp lighting device capable of reliably lighting a normal lamp by controlling the rectification lighting protection function not to operate until the lamp is started.
[0008]
It is a fourth object of the present invention to provide an inexpensive discharge lamp lighting device which does not require an extra detection circuit by diverting a lamp start using a rectifying lighting protection function and making a judgment based on this output change.
[0009]
[Means for Solving the Problems]
A discharge lamp lighting device according to the present invention includes a DC power supply, an inverter circuit for converting a DC voltage of the DC power supply to a high-frequency voltage, a ballast choke, and a discharge lamp (hereinafter, referred to as a lamp) connected to the ballast choke. A discharge lamp load circuit having a coupling capacitor connected thereto for lighting the lamp with a high-frequency current from the inverter circuit, and detecting the asymmetry of the lamp current during lamp rectification lighting based on the voltage level of the coupling capacitor. A rectifying lighting protection means for controlling the oscillation of the inverter circuit based on the detected asymmetric current, and a lamp voltage at the time of non-rectifying lighting of the lamp is detected based on a voltage level of the lamp, and based on the detected voltage. A lamp abnormality protection circuit having a lamp voltage abnormality rise protection means for controlling the oscillation of the inverter circuit. Those were.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention, and FIG. 2 is a waveform diagram of a lamp voltage.
In FIG. 1, a discharge lamp lighting device is connected to a DC power supply E, and switches an DC current of the DC power supply E to convert the DC current into a high frequency voltage. The high frequency voltage generated by the inverter circuit IV turns on the lamp LA. And a lamp abnormality protection circuit NP1 for detecting a failure of the discharge lamp load circuit LAC and outputting a control signal for stopping the operation of the inverter circuit IV.
[0011]
Hereinafter, details of each circuit will be described. The inverter circuit IV has a starting resistor R1 and a control power supply capacitor C1 connected in series, a constant voltage diode DZ1 connected in parallel to the control power supply capacitor C1, and a series connection between both poles of the DC power supply E. A pair of MOS-FETs Q1, Q2 (hereinafter, switching elements Q1, Q2), an inverter control circuit IC1 for controlling the switching elements Q1, Q2 (hereinafter, IV control circuit IC1), and an IV control circuit IC1 A frequency control circuit FC1 for setting the switching frequency of the switching elements Q1 and Q2 is provided. Each terminal of the IV control circuit IC1 has a power supply terminal 1 (hereinafter, referred to as a terminal 1) connected to a control power supply capacitor C1, an output terminal 2, 3, 4 (hereinafter referred to as terminals 2, 3, 4) are connected to the switching elements Q1, Q2, , 7 (hereinafter referred to as terminals 6 and 7) are connected to the frequency control circuit FC1.
[0012]
The frequency control circuit FC1 is composed of a main oscillation resistor R2 and an oscillation capacitor C2 connected in parallel between the terminals 6 and 7 of the IV control circuit IC1 and the negative electrode of the DC power supply E. The IV control circuit IC1 oscillates at a frequency f = K * (current flowing out of the terminal 6 of the IV control circuit which is a constant DC potential) with respect to a constant K determined by the capacitance of the switching elements Q1 and Q2. Perform switching operation at the frequency f. The oscillation stop terminal 5 (hereinafter referred to as terminal 5) has a function of stopping oscillation of the IV control circuit IC1 when a voltage higher than a specified voltage is applied.
[0013]
Next, the discharge lamp load circuit LAC will be described. The discharge lamp load circuit LAC has a ballast choke T1 at both ends of a switching element Q2, a coupling capacitor C4 connected in series via a lamp LA having electrodes F1, F2, and a starting capacitor C3 connected in parallel to the lamp LA. .
[0014]
Next, the lamp abnormality protection circuit NP1 will be described.
The lamp abnormality protection circuit NP1 includes rectification lighting protection means NP1A for controlling the oscillation of the inverter circuit IV when the lamp LA is rectified and lighting, and lamp voltage abnormal rise protection means NP1B for controlling the oscillation of the inverter circuit when the lamp LA is not rectified. Be composed.
[0015]
First, the rectification lighting protection means NP1A includes a voltage detection section VIN, a comparison section COMP, and a control signal output section VOUTa.
The voltage detection unit VIN includes detection resistors R10 and R11 for dividing and level-shifting the voltage across the coupling capacitor C4, a constant voltage diode DZ2, and a capacitor C10 for removing a high-frequency ripple component of the divided voltage. The DC-converted detection voltage is output to the comparator COMP. The comparator unit COMP includes two comparators IC2 and IC3, and a resistor R12 for determining a high threshold value among two reference voltages obtained by dividing the DC voltage of the control power supply capacitor C1 by resistors R12, R13, and R14. The voltage at the connection point of the resistor R13 is input to the non-inverting input terminal of the comparator IC2, and the voltage at the connection point of the resistors R13 and R14, which determines the low threshold value, is input to the inverting input terminal of the comparator IC3. By configuring so that the detection voltage from VIN is input to the inverting input terminal of the comparator IC2 and the non-inverting input terminal of the comparator IC3, a window-type comparator is formed.
[0016]
In the control signal output unit VOUTa, the output terminals of the comparators IC2 and IC3 of the comparator unit COMP are open collectors, and a pull-up resistor 15 is connected to these output terminals. Both output terminals are connected to the base of the transistor Q3. Connected. A voltage dividing resistor R16 is connected between the collector terminal of the transistor Q3 and the positive electrode of the control power supply capacitor C1, and the collector terminal is connected to the terminal 5 of the IV control circuit IC1 via a diode D4.
A parallel circuit of a capacitor C11 and a resistor R17 for dividing the voltage and removing external high-frequency noise is connected between the terminal 5 of the IV control circuit IC1 and the negative electrode of the DC power supply E.
[0017]
Next, in the lamp non-rectified voltage abnormal rise protection circuit NP1B, one end of the capacitor C6 of the capacitors C5 and C6 connected in series is connected to the negative electrode of the DC power supply E, and the other end of the capacitor C5 is connected to the electrode F1 of the lamp LA. Have been.
The connection point between the diodes D1 and D2 where the anode and the cathode are connected is connected to the connection point between the capacitors C5 and C6, and the cathode of the diode D2 is connected to the negative electrode of the DC power supply E via the capacitor C7. The anode of the diode D1 is connected to the negative electrode of the DC power supply E. Further, a series circuit of a Zener diode DZ3, a resistor R3, and a diode D3 is connected between a connection point between the diode D2 and the capacitor C7 and the terminal 5 of the IV control circuit IC1.
Note that the capacitor C11 and the resistor R17 are also used as the rectification lighting protection means NP1A.
[0018]
Next, the operation of the discharge lamp lighting device according to the first embodiment of the present invention will be described. When the discharge lamp lighting device is started and the current is supplied from the DC power supply E to the inverter circuit IV, the control power supply capacitor C1 is charged by the start-up current flowing from the DC power supply E via the start-up resistor R1, and the current of the IV control circuit IC1 is reduced. When the voltage at the terminal 1 reaches the specified operating voltage, the IV control circuit IC1 oscillates at the frequency f determined by the frequency control circuit FC1, and high-frequency signals are output from the terminals 2, 4 to the switching elements Q1, Q2.
[0019]
The switching elements Q1 and Q2 are turned on and off alternately to supply a high-frequency current to the discharge lamp load circuit LAC. The high-frequency current causes a series circuit including the ballast choke T1 and the starting capacitor C3 to perform LC resonance. As a result, a high voltage is generated across the starting capacitor C3, that is, across the lamp LA, and the lamp LA is started and continues lighting at the frequency f. Since a constant voltage diode DZ1 is connected in parallel to the control power supply capacitor C1, the voltage applied to the terminal 1 of the IV control circuit IC1 is limited by the Zener voltage of the constant voltage diode DZ1.
[0020]
Next, the operation of the rectification lighting protection means NP1A of the lamp protection circuit NP1 will be described with reference to FIGS.
When the lamp LA is turned on, the terminal voltage of the switching element Q2, that is, the input voltage to the discharge lamp load circuit LAC is a high-frequency voltage having a peak value of the voltage of the DC power supply E and a frequency f. The coupling capacitor C4 generates a quasi-DC voltage in which a DC voltage is superimposed on a slight high-frequency voltage.
This quasi-DC voltage is divided and level-shifted by the voltage detection unit VIN of the rectification lighting protection means NP1A, and after being converted into a DC voltage by removing a high-frequency component by the capacitor C10, is outputted to the comparator unit COMP. . This DC voltage is compared with the two reference voltages by a window-type comparator composed of the comparator IC2 and the comparator IC3. When the DC voltage falls outside the range of the reference voltage, the transistor Q3 is turned off and the terminal of the IV control circuit IC1 is turned off. 5, an oscillation stop signal is input, the oscillation of the IV control circuit IC1 is stopped, and the switching operation of the switching elements Q1, Q2 is stopped.
[0021]
Next, the operation of the rectification lighting protection means NP1A corresponding to each load state of the lamp LA will be described. First, the voltage generated at both ends of the coupling capacitor C4 is divided by the detection resistor R10 and the detection resistor R11, the level is shifted by the constant voltage diode DZ, and the voltage when the high frequency component is removed by the capacitor C10 is, for example, When the light is normally lit, the voltage is about 7 V, and when the lamp LA is abnormal, the rectified light 1 (when the electrode F1 is at the end of life and electrons are hardly emitted) is about 9.4 V and when the lamp LA is lit, the electrode F2 is at the end of life. In a state where electrons are not easily emitted), the values of the detection resistor R10 and the detection resistor R11 are set so that a DC voltage of about 4.8 V is obtained.
Note that the voltage is 0 V when the lamp LA is not lit or has no load.
The high-frequency lamp current waveform of the lamp LA in the case of rectifying lighting 1 and rectifying lighting 2 at the time of all-light lighting is a symmetrical waveform (FIG. 2A) at the time of all-light lighting as shown in FIG. The rectifying lighting 1 (FIG. 2B) and the rectifying lighting 2 (FIG. 2C) have asymmetric waveforms.
[0022]
In this manner, the reference voltage on the high threshold side of the comparator unit COMP composed of the comparators IC2 and IC3 in FIG. 1 is set to, for example, 8V, and the reference voltage on the low threshold side is set to 6V. If the resistors R12, R13, and R14 are set in advance, the DC voltage set corresponding to the rectification lighting 1, the rectification lighting 2, and the non-lighting and no-load conditions is applied to the comparator when the all-lights are normally lit. When the all-lights are normally lit, the outputs of the comparators IC2 and IC3 are both HI and the transistor Q3 of the control signal output unit VOUTa is in the ON state, so that the oscillation stop signal is input to the terminal 5 of the IV control circuit IC1. Is not output and all-light normal lighting can be continued.
[0023]
On the other hand, in rectification lighting 1, the output of the comparator IC2 is output, and in rectification lighting 2 and non-lighting and no load, the output of the comparator IC3 becomes LO and the transistor Q3 is turned off, so that the oscillation stop signal is output to the terminal 5 of the IV control circuit IC1. It is output and stops the oscillation of the inverter circuit IV. When rectifying lighting or non-lighting, the excessive current to the ballast choke T1 and the starting capacitor C3 is cut off to prevent the circuit from being destroyed. The high frequency voltage generated at the time can be turned off.
[0024]
Next, the operation of the lamp voltage abnormal rise protection means NP1B will be described with reference to FIGS.
FIG. 3A shows a lamp voltage waveform during normal lighting, and FIG. 3B shows a lamp voltage waveform when the lamp LA rises abnormally due to non-rectified lighting.
The rectifying lighting protection means NP1A protects against rectifying lighting in which the high-frequency lamp current waveform of the lamp LA has an asymmetrical waveform as shown in FIGS. 2B and 2C. However, as shown in FIG. Is non-rectified lighting and the voltage rises abnormally, the lamp voltage waveform is symmetrical and cannot be protected, so that the lamp LA can also be protected when the voltage rises abnormally due to the non-rectified lighting. The abnormal increase in the voltage due to the non-rectified lighting has a low probability of occurrence and is caused by an abnormality in the gas filled in the lamp LA.
[0025]
The high-frequency voltage at both ends of the lamp LA is applied to the capacitor C6 by dividing the voltage by the capacitance ratio of the capacitors C5 and C6, and corresponds to the peak of the high-frequency voltage waveform of the capacitor C6 due to the rectification of the diodes D1 and D2. A DC voltage is generated on the capacitor C7.
Here, when the voltage of the lamp LA rises abnormally due to non-rectified lighting and the lamp voltage exceeds the peak voltage at the time of normal lighting as shown in FIG. 3B, the constant voltage diode DZ3 operates and the IV control circuit IC1 An oscillation stop signal is output to the terminal 5 of the inverter circuit, and the value of the resistor R3 is determined so as to stop the oscillation of the inverter circuit IV. An oscillation stop signal, which is a current rectified and smoothed by the diodes D1 and D2 and the capacitor C7, is output to the terminal 5 of the circuit IC1 via the resistor R3 and the diode D3 to the terminal 5 of the IV control circuit IC1. Stop.
[0026]
As described above, it is possible to avoid the continuation of the abnormal state with respect to the rectified lighting, the abnormal voltage rise of the non-rectified lighting lamp, the start failure, and the like caused by the end of the lamp LA life and the lamp failure due to the simple circuit. In addition, it is possible to prevent the occurrence of malfunctions of the device and the lamp.
Further, the start of the lamp can be detected by a change in the output of the rectifying lighting protection means NP1A, and the circuit can be simplified.
[0027]
Embodiment 2 FIG.
FIG. 4 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention, and FIG. 5 is a waveform diagram of lamp voltage showing operation.
In the present embodiment, a level shift unit for controlling the operation sensitivity of the lamp voltage abnormal rise protection means NP1B of the first embodiment to decrease until the lamp is started is added.
4, the same or corresponding parts as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0028]
In the level shift unit LVS, the base of the transistor Q4 is connected to both output terminals of the comparators IC2 and IC3 of the comparator unit COMP via the resistor R19, the collector is connected to the control power supply capacitor C1 via the resistor R23, and the anode is connected to the power supply E. Is connected to the negative electrode.
The base of the transistor Q5 is connected to the collector of the transistor Q4 via the resistor R21, the collector is connected to the connection point of the resistor R3 and the diode D3 of the lamp voltage abnormal rise protection function NP1B via the resistor R20, and the anode is connected to the negative electrode of the power supply E. It is connected.
The base of the transistor Q6 is connected to the collector of the transistor Q4 via the resistor R22, the collector is connected to the collector of the transistor Q3, and the anode is connected to the negative electrode of the power supply E.
[0029]
In the frequency control circuit FC2, in the frequency control circuit FC1 shown in FIG. 1 of the first embodiment, a preheating oscillation resistor R4 as a preheating control unit and a preheating oscillation are connected between the terminal 6 of the IV control circuit IC1 and the negative electrode of the DC power supply E. The series circuit of the capacitor 13 is connected.
[0030]
The control signal output part VOUTb of the rectification lighting protection means NP1A is the same as the control signal output part VOUTa of the first embodiment shown in FIG. Is additionally connected.
[0031]
Next, the operation of the discharge lamp lighting device according to the second embodiment of the present invention will be described with reference to FIGS. The overall operation is the same as that of the first embodiment, and a description thereof will be omitted. The operations of the rectifying lighting protection means NP1A, the lamp voltage abnormal rise protection means NP1B, the level shift unit LVS, and the frequency control circuit FC2 will be mainly described.
FIG. 5A shows a high-frequency envelope voltage waveform between both electrodes F1 and F2 of the lamp LA, and FIGS. 5B to 5D show voltage waveforms at the terminal 5 of the IV control circuit IC1. 5C shows the case of normal lighting of the normal lamp, FIG. 5C shows the case of abnormal voltage rise of the non-rectified lighting of the abnormal lamp, and FIG.
[0032]
First, in FIG. 4, when the inverter circuit IV is connected to the DC power supply E and the charged voltage of the control power supply capacitor C1 reaches the oscillation start voltage of the IV control circuit IC1, the IV control circuit IC1 starts oscillating. At this time, the terminal 6 of the IV control circuit IC1 has a constant DC voltage, and a current flows out from the terminal 6 via the main oscillation resistor R2 and the preheating oscillation resistor R4. The current of the preheating oscillation resistor R4 is The preheating oscillating capacitor C13 is charged and decreases with time. The IV control circuit IC1 has a characteristic that the oscillation frequency is higher as the outflow current from the terminal 6 is larger. Therefore, as the outflow current from the terminal 6 decreases, the IV control circuit IC1 first oscillates at a higher frequency. Starting, the oscillation frequency is controlled so as to gradually decrease to a predetermined frequency.
[0033]
Next, the inter-electrode voltage of the lamp LA will be described with reference to FIG. In the case of normal lighting (dotted line), when the DC power supply E is turned on, the IV control circuit IC1 starts oscillating at a frequency higher than the resonance frequency, but as shown in FIG. Is set to a voltage VE lower than the starting voltage VA1 of the discharge lamp LA, so that the lamp LA is not turned on and the electrodes F1 and F2 are preheated by the resonance current flowing through the electrodes F1 and F2 of the discharge lamp LA. You.
[0034]
Then, when the oscillation frequency of the IV control circuit IC1 decreases, the voltage between the electrodes of the lamp LA increases. During normal lighting, when the voltage between the electrodes of the lamp LA reaches VA1 at time t1, the lamp LA starts ( The preheating time is from time t0 to t1). When the lamp LA is turned on, the impedance of the lamp LA changes, and the voltage between both poles of the lamp LA is reduced to VA2 and the lighting is continued.
[0035]
On the other hand, when the voltage of the lamp LA rises abnormally due to non-rectified lighting due to defective manufacturing (dashed line), as shown in FIG. 5A, the voltage increases from VE to VB1 between time t0 and time t2, and the lamp LA increases. The voltage between both poles of the lamp LA decreases to VB2 due to the impedance change of the lamp LA, but the oscillation of the inverter circuit IV is stopped at time t3 by the non-rectification abnormal lighting protection means NP1B described later.
When the lamp LA is turned off at the end of its life when the high voltage is applied (solid line), the voltage rises from VE to VC1 between time t0 and time t4 as shown in FIG. The oscillation of the inverter circuit IV is stopped by the means NP1B.
[0036]
Next, the operation of the rectification lighting protection means NP1A, the lamp voltage abnormal rise protection means NP1B, and the level shift unit LVS for the lighting state of the lamp LA will be described.
In the case of normal lighting, in the rectification lighting protection means NP1A, since the lamp LA is not lit from the time t0 to the lighting time t1 of the lamp LA, almost no voltage is generated in the coupling capacitor C4. No voltage is detected, the outputs of the comparators IC2 and IC3 become LO, and the transistor Q3 of the control signal output unit VOUTa is off.
[0037]
On the other hand, in the level shift unit LVS, from the time t0 to the lighting time t1 of the lamp LA, the transistor Q4 is turned off, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q5 via the resistors R23 and R21, and the transistor Q5 Is on. Further, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q6 via the resistors R23 and R22, and the transistor Q6 is turned on.
[0038]
For this reason, the oscillation stop signal from the non-rectification abnormal lighting protection means NP1B is output to the terminal 5 of the IV control circuit IC1 by the divided voltage of the resistors R3 and R20, and as shown in FIG. The terminal 5 is kept at a low potential and is at a level sufficiently lower than the threshold value V (TH) at which the oscillation of the inverter circuit stops, and the oscillation of the inverter circuit IV does not need to be rectified even if there is unnecessary operation. No oscillation stop signal is output from the means NP1B to the terminal 5 of the IV control circuit IC1, and at time t1, the lamp LA is lit at the voltage Va1 without any trouble.
At this time, the oscillation stop signal from the rectification lighting protection means NP1A is not output to the terminal 5 of the IV control circuit IC1, and the oscillation of the inverter circuit IV is continued.
[0039]
Next, when the lamp LA is turned on at the time t1, the impedance of the lamp LA changes and the voltage between both ends of the lamp LA decreases, so that the voltage becomes Va2. At this time, in the rectification lighting protection means NP1A, the voltage generated in the coupling capacitor C4 is detected by the voltage detection unit VIN, the outputs of the comparators IC2 and IC3 are inverted to HI, and the transistors Q3 and Q4 are turned on. When the transistor Q4 is turned on, no current is supplied to the bases of the transistors Q5 and Q6, and the transistors Q5 and Q6 are turned off. As shown in FIG. 5B, the voltage at the terminal 5 of the IV control circuit IC1 is reduced to Va3. Level. However, in normal lighting, the level is lower than the threshold value V (TH), and the oscillation stop signal is not output from the non-rectified abnormal lighting protection means NP1B to the terminal 5 of the IV control circuit IC1, and the lamp LA is turned on even after time t1. The state continues.
[0040]
Next, when the voltage of the lamp LA rises abnormally due to the non-rectified lighting of the lamp LA, as shown in FIG. 5C, in the rectified lighting protection means NP1A, the lamp LA is switched from the time t0 to the lighting time t1 of the lamp LA. Since it is not lit, the transistor Q3 of the control signal output unit VOUTb is off.
In the level shift unit LVS, from time t0 to the lighting time t1 of the lamp LA, the transistor Q4 is turned off, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q5 via the resistors R23 and R21, and the transistor Q5 Is on. Further, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q6 via the resistors R23 and R22, and the transistor Q6 is turned on.
[0041]
Therefore, the oscillation stop signal from the non-rectification abnormal lighting protection means NP1B is output to the terminal 5 of the IV control circuit IC1 by the divided voltage of the resistors R3 and R20, so that the potential of the terminal 5 of the IV control circuit IC1 becomes low. It is kept at a level sufficiently lower than the threshold value V (TH) at which the oscillation of the inverter circuit stops, and the oscillation of the inverter circuit IV does not need to be performed. 5, no oscillation stop signal is output, and at time t2, the lamp LA is turned on at the voltage Vb1.
[0042]
Next, when the lamp LA is turned on at the time t2, the impedance of the lamp LA changes and the voltage between both ends of the lamp LA decreases. At this time, the outputs of the comparators IC2 and IC3 of the rectification lighting protection means NP1A are inverted, and the transistors Q3 and Q4 are turned on. When the transistor Q4 is turned on, no current is supplied to the bases of the transistors Q5 and Q6, and the transistors Q5 and Q6 are turned off. As shown in FIG. 5 (c), the voltage of the terminal 5 of the IV control circuit IC1 becomes as high as Vb3. Since the level is shifted to the threshold value V (TH), the non-rectification abnormal lighting protection means NP1B outputs an oscillation stop signal to the terminal 5 of the IV control circuit IC1, and the oscillation of the inverter circuit IV is stopped at time t4.
[0043]
Next, when the lamp LA is not turned on at the end of life or the like when the high voltage is applied, as shown in FIG. 5D, the lamp LA is not turned on from the time t0 to the time t4 in the rectification lighting protection means NP1A. The transistor Q3 of the control signal output unit VOUTb is off.
In the level shift unit LVS, from time t0 to lighting time t4 of the lamp LA, the transistor Q4 is turned off, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q5 via the resistors R23 and R21, and the transistor Q5 Is on. Further, the voltage of the control power supply capacitor C1 is supplied to the base of the transistor Q6 via the resistors R23 and R22, and the transistor Q6 is turned on.
[0044]
Therefore, the oscillation stop signal from the non-rectification abnormal lighting protection means NP1B is output to the terminal 5 of the IV control circuit IC1 by the divided voltage of the resistors R3 and R20, so that the potential of the terminal 5 of the IV control circuit IC1 becomes low. However, since the lamp LA is not lit and has a high voltage and reaches the threshold value V (TH), the non-rectification abnormal lighting protection means NP1B outputs an oscillation stop signal to the terminal 5 of the IV control circuit IC1. Stops the oscillation of the inverter circuit IV.
[0045]
As described above, at the time of starting the lamp, the level shift unit LVS can obtain a high voltage required for starting the lamp, and can prevent an inverter failure due to abnormal high voltage generation that occurs when the lamp does not start. , The level shift unit LVS can be realized by also using the circuit of the lamp voltage abnormal rise protection means NP1B.
Further, the start of the lamp can be detected by a change in the output of the rectifying lighting protection means NP1A, and the circuit can be simplified.
[0046]
Embodiment 3 FIG.
FIG. 6 is a circuit diagram of a discharge lamp lighting device according to Embodiment 3 of the present invention, and FIG. 7 is a voltage waveform diagram of a capacitor C7 corresponding to a lamp voltage.
In this embodiment, the function of the rectification lighting protection means NP1A and the function of the lamp voltage abnormal rise protection means NP1B are removed for a certain period of time after the discharge lamp lighting circuit is turned on after the level shift means of FIG. This is one in which a mask portion MSK for masking is added.
6, the same or corresponding parts as those in FIG. 4 of the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.
[0047]
As shown in FIG. 6, a mask section MSK is provided in the protection circuit NP3. The mask circuit MSK includes a timer circuit TM including resistors R25 and R26, a capacitor C14, and a constant voltage diode DZ5, and an oscillation stop terminal of the IV control circuit IC1. The transistor Q7 is connected between the transistor 5 and the negative terminal of the DC power supply E. The input terminal of the transistor Q7 is connected to the output terminal of the transistor Q8 driven by the output of the timer circuit TM. A Zener diode DZ5 is connected between the base of the transistor Q8 and a connection point between the resistor R25 and the capacitor C14, and the collector of the transistor Q8 is connected to the control power supply capacitor C1 via the resistor R24.
[0048]
When the discharge lamp lighting device is turned on, the mask portion MSK charges the capacitor C14 via the resistors R25 and R26, and after a predetermined time, when the voltage of the capacitor C14 exceeds the Zener voltage of the constant voltage diode DZ5. The transistor Q8 is turned on and the transistor Q7 is turned off. In order to drive the timer circuit TM, the positive side of the resistor 25 is connected to the control power supply capacitor C1, and to drive the transistor Q7, a resistor R17 is connected between the control power supply capacitor C1 and the base of the transistor Q7. I have.
[0049]
Next, the operation of the mask section MSK and the frequency control circuit FC2 will be described with reference to FIGS.
First, in FIG. 6, when the inverter circuit IV is connected to the DC power supply E and the charged voltage of the control power supply capacitor C1 reaches the oscillation start voltage of the IV control circuit IC1, the IV control circuit IC1 starts oscillating. Since the IV control circuit IC1 has a characteristic that the oscillation frequency increases as the current flowing out of the terminal 6 increases, the IV control circuit IC1 initially operates at a high frequency as the current flowing out of the terminal 6 decreases. Oscillation is started and the oscillation frequency is controlled so as to gradually decrease to a predetermined frequency.
[0050]
The oscillation frequency when the IV control circuit IC1 first oscillates after the DC power supply E is turned on starts oscillating at a frequency higher than the resonance frequency of the ballast choke T1 and the starting capacitor C3. On the other hand, at this time, the voltage between the two poles of the lamp LA is set to a voltage VE lower than the starting voltage VA1 of the lamp LA as shown in FIG. That is, the electrodes F1 and F2 are preheated by the resonance current flowing through the electrodes F1 and F2 of the lamp LA.
[0051]
When the oscillation frequency of the IV control circuit IC1, that is, the switching frequency of the switching elements Q1 and Q2 gradually decreases, the voltage between the electrodes of the lamp LA gradually increases, and as shown in FIG. When the voltage of the capacitor C7 corresponding to the voltage between both electrodes of the lamp LA reaches VA1, the lamp LA is started (therefore, the preheating time is from time t0 to t1). When the lamp LA is turned on, the impedance of the lamp LA changes, the frequency decreases, and the voltage of the capacitor C7 decreases to VA2. Thereafter, the frequency decreases to a steady state in response to the decrease in the oscillation frequency of the IV control circuit IC1, and the lamp LA continues to be lit with a predetermined lamp current determined by the impedance of the ballast choke T1.
[0052]
On the other hand, the operation of the rectification lighting protection means NP1A during this time is such that in the case of normal lighting, as shown in FIG. 7A, the lighting is not performed from the on time t0 of the DC power supply E to the lighting time t1 of the lamp LA. Accordingly, the transistor Q3 is off, but until the capacitor C14 of the timer circuit TM is charged to the predetermined voltage, the transistor Q8 is off and the transistor Q7 is on, so that the potential of the terminal 5 is low. Will be kept. If the mask portion MSK is not provided, the transistor Q3 is turned off during the preheating time, so that the oscillation stop signal is output from the rectification lighting protection means NP1A to the IV control circuit IC1, and the lamp LA cannot be turned on. Since the potential of the terminal 5 is kept at the low potential even during the preheating time by the mask portion MSK, the oscillation stop signal is not output from the rectification lighting protection means NP1A to the terminal 5 of the IV control circuit IC1, and the lamp LA does not interfere at the time t1. It is lit without.
[0053]
When the voltage charged in capacitor C14 from control power supply capacitor C1 via resistor 25 reaches the Zener voltage of constant voltage diode DZ5 at time t5, transistor Q8 turns on and transistor Q7 turns off (accordingly, from time t0 to t5). Up to the masking time of the rectifying lighting protection circuit NP3 by the masking section MSK, which is set to be longer than the preheating time). However, at time t5, the lamp LA is already lit, and the transistor Q3 is turned on. Then, the oscillation stop signal is not output from the rectification lighting protection means NP3, and the lighting state is continued.
[0054]
On the other hand, when the voltage of the lamp LA rises abnormally due to the non-rectified lighting of the lamp LA, the rectified lighting protection means NP1A does not light the lamp LA from the time t0 to the lighting time t2 of the lamp LA. Is off.
Further, since the potential of the terminal 5 is kept at a low potential until the mask time t5 of the mask section MSK, the lamp LA is turned on at the time t2.
[0055]
Next, when the lamp LA is turned on at the time t2, since the mask time t5 of the mask section MSK has not come, the oscillation stop signal is not output from the non-rectification abnormal lighting protection means NP1B to the terminal 5 of the IV control circuit IC1. After time t5, an oscillation stop signal is output, and the oscillation of the inverter circuit IV is stopped.
[0056]
Next, when the lamp LA is not turned on at the end of its life or due to a failure, as the oscillation frequency of the IV control circuit IC1 decreases from the initial oscillation frequency to the steady state frequency, the voltage of the capacitor C7 becomes as shown in FIG. As described above, between time t0 and time t5, the voltage rises from VE to VD1 and becomes constant thereafter. During this time, it corresponds to the non-lighting state, and the transistor Q3 of the rectification lighting protection means NP1A is off. However, in the non-lighting state, the transistor Q3 is off after time t2, so that the mask time of the mask portion MSK When the transistor Q7 is turned off at the time t5 when the operation ends, an oscillation stop signal is output from the rectification lighting protection means NP1A to the terminal 5 of the IV control circuit IC1, the oscillation of the inverter circuit IV stops, and the ballast choke T1 and the starting capacitor C3 Blocking the excessively large resonance current from flowing continuously.
[0057]
Next, even when the mask time t5 of the mask section MSK is reached, at time t5, the lamp LA is already lit, the transistor Q3 is turned on, and the oscillation stop signal is output from the rectification lighting protection means NP3. And the lighting state is continued.
[0058]
As described above, since the mask portion MSK for masking the oscillation stop signal so as not to output the oscillation stop signal for a certain period of time after the DC power supply E is turned on is provided, the discharge lamp lighting device having the function of lighting the lamp LA after preheating the electrodes F1 and F2. Especially in a short time, the present invention can be applied to a lamp having no problem even if the voltage for starting the lamp continues to be generated, and a normal discharge lamp can be reliably turned on, and in the case of an abnormality, oscillation can be surely stopped. .
[0059]
【The invention's effect】
As described above, according to the present invention, a DC power supply, an inverter circuit for converting the DC voltage of the DC power supply to a high-frequency voltage, a ballast choke, and a coupling capacitor connected to the ballast choke via a lamp are provided. A discharge lamp load circuit for lighting the lamp with the high-frequency current from the inverter circuit; and detecting the asymmetry of the lamp current during lamp rectification lighting based on the voltage level of the coupling capacitor. Rectifying and lighting protection means for controlling the oscillation of the inverter circuit based on the current of the lamp, and detecting the lamp voltage at the time of lamp non-rectified lighting based on the voltage level of the lamp, and oscillating the inverter circuit based on the detected voltage And a lamp abnormality protection circuit having a lamp voltage abnormal rise protection means to be controlled. By avoiding the continuation of this abnormal state, all lamp abnormalities that can occur due to the end of lamp life or lamp failure, such as rectified lighting and non-rectified lighting, abnormal voltage rise of the lamp and inability to start, etc. It is possible to prevent malfunction of the device and the lamp.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 2 is a lamp current waveform diagram during normal all-light lighting and rectifying lighting of the discharge lamp lighting device according to the first embodiment of the present invention.
FIG. 3 is a lamp voltage waveform diagram of the discharge lamp lighting device according to Embodiment 1 of the present invention during normal lighting of all light and during non-rectified lighting.
FIG. 4 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention.
FIG. 5 is a lamp current waveform diagram and a terminal voltage waveform diagram of the discharge lamp lighting device according to the second embodiment of the present invention.
FIG. 6 is a circuit diagram showing a configuration of a discharge lamp lighting device according to Embodiment 3 of the present invention.
FIG. 7 is a voltage waveform diagram of a capacitor C7 corresponding to a lamp voltage of the discharge lamp lighting device according to the third embodiment of the present invention.
[Explanation of symbols]
C4 coupling capacitor, E DC power supply, FC1, FC2 frequency control circuit, IV inverter circuit, 1C1 IV control circuit, LA lamp, LAC discharge lamp load circuit, LVS level shift section, MSK mask section, NP1, NP2, NP3 Lamp abnormality Protection circuit, NP1A Rectification lighting protection means, NP1B Lamp voltage abnormal rise protection means, T1 ballast choke.

Claims (4)

DC power supply,
An inverter circuit for converting the DC voltage of the DC power supply to a high-frequency voltage;
A ballast choke, a discharge lamp load circuit having a coupling capacitor connected to the ballast choke via a lamp, and lighting the lamp by a high-frequency current from the inverter circuit;
The voltage level of the coupling capacitor detects the asymmetry of the lamp current at the time of lamp rectification lighting, the rectification lighting protection means for controlling the oscillation of the inverter circuit based on the detected asymmetric current, and the voltage level of the lamp. A lamp abnormality protection circuit having a lamp voltage abnormality detection means for detecting a lamp voltage during non-rectified lighting of the lamp and controlling oscillation of the inverter circuit based on the detected voltage;
A discharge lamp lighting device comprising: The inverter circuit includes a preheating control unit that preheats the electrodes of the lamp before starting the lamp,
The lamp voltage abnormal rise protection means of the lamp abnormality protection circuit stops the oscillation of the inverter circuit when the peak-to-peak voltage of the lamp voltage exceeds a predetermined threshold value,
A level shift unit for lowering the operation sensitivity of the lamp voltage abnormal rise protection unit until the lamp is started,
The discharge lamp lighting device according to claim 1, wherein the rectification lighting protection means is not operated until the lamp is started. 2. The discharge lamp lighting device according to claim 1, further comprising a mask portion for preventing the lamp abnormality protection circuit from operating for a certain period of time that is sufficiently longer than the lamp start time after the DC power is turned on. The discharge lamp lighting device according to any one of claims 1 to 3, wherein the start of the lamp is detected by an output change of a rectification lighting protection function.

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