JPH0417296A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To start lighting of a discharge lamp securely with a simple configuration by using a resonant circuit to have a resonant condenser generate high voltage. CONSTITUTION:After DC power supply 1 is made, an inverter circuit 2 oscillates at a low frequency and applies low frequency voltage to a choke coil 3 and the resonant circuit of a condenser 4. Then high-frequency resonant voltage generated by the resonant circuit is superimposed, and a lamp voltage detector circuit 6 detects this resonant voltage. A lighting control circuit 8 changes the oscillating frequency of the inverter circuit 2 into a higher frequency by means of the detected voltage to have the condenser 4 generate high resonance voltage by its resonant circuit. The subsequently generated high resonance voltage actuates a discharge lamp 5. Thus, start of lighting can be securely carried out with a simple configuration.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device for controlling the lighting of a discharge lamp such as a metal halide lamp.

Prior Art A relatively high voltage is applied between a pair of electrodes of a discharge lamp to reduce or substantially eliminate the deleterious electrophoretic and acoustic resonance effects that commonly occur during operation of discharge lamps such as metal halide lamps. A square wave current having a magnitude within a predetermined range and a predetermined repetition rate is applied to the pair of electrodes in order to excite the excitable component enclosed in the discharge lamp and thereafter maintain this excitation. supply,
Furthermore, a method of periodically and alternately changing the direction in which the rectangular wave current is supplied to the electrodes has already been disclosed in Japanese Patent Application Laid-Open No.
It is known from the publication No.-10697.

Problems to be Solved by the Invention However, as seen in the published publications, the apparatus for carrying out the above method is extremely complicated and is extremely disadvantageous in practice.

The present invention solves the above problem by using a resonant circuit,
It is an object of the present invention to provide a discharge lamp lighting device that has a simple configuration and can be started reliably.

Means for Solving the Problems In order to solve the above problems, the lamp lighting device of the present invention includes a DC power source, an inverter means that is driven by the DC power source to oscillate, and a choke coil connected to the inverter means. a resonant circuit consisting of a series circuit of capacitors, a discharge lamp connected to a connection point between the choke coil and the capacitor, a lamp characteristic detecting means for detecting at least one of a lamp voltage and a lamp current, and an output of the lamp characteristic detecting means. and lighting control means for controlling lighting of the discharge lamp by varying the oscillation frequency or duty ratio of the inverter means based on a signal.

Further, the resonant circuit of the present invention includes a series circuit of a first capacitor, a choke coil, and a second capacitor, and the discharge lamp is connected to a connection point between the choke coil and the second capacitor, and the discharge lamp is connected to the connection point of the choke coil and the second capacitor. The capacitance of the second capacitor is larger than that of the second capacitor.

Further, the inverter means of the present invention oscillates at a low frequency when the DC power is turned on, the lamp voltage detection means detects a voltage in which a high frequency resonant voltage is superimposed on the low frequency voltage generated at this time, and the lighting control means The oscillation frequency of the inverter means is changed to a high frequency based on the signal detected by the lamp voltage detection means, thereby generating a high resonant voltage in the resonant circuit.

Furthermore, the lighting control means of the present invention has means for gradually changing and lowering the oscillation frequency of the inverter means when the discharge lamp is started by a high resonant voltage generated in the resonant circuit.

Furthermore, the lighting control means of the present invention has a sawtooth wave generation means or a triangular wave generation means, and when changing the oscillation frequency of the inverter means to a higher frequency, it responds to the output voltage of the sawtooth wave generation means or the triangular wave generation means. The oscillation frequency is changed within a predetermined range.

Furthermore, the lighting control means of the present invention has a starting voltage timer means that operates when the inverter means oscillates at a high oscillation frequency and stops the oscillation of the inverter means when the oscillation frequency of the inverter means does not decrease within a predetermined time. It is something.

Furthermore, the choke coil of the present invention has a center gap between the center legs of a pair of opposing cores, or the choke coil has a space gap between the center legs and both end legs of a pair of opposing cores. be.

Effect With the above configuration, when the lighting control means changes the oscillation frequency of the inverter means, a high resonant voltage is generated in the capacitor at a high frequency of, for example, around 100 KHx by the choke coil and the capacitor, and the discharge lamp is started.
The lamp characteristic detection means detects activation, and after activation, l0KH! flows through the choke coil. The discharge lamp is started and lit by the low frequency currents before and after. In this way, the discharge lamp can be reliably started by generating a high voltage in the capacitor of the resonant circuit.

Also, when a series inverter is used as the inverter means, the capacitance of the second capacitor for resonance is 10
By connecting the first capacitor for current reversal, which has a capacity more than twice as large, to the resonant circuit of the choke coil and the second capacitor, the choke coil and the second capacitor similarly cause a high frequency A high resonant voltage is generated in the second capacitor, and the discharge lamp can be reliably started.

In addition, when the DC power is turned on, the inverter means oscillates at a low frequency, and the low frequency voltage generated at this time is superimposed on the high frequency resonant voltage generated by the resonant circuit of the choke coil and the capacitor. is detected by the lamp voltage detection means, and this detected voltage causes the inverter means to oscillate at a high frequency, and the even higher resonant voltage generated at this time starts the discharge lamp, so that the transition from turning on the DC power to starting the lamp is completed. It is done smoothly.

Furthermore, when transitioning from startup to lighting, the oscillation frequency of the inverter means is not lowered all at once to the original low frequency.
By gradually decreasing the resonant voltage, it is possible to avoid stopping the starting due to a sudden decrease in the resonant voltage.

Furthermore, when changing the oscillation frequency of the inverter means to a higher frequency, the oscillation frequency of the inverter means is changed to a frequency within a predetermined range including the resonance frequency determined by the choke coil and the capacitor using the sawtooth wave generation means or the triangular wave generation means. Therefore, even if the inductance of the choke coil or the capacitance of the capacitor varies or shifts, it is possible to generate a high resonant voltage that will ensure startup. As a result, the resonance voltage is generated for a short period of time, and a large current does not flow for a long period of time, thereby improving the reliability of the components and preventing a drop in the output voltage of the DC power supply.

Furthermore, when the resonance voltage continues to be generated for a predetermined period of time, the activation timer means stops the oscillation of the inverter means, thereby preventing damage to the lighting device and ensuring safety.

Furthermore, by providing a center gap between the center legs of a pair of opposing cores of the choke coil, or by providing a space gap between the center legs and both end legs of a pair of opposing cores of the choke coil, the inductance of the choke coil can be reduced. saturation is avoided, which prevents large current from flowing through the choke coil and damaging the discharge lamp.In addition, when a center gap is used, leakage flux can be particularly reduced, and changes in inductance due to surrounding influences can be prevented. It can be made smaller, and when a space gap is used, the two cores can be separated, making it easier to insulate the cores.

Example An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing the basic configuration of a discharge lamp lighting device according to an embodiment of the present invention. In FIG. 1, 1 is a DC power supply, and an inverter circuit 2 is driven by the DC power supply 1 to oscillate a clock signal of a predetermined frequency. The inverter circuit 2 includes a resonant circuit consisting of a choke coil 3 and a resonant capacitor 4 in series as a load circuit, and a discharge lamp 5 such as a metal highland lamp connected to the connection point between the choke coil 3 and the capacitor 4. It has Furthermore, the load circuit includes a lamp voltage detection circuit 6 which is connected in series to the resonant circuit to detect the startup of the discharge lamp 5 and detects the lamp voltage for controlling subsequent startup and rated lighting, and a current flowing through the load circuit. A lamp current detection circuit 7 is provided to detect the current. The output signals of the lamp voltage detection circuit 6 and the lamp current detection circuit 7 are input to the lighting control circuit 8, and the lighting control circuit 8 varies the oscillation frequency of the inverter circuit 2 or its duty ratio based on these signals, and controls the discharge lamp 5. Controls the lighting operation of the

Next, the operation of the above configuration will be explained. When the DC power supply 1 is turned on, the inverter circuit 2 first receives 2 KH! It oscillates at a relatively low frequency, and this low frequency voltage is applied to the resonant circuit of the choke coil 3 and the capacitor 4. A high frequency resonant voltage generated by the resonant circuit is superimposed on the low frequency voltage generated at this time, and the lamp voltage detection circuit 6 connected to the resonant circuit detects this resonant voltage, and the lighting control circuit 8 uses this detected voltage to invert the inverter. The oscillation frequency of the circuit 2 is changed to a high frequency, and the resonant circuit generates a high resonant voltage in the capacitor 4 at a high frequency around IGQKlh, for example. At this time, the discharge lamp 5 is activated by the high resonant voltage generated in the capacitor 4, and a large amount of current flows through the discharge lamp 5. When current flows through the discharge lamp 5, the voltage across the discharge lamp 5 decreases. At this time, the lamp voltage detection circuit 6 detects that the discharge lamp 5 has started by detecting a sudden decrease in the current flowing through the capacitor 4 from the voltage drop in the lamp voltage detection circuit 6, and the lighting control circuit 8 controls the oscillation frequency of the inverter circuit 2 to a low frequency around loKHx based on the detected voltage of the lamp voltage detection circuit 6, and when the lamp voltage is low, the oscillation frequency of the inverter circuit 2 is lowered and the choke coil 3 through discharge lamp 5
When the lamp voltage is high, the oscillation frequency of the inverter circuit 2 is increased, and the current flowing to the discharge lamp 5 through the choke coil 3 is decreased to control the discharge lamp 5 to be lit at its rated value.

The choke coil 3 has a configuration as shown in FIG. 2 to prevent the inductance from becoming saturated, since if the inductance is saturated, a large current will flow and damage the discharge lamp 5. FIG. 2(a) shows a configuration in which the center legs of a pair of opposing cores 9a of the choke coil 3 have a center gap 10a, and FIG. Figure 3 shows a configuration with a space gap tab through both end legs. Figure 2(a)
This type has less leakage magnetic flux at both end legs, and the change in inductance value due to the influence of the surroundings is small. In addition, Fig. 2 (b
) is easy to insulate the core.

FIG. 3 is a circuit diagram showing the main parts of the inverter circuit 2.

In FIG. 3, the inverter circuit 2 is connected to the choke coil 3.
, a capacitor 4, and an external circuit 11 consisting of a discharge lamp 5. Four switching transistors Q7. Q2.
Q3. It has a bridge inverter configuration consisting of Q4. 12 is a drive circuit for driving this bridge inverter, and both ends of the primary winding of the drive transformer DT are connected to drive transistors Q5. Q6 and the drive transistors Q1. The gate of Q6 is inputted with clocks E, E2 having an oscillation frequency of about 2K)lr and whose phases are inverted to each other, and a drive voltage VD is applied to the midpoint of the negative winding. Four secondary windings are provided on the secondary side of the drive transformer DT, each having one end connected to a resistor R13, R1, R+7. R19 and
Diodes D3, D4 . D6
．． Db and resistance R, □, R+4. R-engineer. , R1
Four switching transistors Q, , Q2 . . . constitute a bridge inverter through 8 series circuits. Q...
Connected to the gate of Q4. Further, a series circuit of switching transistors Q1 and Q2 and a series circuit of switching transistors Q3 and Q4 are interposed between the DC power supply voltage VDD and the ground line of the bridge. An external circuit 11 is interposed between the connection points of Q4. The other end of the secondary winding connected to the gate of the switching transistor Q1 is connected to the transistors Q, ,Q
2, the switching transistor Q3
The other end of the secondary winding connected to the gate of transistor Q
3. Q4 is connected to the connection point of switching transistor Q2. The other ends of the secondary windings connected to the respective gates of Q4 are connected to the ground line A of the bridge and are floating above the ground GND. As a result, a pair of diagonally opposing switching transistors Q, , Q4 and switching transistors Q2 . Q3 is one Q.

When Q4 turns on at the same time, the other 02. Q3 is OF at the same time
It is configured to do F.

C2 is a voltage detection capacitor that constitutes the lamp voltage detection circuit 6 in FIG. The voltage generated across the capacitor C2 is detected as the lamp voltage of the discharge lamp 5. That is, a series circuit of capacitor C3, resistors R2, and R3 is connected between the input side of voltage detection capacitor C2 and earth GND, and a series circuit of capacitor C4, resistor R4, and variable resistor R3 is connected between the output side and earth GND. , a voltage detection terminal VL1°V L2 is taken out from the connection point of resistors R2 and R3 and the connection point of resistor R4 and variable resistor R6, respectively, and the difference between them is the detected voltage by the voltage detection capacitor C2 and the lighting shown in FIG. It is input to the control circuit 8.

Furthermore, the other end of the switching transistor Q2.04 is connected to the ground GND via a resistor R7, and is also connected to the current detection terminal IDC via a resistor R6. The lamp current detection circuit 7 of FIG. 1 is configured together with the capacitor C5 interposed between the two. IP is a lamp instantaneous current terminal taken out from the input side of this lamp current detection circuit.

Now, in the primary winding of the drive transformer DT, a clock El with an oscillation frequency of about 2K82 whose phases are inverted,
E2 is applied, for example switching transistor Q
, , Q4 are turned ON at the same time, a current in the direction (A) flows through the resonant circuit of the external circuit 11, and when the next clock is inverted, the switching transistors Q2 . When Q and Q are turned on at the same time, a current in the (b) direction flows through the resonant circuit of the external circuit 11.

2 KH at this time! A high frequency resonant voltage is superimposed on a low frequency voltage, and the voltage detection capacitor C2
When this voltage is detected, the oscillation frequency of the inverter circuit 2 changes to, for example, 100KH! A high resonant voltage is generated in the capacitor 4 at high frequencies before and after, the discharge lamp 5 is activated, and a large amount of current flows through the discharge lamp. therefore,
The potential difference between the voltage detection terminals VL, VL2 rapidly decreases, thereby detecting the activation of the discharge lamp.

Note that diodes D3. D4. D.

D6 and resistors R,3, R11, R, . . . R,9 are provided to provide a time delay during inversion so as to prevent switching diodes Q1, Q2, Q, and Q4 from turning on at the same time.

Further, although the configuration of a bridge inverter is shown in this embodiment, a half-bridge inverter having a configuration in which the switching transistors Q, Q4 are replaced with capacitors can also operate in the same manner.

FIG. 4 is a circuit diagram showing a specific example of the configuration of the lighting control circuit 8. As shown in FIG. In FIG. 4, reference numeral 13 denotes a voltage detection terminal VL of the lamp voltage detection circuit 7;

A DC voltage detection circuit connected to VL2, consisting of a differential amplifier and a rectifier, and a voltage detection terminal VL.

The potential difference between VL and VL is detected, and a voltage corresponding to the high frequency resonant voltage detected by the lamp voltage detection circuit 7 is outputted to the output terminal.

14 is a lamp lighting detection circuit, and the voltage generated at the capacitor COO at the output terminal of the DC voltage detection circuit 13 is detected at the input terminal.
It consists of a comparator COMP to which C1o is input and a reference voltage obtained from a resistor R21°R22 is input to the negative input terminal, and an inverter INI which inverts the output of this comparator COMP. The inverter circuit 2 in Fig. 1 oscillates at a low frequency, a high frequency resonance voltage is superimposed on the low frequency voltage generated at this time, and this voltage vC detected by the DC voltage detection circuit 13
10 becomes higher than the reference voltage of the lamp lighting detection circuit 14, the output of the comparator COMP becomes high level,
Therefore, the output of inverter INI becomes low level. Next, the oscillation frequency of the inverter circuit 2 changes and a high resonant voltage is generated, and when the discharge lamp 5 is started, the detection voltage of the lamp voltage detection circuit 6 decreases as described above, and the output of the comparator COMP is at a low level, and the inverter The output of INI becomes level 1.

15 is a sawtooth wave generation circuit, the output voltage of which is connected to a resistor R29.
, is added to the bias voltage of the first bias circuit 16 consisting of the variable resistor R24 via the resistors R26 and R26, respectively, and is added to the bias voltage of the first constant current circuit 1 through the first cutoff circuit 17.
It is input to the input terminal of the operational amplifier OP2 of No. 8. This sawtooth wave generation circuit 15 may be a triangular wave generation circuit.

The first cutoff circuit 17 consists of a transistor QI+ interposed between the input terminal of the operational amplifier OP2 of the first constant current circuit 18 and the ground, and its gate has the output terminal of the inverter INI of the lamp lighting detection circuit 14. When the output of the inverter INI is at high level, the transistor Q,1
is turned ON, and the output of the sawtooth wave generating circuit 15 is cut off. The first constant current circuit 18 is a resistor R28 connected to the RT terminal of the switching regulator control IC 19.
, a transistor Q12 and a resistor R connected in parallel to a bias current circuit 20 consisting of a series circuit of a variable resistor R29.
The gate of the transistor Q1□ is connected to the output terminal of the operational amplifier OP2, and the connection point between the transistor Q12 and the resistor Rho is connected to the operational amplifier OP2.
Connected to one input terminal of 2.

Therefore, when the DC power is turned on and the output of the inverter INI of the lamp lighting detection circuit 14 is at a high level, the first cutoff circuit 17 operates to cut off the output of the sawtooth wave generation circuit 15. The transistor Q 12 of the first constant current circuit 18 is 0FFL, and the current flowing through the R terminal of the switching regulator control IC 19 is only the current ia flowing to the bias current circuit 20, and this current ia and the switching regulator control I
It is determined by the capacitor CI2 connected to the zero terminal of C19.

For example, 2K)l! Clocks E, . . . E2 having relatively low frequencies and having mutually inverted phases are outputted from the switching regulator control IC 19 and applied to the drive circuit 12 in FIG. A high frequency resonant voltage is superimposed on the low frequency voltage generated at this time by the resonant circuit of the choke coil 3 and the capacitor 4, and this voltage is detected by the voltage detection capacitor C9.
When the output voltage vclo of the lamp lighting detection circuit 14 becomes higher than the reference voltage of the lamp lighting detection circuit 14, the output of the lamp lighting detection circuit 14 becomes low level, and the transistor Q of the first cutoff circuit 17
, r are turned off, and the output of the sawtooth wave generation circuit 15 is input to the operational amplifier OP2 of the first constant current circuit 18.
Transistor Q1□ conducts and sucks current from the RT terminal of switching regulator control IC19.
The sinking current ib is increased until the voltage generated across the resistor R30 becomes equal to the input sawtooth wave voltage to achieve balance. As a result, a current of ia+ib flows through the R terminal, increasing the frequency of the clocks E, . At this time, since the sawtooth wave generating means 15 changes the oscillation frequency of the inverter circuit within a predetermined range of frequencies including the resonance frequency determined by the choke coil and the resonance capacitor, the inductance of the choke coil and the capacitance of the resonance capacitor may vary or shift. Even if the sawtooth wave voltage generated from the sawtooth wave generation circuit 15 generates a resonant voltage, the resonant voltage is generated for a short time, so that a large current does not continue to flow for a long time. It is possible to improve the reliability of components and prevent a drop in the output voltage of the DC power supply.

21 is a lamp current calculation circuit connected to the output terminal of the DC voltage detection circuit 13. 22 is a resistor R11, a variable resistor R
A bias circuit consisting of 32 generates a bias voltage that serves as a reference for the rated current. 23 is a DC current detection circuit connected to the current detection terminal IDC of the lamp current detection circuit 7. These output voltages are connected to resistors R33 and R341, respectively.
It is added via R35, and the operational amplifier O of the comparator circuit 24
P3 is input to one input terminal of lamp current calculation circuit 21. The reference voltage is the summed output voltage of the lamp current calculation circuit 21 and the first bias circuit 22 such that the sum of the first bias circuit 22 and the DC current detection circuit 23 becomes 0, and the DC current detection circuit 23 Control is performed such that the negative output voltage of is equal to this reference voltage. The output of this comparison circuit 24 is inputted through a second cutoff circuit 25 to an input terminal of an operational amplifier OP4 of a second constant current circuit 26. The second cutoff circuit 25 consists of a transistor Q13 interposed between the input terminal of the operational amplifier OP4 of the first constant current circuit 26 and the ground, and the output terminal of the inverter INI of the lamp lighting detection circuit 14 is connected to the inverter IN.
2 to the gate of transistor Q+3,
When the output of inverter INI is low level, transistor Q
+3 is turned ON, and the output of the comparator circuit 24 is cut off. Further, the second constant current circuit 26 includes a transistor Q14 connected in parallel to the bias current circuit 2G connected to the RT terminal of the switching regulator control IC 19;
It has a series circuit of a resistor R37, the gate of the transistor Q14 is connected to the output terminal of the operational amplifier OP4, and the connection point between the transistor Q14 and the resistor R37 is connected to one input terminal of the operational amplifier OP4.

The lamp current calculation circuit 21 has, for example, a circuit configuration as shown in FIG. 1o is added to the bias voltage obtained from resistor R41 and variable resistor R42,
It is inverted and amplified by operational amplifier OP5.

As a result, the voltage VC generated in the capacitor C11 at the output end of the lamp current calculation circuit 21 and the output voltage vC1o of the DC voltage detection circuit 13 have the characteristics shown in FIG. be done. In Figure 6,
Below the predetermined lamp voltage, that is, the DC voltage detection circuit 13
A predetermined output voltage V. Operational amplifier OP5 below 10'
The output voltage V Cl + of the lamp current calculation circuit 21 is clipped to be constant due to the saturation voltage of , and the oscillation frequency of the switching regulator control IC+9 is limited to be constant below a predetermined lamp voltage V CI O. This prevents excessive current from flowing into the discharge lamp and damaging it. Furthermore, a predetermined output voltage V. ,. ’ or more and less than V CI O’, as the lamp voltage increases, V
CI 1 decreases and becomes 0 above V CI O', and the reference voltage of the comparison circuit 24 becomes only the bias voltage of the first bias circuit 22. In addition, lamp current calculation circuit 2
Instead of using the saturation voltage of the operational amplifier OP5 to clip the high portion of the output voltage VC11, a Zener diode may be connected to the output terminal to perform the clipping. Further, a circuit may be added to provide a lower limit value so that the output voltage of the DC voltage detection circuit 13 does not fall below a predetermined voltage.

As mentioned above, when the frequency of the clocks E, E2 is increased to generate a high resonant voltage of the resonant circuit and the discharge lamp 5 is started, the output voltage of the DC voltage detection circuit 13 is increased. , 0 decreases, and the output voltage VC, , of the lamp current calculation circuit 21 increases and is started. At this time, the reference voltage, which is the added output voltage of the lamp current reference circuit 21 and the first bias circuit 22, increases, the difference with the output voltage of the DC current detection circuit 23 increases, and the output of the comparison circuit 24 becomes negative. Become. At the same time, the output of the lamp lighting detection circuit 14 becomes high level, so that the transistor Q 1 of the first cutoff circuit 17
1 turns on to cut off the output of the sawtooth wave generation circuit 15, turns off the transistor Q1□ of the first constant current circuit 18 to stop the current sucking operation, and turns on the transistor Q of the second cutoff circuit 25. 13 is turned off, the negative output of the operational amplifier OP3 of the comparison circuit 24 is input to the operational amplifier OP4 of the second constant current circuit 26, and the output of this operational amplifier OP4 turns off the transistor Q14.
Therefore, the frequency of the clocks El and E2 of the switching regulator control IC 19 remains the same as the original 2 KH! The frequency will be approximately. Therefore, the lamp current increases and the output voltage of the DC current detection circuit 23 increases.
At the same time, the output voltage VCIO of the DC voltage detection circuit increases, and as a result, the output voltage vC11 of the lamp current calculation circuit 21 increases.
decreases, and as a result, the operational amplifier OP of the comparator circuit 24
3 changes from negative to 0 and then to positive, and at this point the transistor of the second constant power supply circuit 26 becomes conductive and sucks current from the R terminal of the switching regulator control IC 19, and the clock E of the switching regulator control IC 19 , enhances the oscillation of E2. Therefore, the output voltage v of the DC voltage detection circuit 13 of the lamp voltage
As c1o increases, the output voltage V of the lamp current calculation circuit 2I
C,, decreases L7, and at the same time, the output voltage of the DC current detection circuit 23 of the lamp current decreases, increasing the sink current by the transistor Q14 of the second constant current circuit 26, and further inputting it to the input terminal of the operational amplifier OP4. The oscillation frequency of the clocks E, . This control is repeated until the output voltage VC,, of the lamp current calculation circuit 21 becomes 0, and finally, when the output voltage of the DC current detection circuit 23 becomes equal to the output voltage of the second bias circuit 22, The clocks El and E2 oscillate at an oscillation frequency of, for example, around 10KH2, which is determined by the sum ia+ic of the sink current ic of the transistor Q14 of the second constant current circuit 26 and the sink current ia of the bias current circuit 20 at this time. The lamp lights at the rated lamp power during stable lighting.

FIG. 7 shows a lamp voltage (V)-lamp current (I) characteristic diagram. In Fig. 7, a large lamp current is passed when the lamp voltage is below a predetermined lamp voltage V', which is the starting region of the lamp, and a large DC current is passed, and a constant current is passed when the lamp is above a predetermined lamp voltage V', which is the stable lighting region of the lamp. It is controlled to flow. Therefore, the lamp current can be reliably controlled, a large lamp current can be passed at the time of starting, and the lamp can be quickly and stably lit. During stable lighting, the lamp power can be kept almost constant, and the lamp can be lit at the rated lamp power.

In this way, in the above process, the lighting control circuit 8 receives the voltage detected by the lamp voltage detection circuit 6, and when the lamp voltage is low, lowers the frequency of the clocks E, E2 to flow a large lamp current, thereby increasing the lamp voltage. When is high, clock E
, , control is performed such that the frequency of E2 is increased to cause a small lamp current to flow.

27 is a starting voltage timer circuit connected to the output terminal of the lamp lighting detection circuit 14. When the DC power is turned on, the inverter circuit oscillates at a low frequency, and a high frequency resonant voltage is superimposed on the low frequency voltage generated at this time. This resonant voltage is detected by the DC voltage detection circuit 13, and when this detected voltage V CI O becomes higher than the reference voltage of the lamp lighting detection circuit 14, the output of the inverter INI becomes O- level and starting starts. At this time, the starting voltage timer circuit 27 operates at the low level of the inverter INI, and if the inverter INI does not become high level within a predetermined period of time, for example, 1 second, that is, the discharge lamp is started and remains ON within the predetermined period of time. If the starting does not start, the switching regulator control ICl9 stops the oscillation of the inverter circuit, prevents high voltage from being generated for a long time and being applied to the discharge lamp, and prevents damage to the discharge lamp to ensure safety. do.

28 is a starting current timer circuit connected to the output terminal of the lamp current calculation circuit 21, which detects that the lamp current is larger than a predetermined value, that is, the lamp voltage is smaller than the predetermined value (therefore, the lamp current calculation circuit It operates upon detecting that the output voltage V Cl + of the circuit 21 is higher than a predetermined value, and if the output voltage VC,, does not become smaller than the predetermined value within a predetermined time, that is, within 20 seconds, the switching regulator control ICl9 operates. This stops the oscillation of the inverter circuit, prevents the starting current from flowing into the discharge lamp for a long period of time, and prevents damage to the discharge lamp.The starting current timer circuit 28 is operated by the output voltage vc1o of the DC voltage detection circuit 13. In this case, the oscillation of the inverter circuit is stopped when the voltage V CI O does not exceed a predetermined value within a predetermined time.

FIG. 8 is a circuit diagram showing another example of the first cutoff circuit and the first bias circuit, which are used to gradually change the frequency when the discharge lamp transitions from startup to lighting. In FIG. 8, the cutoff circuit 31 is a transistor Q
2+1Q2□, and the gates of the transistors Q21102□ are connected to the output end of the lamp lighting detection circuit 14 via resistors R, , R, 2, respectively. The bias circuit 324 includes a series circuit for bias consisting of a resistor R53 and a variable resistor R54, a series circuit consisting of a resistor R67 and a capacitor C20 connected to the bias point of this bias series circuit, and a series circuit interposed between both ends of the resistor R57. It consists of a diode D for charging the capacitor 2G, and the connection point between the resistor R57 and the capacitor 20 is connected to the first constant current circuit 1 via the resistor R66.
A roughly sawtooth wave generating circuit 1 is connected to the ten input terminal of the operational amplifier OP2 of No.8.
The output voltage of 5 is added and inputted via the resistor R6, and the transistor Q21 of the cutoff circuit 31 is connected between the output terminal of the sawtooth wave generating circuit 15 and the ground, and the transistor Q2
is interposed between the bias point of the bias series circuit and ground.

Now, the output of the lamp lighting detection circuit 14 is at a low level, and the transistors Q2□ and Q2□ of the cutoff circuit 31 are turned off.
When F is applied and startup begins, the bias series circuit R, 3,
The bias voltage of R, 4 is added to the output voltage of the sawtooth wave generation circuit 15 and is applied to the operational amplifier OP of the first constant current circuit 18.
It is input to the ten input terminal of 2. At this time, the bias voltage is almost instantaneously applied to the input terminal of the operational amplifier OP2 of the first constant current circuit 18 via the diode DI+, and a charge is stored in the capacitor C20. Next, when the frequency increases and the lamp current flows due to the high resonant voltage, and starting starts, the output of the lamp lighting detection circuit 14 becomes high level, and the transistors Q2 + IQ2 of the cutoff circuit 31
□ is turned on. At this time, the bias voltage of the bias circuit 32 is not grounded immediately, but the charged voltage of the capacitor 20 is discharged through the resistors R, 7, R66, R6, so the bias voltage gradually decreases, and the bias voltage is gradually lowered.
,, E2 is 2 KH at once! This avoids lowering the frequency to a lower level. In this way, when transitioning from startup to lighting, the frequency of the clock El+E2 is gradually lowered, making it possible to avoid stopping the startup due to a sudden drop in the resonance voltage.

FIG. 9 is a circuit diagram showing a configuration example of a series inverter circuit. In FIG. 9, both ends of the primary winding of drive transformer DT' are connected to drive transistor Q 311 Q
32, and transistors Q3□, Q3
2 gates are clocks E whose phases are inverted to each other,
, E2 are input, and a drive voltage VD is applied to the midpoint of the negative winding. Two secondary windings are provided on the secondary side of the drive transformer DT', and one end of each is connected to the gate of the switching transistor Q33°Q34 via a resistor R71°R7□. The switching transistors Q 331 034 are connected in series and interposed between the DC power supply voltage VDD and the ground to constitute a series inverter, and the other end of each of the secondary windings of the drive transformer DT' is connected to the switching transistor Q 33 .
and Q34 connection point and ground. In addition, a capacitor C30% choke coil 3 for current reversal,
The series circuit of the resonant capacitor 4 and the voltage detection capacitor C31 is connected between the connection point of the switching transistor Q331034 and the ground, and the series circuit of the discharge lamp 5 and the resistor R73 is connected to the connection point of the choke coil 3 and the capacitor 4. connected between ground. Here, the capacitance of the capacitor C30 is configured to be larger than that of the capacitor 4. VL is a lamp voltage detection terminal, and IP is a lamp instantaneous current detection terminal.

In the above configuration, the switching transistor Q 33
When is ON, switching transistor Q34 is 0
FFL, a current from the DC power supply flows in the (c) direction to the resonant circuit via the capacitor C30, and the switching transistor Q1. When Q is OFF, the switching transistor Q
34 is turned on, the charge stored in the capacitor C1° flows into the resonant circuit in the (d) direction, and the operation thereafter is similar to that shown in FIG. 3, and the discharge lamp 5 is lit. At this time, the lamp voltage is detected from the lamp voltage detection terminal VL, and there is no need to detect it from the potential difference across the voltage detection capacitor C31, so the DC voltage detection circuit does not require a differential amplifier as shown in Figure 4. No, just a rectifier is sufficient.

In the above embodiments, the lamp current was controlled by frequency, but it goes without saying that it may also be controlled by duty ratio. Furthermore, although a bridge inverter is used as an example of the inverter, other inverters such as a sleeve inverter, a half-bridge inverter, a push-pull inverter, and a single-stone inverter may be used. It goes without saying that the DC power supply also includes a rectified AC power supply.

Effects of the Invention According to the present invention, by using a resonant circuit, a high voltage can be generated in the resonant capacitor, and thereby the discharge lamp can be reliably started. This can be achieved with Moreover, when the DC power is turned on, even if the inverter means oscillates at a low frequency, the resulting voltage, in which the high frequency resonant voltage is superimposed on the low frequency voltage, is detected and the inverter means is oscillated at a high frequency. By causing the resonant capacitor to oscillate, the resonant capacitor can be changed to generate a high resonant voltage, allowing a smooth transition from power-on to lamp startup.

Furthermore, if the oscillation frequency of the inverter is changed after startup according to the output voltage of the sawtooth wave generating means or the triangular wave generating means, even if the inductance of the choke coil or the capacitance of the resonant capacitor varies or shifts, It is possible to ensure that a resonant voltage is generated, and because the resonant voltage is generated for a short period of time, a large current does not flow for a long time.
It is possible to improve the reliability of components and prevent a drop in the output voltage of the DC power supply.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of a discharge lamp lighting device according to an embodiment of the present invention, and FIGS. 2(a) and 2(b) each show an example of the configuration of a choke coil used in the same discharge lamp lighting device. 3 is a circuit diagram showing the main parts of the inverter circuit in the same discharge lamp lighting device, FIG. 4 is a circuit diagram showing a configuration example of the lighting control circuit in the same discharge lamp lighting device, and FIG. 5 is the same lighting device. A circuit diagram showing a specific configuration example of the lamp current calculation circuit in the control circuit, FIG. 6 is a characteristic diagram of the lamp current calculation circuit, FIG. 7 is a lamp voltage-lamp current characteristic diagram of the lighting control circuit, and FIG. FIG. 9 is a circuit diagram showing another example of the cutoff circuit and bias circuit for the sawtooth wave generating circuit in the same lighting control circuit, and FIG. 9 is a circuit diagram showing an example of the configuration of the series inverter circuit in the same discharge lamp lighting device. 1... DC power supply, 2... Inverter circuit, 3...
Choke coil, 4... Resonance capacitor, 5... Discharge lamp, 6... Lamp voltage detection circuit, 7... Lamp current detection circuit, 8... Lighting control circuit, 11... External circuit, 12... Drive circuit, 13... DC voltage detection circuit, 14... Lamp lighting detection circuit, 15...
sawtooth wave generation circuit, 16...first bias circuit, 1
7... First cutoff circuit, 18... First constant current circuit, 19... Switching regulator control I
C, 20...Bias current circuit, 21...Lamp current calculation circuit, 22...Second bias circuit, 23...
・DC current detection circuit, 24... Comparison circuit, 25...
Second interrupting circuit, 26... Second constant current circuit, 27.
... Starting voltage timer circuit, 28... Starting current timer circuit, 31... Cutoff circuit, 32... Bias circuit. Fig. 1 Tourer electric; block 1 phantom (Fig. 2, 4) (To 1 π toss 5 Sugi muff t2 ---)' Live circuit Fig. 3 Fig. 5 Fig. 6 Fig. 7 Foil h

Claims (1)

[Claims] 1. A DC power supply, an inverter means that is driven by the DC power supply to oscillate, a resonant circuit consisting of a series circuit of a choke coil and a capacitor connected to the inverter means, and the choke coil and the capacitor. a discharge lamp connected to a connection point of the discharge lamp, a lamp characteristic detecting means for detecting at least one of a lamp voltage and a lamp current, and an oscillation frequency or duty ratio of the inverter means being varied by an output signal of the lamp characteristic detecting means. A discharge lamp lighting device comprising: lighting control means for controlling lighting of the discharge lamp. 2. The resonant circuit consists of a series circuit of a first capacitor, a choke coil, and a second capacitor, the discharge lamp is connected to the connection point of the choke coil and the second capacitor, and the capacitance of the first capacitor is The discharge lamp lighting device according to claim 1, wherein the capacity of the second capacitor is larger than that of the second capacitor. 3. The inverter means oscillates at a low frequency when the DC power is turned on, the lamp voltage detection means detects a voltage in which a high frequency resonant voltage is superimposed on the low frequency voltage generated at this time, and the lighting control means oscillates at a low frequency when the DC power is turned on. 3. The discharge lamp lighting device according to claim 1, wherein the oscillation frequency of the inverter means is changed to a higher frequency by the signal detected by the inverter means, thereby generating a high resonant voltage in the resonant circuit. 4. The discharge lamp lighting device according to claim 3, wherein the lighting control means includes means for gradually changing and lowering the oscillation frequency of the inverter means when the discharge lamp is started by a high resonant voltage generated in the resonant circuit. 5. The lighting control means has a sawtooth wave generation means or a triangular wave generation means, and when changing the oscillation frequency of the inverter means to a high frequency, the oscillation frequency is adjusted according to the output voltage of the sawtooth wave generation means or the triangular wave generation means. 4. The discharge lamp lighting device according to claim 3, wherein the discharge lamp lighting device is configured to vary within a predetermined range. 6. The lighting control means has a starting voltage timer means which operates when the inverter means oscillates at a high oscillation frequency and stops the oscillation of the inverter means when the oscillation frequency of the inverter means does not decrease within a predetermined time. The discharge lamp lighting device described. 7. The discharge lamp lighting device according to claim 1 or 2, wherein the choke coil has a center gap between the central legs of a pair of opposing cores. 8. The discharge lamp lighting device according to claim 1 or 2, wherein the choke coil has a space gap between the center leg and both end legs of the pair of opposing cores.