JPH0261997A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To reduce the macroscopic change quantity of the lamp current and prevent the flickering of a discharge lamp and the quick change of the light output by providing the rest period of the lamp current when the discharge lamp is started. CONSTITUTION:When the light output of a discharge lamp 2 is to be increased, it is increased by a dimming control means 4 via a dimming signal II. The lamp current has a rest interval at this time. After the light output is increased by the dimming control means 4, the reset period of the lamp current is narrowed by a dimming control means 3 via a dimming signal I until the rated lighting is obtained. In this case, the start of the discharge lamp 2 and the transition to the lighting mode by the luminescent spot generation are completely performed before the dimming control by the control means 3 is performed. The lighting mode using the start of the discharge lamp 2 and the luminescent spot generation is changed to the lighting mode not using the luminescent spot generation at the time of dimming by the means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at high frequency using an inverter device.

[Prior Art] Conventionally, discharge lamp lighting devices that use an inverter device to light fluorescent lamps at high frequencies have been widely used.

Furthermore, electronic ballasts with a dimming function are known that vary the output of an inverter device to dimly light a fluorescent lamp.

Furthermore, in order to enable dimming control to a deeper dimming level, a method of dimming is performed by applying a starting pulse voltage intermittently and making the voltage between these starting pulse voltages variable. has also been proposed.

[Problem M to be solved by the invention] However, when a discharge lamp is dimmed using the electronic stabilizer 25 with a dimming function as described above, at a shallow dimming level (relatively bright dimming level), There is a problem in that the discharge lamp flickers and the light output suddenly changes, and the light output sometimes suddenly changes even when the discharge lamp is started.

First, the causes of flickering and sudden changes in light output of discharge lamps at shallow dimming levels will be explained. When a hot cathode discharge lamp such as a fluorescent lamp is lit using a general ballast, the filament is preheated and the electrons that form the lamp current collide with the filament, heating it and causing the filament to heat up. A bright spot) is generated, and the main electrons are emitted from this bright spot. On the other hand, dimming ballasts exhibit the same behavior as -m ballasts at rated lighting, but when dimmed to a deep level, the collisions between the electrons and filament described above decrease, and the filament As the temperature decreases, bright spots are less likely to be generated. For this reason, when a fluorescent lamp is continuously dimmed from its rated lighting state to a deeper level, there is a dimming level in the process that transitions from a mode with bright spots to a mode with no bright spots. That will happen. As a result, the light output of the discharge lamp suddenly changes before and after the dimming level, or
It is thought that in this transient state, the lighting mode becomes unstable, causing the discharge lamp to flicker.

Next, a sudden change in light output at the time of starting the discharge lamp will be explained. For the purpose of explanation, a discharge lamp can be considered as an ideal impedance component, that is, if the lamp voltage is lower than the discharge starting voltage, the resistance is infinite, and if it is above the discharge starting voltage, it is a component with a finite resistance value as a conductor. , and the impedance component of an actual discharge lamp.

In FIG. 7, the discharge lamp 1a is started by increasing the lamp voltage V1a to a discharge starting voltage or higher, but when increasing the lamp voltage V1a, an ideal impedance component Z is generated when the discharge is not started. .

is infinite, and its current Izo is zero. On the other hand, since the impedance component Zl of an actual discharge lamp is finite, a current Iz of la/Z1 flows. Then, the lamp voltage Vfa is further boosted, and the lamp voltage V1
At the moment a reaches the discharge starting voltage, the impedance component Z
0 is a finite resistance value Z. 1. For this reason,
Until now, I z, = O was V j! a /
An additional current Z o+ begins to flow, and as a result, the light output of the discharge lamp increases rapidly.

Here, impedance components 2, . 2. Even when a current limiting element such as an inductor is used to suppress a steep current change in the current ■ flowing in , the current Iz, which previously flowed only in the impedance component z1, is also shunted to the impedance component Z0. As a result, the light output of the discharge lamp increases rapidly.

The principle of sudden changes in light output when starting a discharge lamp has been briefly explained above, but in a ballast in which an impedance element is connected in parallel with the discharge lamp, the impedance element is connected in parallel to the impedance component Z1 mentioned above. Therefore, the sudden change in light output becomes more severe.

The present invention has been made in view of these points, and its purpose is to provide a discharge lamp that does not flicker or suddenly change its light output even when the light is dimmed from the rated lighting state to a deep level. An object of the present invention is to provide a discharge lamp lighting device that can perform stable starting and dimming lighting.

[Means for Solving the Problems] In order to solve the above problems, in the discharge lamp lighting device according to the present invention, as shown in FIG. A discharge lamp 2 serving as a load, a first dimming control means 3 that controls the load current rest period of the high frequency generation circuit 1, and a second dimming control means 4 that performs load power control other than load current rest period control. It is characterized by comprising the following.

Here, at the time of starting the discharge lamp 2 and at a dimming level at which no bright spot is generated on the filament, dimming control is performed so that there is always a load current rest period. Therefore, when reducing the light output of the discharge lamp 2, the first
After the dimming control means 3 lengthens the load current pause period and dims the light, the second dimming control means 4 further dims the light.On the other hand, when increasing the light output, the second dimming control means 4 increases the light output. After the light control means 4 increases the brightness, the first dimming control means 3 shortens the load current pause period to further increase the brightness.

Note that the dimming control section by the second dimming control means 4 is 4.
The total time T of this dimming control section t and the lamp current stop period by the first dimming control means 3 is set to be larger than 0 μsec, and the lamp current stop period is set to the maximum. It is preferable to set the value of /T, that is, the minimum value of LET, to 115 or less.

[Function] According to the present invention, as described above, when the discharge lamp 2 does not start and when no bright spot is generated on the filament,
Since it is assumed that a lamp current stop period always exists, the amount of change in lamp current becomes small when viewed macroscopically, and flickering of the discharge lamp and sudden changes in light output can be prevented.

In addition, compared to dimming control that only uses lamp current pause interval control, the degree of freedom in dimming control is greater.
When the light output of the discharge lamp is low, the lamp current pause interval can be set so that flickering and sudden changes in light output are least likely to occur. In particular, by appropriately setting the operating range of the first dimming control means and the second dimming control means, it is possible to reduce the flickering of the discharge lamp and sudden changes in light output to a level that is not noticeable to the human eye. It is what it is.

[Embodiment 1] FIG. 1 is a block circuit diagram of the most basic embodiment of the present invention. In this discharge lamp lighting device, when increasing the light output of the discharge lamp 2, first, the second
It is assumed that the brightness is increased by the dimming control means 4. At this time, it is assumed that there is a pause section in the lamp current 112a.

After the second dimming control means 4 increases the brightness, the first dimming control means 3 narrows the pause period of the lamp current and increases the brightness to reach the rated lighting according to the dimming signal I. However, it is assumed that before shifting to dimming control by the first dimming control means 3, the starting of the discharge lamp 2 and the transition to the lighting mode by bright spot generation are completely performed.

In addition, when dimming the discharge lamp 2, it is assumed that the dimming is performed by a process completely opposite to the process of increasing the luminosity.

By controlling in this way, the discharge lamp 2 can be started,
The transition between the lighting mode based on bright spot generation and the lighting mode not based on bright spot generation is performed during dimming by the second dimming control means 4. In that case, since there is a lamp current pause period, the amount of change in the lamp current from a macroscopic perspective is smaller compared to the conventional dimming control method in which there is no lamp current pause period, and the flickering of the discharge lamp 2 and the light This makes it possible to avoid sudden changes in output.

[Embodiment 2] FIG. 2 is a block diagram of an embodiment of a pond of the present invention. In this embodiment, a low luminous flux stable lighting means 5 is provided so that the light can be stably adjusted to a deeper level.

The specific circuit configuration is shown in FIG. 3. FIG. 3(a) shows the configuration of the main circuit, and FIG. 3(b) shows the configuration of the control circuit.

First, the configuration of the main circuit will be explained. Commercial AC power supply A
A capacitor C3 is connected to C through a diode D that conducts during the positive half cycle, and a capacitor C1 is connected to C through a diode D2 that conducts during the negative half cycle.
is connected. Each capacitor C, C4 has a resistor R
,,R, are connected in parallel. Capacitor C
3 and C4 are connected in series, and between the positive terminal of the capacitor C1 and the negative terminal of the capacitor C4, a high DC voltage obtained by voltage double rectification and smoothing of the commercial AC power supply AC is obtained.

In addition, commercial AC power supply AC and diode D1. D2
The filter circuit inserted between the capacitor CC2, the lance T1, and the nonlinear resistance element ZNR prevents high frequency noise from leaking into the power supply line. Further, the fuse F is for overcurrent prevention.

The positive terminal of the capacitor C1 is connected to a switching element Q1 made of a power MO3FIET and a current-limiting inductor l.
It is connected to the positive terminal of the smoothing capacitor C5 through the . The negative terminal of the capacitor C7 is connected to the negative terminal of the capacitor C1, and a diode D for conducting flywheel current.

The switching element Q is connected between the anode and cathode of
1 and the inductor L1. A resistor R3 is connected in parallel to both ends of the capacitor C3. When switching element Q1 is turned on, capacitor C,...
Current flows from C to capacitor C5 via switching element Q and inductor L1, and electromagnetic energy is accumulated in inductor L. When switching element Q is turned off, the electromagnetic energy of inductor L1 is released through diode D to capacitor C6. This constitutes a well-known step-down chopper circuit.

The DC voltage charged to this capacitor C9 is lower than the voltage obtained in the series circuit of capacitors C) and C4.

The DC voltage obtained across the capacitor C9 is passed through a reverse current blocking diode D4 to a switching element Q3. Q, is applied to the series circuit. A parallel circuit of the discharge lamp 1a and a resonance capacitor C7 is connected to both ends of one switching element Q4 via a DC coupling capacitor C6 and an inductor L2. Switching elements Q, , Q are alternately turned on and off, thereby generating a rectangular wave voltage across switching element Q. This rectangular voltage is passed through a coupling capacitor C6 for cutting the DC component,
An AC voltage is applied to the ■-〇 series resonant circuit consisting of an inductor L2 and a resonant capacitor C1, and the capacitor C
The discharge lamp ja is started and lit by the high voltage generated at both ends of the lamp 7 by the resonance effect.

On the other hand, the high DC voltage obtained in the series circuit of capacitors C, , C, is applied to the switching element Q2. Q, is applied to the series circuit. As described above, a load circuit including an LC resonant circuit is connected to both ends of the switching element Q through the coupling capacitor C6. Therefore, the switching elements Q, ,Q
, the switching element Q2. A circuit including a series circuit of Q constitutes a second high frequency generation circuit, and both of them share a switching element Q4, a coupling capacitor C6, and a load circuit. Including the generation circuit, the high frequency generation circuit 1 shown in FIG. 2 is configured. Here, the high frequency generation circuit made up of switching elements Q, , Q constitutes an inverter for starting and maintaining lighting, and the high frequency generation circuit made up of switching elements Q, , Q4 constitutes a dimming inverter. The former is
Diodes D, ,D, ,resistors R, ,R2, capacitors C
Power is supplied from a voltage doubler rectifier and smoothing circuit consisting of y, C<, and its power supply voltage is approximately 282V. The latter uses the output of the voltage doubler rectifying and smoothing circuit as a power source, and the output voltage of a step-down chopper circuit composed of a switching element Q1, a diode D3, an inductor L1, a capacitor C9, and a resistor R1.

Regarding the resonance system including inductor L2 and capacitor C7, when starting at the lowest dimming level, that is, after the inverter for starting and maintaining lighting has operated for four cycles, and with the inverter for dimming operating for four cycles, the discharge lamp 1a starts and 0
．． The lamp is designed so that the dimming level is less than 5%, and the lamp current flows above the rated current when the lamp is fully lit, that is, when 282V is always being supplied.

Note that when the switching element Q2 is turned on, the diode D4 connects the capacitor C via an anti-parallel diode parasitic between the train and source of the switching element Q.
3, C, is provided to prevent current from flowing backward into the capacitor C5 of the step-down chopper circuit. An element equivalent to the diode D is not provided between the capacitor c3 and the switching element Q2, but this is because the voltage of the capacitors C, C, is higher than the voltage of the capacitor C1, so the switching element Q is Even if the switching element Q2 is turned on, the capacitor C5 is
This is because there is no risk of current flowing into C4.

Next, the control circuit section shown in FIG. 3(b) will be explained. The driving circuit for the switching element Q consists of a transformer T1, resistors R, , R, and a diode DIGD I+. The center tap of the primary winding of the +- lance TIO is connected to the $11 power supply, one end of the primary winding is grounded via the driving switching element QII, and the other end of the primary winding is connected to the diode. It is grounded via D1°.

One end of the secondary winding of the +- lance T10 is connected to the source of the switching element Q4, and the other end is connected to the forward bias resistor Rl? and is connected to the gate of the switching element Q4 via a reverse bias diode D11. A resistor RIM is connected between the gate and source of the switching element Q4.
are connected in parallel.

Now, when the driving switching element Q is turned on and one end of the primary winding of the transformer T1 is grounded, the transformer T
91I applied to the center tap of the primary winding of 1°
Current flows through the primary winding due to the power supply, and the transformer T 1 o
Current flows through the series circuit of resistors R+t and RIH connected to the secondary winding of Q, and the voltage generated across resistor RII forward biases the gate and source of switching element Q. , is turned on. Next, when the driving switching element Q11 is turned off and the current flowing to the primary winding of the transformer TIO is cut off, the diode DIO is turned on to continue flowing this current.
A regenerative current flows to the control power supply through the At this time, transformer T. A back electromotive force is generated in the secondary winding of , and the current flowing through the diode D to the resistor R11+ causes the resistor R
A voltage that reverse biases the gate and source of the switching element Q is generated across the switching element 18, the N product charge of the gate-source capacitance is rapidly discharged, and the switching element Q is quickly turned off.

Switching element Q2 consisting of a power MOSFET. Q
The drive circuits of , have similar configurations, and perform similar operations.

In other words, the transformer Tl+, the resistors R,..., R2°, and the diode D constitute the drive circuit of the switching element Q.
I2. D, 0, a transformer T12 and a resistor R2, which constitute a drive circuit for the switching element Q2.

R22 and diode DI4. DI5 is a transformer Tl that constitutes the drive circuit of the switching element Q4 described above.
.

and resistors R,,,R,, and diodes D,. , Dll, respectively. Therefore, redundant explanations regarding these will be omitted.

Although a fit control source is not particularly shown, it can be obtained from a commercial AC power supply using a step-down transformer, a full-wave rectifier, and a smoothing capacitor. In addition, if the ground line is made to match the source of switching element Q1, the driving circuit of switching element Q can be connected to the transformer 'T'' to
~Can be constructed without using insulating elements such as TI2. However, in this embodiment, the reason why the switching element Q1 is directly driven without using a transformer is to increase the variation range of the on-duty of the switching element Q, as will be described later.

The oscillation circuit C, oscillates a drive signal for the chopper switching element Q, and the oscillation circuit IC2 oscillates a drive signal for the inverter switching elements Q2 to Q4. Both of these oscillation circuits IC+ and IC2 are composed of sub-door ICs (μPC494C manufactured by NEC Corporation) for switching regulators. This control IC is
As is well known, the power terminal (pin 12) and the ground terminal (
7# pin) between $! I #When the power is applied and the capacitor is connected between the capacitor terminal (bin 5'#) and the ground terminal T-, and the resistor is connected between the resistor terminal (bin 6) and the ground terminal. It has a built-in oscillator that oscillates at a frequency that corresponds to a constant. Its first oscillation output is
The second oscillation output is obtained by alternately shorting and opening the first open collector terminal (bin 8) and the first oven emitter terminal (bin 9). This is obtained by alternating between a short-circuited state and an open state between the second oven collector end '7' (bin 11) and the second open emitter terminal (bin 10). Here, when the output control terminal (bin 13) is lowered to earth level, the thimble for one stone is
When the end operation is performed, the first oscillation output matches the second oscillation output, and when set to the level of the reference voltage Vref obtained at the output side tn terminal 3 reference voltage output terminal (bin 14), A push-pull operation for two stones is performed, and the first oscillation output and the second oscillation output take opposite states after a predetermined dead-off time. This dead-off time can be set by inputting the reference voltage Vrer or the level-graded voltage of the control source Vcc to the dead-off time control terminal (bin 4). Note that the non-inverting input terminals (bin 1, bin 16) and the inverting input terminals (pin 2,
Pin 15) is the input terminal of a comparator for pulse width control. When pulse width control is not performed, the former is pulled down to the ground level, and the second one is pulled up to the level of the control power supply VCC. It is something to keep. Further, the feedback terminal (bin 3) is a feedback input terminal for pulse width control, and is left open when not in use.

In this embodiment, the power supply terminal (12
Connect the ground terminal (bin 7) and non-inverting input terminals (bin 1, 16) to the ground line 17, and connect the inverting input terminal (bin 2) to the earth line via resistor R20. The output control terminal (bin 13) is connected to the reference voltage output terminal (bin 14) for push-pull operation. First and second oscillation outputs (No. 8 to 1
1 bottle) is not used. The oscillation period of the oscillation circuit C1 is determined by the time constants of the capacitor C1° connected to the capacitor terminal (pin No. 5) and the variable resistor VR connected to the resistor terminal (pin No. 6). capacitor C5
The voltage at .degree. repeatedly rises and falls depending on the oscillation period, but this voltage is applied to the non-inverting input terminal of the comparator CP. A reference voltage obtained by dividing the control power supply voltage by a variable resistor VR2 is applied to the inverting input terminal of the comparator CP+. The comparator CP1 is an oven collector output voltage comparator such as μPC272. In this embodiment, the output of the comparator CP1 is pulled up to the m control power supply voltage via the resistor R11, and the inverter G, It is inverted and waveform-shaped at ~G3 and applied to the gate of the switching element QIo made of MOSFET. The source of the switching element Q1° is connected to the ground line, and the drain is pulled up to the control power supply voltage via a resistor R1□. The voltage generated between the drain and source of this switching element Q1o is
It is applied between the gate and source of the switching element Q of the chopper circuit, and drives the switching element Q.

When the voltage of the capacitor C1° applied to the non-inverting input terminal of the comparator CP becomes higher than the reference voltage applied to the inverting input terminal, the output of the comparator CP+ becomes High" level, and the inverting circuit G, ~G3 The gate potential of the switching element Q10 becomes "Lo-" level through the switching element Q10, the switching element QIO turns off, and the gate-source voltage of the switching element Q1 becomes "H" level.
high” level, so the switching element Q is turned on. Also, when the voltage of the capacitor CIQ applied to the non-inverting input terminal of the comparator CP becomes lower than the reference voltage applied to the inverting input terminal, the comparator C.P.
1's output becomes °'Lou+'' level, and the inverting circuit G1
~G, the gate potential of the switching element Q to becomes "High" level, and the switching element Q
to is turned on, and the voltage between the gate and source of switching element Q becomes the "LoII+" level, so that switching element Q is turned off. Therefore, by manipulating the reference voltage applied to the inverting input terminal of the comparator CP with the variable resistor VR, the switching element Q
, and can control the output voltage of the step-down chopper circuit.

The on-duty of the switching element Q1 can be adjusted from 0 to 1009° by changing the voltage division ratio of the variable resistor VR2.
It can be made variable within the range of . Then, by changing the on-duty of the switching element Q1 in the range of 0 to 100%, the output voltage of the chopper circuit is changed from 0 to 100%.
It can be changed by 100%, that is, in the range of 0 to 282 cm.

As described above, since the variation width of the on-duty of switching element Q is large, it is difficult to drive switching element Q by a pulse transformer.In this embodiment, the drain of switching element QIO is connected directly to the gate of switching element Q. It is connected to perform direct f2% movement.

Next, in the oscillation circuit IC2, the output control terminal (pin 13)
is operated as the reference voltage level of the reference voltage output terminal (bin 14), and the oven emitter terminal (bin 9 and 10) is grounded, and each oven collector terminal (bin 111 and 8) is grounded. The oscillation outputs obtained are inverted and waveform-shaped by inverters G4 and Gs, respectively, to obtain first and second basic signals for driving the inverter. These first and second basic signals are
Each of the six logic circuits A N D + , A N D is used as one input signal of the AND circuits AND, AND2.
The outputs of 2 are connected to the gates of switching elements Q l l IQ l 2 each made of a MOSFET. These switching elements Q + +, Q
l2 is the switching element Q, ,Q
, the transformer T I O+ T l in each drive circuit of
1, respectively connected to one end of the switching element Q
,,Q,.

The capacitor terminal (5v bin) of this oscillation circuit IC is
It is commonly connected to the capacitor terminal (pin 5) of the oscillation circuit IC7, and performs master-slave operation.

Therefore, the oscillation frequency of the oscillation circuit IC2 is the oscillation frequency of the oscillation circuit I
It has the same frequency as C. The duty ratio of the oscillation output is determined by inputting the voltage obtained by dividing the reference voltage obtained at the reference voltage output terminal (bin 141) by variable resistor VR3 to the dead-off time control terminal (bin -1). Ru. Note that the inverting input terminals (bin 2, bin 15) are pulled up to the level of the control power supply Vcc via resistor R1, and the non-inverting input terminals (bin 1, bin 16)
number bottle) is pulled down to earth level.

Next, the control signal for the switching element Q2 is selected from among the first and second basic signals for driving the inverter, the inverter G,
The second basic signal obtained from the AND circuit A N D
This can be obtained by gating as necessary using s.

The gate signal of the AND circuit ANDA is generated by a color circuit IC.

This counter circuit IC is made up of, for example, a μPD4040, and receives a second basic signal for driving an inverter from one count to the next.
-I'm looking forward to it. Then, the output is logically operated by a logic circuit, and the output of the AND circuit AND is “Hi” for 8 cycles.
gh” level, and a “Low” level signal for 120 cycles is obtained, and the logical product circuit AND.

At the output, a signal of "High" level for 4 cycles and "Low" level for 124 cycles is obtained.

The output of the AND circuit AND is ANDed with the output of the NOT circuit G by the AND circuit AND, and the switching elements Q1. This is the gate signal for J. In this way, the inverter for starting and maintaining lighting can accurately count not only its oscillation circuit but also the rest period.
Completely synchronized with the inverter's operating frequency.

Next, the setting of the lamp current stop period, in other words, the setting of the inverter operating period, is the setting of the counter circuit IC. This is performed by the output of the timer circuit IC, which is triggered by a signal obtained by inverting the output of the precision circuit AND6 by the inverting circuit G1□. The output of this timer circuit IC is the logic circuit AND of the above-mentioned logic circuit.

It is connected to the other input of AND2, and only when the output of timer circuit IC4 is 'High' level.
The inverter becomes operational.

The timer circuit IC is a general-purpose timer IC (Signetics fiNE555).
C, as is well known, the trigger terminal (bin 2) is (1
/3) When the voltage drops below Vcc, it is triggered and the output terminal (3)
1 pin) becomes 'Ilight' level, and the discharge terminal ('
71 pin) becomes high impedance.

Also, the threshold terminal (bin 6) is (2/3)
When Vec is reached, the output terminal (bin 3) becomes ``Low'' level, and the discharge terminal (bin 7) also becomes ``Low'' level.

Is the power terminal (bin 8) ff1l fil? I: Source V
ce line, and the ground terminal (bin 1) is connected to the ground line. In addition, reset I ~ terminal (
The frequency control terminal (bin No. 4) is connected to the control power supply Vcc, and the frequency control terminal (bin No. 5) is connected to the decoupling capacitor C.
Connected to the ground line via. A voltage from a control power source Vcic is applied to a series circuit of a variable resistor R1 and a capacitor C1, which constitute a time constant circuit of the timer circuit IC. The connection point between the variable resistor VR1 and the capacitor C1 is the timer circuit 1B IC.

is connected to the threshold terminal (bin 6) and the discharge terminal (bin 7) of the timer circuit I.
C, operates as a monostable multivibrator.

This monostable multivibrator consists of a timer circuit IC,
When the input terminal (bin 2) becomes 'Loul' level and is triggered, the output terminal (bin 3) becomes "High".
level, the discharge terminal (bin 7) becomes a high impedance state, the capacitor C11 is charged via the variable resistor VR, and the charging voltage is set to the threshold terminal (bin 6).
When the threshold voltage (2/3) Vce of the bin 3 is reached, the output terminal (bin 3) and the discharge terminal (bin 7) become “
The time when the output terminal (bin 3) of the timer circuit IC, which is at the "Low" level and waits for the next trigger after the capacitor CI+ is discharged, is at the ")(i)Bh" level is determined by the variable resistor ■ It is determined by the time constant of R4 and the capacitor C11, and this time becomes the inverter operating period.The inverter operating period is variable from 8 cycles to 128 cycles depending on the rIA ratio of the trigger signal.

Next, the operation of this embodiment will be explained.

FIG. 4(a) shows the operating waveforms of each part during dimming operation by the second dimming control means (step-down chopper circuit), and FIG. The diagram shows the operating waveforms of each part during dimming operation using section control). Further, FIG. 4(b) and FIG. 5(b) show enlarged waveforms of the essential parts of FIG. 47(a) and FIG. 5(a), respectively.

In this example, as a countermeasure against flickering of the discharge lamp and sudden changes in light output during dimming, a high voltage application section, a dimming section, and an inverter pause section are provided, and the inverter pause section is compared with the former two sections. The output voltage of the step-down chopper circuit is made variable during the dimming period to produce a bright spot, and then the inverter is turned off by narrowing the inverter rest period. ing. Specifically, one section has a width of 128 periods, a high voltage application period of 4 periods, a dimming period variable from 4 periods to 124 periods, and an inverter pause variable from 120 periods to 0 periods corresponding to the dimming period. There are sections. At a deep dimming level, as shown in FIG. 4, the longest pause period is 120 periods, and four high voltage application periods and four dimming periods are provided. Dimming is performed by increasing the level of the applied voltage in this dimming section, and a transition is made to a lighting mode in which a bright spot is generated. Again, sudden changes in light output and flickering occur at the dimming level where the lighting mode changes, but since there is a 120-cycle inverter pause period,
For one section (128 cycles), the amount of lamp current change before and after the break is small, and sudden changes in light output and flickering are improved.

After that, as shown in Figure 5, the dimming period is changed from 4 cycles to 1 cycle.
In addition to extending the period to 24, the inverter rest period is increased to 120.
By narrowing the cycle to 0, the light is dimmed to a bright level and the light is switched to full lighting.

Further, the above operation also improves the sudden change in light output when starting the discharge lamp. First, the high voltage application period of 4 periods and 4
It is started according to the dimming period of the cycle.

In case 2, if the level of the applied voltage in the dimming section is set low by the step-down chopper circuit, no discharge path is formed and only both ends of the tube emit light. Next, when the level of the applied voltage in the dimming section is increased by the step-down absorber circuit, the discharge path is broken and the entire tube emits light. At this point, at the moment of break, there will be some fluctuation in the optical output, but since there is a 120-cycle inverter pause interval, one interval = 128 cycles).
The amount of change in lamp current before and after the break is small, and sudden changes in light output at startup are significantly improved.

[Embodiment 3] FIG. 6 is a block diagram of still another embodiment of the present invention. In this embodiment, a first dimming control means 3 based on lamp current stop interval control, and a second In addition to the dimming control means 4, a third dimming control means 6 is added. By using such a circuit configuration, each dimming control width by the first dimming control means 3 and the third dimming control means 6, for example, the frequency variation fhi width in the frequency side control, the input voltage control In this case, input voltage variation (width) and duty variation fl can be suppressed to a small value in duty control.

For example, in the specific circuit example of the second embodiment, input voltage amplitude control using a step-down chopper circuit is used as the second dimming control means 4, and the variation range is 0 to 282V. However, in a step-down chip copper circuit, input current distortion generally increases as the output increases. Therefore, if, for example, a frequency control method is used in conjunction with the third dimming control means 6, it is possible to reduce the range of change in the input voltage caused by the step-down chopper circuit. For example, there is no need to use 141 V to 282 V).

Of course, even if the second dimming control means 4 uses a dimming side control method other than input voltage control, there is an effect of using the third dimming control means 6 in combination. For example, if the second dimming control means 4 uses a frequency control method, and the frequency change width is large,
4 m3 is difficult, but by using the third dimming control means 6 in combination, the frequency change range in the second dimming control means 4 can be reduced, and noise countermeasures can be easily taken.

In addition, the duty control method 3 is applied to the second one-light $ control means 4.
If the duty change width is large, inrush current may flow due to the on-duty being restricted too much.
The current flowing through the switching element may become a phase-advanced waveform, but by using the third dimming control means 6 in combination, there is no need to narrow down the on-duty too much, and generation of inrush current and phase-advanced waveform can be prevented. It is something that can be done.

[Effects of the Invention] According to the present invention, as described above, the discharge lamp is controlled using the first dimming control based on the lamp current rest period control and the second dimming control other than the lamp current rest period control. By dimming, it is possible to always provide a lamp current pause section at a dimming level that causes flickering or sudden changes in light output due to sudden changes in lamp current, thus reducing the amount of change in lamp current seen macroscopically. This has the effect of reducing flickering and sudden changes in light output to a level that is imperceptible to the human eye.

Note that the dimming control during low light output is performed by a second dimming control means other than the lamp current rest period control, and the dimming control during high light output is performed by the first dimming control means using the lamp current rest period. If this is done, the degree of freedom in dimming control will be greater than when dimming is performed only by lamp current rest period control, and the effect of suppressing discharge lamp flickering and sudden changes in light output will be the highest. , it becomes possible to perform lamp current stop interval control.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a pond of the present invention, and FIGS. 3(a) and (b) are same as above. 4 and 5 are the same dynamic fV waveform diagrams as above. FIG. 6 is a block diagram showing the schematic configuration of still another embodiment of the present invention. FIG. 7 is a diagram of the conventional example. It is an operation explanatory diagram. 1 is a high frequency generation circuit, 2 is a discharge lamp, 3 is a first dimming control means, and 4 is a second dimming control means. Figure 1

Claims (1)

[Claims] (1) A high frequency generation circuit, a discharge lamp serving as a load of the high frequency generation circuit, a first dimming control means for controlling a load current rest period of the high frequency generation circuit, and a load power control other than load current rest period control. A discharge lamp lighting device characterized by comprising: second dimming control means for controlling.