JPH08273869A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE: To provide a discharge lamp lighting device capable of preventing lighting failure of a discharge lamp caused by dimming control, preventing drop in efficiency, and reducing electromagnetic noise. CONSTITUTION: One electric feeder line 2 connected to a high frequency constant current source 1 is passed through a current transformer 3, a discharge lamp 5 is connected to both ends of a secondary winding 4 of the current transformer 3, and a capacitor Co is connected to across terminals on a non-power source side of the discharge lamp 5. High frequency constant current Io is supplied to the feeder line 2 from the high frequency constant current source 1, current ILa excited in the secondary winding 4 with the high frequency constant current Io is supplied to the discharge lamp 5 as the lamp current ILa. The lamp current ILa is controlled with a frequency (f) of the high frequency constant current Io flowing through the feeder line 2, or by varying the capacitor Co. A discharge lamp lighting device capable of preventing lighting failure of the discharge lamp caused by dimming control, preventing drop in efficiency, reducing electromagnetic noise, and reducing transfer to a phase advanced mode in the inverter circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp, and more particularly to a discharge lamp lighting device using a high frequency constant current power supply system.

[0002]

2. Description of the Related Art Conventionally, in a high frequency constant current power supply system,
As a discharge lamp lighting device capable of changing the lamp current ILa of the discharge lamp by changing the frequency thereof
There is one disclosed in Japanese Patent Publication No. 990, and its block configuration diagram is the same as the block configuration diagram according to the present invention. Therefore,
This conventional example will be described below with reference to FIG.

In this conventional example, a current transformer 3 is allowed to pass through one power supply line 2 connected to a high frequency constant current source 1, and a discharge lamp 5 is connected to both ends of a secondary winding 4 of the current transformer 3. A capacitor Co is connected between the non-power source side terminals of the discharge lamp 5, and a high frequency constant current Io is fed from the high frequency constant current source 1 to the power supply line 2.
Is supplied to the discharge lamp 5 as the lamp current ILa, and the current ILa excited in the secondary winding 4 by the high frequency constant current Io is supplied to the discharge lamp 5. The lamp current ILa can be controlled by changing the capacitance Co of the capacitor Co.

Here, the impedance | Z | of the capacitor Co is expressed by | Z | = 1 / (2πfCo) ... (1) , When the value of the frequency f is increased,
As shown in, the impedance | Z | of the capacitor Co becomes small. Further, even if the value of the capacitor Co is increased, the impedance | Z | of the capacitor Co decreases. When the impedance | Z | of the capacitor Co decreases,
The current flowing through the capacitor Co increases and the lamp current IL
a decreases. Therefore, by reducing the frequency f of the high frequency constant current flowing through the power supply line 2 or the capacitance of the capacitor Co, the lamp current ILa can be increased and the light output of the discharge lamp 5 can be increased.

FIG. 22 shows the relationship between the voltage across the discharge lamp 5 (hereinafter referred to as the lamp voltage) VLa and the frequency f (hereinafter referred to as the frequency characteristic), and FIG. 22 (b) shows that the lamp resistance RLa is 100% when loaded.
22C, when the lamp resistance La is 80%, that is, when the discharge lamp 5 is 80% dimming, in FIG. 22D, the lamp resistance RLa is 50%.
Time, that is, the time when 50% dimming of the discharge lamp 5 is turned on. Also,
fo is the resonance frequency at no load,

[0006]

[Equation 1]

Resonance frequency fo1 under load
Is

[0008]

[Equation 2]

It is represented by However, Lo indicates the wiring inductance value and the leakage inductance value of the current transformer 3.

Here, since a discharge lamp generally has a negative characteristic, if the dimming control is performed so as to reduce the light output of the discharge lamp, the minimum lamp voltage required for lighting the discharge lamp (= minimum lighting maintaining voltage). Is getting bigger. Further, since it is necessary to apply a lamp voltage higher than the minimum lighting maintaining voltage to the discharge lamp in order to maintain lighting of the discharge lamp, it is necessary to increase the lamp voltage as the minimum lighting maintaining voltage increases.

When f = f1 (<fo), the discharge lamp 5 is f
Assuming that all lights are on, the lamp voltage VLa becomes V1 as indicated by point A on the curve in FIG. Next, the frequency f is increased to f2 (> f1) and the discharge lamp 5 is set to 8
When the dimming lighting is performed to 0%, the lamp voltage VLa becomes V2 (> V1) and the lamp voltage VLa rises as shown by the point B on the curve of FIG. 22 (c). Furthermore, the frequency f is changed to f3 (> f
If the discharge lamp 5 is dimmed to 50% by increasing it to 2),
As indicated by point C on the curve of FIG. 22 (d), the lamp voltage VL
a becomes V3 (> V2), and the lamp voltage VLa further rises.

[0012]

However, in the above-mentioned conventional example, if the frequency f is increased to f4 (> f3) in order to control the light output of the discharge lamp 5 to be less than 50%, The lamp voltage VLa must be made higher than the voltage V3, but the curve of FIG. 22 (a) makes it impossible to satisfy the minimum lighting maintaining voltage, and the discharge lamp 5 goes out.
The first problem arises.

In addition, if the frequency f is made extremely high, the switching loss and the core loss of the secondary winding 4 increase, which lowers the efficiency and increases the electromagnetic noise due to the high frequency. Problems arise.

The present invention has been made in view of the above first and second problems, and an object of the present invention is to prevent extinction of a discharge lamp due to dimming control and prevent deterioration of efficiency. It is possible to provide a discharge lamp lighting device that is capable of reducing electromagnetic noise.

[0015]

In order to solve the above problems, according to the invention described in claims 1 to 17,
When the light output of the discharge lamp is large, the control circuit keeps the DC voltage output of the power supply circuit substantially constant and changes the operating frequency of the inverter circuit to control the dimming of the discharge lamp, and the light output of the discharge lamp. Is small, the operating frequency of the inverter circuit is changed stepwise or continuously, the DC voltage output of the power supply circuit is changed stepwise or continuously, and the inverter circuit is PWM-controlled to pulse At least one of varying the width stepwise or continuously
It is characterized in that dimming control of the discharge lamp is performed by performing one of the two.

According to the eighteenth aspect of the present invention, the power supply circuit is a boost chopper circuit.

[0017]

According to the present invention, by supplying the alternating current high frequency constant current from the constant current source to the current transformer, the current excited in the secondary winding of the current transformer is supplied to the discharge lamp to light the discharge lamp. To do. When controlling the dimming control of the discharge lamp, if the light output of the discharge lamp is large, the control circuit keeps the DC voltage output of the power supply circuit substantially constant, and the operating frequency of the inverter circuit is changed to change the current transformer. The dimming control of the discharge lamp is performed by controlling the alternating high frequency constant current supplied to the primary winding of the discharge lamp and controlling the current excited in the secondary winding of the current transformer.

When the light output of the discharge lamp is small, the operating frequency of the inverter circuit is changed stepwise or continuously by the control circuit, and the DC voltage output of the power supply circuit is changed stepwise or continuously. And PWM control of the inverter circuit to change the pulse width in a stepwise or continuous manner to perform at least one of high frequency constant of the alternating current supplied to the primary winding of the current transformer. The current is controlled, and the current excited in the secondary winding of the current transformer is controlled to dimming the discharge lamp.

[0019]

【Example】

(Embodiment 1) FIG. 1 is a block diagram of the first embodiment according to the present invention. The difference from the above-mentioned conventional example is a method of controlling the current Io. Note that the same configurations as those of the other conventional examples are denoted by the same reference numerals, and description thereof will be omitted.

The specific circuit of FIG. 1 is shown in FIG. The high frequency constant current source 1 transforms a DC voltage obtained by rectifying the AC power supply AC via the rectifier DB into a DC voltage Vdc in the power supply circuit CH,
The DC voltage Vdc is converted into an AC high frequency voltage by the inverter circuit INV, and the power supply circuit CH and the inverter circuit INV are controlled by the control circuit 8.

The power supply circuit CH (hereinafter referred to as a step-up chopper circuit) is a so-called step-up chopper circuit which is composed of an inductance element L1, a switching element Q1, a diode D1 and a capacitor C1 and which can improve the input current distortion. Yes, the switching element Q1 is a chopper control circuit C
The high frequency is controlled by the HCL.

The inverter circuit INV is a so-called full-bridge type inverter circuit composed of switching elements Q2 to Q5 and diodes D2 to D5 connected in antiparallel to both ends of each of the switching elements Q2 to Q5. ,
The inverter control circuit INVCL controls the switching elements Q2 to Q5 as follows, and operates as follows.

In the first state in which the switching elements Q2 and Q5 are turned on and the switching elements Q3 and Q4 are turned off, the current Io changes from the capacitor C1 to the switching element Q.
It flows in the order of 2 → current transformer 32 → current transformer 31 → switching element Q5 → capacitor C1. In the second state in which the switching elements Q2 to Q5 are turned off, the current Io is the current transformer 32 → current transformer 31 → diode D4 → capacitor C1 → diode D3 → current transformer 32 in this order. Transformer 31, current transformer 3
It flows as a regenerative current from 2. Switching element Q
In the third state in which 2, Q5 are off and switching elements Q3, Q4 are on, the current Io is equal to the capacitor C1.
→ Switching element Q4 → Current transformer 31 → Current transformer 32 → Switching element Q3 → Capacitor C1. In the fourth state in which the switching elements Q2 to Q5 are turned off again, the current Io is equal to the current transformer 31.
→ current transformer 32 → diode D2 → capacitor C1
→ Diode D5 → Current transformer 31 flows in this order as regenerative currents from the current transformers 31 and 32. And
In the first to fourth states, the current Io flows through the current transformers 31 and 32 to excite the secondary currents in the secondary windings 41 and 42 to supply high-frequency currents to the discharge lamps 51 and 52. Light up.

The control circuit 8 inputs the dimming signal Vsig to the comparison circuit COMP, controls the inverter circuit INV by the inverter control circuit INVCL until the dimming signal Vsig exceeds the reference value, and the dimming signal Vsig is the reference value. When the value exceeds, the booster chopper circuit CH is controlled by the chopper control circuit CHCL.

Further, a power supply line 2 of several tens of meters is connected to the output end of the high frequency constant current source 1, current transformers 31 and 32 are connected in series to the power supply line 2, and current transformers 31 and 3 are connected.
Discharge lamps 51 and 52 are connected to both ends of the two secondary windings 41 and 42, respectively. Capacitors C11 and C12 are connected between the non-power supply side terminals of the discharge lamps 51 and 52, respectively.

A concrete circuit example of the control circuit 8 is shown in FIG. The inverter control circuit INVCL is an inverter control IC
(For example, μPC494 manufactured by NEC Corporation) 10 (hereinafter referred to as IC1
Call it 0. ), A capacitor C3 connected between the CT terminal of the IC10 and the ground, a current mirror composed of a switching element Q6 and a switching element Q7 having an emitter connected to the RT terminal of the IC10, and a diode connected to the collector of the switching element Q6. -D6, resistor R1
Of the switching element Q6 via the resistor R1
And a Zener diode ZD connected between the emitter and collector of the.

The chopper control circuit CHCL includes a chopper control IC 11 (for example, FA5331 manufactured by Fuji Electric Co., Ltd.)
Switching element Q8 connected between external power supply Vcc and ground, external power supply Vcc and chopper control IC
11 (hereinafter referred to as IC11) and a resistor R5 connected in series between ON / OFF terminals.

The comparator circuit COMP is a voltage V which is obtained by dividing the external power supply Vcc by the resistors R2 and R3 in the comparator COM.
a and the dimming signal Vsig via the diode D7 are compared and output, and the output signal is applied from the external power supply Vcc to the base of the switching element Q8 via the resistor R4.

Next, the operation of the circuit shown in FIG. 3 will be briefly described. When the dimming signal Vsig is smaller than the voltage Va, the output of the comparator COM becomes a low level (L level), the switching element Q8 is turned off, the external power supply Vcc is applied to the IC11 via the resistor R5, and the IC11 is at a high level. Outputs (H level) signal and boost chopper circuit CH
Outputs a substantially constant DC voltage Vdc.

Further, from the dimming signal Vsig, the diode D
6, a current is passed through the base of the switching element Q6 via the resistor R1 to turn on the switching element Q6,
The switching element Q7 is also turned on to operate the IC10. When the dimming signal Vsig changes, the frequency f of the inverter circuit INV changes by the IC 10 and the discharge lamp 5 can be dimmed. However, Zener diode ZD
Accordingly, the value of the dimming signal Vsig supplied to the inverter control circuit INVCL does not exceed the voltage VZD across the Zener diode ZD (hereinafter referred to as the DC voltage VZD), and is maintained substantially equal to the DC voltage VZD. , The frequency f is kept constant.

When the dimming signal Vsig becomes larger than the voltage Va, the output of the comparator COM becomes H level, the switching element Q8 is turned on and the output of the IC11 is turned off. Since the operation of the step-up chopper circuit CH is stopped, the DC voltage V
dc decreases, and dimming by the boost chopper circuit CH can be performed. Here, if the voltage Va is set to be substantially equal to the DC voltage VZD, the switching between the inverter circuit INV and the step-up chopper circuit CH is smoothly performed, and the frequency f of the inverter circuit INV at this time is f2 (> f0). To

FIG. 4 shows the frequency characteristic in this embodiment. Assuming that the discharge lamp 5 is fully lit at f = f1 (<fo), the lamp voltage VLa becomes V1 as indicated by point A on the curve of FIG. 4 (b). Next, the frequency f is changed to f by changing the dimming signal Vsig.
When the discharge lamp 5 is dimmed to 80% by increasing it to 2 (> f1), the lamp voltage VLa becomes V2 (> V1) as indicated by the point B on the curve of FIG. 4C, and the lamp voltage VLa Rises.

Further, if the frequency f is kept constant at f2 by changing the dimming signal Vsig and the boost chopper circuit CH is stopped, the DC voltage output Vdc of the boost chopper circuit CH decreases and the lamp voltage VLa decreases. , All curves as shown in FIGS. 4 (a) to 4 (d) are lowered as a whole. That is, if the dimming signal Vsig is changed so that the discharge lamp 5 is dimmed to 50%, the lamp voltage VLa should change to V3 as shown at point C on the curve of FIG. 4D. , F = f2, so that the lamp voltage VLa changes to V3 as shown at point D in FIG. In this embodiment, a step-down chopper circuit and a step-up / step-down chopper circuit may be used, and the inverter may be a half bridge type.

(Second Embodiment) FIG. 5 shows a circuit diagram of a second embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 3 is that the Zener diode ZD is omitted, and the same components as those of the other first embodiment are denoted by the same reference numerals and the description thereof is omitted.

In this embodiment, the inverter control circuit INV
Since no upper limit is set for the value of the dimming signal Vsig input to CL, when f> f2, the boost chopper circuit CH
Since the dimming control can be performed by stopping the operation of the above, and the dimming control by the inverter circuit INV can be performed, when f> f2, for example, the lamp voltage VLa is V5 as shown at point E in FIG. become. The above first and second
Although the dimming control is performed by stopping the boost chopper circuit CH in the embodiment, the dimming control may be performed by operating the boost chopper circuit CH.

(Embodiment 3) A circuit diagram of a third embodiment according to the present invention is shown in FIG.

The difference from the first embodiment shown in FIG. 3 is that the chopper control circuit CHCL is the chopper control circuit CHCL2.
The continuous dimming control by the DC voltage Vdc is performed, and the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

The chopper control circuit CHCL2 generates a voltage Vb obtained by dividing the dimming signal Vsig by the resistor R5 and the variable resistor VR and a voltage Vc obtained by dividing the DC voltage Vdc by the resistors R8 and R9 via the switching element Q8. , Diode D
Compared with 8 and D9, the larger voltage is Vin of IC11.
It is input to the-terminal, and the external power supply Vcc is connected to the resistor R
2, the voltage Va divided by R3 and the dimming signal Vsig are compared and output by the comparator COM, and the external power source Vcc and the resistor R4 are output.
It is applied to the base of the switching element Q8 via R8 to control the switching element Q8. Also, IC11 Vi
The n-terminal is an operational amplifier which is fed back by the resistor R7 and the capacitor C4 through the VFB terminal.

Next, the operation will be briefly described. Dimming signal Vs
When the ig is lower than the voltage Va, the dimming control by the inverter circuit INV is performed according to the change of the dimming signal Vsig, and the comparator COM outputs the H level signal to turn off the switching element Q8. The voltage Vc is input to the Vin− terminal, and the chopper control circuit CHCL2
Controls the boost chopper circuit CH.

When the dimming signal Vsig reaches the voltage Va,
As described above, the frequency f of the inverter circuit INV is kept constant, and the comparator COM outputs an L level signal to turn on the switching element Q8. Dimming signal Vsig
Is much larger than the DC voltage Vdc, Vb> Vc
If the variable resistor VR is set so that
Is turned on and diode D9 is turned off.
The voltage Vb is input to the in-terminal, and the step-up chopper circuit CH is controlled by the chopper control circuit CHCL2 to reduce the DC voltage Vdc. When the variable resistance VR is changed here, the voltage input to the Vin- terminal of the IC 11 continuously changes, and the DC voltage Vdc can be continuously changed, and continuous dimming by the step-up chopper circuit CH is performed. can do.

FIG. 8 shows the frequency characteristic in this embodiment. When the frequency f is kept constant at f2 by changing the dimming signal Vsig, and the step-up chopper circuit CH is controlled to continuously reduce the DC voltage output Vdc of the step-up chopper circuit CH, FIG. All curves as shown in d) are totally lowered. That is, when the dimming signal Vsig is changed so that the frequency f is kept constant at f2 and the discharge lamp 5 is dimmed to 50%, the lamp voltage VLa is changed as shown at point F on the curve of FIG. 8D. Changes to V6. That is, by controlling the boost chopper circuit CH, dimming of 80% or less can be continuously performed.

(Fourth Embodiment) FIG. 9 shows a circuit diagram of a fourth embodiment according to the present invention.

The difference from the third embodiment shown in FIG. 7 is that the Zener diode ZD is omitted, and the same components as those of the other third embodiment are designated by the same reference numerals and their description is omitted.

In this embodiment, the inverter control circuit INV
Since no upper limit is set for the value of the dimming signal Vsig input to CL, when f> f2, the boost chopper circuit CH
The dimming control by 2 and the inverter circuit INV
Since the dimming control can be performed by, the lamp voltage VLa becomes V7 at f> f2, as shown at point G in FIG. 10, for example.

With the configuration as described in the first to fourth embodiments, the dimming can be performed without changing the frequency f so much that the discharge lamp is prevented from extinguishing, noise is suppressed, and switching loss is reduced. It is possible to reduce.

Further, by switching the order of the dimming control from the dimming control by the inverter circuit INV to the dimming control by the step-up chopper circuit CH, FIG.
At a frequency (for example, f2) higher than the natural vibration frequency fo (= frequency of maximum value of output voltage) of each curve shown in (d),
Since the dimming control is performed by the inverter circuit INV, there is an advantage that the possibility that the inverter circuit INV enters the phase advance mode is extremely reduced. If the inverter circuit INV enters the phase advance mode, the switching element Q2
~ Inrush current flows when Q5 is turned on, and a large stress is applied to the switching elements Q2 to Q5, causing characteristic deterioration. Therefore, the inverter circuit INV can operate stably in the delay mode.

(Fifth Embodiment) FIG. 11 shows a circuit diagram of a fifth embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 3 is that I
The control circuit X for controlling the DEADTIME terminal (hereinafter referred to as the DT terminal) of the C10 is provided, and the inverter circuit INV is PWM-operated to perform the dimming control. The same configurations will be denoted by the same reference numerals and the description thereof will be omitted.

The control circuit X is constructed as follows. IC1
An external power supply Vref is connected to the resistors R24 and R at the DT terminal of 0.
The voltage Vd divided by 25 is applied via the resistor R26, and the voltage Vd is applied via the diode D8 and the resistor R38. Further, the output of the control circuit X is applied to the DT terminal of the IC 10 through the series connection of the resistors R38, R39, R40 and R41.

The control circuit X controls the resistance R37 via the resistance R37.
A control circuit X1 for controlling the switching element Q28 connected to both ends of the series connection of 39, R40 and R41, a control circuit X2 for controlling the switching element Q30 connected to both ends of the series connection of the resistors R40 and R41, and a resistor R41
Switching element Q32 connected at both ends of the series connection of
And a control circuit X3 for controlling the
1, the control circuit X2, and the control circuit X3 are controlled by the dimming signal Vsig.

The control circuit X1 is provided in the comparator COM1.
Voltage V obtained by dividing external power supply Vcc by resistors R32 and R33
a1 and the dimming signal Vsig via the diode D37 are compared and output, and resistors R34, R35,
An output signal is applied to the base of the switching element Q28 via R36. The control circuit X2 is a comparator C
In the OM2, the voltage Va2 (> Va1) obtained by dividing the external power supply Vcc by the resistors R12 and R13 is compared with the dimming signal Vsig via the diode D17, and the external power supply Vc is output.
The output signal is applied from c to the base of the switching element Q30 via the resistors R14, R15, R16, R17 and the switching element Q29. The control circuit X3 is
In the comparator COM3, the external power supply Vcc is connected to the resistor R18,
The voltage Va3 (> Va2) divided by R19 and the dimming signal Vsig via the diode D27 are compared and output, and resistors R20, R21, R22, R23,
Switching element Q3 via switching element Q31
The output signal is applied to the base of No. 2.

Next, the operation of the circuit shown in FIG. 11 will be briefly described. First, since the switching elements Q29, Q31 are off, the switching elements Q30, Q32 are on by the external power supply Vcc.

The dimming signal Vsig is the voltage Va1, Va2,
If it is smaller than Va3, the comparators COM1, COM
2, the outputs of COM3 are all at L level, the switching elements Q28, Q29, Q31 are turned off, and the dimming signal Vs
ig is not applied to the DT terminal, the frequency f of the IC 10 changes due to the change of the dimming signal Vsig input to the RT terminal, the frequency f of the inverter circuit INV changes, and the dimming control by the inverter circuit INV starts. Dimming signal Vs
Until ig reaches a certain level, the inverter circuit IN
Only the dimming control by V is performed, and thereafter, the frequency f of the inverter circuit INV is kept constant.

When the dimming signal Vsig exceeds the voltage Va1, the output of the comparator COM1 becomes H level, the switching element Q28 is turned on, and the dimming signal Vsig is given to the resistor R39 via the resistor R37, that is, the resistor. R3
The DT terminal of the IC 10 can be controlled by the voltage applied to the IC 9 to change the pulse width of the output signal of the IC 10. When the dimming signal Vsig exceeds the voltage Va2, the output of the comparator COM2 becomes H level, the switching element Q29 also turns on, the switching element Q30 turns off, and the resistors R39 and R40 are connected in series to the dimming signal Vsig.
Is given, that is, the voltage applied to the series connection of the resistors R39 and R40 controls the DT terminal of the IC10 to
The pulse width of the output signal of 10 is set to the switching element Q28.
Only when turned on can be narrower. Dimming signal Vsi
When g exceeds the voltage Va3, the output of the comparator COM3 becomes H
And the switching element Q31 is turned on,
The switching element Q32 also turns off and the resistors R39 and R4
The dimming signal Vsig is given to the series connection of 0 and R41,
That is, the DT terminal of the IC10 is controlled by the voltage applied to the series connection of the resistors R39, R40 and R41 to control the IC10.
The pulse width of the output signal of the switching element Q28, Q
Only 29 can be made narrower than when it is on.

In this way, stepwise dimming is possible by PWM controlling the output of the IC 10. FIG. 12 shows frequency characteristics in this embodiment.

By varying the dimming signal Vsig, the frequency f is kept constant at f2, and at the same time, the dimming signal Vsig is changed.
And the voltage exceeds the voltage Va1, the inverter circuit IN
V is PWM-controlled to increase the lamp voltage VLa, and the lamp voltage VLa becomes V7 as shown at point H in FIG.
When the dimming signal Vsig is further changed to exceed the voltage Va2, the lamp voltage VLa also increases, and the lamp voltage VLa becomes V8 as shown at point J in FIG.

(Sixth Embodiment) FIG. 13 shows a circuit diagram of a sixth embodiment according to the present invention.

The difference from the fifth embodiment shown in FIG. 11 is that
The Zener diode ZD is omitted, and the same configurations as those of the other fifth embodiment are denoted by the same reference numerals and the description thereof will be omitted.

In this embodiment, the inverter control circuit INV
Since the upper limit is not set for the value of the dimming signal Vsig input to CL, when f> f2, the inverter circuit INV
Since the dimming control can be performed by the frequency change of 1 and the PWM dimming control can be performed by the inverter circuit INV, when f> f2, for example, the lamp voltage VLa is V9 as shown at points K and L in FIG. , V10.

(Embodiment 7) A circuit diagram of a seventh embodiment according to the present invention is shown in FIG.

The difference from the fifth embodiment shown in FIG. 11 is that
Only a series connection of resistors R38 and R39 is connected to the DT terminal of the IC10, a switching element Q39 controlled by turning on / off the switching element Q28 controlled by the control circuit X1, and a diode connected in series with the switching element Q39. The configuration is such that the dimming signal Vsig is given to the resistor R39 via D28, and the same configurations as those of the other fifth embodiment are denoted by the same reference numerals and the description thereof will be omitted.

Next, the operation will be briefly described. Dimming signal Vs
If ig is smaller than the voltage Va1, the comparator COM1
Of the switching element Q28, Q
39 is turned off, the dimming signal Vsig is not applied to the DT terminal, the frequency f of the IC 10 is changed by the change of the dimming signal Vsig input to the RT terminal, and the inverter circuit INV
The frequency f changes and the dimming control by the inverter circuit INV starts.

Until the dimming signal Vsig reaches a certain level, only the dimming control by the inverter circuit INV is performed, and thereafter, the frequency f of the inverter circuit INV is kept constant. When the dimming signal Vsig exceeds the voltage Va1, the output of the comparator COM1 becomes H level, the switching elements Q28 and Q39 are turned on, and the dimming signal Vsig is given to the resistor R39. And the dimming signal Vsig
By changing, that is, by continuously changing the voltage applied to the resistor R39, the DT terminal of the IC10 is controlled to continuously change the pulse width of the output signal of the IC10, and the inverter circuit INV is continuously changed. The PWM control can be performed to perform the dimming control.

FIG. 16 shows the frequency characteristic in this embodiment. By varying the dimming signal Vsig, the frequency f is kept constant at f2 and the dimming signal Vs
When ig is changed to exceed the voltage Va1, the inverter circuit INV is PWM-controlled, the lamp voltage VLa increases, and the lamp voltage VLa is V11 as shown at point H in FIG.
Becomes

(Embodiment 8) A circuit diagram of an eighth embodiment according to the present invention is shown in FIG.

The difference from the seventh embodiment shown in FIG. 15 is that
The Zener diode ZD is omitted, and the same configurations as those of the other seventh embodiment are denoted by the same reference numerals and the description thereof is omitted.

In this embodiment, the inverter control circuit INV
Since the upper limit is not set for the value of the dimming signal Vsig input to CL, when f> f2, the inverter circuit INV
The dimming control can be performed by the frequency change and the PWM dimming control can be performed by the inverter circuit INV. Therefore, when f> f2, for example, the lamp voltage VLa becomes V12 as shown at the point K in FIG. .

With the configuration as shown in the above fifth to eighth embodiments, since the dimming can be performed without changing the frequency f so much, the discharge lamp is prevented from extinguishing, the noise is suppressed, and the switching loss is reduced. Can be reduced.

By changing the order of the dimming control from the dimming control by the frequency control of the inverter circuit INV to the dimming control by the PWM control of the inverter circuit INV, FIGS. 12 and 14A to 14D are shown. ) Natural vibration frequency fo of each curve shown in () (= frequency of maximum value of output voltage)
At a higher frequency (eg f2), the inverter circuit IN
Since the dimming control by V is performed, the inverter circuit INV
Has the merit that the possibility of entering the phase advance mode is extremely low.

In all the above embodiments, the dimming signal V
As a means for obtaining sig, for example, the configuration shown in FIG. 19 may be adopted. That is, the substantially rectangular wave dimming signal is rectified through the rectifier DB and the resistor R51. Then, a current is supplied to the photodiode of the photocoupler PC to turn on / off the phototransistor of the photocoupler PC. By turning on / off the resistors R52 and R5 from the external power supply Vcc.
The dimming signal is converted to Vsig by charging the electrolytic capacitor C51 connected to both ends of the phototransistor of the photocoupler PC via R3 and R54.

Furthermore, the above-mentioned first to fourth embodiments and the above-mentioned fifth to eighth embodiments may be combined respectively,
With such a configuration, dimming can be performed without further changing the frequency f, as compared with the first to eighth embodiments, so that the discharge lamp is prevented from extinguishing, noise is suppressed, and switching loss is reduced. It is possible to reduce.

The order of dimming is determined by the inverter circuit IN
By switching from dimming control by V frequency control to dimming control by the chopper circuit CH and PWM control of the inverter circuit INV, it is higher than the natural vibration frequency fo (frequency of maximum value of output voltage). Since the dimming control by the inverter circuit INV is performed at the frequency (for example, f2), there is an advantage that the possibility that the inverter circuit INV enters the phase advance mode is extremely reduced.

[0074]

According to the inventions of claims 1 to 17, the discharge lamp is prevented from extinguishing by dimming control, the efficiency is prevented from decreasing, the electromagnetic noise is reduced, and the inverter circuit is put into the phase advance mode. It is possible to provide a discharge lamp lighting device capable of reducing entry.

According to the eighteenth aspect of the present invention, the improvement of the input current distortion and the prevention of the extinction of the discharge lamp by the dimming control,
It is possible to provide a discharge lamp lighting device capable of preventing a decrease in efficiency, reducing electromagnetic noise, and reducing the inverter circuit from entering a phase advance mode.

[Brief description of drawings]

FIG. 1 shows a block diagram according to the present invention.

FIG. 2 shows a specific circuit diagram according to the present invention.

FIG. 3 shows a circuit diagram of a first embodiment according to the present invention.

FIG. 4 is a diagram showing frequency characteristics of the above embodiment.

FIG. 5 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 6 is a diagram showing frequency characteristics of the above embodiment.

FIG. 7 shows a circuit diagram of a third embodiment according to the present invention.

FIG. 8 is a diagram showing frequency characteristics of the above embodiment.

FIG. 9 shows a circuit diagram of a fourth embodiment according to the present invention.

FIG. 10 is a diagram showing frequency characteristics of the above embodiment.

FIG. 11 shows a circuit diagram of a fifth embodiment according to the present invention.

FIG. 12 is a diagram showing frequency characteristics of the above embodiment.

FIG. 13 shows a circuit diagram of a sixth embodiment according to the present invention.

FIG. 14 is a diagram showing frequency characteristics of the embodiment.

FIG. 15 shows a circuit diagram of a seventh embodiment according to the present invention.

FIG. 16 is a diagram showing frequency characteristics of the embodiment.

FIG. 17 shows a circuit diagram of an eighth embodiment according to the present invention.

FIG. 18 is a diagram showing frequency characteristics of the above-mentioned embodiment.

FIG. 19 is a diagram showing a specific circuit example for obtaining a dimming signal.

FIG. 20 shows a circuit diagram on the load side according to the block configuration of the present apparatus.

FIG. 21 is a characteristic diagram showing a relationship between impedance of a capacitor and frequency.

FIG. 22 is a diagram showing frequency characteristics of a conventional example according to the present invention.

[Explanation of reference numerals] 1 constant current source 3 current transformer 5 discharge lamp 8 control circuit CH power supply circuit f frequency INV inverter circuit Vdc DC voltage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Fujimoto 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (18)

[Claims] 1. A discharge lamp and a current transformer having secondary windings connected to both ends of a constant current source, and by supplying an alternating high frequency constant current from the constant current source to the current transformer. In a discharge lamp lighting device for supplying a current excited in the secondary winding to the discharge lamp, the constant current source includes a power supply circuit for converting an AC power supply into a DC voltage output,
The DC voltage output of the power supply circuit is converted to an AC high frequency voltage, an inverter circuit for obtaining an AC high frequency constant current output, and a control circuit for driving the power supply circuit and the inverter circuit, the control circuit, When the light output of the discharge lamp is high,
A discharge lamp lighting device, characterized in that the direct current voltage output of the power supply circuit is made substantially constant, and the operating frequency of the inverter circuit is varied to perform dimming control of the discharge lamp. 2. The control circuit, when the light output of the discharge lamp is small, changes the DC voltage output of the power supply circuit stepwise and makes the operating frequency of the inverter circuit substantially constant, so that the discharge voltage is kept constant. The discharge lamp lighting device according to claim 1, wherein the electric lamp is for dimming control. 3. When the light output of the discharge lamp is small, the control circuit gradually changes the DC voltage output of the power supply circuit and changes the operating frequency of the inverter circuit to change the operating frequency of the discharge lamp. 2. The discharge lamp lighting device according to claim 1, wherein the dimming control is performed. 4. The control circuit, when the light output of the discharge lamp is small, continuously changes the direct current voltage output of the power supply circuit and keeps the operating frequency of the inverter circuit substantially constant, thereby controlling the discharge frequency. The discharge lamp lighting device according to claim 1, wherein the electric lamp is for dimming control. 5. The control circuit continuously changes the DC voltage output of the power supply circuit and changes the operating frequency of the inverter circuit when the light output of the discharge lamp is small, thereby changing the operating frequency of the inverter circuit. 2. The discharge lamp lighting device according to claim 1, wherein the dimming control is performed. 6. The control circuit, when the light output of the discharge lamp is small, performs PWM control of the inverter circuit to change the pulse width stepwise, thereby performing dimming control of the discharge lamp. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is provided. 7. When the light output of the discharge lamp is small, the control circuit changes the operating frequency of the inverter circuit and PWM-controls the inverter circuit to change the pulse width stepwise. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled. 8. The control circuit dimming-controls the discharge lamp by PWM-controlling the inverter circuit to continuously change the pulse width when the light output of the discharge lamp is small. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is provided. 9. The control circuit, when the light output of the discharge lamp is small, changes the operating frequency of the inverter circuit and PWM-controls the inverter circuit to continuously change the pulse width. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled. 10. The control circuit, when the light output of the discharge lamp is small, changes the DC voltage output of the power supply circuit stepwise, and PWM-controls the inverter circuit to change the pulse width stepwise. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by changing the discharge lamp. 11. The control circuit, when the light output of the discharge lamp is small, gradually changes the DC voltage output of the power supply circuit and PWM-controls the inverter circuit to continuously change the pulse width. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by changing the discharge lamp. 12. The control circuit, when the light output of the discharge lamp is small, continuously changes the DC voltage output of the power supply circuit and PWM-controls the inverter circuit to gradually change the pulse width. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by changing the discharge lamp. 13. The control circuit continuously changes the DC voltage output of the power supply circuit and PWM-controls the inverter circuit to continuously change the pulse width when the light output of the discharge lamp is small. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by changing the discharge lamp. 14. The control circuit gradually changes the DC voltage output of the power supply circuit and varies the operating frequency of the inverter circuit when the light output of the discharge lamp is small, and the inverter circuit 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by PWM controlling the pulse width to change the pulse width stepwise. 15. The control circuit gradually changes the DC voltage output of the power supply circuit and changes the operating frequency of the inverter circuit when the light output of the discharge lamp is small, and the inverter circuit 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by PWM controlling the pulse width to continuously change the pulse width. 16. The control circuit continuously changes the DC voltage output of the power supply circuit and changes the operating frequency of the inverter circuit when the light output of the discharge lamp is small, and the control circuit changes the operating frequency of the inverter circuit. 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by PWM controlling the pulse width to change the pulse width stepwise. 17. The control circuit continuously changes the DC voltage output of the power supply circuit and varies the operating frequency of the inverter circuit when the light output of the discharge lamp is small, and the inverter circuit 2. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is dimming-controlled by PWM controlling the pulse width to continuously change the pulse width. 18. The discharge lamp lighting device according to claim 1, wherein the power supply circuit is a boost chopper circuit.