JPH07235391A - Dimming device of discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To make dimming which is free from flickers. CONSTITUTION:The commercial AC electric supply are ratified by a rectifier 13, and the output is converted into high frequency power using an inverter 34 and supplied to a discharge tube 32 via a transformer 16. A charge/discharge circuit is formed from a variable resistor 43, diodes 44, 45, and capacitor 46, and the capacitor 46 is discharged by turning on a transistor 57 in pulsation at each zoo-cross of the commercial power in conformity to the signal given by a rectifier circuit consisting of diodes 53, 54, resistor 55, and photo=diode 56, and a Hi level emission is made from an IC 37 in the period from the capacitor 46 being zero till attainment of the specified voltage. A transistor 49 is turned on, and a switch 33 is put on by a photo-diode 51, and a high frequency power is supplied to the discharge tube 32. In this manner, the rise of a pulse width modulation signal is synchronized with the commercial AC electric supply.

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 rectifying commercial AC power, converting the rectified output to high frequency power by an inverter, and lighting the discharge lamp by the high frequency power. The present invention relates to a dimming device capable of performing on / off control of high-frequency power to be applied by a pulse width modulation signal to perform dimming.

[0002]

2. Description of the Related Art Conventionally, in a lighting device for lighting a discharge tube with high-frequency power, the brightness of the discharge tube is controlled, that is, dimming is performed.
As shown in Japanese Unexamined Patent Publication No. 8 "Vehicle fluorescent light control device", there is a saturable reactor system used for controlling a discharge lamp group, but this has poor controllability. There is a drawback that a large and heavy saturable reactor must be used. Therefore, as shown in the publication, a pulse width modulation signal is generated, the high frequency power applied to the discharge lamp is controlled to be turned on and off by the pulse width modulation signal, and the pulse width of the pulse width modulation signal is changed to adjust light, That is, the brightness is controlled by changing the average current flowing through the discharge tube.

[0003]

As described in the above publication, if the dimming is performed by the pulse width modulation signal, the dimming can be performed better than when the saturable reactor is used. However, as shown in the above publication, it is preferable to convert DC power to high frequency power by an inverter, but when rectifying commercial power and converting the rectified output to high frequency power by an inverter, flickering occurs and it is good. Dimming is not possible. As a result of exploring this reason, the amplitude of the high frequency power changes due to the envelope of the commercial AC power, and the flicker may occur due to interference between the change in the amplitude envelope of the high frequency power and the period of the pulse width modulation signal. found. In other words, the current flowing through the discharge tube is different even when the pulse width modulation signal has a large amplitude and where the high-frequency power has a large amplitude, and the portion that has a high amplitude has a high-frequency power envelope. Since it moved with respect to it, the brightness periodically changed and flickering occurred, and correct dimming could not be performed.

[0004]

According to the present invention, the rising edge of the pulse width modulation signal generator is synchronized with the phase of commercial AC power in the same cycle or every half cycle. Therefore, if the pulse width is constant, a high-frequency current of a magnitude corresponding to the width flows through the discharge tube, and the current flowing through the discharge tube does not change with the same pulse width, and good dimming is performed. .

According to the second aspect of the present invention, it is detected that a certain period of time has elapsed since the operation of the inverter was started and the high frequency power started to rise, and until the detection, the high frequency power for lighting the discharge tube was supplied. The switch means which is turned on / off by the pulse width modulation signal is held in the off state. However, when the high frequency power is generated irrespective of the switch means, the high frequency power is supplied to the heater of the discharge tube. That is, when the inverter starts operating, the heater of the discharge tube is preheated, and then high frequency power is supplied to the discharge tube.

According to the invention of claim 3, in addition to the main unit provided with the pulse width modulation signal generator, at least one unit not provided with the pulse width modulator is provided, and each switch means of the sub unit is the main unit. Controlled by a pulse width modulated signal from

[0007]

FIG. 1 shows an embodiment of the present invention. Commercial power supply 1
1 is supplied to the rectifier circuit 13 via the switch 12. This rectifier circuit 13 is a full-wave rectifier circuit, the output side of the rectifier circuit is supplied to the smoothing circuit 14, and the smoothing circuit 14 One end, one end 15 on the positive side in the figure, is connected to the midpoint of the primary winding 17 of the output transformer 16, and the other end 18, that is, the negative side is connected to both ends of the primary winding 17 through switching elements 19 and 21, respectively. To be done. A resonance capacitor 22 is connected between both ends of the primary winding 17. Further, the output of the smoothing circuit 14 is divided into a constant voltage by the Zener diode 23, and the constant voltage is made a constant bias voltage by the voltage dividing resistors 24 and 25, respectively, and the FETs 19 as switching elements, respectively. 21 is applied to the gate. Also, FE
The gates of T19 and T21 are connected to both ends of the feedback winding 26 of the transformer 16.

Both ends of the secondary winding 28 of the output transformer 16 are connected to one ends of both heaters of a discharge tube, for example, a fluorescent lamp 32, through a switch 33. Secondary winding 2
8'and 28 "are current limiting capacitors 29, 3 respectively
1 is connected to both ends of both heaters of the discharge tube 32.
An inverter 34 is configured by the FETs 19 and 21, the output transformer 16, the resonance capacitor 22, the bias supply voltage dividing resistors 24 and 25, and the like.

When power is applied to the inverter 34, F
Either one of ET19 and ET21 is turned on, a current flows through the turned-on FET, the primary winding 17,
A resonance current is generated in the resonance capacitor 22, and a voltage is generated in the feedback winding 26, and the output turns on the other FET and turns on the F.
When ET is turned off and a charging current flows so as to charge the capacitor 22 in the opposite direction, resonance occurs in the same manner, and thereafter, similarly, due to the voltage of the feedback winding 26, F is generated in a half cycle of the resonance current.
The ETs 19 and 21 are alternately turned on and off, the inverter 34 is oscillated, and high frequency power is obtained at the output transformer 16. The frequency of this high-frequency power is, for example, 20 kHz to 5
It is about 0 kHz.

Further, an IC 37 of an astable multivibrator is provided to perform a dimming action, and a winding 38 is further coupled to the transformer 16 for supplying power source power to the IC 37, and the output of the winding 38 is rectified. The voltage of the coil 38 is made constant by the constant voltage circuit 39, that is, the output of the winding 38 is supplied to a DC power supply 41 that converts it into a DC power, and the output of the DC power supply 41 is supplied as operating power of the IC 37. The positive output end of the DC power supply 41 is connected to the mover of the variable resistor 43 through the resistor 42, and the variable resistor 4
Both ends of 3 are diodes 44 and 4 of opposite polarities.
5 is connected to one end of the capacitor 46, and the other end of the capacitor 46 is connected to the negative side output end of the DC power supply 41. The connection point between the capacitor 46 and the diodes 44 and 45 is connected to the input side of the IC 37, the output side of the IC 37 is connected to the base of the transistor 49 through the resistor 48,
The collector of the transistor 49 is connected to the positive output terminal of the power supply 41 through the photodiode 51, and the emitter is connected to the negative output terminal of the power supply 41.

When the capacitor 46 is charged through the resistor 42, the variable resistor 43, and the diodes 44 and 45 and the voltage across the capacitor 46 becomes a constant voltage, the IC
The output of 37 falls. The electric charge of the capacitor 46 is discharged through the diode 44, the variable resistor 43, the resistor 42, and the IC 37. When the discharge ends, the output side of the IC 37 becomes high level. The sum of the charge time constant and the discharge time constant for the capacitor 46 is constant, and the time constant is changed by the variable resistor 43, and thus the variable resistor 4
By the setting of 3, a pulse whose pulse width is changed at a constant cycle, that is, a pulse width modulation signal is obtained at the output of the IC 37. This pulse width modulation signal causes the transistor 49
Is controlled to be turned on and off, and thus the photodiode 51
Lights up and flashes. The switch means 33 is on / off controlled by this light, that is, the switch means 33 is configured by an AC photoswitch element such as a photomos relay optically coupled to the photodiode 51. The high-frequency power supplied to the discharge lamp 32 is interrupted by turning on / off the switch means 33. If the pulse width of the pulse width modulation signal is increased, the average current flowing through the discharge lamp 32 is increased, and if it is decreased, the average current is decreased. The brightness of the discharge tube 32 can be brightened or darkened.

In the present invention, the pulse width modulation signal output from the IC 37 is synchronized with the commercial AC power. Therefore, both ends of the commercial power supply 11 are diodes 53 and 5, respectively.
4 is connected to one end of the resistor 55, and the other end of the resistor 55 is connected to one end of the full-wave rectifier circuit 13 through the light emitting diode 56. Further, a transistor 57 is connected between both ends of the capacitor 46, resistors 58 and 59 are connected in series between both ends of an output side of the DC power supply 41, and a resistor 58,
The connection point of 59 is connected to the base of the transistor 57. A phototransistor 61 is connected between the base and emitter of the transistor 57. Phototransistor 61
Constitutes a photo coupler with the photodiode 56.

Further, the discharge tube 32 is preheated for a certain period of time at the start of operating the inverter 34, and during that time, the discharge tube 32 is prevented from being discharged by the high frequency power. That is, the positive side end of the DC power supply 41 is connected to one end of the resistor 63 through the capacitor 62, and the other end of the resistor 63 is connected to the negative side of the DC power supply 41. The connection point between the capacitor 62 and the resistor 63 is connected to the base of the transistor 65 through the Zener diode 64, the collector of the transistor 65 is connected to the base of the transistor 49, and the emitter is connected to the emitter of the transistor 49. The diode 60 is connected in parallel with the resistor 63.

Due to this structure, as shown in FIG. 2A, when the switch 12 is turned on at time t ₁ and commercial power is supplied to the rectifier circuit 13, the inverter 34 operates as described above. As a result, high-frequency power is generated as shown in FIG. 2B, and the residual heat of the heater for the discharge tube 32 is started from the generation. When the output of the direct-current power supply 41 reaches a predetermined voltage due to the generation of this high-frequency power, the connection point between the capacitor 62 and the resistor 63 becomes a positive conductivity level through the diode 60, and the positive potential is the capacitor 6
2. The capacitor 63 is gradually discharged with the time constant of the resistor 63, but when the capacitor 62 is charged, the Zener diode 64
Are turned on, the transistor 65 is turned on, the transistor 49 is turned off, and thus the photodiode 5 is turned on.
When 1 is off and the switch means 33 is off, high frequency power is not applied across the discharge tube 32. However, depending on the time constants of the capacitor 62 and the resistor 63, for example, 0.5
After the remaining heat time of about 1 second, the condenser 62,
The potential of the resistor 63 becomes a predetermined value or less, the Zener diode 64 is turned off, the transistor 65 is turned off, the transistor 49 is turned on, light is emitted from the photodiode 51, and the switch means 33 is turned on.
As shown in FIG. 2C, the high frequency power is supplied to the discharge tube 32 at this time point t ₂ , and the discharge tube 32 is lit.

When the input commercial AC power has a waveform as shown in FIG. 2D, the diodes 53 and 54, the rectifying circuit 13
The commercial AC power is subjected to full-wave rectification, and a full-wave rectified output of the commercial AC power is obtained at the connection point of the resistor 55 and the photodiode 56 as shown in FIG. 2E. During most of the full-wave rectified output, the phototransistor 61 is turned on, and the phototransistor 61 is turned on only near the drop point of the full-wave rectified output, that is, near the zero crossing point of commercial AC power.
Is turned off, so only during that time a pulse is applied to the base of transistor 57 as shown in FIG.
Is discharged through the transistor 57. When the transistor 57 is turned off, the capacitor 46 is charged again, and the capacitor 46 is gradually charged as shown in FIG. 2G.
Voltage rises. Further, the output of the IC 37 becomes high level as shown in FIG. 2H, the transistor 49 is turned on, the switch means 33 is turned on, and high-frequency power is supplied to the discharge tube 32 as shown in FIG. 2I. When the voltage of the capacitor 46 reaches a predetermined voltage, the output of the IC 37 is
As shown by H, the level becomes low, the transistor 49 is turned off, the switch means 33 is turned off, and the discharge tube 3 is turned off.
The supply of high-frequency power to 2 is stopped. Capacitor 4
6 gradually discharges during that time, but before the discharge ends, the transistor 57 is turned on by the pulse generated at the next zero crossing point of the commercial frequency, the remaining charge is also discharged to the capacitor 46, and the output of the IC 37 becomes high again. It becomes a level.
That is, as shown in FIG. 2H, the output of the IC 37 rises at each 0 crossing point of the commercial AC power, and the capacitor 46
When becomes a predetermined level, the fall to the low level is repeated. The switching means 33 is turned on during the pulse width of the pulse width modulation signal, and the high frequency power shown in FIG. 2J generated in the inverter 34 is supplied to the discharge tube 32 as the high frequency power intermittently generated by the pulse width modulation signal as shown in FIG. 2I. Is applied. The section to which the high frequency power is supplied can be changed by adjusting the pulse width of the pulse width modulation signal, that is, by adjusting the variable resistor 43, and thereby controlling the brightness of the discharge tube 32. You can

As shown in FIG. 2J, the high frequency power does not have a constant amplitude but changes according to the waveform of the commercial AC power. Therefore, even if the switch means 33 is turned on with the same pulse width, the brightness of the discharge tube 32 varies depending on whether the switch means 33 is turned on in a large amplitude portion or in a small amplitude portion in FIG. 2J. , The pulse of the pulse width modulation signal is generated in synchronism with the commercial AC power, and thus is in synchronism with the envelope of the high frequency power, and if the pulse width is constant, a constant average current flows through the discharge tube 32. .

In the embodiment shown in FIG. 1, a plurality of discharge tubes are simultaneously turned on and dimming is controlled, and a dimming control part, a residual heat part, a DC power supply part, etc. are omitted.
If necessary, one or a plurality of sub-units 67 including the conventional rectifier circuit 13, smoothing circuit 14, inverter 34, output transformer 16 and the like are provided, and the input side of the full-wave rectifier circuit is connected to the commercial power supply 11. Light emitting elements 68 for controlling the switch means 33 provided on the secondary side of each output transformer 16 are respectively provided, and these light emitting elements 68 are a transistor 49 and a photodiode of a main unit 69 including a pulse width modulation signal generator. Connection lines 71 and 72 are connected between the connection point of 51 and the positive side of the DC power supply 41, respectively. In this way, in each sub-unit 67, high frequency power is generated by the inverter, and in a state where the high frequency power rises, the heater is preheated to the discharge tube 32, and the photodiode 68 is turned off during this period. Then, the switch means 33 is held in the off state, and when the residual heat is completed, the photodiode 68 is on / off controlled by the pulse width modulation signal, and the high frequency power is controlled by the pulse width modulation signal to be supplied to each discharge tube 32. To be done. Therefore, according to the brightness set by the resistor 43, each discharge tube 3 of the sub-unit 66.
The brightness of 2 is controlled similarly to the discharge tube 32 of the main unit 69.

[0018]

As described above, according to the present invention, since the pulse width modulation signal is generated in synchronization with the AC signal of the commercial power source, the desired dimming is performed without the brightness flickering. And stable illumination can be obtained. Further, the switch means provided for dimming is used to perform the residual heat at the time of startup, and therefore the life of the discharge tube can be extended as compared with the case where the preheating is not performed. Further, a plurality of sub-units are provided, only one of them is provided with a dimming control section and a residual heat control section, and the other is provided with only a control signal for controlling the switching means of the high frequency power to the main unit. The configuration can be simplified.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing waveforms of respective parts used to explain the operation of FIG.

Claims (6)

[Claims] 1. A pulse width modulation signal is generated in a dimming device of a discharge lamp lighting device, which rectifies commercial AC power, converts the rectified output into high frequency power by an inverter, and lights the discharge lamp by the high frequency power. Means for synchronizing the rising edge of the pulse width modulated signal with the commercial power, and switch means for opening and closing the high frequency power applied to the discharge lamp by the pulse width modulated signal. Dimming device for discharge lamp lighting device. 2. A means for detecting that a predetermined time has elapsed since the high frequency signal was generated after the inverter started to operate, and a control means for turning off the switch means until the detection means detects it. Means for supplying high-frequency power from the inverter to the heater of the discharge lamp without being affected by the switch means, and the adjusting means of the discharge lamp lighting device according to claim 1. Light equipment. 3. The commercial power is supplied, rectifies the commercial power, converts the rectified output into high frequency power by an inverter,
At least one sub unit for applying the high-frequency power to the discharge tube via the transformer and further via the switch means is provided, and each switch means of the unit is configured to be controlled by the pulse width modulation signal. The dimming device for a discharge lamp lighting device according to claim 1 or 2, characterized in that: 4. The means for generating the pulse width modulation signal comprises a variable astable multivibrator whose time constant circuit is controllable so that the charging time constant and the discharging time constant are opposite to each other at the same time, and the synchronizing means is provided. The discharge lamp according to any one of claims 1 to 3, characterized in that the discharge lamp comprises means for generating a pulse synchronized with the commercial AC power, and means for discharging the electric charge of the time constant circuit with the pulse. Lighting device dimming device. 5. The means for generating the pulse comprises a circuit for full-wave rectifying the commercial AC power, and means for generating the pulse when the full-wave rectified output is dropped. 4. The dimming device for the discharge lamp lighting device according to 4. 6. The direct-current circuit for rectifying and smoothing the output of the inverter to output a constant voltage, and the constant-voltage instantaneously when the constant voltage appears from the direct-current circuit 3. A circuit for charging a capacitor and gradually discharging the electric charge of the capacitor, and means for generating an off control signal to the switch means when the voltage of the capacitor is a predetermined voltage or higher.
A dimming device for the discharge lamp illuminator described.