JPH04138696A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To stabilize an arc so as to prevent flickering of a discharge lamp by modulating the frequency of a current supplied from an inverter portion so as to make the lamp current of the discharge lamp constant. CONSTITUTION:A PWM signal generating portion 8 generates a PWM signal of modulation factor corresponding to that of a lamp current detection signal of a discharge lamp 9 output from an output fluctuating element detecting portion 6. When a lamp current is below a set value the output of a high- efficiency smoothing portion 2 is increased and current supplied from an inverter portion 4 is raised so as to return the lamp current to the set value and maintain it at a fixed value. When a lamp current supplied from the inverter portion 4 is raised to above a set value by the switching frequency of an FM signal generating portion 3 the output fluctuating element detecting portion 6 and the PWM signal generating portion 8 are similarly actuated to lower the current from the inverter 4 and return it to the set value. Thereby an arc in the discharge lamp is stabilized to prevent flickering and extinction of the arc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a high-intensity discharge lamp.

(Prior Art) A device shown in FIG. 3 is conventionally known as a discharge lamp lighting device for lighting a discharge lamp of a high-intensity discharge lamp.

The discharge lamp lighting device shown in this figure is a power source 101 such as a commercial power source.
a rectifying section 102 that rectifies the AC voltage supplied from the rectifying section 102, a smoothing section 103 that smoothes the voltage obtained by the rectifying section 102, an FM section 104 that generates a switching signal of a specified frequency, and this FM section 104. An inverter unit 105 converts the voltage output from the smoothing unit 103 into an AC voltage based on a switching signal output from the inverter #105, and a discharge lamp (for example, , HID lamp) 10
7 and a current limiter 106 for lighting the current.

By periodically changing the frequency of the switching signal output from the FM section 104, the acoustic resonance that occurs when the discharge lamp 107, such as an HID lamp, is driven at a specific frequency is prevented, and arc fluctuations are prevented. Discharge lamp 107 while avoiding problems such as bending and extinguishing.
Lights up and drives.

(Problem to be Solved by the Invention) However, in the conventional discharge lamp lighting device described above, since an impedance element such as a coil is used in the current limiting section 108, the oscillation frequency of the SFM section 104 is changed and the inverter section 105 When changing the frequency of the voltage output from the FM section 10, due to the frequency dependence of the current limiting section 106,
As shown in FIG. 4, the lamp current fluctuates depending on the oscillation frequency of the discharge lamp 107, which causes the brightness of the discharge lamp 107 to change, causing flickering or turning off the lamp.

In view of the above circumstances, the present invention makes it possible to make the lamp current flowing through the discharge lamp constant even if the current output from the inverter section is frequency-modulated, thereby stabilizing the arc within the discharge lamp and eliminating flickering. It is an object of the present invention to provide a discharge lamp lighting device that can prevent the discharge lamp from turning off and turning off the discharge lamp.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a discharge lamp lighting device according to the present invention includes a high-frequency generator that converts the output from a DC power source into a high-frequency voltage to energize the discharge lamp, and a frequency control section that periodically changes the output frequency of the high-frequency generator; a detection section that detects the lamp current value of the discharge lamp; and a frequency control section that detects the lamp current value of the discharge lamp; The present invention is characterized by comprising a voltage regulator that controls the output from the DC power supply to maintain the value of the lamp current at a substantially constant value.

(Function) In the above configuration, the voltage adjustment section operates based on the value of the lamp current detected by the detection section to control the voltage value of the AC voltage supplied to the discharge lamp, thereby keeping the value of the lamp current constant. hold at the value of .

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a discharge lamp lighting device according to the present invention.

The discharge lamp lighting device shown in this figure includes a rectifying section 1, a high power factor smoothing section 2, an FM signal generating section 3, an inverter section 4, a current limiting section 5, an output fluctuation element detecting section 6, and an auxiliary power source. Part 7 and P
The FM signal generating section 8 is equipped with a FM signal generating section 8, which causes the FM signal generating section 3 to carry out FM modulation operation to constantly change the frequency of the switching signal outputted from the FM signal generating section 3 while detecting the lamp current and keeping it constant. The discharge lamp 9 is turned on by adjusting the voltage value output from the high power factor smoothing section 2 so that the voltage value becomes .

The rectifier 1 includes a rectifying element 11 and the like, and rectifies an AC voltage supplied from a power source 10 such as a commercial power source to convert it into a DC voltage (
pulsating current voltage) and supplies it to the high power factor smoothing section 2.

The high power factor smoothing section 2 includes a coil 12 that receives the DC voltage supplied from the rectifying section 1 and a DC voltage supplied via the coil 12 based on the PWM signal supplied from the PWM signal generating section 8. Chopping transistor 1
3, a diode 14 that passes the pulse voltage obtained by this transistor 13, and this diode 14.
capacitor 1 charged by a pulsed voltage passed through
Based on the PWM signal supplied from the PWM signal generation section 8, the DC voltage supplied from the rectification section 16) is smoothed with a high power factor to a level corresponding to the PWM signal. generates a DC voltage and sends it to the inverter section 4.
supply to.

Furthermore, the FM signal generating section 3 is equipped with an oscillating IC element, etc., and oscillates while constantly changing the frequency based on conditions for avoiding acoustic resonance, and generates a switching signal obtained by this oscillation operation. is supplied to the inverter section 4.

The inverter section 4 includes two transistors 16.17 and two diodes 18.1, which are turned on and off alternately according to the switching signal supplied from the FM signal generation section 3.
9 etc., converts the DC voltage supplied from the high power factor smoothing section 2 into an AC voltage according to the switching signal supplied from the FM signal generation section 3, and supplies this to the current limiting section 5. supply

The current limiter 5 includes a coil 20 for limiting the current value, etc.
The AC voltage supplied from the inverter section 4 is taken in and supplied to the discharge lamp 9 serving as a load while limiting its current value.

Further, the output fluctuation element detection section 6 is equipped with a resistor for detecting a current value, etc., and detects the current value (lamp current value) of the AC voltage output from the current limiting section 5 and transmits it to the PWM signal signal section. Students will receive 8 stipends.

Further, the auxiliary power supply unit 7 includes a diode bridge circuit 21 that performs full-wave rectification of the AC voltage supplied from the power supply 10, and a capacitor 22 that smoothes the DC voltage output from the diode bridge circuit 21. The AC voltage supplied from the power supply 10 is converted into a DC voltage and supplied to the PWM signal generating section 8.

PWM signal signal generator part 8 An oscillation circuit that oscillates at a set frequency and a signal output from this oscillation circuit are
It is equipped with a modulation circuit that performs M modulation, operates based on the DC voltage supplied from the auxiliary power supply section 7, and performs PWM modulation based on the current value detection signal supplied from the output fluctuation element detection section 6. A PWM signal is generated and supplied to the high power factor smoothing section 2 to control the value of the DC voltage output from the high power factor smoothing section 2.

Next, the operation of this embodiment will be explained with reference to the waveform diagram shown in FIG.

First, the FM signal generator 3 operates to generate a switching signal whose frequency constantly changes within a frequency range according to the preset conditions as shown in FIG. 2(a), and outputs it from the inverter 4. The frequency of the alternating current voltage is changed, and the discharge lamp 9 is lit by the alternating current voltage output from the current limiting section 5.

In parallel with this operation, the lamp current value of the discharge lamp 9 is detected by the output fluctuation element detection section 6, and a current value detection signal corresponding to the detection result is generated, and this is sent to the PWM signal signal generation section 8. be done.

If the value of the lamp current of the discharge lamp 9 outputted from the current limiter @1l15 falls from a preset value, PWM The signal generating section 8 detects the current value, generates a PWM signal with a modulation degree corresponding to the current value as shown in FIG. 2(b), and outputs it from the high efficiency smoothing section 2 as shown in FIG. 2(c). By increasing the value of the output DC voltage, the voltage value of the AC voltage output from the inverter section 4 is increased as shown in FIG. 2(d), and the voltage flows to the discharge lamp 9 as shown in FIG. 2(e). The value of the lamp current is returned to a preset value and held at a constant value.

Furthermore, when the frequency of the switching signal outputted from the FM signal generation section 3 is changed to change the frequency of the AC voltage outputted from the inverter section 4, the lamp current flowing in the discharge lamp 9 increases and If the value exceeds the set value, the PWM signal generator 8 detects the current value based on the current value detection signal outputted from the output fluctuation element detector 6, and generates a PWM signal with a modulation degree corresponding to the current value. is generated to lower the value of the DC voltage output from the high-efficiency smoothing section 2, thereby decreasing the voltage value of the AC voltage output from the inverter section 4, thereby presetting the value of the lamp current flowing through the discharge lamp 9. Return to the set value and keep it at a constant value.

In this way, in this embodiment, the degree of modulation of the PWM signal outputted from the PWM signal generating section 8 is controlled according to the value of the lamp current flowing in the discharge lamp 9, and the modulation degree of the PWM signal outputted from the high efficiency smoothing section 2 is outputted from the high efficiency smoothing section 2. Since the value of the DC voltage is controlled and thereby the value of the AC voltage supplied to the discharge lamp 9 is adjusted to maintain the value of the lamp current supplied to the discharge lamp 9 at a constant value, the inverter section Even if the voltage output from the discharge lamp 4 is modulated in frequency, the lamp current supplied to the discharge lamp 9 can be kept constant, thereby stabilizing the arc within the discharge lamp 9 and preventing flickering and It is possible to prevent the lights from turning off.

〔Effect of the invention〕

As described above, according to the present invention, even if the current output from the inverter section is frequency-modulated, the lamp current flowing through the discharge lamp can be made constant.

This stabilizes the arc within the discharge lamp and prevents flickering and turning off the discharge lamp.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a discharge lamp lighting device according to the present invention, and FIG. 2 is a waveform diagram showing an example of the operation of the embodiment.
Fig. 3 is a block diagram showing an example of a conventionally known discharge lamp lighting device, and Fig. 4 is a waveform diagram showing an example of lamp current of a discharge lamp driven to be lit by the discharge lamp lighting device shown in Fig. 3. be. 2... DC type M (high power factor smoothing section) 3... Frequency control section (FM signal generation section) 4... High frequency generator 5... Current limiting section 6... Detection section (output fluctuation Element detection section) 8... Voltage adjustment section (PWM signal generation section) 9... Discharge lamp

Claims (1)

[Claims] (1) A high-frequency generator that converts the output from a DC power supply into a high-frequency voltage to energize the discharge lamp, a frequency control unit that periodically changes the output frequency of the high-frequency generator, and a lamp current of the discharge lamp. a detection unit that detects the value of the lamp current; and a detection unit that controls the output from the DC power supply supplied to the high frequency generator based on the lamp current value detected by the detection unit to maintain the value of the lamp current at a substantially constant value. A discharge lamp lighting device characterized by comprising: a voltage adjustment unit that maintains the voltage at a certain value;