JPH02215091A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To surely prevent a lighting miss even if circuit components have capacity dispersion and require no adjustment for the resonance frequency at the time of manufacture by sweeping the frequency of the applied voltage near the resonance frequency when a discharge lamp is started. CONSTITUTION:The frequency generated by an inverter circuit 3 is automatically swept around the resonance frequency f0 (preset value) by a control means 6. This sweep width is set to about + or -5% of the resonance frequency f0, for example. When the resonance frequency is swept around the preset value, the voltage with the actual resonance frequency f0 can be surely applied even if the actual resonance frequency is somewhat drifted, and the high voltage required for dielectric breakdown can be generated. A discharge lamp can be surely lighted regardless of some capacity dispersion of circuit components, and no adjustment is required at the time of manufacture.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lighting device for a discharge lamp filled with metal vapor, such as a mercury lamp or a sodium lamp, and particularly relates to an instantaneous lighting technique.

[Prior art]

Conventional discharge lamp lighting devices include 1, for example, "Lighting Handbook, 1st Edition, 1st Printing, May 20, 1980, Published by Ohmsha, pp. 198-201" and "Electrical Engineering Handbook, 1st Edition, 1982. Published by the Institute of Electrical Engineers of Japan, April 10th,
Some are described in pp 1539-1541J.

FIG. 4 is a diagram showing an example of the conventional discharge lamp lighting device as described above.

In FIG. 4, reference numeral 10 denotes an AC power supply serving as an energy supply source, 11 an inverter circuit that converts the voltage 10 of the AC power supply into a high voltage of a predetermined frequency (for example, about several hundred V), and 14
is a discharge lamp. Further, the choke coil 12 and the capacitor 13 constitute an LC series resonant circuit.

In the above device, at the start of lighting, the resonant frequency (100k
When power is supplied (approximately Hz), series resonance causes 1
A high voltage of about 0kV is generated, which causes the discharge lamp 14
Dielectric breakdown of the gas filled in the chamber occurs. At this time, the gas temperature is low, so the resistance value is small, and at the same time as the insulation breaks down, a current of about IA flows and the lamp is lit. After that, the resistance value increases as the gas temperature rises, so the current value gradually decreases, and when the gas temperature reaches a stable state, the current decreases to 0.
It becomes saturated at about 4 to 0.5 A, reaches a desired amount of light, and enters a stable discharge state.

Note that after the first light is turned on, the choke coil 12 operates as a ballast.

When used as a headlamp for a vehicle, the discharge lamp described above has many advantages over current filament type bulbs in terms of small size, light weight, and high efficiency.

[Problem to be solved by the invention]

However, in the conventional discharge lamp lighting device as described above, the frequency of the AC power output from the inverter circuit at the start of one lighting operation is fixed to a constant value, and therefore the series resonant circuit is affected by variations in the capacitance of the choke coil 12 and capacitor 13. If the resonant frequency deviates from the design value, the generated voltage will drop below the design value, and as a result, it may not be possible to reliably light the lamp.Additionally, the resonant frequency must be adjusted for each lighting device after manufacturing. Therefore, there was also the problem of high costs.

The present invention has been made to solve the problems of the prior art as described above, and is a light source that can reliably light up regardless of slight variations in the capacity of one circuit component, and that does not require adjustment during manufacturing. The purpose is to provide an electric light lighting device.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as described in the claims.

That is, in the present invention, by configuring the frequency of the inverter circuit to automatically sweep before and after the resonant frequency of the LC series resonant circuit at the start of lighting, the resonant frequency of the resonant circuit can be changed from the design value due to variations in one component. Even if there is a deviation, the necessary high voltage can be reliably generated.

〔Example〕

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

In FIG. 1, 1 is an AC power supply serving as an energy supply source, and 2 is a full-wave rectifier circuit, which outputs, for example, 300 V DC. In addition, in the case of a DC power source such as a vehicle, DC-
Using a DC converter to convert the 12V of the car battery to 3 DC
Convert to 00v.

Further, 3 is an inverter circuit that converts the above-mentioned DC power into AC power of a predetermined frequency, 4 is an LC series resonant circuit consisting of a choke coil L and capacitors C, , C, and 5 is a discharge lamp. Further, 6 is a control means for controlling the frequency of the inverter circuit 3.

It consists of a dedicated analog or digital circuit, a microcomputer, etc. Note that the resistor R connected in series with the discharge lamp 5 is for detecting the current flowing through the discharge lamp 5 as a voltage value VR, and the capacitor is divided into C1 and 02 for 1. This is to detect the generated voltage as the voltage Vc at the connection point between both capacitors.

Next, one effect will be explained.

When lighting starts (starting up), the LC is connected from the inverter circuit 3.
Resonant frequency of series resonant circuit 'HI4 (about Hz)
A high voltage of approximately 10 kV generated by series resonance is applied to the discharge lamp 5 to cause dielectric breakdown of the filled gas. However, due to variations in the circuit components, the above resonance frequency deviates from the design value. There is a risk that the high voltage required for dielectric breakdown may not be obtained. Therefore, in the present invention, the control means 6 is used to automatically sweep the frequency generated by the inverter circuit 3 around the resonance frequency f (design value). The above sweep width is
For example, it is set to about ±5% of the resonance frequency f0.

Therefore, when the design value f0 of the resonance frequency is 100k)lz, the range of 95 to 105kHz is sequentially swept.

If you sweep the resonant frequency before and after including the design value as described above, even if the actual resonant frequency is slightly off,
It is possible to reliably apply a voltage at the actual resonant frequency,
It can generate the high voltage necessary for dielectric breakdown.

This will be explained in detail below.

FIG. 2 is a flowchart showing the calculation contents of the control means 6;
FIG. 3 is a signal waveform diagram of the control means 6.

In Fig. 2, first, at P, it is determined whether the light switch (not shown in Fig. 1) that operates the discharge lamp to blink is on or not, and if it is on, the process goes to P2, and the start timing waveform is Turn on. This starting timing waveform is, for example, as shown in FIG. 3(a), and when this waveform is on (high level), automatic sweeping of the resonance frequency is performed.

Next, in P, the number of times n of one frequency switching is set to 1, and the frequency addition value 5TEP is set to 0. For example, the design value of the resonance frequency f, (f, = 1/(2πf)) is set to 1oOkHz.
When sweeping a range of ±5%, the frequency sweep range is 95 to 105 kHz. If this sweep range, that is, the 10 kHz width, is to be switched stepwise, for example, 10 times, the value 5TEP added every - time will be 1 to 7.

Finally, in P4, it is judged and determined whether the number of times n of one frequency switching has reached 10, and if it has not reached 10, the process goes to P.

In P, let the value of the output frequency f0 be f, +5TEP
Set to . In the first case (n=1), 5TEP=O, so 1 frequency is the initial value (95kHz in the above example)
becomes.

Next, in P6, the terminal voltage Vc of the capacitor or the terminal voltage VR of the resistor is read.

Next, in P7, the above-mentioned read value is compared with a predetermined voltage v11 set in advance. The above read value, for example V
The value of c is high when the gas filled in the discharge lamp 5 is in an insulating state. If the edge is destroyed, the value will be low (VF
Conversely, I is O during insulation.

(becomes larger after dielectric breakdown), by comparing this value with a predetermined value V, it is possible to determine whether or not dielectric breakdown has occurred.

If No in P7, that is, if dielectric breakdown has not occurred, in P8, set the frequency switching frequency n to n+1 and the frequency addition value 5TEP to 5TEP+1, and then return to P.
Repeat the above calculation process.

Therefore, each time the above loop is repeated, the frequency is added by 1k)Iz. If no dielectric breakdown occurs even after repeating the process 10 times in total, the process returns from P4 to PE.

That is, the control means 6, as shown in FIG. 3(b),
A rectangular wave signal whose initial frequency is 95 kHz and whose frequency increases by 1 kHz each time is sent to the inverter circuit 3 until dielectric breakdown occurs (up to 10 times). The inverter circuit 3 generates an alternating current voltage having the same frequency as the rectangular wave signal, and applies it to the discharge lamp via the LC series resonant circuit 4. Note that FIG. 3(c) is a diagram showing the frequency sweep range mentioned above.

Next, if YES in P7, that is, if dielectric breakdown has occurred, go to P and turn off the starting timing waveform. This stops automatic frequency sweeping.

Next, at P, ll, the frequency of the output signal of the control means 6 (input of the inverter circuit 3) is set to a predetermined frequency after dielectric breakdown (
For example, set it to 4 kHz).

Immediately after dielectric breakdown, the gas temperature is low, so the resistance value is small;
Therefore, if the frequency is set to a predetermined value as shown above,
At the same time as the insulation breaks down, a large current of 2 to 3 A flows and lights up.

Next, pi reads the terminal voltage Vn of the resistor or the terminal voltage Vc of the capacitor.

Next, in pL, it is determined whether or not the discharge lamp is lit by comparing the above-mentioned read value with a predetermined value. In other words, if the discharge lamp is lit and current flows, the terminal voltage VR of the resistor will show a value, and lighting can be detected based on this value.

If it is determined that "lighting is on" in P or Y, the process moves to the first control. In this control, for example, the frequency is set to a steady value of 10 kHz. When controlled in this way, the resistance value increases as the gas temperature rises, so the current value gradually decreases, and when the gas temperature reaches a stable state, the current value is 0.4
It reaches a saturation state at about 0.5 A and becomes a stable discharge state.

On the other hand, if pi2 determines that it is not lit.

Return to "START" and repeat the ignition control described above.

〔Effect of the invention〕

As explained above, according to the present invention, the frequency of the applied voltage is swept around the resonant frequency when starting the discharge lamp, so the capacitance of the coil and capacitor that are circuit components of the resonant circuit is Even if there are variations in the resonance frequency due to variations, a voltage that causes dielectric breakdown can be reliably applied to the discharge lamp. Therefore, it is possible to reliably prevent lighting errors due to variations in circuit components, and there is no need to adjust the resonant frequency for each lighting device during manufacturing, so costs can be reduced.

In addition, excellent effects such as timing control for lighting a plurality of discharge lamps at the same time become possible can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a flowchart showing an embodiment of the calculation process of the present invention, Fig. 3 is a signal waveform diagram of an embodiment of the present invention, and Fig. 4 is a conventional example. FIG. <Explanation of symbols> 1...AC power source 2...Full wave rectifier 3...Inverter circuit 4...LC resonant circuit 5...Discharge lamp 6...Control means 10...AC power source 11 ... Inverter circuit 12 ... Choke coil 13 ... Capacitor 14 ... Discharge lamp

Claims (1)

[Claims] By connecting a discharge lamp in parallel with the capacitor of a series circuit consisting of a choke coil and a capacitor, and applying AC power at the resonant frequency of the series circuit to the series circuit from an inverter circuit, the circuit is generated as a series resonant circuit. In a discharge lamp lighting device that applies a high voltage to the discharge lamp to cause dielectric breakdown in the discharge lamp at the time of starting lighting, the frequency of AC power generated by the inverter circuit is set to the resonance frequency of the series circuit at the time of starting lighting. A discharge lamp lighting device characterized by comprising means for automatically sweeping in a predetermined range including.