JPS584440B2 - Discharge lamp lighting method - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a lighting method for a discharge lamp equipped with an inverter,
This is designed to compensate for the light output immediately after the discharge lamp is lit, so that a constant light output can be obtained while the discharge lamp is lit.

After lighting, the light output of a discharge lamp gradually increases and reaches a certain level after several minutes.

Therefore, until this level is reached, the optical output is small and fluctuates gradually.

For this reason, when used as a light source device for electronic transmission equipment such as a facsimile, it is often inappropriate to use it for several minutes immediately after it is turned on.

A solution to this problem would be to keep the lights on continuously, but the power loss would be large and this would be uneconomical.

Although it is also possible to feed back the optical output to obtain a constant output, the configuration is complicated and increases the cost.

The present invention is a discharge lamp lighting method that solves these drawbacks at once.The inverter output is connected to the discharge lamp through a capacitor (or inductor), and after the discharge lamp is lit, the oscillation frequency of the inverter gradually decreases. It is set to fall (or rise) and settle to a predetermined value, thereby compensating for the light output immediately after the discharge lamp is lit, and during lighting,
It is designed to obtain a constant light output.

Therefore, it has the feature that it can be used immediately after lighting, and since it only requires adding a circuit for changing the oscillation frequency of the inverter over time after lighting, the configuration does not become large-scale and the increase in cost can be kept to a minimum.

An example of an implementation circuit will be described below.

In Figure 1, resistors R1, R2 and capacitor C0
A time constant circuit consisting of Darlington-connected transistors TR, , TR2K provides base bias,
A light output is obtained from a light emitting element LED driven by the output current.

Resistor R3 is used for current limiting.

The light emitting element LED is optically coupled to the light receiving element Cds,
The resistance value of this light receiving element Cds changes depending on the optical output.

Light receiving element Cds, resistor R4 to R6A capacitor C2, N
AND gates IC1 and IC2 constitute an oscillation circuit using an astable multivibrator A, and the light receiving element Cd
The oscillation frequency is set by the resistance value of s.

The output of this astable multivibrator A is NAND gate IC3, IC4, capacitor C3, C4 and resistor R.
7, R8 is connected to a T flip-flop B.

Since this T flip-flop B repeats the inversion operation every cycle of the astable multivibrator A, a perfectly symmetrical square wave with a duty ratio of 50:50 is obtained.

This output is inverted by NAND gate IC5 and passed through resistor R10 to Darlington L transistors TR5, TR.
Join 6.

Also, the other Darlington transistor TR3, T
R4 is a NAN that inverts the output of NAND gate IC5.
The output of the D gate C6 is given through the resistor R.

The above two Darlington transistors and output transformer T
A push-pull inverter C is configured, which switches a DC power source to convert it into AC, and adds the output to the discharge lamp.

CH is a choke coil, capacitor C5 is for waveform shaping,
Capacitor C6 is a ballast.

Next, the operation will be explained with reference to FIGS. 2 and 3.

When DC power is applied to the circuit, a large base current is supplied to the transistor TR1 by the charging current of the capacitor C1, and the collector current of the transistor TR2 also becomes a large value. The resistance value of becomes smaller.

This is as shown in Figure 2 1. As time passes, charging of the capacitor C1 progresses and the light output of the light emitting element LED becomes weaker, so the resistance value of the light receiving element Cds increases and approaches a predetermined value. .

Such a change in the resistance value of the light receiving element Cds gradually lowers the oscillation frequency of the astable multivibrator A (FIG. 2).

Figure 3a shows the oscillation waveform of Paco's multivibrator A.

Furthermore, b is the output waveform of T flip-flop B, and c and d are the output waveforms of NAND gate IC and IC6, respectively.

After such waveform conversion, the Darlington transistors TR3, TR4 and TR5, TR6 are alternately switched, and the output waveform of the output transformer T becomes approximately a sine wave as shown in e.

As mentioned above, the oscillation frequency is high immediately after lighting, and gradually decreases to a predetermined value, so the impedance value of the ballast capacitor C6 also changes, and a large lighting current is supplied to the discharge lamp immediately after lighting. , gradually settles down to a predetermined value.

Therefore, the light output of the discharge lamp L immediately after lighting can be compensated for, and a substantially constant light output can be obtained over time.

FIG. 4 shows this, where A is the conventional light output and A is the light output of the present invention.

Further, as another embodiment of the present invention, an inductor may be used as a ballast instead of the ballast capacitor C6, and the oscillation frequency may be lowered immediately after lighting and then gradually increased.

At this time, the capacitor C1 may be connected in parallel to the resistor R2.

Although only an example in which a time constant circuit and an oscillation circuit are optically coupled is shown, if a voltage-controlled oscillation circuit known before the filing of this application is used, the output voltage of the time constant circuit (terminal voltage of resistor R3 can be used). If you connect directly to the voltage control input terminal of this oscillation circuit, you can obtain the same effect, etc.
The means for coupling the time constant circuit and the oscillation circuit can be implemented as desired and is not limited to the embodiments shown in the drawings of the present application.

As described above, according to the discharge lamp lighting method of the present invention, the light output of the discharge lamp immediately after lighting can be compensated and become almost constant over time, so it can be used immediately after lighting, and it can be used for electronic transmission equipment such as facsimiles. It is extremely useful in
In addition, it is more economical than conventional continuous lighting, and requires only a simple additional circuit, so cost increases can be kept to a minimum.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the discharge lamp lighting method of the present invention, Fig. 2 1 is a resistance value change characteristic diagram of Cds, Fig. 2 is an oscillation frequency change characteristic diagram of multiviprator A, and Fig. 3 is a FIG. 1 is a waveform diagram of key points of the circuit, and FIG. 4 is a diagram of the temporal change characteristics of the optical output. A... Astable multivibrator, B...
...T flip-flop, C...inverter,
T... Output transformer, TR1 to TR6...
・・Transistor, IC1~IC6・・・・・・NAN
D gate, LED... light emitting element, Cds...
... Light receiving element, L ... Discharge lamp, R1 ~ R1
o...Resistor, C1-C6...Capacitor, CH...Choke coil.

Claims (1)

[Claims] 1. A time constant circuit, an oscillation circuit whose oscillation frequency decreases (or increases) by being coupled with the time-varying control output of this time constant circuit, an inverter driven by this oscillation circuit, and a capacitor to which the output of this inverter is connected in series. A discharge lamp lighting method characterized by comprising a discharge lamp connected through an inductor (or an inductor).