JPH081840B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device using frequency modulation means to eliminate arc instability due to an acoustic resonance phenomenon in high frequency lighting of a high pressure discharge lamp. is there.

[Background technology]

Generally, it is desired to reduce the size, weight, and loss of the discharge lamp lighting device, but in the case of the conventional general discharge lamp lighting device, since it is a single yoke coil, a transformer, a capacitor, or the like, the dimensions, Since the weight of the discharge lamp itself is large and the discharge lamp itself is smaller than the fluorescent lamp in comparison with the fluorescent lamp, there is a problem that the storage space cannot be taken when the lighting device is built into the lighting device.

In recent years, for fluorescent lamps, high-frequency lighting devices using switching transistors and the like have been put into practical use in order to reduce the size, weight, and loss of the lighting device and to improve the luminous efficiency. This high-frequency lighting device has the same effect as a fluorescent lamp when applied to a high-pressure discharge lamp, and is expected to be put into practical use.
Instability of the arc (fluctuation, extinguishing, destruction of the arc tube, etc.) due to acoustic resonance during high-frequency lighting of the high-pressure discharge lamp
Is conventionally known to exist, and frequency modulation is one of the preventive measures.

FIG. 4 (a) is a conventional high voltage discharge lamp lighting device using frequency modulation, (1) is an AC power supply, and a full-wave rectifier (2).
Is rectified by driving the high frequency inverter section (3) to light the discharge lamp (4) at a high frequency. (5) is a control unit, which comprises an FM oscillator circuit (6) and a drive circuit (7). The FM oscillator circuit (6) is an FM signal generator circuit (8) and a timer IC.
(9) and the drive circuit (7) is D-FF (1
0), NAND gate (11), (12), NOT gate (13),
(14) and the base drive circuit (15). In this case, the frequency changes with time and the reactance of the source impedance L ₁ changes, and the lamp current Ila becomes as shown in FIG. 4 (b). Lamp current Ila
The ripple cycle corresponds to the FM cycle by the FM oscillator circuit (6). In Figure 4 (a), the timer IC
(9) receives the FM signal at the control voltage terminal 5, changes the threshold value of the voltage of the capacitor C ₂ and outputs a short-wave FM oscillation output to the output terminal 3. When the output of the output terminal 3 is at the H level, it is the period in which the capacitor C ₂ is being charged by the closed circuit of R ₁ -R ₂ -C ₂ , and when Vc ₂ reaches the upper threshold value, the capacitor C ₂ charge, C ₂ -R ₂ - is discharged in the closed circuit terminal 7 terminal 1, the output of the output terminal 3 this time is L level. When Vc ₂ reaches the lower threshold, it becomes a closed circuit of R ₁ −R ₂ −C ₂ . The upper limit threshold is 2 / 3Vcc and the lower limit threshold is 1 / 3Vcc, but since the FM signal is input to the control voltage terminal 5, the threshold value changes in response to this voltage and the output The frequency modulation is applied to the output of the terminal 3. The drive circuit (7) receives this signal and D-FF (10)
Etc. to generate a drive signal. Here, it becomes half the frequency of the signal received from the FM oscillator circuit (6). That is, 1/2 of the input signal frequency becomes the frequency of the high frequency inverter section (3), the high frequency inverter section (3) is driven by the base drive circuit (15), and the discharge lamp (4) is frequency-modulated.
Turn on the high frequency. For this, the discharge lamp (4)
Instability of the arc due to the acoustic resonance phenomenon is reduced and eliminated, but the lamp current waveform is as shown in Fig. 4 (b), so the luminous flux of the discharge lamp (4) changes and it is suitable for applications such as copying machines. On the other hand, uneven light becomes a problem, and if the frequency modulation period is long, it is felt as flicker in the eyes.In addition, the instantaneous value of the lamp current changes drastically and the crest factor increases, which adversely affects the lamp life. Moreover, it has a drawback of increasing noise.

[Object of the Invention]

An object of the present invention is to reduce the change in the instantaneous value of the lamp current even if the frequency is modulated, and suppress the change in the luminous flux to eliminate the flicker.

[Disclosure of Invention]

Example In FIG. 1 (a), (1) is an AC power supply, which is rectified by a full-wave rectifier (2), drives a high frequency inverter section (3) through a voltage variable section (16), and frequency-modulates it. Turn on the discharge lamp (4). The voltage variable section (16) controls the voltage of the high frequency inverter section (3) and suppresses an instantaneous change of the lamp current due to frequency modulation, and the voltage control circuit (18) provided in the control circuit (17). Controlled by.
(6) is an FM oscillator circuit similar to the conventional example of FIG. 4 (a), and (7) is a drive circuit. The voltage variable by the voltage variable unit (16) is synchronized with the frequency modulation of the high frequency inverter unit (3). For example, in the case of inductive current limiting impedance L ₁ , when the lighting frequency becomes higher, it tends to make it difficult for the lamp current to flow, but the voltage variable unit (16) increases the voltage to the high frequency inverter unit (3) to increase the lamp current. The current is controlled so that the values are almost the same.

FIG. 2 (a) shows a voltage variable section (16) and a voltage control circuit (1
8), the FM oscillator circuit (6), and the drive circuit (7) in the specific circuit diagram, in which a voltage booster circuit is used as the voltage variable unit (16). (19) is a flip-flop, (20)
Is a duty setting circuit, which consists of a timer IC (21),
The timer IC (21) is composed of comparators (22), (23), a flip-flop (24) and an output stage (25) as shown in FIG. 2 (b).

When the transistor to Q ₁ operating voltage varying unit (16) is turned on by the output of the base drive circuit (26), a current flows through the inductance L _0, energy stored in the inductance L ₀ at this time the transistor Q ₁ is When turned off, L ₀ −
It is discharged in the circuit of D ₁ -C ₀ , and the capacitor C ₀ is charged.
The voltage of the capacitor C ₀ changes depending on the ON period of the transistor Q ₁ , the duty factor, and the switching frequency. In this embodiment, the switching frequency of the transistor Q ₁ is changed with the ON period kept constant to control the voltage of the capacitor C ₀ . The switching frequency of the transistor Q ₁ is set by the FM oscillator circuit (6) and the flip-flop (19), and the ON period is decided by the timer IC (21).
This ON period is fixed. Since the current limiting impedance is inductive, it becomes difficult for the lamp current to flow when the frequency of the high frequency inverter section (3) becomes high, but the voltage of the capacitor C ₀ changes to compensate for the decrease of the lamp current due to the operation of the transistor Q _1. However, the instantaneous change of the lamp current Ila can be suppressed as shown in FIG.

Next, the fact that the voltage of the capacitor C ₀ increases as the switching frequency of the transistor Q ₁ increases will be briefly described. Since the ON period of the transistor Q ₁ is constant, the OFF period becomes shorter as the switching frequency becomes higher. That is, as the on-duty increases, the energy stored in the inductance L ₀ increases, the charge amount to the capacitor C ₀ increases, the voltage increases, and the lamp current increases. The voltage of the capacitor C ₀ is determined by the balance between the energy input from the inductance L _0, the voltage of the capacitor C ₀ , and the lamp power. Flip Flop (19)
Then, the switching frequency of the transistor Q ₁ is determined by receiving the signal of the FM oscillation circuit (6). At this time, if the frequency of the FM oscillation circuit (6) increases, the switching frequency of the transistor Q ₁ also increases. Duty setting circuit (2
0) determines the ON period of the transistor Q ₁ , the timer IC (21) oscillates at the falling edge of the flip-flop (19), and the output of the output terminal 3 becomes H until the voltage of the capacitor C reaches 2 / 3Vcc. Level, and the transistor Q ₁ is on during this period. The trigger signal to the trigger terminal 2 of the timer IC (21) also changes according to the frequency change of the FM oscillator circuit (6). That is, the transistor Q ₁ is also driven in association with the frequency modulation of the high frequency inverter section (3).

FIG. 3 shows another embodiment of the voltage variable section (16), which is a step-down checker circuit, and the same working effect can be obtained. In addition to this, it is sufficient that the voltage swing can be controlled by frequency, pulse width and the like. When the current limiting impedance is capacitive, the operation is reversed but basically the same.

〔The invention's effect〕

As described above, the present invention provides the input section of the high frequency inverter section with the voltage control section in which the output voltage is controlled in the direction of suppressing the instantaneous change of the lamp current corresponding to the change of the output frequency of the high frequency inverter section. Even if the frequency is modulated, the change in the instantaneous value of the lamp current can be reduced, the change in the luminous flux can be suppressed, and the flicker can be eliminated. Moreover, the circuit configuration is simple and the high power factor can be similarly achieved. It is a thing.

[Brief description of drawings]

FIG. 1 (a) is a block circuit diagram of an embodiment of the present invention, FIG. 1 (b) is a lamp current waveform diagram of the same as above, and FIG. 2 (a) is a specific circuit diagram of essential portions of the same, FIG. (B) is the same timer
Block circuit diagram of the IC, FIG. 3 is a detailed circuit diagram of a main part of another embodiment of the present invention, FIG. 4 (a) is a block circuit diagram of a conventional discharge lamp lighting device, and FIG. 4 (b) is the same as above. FIG. 6 is a lamp current waveform diagram of FIG. (1) ... AC power supply, (2) ... Full wave rectifier, (3) ...
… High frequency inverter, (4) …… Discharge lamp, (16) ……
Voltage variable part.

Claims (1)

[Claims] 1. A discharge lamp lighting device for driving a high frequency inverter section by a power source obtained by rectifying an AC power source for frequency modulation to light a high pressure discharge lamp, wherein a change in output frequency of the high frequency inverter section is input to an input section of the high frequency inverter section. 2. A discharge lamp lighting device, comprising: a voltage control unit for controlling an output voltage in a direction of suppressing an instantaneous change of a lamp current corresponding to the above.