JPH0650677B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for lighting a high-pressure discharge lamp at a high frequency by a bridge type inverter.

[Background technology]

In a conventional general discharge lamp lighting device, the ballast is large in both size and weight because the ballast has a circuit structure composed of a choke coil, a transformer, a capacitor and the like alone or in combination.

From the above point of view, it is desired to reduce the size, weight and efficiency of the discharge lamp lighting device, and for that reason, it is considered to light the discharge lamp at a high frequency. For example, as a lighting device for a fluorescent lamp, a high frequency lighting device using a switching transistor, a thyristor or the like has been put into practical use.

Even in a lighting device for a high pressure discharge lamp, if high frequency is used, the same effect as that of a fluorescent lamp can be obtained, but it has been conventionally known that when a high pressure discharge lamp is lit at high frequency, arc instability caused by acoustic resonance exists. Has been.

As a method of eliminating arc instability due to acoustic resonance, rectangular wave lighting has been described in the literature "Characteristics of Acoustic
al Resonance In Discharge Lamps ”ILLUMINATING ENGIN
EERING December 1970, pp. 713-716. However, this method, although the arc is stable,
Since the flat portion of the rectangular wave is used as a current limiting element by the resistor, the size is increased and power loss is increased. Further, in the case of a high-frequency rectangular wave, the rising and falling edges of the waveform are steep, which causes a problem of noise, and this measure leads to a significant increase in cost.

On the other hand, as a lighting device for a high pressure discharge lamp
No. 100 is disclosed. In this device, the flat part of the rectangular wave is placed in a state in which high-frequency components are superimposed, and an inductance is used as a current limiting element to reduce the size of the device. However, this method requires a transformer for oscillation and a semiconductor element dedicated to the chopper, and the lighting device is still large. US Pat. No. 4,170,74
Some are disclosed in No. 7. What is described therein is a bridge inverter, which does not have an oscillating transformer and also serves as a semiconductor element, but does not show any acoustic resonance phenomenon due to high frequency lighting of a high pressure discharge lamp.

FIG. 7 shows a conventional discharge lamp lighting device shown in US Pat. No. 4,170,747. In the figure, 1 and 2 are power supply terminals, 16, 18, 30, and 28 are bridge-connected transistors, 24, 26, 34, and 32 are diodes connected in parallel to the transistors 16, 18, 30, and 28, and 12 Is a choke coil, 10 is a high pressure discharge lamp,
8, 14 are capacitors, 114 are current detection resistors, 12
Reference numeral 0 is a control unit. FIG. 8 shows transistors 16, 18,
It is a timing diagram which shows operation | movement of 30,28.

Transistors 16 and 18 are 50/60 Hz or 400
When the transistor 16 is on, the transistor 30 performs an on / off operation with a variable duty ratio of, for example, 20 KHz (1 / T ₂ ) when the transistor 16 is on, and when the transistor 18 is on, the transistor 28 is on / off similar to the transistor 30. I do. Further, when the polarity of the high pressure discharge lamp 10 is reversed, the four transistors 16, 18, 30, 2 are
8 is turned off at the same time and has a rest period T _D. The control unit 120 receives the signal from the current detection resistor 114 and controls the transistors 16, 18, 30, 28. In this case, the on / off duty ratio changes depending on the magnitude of the voltage of the current detection resistor 114.

Therefore, a rectangular wave alternating current containing high frequency ripples flows through the high pressure discharge lamp 10.

9A, 9B and 9C show transistors 16 and 3
It is a figure which shows the current waveform of each part in the state where 0 is operating. The current flowing through the choke coil 12 is I _A , the collector current of the transistor 30 is I _B , and the current of the diode 26 is I _C.

The current waveform of each of the above parts depends on the inductance of the choke coil 12, the capacitance of the capacitor 14, the lamp impedance of the high-pressure discharge lamp 10, the switching frequency and the duty ratio of the transistor 30, and is shown in FIGS. 9A, 9B and 9
It is roughly classified into three modes (representative examples) in FIG. t ₁ -t
₂ while is a state in which the transistors 16, 30 is on, current flows through a closed circuit 1-16-12-10,14-30-2, from _{t 2} when the transistor 30 is turned off until _{t 1} Current flows in the closed circuit of 12-10 and 14-26-16. In the mode shown in FIG. 9A, the transistor 30 is turned on almost at the same time when the current I _{C of the} diode 26 becomes zero. Mode of FIG. 9B becomes current _{I C} is zero, the release of energy in the choke coil 12 in _{t 3} when there is a rest period between _t 3 -t ₁ ends. In the mode shown in FIG. 9C, the transistor 30 is turned on before the energy of the choke coil 12 is completely discharged. In this case, a pulsed current flows at time t ₁ . This is because the transistor 30 is turned on before the accumulated charge of the diode 26 is released,
And the transistor 30 are both turned on for a time (t ₁ ). Therefore, a closed circuit 1-26-30-2 is formed, and a pulsed current flows.

If the state as shown in FIG. 9C occurs, the switching loss of the diode 26 and the transistor 30 will greatly increase. Further, in the mode shown in FIG. 9B, the phenomenon as in the mode shown in FIG. 9C does not occur, but the idle period (t ₃ −t ₁ )
As a result, problems such as extinction may occur, and high-frequency components of the lamp current may increase, causing arc fluctuations.

Further, the high-pressure discharge lamp 10 is almost in a short-circuit state at the time of starting, the lamp voltage is as low as 10 to 30 V, and the equivalent resistance of the lamp is small. Therefore, the mode becomes as shown in FIG. Switching loss increases.

As described above, the mode shown in FIG. 9C occurs due to a large impedance change of the high-pressure discharge lamp 10, and the withstand capacity of the diode 26 and the transistor 30 needs to be large, which causes a cost increase. Moreover, the efficiency of the entire lighting device is reduced due to an increase in switching loss.

Note that Japanese Patent Publication No. 49-19794 describes the above three modes, but the discharge lamp lighting device disclosed therein uses a chopper, and does not use the inverter of the present invention at all. It is different.

[Object of the Invention]

The present invention reduces the switching loss of transistors and diodes that form a high-frequency inverter, reduces the high-frequency component of the lamp current, and allows the high-pressure discharge lamp to maintain stable lighting without causing arc fluctuations. An object of the present invention is to provide a lighting device.

[Disclosure of Invention]

The discharge lamp lighting device of the present invention prevents the acoustic resonance phenomenon of the high pressure discharge lamp and stably lights the high pressure discharge lamp without causing fluctuations in the arc.
The drawbacks of No. 0,747 are solved by applying Japanese Patent Publication No. Sho 49-19794 to Takumi.

The discharge lamp lighting device of the present invention includes a DC power supply, a series circuit of first and second switching elements connected in parallel between both poles of the DC power supply, and a series circuit of third and fourth switching elements; First and second diodes respectively connected in antiparallel to the second and fourth switching elements connected to the negative electrode side of the DC power source, a connection point of the first and second switching elements, and the third and The high pressure discharge lamp connected between the connection point of the fourth switching element and the second and fourth switching elements are alternately turned on and off at a low frequency, and the first switching element is turned on during the on period of the fourth switching element. The switching element is turned on and off at a high frequency, and the third switching element is turned on and off at a high frequency during the on period of the second switching element. In a discharge lamp lighting device comprising a control circuit, the control circuit outputs a first zero level signal when detecting a substantially zero level of a current flowing through the first diode, and the second diode Current detection means for outputting a second zero level signal when a substantially zero level of the current flowing in the current is detected, and the first switching is performed when the first zero level signal from the current detection means is received. A switching element control means is provided for switching the element to an ON state and for switching the third switching element to an ON state when receiving the second zero level signal.

In this way, the current detecting means detects the substantially zero level of the current flowing through the first and second diodes, and when the first and second zero level signals are received from the current detecting means, the first and third diodes are detected. When the switching elements are respectively turned on, that is, when the first and third transistors are turned on when the currents of the first and second diodes become substantially zero, the first transistor and the first transistor are turned on. A pulsed current does not flow through the series circuit of the first diode and the series circuit of the third transistor and the second diode, and the lamp current does not have a rest period.

Therefore, it is possible to reduce the switching loss of the transistor and the diode described above, reduce the high frequency component of the lamp current, and stably maintain the lighting without causing the fluctuation of the arc in the high pressure discharge lamp. Also,
The first and the second switching elements, which are connected to the negative side of the DC power supply and operate in low frequency, are connected in anti-parallel to each other.
Since the ground line of the current detection means for detecting the current flowing through the second diode and the ground line of the switching element control means are common, the first and second diodes can be used without using an insulating transformer such as a current transformer. The flowing current can be easily detected.

More specifically, in this discharge lamp lighting device, as shown in FIG. 1, the transistors Q _{1 to} Q ₄ are connected in a bridge shape, and the transistor Q is connected to the negative side of a DC power supply.
Diodes D ₁ and D ₂ are connected in parallel to ₂ and Q ₄ , respectively, and the connection point of the transistors Q ₁ and Q ₂ and the transistor Q ₁ are connected.
A series circuit of a choke coil L ₁ and a high pressure discharge lamp LA is connected between the connection point of ₃ and Q ₄ , and a capacitor C ₁ is connected in parallel to the high pressure discharge lamp LA.

FIG. 2A is a timing chart showing the operation of each part of FIG.

The point of this description is that when the currents I _D1 and I _D2 of the diode D ₁ or D ₂ become substantially zero, the transistor Q
_This is the point where an ON signal is applied to ₁ or Q ₃ .

The discharge lamp lighting device, the transistor _Q 2 with a period _{T 1,}
Q ₄ is turned on and off alternately, and when the transistor Q ₄ is turned on, the transistor Q ₁ is turned on and off in the cycle T ₂ ,
Although not shown, the transistor Q ₃ turns on and off when the transistor Q ₂ turns on.

In Figure _2A, between the t 1 -t _2, the transistor Q
₁ is turned on, and during this period, 1-Q ₁ -L ₁ -LA, C ₁
A circuit of −Q ₄ −2 is formed, a current I _Q1 flows through the transistor Q ₁ , and energy is stored in the choke coil L ₁ . In between following _t 2 -t _3, the transistor _{Q 1} is turned _off, L 1 _-LA, energy of the choke coil _{L 1} in the circuit of C _{1 -Q} 4 -D 1 is released. I _D1 is the current I _L1 flowing through the diode D ₁ at this time, I _L1 is the current flowing through the choke coil L ₁ , and I _LA is the lamp current. Then, at time t ₃ when the current I _D1 flowing through the diode D ₁ becomes zero, the transistor Q ₁ is turned on again, and the above operation is repeated.

When such an operation is performed, 1-Q ₁ at time t ₃
The surge current due to the -D _1-2 circuit does not flow, and the mode shown in FIG. Transistor Q ₂ ,
The same applies when Q ₃ is operating.

FIG. 2B is a diagram showing a current waveform of each part when the transistors Q ₁ and Q ₄ are operating. In the figure, I
_C1 is the current in the capacitor C ₁ . Choke coil L
The current I _L1 of _{No. 1} is _divided into the lamp currents I _LA and I _C1 , but the capacitor C ₁ has a low impedance at high frequencies, and almost all high frequency components flow to the capacitor C ₁ . The lamp current I _LA has a waveform in which a high frequency is superimposed on a direct current when viewed in a short time. On the other hand, in an instant,
At time t ₁ , the current I _L1 is zero and the high pressure discharge lamp L
The current flowing into the circuit of A and the capacitor C ₁ is zero,
The electric charge of the capacitor C ₁ is discharged to the high pressure discharge lamp LA. That is, at time t ₁ , I _L1 = 0 and I
_C1 = I _LA . Further, at time t ₄ , I _C1 = 0 and I _L1 = I _LA . Time t ₅ is the same as time t ₄ .

With such an operation, a surge current does not flow in each of the transistors Q ₁ and Q ₃ and the diodes D ₁ and D ₂ shown in FIG. 9A, the switching loss can be reduced, and the high frequency ripple is _generated in the lamp current I _LA . It is possible to obtain a waveform with a small amount of light, and to stably keep the high-pressure discharge lamp LA lit without causing arc fluctuation due to an acoustic resonance phenomenon. Further, as described above, since the ground line of the current detecting means and the ground line of the switching element controlling means are common, the current flowing through the first and second diodes can be detected without using an insulating transformer such as a current transformer. Can be done easily.

Embodiment A discharge lamp lighting device according to a first embodiment of the present invention will be described with reference to FIGS. 3 and 4. In FIG. 3, reference numeral 3 is a control unit, and the others are the same as in FIG.

FIG. 4 shows a specific configuration of the control unit 3. In FIG. 4, the oscillating circuit 5 oscillates at several hundred Hz, and the flip-flop circuit 6 takes out two signals and outputs the lamp current I
Obtain the reference drive signals for the positive and negative half cycles of _LA . This signal is sent to the base drive circuit 7 of the transistors Q ₂ and Q ₄ which are turned on and off at several hundred Hz. On the other hand, transistors Q ₁ and Q ₃ that turn on and off at several tens of KHz
To the base drive circuit 9 of the timer (IC555: μ
A signal obtained by combining the output signal of I _{1 and} the output signal of the flip-flop circuit 6 with the AND elements I ₃ and I ₄ is given.

The current detection resistor 4 detects the currents I _D1 and I _D2 of the diodes D ₁ and D ₂ , and the comparator I ₂ divides the voltage drop and the reference voltage V _REF by resistors R ₆ and R ₇ to obtain a voltage V _R7 . compare, the higher the voltage across the current detecting resistor 4 than the voltage V _R7, the output of the comparator I ₂ is "H"
Then, the transistor Q ₅ is turned on. The terminal of the timer I ₁ is a reset terminal, and when the transistor Q ₅ is turned on, oscillation by the resistors R ₁ , R ₂ and the capacitor C ₂ is stopped. That is, in the state where the current I _D1 or I _D2 is flowing, the output of the comparator I ₂ turns on the transistor Q ₅ to activate the reset, and when the current I _D1 or I _D2 becomes substantially zero, the transistor Q 5 becomes zero. _{When 5} turns off, the resistors R ₁ and R ₂ and the capacitor C ₂ start oscillating, the output terminal of the timer I ₁ becomes “H”, and the voltage of the capacitor C ₂ becomes (2/3) V _CC , the output The terminal becomes "L". This time corresponds to the on-time of the transistor Q ₁ or Q ₃ . Timer I ₁ is operating as an astable multivibrator, but R ₁ >> R ₂ ,
"L" time of the output terminals _C 2 _-R 2 - when is short time so determined to approximate a constant of the circuit, the output terminal once becomes "L", the transistor to _Q 1 the main circuit, _{Q 3}
Is off and the currents I _D1 and I _D2 flow, the transistor Q ₅ is turned on, the timer I ₁ does not oscillate, and the output terminal remains "L". Therefore, the output terminal is "H"
The time of is determined by the resistors R ₁ and R ₂ and the capacitor C ₂ , and the time of “L” at the output terminal is the time until the currents I _D1 and I _D2 become zero.

By such an operation, the current I of the inductance L _1
L1 becomes the mode shown in FIG. 9A, and the transistor Q
_A surge current does not flow in the ₁ , Q ₃ diodes D ₁ , D ₂ and a diode having a small withstand capacity can be used, which is inexpensive and switching loss can be significantly reduced. Further, the efficiency of the entire lighting device can be improved by significantly reducing the switching loss, and heat generation is reduced. Further, it is possible to flow a small current of DC component in the choke coil L _1, a reduction in iron loss of the choke coil L _1, it can be made compact.

Further, since the current detection resistor 4, the comparator I ₂ and the ground line of the peripheral circuit thereof can be used in common, it is easy to detect the currents of the diodes D ₁ and D ₂ and the circuit becomes simple. This is because an insulating transformer is not required and resistance can be directly detected. A small-capacity capacitor may be connected in parallel with the current detection resistor 4.

Further, as a lighting device for a high-pressure discharge lamp, a chopper circuit or the like is not necessary, and it is possible to realize a significant reduction in size and weight.

Further, even in a state where the lamp impedance changes significantly such as at the time of transition from the start to the steady state, the transistors Q ₁ and Q ₃ are turned on when the diode currents I _D1 and I _D2 become zero. Since the ON intervals of the transistors Q ₁ and Q ₃ are automatically lengthened to operate in the mode shown in FIG. 9A, a rest period may occur (mode shown in FIG. 9B), the transistors Q ₁ and Q ₃ , the diode D ₁ , D ₂
A surge current does not flow in the mode (FIG. 9C mode), the high-pressure discharge lamp LA is not extinguished, and the switching loss can be surely changed to a steady state.

A second embodiment of the present invention will be described with reference to FIGS. 5 and 6. In FIG. 5, 3a is a control unit, and the others are the same as in FIG.

FIG. 4 shows a specific configuration of the control unit 3a. The control unit 3a includes a current detection resistor 4 that detects the currents of the diodes D ₁ and D ₂ and a transistor Q ₁ that operates at high frequency.
It has a current detection resistor 4a for detecting the collector currents I _Q1 and I _Q3 of Q ₃ .

Differences from the embodiment of FIGS. 1 and 2 are as follows. When the currents I _Q1 and I _Q3 are detected and become a predetermined value (voltage obtained by dividing the reference voltage V _REF by the resistors R ₈ and R ₉ ) or more, the comparator I ₆ becomes “H” and the transistor Q ₅ is turned on, Stop the oscillation of timer I ₁ . That is, the peak values of the currents I _Q1 and I _Q3 are prevented from rising above a predetermined value, and the on-time of the transistors Q ₁ and Q ₃ is substantially changed by the currents I _Q1 and I _Q3 .

Since the currents of the diodes D ₁ and D ₂ are detected, the off time of the transistors Q ₁ and Q ₃ is the diode D 1.
The time until the currents I _D1 and I _{D2 of 1} and D ₂ become zero is similar to the operation of the first embodiment.

That is, in the first embodiment, the ON pulse width is constant and the OFF time is until the currents I _D1 and I _{D2 of the} diodes D ₁ and D ₂ become zero. The ON pulse width changes with the peak value of the currents I _Q1 and I _Q3 , and the OFF time changes to the currents I _D1 and I of the diodes D ₁ and D _2.
The difference is that it is the time until _D2 becomes zero.

This embodiment has the same effects as the first embodiment except that constant power can be achieved.

The zero detection of the currents I _D1 and I _D2 can be performed by a current transformer, and various methods other than this can be considered.

It is also possible to use thyristors as a switching element instead of the transistor Q ₁ to Q _4.

Effect of the Invention In the discharge lamp lighting device of the present invention, the current detecting means detects the substantially zero level of the current flowing through the first and second diodes, and receives the first and second zero level signals from the current detecting means. When the first and third switching elements are sometimes turned on, that is, the first
When the first and third transistors are turned on when the current of the second diode and the current of the second diode become substantially zero, the series circuit of the first transistor and the first diode and the third circuit
No pulsed current flows through the series circuit of the transistor and the second diode, and there is no rest period in the lamp current.

Therefore, it is possible to reduce the switching loss of the transistor and the diode described above, reduce the high frequency component of the lamp current, and stably maintain the lighting without causing the fluctuation of the arc in the high pressure discharge lamp. Also,
The first and the second switching elements, which are connected to the negative side of the DC power supply and operate in low frequency, are connected in anti-parallel to each other.
Since the ground line of the current detection means for detecting the current flowing through the second diode and the ground line of the switching element control means are common, the first and second diodes can be used without using an insulating transformer such as a current transformer. The flowing current can be easily detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the configuration of the present invention, FIGS. 2A and 2B are waveform diagrams of respective portions of FIG. 1, FIG. 3 is a circuit diagram of a first embodiment of the present invention, and FIG. FIG. 5 is a detailed circuit diagram of a main part thereof, FIG. 5 is a circuit diagram of a second embodiment of the present invention, FIG. 6 is a detailed circuit diagram of the main part, and FIG. 7 is a circuit of a conventional discharge lamp lighting device. Fig. 8 is a waveform diagram of each part, Fig. 9A,
FIGS. 9B and 9C are current waveform diagrams of each part in the three modes in the apparatus of FIG. Q ₁ ... transistor (first switching element), Q ₂ ... transistor (second switching element), Q ₃ ... transistor (third switching element), Q ₄ ... transistor ( _fourth switching element) ), LA ... high-pressure discharge lamp, 3 ... control unit

Continuation of front page (56) Reference JP-A-59-60996 (JP, A) JP-A-55-66289 (JP, A) JP-A-53-147924 (JP, A) JP-A-59-46796 (JP , A) JP 59-60995 (JP, A) JP 47-21624 (JP, A) JP 57-126099 (JP, A) JP 60-255067 (JP, A) JP 60-121964 (JP, A) JP-A-60-156280 (JP, A) JP-B-49-19794 (JP, B1)

Claims (1)

[Claims] 1. A DC power supply, a series circuit of first and second switching elements and a series circuit of third and fourth switching elements connected in parallel between both poles of the DC power supply, and a negative electrode of the DC power supply. First and second diodes respectively connected in anti-parallel to the second and fourth switching elements connected to the side, connection points of the first and second switching elements, and the third and fourth switching elements. The high pressure discharge lamp connected between the element and the connection point of the element and the second and fourth switching elements are alternately turned on and off at a low frequency to turn on the first switching element during the on period of the fourth switching element. A control circuit for turning on and off at a frequency and turning on and off the third switching element at a high frequency during an on period of the second switching element. In the discharge lamp lighting device, the control circuit outputs a first zero level signal when detecting a substantially zero level of the current flowing through the first diode, and outputs a first zero level signal of the current flowing through the second diode. A current detecting means for outputting a second zero level signal when detecting the zero level is provided, and when the first zero level signal from the current detecting means is received, the first switching element is turned on. A discharge lamp lighting device, characterized in that it is provided with a means for shifting the third switching element to an ON state when receiving the second zero level signal.