JPH0450720B2 - - Google Patents

Description

[Detailed description of the invention] Industrial applications The present invention relates to a discharge lamp lighting device.

Prior Art FIG. 5 shows a conventional discharge lamp lighting device. Basically, the power supply voltage E supplied by the DC power supply 1
is boosted to an alternating current high frequency voltage by the oscillation operation of the transistor inverter circuit 2 comprising switching transistors Q ₁ and Q ₂ , an inverter transformer T, and the like. This voltage is applied to the discharge lamp 3 connected to the secondary winding _N2 of the inverter transformer T to turn it on. Here, when lighting the discharge lamp 3, a method is adopted in which the filaments 3a and 3b of the discharge lamp 3 are preheated. For this reason, the discharge lamp 3
The power supply side terminals of filaments 3a and 3b are connected to the secondary winding N2, but the filaments 3a and _3b are connected to the secondary winding N2.
A series circuit of a diode _D1 and a transistor _Q3 is connected between the non-power supply side terminals of a and 3b.
This transistor Q ₃ consists of transistor Q ₄ , thyristor SCR ₁ , capacitor C ₄ , Zener diode ZD
The timer circuit 4 (the time constant is determined by the resistor _R16 and the capacitor _C4 ) is turned on only for a certain period of time (for example, 1 second) after the power is turned on.

As a result, when the power is turned on now, this transistor Q ₃ is on, so the secondary winding Nz of the inverter transformer T is connected to the filament 3a-
Short circuit only in one direction in the order of diode D ₁ - transistor Q ₃ - filament 3b, and filament 3
A short circuit current flows through a and 3b. Since the current in the reverse direction is blocked by the diode _D1 , the inverter transformer T will undergo magnetic saturation (that is, the ferrite core will be magnetized more strongly than usual), and this saturation phenomenon will cause the secondary short-circuit current to This results in a large current and an increase in short circuit current (according to experiments, approximately 1.5 times). In this way, the filaments 3a, 3b are preheated. When the transistor Q ₃ is turned off after a certain period of time, the filaments 3 a and 3 b are opened, and the discharge lamp 3 is turned off by the inverter transformer T.
A no-load secondary voltage is applied to the lamp, causing it to light up. According to this filament preheating method,
Compared to the rapid start method, no high voltage is applied to the discharge lamp 3 during the preheating period, so the lamp life can be significantly longer.

However, in such a preheating method, there is a problem that the preheating current cannot be significantly increased because the preheating current is limited by the lighting characteristics. For example, lighting devices used in vehicles such as trains have various environments, such as low temperature and low voltage (for example, ambient temperature = -5°C, input voltage =
There is a requirement that the starting light must be lit even when the voltage is 70V). In order to satisfy these demands, it is necessary to increase the no-load secondary voltage and preheating current, but in general, increasing the no-load secondary voltage shortens the lamp life, so It is preferable to use the lowest possible voltage. In this case, it is necessary to make the preheating current sufficiently large, but with the conventional method, as mentioned above, the necessary preheating current cannot be obtained due to constraints on the lighting characteristics, resulting in poor starting characteristics. It's summery. As I said,
Increasing the no-load secondary voltage side will shorten the lamp life.

Thus, the present applicant has proposed a discharge lamp lighting device that can sufficiently increase the preheating current to the filament without being restricted by the lighting characteristics, and can improve the starting characteristics. FIG. 6 shows the circuit configuration. The same parts as shown in FIG. 5 in terms of basic configuration are indicated using the same reference numerals. In this proposal, switching transistors Q ₁ , Q ₂ of transistor inverter circuit 2
The base resistances R ₂ and R ₃ for maintaining oscillation are divided into base resistances R ₂ ′, R ₃ ′ and base resistance R ₂₃ , and this base resistance R ₂₃ is connected to both switching transistors.
This is common to Q ₁ and Q ₂ , and a transistor Q ₅ , which serves as a base resistance short-circuit switch, is connected in parallel to this base resistor R ₂₃ .

A power winding _NSB is provided on the primary side _of the inverter transformer T.
A timer circuit 6 consisting of a resistor R ₂₄ and a capacitor ₆ is connected via a full-wave rectifier circuit 5, and
Thyristor controlled by this timer circuit 6
The SCR ₂ , a transistor _Q6 that controls on/off of the transistor _Q3 , and a transistor _Q7 that controls on/off of the transistor _Q5 are connected. Note that the resistor R ₁ is a starting resistor for causing the transistor inverter circuit 2 to oscillate.
Further, L is an input choke, and _C1 is a resonance tank capacitor.

In such a configuration, when the switch 11 is turned on and the power is turned on, the input chain L
- Starting resistance R ₁ - Base resistance R ₂ ', input chain L
A base current is applied to the transistors Q ₁ and Q ₂ through the starting resistor R ₁ and the base resistor R ₃ ', and the inverter circuit 2 starts oscillating. As a result, a lamp voltage is applied to the discharge lamp 3 via the inverter transformer T. At the same time, a voltage is induced in the power supply winding N _SB , so the base current flows to the transistor Q ₆ via _the resistor R ₂₂ - resistor R ₄₁ and turns it on _. A base current is also applied to Q ₃ and transistor Q ₃ is turned on. As a result, a short-circuit preheating current flows through the filaments 3a and 3b. At this time, transistor Q ₇ is connected through resistor R ₂₂ − resistor R ₂₆
Current also flows through the base of this transistor Q ₇
turns on. As a result, a base current is applied to the transistor _Q5 via the resistor _R20 and the transistor _Q7 , and the transistor _Q5 is turned on. That is, the base resistor _R23 is short-circuited by the transistor _Q5 , and the base resistors of the switching transistors _Q1 and _Q2 are only _R2 ' and _R3 ', respectively. This results in
The base current is the base winding N _B − transistor Q ₅
- Flows through the base resistor R ₂ ' or R ₃ ' to the base of each switching transistor Q ₁ , Q ₂ . On the other hand, when the timer circuit 5 times up and the thyristor SCR ₂ becomes conductive, the bases of the transistors Q ₆ and Q ₇ are grounded by the thyristor SCR ₂ .
As a result, the transistor _Q3 is also turned off, a high voltage is applied to the discharge lamp 3, and the discharge lamp 3 is turned on.
Also, since the transistor _Q5 is also turned off, the base resistor _R23 acts, and the base current becomes
Base winding N _B −Base resistance R ₂₃ −Base resistance
It flows through R ₂ ′ and R ₃ ′ to the bases of each switching transistor Q ₁ and Q ₂ .

Therefore, the resistance values are set so that the rated lighting characteristics are achieved when the base resistances of switching transistors Q ₁ and Q ₂ are R ₂ ′ + R ₂₃ and R ₃ ′ + R ₂₃ , respectively, and after the power is turned on. Transistor only for a certain period of time
By shorting only the base resistor R ₂₃ using Q ₅ , the base current can be reduced to R ₂₃ + (R ₂ ′・R ₃ ′)/R ₂ ′+R ₃ ′)/(R ₂ ′・R ₃ ′)
)/(R ₂ ′+R ₃ ′), which overdrives the inverter transformer circuit 2, allowing the necessary preheating current to flow through the filaments 3a and 3b of the discharge lamp 3. In this way, the filament 3a,
The preheating current for the filaments 3b can be set, and the filaments 3a and 3b can be sufficiently preheated with the necessary preheating current even under conditions such as low voltage and low temperature. This provides good starting characteristics and does not adversely affect lamp life.

Problems to be Solved by the Invention However, in this proposed method, transistors Q ₃ and Q ₅ each operate independently;
The on/off timing of both is random.
Here, if transistor _Q5 turns on before transistor _Q3 , a surge voltage will be generated when the inverter circuit 2 starts oscillating, and an overcurrent will flow to the discharge lamp 3, causing it to light up, with insufficient preheating of the filament. This will shorten the lifespan. Furthermore, if transistor Q ₃ turns off before transistor Q ₅ , the large filament preheating current will suddenly stop flowing, which will also generate a surge voltage, and it will take a long time before high frequency oscillation transformer Q ₅ turns off. An overcurrent flows through the intermittent discharge lamp 3, which adversely affects the life of the discharge lamp 3.

Therefore, the present invention eliminates the generation of surge voltage during switching while maintaining the function of improving the starting characteristics at low temperatures and resistance voltages as proposed above, and
An object of the present invention is to obtain a discharge lamp lighting device that can extend the life of a discharge lamp by preventing overcurrent.

Means for Solving the Problems In the present invention, the power supply side terminals of the filaments 3a, 3b of the discharge lamp 3 are connected to the secondary winding _N2 of the high frequency oscillation transformer T of the transistor inverter circuit 2, and the filaments 3a, A discharge lamp lighting device which preheats filaments 3a and 3b by connecting in series a diode _D1 and a filament short-circuiting switch, such as a transistor _Q3 , which is turned on only for a certain period of time after the power is turned on, to the non-power side terminal of 3b. In the transistor inverter circuit ₂ , a switch for reducing the base resistance, such as a transistor Q5, which is turned on only for a certain period of time after the power is turned on, is connected in parallel to a part of the base resistance of the switching transistors Q 1 and Q 2 of the transistor inverter circuit ₂ , and a switch for reducing the base resistance, such as a transistor Q ₅ , is connected in parallel to a part of the base resistance of the switching transistors Q 1 and Q 2 of the transistor inverter circuit 2. Switch Q ₃
The on-on sequence control circuit 7 or filament short-circuiting circuit turns on the base resistance reducing switch _Q5 at the same time as the base resistance reducing switch _Q5 , turns off the base resistance reducing switch Q5 after a certain period of time, and turns off the filament shorting switch _Q3 instantaneously thereafter. An on-off sequence in which switch Q ₃ is turned on, and an instant later, base resistance reduction switch Q ₅ is turned on, and after a certain period of time, base resistance reduction switch Q ₅ is turned off, and a moment later, filament shorting switch Q ₃ is turned off. A configuration in which a control circuit 10 is provided is adopted.

Operation After the power is turned on, the transistor Q ₃ is turned on for a certain period of time to short-circuit between the filaments 3a and 3b, and a short-circuit preheating current flows through the filaments 3a and 3b. At this time, the switching transistors Q ₁ and
On the Q ₂ side, a part of the divided base resistance is shorted by the transistor Q ₅ to increase the base current of the switching transistors Q ₁ and Q ₂ to overdrive, thereby increasing the filament preheating current and making it sufficient. By performing proper preheating, starting characteristics can be improved even under conditions such as low temperature and low voltage. At this time, normally the transistor
By turning off _Q5 , the rated lighting characteristics can be ensured. The on/off sequence control circuit 7 or 10 controls the on/off operation timing of the transistors Q 3 and Q ₅ by turning on both the transistors Q ₃ and Q ₅ at the same time or turning on the transistor _{Q 3 in} advance, and when the transistors are off. Since the transistor _Q5 is turned off first, no surge voltage is generated in the discharge lamp 3, and no overcurrent flows, so that the life of the discharge lamp 3 is extended.

Embodiment A first embodiment of the present invention will be described based on FIGS. 1 and 2. The same parts as those shown in FIG. 6 are indicated using the same reference numerals. In this embodiment, an on/off sequence control circuit 7 is provided for transistors Q ₃ and Q ₅ . This on/off sequence control circuit 7 includes a transistor Q8 connected to the transistor _Q3 , _a transistor _Q9 controlling this transistor _Q8 , and this transistor _Q9 .
and the transistor _{Q10 ,} a capacitor _C7 and a diode _D2 connected to the base of the transistor _Q10 , and a plurality of resistors _R31 to _R39 . here,
The base resistance of this embodiment is composed of R ₂ ′, R ₃ ′, R ₂ ″, and R ₃ ″, and when transistor Q ₅ is turned on, the base resistance for transistor Q ₁ is R ₂ ′.
The parallel resistance with R ₂ ″, the base resistance for transistor Q ₂ is reduced as the parallel resistance with R ₃ ′ and R ₃ ″,
When transistor Q ₅ is off, the base resistance for transistor Q ₁ is the parallel resistance of R ₂ ′ + (R _{3 ′} + R ₃ ″), and the base resistance for transistor Q ₂ is the parallel resistance of R ₃ ′ and (R ₃ ″ + R ₂ ′+R ₂ ″). Also, inverter transformer T
A detection winding Ns is connected to the secondary side of the detector, and a lamp abnormality detection circuit 8 is provided as a power line to detect abnormalities in the discharge lamp 3 based on the voltage of the detection winding Ns. 9.

In such a configuration, when the switch 11 is turned on and the power is turned on, the resistance R ₃₇ − resistance R ₃₈ −
The base current flows to the transistor Q ₁₀ through the diode D ₂ and the transistors Q ₃ , Q ₅ , Q ₈ , Q ₉ ,
Q ₁₀ is on standby. Further, in the inverter circuit 2, current flows to the bases of the transistors _Q1 and _Q2 via the resistor _R1 to the resistor R' and the resistor _R1 to the resistor _R3 ' to start oscillation. As a result, when the secondary voltage and base winding voltage of the inverter transformer T are generated, the transistors Q ₃ , Q ₅ , Q ₈ , Q ₉ , and Q ₁₀ are in the on state, so the transistors Q ₁ ,
The base current of _Q2 is increased, and a sufficient preheating current flows through the filaments 3a and 3b of the discharge lamp 3.
Then, when the fixed time of the timer circuit 6 has passed, the thyristor SCR ₂ is turned on and the transistor Q ₁₀ is turned on.
The base of is grounded. At this time, the transistor
Q ₁₀ does not turn off completely due to the charge of capacitor C ₇ , but turns off after passing through class A operation. During class A operation of this transistor Q ₁₀ , transistor Q ₅
Since the base current of this transistor decreases
_Q5 also goes through class A operation and then turns off. On this occasion,
Until transistor _Q5 is completely turned off, base current flows through transistor _Q3 , so
Transistor _Q3 turns off with an instant delay compared to transistor _Q5 . i.e. transistor
Q ₃ is compared to transistor Q ₅ , transistor Q ₃ ,
Since it is connected to transistor Q ₈ through a two-stage amplifier, the constants of transistor Q ₉ and transistor Q 8 are determined so that transistor Q ₃ remains substantially on even when transistor Q ₅ is substantially off _. Because transistor Q ₃ is transistor Q ₅
It will definitely turn off later than before. FIG. 2 shows these on/off timings.

In this way, in this embodiment, the transistors Q ₃ ,
An on/off sequence control circuit 7 is provided for Q ₅ , and transistors Q ₃ and Q ₅ are turned on at the same time when oscillation starts. ), the surge voltage generated on the secondary side of the inverter circuit 2 is short-circuited through the diode D ₁ and the transistor Q ₃ , so it is used to preheat the filaments 3a and 3b, and the surge voltage is This means that the voltage will no longer be generated. This prevents unnecessary high voltage from being applied to the discharge lamp 3. Also, looking at the off state, when transistor _Q3 turns off, the transistor
_Q5 is turned off reliably (instantaneously) in advance, and transistor _Q3 is not turned off abruptly, but is turned off with the time constant of capacitor _C7 , so no surge voltage is generated. transistor
Since _Q5 turns off → transistor _Q3 turns off, no overcurrent flows through the discharge lamp 3. This results in
The life of the discharge lamp 3 is extended, and the transistor
The withstand voltage of Q ₁ and Q ₂ can also be lowered. In addition,
Since the deviation in the operation of transistors Q ₃ and Q ₅ is instantaneous and short, the filaments 3a and 3b are effectively preheated by increasing the base current.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. In this example, a diode _D3 is added to the base of the transistor _Q9 .
An off-sequence control circuit 10 is provided. As a result, when oscillation starts, the transistor
The transistor Q 5 is turned on after the transistor Q ₃ is turned on, and when the transistor Q ₅ is turned off, the transistor Q ₅ is turned off first and the transistor Q ₃ is turned off instantaneously after that, as in the previous embodiment. First, when inverter circuit 2 starts oscillating, resistance R ₃₇ - resistance
A base current flows through the transistor _Q9 via the _R40 -diode _D3 , turning on the transistors _Q9 and _Q8 , thereby turning on the transistor _Q3 . or,
Transistor Q ₁₀ is resistor R ₃₇ , R ₃₈ and diode
It turns on later than transistor Q ₉ by a time constant determined by D ₂ and capacitor C ₄ . By turning on this transistor Q ₁₀ , transistor Q ₅
turns on. As a result, the preheating current for the filaments 3a and 3b increases with the base current increasing, but at this time, the transistor _Q3 is turned on reliably in advance, so it is possible to suppress the surge voltage to a low level. can. Then, when thyristor SCR ₂ is turned on by timer circuit 6,
Transistor Q ₉ loses the base current due to the route of resistor R ₄₀ - diode D ₃ , but the transistor
Since the base current is applied from the Q ₁₀ side, the transistor remains active until this transistor Q ₁₀ turns off.
_Q9 will also continue to be on. Therefore, as in the case of the embodiment described above, the transistors are turned off in the order of turning off the transistor _Q5 and turning off the transistor _Q3 , thereby preventing the generation of surge voltage. FIG. 4 shows a timing chart for such an operation.

Effects of the Invention The present invention provides, in addition to a filament short-circuiting switch that short-circuits the filament of a discharge lamp for a certain period of time after the power is turned on as described above to flow a short-circuit preheating current.
Since a base resistance reduction switch is provided to reduce the base resistance of the switching transistor, the base current to the switching transistor can be increased only for a certain period of time after the power is turned on, and the filament preheating current can be made sufficient. The preheating is sufficient even under various environments, and the starting characteristics can be improved.In this case, an on/off sequence control circuit is provided to control the filament shorting switch and the base resistance reducing switch simultaneously or simultaneously. Instantly advance and turn on,
In addition, since the base resistance reducing switch is turned off instantaneously before the filament shorting switch, the generation of surge voltage and overcurrent can be prevented, and the life of the discharge lamp can be extended. Also, the breakdown voltage of the switching transistor can be lowered.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention,
Fig. 2 is a timing chart showing its operation, Fig. 3 is a circuit diagram showing a second embodiment of the present invention, and Fig. 4 is a timing chart showing its operation.
FIG. 5 is a timing chart showing its operation, FIG. 5 is a circuit diagram showing a conventional example, and FIG. 6 is a circuit diagram showing a content already proposed by the applicant. 2...Transistor inverter circuit, 3...Discharge lamp, 3a, 3b...Filament, 7...On/off sequence control circuit, 10...On/off sequence control circuit, _D1 ...Diode, _Q3
...transistor (switch for shorting filament), Q ₅ ...transistor (switch for reducing base resistance), R ₂ ′ to R ₃ ″ ...base resistance.

Claims (1)

[Scope of Claims] 1. The power supply side terminal of the filament of the discharge lamp is connected to the secondary winding of the high frequency oscillation transformer of the transistor inverter circuit, and a diode is connected to the non-power supply side terminal of this filament for a certain period of time after the power is turned on. In a discharge lamp lighting device that preheats the filament by connecting it in series with a filament shorting switch that is turned on, the switch is connected in parallel to a part of the base resistor of the switching transistor of the transistor inverter circuit for a certain period of time after power is turned on. Connect the base resistance reducing switch that turns on only the base resistance reducing switch, turn on the filament shorting switch and the base resistance shorting switch at the same time, turn off the base resistance reducing switch after a certain period of time, and turn off the filament shorting switch instantly after that. A discharge lamp lighting device characterized in that it is provided with an on/off sequence control circuit that controls the operation of the discharge lamp. 2 Connect the power supply side terminal of the filament of the discharge lamp to the secondary winding of the high frequency oscillation transformer of the transistor inverter circuit, and connect a diode to the non-power supply side terminal of this filament and a filament short-circuit switch that is turned on only for a certain period of time after the power is turned on. In a discharge lamp lighting device that preheats the filament by connecting the transistors in series, a base resistance reducing device is connected in parallel to a part of the base resistance of the switching transistor of the transistor inverter circuit and is turned on only for a certain period of time after power is turned on. switch, turn on the filament shorting switch, turn on the base resistance reducing switch instantaneously, turn off the base resistance reducing switch after a certain period of time, and turn off the filament shorting switch instantaneously after that. A discharge lamp lighting device characterized by being provided with an off-sequence control circuit.