JPH043079B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that uses an inverter to convert power from a DC power source into high frequency power and applies the power to a discharge lamp such as a fluorescent lamp to light it.

2. Description of the Related Art Conventionally, there has been a device as shown in FIG. 1 as a device for converting power from a DC power source into a high frequency of several KHz or higher using an inverter to light a discharge lamp of a fluorescent lamp.

In Figure 1, 1 is a commercial frequency AC power supply;
2 is a full-wave rectifier, and 3 is an inverter, which here is composed of a self-excited transistor inverter equipped with an output transformer 6. 4 is a control device that controls the operation of this inverter 3. 5 is a discharge lamp, and 5A and 5B are electrodes.

The inverter 3 includes an output transformer 6 consisting of a collector winding 6C, a base feedback winding 6B, a filament winding 6F, and a secondary winding 6S, and a midpoint between the collector winding 6C and the output of the full-wave rectifier 2. an inductance 7 connected to the side, transistors 8A, 8B, base resistors 9A, 9B of the transistors 8A, 8B, a capacitor 10 connected in parallel with the secondary winding 6S, and also connected in series with the secondary winding. The resonant circuit is composed of a chi-yoke coil 11 and a resonant circuit.

The control device 4 also includes a transformer 13 connected to the AC power supply 1, a full-wave rectifier 14 for rectifying the output of the transformer 13, a resistor 15 and a capacitor 16 connected to both output ends of the full-wave rectifier 14, and a A trigger element 17 whose one terminal is connected to the connection point between the resistor 15 and the capacitor 15, a diode 18 whose anode is connected to the other terminal of the trigger element 17, the anode of which is connected to the emitter of the transistor 8A, and the cathode of which is connected to the full-wavelength transistor 8A. The control device 4 is composed of a thyristor 19 as a switch element whose gate is connected to the cathode of the diode 18 and a timer device 20 at the negative terminal of the rectifier 14.
The output signal is inputted to the bases of the transistors 8A, 8B via the resistors 9A, 9B.

Further, the timer device 20 includes a series circuit of a diode 21 and an electrolytic capacitor 22 connected to the output terminal of the full-wave rectifier 14, a series circuit of a resistor 23 and a capacitor 24 connected in parallel with the electrolytic capacitor 22, and a series circuit of a resistor 23 and a capacitor 24 connected in parallel with the electrolytic capacitor 22. It consists of a series circuit of a Zener diode 25 and a diode 26 connected between the connection point of the capacitor 24 and the resistor 23 and the gate of the thyristor 19.

Next, detailed operation will be explained. AC power supply 1
When is supplied, a voltage as shown in FIG. 2A is applied to the inverter 3 via the full-wave rectifier 2. At the same time, a predetermined voltage is also generated in the transformer 13 of the control device 4, and a pulsating DC voltage that has also been full-wave rectified is supplied from the full-wave rectifier 14. The resistor 15, the capacitor 16, and the trigger element 17 operate in the same manner as a well-known phase control pulse generator, and each half cycle of the AC power supply 1 has a predetermined phase, for example, the phase shown at θ ₁ in FIG. 2A. generates a trigger pulse. Therefore, the switch element 19 (consisting of a thyristor here) conducts at phase θ ₁ and supplies the base current to the transistors 8A, 8B of the inverter 3 via the resistors 9A, 9B at phase θ ₀ .
Continue to supply until nearby.

During the period when this base current is supplied, the DC output of the full-wave rectifier 2 is applied to the collector winding 6C of the output transformer 6 via the inductance 7, and the base feedback winding 6B of the output transformer 6 acts. As a result, transistors 8A and 8B alternately open and close to start oscillation, and the output transformer 6
A high frequency AC voltage as shown in FIG. 2B is generated in each winding.

At this time, the electrodes 5A and 5B of the discharge lamp 5 are preheated by the output voltage of the filament winding 6F provided in the output transformer 6. However, the secondary winding 6S
Since the voltage applied to both ends of the discharge lamp 5 is insufficient to cause the discharge lamp 5 to start discharging, the discharge lamp 5 is not lit yet.

After preheating of the electrodes 5A and 5B is started,
After a predetermined period of time has elapsed, the voltage charged to the capacitor 24 of the timer device 20 of the control device 4 through the resistor 23 exceeds the Zener voltage of the Zener diode 25. For this reason, the thyristor 19 receives a continuous trigger signal via the diode 26, so the thyristor 19 is conductive over almost the entire period of the AC power supply 1. Therefore, the transistors 8A and 8B of the inverter 3 also operate correspondingly, and each winding of the output transformer 6 has a third
A voltage as shown in Figure C is generated. At this time, the electrodes 5A and 5B of the discharge lamp 10 have already been sufficiently preheated, and the discharge lamp 5 is lit.

In this way, the discharge lamp 5 is turned on, but when the inverter 3 oscillates for a period from θ ₁ to θ ₀ shown in FIG. The preheating voltage is applied to electrodes 5A and 5B.
When the voltage is set to a voltage sufficient for preheating, the operation of the timer device 20 is completed and the inverter 3 oscillates for almost the entire period of the AC power supply 1, as shown in FIG. Preheating winding 6 when lit
The voltage generated at F also lasts for almost the entire period of the AC power supply 1, and becomes excessive as a preheating voltage for the electrodes 5A and 5B, resulting in sudden damage to the electrodes 5A and 5B.

The present invention aims to eliminate the above-mentioned drawbacks, and provides an apparatus that can optimally preheat a discharge lamp in either the preheating state or the lit state.

Hereinafter, the details of the present invention will be explained according to Examples. FIG. 3 is a circuit diagram showing one embodiment of the present invention, and FIG. 4 is an explanatory diagram of the operation of the present invention. In FIG. 3, when describing the configuration, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted, and the parts different from FIG. 1 will be mainly described. As is clear from a comparison between FIG. 3 and FIG. 1, the chiyoke coil 11 and capacitor 10 in FIG. A line 6F is provided on the output side of the leakage transformer, and a capacitor 10 is connected in parallel with the collector winding 6C of the output transformer 6.

Next, detailed operation will be explained. First, when AC power is supplied, a voltage as shown in FIG. 4A is supplied to the inverter 3 via the full-wave rectifier 2, similar to the conventional device shown in FIG. Further, a predetermined voltage is also generated in the transformer 13 of the control device 4, and a full-wave rectified pulsating DC voltage is supplied from the full-wave rectifier 14. The resistor 15, the capacitor 16, and the trigger element 17 operate in the same manner as a well-known phase control pulse generator, and are triggered at a predetermined phase every half cycle of the AC power source 1, for example at the phase indicated by θ ₁ in FIG. 4A. Generates a pulse. For this reason, switch element 19
(comprised of a thyristor here) conducts at phase θ ₁ and continues to supply base current to transistors 8A and 8B, which are switching elements, through resistors 9A and 9B until near phase θ ₀ . Therefore, the inverter operates on the same principle as the conventional device shown in FIG. 1, and a high frequency voltage as shown in FIG. 4B is generated in each winding of the output transformer 6.

As is clear from FIG. 4B, the output of the inverter during startup is longer than the period T3 during which the high-frequency AC voltage is generated by the inverter.
It has stopped repeatedly over 4 days.

At this time, the electrodes 5A and 5B of the discharge lamp 5 are connected to the filament winding 6 provided on the output side of the output transformer 6.
It is preheated by the output voltage of F. However, the voltage applied from the secondary winding 6S to both ends of the discharge lamp 10 is insufficient to cause the discharge lamp 5 to start discharging, so the discharge lamp 5 does not light up.

When a predetermined period of time has elapsed after the preheating of the electrodes 5A and 5B was started, the voltage charged to the capacitor 24 of the timer device 20 of the control device 4 via the resistor 23 is applied as in the conventional device shown in FIG. , exceeds the Zener voltage of the Zener diode 25. Therefore, since the thyristor 19 receives continuous trigger signals via the diode 26, the AC power supply 1
is conductive for almost the entire period of the inverter 3.
Since the transistors 8A and 8B also operate in accordance with this, a voltage as shown in FIG. 4C is generated in each winding of the output transformer 6. At this time, the electrodes 5A and 5B of the discharge lamp 5 have already been sufficiently preheated, and the discharge lamp 10 is lit. When the discharge lamp 10 is lit, a current as shown in FIG. 4D flows through the discharge lamp 10. At this time, there is a period _T1 from phase θ ₀ to θ ₂ in which no current flows to the discharge lamp 10, but this is because the voltage of the secondary winding 6S of the output transformer 6 reignites the discharge lamp 5. This corresponds to the period until sufficient voltage is reached. At this time, a voltage as shown in FIG. 4E is generated in the secondary winding 6S of the output transformer 6. In other words, due to the action of the leakage transformer, the period T ₁ when no current is flowing through the discharge lamp 5 corresponds to the voltage at no load, resulting in a high voltage, but during the period T 2 when current is flowing through the discharge lamp 5, the voltage is _high. During the period, the terminal voltage of the discharge lamp 5 becomes lower than in the no-load state, and the effective value also becomes lower. Further, since the filament winding 6F is also provided at the output value of the output transformer 6, its voltage is similar to the voltage generated in the secondary winding 6S, and the filament winding 6F of the conventional device shown in FIG.
By setting the preheating start phase θ ₁ and the number of turns of the filament winding 6F shown in FIG.
It can be optimized even when the lighting is on.

In the embodiment shown in FIG. 3, the period during which the high frequency AC voltage is generated in the output transformer 6 of the inverter 3 is set to be around the phase θ ₁ to θ ₀ shown in FIG. 3A. However, it is also possible to set this to a period in which the instantaneous value of the voltage of the AC power supply 1 is low, such as from phase θ ₁ to θ ₂ , and this embodiment is shown in FIG.

In FIG. 5, when the AC power supply 1 is applied to the transformer 13 of the control device 4, the transistor 28 is turned off during a period when the instantaneous value of the voltage of the AC power supply 1 is low, and the switch element 19 (here (consisting of transistors) is made conductive to supply current to the resistors 9A and 9B of the inverter 3. In this case as well, the timer device 20 continuously turns on the transistor 19 and continuously operates the inverter 3 to light the discharge lamp 5 after a predetermined period has elapsed.

In the above explanation, the DC voltage supplied to the inverter 3 is a full-wave rectified pulsating current. Considering the voltage that has been full-wave rectified by the rectifier 2 and the state shown in FIG. 6A, it is clear that the device of the present invention can be applied.

Furthermore, even if the DC voltage supplied to the inverter 3 is smoothed by connecting a capacitor to the output terminal of the full-wave rectifier 2 as shown in Fig. 3, the DC voltage supplied to the inverter 3 may be smoothed as shown in Fig. 6 (b). A similar effect was obtained by setting the period T and the output generation period _T1 of the inverter 3. In this case, the control device 4 is provided with an oscillation circuit that generates an appropriate period T and an oscillation circuit that generates an appropriate period T.
A monostable multivibrator or the like may be used to set T ₁ .

In the embodiment of the present invention, the electrodes 5A, 5 of the discharge lamp 5
As a device for preheating B, this was done using a filament winding 6F provided on the output side of an output transformer 6 composed of a leakage transformer, but an impedance such as an inductance or a capacitor may be connected in series with the filament winding 6F. Although it is a matter of course, in a device as shown in FIG. 3 which is equipped with a resonant circuit and performs self-oscillation, it is easier to appropriately set the preheating voltage of the electrodes 5A and 5B by using a capacitor as an impedance.

In addition, as shown in Figure 5B, the inverter 3
In cases where a smoothed DC voltage is supplied to the discharge lamp 5, setting the voltage applied to both ends of the discharge lamp 5 near the limit value so that discharge starts when the electrodes are preheated will help in starting the lamp. At times, the discharge lamp starts lighting when the electrodes are preheated by continuing the operation as shown in FIG. 5B. In such a case, the control device 4 may detect the current of the discharge lamp 5 instead of using the timer device 20 to perform the same operation.

In the above description, the case where there is one discharge lamp is shown, but it goes without saying that the invention can be similarly applied to the case where there are two or more lamps.

As described above, according to the device of the present invention, a cold start can be avoided when starting a discharge lamp, and furthermore, it is possible to set the preheating voltage of the electrode to an optimal value both at the time of starting and when lighting, and at the same time, when performing preheating, it is possible to This has the advantage that voltage loss associated with switching operations by the switching elements of the inverter can be reduced.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the configuration of a conventional device; Figure 2 is a circuit diagram showing the configuration of a conventional device;
The figure is an explanatory diagram of its operation, FIG. 3 is a circuit diagram showing the configuration of one embodiment of the device according to the present invention, and FIG.
FIG. 5 is a diagram showing the configuration of another embodiment of the present invention, and FIG. 6 is an explanatory diagram of the operation of the device shown in FIG. In the figure, 1 is an AC power supply, 2 is a full-wave rectifier, 3 is an inverter, 4 is a control device, 5 is a discharge lamp, 5A, 5B are electrodes, 6 is an output transformer, 6F
is a filament winding. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 an inverter comprising a switching element and converting power supplied from a DC power source into high-frequency AC power; a discharge lamp having a preheating electrode heated and lit by the output of the inverter; a control device that repeatedly stops the output for a period longer than the generation period of the high-frequency AC voltage by the inverter and preheats the electrodes before starting lighting of the discharge lamp, and the output means of the inverter is a leakage transformer. A discharge lamp lighting device comprising: a filament winding for preheating electrodes of the discharge lamp; and a filament winding for preheating electrodes of the discharge lamp provided on the output side of the leakage transformer.