JPH0336279B2 - - 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.

Devices that use inverters to convert DC power into high-frequency waves of several KHz or higher to light discharge lamps such as fluorescent lamps have lower losses than the so-called Chi-Yoke coil type ballasts, which include reactance and have been commonly used. It has become popular in recent years due to its advantages such as low weight and light weight.

By the way, when using an inverter to light a discharge lamp, the output voltage of the inverter is set high enough to ensure that the discharge lamp can be started and lit even under adverse conditions such as low temperatures. The following phenomena were likely to occur.

That is, when the discharge lamp is started, a high voltage is applied to both ends of the discharge lamp simultaneously with the start of preheating of the electrodes. For this reason, a so-called cold start, in which discharge is forcibly started before the electrode has been preheated, is likely to occur, which may cause sudden damage to the electrode.

In order to prevent this cold start, it is a good idea to sufficiently preheat the electrode before starting the discharge, and the inventors previously proposed a device shown in FIG. 1 as a device for realizing this. In the conventional device shown in FIG. 1, 1 is a commercial frequency AC power supply, 2 is a full-wave rectifier, and A is an inverter. Here, it is composed of a self-excited pushable transistor inverter equipped with an output transformer 5. . B is a control device that controls the operation of this inverter A, and includes a timer device C that generates a signal at a predetermined time after the AC power source 1 is turned on. L is a discharge lamp such as a fluorescent lamp, and La and Lb are electrodes.

Note that inverter A includes transistors 3a, 3b,
An output transformer 5 consisting of a collector winding 5N, a base feedback winding 5B, a filament winding 5F, and a secondary winding 5S, an inductor connected to the middle of the collector winding 5N and the output side of the full-wave rectifier 2. 4. Base resistance 6 of the transistors 3a and 3b
a, 6b, a capacitor 5C connected in parallel with the collector winding 5N, and a leakage inductance resonant circuit connected equivalently in series with the secondary winding 5S.

The control circuit B also includes a transformer 7 connected to the AC power supply 1, a full-wave rectifier 8 for rectifying the output of the transformer 7, a diode 9 and a capacitor 10 connected to the output terminal of the full-wave rectifier 8, and a resistor 1.
1, a constant voltage diode 12, a resistor 13, transistors 14 and 16, a diode 15, and a resistor 19, a capacitor 20, a diode 17, and a constant voltage diode 18, which constitute a timer device C.

Next, the operation will be explained. First, AC power supply 1
is supplied to inverter A, full-wave rectifier 2 is supplied to inverter A.
A voltage as shown in FIG. 2A is applied through the . At the same time, a predetermined voltage is also generated in the transformer 7 of the control device B, and a pulsating DC voltage that has also been full-wave rectified is supplied from the full-wave rectifier 8. During a period when the instantaneous value of the voltage of the AC power supply 1 is low, the transistor 14 is turned off by the action of the constant voltage diode 12, and the base current is supplied to the transistor 16 via the diode 15, making the transistor 16 conductive and turning off the inverter A. A current is supplied to the resistors 6a and 6b.

Therefore, inverter A is connected to transistors 3a and 3b.
A veil current begins to flow through the base feedback winding 5B.
As a result of this action, the inverter A performs self-excited oscillation operation as is well known, and an output voltage is generated in each winding of the output transformer 5.

As a result, the power sources La and Lb of the discharge lamp L are preheated. FIG. 2 shows this state, and FIG. 2A shows how the transistor 14 is turned on by the Zener voltage of the voltage regulator diode 12. Above V _REF , the inverter stops outputting, and below this,
The inverter generates an output during the period θ ₁ to θ ₂ .
C indicates a period T ₂ during which the inverter output is stopped and a period T ₁ during which the inverter output is generated, and T indicates the period of each half cycle of the AC power supply 1.

In addition, d is the preheating voltage applied to the electrodes La and Lb,
That is, the filament winding 5 of the output transformer 5
The output of F is shown. At this time, it is clear that the period T ₂ during which the inverter stops outputting can be set by the output voltage of the full-wave rectifier 8 and the Zener voltage of the constant thickness diode 12. After this, the terminal voltage of the capacitor 20 of the timer device C increases,
When the Zener voltage of the constant voltage diode 18 is exceeded, the transistor 16 is continuously supplied with a base current from the resistor 19 via the diode 17, so that the transistor 16 continues to conduct continuously. Therefore, the period _T2 during which inverter A stops outputting is eliminated,
The discharge lamp lights up because it continuously generates output.

In this way, a cold start of the discharge lamp can be prevented. However, in the conventional device shown in FIG. 1, the base current to the transistors 3a and 3b of the inverter A is obtained from the transformer 7 used in the control device B via the diode 9. It had the disadvantage that it required things like this and tended to be expensive. Conventionally, transistors 3a,
As a method of supplying the base current to 3b, a method as shown in FIG. 3 without using the transformer 7 was also known. FIG. 3 shows a conventional device of this type,
This is a device that lights a discharge lamp L using an inverter A, similar to the device shown in FIG.
Since the operation is similar to that shown in the figure, the other parts will be explained. 23a and 23b are resistors that supply a base current for starting the self-excited oscillation operation of the inverter A, so when the AC power supply 1 is turned on, the inverter A starts the self-excited oscillation operation.At this time,
The AC voltage generated in the output transformer 5 is transferred to the auxiliary winding 5.
feedback through K, diode 21 and capacitor 22
rectify with. D is a base power supply circuit. After this, the transistor of inverter A is connected to the resistor 6.
Most of the base current is supplied through a and 6b.
Therefore, for example, the voltage of the commercial AC power supply 1 is
Even if the voltage is high such as 100V or 200V, the base power supply circuit D
The voltage can be set low by using the auxiliary winding 5K, so all the base current can be connected to the resistors 23a and 23a.
23b, compared to the case where the resistor 2
Since it is possible to make the resistance values of 3a and 23b sufficiently large, the resistance values of resistors 23a and 23b as well as 6a and 6
It was possible to reduce losses such as b.

However, in this conventional device, the resistors 23a, 2
In order to reduce the loss of 3b, increase the resistance value.If the resistance value is increased too much, if the voltage of the commercial AC power supply 1 is low or depending on the type of discharge lamp L of the load, it may be necessary to turn on the power supply 1. However, it was found that the inverter was unable to perform normal self-excited oscillation, and a phenomenon occurred in which the discharge lamp could not be lit.

When the power supply 1 is turned on, the filament winding 5F of the inverter A first connects the discharge lamp L and the electrodes.
La and Lb are preheated, and at this time, in their initial state, the preheating electrodes La and Lb have only a small filament resistance of about 1/5 to 1/10 compared to the normal lighting state. For this reason, power supply 1 is turned on,
At the moment inverter A starts oscillating, an excessive rush current momentarily flows from filament winding 5F. However, at this time, the capacitor 22 of the base power supply circuit D does not yet have enough charge stored in the capacitor 22 to supply the transistors 3a and 3b with a base current sufficient to cause this rush current to flow. As a result, the inverter A becomes unable to perform normal oscillation operation, and the abnormal oscillation continues, making it impossible to light the discharge lamp.

This invention attempts to eliminate the above-mentioned drawbacks. That is, by charging the capacitor 10 of the base power circuit B with the necessary charge in advance and then repeatedly starting the operation of the inverter, the inverter can be reliably activated. This is a device that allows self-excited oscillation and prevents cold starts of discharge lamps.

The apparatus according to the present invention will be explained below. FIG. 4 shows an embodiment of the apparatus according to the present invention, and FIG. 5 is a diagram for explaining the operation.

In Fig. 4, 1 is a commercial AC power supply, 2 is a full-wave rectifier, and A is an inverter, which is composed of a self-excited pushable transistor inverter, 5 is an output transformer, and B controls the operation of inverter A. The same reference numerals as the devices in FIGS. 1 and 3 indicate corresponding parts, respectively. L is a discharge lamp such as a fluorescent lamp, and La and Lb are electrodes.
11a and 11b of control device B are resistors, 12 is a constant voltage diode, 13 is a resistor, 14 is a transistor, 18 is a constant voltage diode, 19 is a resistor, 20
are capacitors; 18, 19, and 20 constitute a timer device C; 21 is a diode; 22 is a capacitor; 24 is a diode; 25 is a transistor;
6 is a resistor, 27 is a diode, 28 is a constant voltage diode, and 29 is a transistor 3 of inverter A.
This is a capacitor that supplies charge to the bases of capacitors a and 3b, and its capacitance should be much smaller than that of capacitor 22. Numeral 30 is a transistor serving as a switching element.

In the device configured as described above, when the AC power supply 1 is first turned on, the voltage divided by the resistors 11a and 11b is equal to or higher than the Zener voltage of the constant voltage diode 12, as shown in Fig. 5A. In the phase from θ ₁ to θ ₂ , the inverter A is operated for a period of T ₁ from the phase θ ₁ to θ ₂ , as shown in FIG. Electrode of discharge lamp L
La and Lb are preheated by the output of the filament winding 5F of the output transformer 5. After this, timer device C
The rise in the terminal voltage of the capacitor 20 makes the transistor 25 conductive, so that the terminal voltage of the resistor 11b is almost no longer generated, so that no current flows through the voltage regulator diode 12, and the transistor 14 is always in a non-conducting state. , while the voltage is applied to the capacitor 29, the transistor 30 conducts because the base current flows through the resistor 13.
The charge of the capacitor 29 is supplied to the bases of the transistors 3a and 3b of the inverter A through the resistors 6a and 6b, causing the inverter to self-oscillate. In this manner, when the terminal voltage of the capacitor 20 of the timer device C increases after a predetermined period of time, the inverter A operates continuously and the discharge lamp lights up.

Now, to explain the operation of the device of the present invention in more detail, first, when the AC power supply 1 is turned on, no voltage is generated in the capacitor 22 since no voltage is generated in the auxiliary winding 5K yet. At this time, the capacitor 29 is charged from the full-wave rectifier 2 via the resistor 26, and this capacitor 29 is
A voltage as shown in Figure 5C is reached. That is, after the phase θ ₂ in which the transistor 30 was in a conductive state, the transistor 14 becomes conductive as described above, so the transistor 30 becomes non-conductive, and as shown in _FIG. Thereafter, the terminal voltage increases due to charging until it reaches the Zener voltage _V8 of the voltage regulator diode 28. After this,
When the transistor 14 becomes non-conductive and the transistor 30 becomes conductive at phase θ ₁ , the charge in the capacitor 29 is discharged and the inverter A starts oscillating. This operation is repeated every half cycle of the AC power supply 1, so even if the inverter is not able to perform self-oscillation normally during the first half cycle, the operation of the timer device C is completed. Since the process is repeated during this period, the start of oscillation is ensured. Once the inverter A starts oscillating normally, an output voltage is generated in the winding 5K of the output transformer 5, and since a sufficient voltage is now applied to the capacitor 29 from the capacitor 22, for example, the capacitor 29 The voltage is as shown in Fig. 5(d). As described above, even if the resistance values of the electrodes La and Lb of the discharge lamp L are low in the initial state, by charging the capacitor 29 during the period when the inverter is not operating, the resistor 26 can be set to a high resistance value with less loss. Even if the resistance value is used, the inverter can be reliably operated in normal oscillation.

In the embodiment shown in FIG. 4, a constant voltage diode is connected in parallel with the capacitor 29, but this is connected to the resistor 29.
For reasons such as the high voltage of the power supply connected to 6,
This is effective when the voltage of the capacitor 29 becomes too high, and is unnecessary when there is no risk of voltage rise like this. In addition, in the embodiment, the diode 27 is connected in series with the capacitor 22 to charge the capacitor 29. However, when the capacitance of the capacitor 22 is very large,
By setting the capacitor 29 smaller than this, the resistance value of the resistor 26 can be reduced without reducing the resistance value.
It has the effect of increasing the terminal voltage of the capacitor 29 to the voltage required to start normal oscillation operation, and if the capacitor 22 has a small capacity or the voltage of the power supply connected to the resistor 26 is low, the capacitor 22 may be configured to be charged from the resistor 26. In this case, the capacitor 29 and the diode 27 may be omitted; in this case, the capacitor 2
2 is a capacitor that supplies the base current of transistors 3a and 3b.

Even in configurations other than those shown in the embodiments, the timer device C also operates after a predetermined period of time elapses after the AC power source 1 is turned on.
Any device may be used as long as it generates a necessary signal or reaches a predetermined operating state, and the method of supplying base current to the transistors 3a and 3b of the inverter A is not limited to the method using the transistor 30 shown in the embodiment, for example, When the discharge lamp is turned on after the operation of the timer device C is completed, a voltage as shown in FIG. 5E may be supplied to the resistors 6a and 6b.

Furthermore, in the above explanation, the period T ₁ (5th
(see Figure A) is provided in the phase θ 1 to _{θ 2 ,} which is the period of low instantaneous value, for each half cycle of the commercial AC power supply 1. However, after rectifying the AC power supply 1 with the full-wave rectifier 2, by connecting a smoothing capacitor, etc., the pulsating DC current of the inverter A is changed.
When a continuous DC voltage with little ripple is applied, synchronize it with the AC power supply 1,
It would be nice to set it up in a period like Figure 5 A, but
With a repetition period different from the repetition period of AC current 1,
A similar effect can be obtained by configuring the control device B so as to provide a period T ₁ during which the inverter A generates an output and a period T ₂ during which the inverter A stops outputting.

It goes without saying that this method can also be applied to the case where a phase-controlled power source is used as the AC power source 1 to change the output of the inverter A to dim the discharge lamp L.
In this case, the method for setting the period _T1 during which inverter A generates an output immediately after power is turned on does not have to be the method shown in FIG. 5A.

Inverter A is not limited to the push-pull type transistor inverter using a leakage transformer as an output transformer as shown in the embodiment, but the output transformer has an auxiliary winding equivalent to 5K for supplying the main base current to the switching transistor of the inverter. and a winding 5 for preheating the electrodes of the discharge lamp.
Any self-excited transistor inverter having an F-equivalent part can be used, and it goes without saying that the number of discharge lamps may be two or more instead of one. In other words, in a device that preheats the electrodes of a load discharge lamp by repeatedly operating an inverter through periods of generating output and periods of stopping immediately after the power is turned on, during the period when the inverter's output is stopped, To do this, charge the capacitor with the necessary charge and supply this charge as the base current of the switching transistor of the inverter every time the inverter output is generated and stopped, so that the inverter can operate normally and maintain the specified level. After the time has elapsed, the timer device operates to generate the inverter output.
This is a device that finishes the preheating operation for stopping and lights up the discharge lamp.

As described above, according to the device of the present invention, when the power is turned on and the inverter is about to start operating, even if the resistance of the electrodes of the load discharge lamp is low, the inverter can be reliably operated in normal oscillation mode. It has the advantage of

[Brief explanation of drawings]

1 and 3 are circuit diagrams showing a conventional device, FIG. 2 is an explanatory diagram of its operation, FIG. 4 is a circuit diagram showing an embodiment of the device according to the present invention, and FIG. 5 is an explanation of its operation. It is a diagram. Codes in the figure: 1 is an AC power supply, 3a, 3b are transistors, 5 is an output transformer, 5K is an auxiliary winding, 5
F is a filament winding, A is an inverter, B is a control device, C is a timer device, L is a discharge lamp, La,
Lb is an electrode, and the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A transistor inverter for exchanging power supplied from a DC power supply to high-frequency AC power to light a discharge lamp; and a transistor inverter for lighting a discharge lamp by exchanging power supplied from a DC power supply to high-frequency AC power; The high-frequency alternating current is repeatedly stopped for a period longer than one cycle, and the electrodes of the discharge lamp are preheated by the output of the transistor inverter, and the output of an auxiliary winding provided in an output transformer constituting the transistor inverter is used. In an apparatus including a control device that supplies a main base current to a transistor that performs a switching operation of the transistor inverter during lighting of the discharge lamp, the control device controls the transistor inverter to generate an output when the discharge lamp is started. During the period of suspension,
The electric charge of the capacitor charged from the DC power source via the resistor is supplied to the base of the transistor inverter through a switching element that is opened and closed by the output of the timer device, and the output voltage of the auxiliary winding is rectified to the capacitor. A discharge lamp lighting device characterized by supplying DC voltage via a diode. 2. The discharge lamp lighting device according to claim 1, wherein the DC power source outputs a pulsating DC current obtained by rectifying a commercial AC power source. 3. Where the DC power source is obtained by rectifying a commercial AC power source, the control device is configured to provide a period _T1 during which the transistor inverter generates an output at the time of starting the discharge lamp in synchronization with the commercial AC power source. 2. The discharge lamp lighting device according to item 2.