JPH0253920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a discharge lamp lighting device for starting and lighting a discharge lamp such as a fluorescent lamp using a high frequency inverter circuit.

FIG. 1 shows an example of a conventional discharge lamp lighting device using a transistor inverter. The device includes two feedback windings 2 and 3 in an oscillation transformer 1,
The AC voltage generated in the feedback winding 2 and the feedback winding 3,
Transistors 6 and 7 are alternately turned on and off using a DC voltage obtained by a rectifier circuit consisting of a diode 4 and a capacitor 5 to generate a high frequency voltage and supply power to a load. The power supplied to the inverter is smoothed,
Moreover, if the load is a resistive load, there is no particular problem with such a circuit, but as shown in Fig. When lighting a discharge lamp such as a light lamp, there are the following problems. That is, stable and good oscillation cannot be maintained unless the base current required to drive the transistor increases or decreases in proportion to the increase or decrease in load current, that is, the collector current of the transistor.

For example, if the base current is insufficient with respect to the collector current, the transistor cannot completely shift to the saturation region, causing problems such as abnormal overheating and destruction of the transistor. On the other hand, if the base current is too large, a so-called overdrive state occurs, and undesirable phenomena such as an increase in the peak value of the collector current, generation of noise, and increase in loss occur. In Fig. 1, when observing the collector current and base current when the lamp is lit, they are shown in Fig. 2 a.
and b, and it can be seen that the two waveforms do not match. Note that in FIG. 2, peak currents appearing in the collector current and base current during transistor switching are omitted because they are unnecessary for the explanation. The point at which the collector current reaches its maximum is the point at which the lamp is re-ignited, but after the re-ignition there is a period of approximately constant current followed by a drop. Ignoring the starting resistor 10, the base current source adds the high frequency AC voltage generated in the feedback winding 2 to the DC voltage generated in the feedback winding 3, but the amplitude value of this high frequency AC voltage is They change synchronously and reach a maximum as shown in FIG. 2c at a phase angle of 90° of the high current power supply voltage shown in FIG. 2d. Therefore, the base current reaches its maximum at a power supply phase angle of 90°, as shown in Figure 2b.
It is quite different from the collector current.

Also, it is clear from the figure that the collector current and base current do not match during the period when the power supply voltage is decreasing. Therefore, if the base current is adjusted to the optimum value at any point in time, the base current will be insufficient at other points. Alternatively, there may be an inconvenience that the number of the particles becomes excessive, and as a result, the above-mentioned drawbacks appear.

In order to eliminate the above drawbacks, the present invention focuses on the fact that the lamp voltage waveform is very similar to the transistor collector current waveform, and first obtains an output similar to the lamp voltage waveform, and then obtains the base current from it. This allows the waveforms of the base current and collector current to match, thereby eliminating the above-mentioned drawbacks.

FIG. 3 shows a circuit according to an embodiment of the present invention. In this circuit, a full-wave rectifier 12 is connected to an AC power source 11, its positive side is connected to a common connection point of primary windings 15 and 16 of an oscillation transformer 14 via an inductance 13, and its negative side is connected to a transistor 17, Commonly connected to 18 emitters. An oscillation capacitor 19 is connected between the collectors of the transistors 17 and 18, and an oscillation transformer 14 is connected between both ends of the capacitor 19.
are connected to one end of the primary windings 15 and 16, respectively. The bases of transistors 17 and 18 are connected to both ends of the feedback winding 20 of the oscillation transformer 14 with the polarities shown in the figure, and further, resistors 21 and 22 are connected in series. A full-wave rectifier 24 is connected to another feedback winding 23, and a capacitor 25 is connected to its output side.
The negative side of the capacitor 25 is the full wave rectifier 12
Connect to the negative side of Resistor 2 is connected between the positive side of capacitor 25 and the common connection point of resistors 21 and 22.
Connect 6 in series. Furthermore, one end of the resistor 27 is connected to the common connection point of the resistors 21 and 22, and the other end is connected to the common connection point of the primary windings 15 and 16 of the oscillation transformer 14. A cathode preheating winding 28 of the oscillation transformer 14 is connected to the cathode of a fluorescent lamp 29. Another cathode preheating winding 30 is connected to the other cathode of the fluorescent lamp 29. One end of the secondary winding 31 is connected to either one of the cathode preheating windings 28 , and the other end is connected to either one of the cathode preheating windings 30 .

Here, the primary windings 15 and 16 of the oscillation transformer 14
On the other hand, the feedback winding 20 is wound magnetically densely, and the feedback winding 23, cathode preheating winding 28, 3
0. The secondary winding 31 is wound so as to be magnetically coarse. In addition, the feedback winding 23 and the cathode preheating winding 2
8, 30 and the secondary winding 31 are wound so as to be magnetically dense with each other. These relationships are, for example, as shown in FIG. Winding wire 31
is wound around another E type core 33, and these two E
This can be easily obtained by butting the mold cores 32 and 33 with an air hole 34.

Next, the operation of the above circuit will be explained. AC power supply 11
is rectified by the full-wave rectifier 12 to generate an unsmoothed DC voltage, which causes current to flow through the resistors 27, 21, and 22 to the bases of the transistors 17 and 18. Due to the difference in amplification factor h _FE between transistors 17 and 18, for example, if transistor 17 is turned on first, a voltage is generated in feedback winding 20 that increases the base current of transistor 17. Transistor 17 continues to be ON. On the other hand, no current flows through the base of the transistor 18, which is in an OFF state. The voltage generated in the oscillation transformer 14 oscillates due to the leakage inductance of the oscillation transformer 14 and the oscillation capacitor 19. Therefore, after a certain period of time, the feedback winding 2
The polarity of the voltage at 0 is reversed, and now transistor 1
Current flows through the base of transistor 18, and transistor 18
ON and transistor 17 turns OFF. In this way, oscillation begins. The voltage generated in the feedback winding 23 at the same time as the oscillation starts has a waveform as shown in FIG. The waveform shown in FIG. 5b is obtained by cutting off the waveform. This contains some high frequencies, but for practical purposes. It does not interfere with the actions listed below. This voltage is resistor 26,2
The current is supplied to the bases of transistors 17 and 18 via transistors 1 and 22, and can sufficiently supply the base current necessary for lighting the lamp. On the other hand, the fluorescent lamp 29 is turned on by the voltage generated in the cathode preheating windings 28, 30 and the secondary winding 31. Due to the above-mentioned magnetic density relationship, the feedback winding 23 is now connected to the secondary winding 3.
The same waveform as the lamp voltage waveform generated in 1 appears. This voltage waveform is shown in FIG. 5c. This voltage is rectified by diode 24 and capacitor 2
5, the high frequency components are removed, resulting in the waveform shown in FIG. 5d. This voltage supplies most of the base current to transistors 17 and 18 through resistors 26, 21 and 22. This base current waveform is naturally similar to that in FIG. 5d. On the other hand, the collector current flowing through the transistors 17 and 18 has a waveform as shown in FIG. 2a, which is very similar to the voltage waveform generated in the capacitor 25. In other words, the lamp is not lit during the period when the AC power supply voltage is low, and as a result, the collector high current also decreases, but the base current also decreases in the same way. The current also increases rapidly, and after that, the collector current remains constant until the power supply voltage drops and the lamp goes out, but the base current also remains approximately constant. Since the base current is actually added to this by the AC component generated in the feedback winding 20, the matching between the collector current and base current waveforms will be slightly worse, but the voltage ratio generated in the feedback windings 20 and 23 should be adjusted appropriately. If selected, there will be few practical problems.

Taking advantage of the fact that the lamp voltage waveform is very similar to the collector current waveform, a voltage proportional to the lamp voltage waveform is generated, and the voltage obtained by removing the high frequency component can also be used as the base current supply source. As a result, the waveforms of the base current and collector current match well over the entire lighting period, which eliminates excessive overdrive and insufficient drive current, and eliminates the above-mentioned drawbacks.

FIG. 6 shows a part of a circuit diagram of another embodiment of the present invention. The same parts as in FIG. 3 are given the same reference numerals. This is done by winding a third feedback winding 32 around the oscillation transformer 14, rectifying the voltage generated here with a diode 33 and smoothing it with a capacitor 34, and adding the voltage that is similar to the lamp voltage waveform to the base current source. This prevents the base current from becoming insufficient before and after the lamp goes out. That is, during the period when the base current is low before and after the lamp goes out, the base current may become almost insufficient compared to the collector current. In order to prevent this, if the resistor 26 is made small, the base current increases uniformly over the entire period, which is undesirable. However, if the structure is configured so that some DC component is superimposed, the base current increases during the period when the base current is low. It has the advantage of being able to solve the problem of base current shortage and having almost no effect on the increase in base current during periods when the base current is large, thereby allowing for good oscillation over the entire period.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional discharge lamp lighting device, Figure 2 is a waveform diagram of each part showing its operation, Figures 3 and 6 are circuit diagrams of an embodiment of the present invention, and Figure 4 is a diagram of the present invention. A structural diagram of the oscillation transformer of the invention, FIG. 5 is a waveform diagram of each part showing the operation of the invention. In Fig. 3, 11... AC power supply, 12, 2
4... Rectifier circuit, 14... Oscillation transformer, 17,
18...Transistor, 20, 23...Feedback winding.

Claims (1)

[Claims] 1. An AC power source, a rectifier circuit that rectifies the AC power source and outputs a non-smoothed DC voltage, a constant current transistor inverter that converts the output of the rectifier circuit into a high frequency, and power is supplied by the constant current transistor inverter. A discharge lamp lighting device comprising a discharge lamp, wherein the constant current type transistor inverter is driven by a voltage obtained by rectifying a voltage proportional to the instantaneous voltage of the discharge lamp and removing high frequency components. Characteristic discharge lamp lighting device.