JPH0440838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lighting device for lighting a discharge lamp at high frequency.

[Conventional technology]

In today's world where people are clamoring for energy conservation, the wave of energy conservation is also hitting the lighting field, and efforts are being made to reduce power consumption.

Techniques for reducing power consumption in lighting include (1) increasing the efficiency of devices by increasing the luminous efficiency of light sources, reducing power loss in lighting devices, and increasing fixture efficiency; (2) lighting design;
Three methods are being considered: (3) systematic operational management using software such as lighting control, and (3) increasing so-called visual efficiency, such as improving the sense of brightness. Among these, improving device efficiency is the basis of power saving and is one of the most important factors.

Fluorescent lamps, which are originally high-efficiency light sources, can be said to be a light source suitable for the energy-saving era, but power-saving lamps have been developed and put into practical use with the aim of further improving their own luminous efficiency. On the other hand, there are ways to reduce the power loss of the ballast as a way to save power in lighting devices, such as changing the material of the conventional ballast made of iron and copper to save energy and stabilize the lamp current at commercial frequencies. There are hybrid electronic ballasts that replace some of the impedance and starting/maintaining circuits with semiconductors, but there is a limit to how much power loss can be reduced.

Against this background, high-frequency lighting of fluorescent lamps has attracted particular attention in recent years as it has the above-mentioned two power-saving effects. When a fluorescent lamp is lit at high frequency, the luminous efficiency of the lamp is approximately 10 to 20 times higher than when lit at commercial frequency.
Although it has been known for a long time that the lighting device has a % increase, it has been limited to only some special applications due to technical problems and cost performance of the lighting device. However, with recent advances in semiconductor technology, high voltage and high reliability power transistors in particular have been developed, and high frequency magnetic core materials have been improved, increasing the possibility of realization.

As a conventional example that focuses on this point, a discharge lamp high-frequency lighting device using a constant current type push-pull transistor inverter as shown in FIG. 1 is known. To explain this with reference to the figure, 1 is an AC power supply, 2 is a noise filter, 3 is a starting circuit, 4 is an abnormality stop circuit, and 5 is a discharge lamp. First, the commercial AC output from the AC power supply 1 is rectified by the diode bridge 6. Normally, a smoothing electrolytic capacitor is connected after this, but with the exception of this, a high power factor of over 90% is achieved by operating with pulsation. This pulsating voltage is applied to the primary winding 11 of the inverter transformer 10 via the constant current inductor 7 and transistors 8 and 9. Primary winding 11
A capacitor 12 is connected to both ends of the capacitor 12, forming a parallel resonant circuit. The base of the transistor is connected to the feedback winding 13 of the inverter transformer to perform an oscillation operation due to the feedback action, and a base current is supplied by bias resistors 14, 15, 16, and 17. 18 is the base drive winding,
Together with the diode 19 and the capacitor 20, it forms a low voltage supply circuit for the base drive current, which makes the base current appropriate and reduces loss due to the base drive resistance. When the transistors 8 and 9 alternately turn on and off due to the feedback action of the winding 13, a sinusoidal AC voltage is generated in the winding 11. On the other hand, the collector current of the transistor becomes a trapezoidal waveform due to the effect of the constant current inductor 7, and the peak current becomes small, so V _CE ( _sat )
The loss caused by this will be reduced. Also, due to parallel resonance,
The collector voltage becomes a sine wave and the collector DC conversion circuit switches at zero, so the switching loss is very small.

[Problem to be solved by the invention]

However, on the other hand, the above device includes commercial ripples in the output, which not only does not improve the luminous efficiency of the fluorescent lamp but also causes flickering. Furthermore, since an isolation transformer is used, primary-secondary coupling becomes a problem, and depending on the structure, there may be considerable loss. Furthermore, since a part of the secondary winding is always connected to the fluorescent lamp filament, a filament current flows even when the lamp is lit, causing heat loss and reducing efficiency.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a high-frequency discharge lamp lighting device with higher efficiency and no flickering of the discharge lamp.

[Means to solve the problem]

This purpose, according to the present invention, is to convert the output of an AC power supply into DC using a DC conversion circuit, further convert it into high frequency using a frequency converter, and transmit the high frequency into a series resonant circuit consisting of a capacitor and a reactor connected to the discharge lamp. In the device for lighting the discharge lamp by supplying a current, the DC conversion circuit includes a rectifier circuit that full-wave rectifies the AC from the AC power source side, a reactor connected in series to the rectifier circuit, and a switching element connected in parallel. The chopper circuit consists of a chopper circuit that chops a full-wave rectified voltage, and a smoothing circuit consisting of a diode and a capacitor that smooths the chopped voltage into a DC voltage. This is accomplished by having pulse control means that can increase or decrease the smoothing voltage to the converter.

[Effect]

Therefore, in the discharge lamp high-frequency lighting device according to the present invention, the input full-wave rectified voltage is directly stepped and smoothed by using a series conversion circuit, so the commercial impedance seen from the power supply side becomes high and the power is increased. In addition to improving efficiency, ripples are extremely small, eliminating flickering from discharge lamps connected to subsequent stages. Furthermore, since the frequency is high, the capacitance of the capacitor used for smoothing is small, making the smoothing circuit compact. Furthermore, by varying the conduction period of the switching element of the chopper circuit, the magnitude of the DC voltage can be freely changed, making it possible to steplessly change the dimming in the discharge lamp, and also to Capacitive fluorescent lamps can also be lit.

〔Example〕

Hereinafter, the configuration of the present invention will be explained with reference to the embodiment circuit shown in FIG.

First, 21 inputs a DC power source to a DC conversion circuit 23 via a noise filter 22 . The DC conversion circuit 23 includes, from the input side, a rectifier circuit consisting of a diode bridge 24, a chopper circuit consisting of a reactor 25, a transistor 26, and a pulse control means 27 for controlling on/off of the transistor 26, a diode 28, and a capacitor 29. It consists of a smoothing circuit.

A frequency converter 32 consisting of an inverter circuit using, for example, transistors 30 and 31 as switching means is connected to the next stage of the DC conversion circuit 23, and a series resonant circuit consisting of a capacitor 33 and a reactor 34 is connected to the output side of the frequency converter 32. is configured. That is, a saturation transformer 35 is inserted in series with this series resonant circuit to generate a secondary voltage according to the resonant current, thereby turning the transistors 30 and 31 on and off alternately. This causes series resonance to continue.

A discharge lamp 36 is energized across the capacitor 33 constituting the series resonant circuit, and is turned on with this resonant voltage. Also a pair of filaments 3
Diodes 39 and 40 are connected to both ends of the capacitor 33, with their polarities facing each other, so that filament currents flow alternately. Capacitors 41 and 42 connected in parallel to diodes 39 and 40, respectively, act as circuit protection means when the filament is disconnected or when an abnormal voltage occurs. Furthermore, diodes 43 and 44 are connected for freewheeling, and a capacitor 45 with a relatively large capacity is connected for damper.

Next, the operation of the apparatus configured as described above will be explained using the operation waveforms shown in FIG.

In FIG. 3, a is the waveform after full-wave rectification, b is the chopper waveform, c is an enlarged view of waveform b, d is the smoothed DC voltage waveform, and e is the output waveform of the series resonant inverter at both ends of the discharge lamp 36. Shows waveform.

The output of the AC power source 21 is passed through a noise filter 22 and subjected to full-wave rectification by a diode bridge 24 as shown in FIG. 3a. The full-wave rectified DC voltage is transferred to the transistor 26 as shown in b to c of the same figure.
Energy is stored in the reactor 25 when conduction occurs,
Chopping is performed using the chopping circuit that releases electricity when the circuit is cut off. Furthermore, connect this to diode 28 and capacitor 2.
The voltage is smoothed by a smoothing circuit consisting of 9 to obtain a DC voltage as shown in d of the same figure. According to the above-mentioned DC conversion circuit, the input full-wave rectified voltage is directly chopped and then smoothed, so the commercial impedance seen from the power supply side increases, the power factor improves, and ripples are extremely small. Flickering from discharge lamps connected to the subsequent stage is eliminated. Furthermore, since the frequency is high, the capacitance of the capacitor 29 is small, making the smoothing circuit small and inexpensive. Furthermore, by varying the conduction period T1 of the transistor 26, the magnitude of the direct current voltage DC can be freely changed, making it possible to steplessly change the dimming of the discharge lamp, and also making it possible to change the dimming of the discharge lamp steplessly. Fluorescent lights can also be turned on. In other words, by lengthening the conduction period T1, the magnitude of the direct current voltage DC increases, and as this DC increases, the frequency of the frequency converter increases (described later), the current to the discharge lamp increases, and the current to the discharge lamp increases. Brightness can be increased. On the other hand, the conduction period T
By shortening 1, the magnitude of the DC voltage DC
As the DC decreases, the frequency of the frequency converter decreases (described later), the current flowing to the discharge lamp decreases, and the brightness of the discharge lamp decreases. These can be freely performed steplessly by setting the conduction period. In addition, since the chopper circuit is used to smooth the full-wave rectified voltage and increase the frequency (Figure 3 b), a very stable DC voltage (Figure 3 d) can be obtained, and the high frequency lighting can be easily achieved using only a frequency converter. Luminous efficiency can be improved by approximately 10% compared to those that do.

Next, a frequency converter that is supplied with the output of the conversion circuit and converts it into a high frequency will be explained together with a series resonant circuit.

First, when starting the discharge lamp 36, the transistors 30 and 31 as two switching means are not completely balanced in the above circuit, so when a signal is output from the starting circuit 46 to the base of the transistor 31, the transistor 31 becomes conductive. A current flows through the capacitor 45, the diode 39, the capacitor 33, the filament 38, the reactor 34, the saturation transformer 35, and the collector and emitter of the transistor 31. Then, since the base of the transistor 31 is connected to the secondary winding 47 of the saturation transformer 35, a self-excitation operation is performed. On the other hand, the voltage induced in the secondary winding 48 by the saturation transformer 35 is in the direction of cutting off the transistor 30, so it is kept off. Thereafter, as the collector current of the transistor 31 increases steadily, the magnetic flux generated in the saturation transformer 35 also increases with time. However, the magnitude of the magnetic flux generated in the transformer 35 reaches a ceiling at the saturation magnetic flux and does not increase any further. Therefore, the secondary voltage of the saturation transformer 35 is no longer induced, and the transistor 31 is turned off. After that, the current stored in the series resonant circuit follows the decreasing waveform, and the current flowing through the freewheel diode 43 decreases. Next, when this current changes in the opposite direction due to the action of the series resonant circuit, the transistor 30 turns on in the same way, and the transistor 30, which is composed of the saturation transformer 35, the reactor 34, the diode 40, the capacitor 33, the filament 37, the capacitor 45, and the transistor 30, turns on. A current is passed through a closed circuit. When the discharge lamp 36 is started, current only flows through the filament of the discharge lamp, and since the filaments, that is, the discharge lamp are in a high impedance state, the current flowing between the filaments of the discharge lamp is extremely small.

In this way, the transistors serving as the switching means are alternately turned on and off, operating as a series resonant inverter to generate a high-frequency AC voltage, and the discharge lamp 36 preheats the filament by the current flowing through the capacitor 33. After this warming-up, discharge starts.

Next, when the discharge lamp 36 lights up, the filament 3
A discharge current flows between 7 and 38, and most of the current flowing through the capacitor 33 is diverted to the discharge lamp 36.
At this time, the resistance between the filaments 37 and 38 can be considered to be a pure resistance R, and the resistance r of the filaments 37 and 38 itself is extremely small and can be ignored compared to the resistance R between the filaments 37 and 38, so in terms of an equivalent circuit, the capacitor A resistor R is connected in parallel to the reactor 33, and this parallel circuit is connected in series to the reactor 34. By lighting the discharge lamp, the current flowing to the capacitor 33 also flows between the discharge lamps, and accordingly, the voltage across the discharge lamp and the saturation point of the saturation transformer change from the state at the time of starting. Since the operating method of the frequency converter 32 is the same, a stable load current flows after lighting, and stable lighting is performed.

In such a frequency converter, the on/off speed of the transistors 30 and 31 is determined by the induced voltage from the saturation transformer 35. That is, as the DC voltage CD from the DC conversion circuit 23 increases, the collector currents of the transistors 30 and 31 increase accordingly, and the magnetic flux generated in the saturation transformer 35 increases. As a result, the time for the saturation transformer 35 to reach a plateau with the saturation magnetic flux is accelerated, the induction and extinction of the secondary voltage is accelerated, the on/off of the transistors 30 and 31 is accelerated, and the frequency becomes higher. Conversely, when the DC voltage DC from the DC conversion circuit 23 becomes low,
Accordingly, the collector currents of the transistors 30 and 31 decrease, and the magnetic flux generated in the saturation transformer 35 decreases. As a result, the time for the saturation transformer 35 to reach a plateau with the saturation magnetic flux is delayed, the induction and extinction of the secondary voltage is delayed, the on/off of the transistors 30 and 31 is delayed, and the frequency is lowered. In this way, when the frequency is increased, the current to the discharge lamp is increased and the brightness of the discharge lamp is increased, and when the frequency is decreased, the current to the discharge lamp is decreased and the brightness of the discharge lamp is lowered. That is, the frequency of the frequency converter changes in accordance with the variation of the DC voltage from the DC conversion circuit 23, and the brightness of the discharge lamp changes accordingly, allowing stepless brightness adjustment.

Furthermore, at both ends of the series resonant capacitor 33,
Since the discharge lamp 36 serving as a load is connected, an alternating current voltage almost like a sine wave is applied, improving luminous efficiency. Additionally, when starting a discharge lamp, a preheating current for the filament and a high discharge voltage are required.
Since the discharge lamp has a high impedance when starting, the current flowing through the discharge lamp is extremely small, and pure series resonance between the capacitor 33 and the reactor 34 generates high current and voltage, making it easy to start the discharge lamp. . Therefore, instantaneous lighting is possible.

In addition, diodes 39 and 40 are connected to both ends of the filaments 37 and 38, and current is passed through the filaments alternately to reduce the loss by half, which has the effect of reducing filament heat loss, especially when the lighting is stable. .

Furthermore, since the load of the transistors 30 and 31 is a resonant current, no reverse recovery current flows when the transistors are turned on, so that the loss is extremely small.

In addition, in the embodiment circuit shown in FIG. 2, by connecting a plurality of frequency converters from the DC converter circuit in parallel, it is possible to simultaneously light discharge lamps having different ratings. Coupled with the stepless dimming effect of the discharge lamp by varying the conduction period of 26, remarkable effects are expected in home indoor lighting (for example, chandeliers, etc.) where various versatility is required.

〔Effect of the invention〕

As is clear from the above description, according to the present invention,
The output of the AC power supply is converted to DC using a DC conversion circuit, and then converted to high frequency using a frequency converter.
A chopper circuit that chops a full-wave rectified voltage to the DC conversion circuit of a device that lights the discharge lamp by supplying the high frequency to a series resonant circuit consisting of a capacitor and a reactor connected to the discharge lamp, and a chopper circuit that smooths the chopped voltage. Equipped with a smoothing circuit consisting of a diode and a capacitor that converts the voltage into a DC voltage, the input full-wave rectified voltage is directly chopped and smoothed, increasing the commercial impedance seen from the power supply side and improving the power factor. With,
Since the ripple is extremely low, flickering of the discharge lamp connected to the subsequent stage is eliminated. Also, because the frequency is high, the capacitance of the smoothing circuit capacitor becomes smaller.
The smoothing circuit can be made small and inexpensive. Furthermore, by varying the conduction period of the switching element of the chopper circuit, it is possible to freely change the magnitude of the DC voltage, making it possible to steplessly change the dimming of the discharge lamp, and also to adjust the voltage at high tube voltages. Capacitive fluorescent lights can also be lit. In addition, since the chopper circuit smoothes the full-wave rectified voltage and increases the frequency, an extremely stable DC voltage can be obtained, and the luminous efficiency is approximately 10 %, and an extremely efficient discharge lamp lighting device can be constructed relatively easily, which has an extremely large effect industrially.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional discharge lamp high-frequency lighting device, FIG. 2 is a circuit diagram for explaining an embodiment of the present invention, and FIG. 3 is a waveform diagram of each part for explaining the present invention. 21: AC power supply, 23: DC conversion circuit, 30,
31: Transistor, 32: Frequency converter, 3
3: Capacitor, 34: Reactor, 35: Saturation transformer, 36: Discharge lamp.

Claims (1)

[Claims] 1. A frequency converter consisting of a DC conversion circuit connected to an AC power supply and converting the output of the AC power supply into DC, and an inverter circuit connected to the output side of the DC conversion circuit and converting the output from the DC conversion circuit into a high frequency. , a series resonant circuit consisting of a capacitor and a reactor connected to the output side of the frequency converter;
A discharge lamp connected in parallel to a capacitor of the series resonant circuit, and a device for supplying the high frequency to the discharge lamp and the series resonant circuit to light the discharge lamp, wherein the DC conversion circuit is connected to an AC power supply. From the side, there is a rectifier circuit that performs full-wave rectification of alternating current, a chopper circuit that chops the full-wave rectified voltage using a reactor connected in series with the rectifier circuit, and a switching element connected in parallel, and a chopper circuit that smooths the chopped voltage. A smoothing circuit is formed in order of a diode and a capacitor for generating a DC voltage, and the chopper circuit is a pulse control means that can increase or decrease the smoothed voltage to the frequency converter by varying the conduction period of the switching element. A high-frequency lighting device for a discharge lamp, comprising: