JPS6057675B2 - discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device that prevents the flickering phenomenon of a discharge lamp in a low temperature environment, for example.

As a conventional discharge lamp lighting device, there is a transistor inverter type discharge lamp lighting device in which a transistor inverter is connected to the output end of a full-wave rectifier that rectifies a commercial AC power source via a constant current reactor.

This transistor inverter type discharge lamp lighting device alternately switches a pair of transistors to generate a high frequency voltage on the secondary side of an output transformer, and uses this voltage to light the discharge lamp. It is known that in order to increase the input power factor in this discharge lamp lighting device, it is sufficient to rectify the AC power source and then use a pulsating voltage to light the lamp without smoothing it. However, when lighting a discharge lamp using such a pulsating current voltage, the discharge lamp repeats re-ignition → lighting and extinguishing due to changes in the instantaneous value of this AC power supply voltage, so that the collector current of the pair of transistors increases. The envelope has a trapezoidal wave shape as shown in FIG. On the other hand, the power supply waveform for supplying base current to the pair of transistors in order to flow this collector current has a waveform as shown in FIG. If this power source is applied to the base via a resistor and a base current is caused to flow, the base current becomes excessive at a phase near π/2 of the AC power source, causing the transistor to generate heat, which may make it impractical. In order to solve this problem, a resistor is inserted between the diode connected to one end of the feedback winding and the base resistor connected to the base terminal of the pair of transistors. A constant voltage diode is inserted between the resistor and the other end of the feedback winding, and the power supply waveform for supplying the base current is made similar or similar to the waveform of the transistor's collector current, thereby reducing heat generation in the transistor. Can be held low.

The waveform of the collector current of this discharge lamp lighting device has a substantially trapezoidal waveform as shown in FIG. 1, and has a peak when the lamp is re-ignited at phase Nw+ψ. Therefore, since this discharge lamp lighting device requires the most base current during restriking, when the ambient temperature decreases, the DC current amplification factor of the pair of transistors also decreases relatively.

As a result, the base current tends to be insufficient, resulting in a period in which the transistor temporarily stops oscillating. Even if this phenomenon occurs once, the direct current amplification factor increases due to the heat generated by the transistor itself, so that the base current shortage is resolved. However, there is a drawback that the switching operation of the transistor becomes unstable in a transient state from the state of insufficient base current in the re-ignition phase until the state is resolved, so that the oscillation stop period appears and disappears, causing flickering. This invention eliminates the above-mentioned drawbacks and changes the Zener voltage (zε) of the constant voltage diode that shapes the base power supply of the switching transistor into a trapezoidal waveform to the output voltage of the second rectifier in the restriking phase of the discharge lamp load. The maximum value of the output voltage of the second rectifier [VReO(t)] is larger than [VRec(φ)].
- By selecting a range smaller than , the present invention aims to provide a discharge lamp lighting device that can eliminate the lack of base current of the transistor in a low-temperature environment, operate the transistor stably, and prevent the flickering phenomenon of the discharge lamp. It is something.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 3, 1 is an AC power supply, and 2 is a first rectifier, which in the illustrated example is a full-wave rectifier, the output end of which is connected to a transistor inverter 4 via a constant current reactor 3. This transistor inverter 4 constitutes a power source for lighting the discharge lamp 5 and a power source for heating the cathode, and includes a pair of transistors 6, 7, an output transformer 8, capacitors 9, 10,
The second rectifier is composed of a starting resistor 11, resistors 12 and 13, and a diode 15 and a constant voltage diode 16 in the illustrated example. That is, the positive output terminal of the full-wave rectifier 2 is connected to the primary winding 8 of the output transformer 8 via the constant current reactor 3.
a, 8b, and the primary windings 8a, 8
The other ends of each of the transistors b are connected to the collectors of the transistors 6 and 7, and their emitters are collectively connected to the negative output terminal of the full-wave rectifier 2. Further, the base of the transistor 6 is connected to the output side of the constant current reactor 3 via the starting resistor 11, while the base of the transistor 7 is connected to the output side of the full-wave rectifier 2 via the resistor 12 and the constant voltage diode 16 with the polarity shown. Connect to negative terminal. One end of the feedback winding 8c is connected to the positive terminal of a constant voltage diode 16 via a diode 15 and a resistor 13 of the illustrated polarity, and the other end is connected to the negative terminal of the diode 16. Further, a capacitor 10 is connected in parallel to the series connection portion of the feedback winding 8c and the diode 15. Further, the base of the transistor 6 is connected to the positive terminal of the voltage regulator diode 16 via the resistor 14, and one end of the feedback winding 8d is connected to the base of the transistor 6.
The other ends are connected to the bases of transistors 7, respectively. The output transformer 8 also includes cathode heating windings 8e, 8f1 and an output winding 8g.

These cathode heating wires 8e and 8f generate a cathode heating voltage, and the output winding 8g generates a lighting voltage. In this discharge lamp lighting device, when the AC power supply 1 is turned on, a pulsating DC voltage that has been full-wave rectified by the full-wave rectifier 2 is applied to the inverter 4 via the constant current reactor 3.
Therefore, the bases of the transistors 6 and 7 are biased through the starting resistor 11, and the inverter 4 starts oscillating. When the inverter 4 starts operating, a voltage is generated in the feedback winding 8c, and the voltage is rectified by the rectifier 15. The waveform at this time is as shown in FIG. 2, and by applying this voltage to the base bias of each transistor 6 and 7 through the resistor 13, the pair of transistors 6 and 7 are alternately switched and the output transformer 8 A high frequency voltage is generated on the secondary side of the discharge lamp 5, which heats the cathode and discharge lamp 5.
Start lighting. When the discharge lamp 5 starts, this device properly limits the current flowing through the discharge lamp 5 by the leakage inductance of the output transformer 8 to maintain stable lighting. The waveforms of the transistors 6 and 7 are made similar to or similar to the waveforms of the collector currents of the transistors 6 and 7.
The fever is kept low. The waveform of the collector current of this device has a substantially trapezoidal waveform as described above, and has a peak when the discharge lamp 5 is re-ignited at the phase nπ+ψ, so that the ambient temperature decreases. The current amplification factor decreases, a base current shortage occurs in this phase, and the oscillation of the transistor temporarily stops.

As a result, flickering occurs due to unstable operation of the transistors 6 and 7 in a transient state until the base current shortage is resolved due to the heat generated by the transistors 6 and 7 themselves. Therefore, by eliminating this base current shortage, the above-mentioned problems can be solved.

As a result of various experiments, it has been found that this problem can be solved by appropriately selecting the Zener voltage of the voltage regulator diode 16. However, if the supply amount of the base current is increased, the loss in the resistors 12, 13, and 14 will increase, so the larger the resistance value of these resistors, the better, which is contradictory to eliminating the above-mentioned flickering. Therefore, optimal constants must be selected to satisfy both conditions. When the constant is optimally selected in this way, if the constant deviates from the specified range due to a slight condition such as flickering of parts, as mentioned above, an oscillation stop period will occur during the restriking phase and flickering will occur. Conceivable.

For example, assuming that this oscillation stop period is a time Δt as shown in FIG. 4, the voltage across the constant voltage diode 16 decreases by Δν during this period. This can occur regardless of whether the Zener voltage of the constant voltage diode 16 is high or low, and since Δν is determined by the discharge time constant of the capacitor 10, there is no significant difference between the two. Even if the voltage decreases by Δν in this way, the degree of influence is not constant, and clearly the lower the Zener voltage, the greater the influence. Therefore, from the above, during the restriking phase, the voltage regulator diode 1
It has been found that it is desirable to select the Zener voltage of No. 6 as high as possible.

However, unless this Zener voltage is lower than the maximum output voltage of the diode 15 (ReO(t)MaO), the purpose cannot be achieved. Therefore, considering the above two conditions, the Zener voltage ■ZD becomes ■Rec(ψ)≦VZ
By selecting a value within the range of D<VRec(t)Max (where ■ReO(φ) is the output voltage of the diode 15 in the re-ignition phase of the discharge lamp), the DC current of the transistors 6 and 7 in a low-temperature environment can be reduced. It is possible to prevent the flickering phenomenon of the discharge lamp by suppressing the decrease in the amplification factor and stabilizing the operation of the transistors 6 and 7. In particular, the present invention is more effective when applied to a discharge lamp lighting device operated with a pulsating voltage source, such as the embodiment shown in FIG. 3, which uses a full-wave rectified commercial AC power source without smoothing it. It is something.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without changing the gist. In the above embodiment, a commercial AC power source is used as a power source for an inverter in a full-wave rectified and non-smooth state. However, the present invention is not limited to this as a power source; for example, a pulsating wave such as a half-wave rectified wave This effect is particularly evident in the case of extremely high voltage sources.

Further, in the above embodiment, a leakage transformer is used as the output transformer, but the present invention is not limited to this. For example, a current limiting impedance may be simply inserted on the secondary side of the transformer.

As described above, according to the present invention, the Zener voltage (V2c) of the constant voltage diode that shapes the base power supply of the switching transistor into a trapezoidal waveform is changed to the output voltage of the second rectifier in the restriking phase of the discharge lamp load [ VRec(ψ
)] is larger than the maximum value of the output voltage of the second rectifier [VR
By selecting a range smaller than ec(t)MJ, we have created a discharge lamp lighting device that can eliminate the lack of base current of the transistor in a low-temperature environment, operate the transistor stably, and prevent the flickering phenomenon of the discharge lamp. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing the collector current of a transistor in a conventional discharge lamp lighting device, FIG. 2 is a waveform diagram showing the output of the second rectifier in the conventional device, and FIG. 3 is a waveform diagram showing an example of the present invention. The circuit configuration diagram shown in FIG. 4 is a waveform diagram illustrating the operation of the same embodiment. 1... AC power supply, 2... Full wave rectifier,
3... Constant current reactor, 4... Transistor inverter, 5... Discharge lamp, 6,7...
...Transistor, 8h...Output transformer, 8a, 8b...Primary winding, 8c, 8d...
...Feedback winding, 8e, 8f...Cathode heating winding, 8g...Output winding, 9,10...Capacitor, 11...Starting resistance , 12, 13, 14・
...Resistance, 15...Diode, 16.
... Constant voltage diode.

Claims (1)

[Claims] 1. An AC power source, a first rectifier that rectifies this power source,
The two output transformers are energized by the DC output of this rectifier and controlled on and off by the switching transistor.
A self-excited inverter that generates a high frequency output on the next side, a discharge lamp connected to the output end of the inverter and energized by the high frequency output, and a discharge lamp provided in the output transformer of the inverter and connected to the base of the switching transistor A feedback winding that supplies current, a second rectifier that rectifies the output of the feedback winding, and a constant voltage diode that shapes the waveform of the output voltage of the second rectifier into a trapezoidal waveform. The Zener voltage (V_Z_D) of the second rectifier in the restriking phase of the discharge lamp load is [V_R_e_c(■)], and the maximum value of the output voltage of the second rectifier is [V_R_e_c(t)_M_a_x]. When V_R_e_c(■)≦V_Z_D≦V_R_
A discharge lamp lighting device characterized in that the discharge lamp lighting device is selected so as to fall within the range of e_c(t)_M_a_x.