JPS5880296A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a discharge lamp lighting device.

In the conventional discharge lamp lighting device, as shown in Fig. 1, when a series circuit of transistors TR and TR2 is connected to a DC power source E, a diode drawer is connected to the DC power source E, and a series circuit of transistors TR and TR is connected to a series circuit of transistors TR and TR. Connect so that the polarity is reversed, and then connect the DC power supply EK capacitor C.

Connect the series circuit of C2 and connect the transistors TR□, TR
.

A common connection is made between the connection point of diodes D□ and D2, and a discharge lamp LA, a lead coil L□, and a capacitor C3 are connected in series between this common connection point and the connection point of capacitors C and C2. Connect the circuit, connect a capacitor C4 for forming a preheating circuit between both filaments of the discharge lamp LA, turn on the transistors TR and TR2 alternately with a control circuit CT consisting of an astable multivibrator, and turn on the discharge lamp LA. It is set to preheat and turn on.
In addition, the voltage of the DC power supply E is stepped down by the resistor R, and the driving voltage Elf is reduced by the capacitor C5 and the voltage regulator diode ZD.
7r is obtained to operate the control circuit CT.

In such a discharge lamp lighting device, the circuit current has a different phase relationship depending on whether the discharge lamp LA is discharging or not, as shown in FIGS. 2 and 3. explain. FIG. 12 shows the case where the phase of the current amount is leading with respect to the rectangular wave voltage ., and FIG. 3 shows the case where the phase of the current i is lagging with respect to the rectangular wave voltage .

In the case of FIG. 12, the amount of current is 1.5 times higher than tryslx in the first half of the half cycle in which the rectangular wave voltage C is at a high level. The second half of the current flows through the diode D□ as current R-0, and during the half period when the rectangular wave voltage is at a low level, the first half of the period is when the current flows through the transistor TR2 [current The second half flows through the diode D2RR as the amount of current. , flows as. In this case, the diode
Immediately after the transistor TR2 becomes conductive, the recovery current of the drain current flows steeply through the transistor TR2, and the recovery current of the diode D20 similarly flows steeply through the transistor TR.

The switching loss of TR is large.

In the case of Fig. 3, the amount of current flows during the half period when the rectangular wave voltage is at a high level, and in the first half it flows as current 'Di through the maiode D, and in the second half it flows through the transistor TR. A current i□ flows through the square wave voltage e
In the half cycle in which is at a low level, the first half of the warpage is caused by the diode D, and the electric current fIt amount DJ! The second half flows through the transistor TR.

A current 'TR2 flows through the current 'TR2. In this case, the recovery current of the maiodes D and D2 is very small.

Therefore, when the discharge lamp LA is lit, in order to flow a slow-phase current and reduce switching loss, the series reactance of the cheek coil A/L, capacitor C3, and capacitor C (C2) is changed to inductive KM and , when the discharge lamp LA is not discharging, the capacity of capacitor C4 is reduced to
/L, capacitor C3, capacitor C4, and capacitor C (C,)0 series reactance are selected to be capacitive, and K is set so that phase-advanced current i flows.

However, if the phase-advanced current continues to flow for a long time, for example, if the cathode oxide of the filament of the discharge lamp LA is consumed, the IK transistors TR1 and TR2 may be damaged due to switching loss.

In addition, the DC power supply E is stepped down with a resistor R□, and the capacitor C5
Since the driving voltage E is obtained by the constant voltage diode ZD, if the difference between the voltage of the DC power supply E and the driving voltage E becomes large, the voltage drop across the resistor R becomes large. There was a problem that the power loss was large.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lighting device for a stone discharge lamp that can prevent damage to transistors and reduce power loss.

An embodiment of this invention is shown in FIGS. 4 and 5. That is, this discharge lamp lighting device uses transistor TR, T
Insert the primary winding of the transformer T between the connection point of ~ and the connection point of the diode drawer and DI&, and
The electromotive force of the secondary winding atOIll is rectified by the diode D3 to obtain the driving voltage E of the drive control circuit CT by the constant voltage diode ZDTh and the capacitor +C, and the resistor!
2. Koyden fC6 and switch element (SBS,
SSS) A start circuit ST similar to Q is provided, and the other configurations are the same as those shown in FIG.

Next, the operation will be explained. When a voltage is applied from the DC power supply E, the capacitor C6 of the star 1 circuit ST is charged through the resistor R2, and when the charging voltage of the capacitor tC6 reaches the breakover voltage of the switch element Q, the switch element Q becomes conductive and the transistor A small amount of current is supplied to the base of TR2, making transistor TR2 conductive. TR:/l) When SUF TR2 becomes conductive, the DC power supply E
→ Capacitor C engineering → Capacitor C4 → Chi, - Kukoi Jv
Current flows through the path Ll → capacitor C3 → primary 4 of transformer T → transistor TR2 → DC power supply E. After that, the current flowing from the capacitor C6 to the transistor TR2 through the switch element 01 becomes zero and the transistor TR2 is turned off, generating an electromotive voltage in the transformer T FCH and supplying the drive voltage E□ to the control circuit CTK. do. As a result, the control circuit CT starts operating, and the transistors VST and TR are turned on alternately to light the discharge lamp in the same manner as in FIG.

Thus, this embodiment uses transistor TR.

The discharge lamp LA When the constants are set so that the current i advances in phase when the discharge lamp LA is not lit, or when the cathode oxide of the discharge lamp LA is exhausted, the diode D , the steep recovery current of D2 flows from the DC power supply E to the diode D2. Transistor TR engineering, TR through Dl.

It is possible to prevent the flow of K. In addition, since the drive voltage E is obtained from the induced voltage of the two major windings of the transformer T, the resistor R as in the conventional example is not required by setting the turns ratio of the transformer T uniformly. power loss can be reduced.

Furthermore, unlike the case where the drive voltage is obtained by stepping down the voltage of the AC power source, the number of parts can be reduced.

In addition, a simple inductance element is interposed in place of the transformer TK in FIG.
It may be done in the same manner as shown in the figure; in this case, damage to the transistors TR can be prevented.

As described above, the discharge lamp lighting device of the present invention is as follows.

a series circuit of a DC power source, first and second transistors connected across the DC power source, and a first transistor connected across the DC power source so as to have opposite polarity to the first and second transistors; a series circuit of first and second diodes, and a first and second diode connected between both ends of the DC power supply.
a series circuit of a discharge lamp and a current-limiting element connected by KJI between a connection point of the first and second diodes and a connection point of the first and second capacitors;
An impedance element for forming a preheating circuit connected between both filaments of the discharge lamp, and the w! Jl and 2nd
The transistor includes an inductance connected between a connection point of the transistor and a connection point of the first and second diodes, and a control circuit that turns on the first and second transistors alternately. The second invention has the effect of further reducing power loss.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional discharge lamp lighting device, Figure 2 is a circuit diagram of a conventional discharge lamp lighting device,
(1, c) are the waveform diagrams of each part when the current phase is leading, Figure 3. @, a are the waveform diagrams of various parts when the current is lagging, Figure 4.
The figure is a circuit diagram of an embodiment of the present invention, FIG. 5 is a specific circuit diagram of its main part, and FIG. 6 is a waveform diagram of each part when the current phase advances. E...DC power supply, TR engineering, TRj! ...Transistor, D.

Claims (1)

[Claims] (1) A DC power supply, a series circuit of w, first and second transistors connected across the DC power supply, and a series circuit having opposite polarity to the first and second transistors across the DC power supply. a series circuit of first and second diodes connected to the DC power supply, first and second capacitors connected across the DC power supply, a connection point of the first and second diodes, and the first and second capacitors; a series circuit of a discharge lamp and a current limiting element connected between the connection point of the second capacitor; an impedance element for forming a preheating circuit connected between both filaments of the discharge lamp; and the first and second transistors. and a control circuit that alternately turns on the first and second transistors. (A DC power supply, a series circuit of first and second transistors connected across the DC power supply, and a series circuit of the first and second transistors connected across the DC power supply so that the polarity is opposite to that of the first and second transistors. a series circuit of first and second diodes, first and second capacitors connected across the DC power supply, and a connection point between the first and II2 diodes and the first and third capacitors. A series circuit of a discharge lamp and a current limiting element connected to a connection point of νden f, an impedance element for forming a preheating circuit connected between both filaments of the energized lamp, and the @1 and second transistors. a transformer having its own primary winding connected between the connection point of the diodes and the connection point of the first and second diodes; A discharge lamp lighting device equipped with a control circuit that turns on alternately.