JPS63160198A - Discharge lamp lighter - 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 (Technical Field) The present invention relates to a discharge lamp lighting device that lights a plurality of discharge lamps in parallel at high frequency.

(Background technology) FIG. 8 shows a circuit diagram of a conventional discharge lamp lighting device.

The voltage of the alternating current power supply AC is charged to the capacitor CI through the diode D in the positive half cycle, and is charged to the capacitor C2 through the diode D2 in the negative half cycle.
is charged to. A DC voltage obtained by voltage-doubling rectification of the AC power supply AC is generated across the series circuit of the capacitor C1 and the capacitor C2. This DC voltage is applied to transistors Tr, , T
It is applied to the series circuit of r2. Each transistor Tr
, , between the collector and emitter of Tr2 are diodes D, respectively.

D, are connected in antiparallel. discharge lamp DL+,
D L2 are connected in parallel via a balancer transformer T, and this parallel connection circuit is connected between the collector and emitter of the transistor TrI via a capacitor C3 and an inductance L. Discharge lamp DL,,DL
, 2 are connected in parallel with capacitors C4 and Cs for supplying preheating current, respectively. Each transistor Tr1. The Tr2 is turned on alternately by the output of the control circuit 2, and high frequency power is supplied to the discharge lamps D L l and D L2. The balancer transformer T is used to stably light two discharge lamps, and when one lamp lights up, the balancer transformer T's winding "I +
When the current flowing through the discharge lamp 12 becomes unbalanced, a high voltage is induced, which also lights up the other discharge lamp.

In this discharge lamp lighting device, even if one of the discharge lamps does not light up for some reason, resulting in a so-called one-lamp lighting state, the other discharge lamp will light up. Therefore, even if one of the discharge lamps reaches the end of its life and is turned off, the other discharge lamp remains lit, which is very convenient if the person using it changes.

However, in this conventional example, even if the circuit constants are set so that each discharge lamp has its own rated lamp current when two lamps are lit, the lamp current increases significantly when one lamp is lit. This could increase emitter evaporation in the filament and impair lamp life.

(Object of the invention) The present invention has been made in view of the above points, and
The purpose of this is to reduce the lamp life of other discharge lamps when at least one of the discharge lamps is turned off in a lighting device that lights multiple discharge lamps in parallel at high frequency. To provide a discharge lamp lighting device capable of stably lighting the lamp without damage.

(Disclosure of invention) FIG. 1 is a diagram for explaining the basic configuration of the present invention.

In the figure, reference numeral 1 denotes a high frequency conversion circuit consisting of a separately excited inverter circuit, which converts the output of a DC power source E into a high frequency signal. The discharge lamps D L l and D L 2 are connected in parallel via a balancer transformer T1, and each discharge lamp D
On the non-power side of L, DL2, there is a capacitor C< , Cs
are connected in parallel. The parallel circuit of the discharge lamps DLI and DL2 is connected to the output of the separately excited inverter circuit 1 via a current limiting element such as an inductance L1.

The number-of-lights detection circuit 3 detects the number of discharge lamps that are normally lit, and in accordance with the detected number of lights, instructs the control circuit 2 of the separately excited inverter circuit 1 to control conditions for each discharge lamp. Make sure that approximately the rated current flows through the lamp.

Here, the reason why when one of the plurality of discharge lamps is turned off, unless the control conditions of the high frequency conversion circuit are changed, the lamp life of the other discharge lamps is impaired will be explained. For example, in the circuit shown in Figure 8, when one lamp is on and when two lamps are on, the degree of imbalance in the current flowing through the windings nl+n2 of balancer transformer T1 is greater when one lamp is on, so two lamps are on. When one lamp is lit, the inductance of the balancer transformer T1 becomes larger than when one lamp is lit.

As a result, the resonance frequency of the load, which is determined by the capacitors C3 to C9, the current limiting inductance I, the inductance of the balancer transformer T1, etc., is different from when one lamp is lit and when two lamps are lit.
There is a big difference when the lights are on. Therefore, even if the circuit constants are set so that when two lamps are lit, each discharge lamp will have its own rated lamp current, when one lamp is lit, the lamp current will increase significantly, which will cause evaporation of the emitter in the filament. This can lead to increased lamp life.

Therefore, in the present invention, when the number of lamps changes and the resonance system of the load changes, the high frequency conversion circuit is operated in accordance with the changed resonance system, so that excessive lamp current is prevented from flowing into each discharge lamp. It is designed to prevent electricity from being energized.

Examples of the present invention will be described below. In the description of the embodiment, parts having the same functions as those of the conventional circuit are denoted by the same reference numerals, and redundant description will be omitted.

Figure 2 is a circuit diagram of an embodiment of the present invention. In this embodiment, a two-stone transistor T made of MOSFET is used.
r1. A separately excited half-bridge inverter circuit in which Tr2 is alternately turned on and off is used to light two discharge lamps DL, DL2 with different lamp ratings at high frequency. Current transformers CT, CT2 are connected to the ends of each discharge lamp DL, DL2. The output of each current transformer CT, CT2 is connected to a diode Ds
, Da, the capacitors Cs and Cs are charged. Capacitor C8゜C9 has resistors Ra and R
s are connected in parallel.

The terminal voltage of capacitor C8 is connected to one input of AND gate G3 and exclusive OR gate G5.

The terminal voltage of capacitor C9 is connected to one input of AND gate G, and is also connected to the other input of exclusive OR gate G5. The output of exclusive OR gate G5 is output from AND gate G3. Connected to the other input of G<. And Gate G 3. The outputs of G < are each connected to a resistor R7°.

It is connected to the base of the transistor Tr<, Trs via RI. When transistors Tr, Tr5 are turned on, resistors R+4, . R,5 is connected in parallel with resistor R13. Resistor R62 and resistor R13
A power supply voltage Vcc is applied to the series circuit with.

The voltage at the connection point between the resistor R32 and the resistor R13 is applied to the non-inverting input of the operational amplifier IC.

The inverting input of operational amplifier IC3 is connected to the output,
This operational amplifier IC acts as an impedance converter.

The output of operational amplifier IC3 is general-purpose timer IC"555
’” is an astable multivibrator IC.

It is connected to the 5th terminal of the As is well known, this general-purpose timer IC has a trigger terminal (terminal 2) of 1/3 V.
When it becomes less than cc, it is triggered and the output terminal (terminal 3) becomes 'l (high') level, and the discharge terminal (terminal 7) becomes high impedance. Also, the threshold terminal (terminal 6) becomes 2/ When the voltage reaches 3 V cc, the output terminal (terminal No. 3) becomes the 11 LOIL+ level, and the discharge terminal (terminal No. 7) also becomes the "LOIL+" level.

Terminal 1 is an earth terminal connected to the ground level. Terminal 8 is a power supply terminal connected to power supply voltage Vcc.

The No. 4 terminal is a reset terminal and is connected to the power supply voltage Vcc.

A power supply voltage Vcc is applied to a series circuit of resistors R, , R5 and capacitor C6, which constitute a time constant circuit of the astable multivibrator IC. The connection point between resistor R1 and resistor R5 is connected to the discharge terminal (terminal 7), and the connection point between resistor R3 and capacitor C6 is connected to the threshold terminal (terminal 6) and the trigger terminal (terminal 2). )It is connected to the. Astable multi-by-break IC,
The operating frequency is determined by the resistors R, , R5, the capacitor C6, and the voltage at the 5th terminal, and as the 5th terminal voltage increases, the operating frequency decreases.

IC2 is a D flip-flop, and here it works as a T flip-flop by shorting the output and the D input. That is, it operates as a so-called 1/2 frequency divider circuit whose output is inverted by the rising edge of the clock input (C input). The output and output of the D flip-flop C2 are connected to one input of the AND gate G+, G2. anime) G +
, G2 is connected to the output of an astable multivibrator IC. The output of the AND gate G is connected to the gate of a transistor Tr2 made up of a MOS FET via a resistor R5. The output of the AND gate G2 is connected to the base of the transistor Trs via a resistor R6. A power supply voltage Vcc is applied to the series circuit of the transistor Tr3 and the primary winding of the transformer T2. A resistor R is connected to the primary winding of the transformer T2.
A series circuit of capacitor C7 and capacitor C7 is connected. A resistor R2 is connected to the secondary winding of the transformer T2,
The voltage generated across resistor R2 is applied to the MOSFE via resistor R3.
A transistor Tr made of T.

is applied to the gate of Therefore, and gate Gl
When the output of the transistor T is 'High1+' level, the transistor T
rz turns on, and the output of AND gate G2 goes high.
h” level, the transistor Tr= is turned on,
Transistor Tr+ is turned on via transformer T2. Thereafter, by repeating this operation, the transistors Tr, Tr2 are alternately turned on and off. The above operation is shown in FIG.

Generally, in the case of a half-bridge inverter circuit, a damper diode is connected in parallel with the transistors T rl and T r2 (see Fig. 1), but in the case of a MOSFET
In the case of ET, this damper diode is built-in, so anti-parallel diodes are not required.

The operation of the discharge lamps DL + and DL 2 in each lighting state will be described below.

First, a case where both the discharge lamps D Ll and p L2 are lit will be described. Current transformer CT +
, CT2 represents each discharge lamp DL + , DL x
detects the lamp current of the diode D s ,
The current flowing through D6 causes the capacitor Cs,
A charging voltage is generated at Cs. Therefore, both the inputs of the exclusive OR gate G5 are at the 'High' level, and the outputs thereof are at the 'Loud' level, so the outputs of the AND gate G3 and G5 are both at the 'Lou' level, and the transistor T r41 T r s are both turned off. Therefore, the non-inverting input terminal voltage of the operational amplifier ICs is determined by the resistors R1□ and R■, and its value is R+ 3・Vcc/(RI2+ Rl :l), which is the voltage at the 5th terminal of the astable multivibrator IC. Therefore, the astable multivibrator IC3 operates in oscillation at an operating frequency corresponding to this value.

Next, when only the discharge lamp DL+ is lit, a charging voltage is generated in the capacitor C8, but a charging voltage is not generated in the capacitor C9. Therefore, the two-man power of exclusive OR gate G5 is Hig11” level and 'LO
L11" level and the output becomes 'Higb' level. Therefore, the output of AND gate G3 is 'HiFi
h" level, the output of the AND gate G becomes the "Loud" level, the transistor Tr4 is turned on, and the transistor T
r is turned off. At this time, the non-inverting input terminal voltage of the operational amplifier IC3 is RI3・R+<・Vcc/(
R+2 ・RI3+ R13・R+4 + RI4 ・
R+2>, and the astable multi-vibration break I Cl oscillates at an operating frequency corresponding to this value.

Conversely, when only the discharge lamp DL is lit, the output of AND gate G3 is 'Low' level, and the AND gate G
The output of 4 becomes 'High' level, and the transistor T
Since r4 is off and transistor Tre is on,
The non-inverting input terminal voltage of operational amplifier IC3 is R, +3
・R+s・Vcc/(R+2-Rl3+R+3'R+s
+R+s·R12), and the astable multivibrator xc, h< oscillates at an operating frequency corresponding to this value.

Here, obviously R+3・R14/(RI2・R+s
+ Rl 3・Rl 4 + R+ 4・R+□) is
R+ , / smaller than (Rl 2 + R13),
R11・R15/(R12・R+3+R1,・R+ s
+ R+ s・R32) is R1/(R+2+R+2
), the operating frequency is higher when the mini lamp is lit than when two lamps are lit. Also, the resistance R,,,
Unless the value of R is R,,=R,, the discharge lamp D L
The operating frequency is not the same when only the discharge lamp DL 2 is lit and when only the discharge lamp DL 2 is lit.

Therefore, the operating frequency differs depending on whether the discharge lamps DL, D, and L2 are all lit, when only the discharge lamp bLl is lit, or when only the discharge lamp DL2 is lit. In addition, when one lamp is lit, the operating frequency of the inverter is higher than when two lamps are lit, thereby reducing the lamp current.

Therefore, the resistor Rl 21 Rl 3 is connected to the discharge lamp D Ll,
The resistor R1 is set so that the rated lighting occurs when both D and R2 are lit.
, so that the rated lighting occurs when only the discharge lamp DL+ is lit, and the resistor R15 is set so that the rated lighting occurs when only the discharge lamp DL2 is lit. Regardless of the lighting state, the discharge lamp can always be lit at its rated value, and it is possible to prevent the lamp life from deteriorating due to an increase in lamp current when one lamp is lit as described in the conventional example. The above operation is repeated in the fourth step.
As shown in the figure.

In addition, in this embodiment, it has been explained that the operating frequency of the inverter is controlled so that each discharge lamp can be lit at its rated value in the lighting state of each discharge lamp, but it is also possible to prevent deterioration of lamp life when one lamp is lit. From this point of view, it is not necessarily necessary to turn on the rated lamp when one lamp is lit, but the operating frequency may be set so that the lamp current is set to such an extent that the lamp life will not deteriorate when one lamp is lit.

In addition, in discharge lamps whose lamp current can be controlled by on-duty control of transistors, on-duty control is possible.
The lamp current may be set in the lighting state of each discharge lamp by controlling the duty.

1 shaku salmon λ FIG. 5 is a circuit diagram of another embodiment of the present invention.

In this embodiment, one transistor Tr+ delays on/off to turn on the discharge lamp at a high frequency, while a separately excited inverter circuit is used. The voltage of the alternating current power supply AC is full-wave rectified by the diode bridge DB and charged to the capacitor C1. A series circuit of the primary winding of the oscillation transformer ○T and the transistor T r + is connected to both ends of the capacitor C1. A diode D is connected between the collector and emitter of the transistor Tr+.

are connected in antiparallel, and a capacitor C6 is connected in parallel.

The balancer transformer T+ is provided with a detection winding n3. The output of this detection winding n3 is charged to a capacitor C5° via a diode D7.

A resistor R2° is connected in parallel to the capacitor CtO. The terminal voltage of capacitor C0o is determined by comparator IC4.
and is applied to the non-inverting input terminal of C5. A voltage obtained by dividing the power supply voltage Vcc by a resistor R+6 and a resistor R17 is applied to the inverting input terminal of the comparator IC. In addition, the inverting input terminal of the comparator ICs is
A voltage obtained by dividing the power supply voltage Vcc by a resistor R18 and a resistor R5 is applied. The output of the comparator IC is
Connected to one input of Antogame I to G3,
It is inverted by an inverter G6 and connected to one input of an AND gate G. The output of the comparator IC5 is the AND gate G3. Connected to the other input of G<. And Gate G 3. G output is 'H'
By reaching the "high" level, the transistors Tr, respectively.

T r 5 is turned on, resistors R14 and R15 are connected in parallel to resistor R53, and resistor RH
The oscillation frequency of the astable multivibrator ICI changes when the terminal voltage of the astable multivibrator ICI changes when the terminal voltage of the astable multivibrator ICI is inputted to the fifth terminal of the astable multivibrator C1 via the operational amplifier I C3. .

The output terminal (terminal 3) of the astable multivibrator IC+ is connected to the trigger terminal (terminal 2) of a monostable multivibrator IC6 made of a general-purpose timer IC "'555". Monostable multivibrator IC6
Resistor R21 and capacitor CI+ constitute the time constant circuit of
A power supply voltage Vcc is applied to the series circuit. A discharge terminal (terminal No. 7) and a threshold terminal (terminal No. 6) are connected to the connection point between the resistor R2 and the capacitor CI+. Output of monostable multivibrator IC6 (
Terminal 3) is inverted by inverter G7 and connected to resistor R2.
The transistor TrI is connected to the base of the transistor TrI via a speed-up circuit formed by connecting a capacitor C12 and a capacitor C12 in parallel.

The monostable multivibrator IC6 has the second terminal voltage (
1/3) Vcc or lower, a trigger is activated and the output (terminal 3) voltage remains at the "High" level for a certain period of time. The period is determined by the time constants of resistor R2 and capacitor C1. Therefore, when the 5th terminal voltage of the astable multivibrator E C1 changes, the operating frequency of the astable multivibrator IC changes (as the 5th terminal voltage increases, the operating frequency decreases), and the operating frequency of the astable multivibrator IC 6 changes. Although the trigger period changes, the high level period of the output (terminal 3) voltage of the monostable multi-bibreak IC6 is constant, so the LOII
The I-level period changes. Monostable multivibrake■
Since the output of C6 is inverted by inverter G7, the on-period of transistor Trl changes. The above operation is shown in FIG.

Therefore, in this embodiment, the balancer transformer T,
The lighting state is determined based on the induced voltage of the balancer 1 to the lance T, and when one lamp is lit, it is determined which of the discharge lamps DL, DL2 is lit based on the difference in the induced voltage of the balancer 1 to the lance T. When lighting discharge lamps with different lamp ratings according to their respective rated currents, stable lighting can be achieved by appropriately adjusting the ratio of windings +11+I+2 of the balancer transformer T, for example. Therefore, there are differences in the current flowing through the balancer transformer T and the detection winding n when only the discharge lamp DL is lit and when only the discharge lamp DL2 is lit.
3 (difference between n3/nl and n3/n2), the voltage generated in the detection winding n3 differs, so it is possible to detect which discharge lamp is lit. becomes possible.

First, when the discharge lamps DL, DL2 are both lit, the voltage generated in the balancer transformer T1 is very small, so the reference voltage (inverting input terminal voltage) of the comparators IC, IC9 is applied to the resistors R16 to R7. If a suitable selection is made based on , then the comparator IC, .

Both output voltages of IC5 become "'Low" level. On the other hand, when one lamp is lit, assuming that the voltage generated in the balancer transformer T is higher when the discharge lamp DL is lit than when the discharge lamp DL2 is lit, for example, the comparator IC1 The reference voltage of discharge lamp D
By setting the voltage to be lower than the non-inverting input terminal voltage when only discharge lamp DL is lit and higher than the non-inverting input terminal voltage when only discharge lamp DL is lit, only discharge lamp DL is lit. When it is lit, the output of the comparator IC is Hi.
On the other hand, if the reference voltage of comparator IC6 is set lower than the non-inverting input voltage when only discharge lamp DL2 is lit, comparator ■C5
When one lamp is lit, the output of discharge lamps DL, DL2
Always “HigI+” regardless of which one is lit.
“It becomes a level.

Therefore, when two lamps are lit, the comparators ■C, ,I
The outputs of both Cs are 'Low' level, and the output of AND gate Q3.Q is 'Lou+' level, therefore,
Both transistors T r 4 and T r s are turned off.

In addition, when only the discharge lamp DL is lit, both the outputs of the comparators ICI and IC5 are "'High"".
level, the output of AND gate G3 is Highb.
The output of the AND gate G4 becomes 'Loud' level, the transistor Tr is turned on, and the transistor Tr5 is turned off.

Furthermore, when only the discharge lamp DL2 is lit, the output of the comparator IC is at the 'Lou+' level, and since the output of the comparator IC is at the 'High' level, the output of the AND gate G3 is at the 'LOLI+' level. , the output of AND gate G4 becomes 'High' level, transistor Tr is turned off, and transistor Tr5 is turned on.

Therefore, the non-inverting input terminal voltage of the operational amplifier IC differs depending on when two lamps are lit, when only the discharge lamp DL is lit, and when only the discharge lamp DL2 is lit, and accordingly, The operating frequency of inverter 1 is controlled.

This is almost the same as described in the first embodiment, and therefore, the same effects as in the first embodiment can be expected in this embodiment as well.

Figure 7 is a circuit diagram of still another embodiment of the present invention. In this embodiment, three discharge lamps DL, DL2°DL3 are
They are connected in parallel via balancer transformers T + and T 2 and lit in parallel at high frequency. Each discharge lamp DL
,,D L2. Current transformers CT + , CT 2 and CT 3 are connected to the ends of D L3, and their outputs are connected to diodes D s and D, respectively.
6, D a through capacitor C'e, C9
, CI: charged to l. Each capacitor Ca, C
s, CI 3 has a resistor Ra, R91R, 23
are connected in parallel.

The terminal voltages of each capacitor Cs, Cs, CI:l are input to logic gates G8 to GIn, respectively. When the outputs of the logic gates G8 to G13 become 'High' level, the transistors Tr8 to Tr8 to
T r, .

is turned on, and a predetermined resistor is connected in parallel to resistor R13.

First, when all the discharge lamps are lit, all transistors Tr6 to Tr13 are off, and when two lamps are lit, depending on the combination of lit discharge lamps, which one of the transistors TrlI to TrH3 is turned off. is on, and when one lamp is lit, the transistor T
One of ra to Trlo is turned on,
This makes it possible to control each discharge lamp according to its lighting state, and to control the lamp current so that it does not increase to the extent that the lamp life is impaired, regardless of the lighting state. It becomes possible.

In each of the above embodiments, it has been explained that when discharge lamps with different lamp ratings are lit in parallel, deterioration of lamp life is prevented by changing the control conditions of the inverter depending on the lighting state of the discharge lamps. However, regarding these discharge lamps, even if the lamp ratings are not different or have the same rating, the present invention can be achieved if the lamp current when one lamp is lit is similarly controlled to an extent that does not impair the lamp life. The effect can be expected, and in this case, for example, the second
In the embodiment shown in the figure, the resistors R+4, 'RI
The value of 5 may be set to R14=RI5.

(Effects of the Invention) As described above, the present invention provides that among a plurality of discharge lamps that are lit in parallel via a current limiting element by the output of a high frequency conversion circuit,
In a discharge lamp lighting device in which the resonant frequency of the load changes when at least one lamp goes out, a detection means for detecting a decrease in the number of discharge lamps is provided, and the Because we have provided a means to control the high frequency conversion circuit so that approximately the rated current flows through each discharge lamp,
Even if the resonant frequency of the load changes due to a decrease in the number of lamps, an excessive current will not flow through the discharge lamp, which has the effect of preventing the life of the discharge lamp from being impaired.

[Brief explanation of the drawing]

Figure 1 is a block circuit diagram showing the basic configuration of the present invention, Figure 2 is a block circuit diagram showing the basic configuration of the present invention.
The figure is a circuit diagram of one embodiment of the present invention, Figures 3 and 4 are diagrams explaining the operation of the same as above, Figure 5 is a circuit diagram of another embodiment of the present invention, and Figure 6 is a diagram explaining the operation of the same as above. , FIG. 7 is a circuit diagram of still another embodiment of the present invention, and FIG. 8 is a circuit diagram of a conventional example. 1 is a separately excited inverter circuit, 2 is a control circuit, 3 is a lamp number detection circuit, D L I and D L 2 are discharge lamps, E is a DC power supply, and L is an inductance.

Claims (2)

[Claims] (1) Consisting of a DC power source, a high frequency conversion circuit that converts the output of the DC power source into a high frequency, and a plurality of discharge lamps that are lit at high frequency in parallel by the output of the high frequency conversion circuit via a current limiting element, A discharge lamp lighting device in which a resonance frequency determined by a high frequency conversion circuit, a current limiting element, and a lit discharge lamp changes when at least one of the plurality of discharge lamps goes out, A detection means for detecting a decrease in the number of electric lamps is provided, and a means for controlling a high frequency conversion circuit so that approximately the rated current flows through each discharge lamp in accordance with the detection output of the detection means. Characteristic discharge lamp lighting device. (2) The discharge lamp lighting device according to claim 1, wherein the high frequency conversion circuit is a separately excited inverter circuit.