JPH01246793A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To prevent wasteful consumption of power and suppress generation of excessive voltage by furnishing a control circuit to restrict oscillation output from an inverter circuit when the total filemants of discharge lamps in series connection are not fitted perfectly. CONSTITUTION:When a filament f2 or f3 commonly connected with discharge lamps l1, l2 in series connection is out of connection, the sensing power of a filament sensing circuit 3 goes out, and when a filament f1 or f4 is out of connection, the sensing output of a voltage sensing circuit 2 connected between the other end of a capacitor C1 and the other end of a DC power supply E will go out. An output control circuit 4 restricts the oscillation output of an inverter circuit 1 when either of the sensing outputs of the mentioned circuits 2, 3 has gone out, and thereby wasteful consumption of the electric power and generation of excessive voltage are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device that lights a discharge lamp using an inverter circuit.

[Prior Art] FIG. 9 is a circuit diagram showing a conventional inverter circuit used in a discharge lamp lighting device. In FIG. 9, a DC power source E is constituted by a constant voltage power source obtained by rectifying a commercial AC power source. A switching element Q is connected to the DC power supply E via a power switch SW.
, , Q2 are connected in series. The switching elements Q, Q2 are composed of transistors and the like, and are driven to be turned on and off alternately. A series circuit of a coupling capacitor C3, a load R, an inductance element, and a primary winding n1 of a current feedback transformer T1 is connected in parallel with at least one switching element Q among these switching elements Q, Q2. is connected. A resonance capacitor C2 is connected to the load R in parallel. A voltage detection circuit 2 is connected between the non-power supply side terminal of the capacitor C1 and the negative terminal of the DC power supply E. This voltage detection circuit 2 is configured by a voltage dividing circuit using a resistor element having an impedance higher than that of the load R, and detects the presence or absence of the load R. When the load R is not connected, the capacitor C1 is charged to the same voltage level as the DC power supply E, and the input voltage of the voltage detection circuit 2 becomes a low level. Also, when load R is connected,
Capacitor C1 is charged to about half the voltage level of DC power supply E, and the input voltage of voltage detection circuit 2 becomes high level.

In the inverter stop circuit 4, when the detection output from the voltage detection circuit 2 disappears, the transistor Q is turned off and the transistor Q is turned on, and the switching element Q2 is forcibly turned off.

This is to stop the switching operation of Q2.

The operation of this circuit will be explained below. When the power switch SW is turned on and the DC power source E is applied, the switching element Q2 is turned on by the starting circuit 6, and thereafter,
The switching elements Q, Q2 are alternately turned on and off by a drive circuit 5 comprising a current feedback transformer T1. A high voltage with a high frequency is applied to both ends of the load R by an LC series resonant circuit 8 made up of an inductance element L1 and a capacitor C2, and the load R operates.

Here, when the load R is removed and there is no load, the capacitor C1 is charged only in one direction via the resistors R4 and Rs, and is charged to the same voltage as the DC power supply E, so the detection output of the voltage detection circuit 2 is Becomes a low level. At this time, the oscillation of the inverter circuit 1 is stopped under the control of the inverter stop circuit 4.

After that, when the load R is connected again, the resistor R11, the diode, and the gate D1 connected in parallel with the switching element Q1,
The charge of the capacitor CI is discharged through the primary winding nl of the current feedback circuit T, the inductance element L1, and the load R, and the charging voltage of the capacitor C2 decreases. As a result, the input voltage of the voltage detection circuit 2 becomes high level. When the input voltage of the voltage detection circuit 2 reaches a high level, a voltage detection output is generated, so the operation of the inverter stop circuit 4 is canceled, the inverter circuit 1 performs normal operation, and a high voltage is applied to the load R. and the load R operates normally.

[Problem to be Solved by the Invention 1] In the above-mentioned conventional example, the load R is a discharge lamp 17. ．． A circuit diagram including 12 series circuits is shown in FIG.

In this circuit, the non-power supply side terminal of the filament f of the discharge lamp 12 is connected to the discharge lamp 11 through a parallel circuit of a capacitor C4 and a resistor R1, and a primary winding N1 of a preheating transformer T2.
is connected to the non-power supply side terminal of the filament f1.

Also, both electric lights 1. ．． 12 other filamen +-r2
．． r, are connected in series to the secondary winding ti N 2 of the preheating transformer T2. These resistors R, capacitor C1, and preheating transformer T2 constitute a preheating circuit 7 for filaments r, , f, , fs, and f.

Here, discharge lamp 1. , It2 is a round tube type, the sockets for the pair of filaments are integrated, so both filaments are connected almost simultaneously, but if the discharge lamp is a straight tube type, each filament sockets are independent. Therefore, as shown in FIG. 10, when discharge lamps (1, 12) are connected in series, each filament r, , r2, rz.

The sockets I and R are independent. For this reason, for example, connect the discharge lamp 12 in advance, and then connect the discharge lamp! , there is no problem if you connect filament f2 first, but if you connect filament f first, filament r
, , Since the charge in the capacitor C1 is discharged via r4 and the preheating circuit 7, the inverter circuit 1 starts oscillating while the load is still in the abnormal state until the filament f2 is connected. Switching element Q 1.
Since a large resonant current flows through Q2, there is a problem in that the switching loss of the switching elements Ql and Q2 increases. Furthermore, when the resonant current increases, the voltage across capacitor C2 also increases, and the output voltage becomes 30% in effective value.
There is a possibility that it will exceed 0 ■. When used as a lighting fixture, a discharge lamp! , 12 and the power supply are not insulated,
If the output voltage exceeds 300 V in effective value, it will not comply with the Electrical Appliance and Material Control Act and JIS standards, so it is necessary to prevent the generation of such excessive voltage.

Further, a similar problem occurs when the filament is disconnected. Discharge lamp 1. ．． When filament lf or r among the 12 non-common side filaments is disconnected, a complete no-load state occurs, so voltage detection circuit 2 operates normally and oscillation of inverter circuit 1 stops. Tokoroka (
, when the filament t-r2 or r is disconnected, the voltage detection circuit 2 does not operate normally for the same reason as above,
Oscillation of inverter circuit 1 does not stop. The latter problem occurs not only when a straight tube discharge lamp is used, but also when a round tube discharge lamp is used.

The present invention has been made in view of these points, and its purpose is to increase the oscillation output of the inverter circuit only when all the filaments of the discharge lamps connected in series are completely installed. An object of the present invention is to provide a discharge lamp lighting device.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, first and second switching elements Q, Q2 connected in series are connected to a DC power supply E, one end of a capacitor C2 is connected to one end of the DC power supply E, and one end of the capacitor C1 is connected to one end of the DC power supply E. A discharge lamp 1 connected in series between the other end and the connection point of the first and second switching elements Q, Q2.
．． ．． 12 is connected via an inductance element, and the first and second switching elements Q, , Q
Turn on and off the discharge lamps 1 and 2 alternately. ．． In the discharge lamp lighting device, the discharge lamp lighting device includes an inverter circuit 1 that supplies alternating current power to the capacitor C1, and a voltage detection circuit 2 connected between the other end of the capacitor C1 and the other end of the DC power source E, the discharge lamps are connected in series. 1. ．． 12 commonly connected filaments r2
．． A filament detection circuit 3 for detecting f3 is provided, and an output control circuit 4 is provided for limiting the oscillation output of the inverter circuit 1 when at least one of the detection outputs of the filament detection circuit 3 and the voltage detection circuit 2 disappears. This is a characteristic feature.

[Function] In the present invention, as described above, the discharge lamps 1. ．． 12 commonly connected filament l□ f2゜r
Since the filament detection circuit 3 is provided to detect , when filament f2 or f is not connected,
The detection output of the filament detection circuit 3 disappears. Also,
A voltage detection circuit 2 connected between the other end of the capacitor C1 and the other end of the DC power supply E detects the filaments f, , f4, and when the filament r1 or f4 is not connected, the voltage detection circuit 2 2 detection output disappears. In the present invention, when at least one of the detection outputs of the voltage detection circuit 2 and the filament detection circuit 3 disappears, the output control circuit 4 limits the oscillation output of the inverter circuit 1. When the filament is not connected, the oscillation output of the inverter circuit 1 can be restricted to prevent wasteful power consumption and also to prevent the generation of excessive voltage.

[Example 1] FIG. 2 is a circuit diagram of a first embodiment of the present invention.

The circuit configuration will be explained below. An inverter circuit 1 is connected to the DC power source E via a power switch SW. The inverter circuit 1 includes switching elements Q, Q2 made of transistors, and an input DC voltage is applied to a series circuit of the switching elements Q, Q2. In parallel with one switching element Q1, a coupling capacitor C3, discharge lamps 11 and 12, an inductance element L1, a primary winding n of a current feedback transformer T1,
series circuit is connected. The filament rl of the first discharge lamp 11 and the filament 1 of the second discharge lamp 12. A resonance capacitor C2 is connected in parallel between the respective power supply side terminals. This capacitor C2 may be a stray capacitance. The non-power supply side terminal of the filament rl of the discharge lamp 11 is connected to the filament tr of the discharge lamp 12 via a parallel circuit of a capacitor C1 and a resistor R8, and the primary windings of a preheating transformer T2 and a detection transformer T4.

connected to the non-power side terminal of the Also, both electric lights 1.
．． 12 other filaments f2. f, are connected in parallel via the primary winding n4+ns of the filament detection transformer T, and the secondary winding of the preheating transformer T2 is connected to this parallel circuit. With this preheating transformer T2, resistor R8 and capacitor C1, filament 1-r,
, r2. A preheating circuit 7 of r, , r, is configured.

Next, the configuration of the voltage detection circuit 2 will be explained.

One end of the coupling capacitor C1 is connected to the positive input terminal of the inverter circuit 1, and the discharge lamp 1. ．． A series circuit of resistors R, , R2 having a higher impedance than 12 is connected. The voltage obtained at the connection point (point a) of these resistors R4 and Rs is
This is the detection output of the voltage detection circuit 2.

Next, in this embodiment, the configuration of the filament detection circuit 3 will be described.As described above, the discharge lamp 1. ．． 1
2 filament f2. f is connected to the secondary winding of the preheating lance T2 via the primary winding n 4 + n of the filament detection transformer T, , respectively. Secondary winding n of transformer T3 for filament detection
6 is connected to a capacitor C5 via a diode D4. A resistor R1 is connected in parallel to both ends of the capacitor C5. The negative terminal of capacitor C5 is grounded,
The positive terminal is used as an input to NOT circuit G1. The output of the NOT circuit G is the detection output of the filament detection circuit 3.

Next, the configuration of the output control circuit 4 will be explained.

The output of filament detection circuit 3 is connected to the base of transistor Q6 via resistor R3.

The collector of transistor Q6 is connected to the connection point between the anode of diode D5 and resistor R6.

The emitter of transistor Q6 is grounded.

One end of the secondary winding of the detection transformer T4 for preheating current detection is grounded, and the other end is connected to the base of the transistor Q via a diode D, a resistor R5, and a diode D5. The collector of transistor Q is connected to the connection point between resistors R2 and R1□, and the emitter of transistor Q is grounded. The output of the voltage detection circuit 2 is input to the NOT circuit G2. The output of the NOT circuit G2 is connected to the base of the transistor Q via a resistor R1 and a diode D.

The current feedback transformer T has two secondary windings n2, n, one secondary winding +12 is connected between the base and emitter of the switching element Q through a bias resistor R2, and the other The secondary winding n, is bias resistor R2, R
12 between the base and emitter of the switching element Q2. This constitutes the drive circuit 5.

Furthermore, a resistor R3 is connected between the input terminals of the inverter circuit 1.
A series circuit of R1 and capacitor C1 is connected, and the connection point of resistor R1 and capacitor C3 is diac Q.

It is connected to the base of the switching element Q2 via the diode D, and is connected to the collector of the switching element Q2 via the anode and cathode of the diode D. These resistor R3, capacitor C3, diac Q3
and diode D, are the starting circuit 6 of the inverter circuit 1.
It consists of

Note that the switching elements Q, Q2 include diodes D.
, , D2 are connected in antiparallel, but these diodes D + , D 2 are not necessarily required.

The operation of this embodiment will be explained below. When the power switch SW is turned on, the DC power source E is connected to the inverter circuit 1, and the capacitor C1 is charged via the resistor R3. When the voltage of the capacitor C1 reaches the breakover voltage of the diac Q, the charge in the capacitor C3 is discharged through the base-emitter of the switching element Q2. This turns on switching element Q2. After that, the secondary winding +1□, 11 of the current feedback transformer T1
．． The feedback current obtained from the switching element Q, ,
Q2 is turned on and off alternately. At this time, the coupling capacitor C3 is charged with voltage E/2, which is about half of the DC power supply E. Therefore, the voltage divided by the resistors R1 and R5 becomes a "High" level, and the detection output of the voltage detection circuit 2 becomes a "'High" level.

As a result, the output of NOT circuit G2 becomes ゛Lou+″°
level, bias resistor R1o and diode D7
f! :The base current to the transistor Q4 is cut off.

Here, the discharge lamp e, , 12 filaments +-r, , r
, if at least one of them is removed to create an unloaded state,
Since the coupling capacitor C8 is charged only in one direction via the resistors R,,r(,) to the same voltage level as the DC power supply E, the input voltage to the voltage detection circuit 2 becomes low. The detection output of voltage detection circuit 2 is “Low”
level. Therefore, the output of NOT circuit G2 becomes Hi.
gl+'' level, the base current flows through the transistor Q through the bias resistor RIG and the diode D7, and the transistor Q4 is turned on. When the transistor Q is turned on, one switching element Q2 is forced to turn off. Therefore, the secondary winding n of the current feedback transformer T,
2. No feedback current can be obtained from ns, and the switching element Q3. Q2 are both turned off. Therefore, the oscillation of the inverter circuit 1 is stopped.

Next, discharge lamp 1. ．． 12 filaments f2. When one of fs is disconnected, the detection output of the filament detection circuit 3 becomes "Low" level. Now, when only the filament r of the discharge lamp 12 comes off, only one primary winding n of the filament detection transformer T is connected, and the secondary winding n6 of the detection l/lance T is connected. A voltage is induced, and the voltage e1 of the capacitor C1 becomes the "HiH1+" level. Therefore, the output of NOT circuit G is “LoII++
The level becomes t, and the transistor Q6 is turned off.

At this time, during the on period of the switching element Q2,
Detection transformer T for preheating current detection.

A base current is supplied to the transistor Q4 through the diode D6, the resistor R6, and the diode D, and the transistor Q4 is turned on. For this reason, the base current of the switching element Q2 that had been flowing until now is cut off, and at the same time, the charge stored in the stray capacitance between the base and emitter of the switching element Q2 flows to the transistor Q4.
Switching element Q2 turns off quickly. therefore,
When the transistor Q1 turns on and off, the on period of the switching element Q2 becomes shorter, and the switching element Q,
, the conduction period of Q2 becomes asymmetric. At this time, the output voltage eO(t) of the inverter circuit 3 becomes an asymmetric voltage between the positive and negative sides, as shown in FIG. Here, the output voltage eo(t
) is actually a positive/negative asymmetric voltage that includes a DC component voltage, but equivalently it is an AC component voltage with hatching and a DC component voltage E without hatching.

It can be thought of as the composite voltage of Here, the DC component voltage is cut by the capacitor C1 and no DC current flows through the load, so that the only voltage applied to the load is the AC component voltage indicated by diagonal lines.

The AC component voltage at this time is smaller than when the transistor Q is not operating, and the output voltage of the inverter circuit 1 can be lowered.

In addition, since the current flowing through the switching elements Q, Q2 can also be reduced.

C2 can also be protected. Discharge lamp! , the same operation occurs when only the filament f2 of , comes off.

On the other hand, discharge lamp 1. ．． 12 filaments r2. r, are connected together, the primary winding n4. of the filament detection transformer T3. ns, the filaments r2. r
Since the preheating current of 3 flows, no voltage is induced in the secondary winding n6, and the voltage e1 of the capacitor C5 becomes zero. At this time, the output of NOT circuit G1 becomes "High" level, transistor Q6 is turned on, and the output power of detection 1 to lance T for preheating current detection is short-circuited by transistor Q6. doesn't work.

Discharge lamp 1. ．． 12 total ficimen I-f+, f2. fi
, L is connected, both the detection output of the voltage detection circuit 2 and the detection output of the filament detection circuit 3 are "'".
The L transistor Q6 is turned on, and the output of the NOT circuit G2 becomes a "Low" level.

Therefore, the base currents to transistors 1 through Q through bias resistors R6, R, . are both cut off, and transistor Q4 is turned off. At this time, the driving current is normally applied to the switching element Q2 from the current feedback transformer T1, so that the inverter circuit 1 normally performs the oscillation operation. In a steady state, a high frequency high voltage is applied to both ends of the discharge lamp 1.12 by an LC resonant circuit composed of an inductance element and capacitors C2 and C4, and the discharge lamps N, , and C2 are lit.

[Example 2] FIG. 6 is a circuit diagram of a second embodiment of the present invention.

In this embodiment, the tertiary winding N of the preheating transformer T2 also serves as a filament detection transformer.

The tertiary winding N of the preheating transformer T2 is connected to the capacitor C1 via a diode D4. Capacitor C
A resistor R++ is connected in parallel to both ends of 7. The negative terminal of capacitor C7 is grounded, and the positive terminal is connected to one input terminal of comparator CP. A reference voltage 8 is applied to the other input terminal of the comparator CP.

The output of this comparator CP serves as the detection output of the filament detection circuit 3. For other configurations,
Since this is the same as in the first embodiment, parts having the same functions are given the same reference numerals and redundant explanations will be omitted.

The operation of this embodiment will be explained below. First, filament f2. When f- are connected together, the load on the preheating transformer T2 is large, so the voltage induced in its tertiary winding aN3 is small. At this time, let the voltage generated across the capacitor C2 be e, and from this voltage e, The reference voltage ■ is also increased so that the reference voltage VR of the comparator CP becomes larger.
Set R.

Comparator CP is a voltage e1 generated across capacitor C5.
is smaller than the reference voltage vR, the output becomes “I(
level. Therefore, the filament +−
r2. When r is connected normally, the output of the filament detection circuit 3 becomes "'High" level.

Next, when one of the filaments l-[2, r, comes off, the filament resistance decreases by one, so the preheating transformer T
The load on the capacitor C6 becomes lighter, the voltage induced in its tertiary winding N3 becomes higher, and the voltage e1 generated in the capacitor C6 increases. The reference voltage V8 is set so that the reference voltage (3) of the comparator CP is lower than the voltage el of the capacitor C5 at this time.

Comparator CP is a voltage e1 generated across capacitor C5.
is larger than the reference voltage VR, the output becomes “Lo
Therefore, when the filament r2 is not connected, the output of the filament detection circuit 3 becomes the "Low" level. Even when the filament r is not connected, the output of the filament detection circuit 3 is at the "Low" level for the same reason as above.

Moreover, filament f2. When both f3 are disconnected, the load on the preheating transformer T2 becomes even lighter, so the voltage e generated across the capacitor C6 becomes even higher.
Therefore, the output of comparator CP is still “Low”.
``level, and the output of filament detection circuit 3 is''
Becomes Low” Rebel.

Other operations are the same as in the first embodiment.

[Example 3] No. 7 (21) is a circuit diagram of a third embodiment of the present invention.

In this embodiment, in Embodiment 1, the NOT circuit G
A timer circuit 9 is inserted between the output of 1 and the bias resistor R3. The output of NOT circuit G1 is °'Lou
d" level, the output of the inverter circuit 1 is controlled by intermittently turning the transistor Q6 on and off using the output of the timer circuit 9 and causing the transistor Q to operate intermittently. The output voltage of the inverter circuit 1 at this time is as shown in FIG. 8(e).

Further, as a method of reducing the output of the inverter circuit 1, a method of changing the oscillation frequency of the inverter circuit 1 may be used.

[Effects of the Invention] As described above, the present invention provides a discharge lamp lighting device including an inverter circuit for lighting discharge lamps in series and a voltage detection circuit for detecting a no-load state of the inverter circuit. an output control circuit that includes a filament detection circuit that detects a commonly connected filament 1- of the discharge lamps, and that limits the output of the inverter circuit when at least one of the detection outputs of the filament detection circuit and the voltage detection circuit disappears. As a result, when the filament on the non-common side of the discharge lamp is not connected, the detection output of the voltage detection circuit for detecting the no-load state of the inverter circuit disappears, thereby limiting the oscillation output of the inverter circuit. Furthermore, when the filament on the common side of the discharge lamp is not connected, the detection output of the filament I/detection circuit disappears, thereby limiting the oscillation output of the inverter circuit.

Therefore, if even one of the filaments of the discharge lamps connected in series becomes disconnected, the oscillation output of the inverter circuit can be limited, reducing wasteful power consumption. This has the effect of preventing excessive voltage generation.

[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 the first embodiment of the present invention, Figures 3 and 4 are main circuit diagrams of the same as the above, Figure 5 is an operation waveform diagram of the same as the above, and Figure 6 is the circuit diagram of the second embodiment of the present invention. The circuit diagram, FIG. 7, is the third embodiment of the present invention.
FIG. 8 is a circuit diagram of the embodiment, FIG. 8 is an operation waveform diagram of the same as above, FIG. 9 is a circuit diagram of a conventional example, and FIG. 10 is a circuit diagram of another conventional example. 1 is an inverter circuit, 2 is a voltage detection circuit, 3 is a filament detection circuit, 4 is an output control circuit, 1. ．． 12 is a discharge lamp, L, r2. rs, L is filament I. Figure 3 Figure 4 C1 Figure 5

Claims (1)

[Claims] (1) Connect the first and second switching elements connected in series to a DC power supply, connect one end of a capacitor to one end of the DC power supply, and connect the other end of the capacitor to the first and second switching elements.
A load circuit including discharge lamps connected in series is connected between the connection points of the switching elements through an inductance element, and the first and second switching elements are alternately turned on.
A discharge lamp lighting device includes an inverter circuit that supplies alternating current power to the discharge lamp when the discharge lamp is turned off, and a voltage detection circuit is connected between the other end of the capacitor and the other end of the DC power supply. A filament detection circuit for detecting commonly connected filaments of electric lights is provided, and an output control circuit is provided for limiting the oscillation output of the inverter circuit when at least one of the detection outputs of the filament detection circuit and the voltage detection circuit disappears. A discharge lamp lighting device characterized by: