JPH02144890A - Discharge lamp lightup device - Google Patents

Abstract

PURPOSE:To prevent wasteful consumption of electric power and eliminate generation of excessive voltage by putting all filaments of serially connected discharge lamps into series connection in terms of DC current, shutting between non power side terminals in terms of DC current, and supplying preheat current to the filaments of the discharge lamps. CONSTITUTION:The present invention includes a filament coupling circuit 3 to put all filaments of discharge lamps l1, l2 in series connection in terms of DC current, so that the sensing output of a voltage sensing circuit 2 is generated only when connection is established in all filaments f1-f4 of the serially connected discharge lamps l1, l2, a preheat circuit 7, which shuts in terms of DC current between non power side terminals of the uncommon connection side filaments f1, f4 of the serially connected discharge lamps l1, l2 and supplies preheat current to the filaments f1-f4 of the discharge lamps l1, l2, and an inverter stop circuit 4 to stop oscillation of an inverter circuit 1 when the sensing output of the voltage sensing circuit 2 has gone out. This prevents wasteful consumption of the power and eliminates generation of excessive voltage.

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] Figure 5 is a circuit diagram showing a conventional inverter circuit used in a discharge lamp lighting device (see Japanese Patent Application No. 1983-73533). In Figure 5, a DC power source E is a rectified commercial AC power source. It consists of a constant voltage power supply, etc. A series circuit of switching elements Q, , Q is connected to the DC power source E via a power switch SW. The switching elements Q, , Q, are composed of transistors and the like, and are driven to be turned on and off alternately. These switching elements Q, , Q2
A series circuit of a coupling capacitor C2, a load R, an inductance element L1, and a primary winding II of the current transformer T1 is connected in parallel with at least one of the switching elements Q. 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 load R is not connected, capacitor CI is charged to the same voltage level as DC power supply E, and the input voltage of voltage detection circuit 2 is at a low level. Also, when the load R is connected, the capacitor C1
is charged to about half the voltage level of the DC power supply E, and the input voltage of the voltage detection circuit 2 becomes a high level. In the inverter stop circuit 4, when the detection output from the voltage detection circuit 2 disappears, the transistor Qs is turned off, the transistor Q is turned on, and the switching element Q2 is forcibly turned off, so that the switching elements Q + , Q 2 This is to stop the switching operation of the

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 transformer T1. A high voltage with a high frequency is applied to both ends of the load R by an LC series resonant circuit including an inductance element 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 n 4 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 at a low level. At this time,
Under the control of the inverter stop circuit 4, the inverter circuit 1
oscillation stops.

After that, when the load R is connected again, the switching element Q is connected in parallel with the resistor R1, the diode D1, the primary winding n of the current transformer T, the inductance element R, and the capacitor through the load R. The charge on C1 is discharged, and the charging voltage of capacitor C1 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. Then, the load R lights up normally.

[Problems to be Solved by the Invention] In the conventional example described above, a circuit diagram in the case where the load R includes a series circuit of discharge lamps 1+ and lx is shown in FIG.

In this circuit, the non-power supply terminal of the filament r4 of the discharge lamp 12 is connected to the non-power supply terminal of the filament f1 of the discharge lamp via a parallel circuit of a capacitor C4 and a resistor R6, and the primary winding N of a current transformer T2 for preheating. connected to the side terminal. Also, both electric lights 11. The other filament f2. f, are connected in series to the secondary winding N2 of the current transformer T2. These resistances R
8, capacitor C1 and current transformer T2,
A preheating circuit 7 for filaments fl+r2+f3+f4 is configured.

Here, the discharge lamp 12. ．． 1. If is a round tube type,
Since the sockets for the pair of filaments are integrated, both filaments are connected almost simultaneously, but if the discharge lamp is a straight tube type, the sockets for each filament are independent. Therefore, as shown in FIG. 6, when the discharge lamps 1xe2 are connected in series, each filament L, r2. The fv and L sockets are independent.

For this reason, for example, turn on the power switch SW and turn on the discharge lamp Q.
, , 12 are turned on, there is no problem if you remove filament ``1'' of discharge lamp e first, but filament f2
If the filament fl is removed first, the inverter circuit 1 will continue to oscillate with the load abnormality R (discharge lamp 11 in no-load state) until the filament fl is removed.
Since a large resonant current flows through the switching elements Q, Q2, there is a problem in that the switching loss of the switching elements Q, Q2 increases. Furthermore, when the resonant current increases, the voltage across the capacitor C2 also increases, and there is a possibility that the output voltage will exceed 300V in effective value. When used as lighting equipment, circuits in which the discharge lamps 11, 12 and the power source are not insulated, and the output voltage exceeds 300V in effective value, do not comply with the Electrical Appliance and Material Control Law and JIS standards, and are not recommended for safety. Therefore, it is necessary to prevent the generation of such excessive voltage.

Similarly, discharge lamp 1. ．． 1. After lighting up normally, discharge lamp 1. ．． 12 is removed to put it in a no-load state, the oscillation operation of the inverter circuit 1 is stopped, and the discharge lamps 1, . 12, for example, connect the discharge lamp 12 first, then the discharge lamp! , there is no problem if the filament f2 is connected first, but if the filament r is connected first, the charge in the capacitor C2 will be discharged via the filaments r, , r and the preheating circuit 7. Therefore, until the filament f is connected, the inverter circuit 1 starts oscillating while the load is still in the abnormal state, and a large resonant current flows through the switching elements Q, Q2.

Further, a similar problem occurs when the filament is disconnected. Discharge lamp 1. ．． When the filament f or f4 among the 12 non-common side filaments is disconnected, a complete no-load state occurs, so the voltage detection circuit 2 operates normally and the oscillation of the inverter circuit 1 stops. However, when the filament f2 or f is disconnected, the voltage detection circuit 2 does not operate normally for the same reason as above, and the oscillation of the inverter circuit 1 does not stop.The latter problem only applies to straight tube discharge lamps. This also occurs when a round tube discharge lamp is used.

The present invention has been made in view of these points, and its purpose is to ensure that normal oscillation of the inverter circuit starts only when all the filaments of the discharge lamps connected in series are completely installed. It is an object of the present invention to provide a discharge lamp lighting device which is configured to have the following characteristics.

[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 source E, one end of a capacitor CI is connected to one end of the DC power source E, and one end of the capacitor C1 is connected to one end of the DC power source E. The other end and the first and second switching elements Q1. Between the connection points of Q2, discharge lamps 1+, j! A load circuit including the discharge lamp 1.
, l, includes an inverter circuit 1 that supplies AC power to
In a discharge lamp lighting device in which a voltage detection circuit 2 is connected between the other end of the capacitor C1 and the other end of the DC power supply E,
Total filament fI of discharge lamps 17 and 12 connected in series
.

r2. A total of 7 discharge lamps (it, 1tcl) are connected in series so that the detection output of the voltage detection circuit 2 is generated only when r, ,r, are connected.
, fz, fiJ4 are connected in series in a direct current manner, and a discharge lamp 11 . The non-power supply side terminals of the non-common connection side filaments f, , f, of the discharge lamps 1+ and 12 are cut off in terms of direct current, and the filaments L, f2, f3, f3, 12 of the discharge lamps 1+, 12 are connected. A preheating circuit 7 that supplies a preheating current to L and an inverter stop circuit 4 that stops oscillation of the inverter circuit 1 when the detection output of the voltage detection circuit 2 disappears.

[Function] In the present invention, as described above, the discharge lamps 1. ．． 12 all filament rl J2. L, f4 f
Discharge lamps 1. ．． Since the filament connection circuit 3 that connects all 12 filaments L+f2+r3+f4 in series in a direct current manner is provided, the discharge lamps 1. h filaments r,,r,,r,.

When at least one filament among f is not connected, the detection output of the voltage detection circuit 2 disappears. Since the inverter stop circuit 4 stops the oscillation of the inverter circuit 1 when the detection output of the voltage detection circuit 2 disappears, the filaments r, , r
. In addition, after the discharge lamps (1, 12) are lit normally, the discharge lamps 1..12 are removed, placed in an unloaded state, the oscillation operation of the inverter circuit 1 is stopped, and the discharge lamps 1..1. When connecting, the inverter circuit 1 starts normal oscillation operation and the discharge lamps 1..12 are relit normally only when all the filaments r,, r2.t,, r, are connected. Can be done.

In addition, the preheating circuit 7 is a discharge lamp connected in series! .

The discharge lamp 1 is cut off in terms of direct current between the non-power supply side terminals of the non-common connection side filaments r, , r of r2. ．． 12 each filament r, J2. The discharge lamp 1. ．． The detection output of the voltage detection circuit 2 is not generated only when the 12 non-common connection side filaments r+, r4 are connected, but only when all the filaments r, , r, , r, , r are connected. , the inverter circuit 1 performs an oscillation operation.

[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. A series circuit of a primary winding ■1 of a coupling capacitor C1, discharge lamps 11 and 12, an inductance element L1, and a current transformer T for current feedback is connected in parallel with one switching element Q. . The first discharge lamp! A resonance capacitor C2 is connected in parallel between the power supply side terminals of the filament f1 of the second discharge lamp 12 and the filament f4 of the second discharge lamp 12. This capacitor C2 may be a stray capacitance, and the filament r of the discharge lamp 12
The non-power supply side terminal of No. 4 is connected to the non-power supply side terminal of the filament r of the discharge lamp II via the capacitor C1 and the primary winding N1 of the preheating current transformer T2. Also, both electric lights 1. ．． The other filament rz, L of 12 constitutes a series circuit, and the secondary winding N of the current transformer T is connected to this series circuit via a capacitor C2. The current transformer T2 and the capacitor C4 constitute a preheating circuit 7 for the filaments r, , r, , r, l, r.

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

One end of the coupling capacitor C5 is connected to the positive input terminal of the inverter circuit 1, and the discharge lamp it, A series circuit of resistors R4 and R5 having an impedance higher than that of resistor b is connected.

The voltage obtained at the connection point of the resistors R, , R3 is the detection output of the voltage detection circuit 2.

Next, the configuration of the filament connection circuit 3 will be explained. In this embodiment, as described above, one end of the secondary winding N2 of the current transformer T2 in the preheating circuit 7 is connected to the first winding through the capacitor C9. Discharge lamp! , the other end of the secondary winding n2 is connected to one end of the filament r of the second discharge lamp r2, and the other ends of the filaments f2+r3 are connected.

A resistor R is connected between the non-power supply side terminal of the filament f of the discharge lamp 11 and the connection point of the capacitor C9 and the filament r2.
8 is connected, and a resistor R1 is connected between the non-power supply side terminal of the filament f4 of the discharge lamp 12 and the connection point between the secondary winding N2 of the current transformer T2 and the filament fi.

This capacitor C3 and resistors R and R constitute a filament connection circuit 3.

Next, the configuration of the inverter stop circuit 4 will be explained.

Voltage detection port i? The detection output of 82 is the resistance R? It is input to the base of transistor Q through. (2) The emitter of the transistor Q is connected to the negative input terminal of the inverter circuit 1. The collector of transistor Q5 is
It is connected to the positive input terminal a of the inverter circuit 1 via the resistor R, and also to the base of the transistor Q4. The collector of the transistor Q is connected to the base of a switching element Q2 made of a transistor, and the emitter is connected to the negative input terminal of the inverter circuit 1. In this inverter stop circuit 4, when the detection output of the voltage detection circuit 2 becomes "Low" level, the transistor Q is turned off, the transistor Q4 is turned on, and the switching element Q2 is forcibly turned off. be. Furthermore, when the detection output of the voltage detection circuit 2 is at the 'High' level, the transistor Q5 is turned on, the transistor Q is turned off, and the switching element Q2 responds to the output of the secondary winding n of the current transformer T. It turns on and off normally.

The current transformer T1 for current feedback has two secondary windings +
12. One secondary winding #JAn2 is connected between the base and emitter of the switching element Q through a bias resistor R1, and the other secondary winding n3 is connected to the switching element Q through a bias resistor R2. Q2 base
Connected between emitters. This constitutes the drive circuit 5.

Furthermore, a series circuit of a resistor R1 and a capacitor C1 is connected between input terminals a and b of the inverter circuit 1, and a resistor R1 is connected in series with a capacitor C1.
The connection point between 5 and capacitor C1 is connected to the base of switching element Q2 via diac Q, and
It is connected to the collector of the switching element Q2 via the anode and cathode of the diode D. These resistor R1, capacitor C1, diac Q, and diode D.

constitutes a starting circuit 6 of the inverter circuit 1. Note that the switching elements Q, Q2 include diodes D,
, D, are connected in antiparallel, but these diodes D t , 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 C2 is charged via the resistor R1. When the voltage of capacitor C reaches the breakover voltage of diac Q, diac Q becomes conductive and the charge in capacitor C1 is discharged through the base-emitter of switching element Q2. This turns on switching element Q2. Thereafter, the switching elements Q, , Q are alternately turned on and off by the feedback current obtained from the secondary winding n 2 + 13 of the current transformer T for current feedback. 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 R, , R, becomes a "High" level, and the detection output of the voltage detection circuit 2 becomes a "High" level. This turns on transistor Q. Therefore, bias resistance R
The base current to transistor Q, through - is cut off, and transistor Q, is turned off. At this time, since the driving current is applied to the switching element Q2 from the current transformer T, the inverter circuit 1 normally performs the oscillation operation. In a steady state, the inductance element L1
A high frequency high voltage is applied to the discharge lamp 1 by the LC resonant circuit composed of capacitors C6 and C2. ．． 12, the voltage is applied to both ends of the discharge lamp 1. ．． 1. lights up.

Here, discharge lamp 1. ,l, filament r,,r2
．． r.

When at least one filament of f is removed to create an unloaded state, the coupling capacitor C1
is charged in only one direction through the resistors R, ,R, to the same voltage level as the DC power supply E, so the input voltage to the voltage detection circuit 2 becomes low, and the detection output of the voltage detection circuit 2 becomes the “Lou+” level. Therefore, transistor Q is turned off, base current flows to transistor Q4 via bias resistor R5, and transistor Q4 is turned on. When the transistor Q is turned on, one of the switching elements Q2 is forcibly turned off, so that the secondary winding an21n3 of the current feedback current transformer T cannot obtain a feedback current, and the switching element Q1
．． Q2 are both turned off. Therefore, the oscillation of the inverter circuit 1 is stopped.

Figure 3(a) shows the state of the filament detection circuit 3 when the filaments r,,r,,t,,r, come off.
In FIG. 0 shown in (cl), portions labeled a to d correspond to portions labeled with the same symbols in FIG.

In the state shown in FIG. 3(a), since filament r is detached, filament f, J2. A closed loop on the load side (loop indicated by a - dotted line) connecting f, , f is not formed. Therefore, the coupling capacitor CI
cannot be discharged due to the closed loop, the coupling capacitor C1 is charged only in one direction via the resistor R1°R5, and is charged to the same voltage level as the DC power supply E, so one end of the resistor R1 (0 The potential of point) is ゛Lo1
It will be 11 rubles. Therefore, the detection output of the voltage detection circuit 2 is at the lowI+ level, and the transistor Q of the inverter stop circuit 4 is turned off.

is turned off, and the transistor Q, via the bias resistor R6,
Base current flows to turn on transistor Q4,
Since the switching element Q2 is forcibly turned off, the oscillation of the inverter circuit 1 is stopped. Similarly, as shown in FIGS. 3(b), (c), and (d), filament r2. Even if r, , r4 comes off, a closed loop on the load side (indicated by a broken line) connecting filaments r, , r, , r, , r is not formed, and for the same reason as above, the inverter circuit 1 oscillates. will stop. In short, discharge lamp 1. ．． 1. filament L, f2
．． When at least one filament among fi and L is removed, the oscillation of the inverter circuit 1 is stopped. In addition, the filament island, resistor R6, capacitor C7,
Since the current path connecting the current transformer T2, the resistor R9, and the filament "," is cut off in a DC manner by the capacitor C7, the coupling capacitor C1 is not discharged via this current path.

Also, discharge lamp 1. ．． After lighting the discharge lamp 1.12 normally, the discharge lamp 1. ．． 12 to put it in a no-load state, stop the oscillation operation of the inverter circuit 1, and then connect the discharge lamps 11 and 12 again. Unless all the filaments are connected, the filaments shown in Figures 3 (a) to (d) I.L., fz.

No closed loop is formed connecting f, ,f, i.e. filaments r, , r2 . The detection voltage of the voltage detection circuit 2 remains at "Low" level until r, , r are all connected, and the oscillation operation of the inverter circuit 1 does not start.

In this way, the discharge lamp 1. ．． 12 filaments r,,r
,,r,.

Regardless of the connection order of "4", only after all the filaments are connected is the resistor R3 connected in parallel with the switching element Q1, the diode D7, the primary winding n1 of the current transformer T1, the inductance element L filament "1, the resistor R1 , the charge of the capacitor CI is released via the filaments r, , r2, the resistor R1, and the filament f1,
The charging voltage of the capacitor C1 decreases, and as a result, the input voltage of the voltage detection circuit 2 becomes high level. Voltage detection circuit 2
When the input voltage of the discharge lamp 1 becomes high level, a voltage detection output is generated, so the operation of the inverter stop circuit 4 is canceled and the inverter circuit 1 starts normal oscillation operation again, and the discharge lamp 1. ．． 1. The light is turned on again.

[Example 2] FIG. 4 is a circuit diagram of a second embodiment of the present invention.

In this embodiment, the current transformer T2 for preheating is not used, and an inductance element through which the load current flows is used.
A secondary winding is provided, one end of the secondary winding is connected to one end of the filament r in the discharge lamp 12 via a capacitor C9, and the other end of the secondary winding is connected to one end of the filament r2 in the discharge lamp 11. Connect filament r2. The other ends of r, are connected.

The voltage detection circuit 2 also has a coupling capacitor C.
One end of I (0 point) and the negative input terminal of inverter circuit 1 (
diode D1 connected between point b) and discharge lamp 1
．． ．． 12, a higher impedance resistor R4.

It is composed of a series circuit of R9. This diode D4
The inverter circuit 1 absorbs noise components such as surge voltage generated during the oscillation operation of the inverter circuit 1, and stabilizes the operation of the inverter circuit 1. Moreover, the impedance Z connected in parallel with the switching element Q1 is the discharge lamp e, , 1
2 is removed to stop the oscillation operation of the inverter circuit 1, and then the discharge lamp e+ and 12 are connected again. Electric light 1. ．． 12 filaments r,, r2. r.

The detection output of the voltage detection circuit 2 becomes "High+" level only after all of the voltage detection circuit 2 is connected. The other configurations and operations are the same as those of implementation side 1, so duplicate explanations will be omitted.

In addition, as a modified example of the present invention, instead of completely stopping the oscillation of the inverter circuit 1, the switching elements Q, , Q2 are changed so that the oscillation output of the inverter circuit 1 is reduced.
It is also possible to adopt a configuration in which the switching operation of the controller is controlled.

[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. All the filaments of the discharge lamps connected in series are connected in series in a direct current manner, and the non-power side terminals of the non-common connection side filaments of the discharge lamps connected in series are cut off in a direct current manner to apply a preheating current to each filament of the discharge lamp. Therefore, if any one of the filaments of the discharge lamps connected in series becomes disconnected, the detection output of the voltage detection circuit for detecting the no-load state of the inverter circuit disappears. It is possible to stop the oscillation of the inverter circuit, and when connecting the discharge lamp again from a state where the oscillation of the inverter circuit has stopped, regardless of the order in which the filaments are connected, the inverter circuit cannot be connected again until all filaments are connected. The circuit starts normal oscillation operation and the discharge lamp can be lit again.
This has the effect of preventing wasteful power consumption and 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 figures are circuit diagrams of the first embodiment of the present invention, and Figures 3(a) to (
d) is a circuit diagram of the main part of the same as above, FIG. 4 is a circuit diagram of a second embodiment of the present invention, FIG. 5 is a circuit diagram of a conventional example, and FIG. 6 is a circuit diagram of another conventional example. 1 is an inverter circuit, 2 is a voltage detection circuit, 3 is a filament connection circuit, 4 is an inverter stop circuit, 7 is a pre-on
Road, 1. ．． 12@i discharge lamp, r+, f2. rz, L is filament I.

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 connection circuit connects all the filaments of the discharge lamps connected in series in series so that the detection output of the voltage detection circuit is generated only when all the filaments of the electric lamp are connected, and a filament connection circuit connects all the filaments of the discharge lamps connected in series in series. A preheating circuit supplies a preheating current to each filament of the discharge lamp by interrupting the non-power supply side terminals of the filament on the non-common connection side of the lamp, and an inverter when the detection output of the voltage detection circuit disappears. A discharge lamp lighting device comprising an inverter stop circuit that stops oscillation of the circuit.