JPH01246794A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To prevent wasteful consumption of power and suppress generation of excessive voltage by furnishing a circuit to stop oscillation of 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 output 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 inverter stop circuit 4 stops oscillation 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. 7 is a circuit diagram showing a conventional inverter circuit used in a discharge lamp lighting device. In FIG. 7, 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 C1, a load R, an inductance element L1, and a primary winding n1 of a current transformer T is connected in parallel with at least one switching element Q1 among these switching elements Q, Q2. It 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 constituted by a voltage divider circuit using a resistor element with higher impedance than the load R, etc.
This is to detect the presence or absence of 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. Furthermore, when the load R is connected, the capacitor C1 is charged to a voltage level approximately half that of the DC power source E, and the input voltage of the voltage detection circuit 2 becomes a high level. When the detection output from the voltage detection circuit 2 disappears, the inverter stop circuit 4 turns off the transistor Q5, turns on the transistor Q, and forcibly turns off the switching element Q2, thereby switching the switching elements Q1 and Q2. It stops the operation.

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 T. 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, if the load R is removed and there is no load, the capacitor CI will be charged in only one direction via the resistors R4 and R5, and will be charged to the same voltage as the DC power supply E, so the detection output of the voltage detection circuit 2 will be 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 charge in the capacitor C2 is transferred through the switching element Q, the resistor R5 connected in parallel, the diode D5, the primary winding n3 of the current transformer T1, the inductance element L1, and the load R. is released, 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 12 discharge lamps L is shown in FIG.

In this circuit, the non-power supply side terminal of the filament r of the discharge lamp 12 is connected to the filament of the discharge lamp l through a parallel circuit of a capacitor C4 and a resistor R6, and the primary winding N of a current transformer T for preheating. It is connected to the non-power supply side terminal of f1. Further, the other filaments fz and fs of both lamps It and b are connected in series to the secondary winding N2 of the current transformer T2. With these resistor R6, capacitor C4 and current transformer T2, filaments r, , t2 . f.

A preheating circuit 7 of f.

Here, if the discharge lamp b is a round tube type, the sockets for the pair of filaments are integrated, so both filaments are connected almost at the same time, but if the discharge lamp is a straight tube type Each filament socket is independent. Therefore, as shown in FIG.
．． ．． 1. When connected in series, each filament r, , r2 . r3. r.

Each socket is independent. For this reason, for example, when connecting the discharge lamp 12 first and then the discharge lamp, there is no problem if you connect the filament R first, but if you connect the filament 1 first, the filament L, Since the electric charge of the capacitor C4 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, and the switching element Since a large resonant current flows through Q,,Q2, the switching element Q1.Q
There is a problem that the switching loss of No. 2 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 a lighting fixture, a discharge lamp 1. ．． 12
In circuits where the power supply is not insulated, output voltages exceeding 300V in effective value do not comply with the Electrical Appliance and Material Control Act and JIS standards, so it is necessary to prevent the generation of such excessive voltages. .

Further, a similar problem occurs when the filament is disconnected. When filament r or f of the filaments on the non-common side of discharge lamps 1+ and 12 is disconnected, there will be a complete no-load state, so voltage detection circuit 2 will operate normally and oscillation of inverter circuit 1 will stop. do. However,
When the filament ``2'' or ``r'' 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 is only applicable 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 the inverter circuit starts oscillating 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 source E, one end of a capacitor C1 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. A discharge lamp 1 connected in series between the other end and the connection point of the first and second switching elements Q, Q,
．． ．． 12 is connected via an inductance element Ll, and the first and second switching elements Q, ,Q
, alternately turn on and off, discharge lamp 1. ．． In the discharge lamp lighting device, the discharge lamp lighting device includes an inverter circuit 1 for supplying AC power to a DC power source E, and a voltage detection circuit 2 connected between the other end of the capacitor CI and the other end of the DC power source E. To, 12 commonly connected filaments r
2. r, is provided, and when at least one of the detection outputs of the filament detection circuit 3 and the voltage detection circuit 2 disappears, the inverter circuit 1
The present invention is characterized in that an inverter stop circuit 4 is provided to stop the oscillation of the inverter.

[Function] According to the present invention, the discharge lamps are connected in series! , 12 commonly connected filaments f,.

Since the filament detection circuit 3 is provided to detect r,
When the filament f2 or r is not connected, the detection output of the filament detection circuit 3 disappears. Further, the voltage detection circuit 2 connected between the other end of the capacitor C1 and the other end of the DC power supply E has filaments r, , r,
is detected, and when the filament fl or f4 is not connected, the detection output of the voltage detection circuit 2 disappears.In the present invention, at least one of the detection outputs of the voltage detection circuit 2 and the filament detection circuit 3 is detected. Since the oscillation of the inverter circuit 1 is stopped by the inverter stop circuit 4 when the filament disappears, the oscillation of the inverter circuit 1 is stopped when any filament is not connected, thereby preventing wasteful power consumption. As well as being able to
This can 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. This inverter circuit 1 includes switching elements Q, , Q made up of transistors.

An input DC voltage is applied to a series circuit of switching elements Q, , Q2. One switching element Q
, in parallel with the coupling capacitor CI, the discharge lamp! , and l7, an inductance element 3, and a primary winding n of a current transformer T1 for current feedback are connected in series. A resonance capacitor C2 is connected in parallel between the power supply side terminals of the filament fl of the first discharge lamp p and the filament f of the second discharge lamp 12. This capacitor C2 may be a stray capacitance. It is connected to the non-power supply side terminal of the filament r of No. 11. In addition, both electric lights 1. ．． 12 other filaments f2. f constitutes a series circuit, and two current transformers T2 are connected to this series circuit.
The next winding is connected via capacitor C3. The current transformer T2, the resistor R6, and the capacitor C4 connect the filament f1. fz, fs, fi preheating circuit 7
is configured.

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

One end of the coupling capacitor CI is connected to the positive input terminal of the inverter circuit 1, and between the other end of the coupling capacitor CI and the negative input terminal of the inverter circuit 1, a discharge lamp L, A series circuit of resistors R4 and Rs having a higher impedance than b is connected. The voltage obtained at the connection point of the resistors R, , R% is the detection output of the voltage detection circuit 2.

Next, the configuration of the filament detection circuit 3 will be explained. In this embodiment, as described above, one end of the secondary winding of the current transformer T2 in the preheating circuit 7 is connected to the first winding through the capacitor C6. It is connected to one end of the filament r2 in the discharge lamp 11, the other end of the secondary winding is connected to one end of the filament r in the second discharge lamp 12, and the other ends of the filaments ft and fs are connected. The connection point between capacitor C1 and filament f2 is connected to the positive input terminal of inverter circuit 1 via resistor R0, and the connection point between the secondary winding of current transformer T2 and filament f is connected via resistor R10. It is connected to the negative input terminal C of the inverter circuit 1.The capacitor C5 and the resistor R1
The filament detection circuit 3 is constituted by the resistor R1 and R11, and the voltage at one end (point a) of the resistor R1 is the detection output of the filament detection circuit 3.

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

The detection output of the voltage detection circuit 2 is the resistance R? It is input to the base of transistor Q through. Further, the detection output of the filament detection circuit 3 is input to the base of the transistor Q6 via the resistor R1. The emitter of each transistor Q, ,Q, is connected to the negative input terminal C of the inverter circuit 1. The collectors of the transistors Q, Q, are connected to the positive input terminal of the inverter circuit 1 via resistors Rlt and R13, respectively, and are connected to the transistor Q4 via the anodes and cathodes of diodes D4 and Ds, respectively. connected to the base of. The collector of the transistor Q is connected to the base of the switching element Q2, and the emitter is connected to the negative input terminal C of the inverter circuit 1.

In this inverter stop circuit 4, when at least one of the detection output of the voltage detection circuit 2 and the detection output of the filament detection circuit 3 becomes "High" level, the transistor Q is turned on and the switching element Q is forced to operate. This is to turn it off.

Also, if both rain detection outputs are at “Low” level,
Transistor Q4 is turned off and switching element Q2
is normally turned on and off according to the output of the secondary winding n of the current transformer T1.

The current transformer T1 for current feedback has two secondary windings n
2*13, one secondary winding n2 is connected between the base and emitter of the switching element Q through a bias resistor R1, and the other secondary winding n is connected through a bias resistor R2. is connected between the base and emitter of switching element Q2. As a result, the drive circuit 5
is configured.

Furthermore, a series circuit of a resistor R3 and a capacitor C1 is connected between input terminals S and C of the inverter circuit 1, and a resistor F
The connection point between t's and the capacitor C5 is connected to the base of the switching element Q2 via the diac Q, and between the anode and cathode of the diode D.
It is connected to the collector of switching element Q2. These resistor R1, capacitor C5, diac Q, and diode D3 constitute a starting circuit 6 of the inverter circuit 1. Note that the switching elements Q, ,Q, have the following:
Although the diodes D, , D2 are connected in antiparallel, these diodes D, , D2 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 R5. When the voltage of the capacitor C3 reaches the breakover voltage of the diac Q3, the diac Q becomes conductive and the charge stored in the capacitor C1 is discharged through the base-emitter of the switching element Q2. This turns on switching element Q2. Thereafter, the switching elements Q, Q2 are turned on alternately by the feedback current obtained from the secondary windings 1□, n of the current transformer T1 for current feedback.
It will be turned off. At this time, the coupling capacitor C
1 is charged with a voltage E/2, which is about half of the DC power supply E. Therefore, the voltage divided by the resistors R4 and Rs is “I
-l-1i" level, and the detection output of the voltage detection circuit 2 becomes "High" level. As a result, the transistor Q5 is turned on, and the base current to the transistor Q via the bias resistor R12 and the diode D is Be cut off.

Here, when at least one of the filaments f, , f of the discharge lamp b is removed to create an unloaded state, the coupling capacitor C3 is charged only in one direction via the resistors R4 and Rs, and the DC power source Since it is charged to the same voltage level as E, the input voltage to the voltage detection circuit 2 becomes low, and the detection output of the voltage detection circuit 2 becomes a "Low" level. Therefore, the transistor Q5 is turned off, and the base current flows to the transistor Q4 via the bias resistor R1□.
Transistor Q4 turns on. When the transistor Q is turned on, one of the switching elements Q is forcibly turned off, so that no feedback current can be obtained from the secondary windings n2 and R3 of the current transformer T for current feedback. Both switching elements Q, , Q are in the off state.

Therefore, the oscillation of the inverter circuit 1 is stopped.

Next, when at least one of the filaments fz and L of the discharge lamp b comes off, the detection output of the filament detection circuit 3 becomes "Low" level. Now filament f
FIG. 3 shows the state of the filament detection circuit 3 when only . In the state shown in FIG. 3, filament r is detached, so current path A through filaments fz and b is not formed, and current path B through the secondary winding of current transformer T2 is connected to the DC power source. Since the direct current from E is blocked by capacitor C6, this current path is not formed either. Therefore, no current flows through resistor R1°, and the potential at one end (point a) of resistor R10 becomes "L o
s" level. Therefore, the filament detection circuit 3
The detection output of becomes "Low" level, the transistor Q of the inverter stop circuit 4 is turned off, and the bias resistor R1 is turned off.
A base current flows through the transistor Q4 through the transistor Q3 and the diode D, turning on the transistor Q4 and forcibly turning off the switching element Q2, so that the oscillation of the inverter circuit 1 is stopped. Even if only the filament r2 of the discharge lamp comes off, the oscillation of the inverter circuit 1 will stop for the same reason as above.

On the other hand, when the filaments ft and rs of the discharge lamp To are connected together, current flows through the current path A in Figure 3, so a voltage is generated across the resistor R1°.
The detection output of the filament detection circuit 3 becomes "High" level. Therefore, transistor Q is turned on,
The base current to the transistor Q4 via the bias resistor R1 is cut off.

Total filament fl of discharge lamp 1+,'lt,[2,N3
．． When f4 is connected, both the detection output of voltage detection circuit 2 and the detection output of filament detection circuit 3 are “H”.
"high" level, and the transistors Q s and Q
- are both turned on. Therefore, bias resistor R12
The base currents to the transistor Q through R1 are both cut off, and the transistor Q4 is turned off.

At this time, since a driving current is applied from the current transformer T to the switching element Q2, the inverter circuit 1 normally performs the oscillation operation. Due to the high frequency and high voltage discharge lamp j!
+ is applied to both ends of 1□, and the discharge lamp, et, is lit.

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

In this embodiment, one end of the secondary winding of the preheating current transformer T2 is connected to the discharge lamp 11.
N2 is connected to one end of each of filaments fi, f* on the common side, and the other end of the secondary winding is connected to filament r2. r
, connected to each other end of the . That is, in this embodiment, filament r2. r, are connected in parallel.

One end of each filament r, , r is connected to the positive input terminal C of the inverter circuit 1 via a resistor R8, and the other end is connected to the negative input terminal C of the inverter circuit 1 via a resistor RIO. The voltage at one end (point a) of the resistor R3° is applied to one input terminal of the comparator CP. A reference voltage V is applied to the other input terminal of the comparator CP. This comparator CP and reference voltage ■8
The capacitor C2 and the resistors R1° and Ro constitute a filament detection circuit 3, and the output of the comparator CP serves as the detection output of the filament detection circuit 3. The other configurations are the same as in the first embodiment, so parts having the same functions are given the same reference numerals and redundant explanations will be omitted.

In the following, the operation of this embodiment will be explained. In this embodiment, the filament r2 on the common side of the discharge lamp, lit.
．． Since r, are connected in parallel, both filaments f2
．． When f, is connected normally, the filament resistors Rf, , Rf of both filaments rz, L are connected in parallel to the resistors R11 and RIo. At this time, let the voltage generated at one end (point a) of the resistor R1° be e, and this voltage e is higher than the reference voltage V of the comparator CP.
The reference voltage VR is set so that ,
When the voltage generated at one end (point a) of the resistor R1° is greater than the reference voltage VR, the output of the comparator CP becomes a "High" level. Therefore, when the filaments r, , r are connected normally, the output of the filament detection circuit 3 becomes a "High" level.

Next, filament r2. When one of r is removed, the filament resistance decreases by one, so the current flowing through the filament detection circuit 3 decreases. Now, the state of the filament detection circuit 3 when only the filament f2 has come off is shown in FIG. It corresponds to

In the state shown in FIG. 5, filament r2 is removed, so there is no current path through resistor Rf2, and resistor R
The only current path is through f. For this reason, the resistance R,
The current flowing through o decreases and one end of resistor R6° (a
The voltage generated at point ) also decreases. This voltage is referred to as e2, and the reference voltage vR is set so that the reference voltage ■R of the comparator CP is higher than this voltage e.

When the voltage generated at one end (point a) of the resistor R1° is smaller than the reference voltage VR, the output of the comparator CP becomes "Low" level. Therefore, filament f
2 is not connected, the output of the filament detection circuit 3 becomes "Low" level. filament f,
Even when the is not connected, for the same reason as above,
The output of the filament detection circuit 3 becomes the °'Lo-" level.

Furthermore, when both filaments t and f are removed, the current path through filaments ft and fs disappears, and the current path through the secondary winding of current transformer T2 is cut off in terms of direct current by capacitor C6. Resistance R
At 1°, no current flows, and the voltage at one end (point a) becomes “Lo-” level. Therefore, the output of the comparator CP is also at the "low" level, and the output of the filament detection circuit 3 is at the low level.

Other operations are the same as in the first embodiment.

[Third Embodiment] FIG. 6 is a circuit diagram of a main part of a third embodiment of the present invention. In this embodiment, the capacitor C2 in the circuit shown in FIG. 2 is replaced with a diode D6. In this case, when the filaments f2°f of discharge lamps 1+ and b are connected together, a current flows from the DC power supply E through the resistor R8, the filament f2+, and the resistor R1°, and one end of the resistor R1° ( Since the voltage level at point a) increases, the detection output of the filament detection circuit 3 becomes "High" level. At this time, filament f2. L is DC preheated by the output of the current transformer T2 via the diode D6.

Next, when at least one of the filaments L and f- comes off, the current path passing through the filaments f, , f is cut off, and the current path passing through the secondary winding of the current transformer T2 is connected to the DC current path by the diode D6. As a result, no current flows through the resistor R2°, and the voltage level at one end (point a) of the resistor R2° decreases. Therefore, the detection output of the filament detection circuit 3 becomes "Low" level. Other operations are the same as in the first embodiment.

In addition, as a modified example of the present invention, instead of completely stopping the oscillation of the inverter circuit 1, switching elements Q, , Q are provided 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 No. 2 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. a filament detection circuit for detecting commonly connected filaments of the discharge lamps, and an inverter stop circuit for stopping oscillation of the inverter circuit when at least one of the detection outputs of the filament detection circuit and the voltage detection circuit disappears. Therefore, 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, and the oscillation of the inverter circuit is stopped. When the filament on the common side of the discharge lamp is not connected, the detection output of the filament detection circuit disappears, and the oscillation of the inverter circuit is stopped. Therefore, the oscillation of the inverter circuit is stopped. If any one of them is disconnected, the oscillation of the inverter circuit can be stopped, which 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.
3 is a circuit diagram of the first embodiment of the present invention, FIG. 3 is a circuit diagram of the same essential parts as above, FIG. 4 is a circuit diagram of a second embodiment of the present invention, FIG. 5 is a circuit diagram of essential parts of the same as above, FIG. 6 is a circuit diagram of a main part of a third embodiment of the present invention, FIG. 7 is a circuit diagram of a conventional example, and FIG. 8 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 inverter stop circuit, ZIJ2 is a discharge lamp, f, , f2. f,,f, are filaments.

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 inverter stop circuit is provided for stopping oscillation of an inverter circuit when at least one of the detection outputs of the filament detection circuit and the voltage detection circuit disappears. Characteristic discharge lamp lighting device.