JPH11162677A - Discharge-lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an inverter circuit from being destroyed by heat, by surely halting oscillation of the inverter circuit on detecting non-attachment of a discharge lamp. SOLUTION: In the event that the number of discharge lamp FL as the load is one, when at least one filament of the discharge lamp is open open circuited, based on voltage detected by a first or second detecting circuit 5, 6, a first or second comparator CP1, CP2 detects that the filament is in a non-attachment state and a control circuit 3, receiving a detection signal of the non-attachment state from the first or second comparator CP1, CP2, halts oscillation of an inverter circuit 2, whereby switching elements of the inverter circuit are prevented from being destroyed by heat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for starting and lighting a discharge lamp at a high frequency.

[0002]

FIG. 7 is a circuit diagram of a conventional discharge lamp lighting device described in Japanese Patent Application Laid-Open No. 8-339891. FIG.
, 1 is a DC power supply, 2 is a MOS-FET Q1, Q
2 is an inverter circuit, 3 is a control circuit for controlling the operation of the inverter circuit 2, 4 is a DC power supply circuit for driving the control circuit 3, L is a ballast choke which is a load current limiting inductance element, and FL is a discharge lamp. , C2 are preheating capacitors connected in parallel to the discharge lamp FL, and C3 is a DC blocking capacitor.

[0003] The inverter circuit 2 includes a MOS-FET Q
An ON signal is alternately supplied from the control circuit 3 connected to the gates of the transistors 1 and Q2 to alternately turn on and off. And M
A load circuit is connected between the drain and the source of the OS-FET Q2. That is, a series resonance circuit composed of a parallel circuit of a ballast choke L as a load current limiting inductance element, a discharge lamp FL and a resonance preheating capacitor C2 is connected via a DC blocking capacitor C3. The DC power supply circuit 4 includes a secondary winding of a ballast choke L, a resistor R3,
It includes a diode D3, a capacitor C4, and a Zener diode DZ2.

Here, when a high-frequency current flows through the ballast choke L and a high-frequency voltage is generated in the secondary winding, the DC power supply circuit 4 rectifies the high-frequency voltage with a diode D3, and thereafter smoothes the high-frequency voltage with a capacitor C4, and smoothes the DC voltage. Get the voltage. The Zener diode DZ2 is connected to stabilize the DC voltage, and the resistor R3 is connected as a current limiting resistor for limiting the Zener current flowing through the Zener diode DZ2.

Next, the operation of the conventional discharge lamp lighting device shown in FIG. 7 will be described. First, when the discharge lamp FL is mounted, the load circuit is in a closed state.
-The high-frequency current flows through the load circuit by the on / off operation of the FETs Q1 and Q2. When the high-frequency current flows, a high-frequency voltage is generated in the secondary winding of the ballast choke L. The high-frequency voltage is rectified and smoothed by the diode D3 and the capacitor C4 to obtain a DC voltage. The control circuit 3 continues to control the ON / OFF operation of the MOS-FETs Q1 and Q2 using the DC voltage thus obtained as a power supply. Next, when the discharge lamp FL is not mounted, the load circuit is in an open state.
Even if 1 and Q2 are turned on and off, no high-frequency current flows through the load circuit. Therefore, no high-frequency voltage is generated in the secondary winding of the ballast choke L, so that a DC voltage cannot be obtained at the capacitor C4. That is, since power is not supplied to the control circuit 3, control of the ON / OFF operation of the MOS-FETs Q1 and Q2 cannot be continued. That is, the inverter circuit 2 stops operating.

FIG. 8 is a circuit diagram of another conventional discharge lamp lighting device described in Japanese Patent Application Laid-Open No. 1-39270. In FIG. 8, 1 is a DC power supply, 2 is a transistor Q
1, an inverter circuit composed of Q2 and regenerative diodes D10 and D11, 3 is a control circuit for controlling the operation of the inverter circuit, 4 is a DC power supply circuit for driving the control circuit 3, and La and Lb are load current limiting inductances. Ballast chokes, FLa and FLb, are discharge lamps and C
2a and C2b are preheating capacitors respectively connected in parallel to the discharge lamps FLa and FLb, and C3 is a DC blocking capacitor.

The inverter circuit 2 includes transistors Q
An ON signal is alternately supplied from a control circuit connected to the bases of Q1 and Q2 to alternately turn on and off. Regeneration diodes D10 and D11 are connected in the reverse direction between the collectors and emitters of the transistors Q1 and Q2, respectively.
Two loads are connected in parallel between the collector and the emitter of the transistor Q2. That is, the ballast choke La, which is a load current limiting inductance element,
A series resonance circuit composed of a parallel circuit of a discharge lamp FLa and a preheating capacitor C2a is connected via a DC blocking capacitor C3. Similarly, a ballast choke Lb which is a load current limiting inductance element, a discharge lamp FLb and a preheating capacitor C2b are connected. A series resonance circuit composed of a parallel circuit is connected via a DC blocking capacitor C3. The DC power supply circuit 4 includes secondary windings of ballast chokes La and Lb, diodes D3a and D3b, and a capacitor C4.

Here, when a high-frequency current flows through the ballast choke La or Lb to generate a high-frequency voltage in the secondary winding, the DC power supply circuit 4 converts the high-frequency voltage into a diode D3.
The voltage is rectified by a or D3b and then smoothed by a capacitor C4 to obtain a DC voltage. The diode D3
Since a and D3b are OR-connected, if a voltage is generated in one of the secondary windings of the ballast chokes La or Lb, the DC power supply is connected even if no voltage is generated in the other secondary winding. Obtainable.

Next, the operation of another conventional discharge lamp lighting device shown in FIG. 8 will be described. First, the discharge lamps FLa, FL
When both lamps are mounted, the two load circuits connected in parallel are both in a closed state, so that the high-frequency current flows through both load circuits by the on / off operation of the transistors Q1 and Q2. It will flow. When the high-frequency current flows, a high-frequency voltage is generated in the secondary windings of the ballast chokes La and Lb. The voltage generated in the secondary winding of the ballast choke La is rectified by the diode D3a, and the voltage generated in the secondary winding of the ballast choke Lb is rectified by the diode D3b. Get. The control circuit 3 continues to control the on / off operations of the transistors Q1 and Q2 using the DC voltage thus obtained as a power supply.

Next, when one discharge lamp is mounted (FLa) and one discharge lamp is not mounted (FLb), the load circuit corresponding to the discharge lamp FLa is closed and corresponds to the discharge lamp FLb. Since the load circuit is open, the transistors Q1,
By the ON / OFF operation of Q2, the high-frequency current does not flow through the load circuit on the discharge lamp FLb side, but the high-frequency current flows through the load circuit on the discharge lamp FLa side. The high-frequency current flows in such a manner that the ballast choke L
No high-frequency voltage is generated in the secondary winding on the b side, but a high-frequency voltage is generated in the secondary winding of the ballast choke La.
Then, the voltage generated in the secondary winding of the ballast choke La is rectified by the diode D3a, and then smoothed by the capacitor C4 to obtain a DC voltage. Control circuit 3
Uses the DC voltage obtained as described above as a power supply to continue controlling on / off operations of the transistors Q1 and Q2.

When the two discharge lamps FLa and FLb are not mounted, the two load circuits connected in parallel are both open, so that the transistors Q1 and Q2
, The high-frequency current does not flow in either load circuit. Therefore, ballast chokes La and L
Since no high-frequency voltage is generated in the secondary winding b, a DC voltage cannot be obtained at the capacitor C4. That is, since power is not supplied to the control circuit 3, the transistor Q
1, the control of the on / off operation of Q2 cannot be continued. That is, the inverter circuit 2 stops operating.

[0012]

In any of the conventional discharge lamp lighting devices, when the discharge lamp is not mounted, the load circuit of the inverter circuit 2 is in an open state, so that no current flows through the load circuit and the ballast choke. Since no voltage is generated in the L secondary winding, the DC power supply circuit 4 cannot be generated. Therefore, the inverter circuit 2 stops operating.

By the way, in the case of an actual fluorescent lighting equipment,
As shown in FIG.
There are four terminals, which are connected between the printed circuit board of the inverter circuit 2 and the fluorescent lamps by four wires per lamp. By connecting with electric wires, there is equivalently a minute capacitance as shown by a broken line in FIG. 9B between these four electric wires. This capacitance varies depending on the length of the electric wire, but is as small as about several pF to several tens pF. Then, as shown in FIG.
If a capacitor exists between the terminals, for example, even if the fluorescent lamp is not mounted, it is actually closed as a load circuit. Then, although there is no load (when the lamp is not mounted) depending on the capacitance between the four terminals, the inverter circuit 2 continues to oscillate by the same mechanism as when the load (when the lamp is mounted). There may be cases.

However, when the load is applied and when the load is not applied,
Even if oscillation occurs in the same manner, there is a difference in the state of the load circuit.
That is, when the load is applied, the load is inductive (the L component of the ballast choke L is dominant as the impedance of the load circuit), but when no load is applied, the extreme capacitance (the C component of the capacitance CA to CD between the four terminals increases). State which is dominant as the impedance of the load circuit). When the operation waveforms of the inverter circuit in these states are compared, the waveforms are completely different from each other at the time of load and at the time of no load, as shown in FIGS. In the waveform of FIG.
This is a portion corresponding to the loss of the OS-FET. Comparing these waveforms, the loss of the MOS-FET is much larger in the no-load waveform than in the loaded waveform. Therefore, when no load is applied, if the inverter circuit continues to oscillate, the MOS-FET may be broken due to heat generation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to surely stop the oscillation of the inverter circuit when there is no load and to prevent the inverter circuit from being damaged by heat generation. An object of the present invention is to provide an electric lighting device.

[0016]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device comprising: a DC power supply; an inverter circuit connected to the DC power supply; a DC power supply circuit connected to the DC power supply; A load circuit including a discharge lamp connected between the output terminals of the discharge lamp, a first detection circuit for detecting the impedance of one filament of the discharge lamp, and a direct current from the output terminal of the inverter circuit via the other filament of the discharge lamp. A second detection circuit connected between the negative electrode side of the power supply and indirectly detecting the discharge lamp voltage, and when an output level output from the first detection circuit is equal to or higher than a first threshold set in advance. Output the detection signal of the filament non-attached state to the first
A second comparator that outputs a detection signal of a filament non-attached state when an output level output from the second detection circuit is equal to or less than a preset second threshold value, and a DC power supply circuit. Drive control to control the operation of the inverter circuit, and control to stop the operation of the inverter circuit when receiving a filament non-attached state detection signal of at least one of the first comparator and the second comparator. And a circuit.

According to a second aspect of the present invention, there is provided a discharge lamp lighting device connected between a DC power supply, an inverter circuit connected to the DC power supply, a DC power supply circuit connected to the DC power supply, and an output terminal of the inverter circuit. A load circuit including the plurality of discharge lamps, a plurality of first detection circuits for detecting the impedance of one filament of each discharge lamp, and an output terminal of the inverter circuit via the other filament of each discharge lamp. A plurality of second detection circuits that are connected between the negative side of the DC power supply and indirectly detect the lamp voltage;
A first comparator for outputting a detection signal of a filament non-attached state when an output level outputted therefrom is equal to or more than a preset first threshold value, and a second detection circuit And a second comparator for outputting a detection signal of a filament non-attached state when an output level outputted therefrom is equal to or less than a preset second threshold value, and a first comparator corresponding to each discharge lamp. No load that outputs a detection signal when at least one of the comparator and the second comparator receives a detection signal in a filament unattached state from the first or second comparator corresponding to each discharge lamp. The operation of the inverter circuit is controlled by being driven by the discrimination circuit and the DC power supply circuit, and the operation of the inverter circuit is stopped when a filament non-attached state detection signal is received from the no-load discrimination circuit. It is constituted by a control circuit for cormorants control.

A first detection circuit of a discharge lamp lighting device according to a third aspect of the present invention is such that one end of a filament of a discharge lamp for detecting impedance is connected to a negative electrode side of the DC power supply.

The first detection circuit of the discharge lamp lighting device according to claim 4 of the present invention is provided between a positive electrode side of the DC power supply circuit and a negative electrode side of the DC power supply, and has a resistance value of the first power supply circuit. And a series circuit of a first resistor, a first diode, and a charging capacitor, which is sufficiently larger than the impedance of the filament of the discharge lamp detected by the detection circuit, and a connection point between the first resistor and the first diode. A second diode connected between one filament of the discharge lamp and the first diode and the second diode from a positive electrode of the DC power supply circuit to a negative electrode of the DC power supply. Side is connected in the direction in which the direct current flows.

A discharge lamp lighting device according to claim 5 of the present invention is provided between the DC power supply circuit and the control circuit, and includes at least one of the first comparator and the second comparator. A switch circuit is provided for interrupting the supply of power from the DC power supply circuit to the control circuit when receiving a detection signal of an unmounted state.

A discharge lamp lighting device according to a sixth aspect of the present invention is provided between the DC power supply circuit and the control circuit, and receives a filament non-attached state detection signal from the no-load determination circuit. A switch circuit for interrupting supply of power from the DC power supply circuit to the control circuit.

According to a seventh aspect of the present invention, in the discharge lamp lighting device according to the first aspect of the present invention, the first comparator differentiates when the first comparator receives the detection signal in the non-filament state and no longer receives the detection signal in the non-filament state. A reset circuit that generates a pulse and outputs a differentiated pulse to the control circuit; and the control circuit is configured to perform a sequence control of preheating, starting, and lighting of the discharge lamp in response to the differentiated pulse from the reset circuit. I have.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention. FIG.
, 1 is a DC power supply, 2 is a MOS-FET Q1, Q
2, an inverter circuit 3, a control circuit for controlling the operation of the inverter circuit 2, and a control circuit 3, including resistors R1 and R2, a capacitor C1, and a Zener diode DZ1.
L is a ballast choke which is a load current limiting inductance element, and FL is f1
And f2 are filament discharge lamps, C2 is a preheating capacitor connected in parallel to the discharge lamp FL, and C3 is a DC blocking capacitor. 5 is a filament f of the discharge lamp FL
A first detection circuit for detecting the impedance of 1 and a second detection circuit 6 for indirectly detecting the discharge lamp voltage. C
P1 is a first comparator for comparing the output of the first detection circuit 5 with the first threshold S1, and CP2 is a second comparison for comparing the output of the second detection circuit 6 with the second threshold S2. These outputs are OR-connected by diodes D1 and D2, and the OR output is input to the control circuit 3.

Next, the operation of the discharge lamp lighting device according to the first embodiment of the present invention will be described with reference to FIG. In the discharge lamp lighting device shown in FIG. 1, the first detection circuit 5 converts the impedance of the filament f1 of the discharge lamp FL into a voltage. Here, the filament f1 usually has a low impedance of about 2 to 3Ω, but when the filament f1 is in an open state due to disconnection or the like, it has a theoretically infinite high impedance. Therefore, this filament f
A voltage can be generated at both ends of the filament by passing a very small current through the filament. This filament voltage hardly occurs when the filament f1 is mounted because the filament f1 has a low impedance. However, when the filament f1 is open due to disconnection or the like, the voltage applied to the filament f1 is generated almost as it is because the impedance is high.
Then, a threshold value S1 is provided between these two voltages, and the voltage applied to the filament f1 is compared with the threshold value S1 by the first comparator CP1. As a result, the first comparator CP
No. 1 detects that the filament f1 is in the mounted state when the filament voltage is equal to or less than the threshold value S1, and conversely detects that the filament f1 is in the unmounted state when the filament voltage is equal to or more than the threshold value S1.

The second detection circuit 6 indirectly discharges the discharge lamp F
The discharge lamp voltage of L is detected. Actually, since the second detection circuit 6 is connected in parallel with the series circuit of the discharge lamp FL and the DC blocking capacitor C3, the combined voltage of the discharge lamp voltage and the DC blocking capacitor C3 is detected. Will be.
Normally, the discharge lamp voltage is a high voltage of 100 V or more by, for example, FHF32 (a high-frequency lighting dedicated lamp), and is divided into a low voltage of about several V using a resistor or the like and input to the second comparator CP2. I do. By the way, the second detection circuit 6
Are connected in series between the output terminals of the inverter circuit 2 via the ballast choke L and the filament f2 of the discharge lamp FL. Therefore, when the inverter circuit 2 oscillates, a voltage is generated in the second detection circuit 6 when the filament f2 is in the mounted state, but when the filament f2 is open due to disconnection or the like, the second detection circuit 6 generates the voltage. The detection circuit 6 hardly generates a voltage. A threshold value S2 is provided between these two voltages (a voltage divided into a low voltage of about several volts), and the divided voltage of the second detection circuit 6 and the threshold value S2 are provided by the second comparator CP2. Compare with As a result, the second comparator CP2 detects that the filament f2 is in the mounted state when the divided voltage of the second detection circuit 6 is equal to or more than the threshold value S2. If the divided voltage is equal to or less than the sound value S2, it is detected that the filament f2 is not mounted.

Further, the first or second comparator CP1, CP
2 is configured to output an H level when the non-attachment state of the filament is detected. Since these outputs are OR-connected, control is performed when at least one filament of the discharge lamp FL is not attached. The H level can be input to the circuit 3. Then, when the H level is input to the control circuit 3, the control circuit 3 operates so as to stop the oscillation of the inverter circuit 2. As described above, when only one discharge lamp FL is used as the load, and when at least one filament of the discharge lamp FL is in an open state, the first or second detection circuit 5 or 6 detects the load based on the voltage detected. 1st or 2nd
Of the first and second comparators CP1 and CP2 detect that the filament f1 or f2 is not mounted.
1. Since the control circuit 3 which has received the detection signal of the filament non-attachment state of the CP 2 stops the oscillation of the inverter circuit 2, the switching element of the inverter circuit 2 is prevented from being destroyed due to heat generation, and protection under no load is performed.

Embodiment 2 FIG. FIG. 2 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention. 2, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description of the duplicate components will be omitted. When the second embodiment shown in FIG. 2 is compared with the first embodiment shown in FIG. 1, the first embodiment uses one discharge lamp FL as a load of the inverter circuit 2.
In contrast to the lamp, in the second embodiment, the inverter circuit 2
, Two discharge lamps FL are connected in parallel.
The circuits corresponding to the respective discharge lamps FL are the same as those in FIG.
FLb, a is added to the end of the reference numeral of the circuit corresponding to the discharge lamp FLa, and b is added to the end of the reference numeral of the circuit corresponding to the discharge lamp FLb. Reference numeral 8 denotes an AND circuit which is a logic circuit serving as a no-load discriminating circuit.
Each of the comparators corresponding to FLb is connected to the OR output side, and the output side is connected to the control circuit 3.

Next, the operation of the discharge lamp lighting device according to the second embodiment of the present invention will be described with reference to FIG. In the discharge lamp lighting device shown in FIG. 2, the installation state of the filaments f1a, f2a and f1b, f2b is detected for each of the discharge lamps FLa, FLb, and these detections are exactly the same as the circuit of FIG. Done in That is, the discharge lamp F
For La, the first detection circuit 5a and the first comparator C
P1a and the threshold S1a are used to detect the mounting state of the filament f1a, and the second detection circuit 6a and the second comparator CP
2a, the mounting state of the filament f2a is detected using the threshold value S2a. Further, for the discharge lamp FLb, the mounting state of the filament f1b is detected using the first detection circuit 5b, the first comparator CP1b, and the threshold value S1b, and the second detection circuit 6b, the second comparator CP2b, The attachment state of the filament f2b is detected using the threshold value S2b.

The first and second comparators CP1a and CP2a corresponding to the discharge lamp FLa output an H level when the non-attached state of the filaments f1a and f2a is detected. Diode D1
a and D2a, the discharge lamp F
When at least one filament of La is not mounted, the H level can be input to the AND circuit 8. Similarly, the first and second comparators CP corresponding to the discharge lamp FLb
1b and CP2b output an H level when detecting the non-attachment state of the filaments f1b and f2b. Since these outputs are OR-connected by the diodes D1b and D2b, at least one of the discharge lamps FLb If no filament is attached, AND circuit 8
To the H level. The AND circuit 8 outputs an H level when at least one filament of the discharge lamp FLa is not mounted and when at least one filament of the discharge lamp FLb is not mounted. Then, when an H level is input from the AND circuit 8 to the control circuit 3, the control circuit 3 operates so as to stop the oscillation of the inverter circuit 2.

As described above, when two discharge lamps FL are connected in parallel as a load, at least one filament is open for all discharge lamps FL, that is, one discharge lamp FL is connected.
When at least one filament of La is not mounted and at least one filament of the other discharge lamp FLb is not mounted, one discharge lamp F is connected to the AND circuit 8.
The detection signal of the first or second comparator CP1, CP2 in the filament non-attached state in La and the other discharge lamp FLb
Of the first or second comparator CP1 or CP2 in the non-attached state of the filament is input, the AND circuit 8 outputs a detection signal of the non-attached state of the filament to the control circuit 3, and Since the control circuit 3 that has received the detection signal stops the oscillation of the inverter circuit 2, the switching element of the inverter circuit 2 is prevented from being destroyed due to heat generation, and so-called no-load protection is performed.

If at least one of the normal discharge lamps FLa and FLb with the filaments mounted at both ends is present, the AND circuit 8 does not output a detection signal indicating that the filament is not mounted to the control circuit 3. Since the control circuit 3 maintains the oscillation of the inverter circuit 2, for example, in the case of a lighting device for two lamps, thinning out is performed when only one lamp is mounted and one lamp is removed. Lighting is possible, and the use of lighting equipment is expanded.
When three discharge lamps FL are connected in parallel as a load, in the case of a lighting device for three lamps, thinning-out lighting is performed in a case where only one lamp is installed and two lamps are removed. Needless to say, this is possible.

Embodiment 3 FIG. FIG. 3 is a circuit diagram of a discharge lamp lighting device according to Embodiment 3 of the present invention. 3, the same components as those in the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description of the duplicate components will be omitted. When compared with the third embodiment shown in FIG. 3 and the first embodiment shown in FIG. 1, the two differ in the arrangement of the load circuits connected between the output terminals of the inverter circuit 2. That is, in the first embodiment, the inverter circuit 2
Are connected in the order of ballast choke L → parallel circuit of discharge lamp FL and preheating capacitor C → DC blocking capacitor, whereas in Embodiment 3, ballast choke L → DC blocking capacitor → The discharge lamp FL and the preheating capacitor C2 are connected in the order of a parallel circuit.

The circuit operation of the third embodiment is the same as that of the first embodiment.
Since the high-frequency voltage is applied to both ends of the filament f1 with respect to the negative electrode side of the DC power supply 1, the filament f1
In order to compare the voltage and the threshold value S1 with the first comparator CP1, the first detection circuit 5 requires an insulating element such as a transformer or a photocoupler. On the other hand, in the third embodiment,
Since one end of the filament f1 of the discharge lamp FL is connected to the negative electrode side of the DC power supply 1, the first detection circuit 5 does not require an insulating element such as a transformer or a photocoupler, and directly detects the voltage of the filament f1. The first detection circuit 5 can be configured relatively easily.

Embodiment 4 FIG. 4 is a circuit diagram of a discharge lamp lighting device according to Embodiment 4 of the present invention. 4, the same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description of the duplicate components will be omitted. Embodiment 4
In the first embodiment, the first detection circuit 5 is specifically configured using electronic components in the first embodiment shown in FIG. In FIG. 4, a resistor R is connected between output terminals of the DC power supply circuit 4 (between the positive terminal of the DC power supply circuit 4 and the negative terminal of the DC power supply 1).
3, a series circuit of a diode D3 and a charging capacitor C4, and a series circuit of a diode D4 and a filament f1 between a connection point between the resistor R3 and the diode D3 and the negative electrode side of the DC power supply 1. Here, the resistor R3, the diodes D3 and D4, and the charging capacitor C4 correspond to the first detection circuit 5.

Next, the operation of the discharge lamp lighting device according to Embodiment 4 of the present invention will be described with reference to FIG. In the discharge lamp lighting device shown in FIG.
3 is selected to be sufficiently larger than the impedance of the filament f1 of the discharge lamp FL. that way,
When the filament fl is mounted, the impedance of the filament f1 is sufficiently smaller than the resistance R3, so that the power supply voltage of the DC power supply circuit 4 is almost applied to the resistance R3. Hardly applied.

However, when the filament f1 is open due to disconnection or the like, no current flows through the diode D4, so that the power supply voltage of the DC power supply circuit 4 is applied to the charging capacitor C4. Then, a threshold value S1 is provided between these two voltages, and the first comparator CP1 compares the voltage applied to the charging capacitor C4 with the threshold value S1. As a result, the voltage of the charging capacitor C4 becomes the threshold S
If it is 1 or less, it is detected that the filament f1 is in the mounted state, and if the voltage of the charging capacitor C4 is equal to or more than the threshold value S1, it is detected that the filament is not in the mounted state.
Subsequent control of the inverter circuit 2 is performed in the same manner as in FIG.

As described above, the first detection circuit 5 is provided between the positive side of the DC power supply circuit 4 and the negative side of the DC power supply 1 and has a resistance value detected by the first detection circuit. FL
And a series circuit of a first resistor R3, a first diode D3, and a charging capacitor C4, which is sufficiently larger than the impedance of the filament f1, a connection point between the first resistor R3 and the first diode D3, and the discharge lamp FL. And a second diode D4 connected between the first filament f1 and the first comparison circuit based on the charging voltage of the charging capacitor C4 supplied with the voltage from the DC power supply circuit 4. Since the detector CP1 detects whether or not the filament is in the non-attached state, the first detection circuit 5 that can use the DC power supply circuit 4 is configured, and the power supply is shared with the control circuit 3. Thus, the entire circuit can be configured at low cost.

Embodiment 5 FIG. 5 is a circuit diagram of a discharge lamp lighting device according to Embodiment 5 of the present invention. 5, the same components as those in the fourth embodiment shown in FIG. 4 are denoted by the same reference numerals, and the description of the duplicate components will be omitted. Embodiment 5
Switches the switch circuit 7 that turns on and off based on the OR output of the first or second comparator CP1 or CP2 in the fourth embodiment shown in FIG. And the control circuit 3.
This switch circuit 7 includes a first and a second comparator C
An OR output of P1 and CP2 is input, a transistor Q4 having an emitter connected to the negative electrode of the DC power supply 1, a collector of the transistor Q4 connected to the base, an emitter connected to the control circuit 3, and a collector connected to the DC power supply circuit 4. , And a resistor R4 for connecting the collector and the base of the transistor Q3 and supplying a base current to the transistor Q3.

Next, the operation of the discharge lamp lighting device according to Embodiment 5 of the present invention will be described with reference to FIG. In the discharge lamp lighting device shown in FIG. 5, as described with reference to FIG. 1, when the first comparator CP1 and the second comparator CP2 detect the non-attachment state of the filament, they output an H level.
Then, receiving this signal, the transistor Q4 of the switching circuit 7 is turned on. When the transistor Q4 is turned on, the base current cannot be supplied to the transistor Q3 via the resistor R4.
Turns off, and the switch circuit 7 turns off. Therefore, since control power is not supplied to the control circuit 3 by the switch circuit 7 turned off from the DC power supply circuit 4, the control circuit 3 does not operate and the inverter circuit 2 cannot operate. That is, the inverter circuit 2 stops oscillating. However, on the contrary, when the mounting state of the filament is detected, the first and second comparators CP1 and CP2 output the L level. At this time, the transistor Q4 is turned off, so that the transistor Q3 is turned on when a base current is supplied from the DC power supply circuit 4 via the resistor R4, the switch circuit 7 is turned on, and control power is supplied to the control circuit 3. , The control circuit 3 operates. That is,
Inverter circuit 2 can continue oscillating.

As described above, the DC power supply circuit 4 and the control circuit 3
And the switch circuit 7 provided between the first comparator C
Pl and the second comparator CP2 are turned off in response to a detection signal output when the filament has not been mounted,
Since no control power is supplied from the DC power supply circuit 4 to the control circuit 3, wasteful power consumption in the control circuit 3 when stopping oscillation of the inverter circuit 2 can be suppressed. Note that such a switch circuit 7 can also be provided in the first, second, third, and fourth embodiments.

Embodiment 6 FIG. FIG. 6 is a circuit diagram of a discharge lamp lighting device according to Embodiment 6 of the present invention. In the sixth embodiment, in the circuit of the fifth embodiment shown in FIG. 5, two load circuits of the inverter circuit 2 are connected in parallel, and the first detection circuit 5 (5a, 5
b), the second detection circuit 6 (6a, 6
b) the first comparator CP1 (CP1 for two circuits)
a, CP1b) and a portion corresponding to the second comparator CP2 (CP2a, CP2b for two circuits) are specifically configured using electronic components. In addition, the sixth embodiment includes a reset circuit 8 (8a, 8b for two circuits) that outputs a reset signal to the control circuit 3 when the discharge lamp is attached or detached.

Next, the operation of the discharge lamp lighting device according to the sixth embodiment of the present invention will be described with reference to FIG. In the discharge lamp lighting device shown in FIG. 6, the installation state of the filaments f1a, f2a and f1b, f2b is detected for each of the discharge lamps FLa, FLb. That is, for the discharge lamp FLa, the mounting state of the filament f1a is detected using the first detection circuit 5a, the zener diode DZ2a corresponding to the first comparator CP1, and the resistor R5a, and the second detection circuit 6a , The resistors R6a and R8a corresponding to the second comparator CP2, the Zener diode DZ3a,
The mounting state of the filament f2b is detected using the DZ4a, the transistor Q5a, and the capacitor C7a.

The method of detecting the mounting state of the filament f1a is as described in the description of FIG. 4, but the threshold value S1 of FIG.
In FIG. 6 corresponds to the Zener diode DZ2a. That is, when the voltage of the charging capacitor C4 is equal to or lower than the Zener voltage of the Zener diode DZ2a, it is detected that the filament f1a is in the mounted state, and the base current is not supplied to the transistor Q4a.
Since transistor 4a is turned off, transistor Q3 is turned on by the base current being supplied from DC power supply circuit 4 via resistor R4a and diode D9a, and control power is supplied to control circuit 3. On the other hand, when the voltage of the charging capacitor C4 is equal to or higher than the Zener voltage of the Zener diode DZ2a, it is detected that the filament f1a is not mounted, and the base current is supplied to the transistor Q4a and the transistor Q4a is supplied.
Since transistor 4a is turned on, transistor Q3 cannot supply a base current from DC power supply circuit 4 via resistor R4a and diode D9a.

The method of detecting the mounting state of the filament f2a is as described in the description of FIG. 1, but the threshold value S2 of FIG.
In FIG. 6 corresponds to the Zener diode DZ3a. That is, of the voltage divided by the capacitors C5a and C6a connected in series in the detection circuit 6a, the capacitor C6
If the voltage generated at a is equal to or higher than the Zener voltage of the Zener diode DZ3a, it is detected that the filament f2a is in the mounted state, the base current is supplied to the transistor Q5a, and the transistor Q5a is turned on. Since no charge is charged from the circuit 4 via the resistor R8a, the Zener diode DZ4a does not turn on. Accordingly, the base current is not supplied to the transistor Q4a, so that the transistor Q4a is turned off.
a, a base current is supplied via a diode D9a to turn on, and control power is supplied to the control circuit 3.

Conversely, when the voltage generated in the capacitor C6a is lower than the Zener voltage of the Zener diode DZ3a, it is detected that the filament f2a is not mounted, and the base current is not supplied to the transistor Q5a, so that the transistor Q5a is turned off. Accordingly, the capacitor C7a is charged from the DC power supply circuit 4 via the resistor R8a, and the Zener diode DZ4a is turned on. Then, the base current is supplied to transistor Q4a and transistor Q4a is turned on, so that transistor Q3 cannot supply the base current from DC power supply circuit 4 through resistor R4a and diode D9a. The reset circuit 8a includes a capacitor C8a, a differentiating circuit of the resistor R9a, and a diode D8a.
When the DC power supply circuit 4a changes from on to off,
From the resistor R4a, capacitor C8a, diode D8a
The differential pulse is input to the control circuit 3 via the control circuit 3.

Here, a case where the transistor Q4a changes from on to off will be described. As described above, in order for the transistor Q4a to be turned on, the condition is that at least one of the filaments f1a and f2a is not mounted.
Further, in order for the transistor Q4a to be turned off, it is required that both filaments f1a and f2a are in the mounted state. That is, when the filament is changed from the non-mounted state to the mounted state (strictly, when the filament f1a is changed from the non-mounted state to the mounted state), that is, when the discharge lamp is replaced, the transistor Q4a is turned off from on. The differential pulse is input from the DC power supply circuit 4 to the control circuit 3 via the resistor R4a, the capacitor C8a, and the diode D8a. If the control circuit 3 has a function of performing sequence control of preheating, starting, and lighting of the discharge lamp, when the differential pulse is detected, that is, when the discharge lamp is replaced, the differential pulse is used as a trigger. Sequence control of preheating, starting, and lighting can be performed.

The diode D7a and the resistor R7a are:
This component is provided to discharge the capacitor C7a by turning on the transistor Q5a when the filament f1a changes from the mounted state to the non-mounted state. The capacitor C7a is charged by the filament f
When the filament f1a changes from the non-mounted state to the mounted state unless the capacitor C7a is discharged, that is, when the discharge lamp is replaced, a differential pulse is input to the control circuit 3 when the capacitor C7a is not discharged. Can not. That is, when only the filament f1a changes from the non-mounted state to the mounted state (for example, when a lamp in which only the filament f1a is broken is replaced), a differential pulse cannot be input.

Although the operation of the circuit of FIG. 6 has been described so far on the discharge lamp FLa side, the operation on the discharge lamp FLb side is performed in exactly the same manner. However, transistors Q3, Q4a, Q4b, resistors R4a, R4b, and diodes D9a, D9b constitute a NAND circuit. Therefore, when both of the transistors Q4a and Q4b are on, that is, the filament f of the discharge lamp FLa
When at least one of the lamps 1a and f2a is not mounted and at least one of the filaments f1b and f2b of the discharge lamp FLb is not mounted, the transistor Q3 cannot supply a base current. Is not supplied, and the oscillation of the inverter circuit 2 stops.

As described above, the differential pulse is generated when the first comparator CP1 does not receive the detection signal of the filament non-attached state after receiving the detection signal of the filament non-attached state, and controls the differential pulse. A reset circuit 8 for outputting to the circuit 3 is provided. The control circuit 3 receives the differentiated pulse from the reset circuit and performs sequence control of preheating, starting, and lighting of the discharge lamp. The circuit 8 generates a differentiated pulse and outputs the differentiated pulse to the control circuit 3. The control circuit 3 can surely perform preheating, starting, and lighting of the replacement-mounted discharge lamp. Note that such a reset circuit 8 can also be provided in the first, second, third, fourth and fifth embodiments.

[0050]

According to the discharge lamp lighting device of the present invention, when only one discharge lamp is used as a load, at least one filament of the discharge lamp is in an open state.
Based on the voltage detected by the first or second detection circuit,
Alternatively, the second comparator detects that the filament is not attached, and the control circuit that has received the detection signal of the first or second comparator that the filament is not attached stops the oscillation of the inverter circuit. This has the effect of preventing the switching elements of the circuit from being destroyed due to heat generation and providing protection when no load is applied.

In the discharge lamp lighting device according to the second aspect of the present invention, when a plurality of discharge lamps are connected in parallel as a load, at least one filament of all the discharge lamps is in an open state, that is, when no discharge lamp is mounted. The detection signal of the filament non-attachment state of the first or second comparator in all the discharge lamps is input to the no-load determination circuit, and the no-load determination circuit outputs the filament non-attachment state detection signal to the control circuit. The control circuit that has received the detection signal of the filament non-attached state stops the oscillation of the inverter circuit, so that the switching element of the inverter circuit is prevented from being destroyed due to heat generation, so-called no-load protection is performed, and the filaments at both ends are attached. If there is at least one normal discharge lamp in the lit state, the no-load determination circuit controls the detection signal of the filament non-mounted state. Since the control circuit keeps the inverter circuit oscillating because it is not output to the lighting device, if the lighting fixture for multiple lamps is used, for example, only one discharge lamp is installed and the rest is removed It is possible to perform thinned-out lighting, and there is an effect that the usage of the lighting device is expanded.

In the discharge lamp lighting device according to the third aspect of the present invention, the first detection circuit connects one end of the filament of the discharge lamp for detecting the impedance to the negative electrode side of the DC power supply. There is no need for an insulating element such as a transformer or a photocoupler in the circuit, the voltage of the filament can be directly detected, and the first detection circuit can be configured relatively simply and inexpensively.

According to a fourth aspect of the present invention, in the discharge lamp lighting device, the first detection circuit is provided between the positive electrode side of the DC power supply circuit and the negative electrode side of the DC power supply, and has a resistance value of the first detection circuit. A first resistor, which is sufficiently larger than the impedance of the filament of the discharge lamp detected by the detection circuit, a series circuit of the first diode and the charging capacitor, and a connection point between the first resistor and the first diode; A second diode connected between the lamp and one of the filaments;
Since the first comparator detects whether or not the filament is in the non-attached state based on the charging voltage of the charging capacitor supplied with the voltage from the DC power supply circuit, the first comparator can use the DC power supply circuit. One detection circuit is configured, the power supply can be shared with the control circuit, and there is an effect that the entire circuit can be configured at low cost.

In the discharge lamp lighting device according to the fifth aspect of the present invention, the switch circuit provided between the DC power supply circuit and the control circuit may be configured such that the first comparator and the second comparator have no filament mounted. Since the supply of power from the DC power supply circuit to the control circuit is cut off in response to the detection signal output when the state is detected, it is possible to suppress unnecessary power consumption in the control circuit when stopping the oscillation of the inverter circuit. effective.

In the discharge lamp lighting device according to the present invention, when a plurality of discharge lamps are connected in parallel as a load, at least one of the filaments of all the discharge lamps is in an open state, that is, when the discharge lamp is not mounted. A non-load discrimination circuit that outputs a detection signal of the filament non-attached state to the control circuit when a filament non-attached state detection signal of the first or second comparator in all the discharge lamps is input;
A switch circuit provided between the DC power supply circuit and the control circuit is configured to cut off the supply of power from the DC power supply circuit to the control circuit when receiving a detection signal indicating that the filament is not attached from the no-load determination circuit. Therefore, there is an effect that unnecessary power consumption in the control circuit when stopping the oscillation of the inverter circuit can be suppressed.

In the discharge lamp lighting device according to the present invention, when the first comparator receives the detection signal of the filament non-attached state and stops receiving the detection signal of the filament non-attached state, the differential pulse And a reset circuit that outputs the differentiated pulse to the control circuit.The control circuit receives the differentiated pulse from the reset circuit, and performs sequence control of preheating, starting, and lighting of the discharge lamp. When the reset circuit is replaced, the reset circuit generates a differentiated pulse and outputs the differentiated pulse to the control circuit, and the control circuit can reliably perform preheating, starting, and lighting of the replaced and mounted discharge lamp. This has the effect.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to Embodiment 1 of the present invention.

FIG. 2 is a circuit diagram of a discharge lamp lighting device according to Embodiment 2 of the present invention.

FIG. 3 is a circuit diagram of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a discharge lamp lighting device according to Embodiment 4 of the present invention.

FIG. 5 is a circuit diagram of a discharge lamp lighting device according to Embodiment 5 of the present invention.

FIG. 6 is a circuit diagram of a discharge lamp lighting device according to Embodiment 6 of the present invention.

FIG. 7 is a circuit diagram of a conventional discharge lamp lighting device.

FIG. 8 is a circuit diagram of another conventional discharge lamp lighting device.

FIG. 9 is a configuration diagram for explaining a state of a discharge lamp.

FIG. 10 is a waveform chart for explaining the operation of the inverter circuit.

[Explanation of symbols]

1 DC power supply, 2 inverter circuit, 3 control circuit, 4
DC power supply circuit, 5 first detection circuit, 6 second detection circuit, CP1 first comparator, CP2 second comparator, F
L Discharge lamp.

Claims (7)

[Claims] A DC power supply; an inverter circuit connected to the DC power supply; a DC power supply circuit connected to the DC power supply; a load circuit including a discharge lamp connected between output terminals of the inverter circuit; A first detection circuit for detecting the impedance of one of the filaments, and an output terminal of the inverter circuit connected to the negative side of the DC power supply via the other filament of the discharge lamp to indirectly detect the discharge lamp voltage. A second detection circuit for detecting, a first comparator for outputting a detection signal of a filament non-attached state when an output level output from the first detection circuit is equal to or greater than a first threshold set in advance, A second comparator that outputs a detection signal of a filament non-attached state when an output level output from the second detection circuit is equal to or less than a preset second threshold value, and a DC power supply circuit Control to control the operation of the inverter circuit, and to stop the operation of the inverter circuit when receiving a detection signal of a filament non-attached state of at least one of the first comparator and the second comparator. A discharge lamp lighting device comprising a circuit. 2. A DC power supply, an inverter circuit connected to the DC power supply, a DC power supply circuit connected to the DC power supply, and a load circuit including a plurality of discharge lamps connected between output terminals of the inverter circuit. A plurality of first detection circuits for detecting the impedance of one filament of each discharge lamp; and a plurality of first detection circuits connected between the output terminal of the inverter circuit and the negative electrode side of the DC power supply via the other filament of each discharge lamp. A plurality of second detection circuits for indirectly detecting a lamp voltage, and a filament not attached when an output level corresponding to each of the first detection circuits is equal to or higher than a first threshold value set in advance. When the output level corresponding to each of the first comparators for outputting a state detection signal and each of the second detection circuits and the output level thereof is equal to or less than a second threshold value set in advance, the filament is not detected. A second comparator for outputting a detection signal of a wearing state; and a detection signal of a filament non-attachment state of at least one of the first comparator and the second comparator corresponding to each discharge lamp. And a no-load discrimination circuit that outputs the detection signal when received from the first or second comparator corresponding to the first and second comparators, and controls the operation of the inverter circuit driven by the DC power supply circuit. A control circuit for controlling operation of the inverter circuit to be stopped when a detection signal of a filament non-attached state is received. 3. The discharge lamp according to claim 1, wherein the first detection circuit connects one end of a filament of the discharge lamp for detecting impedance to a negative electrode side of the DC power supply. Lighting device. 4. The first detection circuit is provided between a positive side of the DC power supply circuit and a negative side of the DC power supply,
A series circuit of a first resistor, a first diode, and a charging capacitor, whose resistance value is sufficiently larger than the impedance of the filament of the discharge lamp detected by the first detection circuit;
A second diode connected between a connection point between the first resistor and the first diode and one filament of the discharge lamp, wherein the first diode and the second diode are connected to each other. The discharge lamp lighting device according to claim 3, wherein a diode is connected in a direction in which a direct current flows from a positive electrode side of the DC power supply circuit to a negative electrode side of the DC power supply. 5. A control circuit provided between the DC power supply circuit and the control circuit, wherein when a detection signal of a filament non-attached state of at least one of the first comparator and the second comparator is received. 5. The discharge lamp lighting device according to claim 1, further comprising a switch circuit for interrupting supply of power from a DC power supply circuit to the control circuit. 6. A power supply, provided between the DC power supply circuit and the control circuit, for supplying power from the DC power supply circuit to the control circuit when a detection signal of a filament non-attached state is received from the AND circuit. The discharge lamp lighting device according to claim 2, further comprising a switch circuit that shuts off the discharge lamp. 7. A differential pulse is generated when the first comparator receives the detection signal of the filament non-attached state from the detection signal of the filament non-attached state and generates the differentiated pulse. And a control circuit for performing sequence control of preheating, starting, and lighting of the discharge lamp in response to a differential pulse from the reset circuit. The discharge lamp lighting device according to any one of the above.