JP3513583B2 - Discharge lamp lighting device for backlight - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for a backlight . 2. Description of the Related Art A conventional discharge lamp lighting device of this type will be described with reference to FIG. The base of a transistor 3, which is the input side of a push-pull circuit, is connected to a DC power supply 1 via a starting resistor 2 in series. In this push-pull circuit, primary windings 6, 9, and 10 having an intermediate tap provided between collectors of a pair of transistors 3 and 4, each having an emitter grounded, are connected in parallel.
Are connected in parallel. The DC power supply 1 is connected to an intermediate tap via a coil 11 in series. Electromagnetic transformer 1
Electrodes of a discharge lamp 16 are electrically connected to both ends of the secondary windings 13, 14, 15 on the output side of 2, 7, and 8, respectively. The tertiary winding 17 on the output side of the electromagnetic transformer 12 includes a discharge lamp 16
Transistors 3 and 4 to feed back the voltage when
Is connected to the base side. A plurality of inverter circuits configured as described above are provided and used as a backlight lighting device. In the above circuit, when the DC power supply 1 is applied, a current flows through the coil 11 to the primary windings 6, 9, 1, and 2.
0, the resonance of the primary windings 6, 9 and 10 and the resonance capacitor 5 causes resonance, and the primary windings 6, 9, 10 and the tertiary winding 17, A voltage is induced by a turns ratio of 18. The voltage of the tertiary winding 17 is applied to the bases of the transistors 3 and 4, and the transistors 3 and 4
Conduction is alternately performed at the resonance frequency of the secondary winding 6. Secondary winding 1
Voltages boosted by the turns ratio of the primary windings 6, 9, 10 and the secondary windings 13, 14, 15 are induced in 3, 14, 15 and discharge starts inside the discharge lamp 16, The discharge lamp 16 lights up. Only the voltage is generated in the tertiary windings 18 that are not connected to the bases of the transistors 3 and 4. [0004] The discharge lamp lighting device of the prior art has a plurality of inverter circuits arranged in parallel to light a large number of discharge lamps, and component constants constituting each inverter circuit. Oscillates at different frequencies due to
There was a problem that flickering of the discharge lamp occurred. In order to solve the above problems, the present invention connects a tertiary winding, which is not connected to the base of a transistor of an electromagnetic transformer of an inverter circuit, to the base of a transistor of another inverter circuit. Connected in parallel with one of the tertiary windings,
An object is to eliminate flickering of a screen of a liquid crystal display device or the like. [0006] In order to achieve the above object, an invention according to claim 1 of the present invention provides a primary transformer.
Primary and tertiary windings with intermediate taps
A small number of secondary windings on the secondary side of the transformer
At least two or more starting electromagnetic transformers and their starting
Each of the transformers connected in parallel with the primary winding of the electromagnetic transformer
A push-pull circuit and a capacitor for resonance;
Primary winding with intermediate tap on primary winding of electromagnetic transformer
Are connected in parallel and have a secondary winding and a tertiary winding
Driven electromagnetic transformers and these driven electromagnetic transformers
Intermediate tap and intermediate tap of the starting electromagnetic transformer are common
Connected to one of the switching elements of the push-pull circuit.
DC power supply connected between the
Lance and connected to the secondary winding of each driven electromagnetic transformer
Discharge lamp group, and are arranged in parallel with each of the starting electromagnetic transformers.
Forms a closed circuit with the tertiary winding of the driven transformer connected to the
And the tertiary winding of the starting electromagnetic transformer is connected to the
The other switching element of the push-pull circuit and the DC power supply
Between the starting electromagnetic transformer and the driven electromagnetic transformer
Driving the discharge lamp with the connection between the
Features. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of a backlight discharge lamp lighting device according to an example of an embodiment of the present invention. In this figure, the base of a transistor 3 on the input side of a push-pull circuit is connected to a DC power supply 1 via a starting resistor 2 in series. In this push-pull circuit, primary windings 6, 9, 10 provided with an intermediate tap between collectors of a pair of transistors 3, 4 each having an emitter grounded are connected in parallel, and a resonance capacitor 5 is connected. Are connected in parallel. The DC power supply 1 is connected to the intermediate taps of the primary windings 6, 9, and 10 on the input side of the electromagnetic transformers 12, 7, and 8 via a coil 11 in series.
Current is caused to flow through 9 and 10. Electromagnetic transformer 1
The secondary windings 13, 14, 15 on the output side of 2, 7, 8 are 1
The number of windings is larger than that of the next windings 6, 9, and 10, so that the voltage is boosted. Both ends of the secondary windings 13, 14, 15 are directly connected to the electrodes of the discharge lamp 16 to supply current to the discharge lamp 16. Both ends of the secondary windings 13, 14, 15 may be connected to the electrodes of the discharge lamp 16 via current limiting capacitors. The tertiary winding 17 on the output side of the electromagnetic transformer 12 is
The third winding 17 is connected to the bases of the transistors 3 and 4.
The generated voltage is fed back to the base and applied. Primary windings 6, 9, 10, and secondary windings 13, 1 having intermediate taps of the inverter circuit configured as described above.
A plurality of electromagnetic transformers 12, 7, 8 provided with 4, 15, tertiary windings 17, 18, 19, transistors 3, 4
A circuit portion including the resonance capacitor 5 and the like is referred to as a block 20. Another inverter circuit having the same construction as the above-mentioned inverter circuit, having primary windings 21, 22, 23, secondary windings 24, 25, 26, and tertiary windings 27, 28 having intermediate taps. , 29 provided with a plurality of electromagnetic transformers 30,
A circuit portion including the transistors 31 and 32, the transistors 33 and 34 forming a pair, the resonance capacitor 35, and the like, and having the same configuration as the block 20 described above is referred to as a block 36, which is another inverter circuit having the same configuration as the inverter circuit. And a plurality of electromagnetic transformers 46, 47, 48 provided with primary windings 37, 38, 39 having secondary taps, secondary windings 40, 41, 42, and tertiary windings 43, 44, 45. A circuit portion having the same configuration as the above-described block 20 including the transistors 49 and 50 and the resonance capacitor 51 is referred to as a block 52. A plurality of electromagnetic transformers 30, 31, and 32 are arranged in parallel with the block 36 as in the above-described block 20, and a plurality of electromagnetic transformers 46, 47 and 48 are arranged in parallel with the block 52 as in the above-described block 20. Is provided. The tertiary winding 27 of the electromagnetic transformer 30 is connected to the bases of the transistors 33 and 34, and the tertiary winding 43 of the electromagnetic transformer 46 is connected to the bases of the transistors 49 and 50 to connect the tertiary windings 27 and 43. Is applied to the bases of the transistors 33, 34, 49 and 50. Tertiary windings 19, 2 of electromagnetic transformers 8, 32, 48
9, 45 are connected in parallel. The tertiary windings 18, 28, 44 of the electromagnetic transformers 7, 31, 47 are not connected to any, but are parallel to the tertiary windings 19, 29, 45, 18, 28, 44 not connected to the base. May be connected. As described above, by repeatedly connecting the tertiary winding not connected to the base of the transistor to the tertiary winding not connected to the base of the transistor of another inverter circuit, Synchronize the frequency of all blocks. In the above configuration, the DC power supplies 1, 53, 5
When 4 is applied, current flows through each circuit. Specifically, when the DC power supplies 1, 53, 54 are applied, the coil 1
Blocks 1, 36, 52 1 through 1, 55, 56
Next windings 6, 9, 10, 21, 22, 23, 37, 38,
A current starts to flow in 39, and the reactance of the primary windings 6, 9, and 10 and the resonance capacitor 5 in the block 20, and the primary windings 21, 22, and 23 in the block 36.
In the block 52, the reactance of the primary windings 37, 38, and 39 and the resonance capacitor 51 resonate individually. Then, the electromagnetic transformers 12, 7, 8, 30, 31, 32, 46, 47,
48 tertiary windings 17, 18, 19, 27, 28, 29,
Primary windings 6, 9, 10, 2 between terminals 43, 44, 45
Number of turns of 1, 22, 23, 37, 38, 39 and tertiary winding 1
7, 18, 19, 27, 28, 29, 43, 44, 45
The voltage is induced by the turns ratio of the number of turns. Tertiary winding 17,
27, 43 are respectively connected to the transistors 3, 4, 33,
34, 49, and 50 to the base of transistor 3,
4, 33, 34, 49, 50 are connected to the primary windings 6, 21,
Conducting alternately at a resonance frequency of 37, the collector current becomes 1
Next windings 6, 9, 10, 21, 22, 23, 37, 38,
Flow through 39. Secondary windings 13, 14, 15, 2
4, 25, 26, 40, 41, 42, primary windings 6, 9, 10, 21, 22, 23, 37, 38, 3
9 and secondary windings 13, 14, 15, 24, 25, 26, 4
A high voltage boosted by the turns ratio of 0, 41, 42 is induced, and the secondary windings 13, 14, 15, 24, 25, 26, 4,
0, 41, and 42 have primary windings 6, 9, 10, 21, 2
The current flows in the same direction as the current flows of 2, 23, 37, 38, and 39. That is, the secondary windings 13, 14,
When a voltage is applied to the bases of the transistors 3, 33, and 49, a current flows in the right direction to 15, 24, 25, 26, 40, 41, and 42, and a voltage is applied to the bases of the transistors 4, 34, and 50. In this case, a current flows to the left, and the current is supplied alternately to the electrodes of the discharge lamp 16. Discharge starts inside the discharge lamp 16, and the discharge lamp 16 is turned on. Since the tertiary windings 19, 29, and 45 are connected in parallel, they operate to synchronize the resonance frequencies of the respective circuit blocks 20, 36, and 52. The primary windings 9, 22, 38 are connected to the tertiary windings 18, 28, 44 which are not connected to any of them.
Only the voltage induced by is generated. One of the tertiary windings not connected to the base of the transistor of the electromagnetic transformer paralleled in this way is connected in parallel with the tertiary winding not connected to the base of the transistor of another inverter circuit. , A high-voltage waveform whose frequency and phase are synchronized from both ends of the secondary winding of the electromagnetic transformer is generated, and as a result, flickering of the discharge lamp is prevented. The embodiment shown in FIG. 2 will be described. For the sake of simplicity, parts having the same functions as those in FIG. 1 will be described using the same reference numerals. In the present embodiment, 3
One of the terminals of the next windings 19, 29, 45 is connected in parallel,
The other terminal is grounded. If one of the terminals is grounded, the circuit is simplified and the manufacture of the substrate is facilitated.
The other configuration is completely the same as that of the embodiment shown in FIG. The embodiment shown in FIG. 3 will be described. In the present embodiment, the other terminals of the tertiary windings 19, 29, 45 are grounded via switches 57, 58, 59. The other configuration is exactly the same as the above-described embodiment of FIG. As described above, when the switches 57, 58, and 59 are provided, a desired inverter circuit among a plurality of inverter circuits can be opened, and the light amount of only a desired portion can be reduced. According to the present invention, one of the tertiary windings not connected to the base of a transistor of an electromagnetic transformer in parallel with each inverter circuit is connected to the base of a transistor of another inverter circuit. , So that the resonance frequency of each inverter circuit is synchronized so that the frequency and phase can be shifted from both ends of the secondary winding of each electromagnetic transformer. Has the effect of generating a synchronized high-voltage waveform, thereby preventing flickering of the discharge lamp. Further, by grounding one of the terminals of the tertiary winding connected to each other between different circuits, the circuit is simplified, and there is an effect that the manufacture of the substrate is facilitated. Further, when grounded via a switch, there is an effect that a desired inverter circuit is synchronized when the circuit is closed, and that when the circuit is open, the independent DUTY dimming and the turning off of the discharge lamp can be performed by the respective inverter circuits.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing a configuration of an example of an embodiment of the present invention. FIG. 2 is a circuit diagram showing a configuration of an example of an embodiment of the present invention. FIG. 3 is a circuit diagram showing a configuration of an example of an embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration of a conventional example. [Description of Signs] 1, 53, 54 DC power supplies 3, 4, 33, 34, 49, 50 Transistors 5, 35, 51 Capacitors 6, 9, 10, 21, 22, 23, 37, 38, 39
Primary windings 7, 8, 12, 30, 31, 32, 46, 47, 48
Electromagnetic transformers 13, 14, 15, 24, 25, 26, 40, 41, 4
2 Secondary winding 16 Discharge lamps 17, 18, 19, 27, 28, 29, 43, 44, 4
5 Tertiary winding 57, 58, 59 Switch

Claims (1)

(57) [Claims] [Claim 1] An intermediate tap provided on a primary side of a transformer is provided.
Primary and tertiary windings and secondary side of transformer
At least two or more starting electrodes having a secondary winding provided in
Magnetic transformers and each of these starting electromagnetic transformers
Push-pull circuit connected in parallel with primary winding and resonance
Capacitor and the primary winding of each starting electromagnetic transformer
A primary winding having an intermediate tap is connected in parallel, and
A driven electromagnetic transformer having a secondary winding and a tertiary winding;
The intermediate tap of these driven electromagnetic transformers and the starting power
Connect the middle tap of the magnetic transformer in common and
Connected between one switching element of the
Power supply, each of the starting electromagnetic transformers and each driven electromagnetic
Tertiary of the driven transformer connected to the secondary winding of the transformer
Forming a closed circuit with windings and the starting electromagnetic transformer;
Is connected to the other switch of the push-pull circuit.
Starting electromagnetic transformer connected between the switching element and DC power supply
And the discharge between the driven electromagnetic transformers in a coupled state.
Discharge lamp spot for backlight characterized by driving a lamp
Lighting device.