JP2002117991A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the noise applied to an electric apparatus such as a television set. SOLUTION: This discharge lamp lighting device comprises an FET 7 serving as a switch element in a DC power circuit 5 converting the AC of a commercial power supply 1 into DC and outputting it, an inverter 13 having a pair of FETs 14 and 15 connected to the output side of the DC power circuit as switch elements and converting the DC of the DC power circuit into a high-frequency voltage, and a series circuit of a discharge lamp 20 and a DC cut capacitor 22 connected to the output side of the inverter. An inductance 31, 33, or 35 having a nearly zero impedance at the drive frequency of the FET and having a high impedance in the VHF low-channel frequency band of the television set is connected in series between a gate of at least one of the FETs 7, 14, 15 and a gate drive circuit connected to the gate.

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 lighting a discharge lamp by applying a high-frequency voltage to the discharge lamp.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing the configuration of a conventional discharge lamp lighting device, FIG. 6 is a graph showing the relationship between frequency and noise of the discharge lamp lighting device, and FIG.
FIG. 4 is a waveform diagram of a gate applied voltage and a gate current of FIG. In the figure, 1 is a commercial power supply, 2 is a noise filter for cutting noise included in the commercial power supply 1, 3 is a capacitor provided on the output side of the noise filter 2, and 4 is a diode for full-wave rectification of the AC of the commercial power supply 1. The bridge 5 is a DC power supply circuit that smoothes the pulsating current that has been full-wave rectified by the diode bridge 4 and generates a boosted DC voltage.

The DC power supply circuit 5 includes a switching transformer 6 connected to the output side of the diode bridge 4 and a switching transformer 6 connected to the output side of the diode bridge 4.
And a first gate drive circuit 8 for driving the FET 7, an output side of the first gate drive circuit 8 and the FE
A resistor 9 provided between the gate of T7, a diode 11 connected to the drain of the FET 7, and a diode 1
1 and a smoothing capacitor 12 connected to the control circuit 1. The connection point between the source of the FET 7 and the resistor 10 is connected to the current detection terminal of the first gate drive circuit 8.

An inverter 13 converts a DC voltage of the DC power supply circuit 5 into a high-frequency voltage. This inverter 13
Is a pair of FETs 14 and 15 connected to the output side of the DC power supply circuit 5 and a pair of FETs 14 and 1
A second gate drive circuit 16 for alternately driving the gate 5 at a predetermined frequency, an output side of the second gate drive circuit 16 and an FET
It comprises a resistor 17 provided between the gate of FET 14 and a resistor 18 provided between the output side of the second gate drive circuit 16 and the gate of the FET 14. A pair of FE
The connection point between T14 and T15 is connected to the middle point of the second gate drive circuit 16. A discharge lamp lighting circuit, which is a series circuit of a discharge lamp 20 and a DC cut capacitor 22 in which an inductance 19 and a starting capacitor 21 are connected in parallel, is connected in parallel with the FET 15.

[0005] 25 is a resistor connected to the output side of the diode bridge 4, 26 is a Zener diode connected to the resistor 25, and 27 is an electrolytic capacitor connected to the resistor 25. The resistor 25, the Zener diode 26, and the electrolytic capacitor 27 smooth the pulsating current of the diode bridge 3 into a DC voltage, and input the DC voltage to the first and second gate drive circuits 8 and 16 as a drive power supply. belongs to.

The conventional discharge lamp lighting device is configured as described above. The alternating current of the commercial power supply 1 is full-wave rectified by the diode bridge 4 via the noise filter 2 and the capacitor 3, and is pulsated by the DC power supply circuit 5. And a DC voltage that is smoothed and boosted. The step-up of the DC voltage from the pulsating flow of the DC power supply circuit 5 stores energy for boosting by the switching transformer 6 and the first gate drive circuit 8 turns on and off the FET 7 for the energy. Is performed by smoothing the boosted AC with a diode 11 and a smoothing capacitor 12 to obtain a DC voltage. The DC voltage boosted by the DC power supply circuit 5 is applied to a pair of FETs 14 and 15 of the inverter 13. Then, the second gate drive circuit 16 alternately turns on and off the pair of FETs 14 and 15 at a predetermined frequency, converts the DC of the DC power supply circuit 5 into a high-frequency AC, and turns on the discharge lamp 20. I have.

[0007]

In the conventional discharge lamp lighting device as described above, the FET 7 of the DC power supply circuit 5 is driven by the first gate drive circuit 8. At this time, the drive voltage of the first gate drive circuit 8, that is, the gate applied voltage of the FET 7 is a rectangular wave as shown in FIG. 7A, the time t1 (for example, 10 μs) is the gate drive time, and the time t2 (for example, 10 μs) is the stop time. This driving voltage is FET7
When the voltage is applied to the gate of FIG. 7, a gate current flows as shown in FIG. The gate current is a current for charging and discharging the capacitance between the gate and the source of the FET 7, and the current has a waveform having a steep rise. The current having the steep rising waveform contains a large amount of high frequency components that affect the frequency band of the television as switching noise, and appears as noise on the television from the power supply line via the television antenna line. As shown by, around 100 MHZ, that is, V
There is a problem that noise appears on the screen of the low channel (1 to 3 channels) of the HF band, and the influence is large.
This problem also occurs when the FETs 14 and 15 of the inverter 13 having the same switching frequency as the DC power supply circuit 5 are driven by the second gate drive circuit 16.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a discharge lamp lighting device in which noise applied to electric equipment such as a television is suppressed.

[0009]

According to a first aspect of the present invention, there is provided a discharge lamp lighting apparatus comprising: an FE as a switch element provided in a DC power supply circuit for converting an alternating current of a commercial power supply into a direct current and outputting the direct current.
T, a first gate drive circuit that drives the FET at a predetermined drive frequency, and a smoothing circuit connected to the FET, and a pair of FETs and a pair of switch elements connected to the output side of the DC power supply circuit. A second gate drive circuit for driving the FET at a predetermined drive frequency; an inverter for converting DC of the DC power supply circuit to a high-frequency voltage; an inverter connected to an output side of the inverter; an inductance element and a starting capacitor connected in parallel; A discharge lamp lighting device comprising a discharge lamp and a series circuit of a DC cut capacitor.
The impedance becomes substantially zero at the driving frequency of the FET in series between at least any one of the gates and the gate driving circuit connected corresponding to the gate, and the impedance becomes high at a high frequency band much higher than the driving frequency. Are connected to each other.

In the discharge lamp lighting device according to a second aspect of the present invention, the high frequency band of the inductance element is a VHF low channel frequency band of a television.

In a discharge lamp lighting device according to a third aspect of the present invention, an element for absorbing a negative voltage based on an electromotive force generated in the inductance element is provided on an output side of the gate drive circuit.

In a discharge lamp lighting device according to a fourth aspect of the present invention, the element for absorbing a negative voltage based on the electromotive force generated in the inductance element is a capacitor or a diode.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a first embodiment of the present invention.
FIG. 3 is an impedance characteristic diagram with respect to the frequency of the inductance of the discharge lamp lighting device of the first embodiment, and FIG. 3 is a waveform diagram of the gate applied voltage of the FET of the discharge lamp lighting device of the first embodiment. In the figure, the same components as those of the conventional example are denoted by the same reference numerals, and the description of the duplicate components will be omitted. Reference numeral 31 denotes an inductance provided between the resistor 9 connected to the output side of the first gate drive circuit 8 in the DC power supply circuit 5 and the gate of the FET 7, and has a frequency of 50K as shown in FIG.
In HZ, the impedance is almost zero and 100 MHZ
It has the characteristic that the impedance becomes as high as about 2000Ω in the vicinity. 32 is a resistor 9 and an impedance 3
A capacitor having one end connected to the connection point 1 and the other end grounded.

Reference numeral 33 denotes an inductance provided between the resistor 17 connected to one output side of the second gate drive circuit 16 of the inverter 13 and the gate of the FET 14, and has the same characteristics as the inductance 31. Reference numeral 32 denotes a capacitor having one end connected to a connection point between the resistor 17 and the impedance 33 and the other end connected to a middle point of the second gate drive circuit 16. Reference numeral 35 denotes an inductance provided between the resistor 18 connected to the other output side of the second gate drive circuit 16 of the inverter 13 and the gate of the FET 15, and has the same characteristics as the inductance 31. A capacitor 36 has one end connected to the connection point between the resistor 18 and the impedance 35 and the other end grounded.

Next, the operation of the discharge lamp lighting device according to the first embodiment of the present invention will be described. FET of DC power supply circuit 5
7 is driven by a first gate drive circuit 8. At this time, the drive voltage of the first gate drive circuit 8, that is, the gate applied voltage of the FET 7 is a rectangular wave as shown in FIG. 7A, the time t1 (for example, 10 μs) is the gate drive time, and the time t2 (for example, 10 μs) is the stop time. When this drive voltage is applied to the gate of the FET 7, a gate current flows as shown in FIG. This gate current is a current for charging and discharging the capacitance between the gate and the source of the FET 7, and the current has a waveform having a steep rise. The current having the steep rising waveform contains a large amount of high-frequency components, for example, around 100 MHZ, which affect the frequency band of the television as switching noise.

Since the impedance of the inductance 31 connected to the gate of the FET 7 has almost zero at the switching frequency of the FET 7, it does not affect the switching characteristics. The impedance becomes high at 2000 Ω near 100 MHZ. As a result, high-frequency components around 100 MHZ are suppressed, and noise near 100 MHZ is suppressed as shown by the broken line in FIG. That is, the high impedance of the inductance 31 suppresses the high frequency component around 100 MHZ, so that the high frequency component around 100 MHZ from the power supply line via the TV antenna line allows the low-frequency (1 to 3 channel) screen of the VHF band of the television to be displayed. No longer appears as noise.

At this time, the electromotive force generated in the inductance 31 by the current flowing through the gate of the FET 7 is applied to the output terminal of the first gate drive circuit 8 and the output voltage of FIG.
A negative voltage is applied as shown in FIG. This negative voltage may destroy the output element inside the first gate drive circuit 8. However, since the negative voltage is absorbed by the capacitor 32 connected to the connection point between the resistor 9 and the inductance 31 connected to the output side of the first gate drive circuit 8, the voltage applied to the gate of the FET 7 is not shown. The waveform is as shown in FIG. Therefore, no negative voltage is applied to the output terminal of the gate control circuit 8, and there is no possibility that the output element inside the first gate drive circuit 8 will be destroyed.

FIG. 4 is a circuit diagram showing various modifications of the main part of the discharge lamp lighting device according to the first embodiment. FIG. 4a shows FIG.
A diode 42 is provided instead of the capacitor 32 connected to the connection point of the resistor 9 and the inductance 31 connected to the output side of the first gate drive circuit 8 shown in FIG. In this modified example, the same operation and effect are obtained by bypassing the reverse voltage by the switching operation while the junction capacitance of the diode 42 operates in the same manner as the capacitor 32. 4B differs from FIG. 1 in that the capacitor 32 is connected to the connection point between the output side of the first gate drive circuit 8 and the resistor 9. Even when the capacitor 32 is provided at the position shown in this modified example, the negative voltage is absorbed as in the first embodiment.

FIG. 4C is different from FIG.
2 is connected to a connection point between the output side of the first gate drive circuit 8 and the resistor 9. Even when the diode 42 is provided at the position shown in this modified example, the same function and effect can be obtained by bypassing the reverse voltage by the switching action while the junction capacity of the diode 42 has the same action as the capacitor 32. 4d is different from FIG. 1 in that the capacitor 32 is not provided. In this modified example, the electromotive force generated in the inductance 31 by the current flowing through the gate of the FET 7 is applied to the output terminal of the first gate drive circuit 8, and a negative voltage as shown in the waveform of FIG. This is because when the negative voltage is small, there is no possibility that the output element inside the first gate drive circuit 8 will be destroyed.

The above description is for the FET 7 as a switch element constituting the DC power supply circuit 5,
An FET 13 as a switch element constituting an inverter 13 having a switching frequency substantially the same as that of the DC power supply circuit 5,
Providing the inductances 33 and 35 and the capacitors 34 and 36 also provides the same operation and effect as in the DC power supply circuit 5. It is not always necessary to connect the inductances 31, 33, and 35 to the gates of the FETs 7, 14, and 15, which are all switch elements, and they may be appropriately selected depending on the performance of the switch elements and the performance of the gate drive circuit. Also, FETs 7, 14, 1
Inductors 31 and 3 connected in series to the gate of 5
Needless to say, the components 3 and 35 need not have the above-described characteristics, but need to have an effect of increasing impedance in a required high frequency band and suppressing noise in the frequency band.

[0021]

As described above, according to the present invention, an FET as a switch element included in a DC power supply circuit by converting AC from commercial power into DC and a first gate for driving the FET at a predetermined drive frequency. A driving circuit and a smoothing circuit connected to the FET, a pair of FETs as switching elements connected to the output side of the DC power supply circuit, and a second gate driving circuit for driving the pair of FETs at a predetermined driving frequency. Have
In a discharge lamp lighting device comprising an inverter for converting the DC of a DC power supply circuit to a high-frequency voltage, and a discharge lamp and a series circuit of a DC cut capacitor connected to an output side of the inverter and having an inductance element and a starting capacitor connected in parallel, Since an inductance element having high impedance in a high frequency band much higher than the driving frequency is connected between at least one of the gates of the FET and a gate driving circuit connected to the gate, FE
When T is driven by the gate drive circuit, when a drive voltage of the gate drive circuit is applied to the gate of the FET, a gate current having a waveform having a steep rise flows, and the gate current has a drive frequency of the FET. It contains a large amount of high-frequency components in a much higher high-frequency band, but the high-frequency components are suppressed by the high impedance of the inductance connected to the gate of the FET, and may appear as noise in external electrical equipment. This has the effect of disappearing. When the high frequency band of the inductance element has a high impedance in the VHF low channel frequency band of the television, the driving voltage of the gate driving circuit is FE.
When applied to the gate of T, a gate current having a waveform having a sharp rise flows, and the gate current is applied to the V
It contains a large amount of high-frequency components in the HF low-channel frequency band, but the high-frequency components are suppressed by the high impedance of the inductance connected to the gate of the FET. There is an effect that nearby high frequency components do not appear as noise on the screen of the television channel.

Further, according to the present invention, a capacitor or a diode is provided on the output side of the gate drive circuit as an element for absorbing a negative voltage based on an electromotive force generated in the inductance element. The negative voltage applied to the output terminal of the gate drive circuit due to the electromotive force generated is absorbed by a capacitor or a diode provided on the output side of the gate drive circuit, so that the negative voltage is applied to the output terminal of the gate drive circuit. This prevents the output element inside the gate drive circuit from being destroyed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is an impedance characteristic diagram with respect to a frequency of an inductance of the discharge lamp lighting device according to the first embodiment.

FIG. 3 is a waveform diagram of a gate applied voltage of an FET of the discharge lamp lighting device according to the first embodiment.

FIG. 4 is a circuit diagram showing various modified examples of a main part of the discharge lamp lighting device according to the first embodiment.

FIG. 5 is a circuit diagram showing a configuration of a conventional discharge lamp lighting device.

FIG. 6 is a graph showing a relationship between frequency and noise of the discharge lamp lighting device.

FIG. 7 is a waveform diagram of a gate applied voltage and a gate current of the FET of the discharge lamp lighting device.

[Explanation of symbols]

1 commercial power supply, 7 FET, 8 first gate drive circuit, 11 diode (smoothing circuit), 12 smoothing capacitor, 13 inverter, 14 FET, 15 FET,
16 second gate drive circuit, 19 inductance,
20 discharge lamp, 21 starting capacitor, 22 DC cut capacitor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Noriaki Okuda 2-14-40 Ofuna, Kamakura City, Kanagawa Prefecture Inside Mitsubishi Electric Lighting Co., Ltd. Inside Electric Lighting Co., Ltd. (72) Inventor Ryoji Minagawa 2-14-40, Ofuna, Kamakura City, Kanagawa Prefecture Mitsubishi Electric Lighting Co., Ltd. F-term (reference) 3K072 AA02 BA03 BA05 BB01 BC01 CA16 DB03 FA04 GA02 GB12 GC04

Claims (4)

[Claims] An FET as a switch element included in a DC power supply circuit that converts an AC of a commercial power supply into a DC and outputs the DC.
A first gate driving circuit for driving the FET at a predetermined driving frequency and a smoothing circuit connected to the FET, and a pair of FETs and a pair of FETs serving as switch elements connected to the output side of the DC power supply circuit, An inverter for converting a direct current of a DC power supply circuit to a high-frequency voltage, and a discharge lamp connected to an output side of the inverter and having an inductance element and a starting capacitor connected in parallel; And a series circuit of a direct current cut capacitor, wherein at least one of the gates of the FET and a gate drive circuit connected to the gate are connected in series with F
A discharge lamp lighting device comprising an inductance element having an impedance substantially equal to zero at a driving frequency of ET and having a high impedance in a high frequency band much higher than the driving frequency. 2. The discharge lamp lighting device according to claim 1, wherein the high frequency band of the inductance element is a VHF low channel frequency band of a television. 3. The discharge lamp lighting according to claim 1, wherein an element that absorbs a negative voltage based on an electromotive force generated in the inductance element is provided on an output side of the gate drive circuit. apparatus. 4. The discharge lamp lighting device according to claim 3, wherein the element that absorbs a negative voltage based on an electromotive force generated in the inductance element is a capacitor or a diode.