JP2001160496A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device with comparatively simple circuitry and easy and inexpensive manufacturing process realizing a compact size, which can avoid an adverse effect due to dispersion of electric characteristics of field effect transistors each switching alternately without fail. SOLUTION: A resonant circuit 11 including capacitor 8, a ballast choke 9, and a discharge lamp 10 is connected between output ends of half-bridge type inverter circuit, where a pair of field effect transistors 12, 13 of the inverter circuit 5 shall be N-channel and secondary coils 18, 19 of the ballast choke 9 as well as parallel resonant circuits 26, 27 including inductors 22, 23 and capacitors 24, 25 are set up in a gate-driving circuit 16, 17 of the field effect transistors 12, 13.

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 fluorescent lamp and other discharge lamps by driving an inverter.

[0002]

2. Description of the Related Art As a discharge lamp lighting device provided with a half-bridge type inverter circuit, there has heretofore been known a Japanese Patent Publication No. 6-7952.
No. 0 and Japanese Patent Application Laid-Open No. 10-327584.

That is, in the discharge lamp lighting device described in Japanese Patent Publication No. 6-79520, a resonance circuit including a capacitor, a ballast choke and a discharge lamp is connected between the output terminals of a half-bridge type inverter circuit. The discharge current is fed back by a current transformer to alternately switch a pair of transistors of the inverter circuit, thereby lighting the discharge lamp.

The discharge lamp lighting device described in Japanese Patent Application Laid-Open No. 10-327584 uses a P-channel type field effect transistor and an N-channel type field effect transistor for a pair of switching elements of an inverter circuit.
In the gate drive circuit of each of these field effect transistors,
A secondary coil of a ballast choke and a series resonance circuit including a resistor, a capacitor, and an inductor are provided, and the discharge lamp is turned on by switching each field effect transistor alternately.

[0005]

The former conventional discharge lamp lighting device has a drawback that the entire device is structurally large because it has a circuit configuration using a current transformer.

On the other hand, the latter discharge lamp lighting device does not require the use of a current transformer, and thus has the advantage of being structurally miniaturized.

However, in this discharge lamp lighting device, since the inverter circuit is formed by using the P-channel field effect transistor and the N-channel field effect transistor, the cost of the circuit components increases, and
There is a disadvantage that it is difficult to maintain a balance between the switching operations of the pair of switching elements.

That is, the P-channel field-effect transistor generally has a higher cost than the N-channel field-effect transistor, which causes a problem that the manufacturing cost is increased.

[0009] The P-channel field-effect transistor and the N-channel field-effect transistor both have greatly different electrical characteristics. Therefore, when a P-channel field-effect transistor and an N-channel field-effect transistor are alternately switched by a single gate drive circuit, both transistors have the same characteristics as those using the same type of field-effect transistor. There is a problem that it is difficult to perform switching in an anti-symmetric manner, and that the influence of variations in individual electric characteristics of each field-effect transistor becomes large.

Further, in the latter discharge lamp lighting device, since the series resonance circuit is provided in the gate drive circuit, the current value of the inductor becomes larger than that using the parallel resonance circuit, and the inductor becomes larger. There are drawbacks.

In view of the conventional problems, the present invention can be manufactured easily and inexpensively with a relatively simple circuit configuration, can reduce the size of the entire device, and can reliably switch each field effect transistor alternately. It is another object of the present invention to provide a discharge lamp lighting device capable of preventing the influence of variations in individual electrical characteristics of a field effect transistor and stably lighting a discharge lamp.

[0012]

According to the present invention, a capacitor 8 is connected between the output terminals of a half-bridge type inverter circuit 5.
A ballast choke 9 is connected to a resonance circuit 11 including a discharge lamp 10, and a pair of field effect transistors 12,
In the discharge lamp lighting device in which the discharge lamp 10 is turned on by alternately switching the 13, the pair of field effect transistors 12 and 13 are N-channels, and the gate drive circuits 16 and 17
In addition, the secondary coils 18, 19 of the ballast choke 9 and the parallel resonance circuit 26, including the inductors 22, 23 and the capacitors 24, 25,
27.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. In FIG. 1, 1 is a commercial AC power supply,
Reference numeral 2 denotes a full-wave rectifier circuit, and a smoothing capacitor 4, a half-bridge type inverter circuit 5, and an inverter starting circuit 6 are connected to the output side of the full-wave rectifier circuit 2 via a resistor 3. And, between the output terminals of the inverter circuit 5, a capacitor 7 for DC cutoff, a capacitor 8 for starting
The resonance circuit 11 including the primary coil 9a of the ballast choke 9 and the discharge lamp 10 is connected. Note that a fluorescent lamp or the like is used as the discharge lamp 10.

The inverter circuit 5 includes a series circuit of a first field effect transistor 12 and a second field effect transistor 13 as a pair of switching elements, and this series circuit is connected to the capacitor 4 in parallel. A MOS N-channel is used for each of the field effect transistors 12 and 13.

The drain of the second field effect transistor 13
The filaments 14 and 15 of the discharge lamp 10 are connected between the sources via the capacitor 7 and the primary coil 9a of the ballast choke 9, and the capacitor 8 is connected between the filaments 14 and 15.

Each of the field effect transistors 12 and 13 is provided with a gate drive circuit 16 and 17 respectively. Each gate drive circuit 16, 17 is a secondary coil of ballast choke 9.
18 and 19 and parallel resonance circuits 26 and 27 including resistors 20 and 21, inductors 22 and 23 and capacitors 24 and 25. The secondary coils 18, 19 and the resistors 20, 21 of the ballast choke 9 are
The resistors 20 and 21 are connected in series between the gate and the source of the field-effect transistors 12 and 13 so that the resistors 20 and 21 are on the gate side.
The inductors 22 and 23 and the capacitors 24 and 25 are connected in parallel to this.

In this discharge lamp lighting device, the resonance frequency f ₀ of the parallel resonance circuits 26 and 27, the lighting frequency f _T of the discharge lamp 10 and the resonance frequency f _M of the resonance circuit 11 on the discharge lamp 10 side are shown in FIG. As shown in the figure, the capacitors 8 and the ballast choke 9 of the resonance circuit 11 including the discharge lamp 10 and the capacitors 24 and 27 of the parallel resonance circuits 26 and 27 satisfy the condition of the resonance frequency f ₀ <lighting frequency f _T <resonance frequency f _M. 25 and constants of the inductors 22 and 23 are set respectively.

The inverter starting circuit 6 includes a resistor 28 and a capacitor 29 connected in series.
A switching element 30 such as a diac is connected between a connection point of the second field effect transistor 12 and a gate of the first field effect transistor 12, and a diode 32 is connected between the connection point and the source side of the second field effect transistor 13. A resistor 33 and a capacitor 34 are connected in parallel with the second field effect transistor 13, and one of the pair of field effect transistors 12, 13 of the inverter circuit 5, that is, the first field effect transistor
12 is switched first.

When the power is turned on when the discharge lamp 10 is turned on, the DC power rectified by the full-wave rectifier circuit 2 is converted into a capacitor.
4 and the capacitor 29 is charged via the resistor 28. When the charging voltage of the capacitor 29 reaches the breakover voltage of the switching element 30, a gate voltage is applied to the first field-effect transistor 12, and the first field-effect transistor 12 is turned on.

Therefore, the condenser 7, the filament 14 of the discharge lamp 10, the condenser 8, the filament 15 of the discharge lamp 10,
A current flows through the primary coil 9a of the ballast choke 9 and the first field effect transistor 12. As a result, the capacitor 8 is charged, and a voltage is induced in the secondary coil 18 of the ballast choke 9, and the voltage causes the first field-effect transistor 12 to be completely turned on. Also capacitor 8
Is charged, the charging voltage is applied to the discharge lamp 10.

Thereafter, as the capacitor 8 charges, the resonance current between the capacitor 8 and the ballast choke 9 gradually decreases, and the voltage of the secondary coil 18 of the choke coil 9 decreases.
Gate-source voltage V of first field effect transistor 12
_{Since GS} decreases, the first field-effect transistor 12 turns off.

On the other hand, the secondary coil 19 of the ballast choke 9
And the second field effect transistor 13 is turned on by the voltage after the first field effect transistor 12 is turned off. Therefore, the charge of capacitor 8
, Second field effect transistor 13, ballast choke 9
To discharge through.

Hereinafter, the first operation is performed by repeating the same operation.
Field effect transistor 12 and second field effect transistor 13
The switching operation of turning on and off alternately is repeated, and the inverter circuit 5 maintains the oscillation state. And
When the voltage of the capacitor 8 rises due to resonance between the capacitor 8 of the resonance circuit 11 and the ballast choke 9 and the voltage becomes the lighting voltage of the discharge lamp 10, the filament 1 of the discharge lamp 10
A discharge occurs between 4, 15 and the discharge lamp 10 is turned on.

This discharge lamp lighting device has the following advantages. That is, two N-channel field effect transistors 12 and 13 are used as switching elements of the inverter circuit 5, and each of the field effect transistors 12 and 13 is of the same type.
Since it is a channel, the cost of the pair of field effect transistors 12 and 13 can be reduced as compared with the case where a P-channel field effect transistor is used.

Each of the field effect transistors 12 and 13 is of the same type, and uses N-channel field effect transistors 12 and 13 having smaller on-resistance and input capacitance among electrical characteristics than the P-channel. The secondary coils 18 and 19 of the ballast choke 9 are incorporated in the gate drive circuits 16 and 17 of the field effect transistors 12 and 13, respectively, so that the field effect transistors 12 and 13 are alternately switched. Individual field-effect transistors compared to the case where
2,13 Variations in the electrical characteristics of each other can be reduced, and each field effect transistor 12,13 can be switched alternately in a well-balanced manner, so that variations in the individual electrical characteristics of the field effect transistors 12,13 can be achieved. Can be prevented.

The gate drive circuits 16 and 17 of the field effect transistors 12 and 13 are connected to the secondary coils 18 and 19 of the ballast choke 9.
, Resistors 20, 21 and capacitors 24, 25,
Gate-source voltage V of field effect transistors 12 and 13
_GS is delayed with respect to the induced voltage of the secondary coils 18 and 19 due to the time constant of the resistors 20 and 21 and the capacitors 24 and 25. Therefore, if the power supply voltage rises, the off-state of each of the field-effect transistors 12 and 13 is delayed and the on-period becomes longer, so that the oscillation frequency of the inverter circuit 5 decreases. Then, the lighting voltage of the discharge lamp 10 decreases, and not only cannot the stable lighting of the discharge lamp 10 be maintained, but also the field-effect transistors 12, 13 may be damaged due to an excessive decrease in the oscillation frequency.

However, in addition to the secondary coils 18 and 19 of the ballast choke 9, resistors 20 and 21, capacitors 24 and 25, and inductors 22 and 23 are provided in the gate drive circuits 16 and 17 of each of the field effect transistors 12 and 13. And the parallel resonance circuits 26, 2
7 and the resonance frequency f ₀ of the parallel resonance circuits 26 and 27.
Operating frequency f _T and the discharge lamp 10 side of the resonant circuit 11 of the discharge lamp 10 and
Of the resonance frequency f _M is equal to the resonance frequency f ₀ <as shown in FIG.
The capacitors 8 and the ballast choke 9 of the resonance circuit 11 including the discharge lamp 10 and the capacitors 24 and 2 of the parallel resonance circuits 26 and 27 satisfy the condition of lighting frequency f _T <resonance frequency f _M.
5 and the constants of the inductors 22 and 23 are set respectively. Therefore, when the oscillation frequency of the inverter circuit 5 decreases due to an increase in the power supply voltage or the like, the phase control is performed by the parallel resonance circuits 26 and 27, and FIG. it can be moved to the solid line the phase of the gate-source voltage V _GS of the field effect transistors 12 and 13 from the dotted line as shown in.

As a result, the respective field effect transistors 12 and 13 are turned off quickly, so that the oscillation frequency of the inverter circuit 5 can be prevented from lowering, the stable lighting of the discharge lamp 10 can be maintained, and the respective field effect transistors 12 and 13 can be maintained. 13 can be prevented from being damaged. That is, this phase control causes the gate-source voltage V _GS of each of the field-effect transistors 12 and 13 to be increased.
Can be controlled to a phase suitable for turning on the discharge lamp 10, and the discharge lamp 10 can be stably turned on. Incidentally, V _DS in FIG. 3 is a drain-source voltage of the field effect transistors 12 and 13.

The gate drive circuits 16 and 17 of the field effect transistors 12 and 13 have resistors 20 and 21 and capacitors 24 and 25, respectively.
In addition, since parallel resonance circuits 26 and 27 including inductors 22 and 23 are provided, the resonance current is smaller than in the case of a series resonance circuit, and the current in inductors 22 and 23 can be reduced. 22,23 can be downsized.

Although the embodiment of the present invention has been described in detail, the present invention is not limited to this embodiment.
For example, the gate drive circuits 16 and 17 of the field effect transistors 12 and 13 are connected to the secondary coils 18 and 19 of the ballast choke 9.
It is sufficient that the circuit includes the capacitors 24 and 25 and the parallel resonance circuits 26 and 27 of the inductors 22 and 23. The specific circuit configuration can be variously changed. Also, various circuit configurations can be employed for the inverter start-up circuit 6.

[0031]

According to the present invention, the pair of field effect transistors 12 and 13 have N channels, and the gate driving circuits 16 and 17 of the field effect transistors 12 and 13 have the secondary coils 18 and 19 of the ballast choke 9 connected thereto. And the parallel resonance circuits 26 and 27 including the inductors 22 and 23 and the capacitors 24 and 25 can be manufactured easily and inexpensively with a relatively simple circuit configuration, and the entire device can be reduced in size and the electric field effect can be reduced. The effects of variations in the individual electrical characteristics of the transistors 12 and 13 can be prevented, and the discharge lamp 10 can be stably turned on.

The resonance frequency f ₀ of the parallel resonance circuits 26, 27
Operating frequency f _T and the discharge lamp 10 side of the resonant circuit 11 of the discharge lamp 10 and
The resonance frequency f _M is the resonance frequency f ₀ of the <lighting frequency f _T <
Since the constants of the capacitors 24 and 25 and the inductors 22 and 23 of the parallel resonance circuits 26 and 27 are set so as to be the resonance frequency f _M , a decrease in the oscillation frequency of the inverter circuit 5 due to an increase in the power supply voltage or the like is prevented. At the same time, it is possible to prevent the field effect transistors 12 and 13 from being damaged at that time.

Further, a resonance circuit 11 including a capacitor 8, a ballast choke 9 and a discharge lamp 10 is connected in parallel to one of the pair of field effect transistors 12 and 13, and the other is connected when the inverter circuit 5 is started. Since the inverter starting circuit 6 for switching the field effect transistor 12 first is provided, the starting of the inverter circuit 5 can be easily and smoothly performed.

Further, each of the gate drive circuits 16 and 17 has a resistor 2 between the gate and the source of each of the field effect transistors 12 and 13.
The ballast choke 9 includes secondary coils 18, 19 and resistors 20, 21 connected in series such that 0, 21 is on the gate side, and capacitors connected in parallel to these.
24, 25 and inductors 22, 23, each switching element 30 has an N-channel field effect transistor.
Despite using 12,13, gate drive circuit 1
The circuit configuration of 6,17 can be simplified.

[Brief description of the drawings]

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

FIG. 2 is a frequency characteristic diagram showing one embodiment of the present invention.

FIG. 3 is a voltage waveform diagram showing one embodiment of the present invention.

[Explanation of symbols]

 5 Inverter circuit 6 Inverter starting circuit 8 Capacitor 9 Ballast choke 10 Discharge lamp 11 Resonance circuit 12 First field effect transistor 13 Second field effect transistor 16,17 Gate drive circuit 18,19 Secondary coil 20,21 Resistance 22,23 Inductor 24,25 Capacitor 26,27 Parallel resonance circuit

Claims (4)

[Claims] A half-bridge type inverter circuit (5)
Between the output terminals of the capacitor (8) and ballast choke (9)
In addition, a resonance circuit (11) including a discharge lamp (10) is connected, and the discharge lamp (10) is turned on by alternately switching a pair of field effect transistors (12) and (13) of an inverter circuit (5). In the discharge lamp lighting device described above, the pair of field effect transistors (12) and (13) are N-channels, and the gate drive circuits (16) and (17) of each of the field effect transistors (12) and (13)
The secondary coils (18) and (19) of the ballast choke (9) and the parallel resonant circuits (26) and (27) including the inductors (22) and (23) and the capacitors (24) and (25). Discharge lamp lighting device characterized by the above-mentioned. 2. The resonance frequency f _{0 of the} parallel resonance circuits (26) and (27).
And the lighting frequency f _T of the discharge lamp (10) and the resonance frequency f _M of the resonance circuit (11) on the side of the discharge lamp (10) are set in parallel so that the resonance frequency f ₀ <the lighting frequency f _T <the resonance frequency f _M. Resonant circuit (26)
The discharge lamp lighting device according to claim 1, wherein constants of the capacitors (24) and (25) and the inductors (22) and (23) of (27) are set. 3. A capacitor (8) is connected to one of the pair of field effect transistors (12) and (13).
Resonant circuit including ballast choke (9), discharge lamp (10)
3. An inverter starting circuit (6), wherein said inverter starting circuit (6) is connected in parallel and said other field effect transistor (12) is switched first when said inverter circuit (5) is started. The discharge lamp lighting device as described in the above. 4. Each of the gate drive circuits (16) and (17) includes a resistor (2) between the gate and the source of each of the field effect transistors (12) and (13).
0) and (21) are connected in series such that the ballast choke (9) secondary coils (18) and (19) and the resistors (20) and (21) are connected in series with the gate side. The discharge lamp lighting device according to any one of claims 1 to 3, further comprising capacitors (24) and (25) and inductors (22) and (23) connected to the discharge lamp.