JPH1197193A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which secures a sufficient preheating current and ensures a long lifetime of the discharge lamp. SOLUTION: A series circuitry of switching elements Q1 and Q2 is connected across a capacitor C1 for filtering, while a parallel circuit of a load circuit 1 and a charging circuit 2 is connected between the DC output end on the low potential side of a rectifier DB and the connecting point of the two switching elements Q1 and Q2. The ground potential of a filament f1 on the rectifier DB side of the discharge lamp La takes a value sunk by an amount corresponding to the voltage generated at the two ends of the inductor L2 from the case where the inductor 12 is connected with the rectifier DB side to the discharge lamp La. The ground potential of the filament f2 of the discharge lamp La on the side with the switching elements Q1 and Q2 takes a value sunk by an amount corresponding to the voltage generated at the two ends of the inductor L2, viewed from the connecting point of the two switching elements Q1 and Q2.

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 converting a DC voltage obtained by rectifying and smoothing an AC power into a high frequency and supplying the high frequency to a discharge lamp.

[0002]

2. Description of the Related Art FIG.
Some have a circuit configuration as shown in FIG. This discharge lamp lighting device includes a rectifier DB for full-wave rectification of an AC power supply Vs.
, A small-capacity capacitor C ₂ connected between the DC output terminals of the rectifier DB, a smoothing capacitor C ₁ having one end connected to the low potential side of the DC output terminal of the rectifier DB, and both ends of the capacitor C ₁ a series circuit of switching elements Q _1, Q ₂ which is turned on and off to the connected alternating between a switching element Q _1, Q ₂ diode D _1, which are respectively connected in antiparallel, D _2, switching element Q ₁ , one end to the connection point Q ₂ 'is connected, it is composed of a parallel circuit of the rectifier DB and the load circuit and the other end is connected to a connection point of the capacitor C ₂ 1 and the inductor L _1, the switching element Q ₁ , Q ₂ is turned on and off alternately by a control circuit (not shown).

[0003] Further, the load circuit 1 includes a rectifier DB and the inductor L ₂ having one end to a connection point between the capacitor C ₂ is connected
If, on the other end of the inductor L ₂ together with the power supply side terminal of one filament is connected, the switching elements Q _1,
To the connection point Q ₂ 'made of, for example, a fluorescent lamp power supply side terminal is connected to the other filament and the discharge lamp La, the discharge lamp La
Composed of capacitors connected C ₃ Metropolitan between non-power side terminals of both filaments.

Here, with reference to FIGS. 8 (a) to 8 (e),
Switching element Q₁, Q_TwoExplain the on / off operation of
You. As shown in FIG. 8A, the switching element Q₁But
When turned on, the capacitor C ₁From switching element Q₁
→ Inductor L₁And load circuit 1 → capacitor C_Two→ Ko
Capacitor C₁The current flows through the path. At this time,
Sa C_TwoVoltage V _C2Is the inductor L_TwoDue to resonance with
Increase. Switching element Q₁Is turned off, the figure
As shown in FIG.₁And load circuit 1
From the parallel circuit of capacitor C_Two→ Diode D_Two→ Inn
Dacta L₁Current flows in the parallel circuit path of the load circuit 1
And the capacitor C_TwoVoltage V_C2Increases further.

[0005] Next, when the switching element Q ₂ is turned on, as shown in FIG. 8 (c), the resonance of the inductor L _1, L ₂ and capacitor C _2, C _3, the inductor L ₁ and capacitor C ₂ A resonance current flows through the path of the load circuit 1 → the switching element Q ₂ → the capacitor C ₂ . At this time, the voltage V _C2 across the capacitor C ₂ gradually decreases, and when the voltage V _C2 across the capacitor C ₂ becomes lower than the output voltage of the rectifier DB, as shown in FIG. rectifier DB → inductor L ₁ and the load circuit 1 → switching element Q ₂ → rectifier DB → AC power source V
The current flows through the path s, and the input current is drawn from the AC power supply Vs. Thereafter, when the switching element Q ₂ is turned off, as shown in FIG. 8 (e), the rectifier DB from the AC power source Vs → inductor L ₁ and the load circuit 1 → diode D ₁
A current flows through a path of → capacitor C ₁ → rectifier DB → AC power supply Vs, and when the current becomes zero, the state returns to the state of FIG.

As described above, the switching elements Q ₁ and Q ₂
Since the input current is drawn from the AC power supply Vs in one cycle of the on / off operation of the input current, the input current is drawn at a high frequency, and the high-frequency component of the input current can be reduced. Therefore,
By using this circuit, the harmonic component of the input current can be suppressed with a relatively small number of components, and the input power factor can be increased.
Circuit size and cost can be reduced.
Note that the use of the field-effect transistor as the switching element Q _1, Q _2, the parasitic diode of the field effect transistor also serves as the diodes D _1, D _2, it is possible to omit the diodes D _1, D _2.

[0007] Further, as this type of discharge lamp lighting device,
A circuit configuration as shown in FIG. 9 has also been proposed. This
The discharge lamp lighting device of FIG.₁And con
Densa C₁Switching element connected between both ends of
Q₁, Q_TwoAnd the switching element Q₁, Q_Two
D connected in anti-parallel to₁, D_TwoWhen,
Capacitor C₁Cathodes are connected to the high potential side of
Diode D_Three, D_FiveAnd the diode D_ThreeAnneau
The cathode is connected to the ₁of
Diode D with anode connected to low potential side_FourAnd da
Iod D_FiveOne end is connected to the anode of
Capacitor C₁With the other end connected to the low potential side of
Sa C_FourAnd the switching element Q₁, Q_TwoConnection points and dies
Aether D_FiveAnd capacitor C_FourConnected to the connection point of
Load circuit 1 and diode D_FiveAnd capacitor C_Four
Connection point and diode D_Three, D_FourConnected to the connection point of
And an AC power supply Vs. Here, the switch
Ching element Q₁, Q_TwoIs high by a control circuit not shown.
It is turned on and off alternately by the frequency, and the high-frequency power
Supply.

Here, the ON / OFF operation of the switching elements Q ₁ and Q ₂ will be described with reference to FIGS. The polarity of the power supply voltage of the AC power supply Vs is assumed to be positive in the direction of the arrow in FIG. 9, and the operation when the polarity of the AC power supply Vs is positive will be described below. As shown in FIG. 10A, when the switching element Q ₁ is turned on and the switching element Q ₂ is turned off, the diode D ₁ → the capacitor C _{1 is transferred} from the load circuit 1 in the direction of the current flowing through the load circuit 1 until then. →
Current flows through the path of the capacitor C ₄ → load circuit 1 (mode 1). When all the energy stored in the load circuit 1 is released, as shown in FIG.
_{From 1} , the switching element Q ₁ → the load circuit 1 → the capacitor C ₄ → the current flows through the path of the capacitor C ₁ and the load circuit 1
Power is supplied to the voltage across the capacitor C ₄ is gradually increased (mode 2). When the voltage across the capacitor C ₄ is equal to the supply voltage of the AC power source Vs, more current is not flowing into the capacitor C _4. At this time,
Since the current still flows in the load circuit 1 in the same direction, the diode D ₃ → the switching element Q ₁ → the load circuit 1 as shown in FIG.
→ Current flows through the path of the AC power supply Vs (mode 3).

[0009] Next, when the switching element Q ₁ is off, the switching element Q ₂ is turned on, as shown in FIG. 10 (d), to release the energy stored in the load circuit 1 so far, the AC power source Vs A current flows through a path of → diode D ₃ → capacitor C ₁ → diode D ₂ → load circuit 1 → AC power supply Vs (mode 4). When the load circuit 1 releases all the energy stored, as shown in FIG. 10 (e), a capacitor C ₄ as a power supply, a capacitor C
_{From 4} , the current flows through the path of the load circuit 1 → the switching element Q ₂ → the capacitor C ₄ , and the voltage across the capacitor C ₄ gradually decreases (mode 5).

After that, when the switching element Q ₁ is turned on and the switching element Q ₂ is turned off, the mode shifts to the mode 1 state, and the energy stored in the load circuit 1 until then is released. Although the polarity of the power supply voltage of the AC power source Vs is performed the same operation in the case of negative, when the polarity of the supply voltage is positive, when the ON switching element Q _1, a diode D
Respect from the AC power source Vs through a ₃ to that supply power directly to the load circuit 1, when the polarity of the power supply voltage is negative, when the ON switching element Q _2, via a diode D _4, the AC power source From Vs to load circuit 1 → switching element Q
The operation differs from the operation when the polarity of the power supply voltage is positive in that the power of the load circuit 1 is directly supplied through the path of ₂ → diode D ₄ → AC power supply Vs.

Further, when the polarity of the power supply voltage of the AC power source Vs is negative, because of the diode D _5, the voltage across the capacitor C ₄ is not rise above the voltage across the capacitor C _1. Accordingly, the peak value of the voltage across the capacitor C ₄ is cut, the stress is reduced across the capacitor C _4. Incidentally, the capacitance of the capacitor C ₄ is preferably a small capacity of about perform the charge and discharge of electric charges in one cycle of the on-off switching element Q _1, Q _2.

By the above operation, the AC power supply Vs
Input current over substantially the entire area of one cycle of the AC power supply Vs
It can flow and the power factor can be improved. here
FIG. 11 shows a circuit configuration of the circuit of FIG.
Shown in In the circuit of FIG. 11, the die shown in FIG.
Aether D_FiveAnd the switching element Q ₁, Q_TwoTo M
OS type field effect transistor (hereinafter abbreviated as MOSFET)
S) Q₁', Q_Two'And MOSFET Q₁', Q_Two'
Diode D₁, D_TwoIs also used
You. Further, the AC power supply Vs and the capacitor C_FourConnection points and
Switching element Q₁', Q_Two'Between the connection point
Path 1 and inductor L₁And load circuit 1
Power supply Vs and capacitor C_FourOne end is connected to the connection point of
Inductor L_TwoAnd the inductor L_TwoTo the other end
When the power supply terminal of the filament is connected, the MOS
FETQ₁', Q_Two'The other filament power to the connection point
Discharge lamp La made of, for example, a fluorescent lamp to which side terminals are connected.
And between the non-power supply side terminals of both filaments of the discharge lamp La.
Continued capacitor C_ThreeIt is composed of

Next, each part in one cycle of the AC power supply Vs
12 (a) to 12 (d). A in the figure is AC
This is the voltage waveform of the power supply Vs, and B in the figure is the input current waveform.
You. In the figure, C is a capacitor C_Three, And D in the figure
Is a lamp current waveform flowing through the discharge lamp La, and E is an inductor
Kuta L₁, L_TwoIs the sum of the currents flowing through
P ₁, P_Two, P_ThreeIn MOSFETQ₁', Q_Two'Flow
FIGS. 12B to 12D show the currents flowing. Where the exchange
When the polarity of the power supply voltage of the power supply Vs is positive,
In the vicinity of the peak value, the MOSFET Q₁Current flowing through
The waveform is shown in FIG._TwoCurrent flowing in '
The shape is as shown in FIG. On the other hand, the power supply of the AC power supply Vs
When the polarity of the voltage is negative,
And MOSFETQ₁Fig. 12
(D), MOSFET Q_TwoFig. 12
(B). Also, the power supply voltage of the AC power supply Vs is 0V
MOSFETQ near₁', Q_TwoNo current flowing through
This is also as shown in FIG.

As described above, by using this circuit configuration, it is possible to suppress the harmonic component of the input current and increase the input power factor with a relatively small number of components, thereby reducing the size and cost of the circuit. Can be realized.

[0015]

By the way, when a discharge lamp such as a fluorescent lamp starts discharging, a transition is made from glow discharge to arc discharge. Generally, the lamp voltage applied to the discharge lamp is high, Glow discharge occurs when the discharge current is small. Further, it is known that when the discharge current is increased in a state where a glow discharge is occurring, the glow discharge shifts to an arc discharge. Note that the lamp voltage applied to the discharge lamp may be a voltage applied to both ends of the discharge lamp, and also a ground potential between the lamp and the ground.

Here, in the circuits shown in FIGS. 7 and 11,
Equivalently, it is considered that a very small capacitor is connected between the ground line on the circuit diagram and the ground,
The potential difference V between the ground line and ground on the circuit diagram
g occurs. For example, in the circuit shown in FIG. 13, the discharge lamp La connected to the connection point of the switching elements Q ₁ and Q ₂
The potential of the power supply-side terminals of the filament f _2, and the potential Vg of the ground line, the potential of the ground line (GND) V
g in between potential plus the voltage across the capacitor C ₁ becomes potential such as switched at a high frequency. The potential of the power source side terminal of the inductor L ₂ connected to the discharge lamp La filament f ₁ is a voltage was applied to the inductor L ₂ for resonance with small capacitor to the potential of the ground line potential. In this circuit, the potential of the power supply side terminal of both filaments f ₁ and f ₂ of the discharge lamp La as viewed from the ground is lower than that of a half-bridge circuit in which one end of the discharge lamp La is connected to the ground line as shown in FIG. Therefore, the voltage was relatively high, and glow discharge was likely to occur. Therefore, in this circuit, the glow discharge shifts to the arc discharge at a relatively low lamp voltage.

Incidentally, in the lighting device of the discharge lamp La composed of a fluorescent lamp, it is necessary to sufficiently preheat the cathode before the start of discharge in order to extend the life. In order to reduce the manufacturing cost of the lighting device, when a capacitor preheating method in which a preheating current is applied to the filament of the discharge lamp La via a capacitor before the start of discharge, a circuit shown in FIGS. 7, 11 and 13 is used. Since the transition from glow discharge to arc discharge is performed at a relatively low lamp voltage, the lamp is started before a sufficient preheating current is secured, resulting in a problem that the lamp life is shortened. Therefore, if the capacitance of the preheating capacitor is increased, a sufficient preheating current can be ensured, but there is a problem that the filament loss at the time of rated lighting increases and the efficiency deteriorates.

The present invention has been made in view of the above problems, and an object of the present invention is to secure a sufficient preheating current without deteriorating the efficiency and to extend the lamp life. To provide a discharge lamp lighting device.

[0019]

According to a first aspect of the present invention, there is provided a rectifier for rectifying an AC power, a first capacitor for smoothing a rectified voltage of the rectifier, and
It is connected in parallel with the first capacitor and turns on alternately at high frequency.
A series circuit including the first and second switching elements to be turned off, and a parallel circuit including a load circuit and a charging circuit connected between a connection point between the first and second switching elements and one end of the DC output terminal of the rectifier. One end is connected to a connection point between the rectifier and the parallel circuit including the circuit, the charging circuit and the load circuit, and the other end is connected to one of the terminals of the first capacitor to form a resonance circuit together with the charging circuit and the load circuit. A charging circuit comprising at least one inductor or a transformer, a load circuit comprising at least one inductor, a capacitor and a discharge lamp, and one end of an inductor constituting the load circuit. Since it is connected to the connection point of the first and second switching elements, the ground potential of the discharge lamp on the first and second switching elements side From the potential at a high frequency to switch between the potential of the ground line and the potential of the ground line plus the voltage across the first capacitor by a voltage generated at both ends of the inductor forming the load circuit. It can be a potential. Further, compared to the case where the inductor constituting the load circuit is connected to the rectifier with respect to the discharge lamp, the ground potential of the discharge lamp on the rectifier side can be set to a potential lowered by the voltage generated at both ends of the inductor. .

According to a second aspect of the present invention, a rectifier for rectifying an AC power supply, a first capacitor having one end connected to a low potential side of a DC output terminal of the rectifier and for smoothing a rectified voltage of the rectifier, First and second switching elements connected in parallel with a capacitor and alternately turned on and off at a high frequency; a small-capacity third capacitor connected between the DC output terminals of the rectifier; and a DC output on the high potential side of the rectifier A parallel circuit consisting of a charging circuit and a load circuit connected between the end and a connection point of the first and second switching elements, the charging circuit comprising at least one inductor or a transformer, and the load circuit comprising at least One inductor, a capacitor and a discharge lamp are connected, and one end of an inductor forming a load circuit is connected to a connection point of the first and second switching elements. Therefore, the ground potential of the discharge lamps on the first and second switching elements is cut at a high frequency between the ground line potential and the potential obtained by adding the voltage across the first capacitor to the ground line potential. The potential can be set to a potential lower than the replaced potential by a voltage generated at both ends of the inductor constituting the load circuit. In addition, since the ground potential of the discharge lamp on the rectifier side is the potential obtained by adding the voltage of both ends of the small-capacity third capacitor to the potential of the ground line, the ground potential at both ends of the discharge lamp is reduced as compared with the conventional circuit. can do.

According to a third aspect of the present invention, a first capacitor for smoothing, a series circuit of first and second switching elements connected between both ends of the first capacitor and alternately turned on and off at a high frequency; A rectifier circuit composed of a series circuit of first and second diodes connected between both ends of the first capacitor, one end of which is connected to a connection point of the first and second switching elements, and the other end of which is an alternating current. A parallel circuit of a charging circuit and a load circuit connected to a connection point of the first and second diodes via a power supply, a connection point of the parallel circuit of the charging circuit and the load circuit and the AC power supply, and a DC output terminal of a rectifier circuit A charging circuit comprising at least one inductor or a transformer, and a load circuit comprising at least one inductor, a capacitor, and a discharge lamp. In addition, since the inductor constituting the load circuit is connected to the connection point of the first and second switching elements, the ground potential of the discharge lamps on the first and second switching elements is reduced to the potential of the ground line. When,
A potential lower than a potential that switches at a high frequency between a potential of the ground line and a potential obtained by adding a voltage between both ends of the first capacitor by a voltage generated at both ends of the inductor forming the load circuit can be obtained. Also, since the ground potential of the discharge lamp on the AC power supply side is a voltage obtained by adding the voltage across the small-capacity fourth capacitor to the ground line potential,
As compared with the conventional circuit, the ground potential at both ends of the discharge lamp can be reduced.

According to a fourth aspect of the present invention, in the first to third aspects, the load circuit includes an inductor having one end connected to a connection point of the first and second switching elements, and a power supply side terminal of one of the filaments. And a fifth capacitor connected between the non-power-supply-side terminals of both filaments of the fluorescent lamp, so that one end of the inductor is connected to the non-power-supply-side terminals of both filaments of the fluorescent lamp. The potential can be reduced.

[0023]

Embodiments of the present invention will be described with reference to the drawings.
I will explain. (Embodiment 1) The discharge lamp lighting device of this embodiment is
As shown in the circuit diagram, rectification for full-wave rectification of the AC power supply Vs
And a first capacitor for smoothing the rectified voltage.
Capacitor C₁And the capacitor C₁Connected between both ends of the
First and second switching elements that are turned on and off each other
Switching element Q composed of a bipolar transistor
₁, Q_TwoAnd the switching element Q₁, Q_TwoTo
Diodes D connected in anti-parallel₁, D_TwoAnd switch
Ching element Q₁, Q_TwoConnection point and low potential side of rectifier DB
Load circuit 1 connected between the DC output terminal of
A parallel circuit comprising a circuit 2, a load circuit 1 and a charging circuit 2
One end is connected to the connection point between the parallel circuit consisting of
And the capacitor C₁Other terminal on the low potential side of
A second capacitor having a small capacitance connected to the end
Capacitor C_TwoIt is composed of

Here, one end of the load circuit 1 is switched
Element Q₁, Q_TwoIndact L connected to the connection point_Two
And one filament f₁Rectifier DB
Connected to the DC output terminal on the low potential side of
Filament f_TwoIs the inductor L_TwoOther
A discharge lamp La made of, for example, a fluorescent lamp connected to the end;
Both filaments f of electric lamp La₁, F_TwoBetween the non-power side terminals
C, the fifth capacitor connected to_ThreeFrom
Be composed. On the other hand, the charging circuit 2 has an inductor L ₁From
Is done.

The operation of this circuit will be described with reference to FIGS.
It will be described in the light of the above. As shown in FIG.
Element Q₁Is on, switching element Q _TwoIs off
If the capacitor C₁From switching element Q₁→ Load times
Path 1 and inductor L₁→ Capacitor C_Two→ Capacitor
C₁Current flows in the path of_TwoVoltage V
_C2Is the inductor L₁, L_TwoAnd increase by resonance.

When the voltage V _C2 across the capacitor C ₂ increases and the sum of the voltage V _C2 across the capacitor C ₂ and the power supply voltage of the AC power supply Vs becomes higher than the voltage V _C1 across the capacitor C ₁ , FIG. As shown in FIG. 2 (b), a current flows from the AC power supply Vs through a route of the rectifier DB → the switching element Q ₁ → the load circuit 1 and the inductor L ₁ → the rectifier DB → the AC power supply Vs, and an input current is drawn from the AC power supply Vs. It is.

Next, when the switching element Q ₁ is turned off and the switching element Q ₂ is turned on, as shown in FIG. 2C, the rectifier DB → the capacitor C ₁ → the switching element Q ₂ → the load circuit 1 as shown in FIG. And inductor L ₁ →
A current flows through a path from the rectifier DB to the AC power supply Vs. Thereafter, as shown in FIG. 2D, the resonance of the inductors L ₁ and L ₂ and the capacitors C ₂ and C ₃ causes the capacitor C
_{From 2} , the resonance current flows through the path of the load circuit 1 and the inductor L ₁ → the switching element Q ₂ → the capacitor C ₂ .

Furthermore, as shown in FIG. 2 (e), the load circuit 1 and the inductor from the capacitor C ₂ L ₂ → switching element Q ₁ → current continues to flow in a path of the capacitor C ₁ → capacitor C _2, the current is zero Then, the state returns to the state shown in FIG. The basic operation of the circuit of this embodiment, whereas it is substantially the same as the circuit of Figure 7 described above, the circuit of FIG. 7 draws input current through the switching element Q ₂ in the circuit of this embodiment is different in that draws an input current through the switching element Q _1.

FIG. 3 shows the ground potential _VA at the power supply side terminal (point P ₁ in FIG. ₁ ) of the filament f ₁ of the discharge lamp La connected to the connection point between the rectifier DB and the capacitor C ₂ . FIG. 4 shows the ground potential V _B at the power supply side terminal (point P _{2 in} FIG. 1) of the filament f ₂ of the discharge lamp La connected to the inductor L ₂ . In FIGS. 3 and 4, the ground potentials V _A and V _B and the power supply voltage of the AC power supply Vs are shown with different scales. Here, the ground potential _VA indicates the waveform of the potential of the ground line on the circuit diagram of this circuit (that is, the potential Vg viewed from the ground). On the other hand, in the circuit shown in FIG. 13 described above, the ground potential V _A ′ at the power supply side terminal (point P _{1 in} FIG. 13) of the filament f ₁ of the discharge lamp La connected to the inductor L ₂ is shown in FIG.
To show the switching elements Q _1, Q ₂ of the connection to the connecting point to the discharge lamp La of the power supply-side terminals of the filament f ₂ (Fig. 1
FIG. 15 shows the ground potential V _B ′ at point P ₂ ) in FIG. 14 and 15, the ground potential V _A ′,
V _B ′ and the power supply voltage of the AC power supply Vs are shown on a different scale.

Comparing FIG. 3 and FIG. 14, the ground potential V _{A at} the point P ₁ of the circuit is equal to the point P ₁ of the circuit shown in FIG.
_Both the amplitude and the peak value are lower than the ground potential V _A ′ at ₁ . This ground potential V _A at a point P ₁ in FIG. 1, as compared with the ground potential V _A 'at the point P ₁ in FIG. 13, since only lower voltage fraction generated in the inductor L _2. Similarly, comparing FIG. 4 and FIG. 15, the ground potential V _{B at} the point P ₂ of the present circuit is smaller in both amplitude and peak value than the ground potential V _B ′ at the point P ₂ of the circuit shown in FIG. ing. This is ground potential V _B at a point P ₂ in FIG. 1, as compared to the ground potential V _B 'at the point P ₂ in FIG. 13, inductor L ₂ when viewed from the connection point of the switching elements Q _1, Q ₂ Is lower by the voltage generated in

As described above, by connecting the resonance inductor L ₂ between the connection point of the switching elements Q ₁ and Q ₂ and the discharge lamp La, the ground potential of the power supply side terminal of both filaments of the discharge lamp La is obtained. Can be reduced. Therefore, since the discharge lamp La does not start until an appropriate voltage across the discharge lamp La is applied, the preheating current of the discharge lamp La can be sufficiently secured, and the life of the discharge lamp La can be extended. Can be. Moreover, since the preheating current of the discharge lamp a sufficiently secured, can be relatively small design the capacitance of the capacitor C ₃ for preheating, it improves the efficiency of switching.

(Embodiment 2) As shown in the circuit diagram of FIG. 5, the discharge lamp lighting device of this embodiment includes a rectifier DB for rectifying an AC power supply Vs, and a DC output terminal on the low potential side of the rectifier DB. Is connected and a capacitor C _{1 as} a _first capacitor for smoothing the rectified voltage of the rectifier DB, and a first capacitor C ₁ connected between both ends of the capacitor C ₁ and turned on and off alternately.
And a second series circuit of a switching element serving as the switching element Q _1, Q _2, switching element Q _1, Q ₂
Diodes D ₁ and D ₂ connected in anti-parallel to each other, a capacitor C ₂ as a small-capacity third capacitor connected between the DC output terminals of the rectifier DB, and a DC output terminal on the high potential side of the rectifier DB. It comprises a parallel circuit comprising a load circuit 1 and a charging circuit 2 connected between the connection point of the switching elements Q ₁ and Q ₂ .

[0033] Here, the load circuit 1, Indataku L ₂ having one end connected to a connection point of the switching elements Q _1, Q ₂
And the power supply side terminal of _one filament f1 is connected to the rectifier DB
And a discharge lamp La composed of, for example, a fluorescent lamp, which is connected to the connection point between the DC output terminal on the high potential side and the capacitor C ₂ and the power supply side terminal of the other filament f ₂ is connected to the other end of the inductor L _2. , and a fifth capacitor serving capacitor C ₃ connected between the non-power supply side terminal of the discharge lamp both filaments of La f _1, f _2. On the other hand, the charging circuit 2 is composed of an inductor L _1.

The operation of this circuit is substantially the same as the operation of the conventional circuit shown in FIG. 7, and a description thereof will be omitted.
Here, the potential at the connection point of the switching elements Q ₁ and Q ₂ is a high frequency between the potential Vg of the ground line on the circuit diagram and the potential obtained by adding the voltage across the capacitor C ₁ to the potential Vg of the ground line. The switching potential is obtained. In this circuit, the switching element Q _1, a resonance between the connection point Q ₂ 'and the discharge lamp La in so the inductor L ₂ is connected, is connected to the inductor L ₂ the filaments f ₂ of the power supply-side terminal ground potential (potential viewed from the ground) has a potential Vg of the ground line on the circuit diagram, the potential at which the switching at a high frequency between a potential obtained by adding the voltage across the capacitor C ₁ to the potential Vg of the ground line , the dropped by the voltage generated across the inductor L ₂ of the resonant voltage. Further, ground potential of the power supply-side terminals of the rectifier DB side filament f _1, since the addition of the voltage across the capacitor C ₂ of small capacity to the potential Vg of the ground line potential,
Compared with the conventional circuit of FIG. 7, the maximum value of the ground potential of the power supply side terminals of both filaments f ₁ and f ₂ of the discharge lamp La can be reduced.

Therefore, unlike the conventional circuit shown in FIG. 7, the discharge lamp La does not shift from glow discharge to arc discharge at a relatively low lamp voltage. In addition, a sufficient preheating current can be ensured without complicating the circuit configuration of the discharge lamp lighting device, and the life of the discharge lamp La can be extended. (Embodiment 3) FIG. 6 is a circuit diagram of a discharge lamp lighting device according to this embodiment.

This circuit includes a first capacitor for smoothing.
Capacitor C₁And the capacitor C ₁Connected between both ends of
First and second switches that alternately turn on and off at high frequency
MOS field effect transistor (hereinafter, referred to as a switching element)
MOSFET)₁', Q_Two'Series circuit and capacitor
Sensor C₁First and second diodes connected between both ends of the
The diode D_Three, D_FourRectifier consisting of a series circuit of
Road 3 and one end of MOSFET Q₁', Q_TwoConnect to '
And the other end is connected via an AC power supply Vs.
Do D_Three, D_FourCircuit 1 connected to the connection point of
A parallel circuit comprising a circuit 2, a load circuit 1 and a charging circuit 2
Of the rectifier circuit 3 and the connection point between the parallel circuit of
A small capacity fourth capacitor connected between one end of the DC output end
Capacitor C_FourIt is composed of

Here, one end of the load circuit 1 is MOSFE
An inductor L ₂ connected to a connection point of TQ ₁ ′ and Q ₂ ′,
With one power supply terminal of the filament f ₁ is connected to an AC power source Vs, the discharge lamp La power supply side terminal of the other filament f ₂ is made of, for example, a fluorescent lamp is connected to the other end of the inductor L _2, release Both filaments f of electric lamp La
_1, and a fifth capacitor serving capacitor C ₃ connected between the non-power supply side terminal of f _2. On the other hand, the charging circuit 2 is composed of an inductor L _1.

The operation of this circuit corresponds to the operation shown in FIG.
Since the circuit is almost the same as that of the conventional circuit, the description is omitted. here
And MOSFET Q₁', Q_TwoThe potential of the connection point '
The potential Vg of the upper ground line and the potential of the ground line
Capacitor C₁Between the voltage obtained by adding the voltage across
At a high frequency. In this circuit,
MOSFET Q₁', Q_Two'Between the connection point and the discharge lamp La
Inductor L for resonance _TwoConnected,
L_TwoFilament f connected to_TwoPower side terminal pair
Ground potential (potential viewed from the ground) is the ground on the circuit diagram
Line potential Vg and the ground line potential Vg.
Densa C₁Between high and low potentials.
From the potential that switches, the resonance inductor L_TwoBoth
The potential drops by the voltage generated at the end. Also,
Power supply Vs and capacitor C_FourConnected to the
Lament f₁The ground potential of the power supply side terminal of
Capacitor C with a small capacity_FourIs applied.
Since the potential becomes higher than that of the conventional circuit shown in FIG.
Both filaments f of the discharge lamp La₁, F_TwoPower supply terminal
The maximum value of the ground potential can be reduced.

Therefore, unlike the conventional circuit shown in FIG. 11, the discharge lamp La does not shift from glow discharge to arc discharge at a relatively low lamp voltage. In addition, a sufficient preheating current can be ensured without complicating the circuit configuration of the discharge lamp lighting device, and the life of the discharge lamp La can be extended.

[0040]

As described above, the first aspect of the present invention provides a rectifier for rectifying an AC power supply, a first capacitor for smoothing the rectified voltage of the rectifier, and a high frequency alternately connected in parallel with the first capacitor. A series circuit including first and second switching elements that are turned on and off, and a load circuit and a charging circuit that are connected between a connection point between the first and second switching elements and one end of a DC output terminal of the rectifier. One end is connected to the connection point between the rectifier and the parallel circuit comprising the charging circuit and the load circuit, and the other end is connected to one of the terminals of the first capacitor. A second capacitor constituting a circuit; a charging circuit comprising at least one inductor or a transformer; and a load circuit comprising at least one inductor, a capacitor and a discharger. Together consist and, because it connects one end of the inductor constituting the load circuit to a connection point of the first and second switching elements, first and second
A load circuit is configured from a potential that switches at a high frequency the ground potential of the discharge lamp on the switching element side between a ground line potential and a potential obtained by adding the voltage of both ends of the first capacitor to the ground line potential. It is possible to set the potential to drop by the voltage generated at both ends of the inductor. Also, compared to the case where the inductor constituting the load circuit is connected to the rectifier with respect to the discharge lamp, the ground potential of the discharge lamp on the rectifier side is reduced by the voltage generated at both ends of the inductor. The ground potential at both ends can be reduced. Therefore, since the discharge lamp does not start until an appropriate starting voltage is applied, a sufficient preheating current can be secured, and the life of the discharge lamp can be extended.

According to a second aspect of the present invention, there is provided a rectifier for rectifying an AC power supply, a first capacitor having one end connected to a low potential side of a DC output terminal of the rectifier and for smoothing a rectified voltage of the rectifier, First and second switching elements connected in parallel with a capacitor and alternately turned on and off at a high frequency; a small-capacity third capacitor connected between the DC output terminals of the rectifier; and a DC output on the high potential side of the rectifier A parallel circuit consisting of a charging circuit and a load circuit connected between the end and a connection point of the first and second switching elements, the charging circuit comprising at least one inductor or a transformer, and the load circuit comprising at least One inductor, a capacitor and a discharge lamp are connected, and one end of an inductor forming a load circuit is connected to a connection point between the first and second switching elements. Therefore, the ground potential of the discharge lamps on the first and second switching elements is switched at a high frequency between the ground line potential and the potential obtained by adding the voltage of the first capacitor to the ground line potential. The potential can be set to be lower than the potential by a voltage generated at both ends of the inductor forming the load circuit. In addition, since the ground potential of the discharge lamp on the rectifier side is the potential obtained by adding the voltage of both ends of the small-capacity third capacitor to the potential of the ground line, the ground potential at both ends of the discharge lamp is reduced as compared with the conventional circuit. can do. Therefore, since the discharge lamp does not start until an appropriate starting voltage is applied, a sufficient preheating current can be secured, and the life of the discharge lamp can be extended.

According to a third aspect of the present invention, there is provided a series circuit of a first capacitor for smoothing, a first and a second switching element connected between both ends of the first capacitor and alternately turned on and off at a high frequency. A rectifier circuit composed of a series circuit of first and second diodes connected between both ends of the first capacitor, one end of which is connected to a connection point of the first and second switching elements, and the other end of which is an alternating current. A parallel circuit of a charging circuit and a load circuit connected to a connection point of the first and second diodes via a power supply; a connection point of the parallel circuit of the charging circuit and the load circuit with an AC power supply; and a DC output terminal of a rectifier circuit. A charging circuit comprising at least one inductor or a transformer, and a load circuit comprising at least one inductor, a capacitor and a discharge lamp. In addition, since the inductor constituting the load circuit is connected to the connection point of the first and second switching elements, the ground potential of the discharge lamps on the first and second switching elements is set to the potential of the ground line. ,
A potential lower than a potential that switches at a high frequency between a potential of the ground line and a potential obtained by adding a voltage between both ends of the first capacitor by a voltage generated at both ends of the inductor forming the load circuit can be obtained. Also, since the ground potential of the discharge lamp on the AC power supply side is a voltage obtained by adding the voltage across the small-capacity fourth capacitor to the ground line potential,
Compared with the conventional circuit, the ground potential at both ends of the discharge lamp can be reduced. Therefore, since the discharge lamp does not start until an appropriate starting voltage is applied, a sufficient preheating current can be secured, and the life of the discharge lamp can be extended.

According to a fourth aspect of the present invention, the load circuit includes an inductor having one end connected to a connection point between the first and second switching elements and a fluorescent light having one end connected to a power supply side terminal of one of the filaments. Since it is composed of the lamp and the fifth capacitor connected between the non-power supply terminals of both filaments of the fluorescent lamp, the ground potential of the power supply terminals of both filaments of the fluorescent lamp can be reduced. Therefore, the fluorescent lamp is not started until an appropriate starting voltage is applied to the fluorescent lamp, so that a sufficient preheating current can be secured, and the life of the fluorescent lamp can be extended.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a discharge lamp lighting device according to a first embodiment.

FIGS. 2A to 2E are views for explaining the operation of the above.

3 is a waveform diagram showing a ground potential at a point P ₁ of the same.

4 is a waveform diagram showing a ground potential at a point P _2; FIG.

FIG. 5 is a circuit diagram showing a discharge lamp lighting device according to a second embodiment.

FIG. 6 is a circuit diagram showing a discharge lamp lighting device according to a third embodiment.

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

FIGS. 8A to 8E are diagrams for explaining the operation of the above.

FIG. 9 is a circuit diagram showing another discharge lamp lighting device of the above.

FIGS. 10A to 10E are diagrams for explaining the operation of the above.

FIG. 11 is a circuit diagram showing another discharge lamp lighting device of the above.

12 (a) to 12 (d) are waveform diagrams showing waveforms of respective parts of the above.

FIG. 13 is a circuit diagram showing still another discharge lamp lighting device of the above.

14 is a waveform diagram showing a ground potential at a point P ₁ of the same.

15 is a waveform diagram showing a ground potential at a point P _2; FIG.

[Explanation of symbols]

1 a load circuit 2 charging circuit C ₁ capacitor DB rectifying circuit f _1, f ₂ filaments L ₂ inductor La discharge lamp Q _1, Q ₂ switching elements

Claims (4)

[Claims] 1. A rectifier for rectifying an AC power supply, a first capacitor for smoothing a rectified voltage of the rectifier, and first and second switching elements connected in parallel with the first capacitor and turned on and off alternately at a high frequency. , A parallel circuit consisting of a load circuit and a charging circuit connected between the connection point of the first and second switching elements and one end of the DC output terminal of the rectifier, and a charging circuit and a load circuit. One end is connected to the connection point between the parallel circuit and the rectifier,
A second capacitor having the other end connected to one of the terminals of the first capacitor and forming a resonance circuit together with the charging circuit and the load circuit, the charging circuit comprising at least one inductor or a transformer, and At least one
A discharge lamp lighting device comprising: one inductor, a capacitor, and a discharge lamp, wherein one end of an inductor forming a load circuit is connected to a connection point of the first and second switching elements. 2. A rectifier for rectifying an AC power supply, a first capacitor having one end connected to a low potential side of a DC output terminal of the rectifier, for smoothing a rectified voltage of the rectifier, and being connected in parallel with the first capacitor. First and second switching elements that are alternately turned on and off at a high frequency; a third capacitor having a small capacitance connected between the DC output terminals of the rectifier; a DC output terminal on the high potential side of the rectifier; A parallel circuit comprising a charging circuit and a load circuit connected between the connection point of the second switching element and the charging circuit, the charging circuit comprising at least one inductor or a transformer, and the load circuit comprising at least one inductor and a capacitor And a discharge lamp, and one end of an inductor constituting a load circuit is connected to a connection point of the first and second switching elements. Lamp lighting device. 3. A first capacitor for smoothing, a series circuit of first and second switching elements connected between both ends of the first capacitor and alternately turned on and off at a high frequency;
A rectifier circuit comprising a series circuit of first and second diodes connected between both ends of a capacitor, and one end connected to a connection point of the first and second switching elements, and the other end connected to an AC power supply. A parallel circuit of a charging circuit and a load circuit connected to a connection point of the first and second diodes via a connection point between the parallel circuit of the charging circuit and the load circuit and the AC power supply, and one end of a DC output terminal of the rectifier circuit And a fourth capacitor connected between the first and second capacitors, the charging circuit includes at least one inductor or a transformer, and the load circuit includes at least one inductor, a capacitor, and a discharge lamp, and forms a load circuit. The first inductor
And a discharge lamp lighting device connected to a connection point of the second switching element. 4. A load circuit comprising: an inductor having one end connected to a connection point of the first and second switching elements; a fluorescent lamp having one end connected to a power supply terminal of one of the filaments; 4. The discharge lamp lighting device according to claim 1, further comprising a fifth capacitor connected between the non-power-supply-side terminals of the two filaments.