JPH10144488A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device wherein stress applied to a component constituting an electronic ballast can be reduced, size reduction can be performed and a cost can be reduced. SOLUTION: An electronic ballast is constituted by a DC power circuit 2 and a power converter circuit 3. In a control circuit 11, based on lamp voltage V1a and voltage VL of a secondary winding N2 of an inductor L1 , a switching element Q1 is on/off-controlled. The control circuit 11 has an inverter 18 inverting a control signal S1 output from a PWM circuit 17, for instance, like a NOT circuit, timer circuit 19 performing a prescribed time count based on an output signal S2 of the inverter 18 to output a trigger pulse signal S3 and a switching element Q20 turned on by the trigger pulse signal S3 from the timer circuit 19. In the control circuit 11, when a discharge lamp La is normally lighted, control is performed such that the switching element Q1 is turned on when a current flowing in the inductor L1 is generated substantially zero.

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 such as a fluorescent lamp or an HID lamp.

[0002]

2. Description of the Related Art Conventionally, a copper-iron type ballast (a so-called copper ballast) has been used as a lighting device for lighting a discharge lamp such as a fluorescent lamp or an HID lamp. However, since the copper-iron type ballast becomes heavy and the ballast itself becomes large, in recent years, electronic components such as switching elements and diodes have been developed in order to reduce the weight, size, and function of the ballast. A so-called electronic ballast using is used. Hereinafter, a discharge lamp lighting device for stably lighting a discharge lamp using an electronic ballast will be described.

As shown in FIG. 14, for example, an electronic ballast includes a DC power supply circuit 2 to which an AC output of an AC power supply AC is input and outputs a DC, and an electric power supplied to an output terminal of the DC power supply circuit 2 and supplied to a discharge lamp La. And a power conversion circuit 3 for adjusting and controlling the power. FIG. 15 shows a specific example of an electronic ballast circuit.
A rectifier circuit 5 for rectifying the C AC output, which is connected between the output ends of the rectifier circuit 5 is constituted by a smoothing capacitor C ₀ for smoothing the output of the rectifier circuit 5, rectifies the AC voltage of the AC power source AC into a DC voltage Smooth. The power converter circuit 3 includes a switching element Q _1, the inductor L _1, diode D
₁ , a capacitor C _1, and a control circuit 11 for controlling ON / OFF of the switching element Q _1. Discharge lamps La are connected to both ends of the capacitor C ₁ . Here, the switching element Q _1, a diode D _1, inductor L ₁
Constitutes a step-down chopper circuit. The operation of the step-down chopper circuit is well known and will not be described. The control circuit 11 detects the voltage across the capacitor C ₁ as the lamp voltage Vla of the discharge lamp La, and controls the switching frequency or on-duty for turning on and off the switching element Q ₁ at a high frequency in accordance with the lamp voltage Vla, thereby controlling the discharge lamp. The power supplied to La is adjusted. The power supplied to the discharge lamp La may be adjusted by detecting the lamp current flowing through the discharge lamp La and according to the lamp current.

[0004] Here, a current flowing through the inductor L ₁ IL
Let's focus on. In the steady lighting state of the discharge lamp La,
When the switching element Q ₁ is turned on / off by the control circuit 11 based on a control signal S ₁ described later, the inductor L ₁
There are the following three modes of the current IL flowing through That is, FIG. 16 from the control circuit 11 to the switching element Q ₁ (a), FIG. 17 (a), the in the case where the control signals S ₁ as shown in FIG. 18 (a) is input, FIG. 1
As shown in FIG. 6B, the idle period ta during which the current IL does not flow
(Hereinafter, referred to as a discontinuous mode), the control signal S ₁ goes low at almost the same time as the current IL decreases to zero as there is no pause as shown in FIG. To a high level and the current IL flows again (hereinafter referred to as a zero-cross switching mode). As shown in FIG. 18B, the current IL has no idle period and is controlled before the current IL decreases to zero. signal S ₁ is mode current IL changes from the low level to the high level continuously flowing (hereinafter referred to as the continuous mode) there are three modes.

Meanwhile, in the step-down chopper circuit described above, the stress is changed according to the component by the mode of the current IL flowing through the inductor L _1, also the ripple content of the output current changes. For example, in the discontinuous mode described above, since the current IL has a pause period ta, in order to supply the same lamp current to the discharge lamp La as in the other two modes, the peak value Ia of the current IL (FIG. 16B) 17) to the peak value Ib of the current IL in the other mode (FIG. 17B).
See) and Ic ₁ must be greater than the (FIG. 18 (b) refer), since the ripple content of the output current increases, must be smoothed to increase the capacitance of the capacitor C ₁ no, the capacitor C ₁ becomes large.

On the other hand, in the above continuous mode, but can reduce the ripple component of the output current as compared with the case of the discontinuous mode, Ic ₂ (Fig. 18 as the current IL when the switching element Q ₁ is changed from off to on (b ) for the current magnitude of reference) is flowing, the voltage of the switching element Q _1,
The current changes as shown by a broken line and a solid line in FIG. Here, it is adapted to the switching element Q ₁ is to expand the time axis of the cut-switched portion A from OFF to ON in FIG. 19 (a) FIG. 19 (b), the switching loss in a portion indicated by two-dot chain line B there will occur, the temperature rise of the switching elements Q _1, there is a possibility that the switching element Q ₁ is destroyed. The switching loss in the same manner as the switching element Q ₁ also diode D ₁ is generated.

On the other hand, in the above-described zero-cross switching mode, the ripple current can be reduced as compared with the discontinuous mode, and the switching loss of the switching element Q ₁ and the diode D ₁ can be reduced as compared with the continuous mode. zero-cross switching mode is desired as the mode of the current IL flowing through the inductor L ₁ in the circuit.

FIG. 20 shows an example of a circuit for realizing the zero-cross switching mode. The basic configuration of the discharge lamp lighting device shown in FIG. 20 is substantially the same as the device shown in FIG. 15, and a secondary winding N ₂ for zero current detection for detecting that the current IL becomes zero is provided in the inductor L _1. it is obtained by adding a (primary winding N ₁ of the transformer is the inductor L _1). Here, the control circuit 11 has a circuit configuration as shown in FIG. 21 and includes the lamp voltage Vla and the secondary winding N _2.
Controlling the turning on and off of the switching element Q ₁ on the basis of the voltage VL. Here, the voltage VL varies based on the current flowing through the inductor L _1. Diodes D _{13 and} D _{14 in} FIG. 21 are protection diodes for preventing the voltage VL from falling below zero volts or exceeding the control power supply voltage Vcc.

The control circuit 11 includes a reference voltage source E ₁ and a voltage V
And compares the reference voltage V ₁ of the L and the reference voltage source E ₁ comparator 15, the control signals S ₁ such that only a high level time corresponding to the lamp voltage Vla is triggered in response to the output signal V ₂ of the comparator 15 And a PWM circuit 17 that outputs the same. The output signal V ₂ of the comparator 15 becomes high level when VL> V ₁ , and VL ≦ V
It becomes low level at ₁ (see FIG. 22 (c)). Further, the PWM circuit 17 outputs the output signal V
In response to ₂ the output signal V ₂ is triggered changes from the high level to the low level, the time corresponding to the lamp voltage Vla Ton only the control signal S ₁ is a high level (FIG. 22
(D)). That is, the switching element Q ₁ at substantially the same time the control signals S ₁ and the current IL becomes zero flowing to inductor L ₁ becomes a high level is to turn on.

The operation of the discharge lamp lighting device shown in FIG.
Will be described with reference to FIG. As shown in FIG.
Control signal S₁Is high level and switching element Q₁But
Time t₀~ T₁In between, smooth condensate
Sa C₀→ Switching element Q ₁→ Inductor L₁→ discharge
Light La → Smoothing capacitor C₀The current flows through the path
And the inductor L₁The current IL flowing through is shown in FIG.
It increases over time as shown. Meanwhile, the control signal
S₁Is low level and switching element Q₁Is off
Time t₁~ T_TwoIn between, the inductor L₁Stored in
Energy is released and the inductor L₁→ Discharge lamp L
a → Diode D₁→ Inductor L₁Current flows in the path
The inductor L₁The current IL flowing through
As shown in (a), it decreases with time. here
And the inductor L₁Secondary winding N_TwoThe voltage VL of FIG.
As shown in FIG. 2 (b), the switching element Q₁Is off
Nacta L₁At which the energy stored in the battery is released
t₁~ T_TwoBetween the high level (that is, the secondary winding
N_TwoVoltage is generated at the output), the inductor L₁Stored in
When the energy has been released (time t_Two), Low level
(Zero volts). Output signal V of comparator 15_Two
Means that the voltage VL is equal to the reference voltage V as shown in FIG.
₁From high level to low level when it becomes smaller than
Change. The PWM circuit 17 outputs the output signal V_TwoFall of
Control signal S for a predetermined on-time Ton₁Depart
Let it live. Here, the on-time Ton is equal to the lamp voltage Vla.
Determined by

[0011]

By the way, in the discharge lamp lighting device of the above-mentioned zero cross switching mode,
As the discharge lamp La, for example, a high-pressure discharge lamp such as a mercury lamp, a metal halide lamp, or a high-pressure sodium lamp may be used. High-pressure discharge lamps are roughly classified into three states: a no-load state (non-lighting state), a starting process state, and a steady lighting state. Generally, at the start of a high-pressure discharge lamp in a state where the lamp is cold (initial start), when the lamp is turned on, the lamp voltage becomes substantially zero volt, and thereafter, as the temperature of the lamp increases, the lamp voltage Vla increases. It takes about 5 to 10 minutes for the lamp voltage Vla to reach the rated lamp voltage (to reach the steady lighting state), and the starting process state is continued for this time. Next, if you try to turn off the lamp once turned on and then immediately turn it on, the inside of the lamp is high temperature and high pressure,
It cannot start lighting immediately. For this reason, it takes about 5 to 10 minutes until the lamp cools and the inside of the lamp becomes low pressure, and the no-load state is continued for this time. Less than,
The operation of the discharge lamp lighting device shown in FIG. 20 in the above three states will be described.

In the steady lighting state, an operation similar to the operation described with reference to FIG. 22 is obtained. That is, in the steady lighting state, the zero cross switching mode can be reliably realized. In unloaded condition, the output terminal of the power conversion circuit 3 is equivalent to being opened, no current IL flows most, it becomes difficult to realize a zero-cross switching mode, the switching element Q ₁ This causes a problem that the switching operation cannot be continued.

Further, in the starting process state, the lamp voltage Vla is low (lamp impedance is small), the time change of the current IL in the on period of the switching element Q ₁ as shown in FIG. 23 (a) (current rise rate ) Is large, and a sufficient current can flow through the discharge lamp La even during a slight ON period. However, the time change of the current IL in the OFF period of the switching element Q ₁ so (current reduction rate) is small (smaller absolute value of the current reduction rate as compared with the absolute value of the aforementioned current rise rate), the inductor L ₁ It takes a considerable time to release energy, and the current IL gradually decreases. Therefore, in the low starting process state lamp voltage Vla is, the control signal current IL in order to achieve a zero-cross switching mode as shown in FIG. 23 (a) inputted from the control circuit 11 to the switching element Q ₁ S ₁ is as shown in FIG. 23 (d) (Ton is shorter than the time of steady lighting state). That is, in the starting process state, the switching frequency fsw of the switching element Q ₁ is becomes much lower than that of the steady lighting state, noise switching frequency fsw is equal to or less than the audible frequency 20kHz increases There is.
As an example, when an HID lamp is used as the discharge lamp La, the relationship between the lamp voltage Vla and the switching frequency fsw is as shown in FIG. 24. When the lamp voltage Vla is low, the switching frequency fsw is lower than 20 kHz.
As the lamp voltage Vla rises, the switching frequency f
sw becomes higher.

In the case of an HID lamp, 5 to 1 is required after the lamp is turned on as described above until the lamp enters a steady lighting state.
Although it takes about 0 minutes, in order to shorten this time, the lamp must be quickly warmed by increasing the lamp current Ila when the lamp voltage Vla is low to make a transition to a steady lighting state. That is, as shown in FIG. 25, when the lamp voltage Vla is low, it is necessary to increase the lamp current Ila. In this case, the lamp current Ila
Is such that the current value when the lamp voltage Vla is substantially zero volts is approximately 1.2 to 1.5 times the current value in the steady lighting state.

However, as described above, the lamp current Il
a, when the zero-cross switching mode is realized even when the lamp voltage Vla is low, the current I
The peak value of L is approximately 1.
It needs to be 2 to 1.5 times. For this reason, since the maximum current rating of each component must be increased, there is a problem that each component is increased in size and cost is increased. The inductor L ₁ had also problems such as becomes easily saturated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a discharge lamp lighting device capable of reducing the stress applied to components constituting an electronic ballast and capable of reducing the size and cost. Is to do.

[0017]

According to a first aspect of the present invention, there is provided a DC power supply circuit having a rectifier circuit for rectifying an AC output of an AC power supply, and a DC power supply circuit connected to an output terminal of the DC power supply circuit. A power conversion circuit that adjusts and controls the power supplied to the load.The power conversion circuit includes a switching element between an output terminal of the DC power supply circuit and a diode having a cathode connected to one end of the switching element. A series circuit is connected, a series circuit of an inductor and a capacitor is connected in parallel with the diode, a discharge lamp as the load is connected in parallel with the capacitor, and the switching element is turned on and off at a high frequency, and a switching frequency or an on-duty is connected. A control circuit for controlling the power supplied to the discharge lamp by controlling
The control circuit controls the switching element to be turned on when a current flowing through the inductor becomes substantially zero when the switching element is turned off in the steady lighting state of the discharge lamp, and controls the switching element to be in a state other than the steady lighting state of the discharge lamp. In the state, the current flowing through the inductor is controlled to be a continuous current that does not become zero or the current flowing through the inductor is a discontinuous current having a pause. And the switching loss of the diode or the like can be reduced.In a state other than the steady lighting state, the peak value of the lamp current can be reduced by appropriately changing the current flowing through the inductor to a continuous current or a discontinuous current. The maximum rated value of the current of each part can be reduced, And low cost can be achieved.

According to a second aspect of the present invention, in the first aspect of the invention, a high-pressure discharge lamp is used as the discharge lamp, and the current flowing through the inductor is continuously increased in a starting process state in which the lamp voltage of the discharge lamp is lower than in a steady lighting state. Since the current is used, it is possible to shift to the steady lighting state immediately after the lamp is turned on.
According to a third aspect of the present invention, in the first or second aspect of the present invention, a polarity inversion circuit is provided between the power conversion circuit and the discharge lamp for converting a current flowing through the discharge lamp into an alternating current. It is possible to prevent the discharge lamp from being subjected to AC lighting and to bias the stress on one electrode of the lamp as compared with the case of DC lighting.

According to a fourth aspect of the present invention, in the third aspect of the present invention, two sets of series circuits of two switching elements are connected in parallel with the output terminal of the power conversion circuit as a polarity inversion circuit, and the switching in each of the series circuits is performed. A discharge lamp is connected between the connection points of the elements. According to a fifth aspect of the present invention, in the third aspect, the power conversion circuit and the polarity inversion circuit are configured by a full bridge circuit.

According to a sixth aspect of the present invention, in the third aspect of the present invention, the power conversion circuit and the polarity inversion circuit are configured by a half bridge circuit.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1A is a circuit diagram of the present embodiment, and FIG. 1B is a circuit configuration diagram of a control circuit 11. The basic configuration of this embodiment is substantially the same as the conventional configuration shown in FIG. 20, and the configuration of the control circuit 11 is different from the conventional configuration. In the control circuit 11 in the discharge lamp lighting device of the present embodiment, FIG.
In the control circuit 11 having the conventional configuration shown in FIG. ₁ , an inverter 18 for inverting the control signal S ₁ output from the PWM circuit 17 such as a NOT circuit,
A timer circuit 19 for outputting a trigger pulse signal S ₃ performs a predetermined timing based on the output signal S _2, the timer circuit 1
The trigger pulse signal S ₃ from 9 is obtained by adding a switching element Q ₂₀ to turn on.

The timer circuit 19 starts counting after the output signal S ₂ of the inverter 18 becomes high level,
Counting time and outputs a trigger pulse signal S ₃ when a predetermined value Toff. The switching element Q ₂₀ has been made to off by receiving a trigger pulse signal S _3, the switching element Q ₂₀ is turned on, the output signal V ₂ of the comparator 15 is forced to a low level.

The operation in the starting process will be described below with reference to a time chart shown in FIG. Now, time t
_{At 0} , the control signal S ₁ is at a high level (pulse width Ton)
And a switching element Q ₁ is turned on when turned, between the time t ₀ ~t ₁ control signal S ₁ is at a high level, the slope as shown in the conventional example as well as inductor L ₁ in FIGS. 2 (a) Current IL flows. Incidentally, the secondary winding N ₂ voltage V
L changes as shown in FIG. Next, at time t ₁
When the control signal S ₁ (see FIG. 2D) goes low, the switching element Q ₁ is turned off, and the current IL flows by the energy stored in the inductor L ₁ as in the conventional example. Comparator 15 compares the reference voltage V ₁ of the conventional example as well as the secondary winding N ₂ voltage VL (see FIG. 2 (b)) and the reference voltage source E _1, and the high level when the VL> V ₁ and outputs the composed output signal V _2. Here, the timer circuit 19
Counting starts at time t _{1 when} the output signal S ₂ (see FIG. 2E) of the inverter 18 that inverts the control signal S ₁ output from the PWM circuit 17 becomes high level. Upon reaching the Toff, turns on the switching element Q ₂₀ outputs a trigger pulse signal S ₃ shown in FIG. 2 (f). That is, the switching element Q ₂₀ is turned on by a trigger pulse signal S ₃ at time t _2, the output terminal of the comparator 15 is short-circuited to ground via the switching element Q ₂₀ output signal V ₂ (FIG. 2
(C) becomes low level. Therefore, Kakawawazu to current IL does not become zero, PWM circuit 17 receives the falling from the high level output signal V ₂ to a low level, the control signals S ₁ to a high level (pulse width Ton) To

[0024] That is, in this embodiment, by setting the maximum value of the off time of the switching element Q ₁ a (predetermined value Toff) by a timer circuit 19, the lamp voltage Vla in the startup process state and the switching frequency of the switching element Q ₁ 3 can be set as shown in FIG. 3, and when the lamp voltage Vla is low, the switching frequency f
It is possible to prevent the noise from being generated due to the decrease in sw and the audible frequency. The current flowing in the lamp voltage Vla is lower starting process state to the inductor L ₁ I
Since L is above the continuous mode, increases the lamp current Ila in order to shift quickly to a steady lighting state after lamp ignition can also be reduced the peak value of the current IL, prevent saturation of inductor L ₁ be able to.

In the no-load state, the inductor L ₁
Without current flows in, the control signals S ₁ of the PWM circuit 17 is a switching element Q ₂₀ is turned on at predetermined value Toff which is set by the timer circuit 19 changes to the high level (pulse width Ton), it is possible to continue the switching operation of the switching element Q _1. In the steady lighting state, the current IL is shorter than the predetermined value Toff.
Is reduced to zero, so that a zero-cross switching mode is realized.

[0026] In Thus, in the present embodiment, it is possible to reduce the peak value of the current IL even when increasing the lamp current Ila in order to quickly shift to a steady lighting state from the starting process state, the inductor L ₁ Since saturation can be prevented, the maximum rated value of the current of each component can also be reduced. Therefore, the size and cost of the entire apparatus can be reduced. Also, in a steady lighting state and no-load conditions it is possible to realize a zero-cross switching mode as the mode of the current IL, it is possible to reduce the switching losses, such as the switching element Q ₁ and diode D _1.

[0027] In the present embodiment, although the inductor L ₁ provided with the secondary winding N ₂ to detect when the current flowing through the inductor L ₁ IL becomes zero, for example, a diode D ₁ and capacitor C ₁ it may be detected by converting the current flowing through the inductor L ₁ to a voltage by inserting a current detecting resistor between. (Embodiment 2) The basic configuration of this embodiment is substantially the same as that of Embodiment 1, and the configuration of the control circuit 11 is different. Therefore, only the circuit configuration diagram of the control circuit 11 is shown in FIG.

By the way, the off-time of the first embodiment in the switching element Q ₁ preset have predetermined value Toff timer circuit 19 (hereinafter, referred to as OFF time set value Toff) was constant at. On the other hand, the present embodiment is characterized in that an off-time setting circuit 21 for changing the off-time setting value Toff according to the lamp voltage Vla is added when the lamp voltage Vla is low.

In the present embodiment, the off-time setting value Toff of the timer circuit 19 is made variable by the off-time setting circuit 21. The off-time setting circuit 21 sets the off-time setting value Toff in accordance with the lamp voltage Vla. Is changed as shown in FIG. Since the basic configuration and basic operation are substantially the same as those in the first embodiment, a detailed description is omitted. In the present embodiment, the lamp voltage Vla and the switching frequency f
The relationship with sw is as shown in FIG.
FIG. 7 shows the relationship between the current and the lamp current Ila.
In the present embodiment, the off-time set value Toff is set to the lamp voltage V
by changing the lamp voltage Vla.
Is low, the lamp current Ila can be adjusted as shown by the broken line in FIG. Thus, for example, in the case you want to limit the lamp current Ila in the starting process state, when unable to so short account of (substantially equal to the pulse width Ton of the see FIG. 2 (d)) the circuit of the on-time switching element Q ₁ is off time by adjusting the off-time of the switching element Q ₁ by varying the off time set value Toff by the setting circuit 21, it is possible to limit the lamp current Ila. Therefore, the maximum current rating of each component can be reduced.

(Embodiment 3) By the way, in the discharge lamp lighting devices of Embodiments 1 and 2, since the discharge lamp La is DC-lighted, stress is biased to one electrode of the lamp. The present embodiment improves this point.
In the discharge lamp lighting device according to the first or second embodiment,
As shown in FIG. 8, a polarity inversion circuit 22 for alternating current lighting of the discharge lamp La is added between the power conversion circuit 3 and the discharge lamp La. The polarity inversion circuit 22 includes a series circuit of the switching elements Q ₂ and Q _{3 and} a series circuit of the switching elements Q ₄ and Q ₅ , each of which is connected in parallel to the capacitor C ₀ of the power conversion circuit 3.
₂ and Q ₃ and the switching elements Q ₄ and Q ₅
The discharge lamp La is connected between the connection points.

The polarity inversion circuit 22 is shown in FIGS.
As shown in FIG. _Two, Q_FiveIs on
Switching element Q_Three, Q_FourIs off and the switch
Element Q_Two, Q_FiveIs off and switching element Q_Three, Q_Four
Are alternately turned on and low frequencies (for example, several tens Hz to several
(100 Hz). Therefore, the discharge lamp La has a
(E) A lamp of a substantially rectangular wave alternating at a low frequency as shown in (e).
The current Ila flows. In the present embodiment, the discharge lamp La
The lamp current Ila is changed to AC,
In DC lighting as in Embodiment 1 and Embodiment 2,
Solving the problem of biased stress on one electrode
Can be.

In the present embodiment, the lamp current Ila flowing through the discharge lamp La is a rectangular wave. However, the present invention is not limited to the rectangular wave, and the on / off control of the switching elements Q _{2 to} Q ₅ is controlled by the above-described control. It is a matter of course that the lamp current Ila may be, for example, substantially sinusoidal, different from the above. (Embodiment 4) In this embodiment, a circuit having both functions of the power conversion circuit 3 and the polarity inversion circuit 22 in Embodiment 3 is replaced with four switching elements Q ₆ as shown in FIG.
To Q ₉ are those configured by full bridge circuit 27 that bridge connection. In the present embodiment, instead of detecting the current IL flowing through the inductor L _1, detected by the control circuit 11 a current I flowing through the current detection resistor 28 as a voltage of the resistor 28, the control circuit 11 to the voltage On / off control of the switching elements Q _{6 to} Q ₉ is performed based on the switching.

Each of the switching elements Q _{6 to} Q ₉ is controlled by a control signal from the control circuit 11 as shown in FIGS.
As shown in the figure, the switching elements Q ₆ and Q ₉ are switched at high frequency and the switching elements Q ₇ and Q ₈ are turned off, and the switching elements Q ₆ and Q ₉ are turned off and the switching elements Q ₇ and Q ₈ are switched at high frequency. Is alternately repeated at a low frequency (several tens Hz to several hundred Hz). That is, in this embodiment, the substitute switching element Q ₁ and the switching element Q ₂ to Q ₅ in FIG. 8 by the switching element Q ₆ to Q _9.

The switching element Q₆, Q₉Is high lap
During the period of wave switching, switching
Element Q₆, Q₉Is off, the inductor L₁Accumulated in
Energy is released and the inductor L₁→ discharge lamp La
→ Diode D₈→ Smoothing capacitor C₀→ Current detection resistor
Anti-28 → diode D₇→ Inductor L₁Current in the path
Flows (that is, the inductor L₁Energy is smooth
Densa C₀, On the other hand, the switching element Q
₇, Q₈During high-frequency switching
Is the switching element Q₇, Q₈When the inductor is off
L₁The energy stored in the inductor is released and the inductor
L₁→ Diode D₆→ Smoothing capacitor C ₀→ Current detection
Resistor 28 → diode D₉→ discharge lamp La → inductor
L₁Current flows in the path of₁of
Energy is smoothing capacitor C₀Will be returned to). others
The diode D₆~ D₉As a result,
Do D ₁Can be substituted.

In this embodiment, the current detection resistor 2
8 flows through the inductor L₁Current IL flowing through
Since they are the same, the switching element Q
₆~ Q₉Is controlled in the same manner as in the third embodiment.
The lamp La can be turned on by alternating current. Also switch
Element Q₆~ Q₉For example, FET (MOSFE
If T) is adopted, the FET has a parasitic diode.
And the diode D by the parasitic diode of each FET.₆~
D₉And four FETs can be used in the embodiment.
Switching element Q in 3₁, Diode D₁,
Switching element Q _Two~ Q_FiveSubstitute the six elements
Can reduce the number of parts and reduce the cost of the entire system.
Size and size can be reduced.

(Embodiment 5) This embodiment is different from the power conversion circuit 3 and the polarity inversion circuit 2 in the embodiment 3 shown in FIG.
2 has a half bridge circuit 37 having a series circuit of a pair of switching elements Q ₁₀ and Q ₁₁ as shown in FIG. Here, the connection point between the two capacitors C ₀ and C ₀ ′ of the DC power supply circuit 2 and the two switching elements Q
Between the connection point of _10, Q _11, parallel circuit of the discharge lamp La and the capacitor C ₁ through the inductor L ₁ is connected. In this embodiment, an alternating current is supplied to the discharge lamp La by alternately turning on and off the switching elements Q ₁₀ and Q ₁₁ by the control circuit 11. Hereinafter, the operation of the present embodiment will be described with reference to FIG.

The switching elements Q ₁₀ and Q ₁₁ alternately repeat high frequency switching as shown in FIGS. 13 (a) and 13 (b). That is, the switching elements Q ₁₀ , Q
_11, the switching element Q ₁ in FIG. 8, is obtained by substituting switching element Q ₂ to Q _5. In the present embodiment, in a period when the switching element Q ₁₀ is high-frequency switching, when the switching element Q ₁₀ is turned off, energy stored in the inductor L ₁ is released, the inductor L ₁ → discharge lamp La → diode D Current flows through the path of ₁₀ → smoothing capacitor C ₀ → inductor L ₁ (that is, the energy of inductor L ₁ is fed back to smoothing capacitor C ₀ via diode D ₁₀ ). In the period when the switching element Q ₁₁ is a high frequency switching, the OFF of the switching element Q _11, the inductor L
_The energy stored in ₁ is released and the inductor L
₁ → smoothing capacitor C ₀ '→ diode D ₁₁ → discharge lamp L
a → current flows through a path of the inductor L ₁ (i.e., the energy of the inductor L ₁ is fed back to the capacitor C ₀ 'via the diode D _11). Therefore, by the diode D _10, D ₁₁ it is possible to substitute diode D ₁ in FIG.

In this embodiment, similarly to the third and fourth embodiments, an alternating current can be supplied to the discharge lamp La, and the same control as in the third and fourth embodiments can be performed. Also in the present embodiment, if an element having a parasitic diode such as an FET is used for the switching elements Q ₁₀ and Q ₁₁ , the diodes D ₁₀ and D ₁₁ can also be used as the parasitic diodes of the FETs.
In the switching element Q ₁ in the third embodiment, the diode D _1, since the six elements of the switching element Q ₂ to Q ₅ may be substituted, it is possible to lower cost and size.

There is no need to separately connect a diode,
The number of parts can be reduced and the size can be reduced. In the above embodiments, only the case where a high-pressure discharge lamp is used as a load has been described. However, since a fluorescent lamp also has various load states such as preheating and dimming, the same control as in each embodiment is applied. can do.

[0040]

According to the first aspect of the present invention, there is provided a DC power supply circuit having a rectifier circuit for rectifying an AC output of an AC power supply, and a power supply connected to an output terminal of the DC power supply circuit for adjusting and controlling power supplied to a load. A power conversion circuit, wherein the power conversion circuit connects a series circuit of a switching element and a diode having a cathode connected to one end of the switching element between output terminals of the DC power supply circuit, and in parallel with the diode. A power supply to the discharge lamp by connecting a series circuit of an inductor and a capacitor, connecting a discharge lamp as the load in parallel with the capacitor, and turning on and off the switching element at a high frequency to control a switching frequency or on-duty. A control circuit for controlling the discharge lamp in a steady lighting state of the discharge lamp. When the switching element is turned off, the switching element is controlled to turn on when the current flowing through the inductor becomes substantially zero, and in a state other than the steady lighting state of the discharge lamp, a continuous current or a current flowing through the inductor does not become zero. Since the current flowing through the inductor is controlled so as to be a discontinuous current having a quiescent period, it is possible to reduce the switching loss of the switching element and the diode in the steady lighting state, and to perform a state other than the steady lighting state. Since the peak value of the lamp current can be reduced by appropriately changing the current flowing through the inductor to a continuous current or a discontinuous current, the maximum rated value of the current of each component can be reduced, and the overall device can be reduced in size and reduced. This has the effect of enabling cost reduction.

According to a second aspect of the present invention, in the first aspect of the invention, a high-pressure discharge lamp is used as the discharge lamp, and the current flowing through the inductor is continuously increased in a starting process state in which the lamp voltage of the discharge lamp is lower than in a steady lighting state. Since the current is used, there is an effect that the state can be shifted to the steady state immediately after the lamp is turned on. According to a third or sixth aspect of the present invention, in the first or second aspect, a polarity inversion circuit for converting a current flowing through the discharge lamp into an alternating current between the power conversion circuit and the discharge lamp is provided. Since the discharge lamp is provided, the discharge lamp is lit by AC, and it is possible to prevent stress from being biased to one electrode of the lamp as compared with the case of DC lighting.

[Brief description of the drawings]

FIG. 1 shows a first embodiment, in which (a) is a schematic circuit configuration diagram,
(B) is a circuit configuration diagram of a main part.

FIG. 2 is an operation explanatory view of the above.

FIG. 3 is another operation explanatory view of the above.

FIG. 4 is a main part circuit configuration diagram of a second embodiment.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is another operation explanatory view of the above embodiment.

FIG. 7 is another operation explanatory view of the above embodiment.

FIG. 8 is a circuit configuration diagram showing a third embodiment.

FIG. 9 is an operation explanatory view of the above.

FIG. 10 is a circuit configuration diagram showing a fourth embodiment.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is a circuit diagram showing a fifth embodiment.

FIG. 13 is an explanatory diagram of the operation of the above.

FIG. 14 is a schematic block diagram showing a conventional example.

FIG. 15 is a circuit configuration diagram of the above.

FIG. 16 is an operation explanatory view of the above.

FIG. 17 is another operation explanatory view of the above embodiment.

FIG. 18 is another operation explanatory view of the above embodiment.

FIG. 19 is a diagram illustrating another operation of the above.

FIG. 20 is a circuit configuration diagram showing another conventional example.

FIG. 21 is a main part circuit configuration diagram of the above power supply system;

FIG. 22 is an explanatory diagram of the above operation.

FIG. 23 is a diagram illustrating another operation of the above.

FIG. 24 is another operation explanatory view of the above embodiment;

FIG. 25 is another operation explanatory view of the above embodiment.

[Explanation of symbols]

AC AC power supply 2 DC power supply circuit 3 power conversion circuit 11 control circuit La discharge lamp L ₁ inductor Q ₁ switching element C ₀ smoothing capacitor C ₁ capacitor

Continuing on the front page (72) Inventor Hiromitsu Mizukawa 1048 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd.

Claims (6)

[Claims] A DC power supply circuit having a rectifier circuit for rectifying an AC output of an AC power supply; and a power conversion circuit connected to an output terminal of the DC power supply circuit for adjusting and controlling electric power supplied to a load. The power conversion circuit connects a series circuit of a switching element and a diode having a cathode connected to one end of the switching element between an output terminal of the DC power supply circuit and a series circuit of an inductor and a capacitor in parallel with the diode. A control circuit for controlling the power supplied to the discharge lamp by connecting the discharge lamp as the load in parallel with the capacitor, and controlling the switching frequency or on-duty by turning the switching element on and off at a high frequency. And the control circuit turns off the switching element in a steady lighting state of the discharge lamp. Sometimes, when the current flowing through the inductor becomes substantially zero, the switching element is controlled to be turned on, and in a state other than the steady lighting state of the discharge lamp, the current flowing through the inductor flows through the continuous current that does not become zero or flows through the inductor. A discharge lamp lighting device characterized in that the current is controlled so as to be a discontinuous current having an idle period. 2. The method according to claim 1, wherein a high-pressure discharge lamp is used as the discharge lamp, and a current flowing through the inductor is a continuous current in a starting process state in which the lamp voltage of the discharge lamp is lower than in a steady lighting state. Discharge lamp lighting device. 3. The discharge lamp according to claim 1, further comprising a polarity inversion circuit provided between the power conversion circuit and the discharge lamp for converting a current flowing through the discharge lamp into an alternating current. Lighting device. 4. The polarity reversing circuit connects two sets of a series circuit of two switching elements in parallel with an output terminal of a power conversion circuit, and connects a discharge lamp between connection points of the switching elements in each series circuit. The discharge lamp lighting device according to claim 3, wherein: 5. The discharge lamp lighting device according to claim 3, wherein the power conversion circuit and the polarity inversion circuit are configured by a full bridge circuit. 6. The power conversion circuit and the polarity inversion circuit are constituted by a half bridge circuit.
The discharge lamp lighting device as described in the above.