JPH01298697A - Electric-discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce a noise generated in the operation switching of invertor circuits by switching each invertor circuit successively in order of variation rank of the supply capability to an electric-discharge lamp. CONSTITUTION:During operating an invertor circuit 12, switch elements S3 and S4 are turned on/off alternately. When S5 having a parallel relation to S3 is turned on, the switching from the circuit 12 to the circuit 13 is conducted. Similarly, the switching from 13 to 11 is conducted. In a control circuit 10, when both exposure switches SW1, SW2 are turned on, switch elements Q1, Q2 are turned on/off to turn elements S1, S2 on/off through transformers T1, T2. Hence, only the circuit 11 is operated to supply a current to the electric discharge lamp 2 through chokes CH1-CH3. Then, when only SW1 is turned off, only the circuit 13 supplies a current to the electric-discharge lamp 2 through CH1, CH2, and further, when SW2 is also turned off, only the circuit 12 supplies a current to the electric discharge lamp 2 through CH1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a dimmable discharge lamp lighting device.

[Prior Art] Discharge lamp lighting devices that use an inverter circuit are generally provided as discharge lamp lighting devices. In order to enable dimming in a discharge lamp or α lamp circuit using an inverter circuit, the present inventors developed a separately excited inverter circuit 1. as shown in FIG. ．． 1. In addition to using a plurality of inverter circuits 11 and 12, different impedance elements are inserted between the output ends of each inverter circuit 11 and 12 and the discharge lamp 2.
It was proposed to change the power supplied to the discharge lamp 2 and dim it by switching □.

That is, it has two inverter circuits 1 and 11□, each of which is a bar 7 type. are switch elements S and S2 connected in series, and each switch element S
, S2 are connected in parallel to each other, and the inverter circuit 1. Similarly, the switch elements S, , S, and each switch element S, are connected in series.
, S, and diodes D, , D, connected in parallel to each other, and a choke filter as an impedance element is connected between the connection point of the switch elements S, , S2 and the connection point of the switch element S3°S. CH is inserted. Both inverter circuits 11,1. A circuit in which a choke CH and a capacitor C2 are connected in series to a parallel circuit of the discharge lamp 2 and a capacitor C2 is connected as a load. Inverter circuit 1. ．． 12 power supply is AC power supply AC with full wave rectifier D
It is a DC power source rectified by R and smoothed by capacitor C.

The operation of this circuit is as follows. Now, assuming that the inverter circuit 12 is operating and the inverter circuit 1° is not operating, the circuit is equivalent to the circuit shown in PIS 7 (a), and operates as a normal bar 7 type inverter circuit. Here, the impedance z2 of the load when the discharge lamp is lit is expressed by the following equation.

However, ωX is the operating angular frequency of the inverter circuit 12, Ll
is the inductance of the choke CH, Rlm is the lamp impedance when the discharge lamp is lit, and the capacitor C1 is ignored.

Next, inverter circuit 1□ stops operating, and inverter circuit 1. When it operates, it becomes equivalent to the circuit shown in FIG. 7(b). At this time, the load impedance Z1 when the discharge lamp is lit is as shown in the following equation.

However, L is the inductance of the choke coil CH. As is clear from comparing equations ■ and (■), the operating frequency fx of the inverter circuit 1°12 (ωX=2πfx
) are equal, due to the effect of the inductance L, 12.1 > 1221, and the current ■1 to the discharge lamp 2 when the inverter circuit 11 is operating, and the current I2 to the discharge lamp 2 when the inverter circuit 12 is operating The relationship is I,<12. In other words, the power supplied to the discharge lamp 2 can be controlled by selecting whether to operate the inverter circuit 11 or the inverter circuit 12.

Therefore, if the operating time ratio of each inverter circuit 11 and 12 is adjusted within a certain period (for example, a period corresponding to several Hz to 20 AHZ), each inverter circuit 1. ．． 1
It is possible to supply any power to the discharge lamp 2 between the power supplied by the discharge lamp 2.

[Problem to be Solved by the Invention 1] In the above configuration, the lamp current changes with a period T as shown in FIG. A peak current will flow when switching to . Here, the period T generally corresponds to an audio frequency, and since a large current change occurs in the period of the audio frequency, a problem arises in that noise is generated due to vibration of the impedance element. In other words, since the capacitor C2 and the choke coil CH are inserted in the circuit including the discharge lamp 2, the larger the amount of change in the lamp current, the more the peak current that momentarily flows as the inverter circuit switches its operation. When the capacitor C2 is a film-wound capacitor, vibrations occur due to the attraction and repulsion between the films, and as a result, Noise will be generated.

The present invention aims to solve the above-mentioned problems, and provides a discharge lamp lighting device that reduces the noise generated when switching the operation of an inverter circuit.

[Means for Solving the 9 Problems] In the present invention, in order to achieve the above object, three or more inverter circuits are provided, and the operating inverter circuits are arranged in order of decreasing amount of change in power supplied to the discharge lamp. , each inverter circuit is sequentially switched.

[Function] According to the above configuration, the amount of change in the lamp current in one operation switching of the inverter circuit can be made relatively small, and the peak current can be suppressed and noise can be reduced.

[Example] In this example, three inverter circuits 1. Although an example in which the inverter circuits are provided at an angle of ~1° is shown, the present invention is not limited to this, and a larger number of inverter circuits may be provided.

As shown in FIG. 1, each inverter circuit 11-1 is
A pair of switch elements 81 to S6 each connected in series
and diodes D, ~D6 for gunpa connected in parallel to each switch element S, -S, respectively,
Each of the switch elements 81 to S6 is formed of a MOSFET. The conduction of each of the switch elements 81 to S6 is controlled by a control signal inputted via a transformer T, -T, respectively. Inverter circuit 11,1. and between the output terminals of the inverter circuit 12. Choke coils CH, which are impedance elements, are connected between the output terminals of L, respectively.
,CH, are inserted. Each inverter circuit 11-1. are supplied with power from a common ta circuit, and the power supply circuit supplies DC power obtained by smoothing alternating current tIL power AC through a full-wave rectifier DR by smoothing capacitors C2 and C. Further, a noise filter NF is inserted between the AC power supply AC and the gold wave rectifier DR. Inverter circuit 1. At the output end of
A circuit in which these are connected in series is connected.

Next, using FIGS. 3 and 4, inverter circuit 1
1-1. Explain the operation. Figure 3 shows inverter circuit 1
1-1. The switch elements S and -S are expressed using the symbol of a switch. First, consider the case where the inverter circuit 12 is in operation as shown in FIG. 4(a). If the switch element S is on, the positive terminal of the DC power supply → switch element S → capacitor C1 → choke C
Current flows through H+→parallel circuit of discharge lamp 2 and capacitor C2→negative electrode of DC power supply. Switch element S is turned on and off alternately with switch element S4, so when switch element S is on, the charge accumulated in capacitor C7 when switch element S is on is transferred to switch element S → discharge lamp 2 and capacitor C2. Parallel circuit → choke CH
, is discharged through.

Then, the switch element S in parallel with the switch element S is turned on, and as shown in FIG. 4(b), the inverter circuit 12 is connected to the inverter circuit 1. Even if switching is performed, the loop when the switch element S is on is the capacitor C1.
→ Switch element S6 → Discharge lamp 2 and capacitor C2
Parallel circuit → choke CH8 → capacitor CIl (there is no problem in discharging capacitor CI).The same applies when switching from inverter circuit 1 to inverter circuit 1 as shown in Fig. 4(c). perform the following actions.

On the other hand, inverter circuits 11-1. Control circuit 1 that controls
0 has a clock generation circuit 11 and a logic circuit. When both dimmer switches SW, SW2 are turned on, AND circuit A5. Since one input terminal of A2 is connected to the power supply circuit 12, the clock signal from the clock generation circuit 11 is passed through, and the switching elements Q, Q2 made of MOSFETs are turned on and off, thereby turning on the transformer T.
,, a pulse current is passed through the primary side of T2, and this transformer i
' , , the switch element S1. connected to the secondary side of T2. Turn S2 on and off. Here, switch element Q
, , Q are input with clock signals having opposite phases to each other, so as shown in FIGS. 2(a) and (b), the switching element S
1 and S2 are turned on and off alternately. at this point
AND circuits A and A8 prohibit the passage of clock signals. Therefore, only the inverter circuit 11 operates,
Other inverter circuits 1. , L do not operate, and power is supplied to the discharge lamp 2 through the chiroke coils CH, ~CH.Next, when only the dimmer switch SWl is turned off, the AND circuit A5. A, only passes the clock signal, and as shown in FIG. 2 (cHd), the switching elements Q, , Q, are turned on and off alternately, and the inverter circuits 1. Only the choke coils CH, , CH2 supply power to the discharge lamp 2. Furthermore, if the dimmer switch SW2 is also turned off, the AND circuit A
,,A, will now only pass the clock signal,
As shown in FIGS. 2(e) and (f), the switching elements Q, ,Q,
are alternately turned on and off, and only the inverter circuit 12 supplies power to the discharge lamp 2 via the choke coil CH. In this way, by sequentially reducing the impedance elements CH, . . . CH, the discharge lamp 2 is dimmed to increase its brightness. Furthermore, when dimming the light, the operations may be performed in the reverse order to the above order from the state where both the dimmer switches SW, SW2 are turned off. Each inverter circuit II-1. Since the control signal to is given by a single clock signal, as shown in FIG.
Each inverter circuit 11-1. When switching the operation, no phase shift occurs, and each inverter circuit 1, to 13
Since the lamps operate synchronously, there is no problem such as the discharge lamp 2 having a long pause period and turning off. In FIG. 1, T is a step-down transformer for the power supply circuit 12, P is a tjS product circuit for the stabilized Wi source, and output terminals a-r are transformers T, ~T, with the same sign on the primary side. It corresponds to the end. The switches sw, sw2 are actually controlled by a separate control circuit so as to be repeated at a constant cycle (generally an audible frequency), and as shown in FIG. The switching operation is performed so that the values are sequentially increased or decreased sequentially. Therefore, each inverter circuit 11-1. By setting the operating time ratio within one cycle to $'4ffi, the power supplied to the discharge lamp 2 can be adjusted and dimming control can be performed.

According to the above configuration, the inverter circuit 1. If the amount of light adjustment between the inverter circuit 1. and the inverter circuit 12 is the same as the conventional configuration shown in FIG. As a result, as shown in FIG. 5, the amount of change in the lamp current in one stage of switching becomes smaller than in the previous case, and as a result, the inverter circuits 11 to 11.
1. This makes it possible to suppress the peak current that occurs when switching operations, and to reduce the generation of noise.

[Effect of the invention 1] As described above, the present invention provides three or more inverter circuits, and sequentially switches and operates each inverter circuit in descending order of the amount of change in power supplied to the discharge lamp for the inverter circuits in operation. This makes it possible to make the amount of change in lamp current relatively small during one operation switching of the inverter circuit, and to suppress the peak current. As a result, it has the advantage that the noise generated from the resonant element can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of the same as above, Fig. 3 is a basic configuration diagram of the same as above, and Fig. 4 is a configuration diagram showing the operating state of each inverter circuit in the same as above. , Fig. 5 is an explanatory diagram of the same operation as above, Fig. 6 is a circuit diagram showing a conventional example, Fig. 7 is a configuration diagram showing the operating state of each inverter circuit of the above, and Figure 8 is an explanatory diagram of the operation of the same as above. . 11-1. ...Inverter circuit, 2...Discharge lamp, 1
0...Control circuit, CHI...Choke coil. Agent Patent Attorney 5 [B] Figure 2 Figure 3 Figure 7 (a) (b) Figure 8

Claims (1)

[Claims] (1) A plurality of separately excited inverter circuits, a plurality of impedance elements that limit the current supplied from each inverter circuit to the discharge lamp and vary the power supplied from each inverter circuit to the discharge lamp, and a predetermined period. In a discharge lamp lighting device, the discharge lamp lighting device is equipped with a control unit that adjusts the operating time ratio of each inverter circuit within the inverter circuit to obtain a desired dimming amount, in which three or more inverter circuits are provided, and the control unit In descending order of the amount of change in power supplied to the discharge lamp relative to the circuit:
A discharge lamp lighting device characterized by sequentially switching and operating each inverter circuit.