JPH04181695A - Lighting device for discharge lamp - Google Patents

Abstract

PURPOSE:To prevent a detecting means from being operated as the current limiting element of a discharge lamp by forming the portion inserted into a current feeding loop in a lighting device with a circuit detecting and controlling the discharge lamp current. CONSTITUTION:A control circuit 1 is constituted with a comparator CP and a mono-stable multivibrator IC1 and the like. The power voltage E1 which can maintain the lighting of a discharge lamp 1a is applied to a serial circuit of the discharge lamp 1a, a switching element SW1 and a transistor Q1 detecting the current I1a. Transistors Q1, Q2 constitute a current mirror circuit the collector of Q2 is connected to a control power source VDD via a current detecting resistor R and connected to the input terminal of the control circuit 1 of the next stage. The current limiting effect of the transistor Q1 is negligible, the discharge lamp 1a can stably be lighted by only the switching of the element SW1, and the loss at a detection section can remarkably be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention relates to a discharge lamp lighting device that detects a switching state in a control system that supplies high-frequency energy from a power source to a discharge lamp via a switching element. It is something.

[Prior Art] Conventionally, in a circuit that supplies a regulated pulse current to a discharge lamp by switching, an example of a means for detecting a switching state is shown in FIG. 15. This turns the discharge lamp t'a on and off by turning on and off the switching element SW.
A change in the current flowing through the discharge lamp is detected as a voltage value by a resistance element Rs inserted in series in a discharge lamp current loop composed of a power supply E, a discharge lamp Za, and a switching element SWl. Based on this voltage value, the peak value of the current flowing through the discharge lamp 1a is limited to a constant value, and the discharge lamp current is controlled.

FIG. 16 shows operating waveforms of the conventional example shown in FIG. 15, and the operation will be explained below. Discharge lamp/a and s(
= Current Tl flowing through switching element SW1 and discharge lamp pa
A voltage higher than the voltage at which the discharge lamp la can be kept lit is applied by the power source E1 to the resistor Fjs for detecting a and the force surface array circuit. When the discharge lamp 1a is in a state where it can be re-ignited, time t0
When the switching element SWl is turned on, the discharge lamp la, the switching element SW1, the resistance Rs
A current Ila flows as shown in FIG. 16(a). Then, the resistor Rs has Rsn T corresponding to the current It'a.
A voltage ea is generated.

This voltage Vs (Fig. 16(b)) is applied via the resistor R1 as follows.
It is applied to one input terminal V- of the comparator CP.

When @riLIla increases and the voltage VS exceeds the reference voltage Vr applied to the other input terminal V+ of the comparator CP at time t, the output voltage V1 of the comparator CP becomes as shown in FIG. 16(C). , from H level to L
change to the level.

The fall of this voltage V is the monostable multivibrator (hereinafter referred to as monostable multi).
38 I() terminal). Monostable multi IC1 is
Due to the fall of the trigger terminal, the output terminal 0 becomes H level as shown in Figure 16(d), and in response to this, the output of the switching element SW1 is inverted and the output of the IC+ becomes H level as shown in Figure 16(e). ), the monostable multi I
C, maintains the H level for a period set by the capacitor C3 and the resistor R6, and switches the switching element S until time t2.
W1 is turned off.

At time t2, the output terminal 0 of the monostable multi-IC returns to the L level, so the switching element SW1 is turned on again and the current IZa begins to flow. By repeating the above operation, a current of a constant peak value flows through the discharge lamp 1a at constant time intervals.

FIG. 17 shows another conventional example, and FIG. 18 shows its operating waveforms. This conventional example uses a current transformer CT instead of the current detection resistor Rs of the conventional example shown in FIG. When the discharge lamp fa is in the re-ignition possible state, when the switching element SW1 is turned on at time 1u, the discharge lamp t'a and the switching element SW1.
A current I[a flows through the primary winding of the current transformer CT as shown in FIG. 18(a). Current transformer C
In the secondary winding of T, as shown in FIG. 18(b), there is a current t proportional to the current in the same direction as the current 11a. Since a flows, as shown in FIG. 18(c), as Vs, ■. .

-R6XIcy voltage is generated. This voltage Vs is
It is applied to the input terminal V+ of the comparator CP via the resistor R,.

When the current 11a increases and the voltage Vs falls below the reference voltage Vr applied to the other input terminal - of the comparator CP at time t1, the output voltage of the comparator CP decreases as shown in FIG. 18(d). V, from H level to L
change to the level.

The fall of this voltage ■I is received by the trigger terminal of the monostable multi-IC. In a monostable multi-IC, the output terminal 0 becomes H level as shown in Fig. 18(e) due to the fall of the trigger terminal, and in response to this, the switching element SW
1 drive inverting buffer IC.

The output becomes a level as shown in FIG. 18(f), and the switching element SW1 is turned off. Sheep stable multi I
(:1 maintains the H level for a period set by the capacitor C2 and the resistor R7, and the switching element SWt is turned off until time t2. At time t2, the monostable multi-■C1 returns to the L level, so the switching element SWt S W +
is turned on again and current INa begins to flow. By repeating the above operations, a current of a constant peak value flows through the discharge lamp 1a at constant time intervals.

[Problems to be Solved by the Invention] However, in the circuit shown in the conventional example above, a current detection resistor or a current transformer is inserted in series with the discharge lamp current, so these have a current-limiting effect or phase that limits the discharge lamp current. This has the effect of changing the current of the discharge lamp, causing problems such as an increase in loss and a delay in the phase of the detection signal.

The present invention has been provided in view of the above-mentioned points, and an object of the present invention is to provide a discharge lamp lighting device including a switching state detection means that does not function as a current limiting element of the discharge lamp.

[Means for Solving the Problems] The present invention provides a discharge lamp and a switching element for switching the discharge lamp, which are connected in parallel with a discharge lamp lighting power source having a voltage higher than that which can keep the discharge lamp lit.

In a discharge lamp lighting device comprising a control circuit connected in series with a detection means for detecting a discharge lamp current and supplying energy to the discharge lamp by controlling switching of a switching element by the output of the detection means, the discharge lamp of the detection means is connected in series. The part inserted into the loop through which current flows is a semiconductor element.

Further, the detection means is constituted by a current mirror circuit, and the circuit configuration is such that an output corresponding to the discharge lamp current is generated outside the loop through which the discharge lamp current flows.

Furthermore, the detection means is a circuit that can take out a part of the discharge lamp current outside the loop through which the discharge lamp current flows.

[Function] Therefore, since the portion of the detection means inserted into the loop through which the discharge lamp current flows is a semiconductor element, the voltage effect in the semiconductor element is small and the effect of stabilizing the discharge lamp by sowing is small. Compared to this, the current limiting effect in the detection means can be made extremely small, and no phase difference will occur.

[Example 1] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a specific circuit diagram, and FIG. 2 shows an operating waveform diagram. Comparator CP and monostable multi-IC as before
, etc., and transistors Q, , Q2, etc. are added compared to the conventional one.In this embodiment, the discharge lamp la
The discharge lamp 1a, the switching element SW and the discharge lamp 1
It is applied to a series circuit with a transistor Q that detects the current 11a flowing through the current 11a.

the base of transistor Q, and the other transistor Q2
is connected to the base of transistor Q,
, Q2 have their respective emitters grounded. Furthermore, the bases of transistors Q, , Q2 are connected to the collector of transistor Q, forming a current mirror circuit. The collector of the transistor Q2 is connected to the control power supply Vno via a current detection resistor Rt, and is further connected to the input terminal of the control circuit 1 at the next stage.

The circuit of this embodiment operates as follows. When the discharge lamp la is in a state where it can be re-ignited, a time t occurs. When the switching element SW is turned on, as shown in FIG. 2(a),
A discharge lamp current la flows through the transistor Q. Transistors Q and Q2 are transistors manufactured under the same conditions, and their emitter area ratio is Q 2 / Q l =
1/N, a current of approximately Ila/N flows through the emitter of transistor Q2 due to the current mirror circuit (however, hfe of transistors Q, ,Q,
is large and the base current is negligibly small compared to the collector current).

Then, I 2x R? is generated between both ends of the resistor R1 due to the collector current 2 shown in FIG. 2(b). A voltage drop occurs,
The voltage Vs at the input terminal ■+ of the comparator CP connected to the collector of the transistor Q2 via the resistor R is the voltage ■ of the control power supply. . It goes down from As the current IZa increases and at time t1, as shown in FIG. 2(C), when the voltage Vs falls below the reference voltage Vr applied to the other input terminal V- of the comparator CP, the output of the comparator CP The voltage ■ is at the H level as shown in Figure 2 (d).

change to the level.

When the trigger terminal of the monostable multi-IC receives this first fall of voltage ■, the output terminal O becomes H level as shown in Fig. 2 (e), and in response, the switching element S
The output of the inverting buffer IC2 for driving W1 is shown in Figure 2 (f).
As shown in the figure, the level becomes L level, and the switching element SW1
is turned off. Monostable multi IC, capacitor CI,
The H level is maintained for the time set by resistor R9, and the time t
Since the monostable multi-IC returns to the L level at time t2 when the switching element SW is turned off up to 2,
The switching element SW is turned on again, and the current 11a begins to flow. By repeating the above operations, the discharge lamp 1a
, a stream with a constant peak value flows at constant time intervals.

The transistor Q1 connected in series with the discharge lamp fa and the switching element SW1 is connected to the switching element SW1.
There is a voltage drop of about 0.7V when + is on, but its current limiting effect is negligible, and the switching element S
It is possible to stably light the discharge lamp 1a only by switching W, and the loss in the detection part can be significantly reduced compared to the conventional detection using a resistor etc. .

Furthermore, the transistor Q constituting the current mirror circuit is
Even if Q is not a transistor manufactured under the same conditions, a voltage proportional to the current flowing through the transistor Q1 can be obtained across the resistor R1, for example, hfe.
Any combination of transistors may be used. Furthermore, the transistors Q1 and Q2 are not limited to bipolar transistors, but may also be MOSFETs or the like.

[Example 21 Example 2 is shown in FIG. 3, and its operating waveforms are shown in FIG. 4. In this embodiment, the discharge lamp t'a and the transistor Q, which also serves as a switching function and detects the current IZa flowing through the discharge lamp La, are connected to the discharge lamp t'a by a power supply E1 having a voltage equal to or higher than the voltage at which the discharge lamp RA can be maintained lit. It is applied to a series circuit with.

the base of transistor Q, and the other transistor Q2
is connected to the base of transistor Q,
, Q2 have their respective emitters grounded. Furthermore, transistor Q1. The base of Qz is connected to the collector of transistor Q1 via switch element SWs, forming a current mirror circuit. The switch element SW5 is connected to the output terminal of the inverting buffer IC2 of the control circuit 1, and is turned on and off by the voltage of the inverting buffer TC2.

The circuit of this embodiment operates as follows. When the discharge lamp 1a is in the state where it can be re-ignited, when the switch element S W s is turned on at time t0, the transistor Q1. The base of Q2 is connected to the collector of transistor Q1, and as shown in FIG. 4(a), the base voltage of transistor Q2 is
ゎ rises, transistor Q1 turns on, and as shown in Fig. 4<a)
As shown in the figure, a discharge lamp current 11a flows through the transistor Q. Since transistors Q1 and Q2 form a current mirror circuit, current I flowing through transistor Q
A current proportional to la flows through transistor Q2.

Then, due to the collector current I2 shown in FIG. 4(C), a voltage drop of Ix:<R7 occurs across the resistor R1.
The voltage Vs at the input terminal ■+ of the comparator CP connected to the collector of the transistor Q2 via the resistor R1 is a current 11a which decreases from the voltage V0° of the control power supply.
increases, and at time t, the voltage Vs changes to the other input terminal V- of the comparator CP, as shown in FIG.
When the output voltage V1 of the comparator CP becomes lower than the reference voltage Vr applied to the reference voltage Vr, the output voltage V1 of the comparator CP changes from the H level to the L level as shown in FIG. 4(e).

When the trigger terminal of the monostable multi-IC+ receives the fall of this voltage ■1, the output terminal 0 becomes H level as shown in Fig. 4(f), and in response, the switch/I chip element S
W, f) The output of the driving inverting buffer IC2 is shown in Figure 4 (
It becomes L level as shown in g).

Switch element SW is turned off. The monostable multi IC3 maintains the H level for the time set by the capacitor C1 and the resistor 87, and the switch element SW is turned off until time t2.At time t2, the monostable multi IC3 returns to the L level, so the switch Element SW is turned on again and current Ifa begins to flow.

By repeating the above operation, a current of a constant peak value flows through the discharge lamp 1a at constant time intervals.

Incidentally, as an example of the switch element SW, there is a method using a transistor as shown in FIG. Also, MOSFET
Needless to say, it is also possible to use the following. Furthermore, a switch that turns on and off in a complementary manner to the switch element SW may be provided between the base and emitter of the transistor Q1 to ensure reliable operation.

[Example 3] Example 3 is shown in FIG. 6, and FIG. 7 is an operation waveform diagram thereof. In this embodiment, a second switching element sw2 is connected in parallel with a switching element SWl that directly switches the current It'a flowing through the discharge lamp eit.
The discharge lamp ea is connected to a train of switching elements sw, , sw2, and the source of the switching element SW is tJ.
Connected to the ground side of E. Switching element SW2
The source of is connected to the source of the switching element SW1 via a current detection resistor R6. The gates of the switching elements sw, , sw2 are connected to an inverting buffer r in parallel.
Connected to C2. Here, the switching element SW
,, SW2 is, for example, a power M with a 5ENS terminal.
It is a part of O3FET (IRC740 etc.).

Normally, a power MO3FET is a large number of small vertical MO3FETs fabricated on the same chip and connected in parallel, but the characteristics of these small MO3FETs are almost the same, and if the same current flows through each MO8FET, You can think of a power MO3FET with a 5ENS terminal in which the source electrode of some of these small MO5FETs is taken out separately from the main source electrode, and a part of the main current is taken out! ), this corresponds to the switching element SW2. The number of small MO3FETs of the switching element SW1 is sufficiently larger than the number of small MO5FETs of the switching element SW2, and most of the current 11a is connected to the switching elements SW and pfL.

The switching element SW2 includes a switching element SW
Since a small portion of current proportional to the current flowing through + flows, this is detected by resistor R8.

The operation of this embodiment will be explained below. When the discharge lamp ra is in the state where it can be re-ignited, when the switching elements sw, , sw2 are turned on at time 0, a discharge lamp current Ila flows to the switching element SW, as shown in FIG. 7(a). Then, a small portion of the current 2 proportional to the current Ila flows through the switching element SW2 as shown in FIG. 7(b).

Then, a voltage drop of 12XR occurs across the resistor R8 due to the current I2 shown in FIG. 7(b), and the voltage Vs at the input terminal V- of the comparator CP connected to the drain of the switching element SW2 via the resistor R3. is Figure 7(c)
rise as shown in . The current lea increases at time t,
As shown in FIG. 7(), when the voltage Vs rises above the reference voltage Vr applied to the input terminal V+ of the comparator (the other f of p), the output voltage V1 of the comparator CP increases as shown in FIG. As shown in d), it changes from H level to L level.

Upon receiving the fall of this voltage V at the trigger terminal of the monostable multi-IC 8, the output terminal 0 becomes H level as shown in Fig. 7 (e), and in response, the switching element S
The output of the inverting buffer IC2 for driving W1 is shown in Figure 7(f).
As shown in , it becomes L level, and the switching element sw,
, sw2 is turned off.

The monostable multi-IC keeps the H level for a time set by the capacitor C8 and the resistor R6, and the switching element SW1.8w2 is turned off until time t2.

At time t, the monostable multi-IC returns to the L level, so switching elements SW+ and SW2 are turned on again, and current 11a begins to flow. By repeating the above operation, a current of a constant peak value flows through the discharge lamp la at constant time intervals.

Also in this third embodiment, since most of the current rla flows through the switching element swl, there is almost no current limiting effect in the current detection circuit.

[Example 4.5] Figure 8 shows Example 4, and Figure 9 shows Example 5.
a2 are connected in series and have the same effect.

[Example 6] Example 6 is shown in FIG. 10. This example is a discharge lamp ff1.
a,,! az are connected in parallel, but the feature is that the current detection means and the control circuit can be integrated into one by alternately operating the switching elements SW+ and SW3.

The operation of this embodiment will be explained below. timer circuit IC,
, resistance R,,R,. , R, , output signal V of the astable multivibrator circuit composed of capacitor c2
41 and V, 2 (FIG. 11(e), (f)) are in a complementary relationship, and when one is at H level, the other is at L level.

Now, at time i'l t , as shown in FIG. 11(e), the output voltage V□ of the timer cycle n' r C2 becomes L level, and at the same time, the output voltage v2 of the monostable multi-IC
becomes L level as shown in FIG. 11(d).

At this time, the output V51 of the OR gate G1 is as shown in FIG.
), it becomes L level, and the switching element S
WI is turned on and a discharge lamp current 11a flows through the discharge lamp 1a. At this time, the output voltage V42 via the inverter G3
simultaneously becomes L level, as shown in FIG. 11(f). At this time, the output V51 of the OR gate GL becomes L level, the switching element SW1 is turned on, and the discharge lamp is turned on! a
, a current I la flows through .

At this time, the output voltage V42 of the inverter G is at H level because of the complementary relationship as described above, and the output voltage V52 of the OR gate G2 is as shown in FIG. 11(i) regardless of the value of the voltage 2. The current I Za+ increases in the same way as shown in Example 1, and when reaching time t1, the voltage v2 becomes the H level as shown in FIG. 11(d). After the set time of monostable multi-IC5 has elapsed, time t
2, the voltage V2 goes to the L level and at the same time the timer circuit IC2 output is also inverted, and the voltage 41 becomes as shown in Fig. 11<e
), it becomes H level. Therefore, the voltage V 5
, maintains the H level even if the voltage V2 goes to the L level, and the switching element SWl remains off.

On the other hand, as shown in FIG. 11(f), the voltage V,2 becomes the L level at time t2, and the voltage 2 becomes the L level, so the voltage V52 becomes the L level, and the switching element S
Double turns on. Therefore, t a I la t increases, and similarly at time t, the voltage 2 becomes H level as shown in FIG. 11(d), and after the set time of the monostable multi IC , the voltage v2 becomes L level. At this time, the voltage V4+ becomes L level again, as shown in FIG. 11(e), and the same operation is repeated.

As described above, the switching elements SW and SW x are 1
The discharge lamp l
It becomes possible to operate a and la2 alternately. In addition, in this example, monostable multi ((.

Although the explanation has been given by synchronizing the set time of , and the timer time of the timer circuit IC2, even if these times are not synchronized, the switching elements SW and SW operate alternately and exhibit the same effect.

[Example 7] FIG. 12 shows Example 7, in which AC t II was used as the power source.
The feature is that v Ac is applied. In this example,
Depending on the direction of current flow, there are two sets of switching control circuits 3 consisting of a control circuit 1, a detection circuit, a switching circuit, etc.
4, it is possible to realize a detection circuit that does not have a current limiting effect in an AC circuit.

Example 8] FIG. 13 shows Example 8, and this example is applied to a half-bridge circuit, using the switching control circuit 3.4 shown in FIG. By alternately turning on the timing control circuit 5, AC power is supplied to the discharge lamp la.

[Embodiment 9] FIG. 14 shows Embodiment 9. This embodiment is applied to a full bridge circuit, and is characterized in that only one detection circuit and one control circuit are required. The control circuit 1 supplies AC power to the discharge lamp 1a by alternately driving the switching elements SW, SW1, SW2 and SW.

In the first to ninth embodiments described above, the detection circuit may be inserted at any position within the path through which the discharge lamp current flows. Furthermore, as the current detection element, a PNP transistor, MOS FET, etc. may be used in place of the NPN transistor, and the same effect can be obtained by using a pulsating current power supply, a pulsed power supply, etc. instead of the DC current REI. It will be done. Further, although an example of a control circuit that maintains the peak value of the discharge lamp current constant has been shown, similar effects can be obtained with other systems.

[Effects of the Invention] As described above, the present invention provides a discharge lamp and a switching element for switching the discharge lamp in parallel with a discharge lamp lighting power source having a voltage higher than that for maintaining lighting of the discharge lamp. and a detection means for detecting the discharge lamp current are connected in series, and the output of the detection means controls the switching of a switching element to supply energy to the discharge lamp. Since the portion of the means inserted into the loop through which the discharge lamp current flows is a semiconductor element, the voltage effect on the semiconductor element is small;
Compared to the effect of stabilizing the discharge lamp by switching, the current limiting effect in the detection means can be made extremely small, and no phase difference can be caused, which has the effect of stably lighting the discharge lamp. be.

It is interesting to note that the above-mentioned detection means is constituted by a current mirror circuit, and has a circuit configuration that generates an output according to the discharge lamp current outside the loop in which the discharge lamp current flows; By making it a circuit that can be taken out of the loop where the discharge lamp current flows, the voltage effect is small, and compared to the effect of stabilizing the discharge lamp by switching, the current limiting effect in the detection means can be extremely small, and no phase difference occurs. This enables stable lighting of the discharge lamp. It is possible to do two things.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of an embodiment of the present invention, Figure 2 is an operational waveform diagram of the same as above, Figure 3 is a circuit diagram of Example 2 of the same as above, Figure 4 is an operational waveform diagram of the same as above, and Figure 5 is A specific circuit diagram as above, FIG. 6 is a circuit diagram of Example 3 as above, FIG. 7 is an operation waveform diagram as above,
8 is a circuit diagram of the fourth embodiment, FIG. 9 is a circuit diagram of the fifth embodiment, FIG. 10 is a circuit diagram of the sixth embodiment, and FIG. 11 is an operation waveform diagram of the same example. Figure 12 is Example 7 of the same as above.
Figure 13 is the circuit diagram of Example 8, and Figure 14 is the circuit diagram of Example 8.
15 is a circuit diagram of the conventional example, FIG. 16 is an operating waveform diagram of the same as above, FIG. 17 is a circuit diagram of another conventional example, and FIG. 18 is an operating waveform diagram of the same as above. It is. 1 is the control circuit, EI is the DC power supply, la is the discharge lamp, SW
+ is a switching element. 1...Control circuit El...DC power supply la...Discharge lamp SWI...Switching element 1m+111 Fig. 2 113WJ Fig. 4 m5 section Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 12 Diagram 13, 14, 15, 16, 17, old diagram procedural amendment (voluntary) December 28, 1990

Claims (3)

[Claims] (1) A discharge lamp, a switching element for switching the discharge lamp, and a detection means for detecting the discharge lamp current are connected in series in parallel with a discharge lamp lighting power supply having a voltage higher than that which can keep the discharge lamp lit. , in a discharge lamp lighting device comprising a control circuit that supplies energy to the discharge lamp by controlling the switching of a switching element by the output of the detection means, a portion of the detection means inserted into the loop through which the discharge lamp current flows is a semiconductor element. A discharge lamp lighting device characterized by: (2) The discharge lamp lighting device according to claim 1, wherein the detection means is constituted by a current mirror circuit, and has a circuit configuration that generates an output according to the discharge lamp current outside the loop in which the discharge lamp current flows. . (3) The discharge lamp lighting device according to claim 1, wherein the detection means is a circuit that allows a part of the discharge lamp current to be taken out of the loop through which the discharge lamp current flows.