JPH01274390A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To reduce a flickering of a lamp by providing a lamp voltage detecting device to generate the output when the voltage of a discharge lamp exceeds a specific value, and making the first and the second operation periods of a control circuit variable to reduce the first and the second operation periods when the output of the lamp voltage detecting device is generated. CONSTITUTION:While a discharge lamp DL1 is being lighted, a lamp voltage detecting circuit Y detects the lamp voltage VDL and when the value exceeds a specific value, it generates an output, and adds the output to a control circuit X2. The first and the second operation periods of the control circuit 12 are reduced consequently. When a voltage variation to increase the equivalent conductance and to reduce the voltage VDL from the former half to the latter half in the first and the second operation periods respectively resulting from the fact that the voltage VDL exceeds the specific value by the functions of the detecting circuit Y and the control circuit X2, the first and the second operation periods are reduced. As a result, the variation width of the equivalent conductance is reduced, and the variation width of the voltage VDL is also reduced. A flickering of the discharge lamp DL1 when the voltage VDL is increased can be reduced consequently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device for lighting a high-pressure discharge lamp or the like.

[Conventional technology]

Figure 5 shows a circuit diagram of a discharge lamp lighting device that is the basis of this invention, which is a discharge lamp lighting device that includes a full-bridge type inverter circuit, and Figure 6 shows a specific circuit diagram of the main parts of Figure 5. There is.

The discharge lamp lighting device of FIG. 5 includes a DC power source E1, a parallel circuit of a discharge lamp DLI such as a high-pressure discharge lamp, a capacitance element C2 consisting of a capacitor, an inductance element, and a switching element Q1 consisting of a transistor. Q4 are connected in series to form a first closed circuit that allows current to flow in one direction through the discharge lamp DL, and the DC power source E1
For discharge lamp DL, and capacitance element C3
The parallel circuit, the inductance element L1, and the switching elements Qt and Qx consisting of transistors are connected in series to form a second closed circuit that allows current to flow in the other direction through the discharge lamp D L +.

Furthermore, each cycle of the low frequency is divided into a first and a second operating period, and a period of time is set between the first operating period and the second operating period, and between the second operating period and the first operating period, respectively. During the first operating period, the switching element Q1 is operated on and off at a high frequency while the switching element Q2 is kept off, and the switching element Q
s and Q4 are held off and on, respectively, and the switching element Q1 is held off and the switching element Q! is held off during the second operation period. is operated on and off at high frequency, and the switching element Q3. Turn on each Q.

Switching element Q, held off during the rest period.

A control circuit X1 (details shown in FIG. 6) is provided to keep all of Qt, Qx, and Q4 off.

In addition, in FIG. 5, ■ indicates an AC power supply, DB.

is a full-wave rectifier SC+ is a smoothing capacitor, and these constitute a DC power supply El. L is the capacitance element C2
and an inductance element that constitutes a filter circuit, DI
to D4 are diodes, and R+ is a current detection resistor.

In FIG. 6, T is a transformer, T8 and T3 are each a pulse transformer, DBt is a full-wave rectifier, C8 to C4 are each a capacitor, and R.

and RIS are resistors, Ds and Da are diodes, Q, , Q are transistors, and IC1
is a general-purpose switching regulator control integrated circuit (IR
3MO2N; made by Sharp ■), ICz is a general-purpose timer integrated circuit (LB8555M; made by Tokyo Sanyo Electric ■), IC3 is a flip-flop (4013; made by Matsushita Electronic Components),
ICa and ICs are NOR gates. Note that the symbols a to m in FIG. 6 correspond to the symbols a to m in the control circuit X1 in FIG. 5, respectively.

Next, the operation of the discharge lamp lighting device shown in FIGS. 5 and 6 will be explained with reference to FIG. 7.

In this discharge lamp lighting device, the switching elements Q, Qx each switch at a high frequency (for example, about 4QKHz) in response to a drive signal from the control circuit X1, and the switching elements Qs and Qa switch at a low frequency (for example, about 400KHz).
Hz).

In this case, switching element Q is off as shown in FIG. 7 (C1) and switching element Q4 is off as shown in FIG.
When on as shown in l, the switching element Q
, are turned on and off at a high frequency as shown in FIG. 7 la, and the switching element Q3 remains off as shown in FIG. On the other hand, when switching element Q is on as shown in FIG. 7 (C1) and switching element Q4 is off as shown in FIG. 7 (dl),
Switching element Q.

remains off as shown in Figure 7 (al), and
The switching element Q8 turns on and off at high frequency as shown in FIG.
When off as shown in , the switching element Q
+, Q x are both held off as shown in Figure 7 1al, (bl). Note that the switching elements Q,
The pulse width of the QxO high frequency switching is determined by the current flowing through the switching elements Q1 to Q4, that is, the current flowing through the resistor R1, as will be described later.

In the on/off operation of each of the switching elements QI-Q4 as described above, assuming that the switching elements Q + and Q a are in the on state, the resistance R1 gradually increases 'r!' due to the action of the inductance element R! One current flows, and this current generates a voltage across resistor R1. This voltage is input to the 16th terminal of the general-purpose switching regulator control integrated circuit IC, and the error built in the general-purpose switching regulator control integrated circuit IC. Amplified by an amplifier (operational amplifier).

On the other hand, integrated circuit I for general-purpose switching regulator control
C, has a built-in oscillator that generates a sawtooth wave at a period set by a resistor Rt and a capacitor C4 connected to terminals 6 and 5, respectively, and a comparator for pulse width modulation. The output voltage of the amplifier and the sawtooth wave voltage output from the oscillator will be compared by a pulse width modulation comparator. As a result, a pulse width modulated high frequency pulse signal (for example, 40K
)iz) is output from the No. 8 terminal of the general-purpose switching regulator control integrated circuit IC, and the switching element Q is switched by this high-frequency pulse signal, so that the gradually increasing current is interrupted. The details will be described later.

On the other hand, the length of the high-level pulse period TF (corresponding to the above-mentioned operating period) of the low-frequency pulse signal (for example, 400) 1z) for turning on and off the switching element Q4 is determined by the length of the high-level pulse period TF (corresponding to the above-mentioned operating period) It is determined by the resistor Rra and the capacitor C3, and the length of the low-level pulse pause period T (corresponding to the above-mentioned pause period) is determined by the discharge time constant of the capacitor C1 and the resistor RIS.

Then, the above-mentioned low frequency pulse signal is outputted from the third terminal of the general-purpose timer integrated circuit ICt.

The above-mentioned low frequency pulse signal is distributed and outputted to terminal e and terminal f by flip-flop ICz, and is output from terminal e.
, f to the switching elements Qi, Q.

are added to the bases of the transistors, respectively. As a result, switching element Q3. Q4 is as described above in accordance with the low frequency pulse signal in FIG. 7(C).

(It turns on and off as shown in d+.

On the other hand, integrated circuit I for general-purpose switching regulator control
The high frequency pulse signal output from terminals C and 08 is N along with the output signals Q and Q of flip-flop IC1.
It is input to OR gate IC, IC8, and NOR gate I
The output of C4, I C8 is the transistor Q s, Q
h and is added to the base of the transistor which is the switching element Q+, Qz via a pulse transformer T z, T i etc. Therefore, as described above, during the pulse period T when the switching elements Q s and Q a are off and on, the switching element Q turns on and off at high frequency as shown in FIG. Switching element Q2 remains off.Also, switching element Q,.

During the pulse period T during which C4 is on and off, the switching element Q! turns on and off at high frequency, and the switching element Q1 remains off. Also, switching element Q3. Q.

Both switching elements Q + and Q z remain off during the pulse pause period TO when both are off.

The discharge lamp lighting device shown in FIGS. 5 and 6 operates as described above, and currents as shown in FIG. 7 (el, (fl) flow through the switching elements Q1 and C2, respectively,
Capacitance element Ct and inductance element L!
The discharge lamp DL is lit with a rectangular wave due to the filtering action of the discharge lamp DL. At this time, the lamp current rot of the discharge lamp DLI and the lamp voltage VDL of the discharge lamp DLI are shown in FIG.
gl, (as shown in hl, both have a substantially rectangular wave shape.

This discharge lamp lighting device shortens the pulse pause period T, so that when the discharge lamp DL+ is lit, a so-called high restriking voltage does not appear in the lamp voltage VDL of the discharge lamp DL+. There is an advantage that the discharge lamp DL+ is extremely unlikely to go out.

[Problem to be solved by the invention]

In the discharge lamp lighting device described above, the discharge lamp DL.

The lamp current ■1 flowing in Figure 7 (as shown in the illusion,
Since the reversal does not occur abruptly but gradually over a certain period of time, the equivalent conductance of the discharge lamp DL is relatively smaller and later in each half cycle the discharge lamp D
The equivalent conductance of L increases.

Fluctuations in the equivalent conductance of the discharge pump DLI during each half cycle of the lamp current 111L occur, for example, when the voltage of the DC power supply E1 is high, or when the lamp voltage VDL increases due to aging of the discharge lamp DL. The impact is significant. That is, the lamp voltage■. When , is high, the waveform becomes high in the first half of each half cycle and becomes low in the second half, as shown in FIG. 7+11.

The above-described fluctuations (instability) in the lamp voltages v and L sometimes cause the discharge lamp DL to flicker.

The above-mentioned flickering of the discharge lamp DL is caused especially by the DC amount i1! in the circuit of FIG. This was noticeable when there was a ripple in the voltage of smoothing capacitor C3 of E + that was synchronized with the voltage of AC power supply ■1, and when the frequency of lamp current 111L and the frequency of the voltage of AC power supply ■ were asynchronous. .

An object of the present invention is to provide a discharge lamp lighting device that can reduce flickering of a discharge lamp when the lamp voltage is high.

[Means to solve the problem]

The discharge lamp lighting device of the present invention includes a first switching device that connects a discharge lamp and a parallel circuit of a capacitance element, an inductance element, and a first switching element in series to a direct current source to flow current through the discharge lamp in one direction. form a closed circuit,
A parallel circuit of a discharge lamp and a capacitance element, an inductance element, and a second switching element are connected in series to a DC power source to form a second closed circuit that allows current to flow in the other direction through the discharge lamp.

Furthermore, each cycle of the low frequency is divided into a first and a second operating period, and a period of time is set between the first operating period and the second operating period, and between the second operating period and the first operating period, respectively. intervening a rest period, operating the first switching element on and off at high frequency during the first operating period and holding the second switching element off, and holding the first switching element off during the second operating period; At the same time, the second switching element is turned on and off at high frequency.

A control circuit is provided to hold both the first and second switching elements off during the idle period.

Further, the first and second operating periods in the control circuit are configured to be variable, and a lamp voltage detection circuit is provided that generates an output when the lamp voltage of the discharge lamp exceeds a predetermined value. At the time of occurrence, the first and second operation periods are shortened.

[For production]

According to the configuration of the present invention, during the first operation period of each cycle of the low frequency, the control circuit turns on and off the first switching element at the high frequency and holds the second switching element off. As a result, the current flowing through the first closed circuit is interrupted at a high frequency, and no current flows through the second closed circuit.

Further, during the second operation period, the control circuit holds the first switching element off and turns on and off the second switching element at a high frequency. As a result, the current flowing through the second closed circuit is interrupted at high frequency, and no current flows through the first closed circuit.

Also, during the rest period, the control circuit holds both the first and second switching elements off.

As a result, no current flows through both the first and second closed circuits.

As described above, when current flows through the first and second closed circuits, the current continues to flow through the discharge lamp due to the energy stored in the capacitance element even when the first and second switching elements are off. , the lamp current has a low frequency substantially rectangular waveform, and the lamp voltage also has a substantially rectangular waveform.

On the other hand, while the discharge lamp is lit, the lamp voltage detection circuit detects the lamp voltage, and when the value exceeds a predetermined value, it generates an output and applies it to the control circuit. As a result, the control circuit shortens the first and second operating periods.

As a result of the operation of the lamp voltage detection circuit and the control circuit, when the lamp voltage exceeds a predetermined value and a voltage fluctuation occurs that decreases from the first half to the second half of each of the first and second operation periods, Since the first and second operating periods are shortened, the fluctuation range of the lamp voltage is reduced. As a result, flickering of the discharge lamp when the lamp voltage is high is reduced.

〔Example〕

A first embodiment of the present invention will be described based on FIGS. 1 to 3. That is, this discharge lamp lighting device uses a full bridge type inverter circuit, and as shown in Fig. 1, a capacitance element Cz consisting of a discharge lamp DL+ such as a high-pressure discharge lamp and a capacitor is connected in parallel to a DC 11i1E+. A circuit, an inductance element, and switching elements Q, Q, each consisting of a transistor are connected in series to form a first closed circuit that allows current to flow in one direction through the discharge lamp DL, and discharges to the DC power source E1. Lamp D
L, a parallel circuit of capacitance element Ct, an inductance element R, and switching elements Q, , Q3 consisting of transistors are connected in series to form a discharge lamp DL+.
A second closed circuit is formed in which current flows in the other direction.

Furthermore, each cycle of the low frequency is divided into a first and a second operating period, and a period of time is set between the first operating period and the second operating period, and between the second operating period and the first operating period, respectively. During the first operation period, the switching element Q is turned on and off at a high frequency with a rest period intervening, and the switching element Q! is held off and the switching element Q,
, Q4 are held off and on, respectively, the switching element Q is held off and the switching element Q8 is operated on and off at high frequency during the second operation period, and the switching element Q3. Turn on each Q4.

Switching element Cb is held off during the rest period.

A control circuit Xs is provided to keep all of Qi, Qs, and Q4 off.

Furthermore, a lamp voltage detection circuit Y is provided, which configures the first and second operating periods in the control circuit X to be variable, and generates an output when the lamp voltage VDL of the discharge lamp DL exceeds a predetermined value, The first and second operating periods are shortened when the lamp voltage detection circuit Y generates an output.

The other configurations are the same as the discharge lamp lighting device shown in FIG.

Next, the operation of this discharge lamp lighting device will be explained.

In this discharge lamp lighting device, during the first operation period of each cycle of low frequency, the control circuit X2 turns on and off the switching element Q at high frequency and holds the switching element Q2 off, and the switching element Q s , Q
Keep < off and on, respectively. As a result, the current flowing through the first closed circuit is interrupted at a high frequency, and no current flows through the second closed circuit.

During the second operation period, the control circuit X1 holds the switching element Q1 off, turns the switching element Q2 on and off at high frequency, and controls the switching element Q3. Turn on each Q4.

Hold off. As a result, the current flowing through the second closed circuit is interrupted at high frequency, and no current flows through the first closed circuit.

Also, during the rest period, the control circuit X switches the switching elements Q + , Q ! +Keep all Qs, Qa off. As a result, no current flows through both the first and second closed circuits.

As described above, when current flows through the first and second closed circuits, the discharge lamp DL, the switching elements Q+, Q,
, C1, , Q4 are off, the current continues to flow due to the energy stored in the capacitance element C2, so that the lamp current has a low frequency substantially rectangular waveform, and the lamp voltage also has a substantially rectangular waveform.

On the other hand, while the discharge lamp DL is lit, the lamp voltage detection circuit Y detects the lamp voltage VIIL, and when the value exceeds a predetermined value, generates an output and applies it to the control circuit X2. As a result, the control circuit X2 shortens the first and second operation periods.

Such lamp voltage detection circuit Y and control circuit X! As a result of the lamp voltage VDL exceeding the predetermined value due to the operation of
In each of the first and second operating periods, if a voltage fluctuation occurs in which the equivalent conductance of the discharge lamp DL increases and the lamp voltage decreases from the first half to the second half, the first and second operating periods Since it is shortened, the fluctuation range of the equivalent conductance is reduced, and therefore the fluctuation range of the lamp voltage VOt is reduced. As a result, flickering of the discharge lamp DLI when the pump voltage VIIL is high is reduced.

Other operations are similar to those in FIG.

As described above, the lamp voltage detection circuit Y and the control circuit X! shorten the first and second operation periods to prevent flickering of the discharge lamp D L +. Specifically, it has a configuration as shown in FIG.

First, the lamp voltage detection circuit Y includes a detection transformer T4 having a primary S line connected to both ends of the discharge lamp DL, a diode bridge DBS for full-wave rectification of the secondary output of the detection transformer T4, and a diode bridge DBS that performs full-wave rectification of the secondary output of the detection transformer T4. DBs
capacitor Ct and resistor R4, which smooth the output voltage of
R1'? and a Zener diode ZD.

In addition, the control circuit X has a transistor Q? in the resistor RI4 in FIG. and a resistor R1□ are connected in parallel, and the rest is the same as that shown in FIG.

Next, the operation of these circuits will be explained.

The lamp voltage detection circuit Y constantly detects the lamp voltage VDL of the discharge lamp D L +, and a voltage proportional to the amplitude of the lamp voltage VDL appears across the capacitor C1.

Now, when the lamp voltage VDL of the discharge lamp DL exceeds a certain set level, the voltage across the capacitor C1 exceeds the Zener voltage of the Zener diode ZD.

conducts from capacitor C1 to transistor Q.

Supply of base current to is started. As a result, transistor Q? moves to the active region, resistor RI4 and transistor Q? The combined impedance of the parallel circuit with the series circuit of resistor R1° is reduced. If this combined impedance decreases, the pulse period T will be shortened. At this time, the base current supplied to the transistor Q increases as the lamp voltage VDL increases, and the impedance between the emitter and collector of the transistor Q decreases, so the pulse period TP increases as the lamp voltage VDL increases. It will be gradually shortened, and further the first and second operating periods referred to in the claims will be shortened. Note that the transistor Q is
Zener diode ZD.

The circuit constants may be set so that the conduction occurs suddenly when the conduction occurs.

Figure 3 (al to (C) are waveform diagrams of various parts when the lamp voltage VIL is lower than a predetermined value, Figure 3 ta+ shows the on/off state of the switching element Q, and Figure 3) is the switching element Q4. 3 (C1 is the lamp voltage 2 of the discharge lamp DL, and these waveforms are the same as the waveforms of (cl, (di, (hl) in FIG. 7).

Figure 3 +d1~(fl is a waveform diagram of each part when the lamp voltage VDL is higher than a predetermined value, Figure 3 (dl indicates the on/off state of the switching element Q, Figure 3 tel represents the switching element Q, Figure 3 shows the on/off state of
f) shows the waveform of the lamp voltage VOt of the discharge lamp DL.

Other circuit configurations and operations are similar to those in FIG.

The discharge lamp lighting device of this embodiment includes a lamp voltage detection circuit Y that generates an output when the lamp voltage VDL of the discharge lamp DLI exceeds a predetermined value, and a control circuit X8.
The first and second operating periods, that is, the pulse period T, are configured to be variable, and the first and second operating periods are shortened when the output of the lamp voltage detection circuit Y is generated, so that the lamp voltage VIIL is When a voltage fluctuation that decreases from the first half to the second half of each of the first and second operation periods occurs as a result of exceeding the predetermined value, the second operation period occurs.

Since the first and second operating periods are shortened, the lamp voltage ■. , and the flickering of the discharge lamp DLI when the lamp voltage VIIL is high can be reduced.

Furthermore, if the voltage of the capacitor C1 includes ripple, the capacitance of the capacitor C8 that can suppress flickering can be reduced.

In the above embodiment, the length of the pause period is not changed, but it is of course possible to actively change the lamp current flowing through the discharge lamp DL as long as it does not cause a substantial pause period. .

Furthermore, if the first and second operating periods described above are set to be short from the beginning, fluctuations in the lamp voltage VDL can be reduced and flickering of the discharge lamp DLI can be reduced, but the DC power supply E1 In other words, in order to ensure the same brightness of the discharge lamp DL, the switching elements Q+, Qz, C cannot be turned on with sufficient brightness.
The peak value of the current flowing through L, , Qa must be increased, and the switching elements Q , Q z, Q s,
There is the inconvenience of having to increase the rating of Q a.

A second embodiment of the invention will be described based on FIG. 4.

In this embodiment, the present invention is applied to a discharge lamp lighting device using a half-bridge type inverter circuit. As shown in FIG. 4, this discharge lamp lighting device has a DC flow rate dE
In contrast to 2, discharge lamps such as high-pressure discharge lamps DL! and a parallel circuit of a capacitance element CI3 consisting of a capacitor, an inductance element L11, a switching element Q11 consisting of a transistor, and a capacitance element CI! consisting of a capacitor! are connected in series to form a first closed circuit that allows current to flow in one direction through the discharge lamp DLt, and the DC amount aE
! For discharge lamp DLt and capacitance element C
+3 parallel circuit, an inductance element Ll+, a switching element Glut made of a transistor, and a capacitance element C++ made of a capacitor are connected in series to form a second closed circuit that allows current to flow in the other direction to the discharge lamp DL8. .

Furthermore, each cycle of the low frequency is divided into a first and a second operating period, and a period of time is set between the first operating period and the second operating period, and between the second operating period and the first operating period, respectively. intervening a rest period, during the first operation period the switching element Q, 1 is operated on and off at high frequency and the switching element QIX is kept off, and during the second operation period the switching element Qll is kept off and the switching element QI! A control circuit (not shown) is provided to turn on and off the switching elements Q, , Q, at a high frequency and keep both switching elements Q, , Q, off during the rest period.

Further, as in the first embodiment, the first and second operating periods in the control circuit are configured to be variable, and lamp voltage detection is performed to generate an output when the lamp voltage of the discharge lamp exceeds a predetermined value. A circuit is provided to shorten the first and second operating periods when the lamp voltage detection circuit generates an output.

As the control circuit and lamp voltage detection circuit in this embodiment, circuits similar to those shown in FIG. 2 can be used. Note that terminals e and r are not used, and power supply circuit E
2 is composed of an AC power supply v2 and a full-wave rectifier DB.

The discharge lamp lighting device of this embodiment also provides the same effects as those of the previous embodiment.

〔Effect of the invention〕

According to the discharge lamp lighting device of the present invention, a lamp voltage detection circuit that generates an output when the lamp voltage of the discharge lamp exceeds a predetermined value is provided, and the first and second operating periods in the control circuit are variable. As a result of the lamp voltage exceeding a predetermined value,
If a voltage fluctuation occurs that decreases from the first half to the second half of each of the first and second operating periods, the first and second operating periods are shortened, so the fluctuation width of the lamp voltage is reduced, and the lamp Flickering of the discharge lamp when the voltage is high can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a first embodiment of the present invention;
Figure 2 is a specific circuit diagram of the control circuit in Figure 1, and Figure 3 is a specific circuit diagram of the control circuit in Figure 1.
4 is a block diagram showing the configuration of the second embodiment of the present invention, FIG. 5 is a circuit diagram of a discharge lamp lighting device that is the basis of the present invention, and FIG. 6 is a time chart showing the operation of the second embodiment of the present invention. 5 is a specific circuit diagram of the control circuit shown in FIG. 5, and FIG. 7 is a time chart showing the operation of the discharge lamp lighting device shown in FIG. E, ... DC power supply, D L + ... discharge lamp,
C1...Capacitance element, Ll...Inductance element, Q+, Qz...Switching element, X...Control circuit, Y...Lamp voltage detection circuit E, -Repair power supply OL, - Issei Road Lamp C2 - Keybar; 7 tances element Ll - Ingcutance element Ql, C2 --- Switching element x 2 - Control 8 x 2 Fig. 1/E2 /E1 Fig. 5 (.) On/off No. Figure 7

Claims (1)

[Claims] A first closed circuit is provided in which a parallel circuit of a discharge lamp and a capacitance element, an inductance element, and a first switching element are connected in series to a DC power source to flow current through the discharge lamp in one direction. forming a parallel circuit of the discharge lamp and the capacitance element, and connecting the inductance element and the second switching element in series with respect to the DC power supply to cause current to flow in the other direction through the discharge lamp;
forming a closed circuit, dividing each period of the low frequency into a first and second operation period, and between the first operation period and the second operation period and between the second operation period and the first operation. and a rest period is interposed between the periods, and during the first operation period, the first switching element is turned on and off at a high frequency, and the second switching element is held off, and the second operation period is A control circuit is provided that holds the first switching element OFF while operating the second switching element on and off at high frequency, and holds both the first and second switching elements OFF during the rest period. In the discharge lamp lighting device, the first and second operating periods in the control circuit are configured to be variable, and a lamp voltage detection circuit is provided that generates an output when the lamp voltage of the discharge lamp exceeds a predetermined value. . A discharge lamp lighting device, characterized in that the first and second operating periods are shortened when the lamp voltage detection circuit generates an output.