JPS63175397A - Discharge lamp lighter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a discharge lamp lighting device for lighting a discharge lamp using a separately excited current resonance type inverter circuit.

(Background Art) FIG. 5 is a circuit diagram showing the basic configuration of a discharge lamp lighting device using an inverter circuit. A series circuit of switching elements Q, Q2 and a capacitor CI are connected to both ends of the DC power supply E.
+CI' series circuit is connected in parallel. Diodes D, D2 are connected in antiparallel to the switching elements Q, Q2, respectively. Switching element Q 1.
A load circuit is connected between the connection point of Qt and the connection point of capacitors C+ and C+'. As a load circuit, a series circuit of a discharge lamp L with a preheating capacitor C2 connected in parallel and an inductance L is connected to the non-power supply side, and this load circuit is generally designed to exhibit inductive reactance. . The capacitor C2 and inductance L connected to the non-power side of the discharge lamp l are L.
Configure a C resonance circuit, and use this resonance circuit to connect the discharge lamp P.
A high voltage is generated across the lamp to start and keep the discharge lamp lit.

BACKGROUND ART Conventionally, when lighting a discharge lamp, a method has been widely used in which the filaments 1- at both poles are sufficiently preheated and then a high voltage is applied to light them, in order to extend the life of the discharge lamp. In this conventional example, as shown in FIG. 6(a), the inverter circuit is oscillated at the frequency f1 during the preheating time L1, and the voltage Vc2 across the capacitor C2 is lowered to below the lighting voltage. After the preheating time L1 has elapsed, the inverter circuit is oscillated at the frequency f2, and the voltage across the capacitor C2 is raised to ■. 2
is set higher than the lighting voltage to start the discharge lamp l.

FIG. 6(b) shows the current raw flowing through the capacitor C2, and FIG. 6(c) shows the current 11 flowing through the discharge lamp l. The figure (d) shows the preheating time 1. , which shows the waveform of the current flowing through the switching element, and (e) of the same figure shows the time t2 from when a high voltage is applied until the discharge lamp l lights up.
2 shows the current waveform flowing through the switching element. Furthermore, FIG. 2(f) shows a current waveform flowing through the switching element after the discharge lamp 1 is turned on. Same figure (
g) shows the relationship between the voltage vc2 generated across the capacitor C2 and the oscillation frequency f.As shown in FIG. 6(a), after the preheating time has elapsed, the frequency changes from fl to f2. change. At this time, in order to generate a high voltage in capacitor C2, the oscillation frequency f2
is often set lower than the natural oscillation frequency f0 of the inductance L and capacitor C2.Furthermore, in order to obtain a predetermined discharge lamp current when the lamp is lit, f2<f.

In this case, between the time the frequency is switched and the discharge lamp 1 turns on,
Although it is for a short time t2, a phase-advanced current as shown in FIG. 4(e) flows through the switching element, and a surge current in the simultaneous ON state flows. Particularly when the power supply voltage E is low, the effective value of the current is large and the surge current is also large, causing problems such as exceeding the ASO area (safe operating area) of the switching element.

Therefore, conventionally, a circuit as shown in FIG. 7 has been proposed. The details of this circuit will be described later, but as the charging voltage of the integrating capacitor C4 increases, the oscillation frequency f of the inverter circuit changes from the preheating wave number f to the lighting frequency r2.
It is designed to smoothly change up to. For a certain period of time after the power is turned on, the transistor Q is turned on by the output of the timer circuit 4, and the resistor R2 is connected across the capacitor C1, so the voltage of the capacitor C4 is at a low level. The oscillation frequency of the inverter circuit at this time is the preheating current wave number f1. When the timer moment flt+ of the timer circuit 4 elapses, the transistor Q.

is turned off, capacitor C4 is connected to I transistor Q3.
The voltage is charged through a current limiting element consisting of a resistor R2, and the charging voltage gradually increases. As the charging voltage of the capacitor C1 increases, the oscillation frequency of the inverter circuit gradually increases, and finally reaches the lighting frequency f2.

FIG. 8(a) shows the relationship between the temporal change in the oscillation frequency f and the voltage across the capacitor VC, · in the circuit of FIG. The oscillation frequency f is fixed at the frequency f1 during the preheating time t, and the filament of the discharge lamp l is sufficiently preheated in this state, so the discharge lamp life is not impaired. In the case of preheating frequency f,
Since the resonance point f0 is included between the frequency f2 and the frequency f2 at the time of lighting, the light is turned on with the same current waveform as the slow mode current waveform flowing through the switching element at the frequency fI,
The phase advance mode current stops flowing. In addition, Fig. 8(b)
, (c) show temporal changes in the current IC2 flowing through the capacitor C2 and the current 11 flowing through the discharge lamp l, respectively.

By the way, when a discharge lamp reaches the end of its life, it may cause half-wave discharge or stop lighting before the filament breaks. In such a state, the equivalent resistance of the discharge lamp increases, so the degree of resonance deepens, the current in the switching element enters a phase advance mode, its peak value increases, and the stress on the switching element increases. However, if this state continues for a long time, the switching element Q1. The problem arises that Q2 is destroyed.

Therefore, in the circuit shown in FIG. 7, an overcurrent flowing through the switching element Q2 is detected at the end of the life of the discharge lamp l, and when an overcurrent exceeding a predetermined level is detected, the timer circuit 4 is reset and the transistor Q5 is turned on. By discharging the integrating capacitor C4 via the resistor R1, the oscillation frequency of the inverter circuit is returned to the preheating local wave number f1. Then, the timer circuit 4's timer 1 hour 1. When , the transistor Q is turned off again and the integrating capacitor C1 is gradually charged via the resistor R6, thereby smoothly changing the oscillation frequency of the inverter circuit to the lighting frequency. Thereafter, as the overcurrent at the end of the discharge lamp life is detected again, the same operation is repeated and the oscillation frequency of the inverter circuit changes as shown in FIG. 9. As a result, the discharge lamp l alternately cycles between the lighting state and the preheating state, and its output luminous flux blinks to notify the user that the discharge lamp is at the end of its lifespan, so that the power can be cut off before the circuit is damaged. ing.

However, in this method, when the lighting state and preheating state are alternately repeated, the capacitor C4, which determines the oscillation frequency of the inverter circuit, repeats charging and discharging with a predetermined time constant, so the oscillation frequency is as shown in FIG. It changes through the resonance point f0 of the LC circuit. Therefore, especially after detecting the end of life and before entering preheating mode, the stress applied to the switching elements Q, , Q2 becomes very large, and the stress applied to the switching elements Q, , Q2 becomes extremely large while the discharge lamp l is blinking. Q. There was a risk that it would be destroyed.

(Object of the invention) The present invention has been made in view of the above points, and
The purpose of this is to reduce the stress on the switching elements of the inverter circuit when starting the discharge lamp, and to notify the user that the discharge lamp is at the end of its life by blinking at the end of its life. It is an object of the present invention to provide a discharge lamp lighting device which is capable of reducing the stress on a switching element during blinking of the discharge lamp.

(Disclosure of the Invention) The configuration of the discharge lamp lighting device according to the present invention is shown in FIGS.
To explain the embodiment shown in the figure, in a discharge lamp lighting device that lights a discharge lamp l by the oscillation output of a separately excited current resonance type inverter circuit, an integrating capacitor C4 is charged via a current limiting element such as a resistor R6. a frequency control circuit 5 that smoothly changes the oscillation frequency of the inverter circuit from the preheating local wave number f1 to the lighting frequency f2 in response to an increase in the charging voltage; and an end-of-life detection circuit 6 that detects the end of the life of the discharge lamp l. , a rapid discharge circuit 7 that rapidly discharges the integrating capacitor C4 of the frequency control circuit 5 to the initial voltage so as to recharge it via the current limiting element when the detection output of the end-of-life detection circuit 6 is generated. It is something.

In the present invention, when the end-of-life detection output of the discharge lamp l occurs, the integrating capacitor C4 for frequency control is rapidly discharged, so that when the lamp is lit, as shown in FIG. When returning from the frequency r2 to the preheating current wave number f, the frequency changes instantaneously to the preheating current wave number f1.
When changing from the lighting frequency f2 to the lighting frequency f2, the frequency changes gradually. Therefore, the stress on the switching elements of the inverter circuit when starting the discharge lamp can be reduced, and at the end of the discharge lamp's life, the frequency changes gradually. By blinking the electric lamp, it is possible to inform the user that the discharge lamp is at the end of its life, and the stress on the switching element when the discharge lamp blinks can be reduced.

Examples of the present invention will be described below.

Figure 2 is a circuit diagram of an embodiment of the present invention. In this embodiment, parts having the same functions as those of the conventional circuit are given the same reference numerals and redundant explanations will be omitted. The capacitance of the capacitor in the load circuit is set so that CI>C2', and the natural oscillation frequency of the load circuit is approximately determined by the inductance L and the capacitor C2.

A control power supply circuit consisting of a series circuit of a resistor R2 and a capacitor C1 is connected to both ends of the DC power supply E. The voltage of capacitor C5 is connected to resistor R7 and Zener diode ZD.
is applied to the series circuit.

The reference voltage developed across the Zener diode ZD is applied to the inverting input terminal of the comparator CP2.

The voltage of the capacitor C9 is applied to the non-inverting input terminal of the comparator CP2. Capacitor C5 is charged via transistor Q with the charging voltage of capacitor C1. A transistor Q is connected to the transistor Q to form a current mirror circuit. Assuming that the current gain hfe of each transistor Q, , Q, is sufficiently large, the current flowing through transistor Q4 is
The current will be the same as that flowing through transistor Q. Transistor Q is connected across capacitor C3 via a series circuit of resistors Rs and Rs. For resistor R5,
A series circuit of a transistor Q and a resistor R4, a capacitor C1, and a transistor Qs are connected in parallel. The output of the timer circuit 4 is connected to the base of the transistor Qs via a resistor R3. The timer circuit 4 is
The preheating time is set, and a high level signal is output for a predetermined time after the DC power supply E is turned on and the charging voltage of the capacitor C1 rises. Therefore, the current flowing through the transistor Q is determined by the resistors R,,R,,R, for a certain period of time after the power is turned on, and then decreases to has a constant frequency determined by the series resistance of resistors R2 and R. This CR circuit constitutes the frequency control circuit 5.

The voltage across the capacitor C1 is connected to the 2nd, 6th, and 7th terminals of the timer ICtm. This timer ICt+a is a general-purpose timer IC (μPD1 manufactured by NEC).
5555), and as is well known, when the trigger terminal (terminal 2) becomes lower than (1/3) Vcc, it is triggered and the output terminal (terminal 3) becomes high level, and the discharge terminal (terminal 7) becomes high impedance. Also, when the threshold terminal (terminal 6) becomes (2/3) V cc, the output terminal (terminal 3) becomes low level, and the discharge terminal (terminal 7) becomes low level.
terminal) is also at a low level.

Therefore, a sawtooth wave voltage is generated across the capacitor C1. This voltage is compared with a reference voltage by a comparator CP2, and a rectangular wave oscillation output is obtained from the comparator CP2.

The output of comparator CP2 is the D flip-flop FF.
The frequency is divided by Output Q of D flip-flop FF,
Q is connected to one input of NAND gates G, , G, respectively. Further, the output Q is connected to the data input terminal. The clock input C is connected to the output of the above-mentioned comparator CP2. Every time the clock input C rises from a low level to a high level, the output of the D flip-flop FF is inverted, and from the outputs Q and Q, a duty factor of 50%, which is the output of the comparator CP2 divided by half, is output. A square wave is obtained. On the other hand, comparator c
The output of p, is the inverter game)-a3. G4 and resistance R
, to the other inputs of the NAND gates G + and G z . It is input to drive circuits 1 and 2 of each NAND gate GQ2. Therefore, the drive signals of the switching elements Q, , Q, alternate between a first period in which one is at a high level and the other is at a low level, and a second period in which one is at a low level and the other is at a high level. There is a third period between the first period and the second period in which both outputs are at a low level. This third
The period is a dead-off time to prevent both switching elements Q, Q2 from being turned on, and it can be a short time taking into consideration the charge accumulation time of the switching elements when they are on. , is determined by the period during which the output of comparator CP2 is at a low level.

A current detection resistor R1 is connected in series to the switching element Q2, and a capacitor C7 is connected to both ends of this resistor R3. The voltage across the capacitor C7 is applied to the non-inverting input terminal of the comparator CP. When the reference voltage Vr is applied to the inverting input terminal of the comparator CP1 and exceeds the level, the voltage drop across the resistor R1 increases and the voltage across the capacitor C7 increases to the reference voltage Vr.
r becomes higher than r, and the output of comparator CP becomes Lo.
w" level becomes "HiHI+" level. The output of comparator CP1 is connected to the reset input of timer circuit 4 via output inhibit circuit ii'83. Set the output to “L”.

w" level, and its terminal is a circuit that outputs the output of the comparator cP1 as it is. The circuit constitutes an end-of-life detection circuit 6 that detects overcurrent at the end of the discharge lamp's life.

With the above configuration, frequency control as shown in FIG. 1 can be performed. In other words, when DC power supply E is turned on,
Transistor Q5 is activated for a certain period of time by the output of timer circuit 4.
turns on. Therefore, the oscillation frequency of the inverter circuit is
The value is approximately determined by the values of the capacitor C2 and the resistor r (5, R41Ra), and preheating is performed at the frequency f.Next, when one time t1 of the timer circuit 4 elapses, its output becomes the level of Mr. The transistor Qs is turned off. Therefore, the capacitor C1 is gradually charged, and its charging voltage reaches the divided voltage of the resistors Rs and Rg. At this time, the oscillation frequency of the inverter circuit is equal to the frequency f during preheating described above. From, resistor R5, R, and capacitor C
The frequency gradually changes to f2 determined by 6. During this frequency change, the discharge lamp 1 is turned on.

Next, when the discharge lamp l reaches the end of its life, the end-of-life detection circuit 6 detects an overcurrent flowing through the switching element Q2, and when an overcurrent exceeding a predetermined level is detected, the output of the end-of-life detection circuit 6 is The level becomes High°, which resets the timer circuit 4 and causes the base current to flow through the transistor Q through the resistor R1.
Turn on.

This causes integrating capacitor C4 to connect to transistor Q6.
The oscillation frequency of the inverter circuit instantly returns to the preheating current wave number f1. This suppresses overcurrent, so the output of the end-of-life detection path 6 becomes 'Lo.
g" level, and the transistor Q6 is turned off. After that, when one time t1 of the timer circuit 4 elapses,
Transistor Q.

is turned off, the integrating capacitor C4 is gradually charged again via the resistor R3, and the oscillation frequency of the inverter circuit is smoothly changed to the lighting frequency f2.

After this, the overcurrent at the end of the discharge lamp life is detected again, and the same operation is repeated, and the oscillation frequency of the inverter circuit becomes the first [? It changes as shown in l. Therefore, the discharge lamp 1 alternately repeats the lighting state and the preheating state, and the output luminous flux blinks, thereby informing the user of the end of the life of the discharge lamp. Moreover, when returning from the lighting state to the preheating state, the frequency is changed instantaneously, so unlike the conventional example, the switching element Q1. It is possible to prevent large stress from being applied to Qz.

Fig. 3 is a circuit diagram of a main part of another embodiment of the present invention, and since the configuration of the main circuit of the inverter device is the same as the circuit in Fig. 2, the illustration is omitted. In this embodiment, the configuration of the control circuit of the inverter device is different from the previous embodiment. tlml is a general-purpose timer IC (μPD1 manufactured by NEC)
5555).

A resistor R that constitutes the time constant circuit of the timer ICLM+.

A power supply voltage ■ee is applied to the series circuit of 2, R+3, and capacitor C. The connection point between resistors RI2 and R13 is.

It is connected to the discharge terminal (terminal 7) of the timer ICt+a+, and the connection point between the resistor R13 and the capacitor C8 is the timer IC.
It is connected to the threshold terminal (terminal 6) and trigger terminal (terminal 2) of tm+. Thereby, timer ICLm+ operates as an astable multivibrator. The oscillation frequency is determined by the time constant of the resistor R12°RI3 and the capacitor C3, and the voltage at the control terminal (terminal 5). Timer ICt+++.

The output terminal (terminal 3) of is connected to a frequency dividing circuit made up of a flip-flop FF.

The configuration of the frequency control circuit 5 is almost the same as that of the first embodiment. After the power is turned on, the output of the timer circuit 4 is at a high level and the transistor Q5 is on for a certain period of time, so the operational amplifier OP has resistors R1, R4, R5 and a resistor R.
The divided voltage with IG is inputted, the impedance is made low by the operational amplifier OP, and it is inputted to the control terminal (5'# terminal) of the timer ICt+al, and the oscillation frequency f1 during preheating is input.
is determined. The operation of the frequency dividing circuit using the flip-flop FF is the same as in the first embodiment.

Next, after one hour [1] of the timer circuit 4 has elapsed, the transistor Q is turned off and the capacitor C1 is charged via the resistor R2, so the input voltage to the operational amplifier oP gradually decreases compared to during preheating. As a result, the oscillation frequency of timer ICtm+ gradually decreases.

This change allows a smooth transition from the oscillation frequency f1 during preheating to the oscillation frequency f2 during lighting.

Furthermore, when the discharge lamp l reaches the end of its life, the end of life detection circuit 6 detects an overcurrent flowing through the switching element Q2,
When a 3at flow higher than a predetermined level is detected, the output of the end-of-life detection circuit 6 becomes the "Hlgll" level,
The timer circuit 4 is reset, and a base current is passed through the transistor Q6 via the resistor R4 to turn on the I transistor Q6.

This causes integrating capacitor C1 to connect to transistor Q6.
The oscillation frequency of the inverter circuit instantly returns to the preheating current wave number f1.

Note that there is no need to specifically limit the volatiles of the integrating capacitor C4 for frequency sweeping in the circuits of FIGS. 2 and 3, but when using an aluminum electrolytic capacitor, the temperature characteristics of its leakage current are As shown in the figure, it exhibits a characteristic that increases exponentially as the temperature increases. Therefore, if you use this characteristic to increase the current flowing through the capacitor C1 at high temperatures and decrease it at low temperatures, IC etc. is designed to be less affected by temperature, so the oscillation frequency has a temperature characteristic that is low at low temperatures and high at high temperatures, and the current flowing through the discharge lamp increases at low temperatures. Therefore, it is possible to solve problems peculiar to discharge lamps, such as turning off the dimmed lighting state at low temperatures and a decrease in luminous flux at low temperatures.

Furthermore, in the description of the embodiment, the end-of-life detection circuit 6 has been exemplified as a circuit that detects an overcurrent at the end of the life of a discharge lamp, but it may also be a circuit that detects a half-wave discharge state of the discharge lamp.

(Effects of the Invention) As described above, the present invention is capable of smoothly changing the oscillation frequency from the preheating frequency to the lighting frequency in response to an increase in the charging voltage of the integrating capacitor charged via the current limiting element. In a device for lighting a discharge lamp using a separately excited current resonant inverter circuit, when an end-of-life detection output of the discharge lamp occurs, an integrating capacitor for frequency control is recharged via the current limiting element. Since the battery is rapidly discharged to the initial voltage, it is possible to instantly return from the lighting frequency to the preheating frequency, and the frequency can be changed gradually when changing from the preheating frequency to the lighting frequency. Therefore, the stress on the switching elements of the inverter circuit when starting the discharge lamp can be reduced, and at the end of the discharge lamp's life, the discharge lamp can blink to notify the user that it is at the end of its life. This has the effect of reducing the stress on the switching element during blinking of the discharge lamp, and realizing a highly reliable lighting device.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the operation of the present invention, Fig. 2 is a circuit diagram of one embodiment of the invention, Fig. 3 is a main circuit diagram of another embodiment of the invention, and Fig. 4 is an explanation of the operation of the same. 5 is a circuit diagram of a conventional example, 6I2I is an explanatory diagram of the same operation as above, FIG. 7 is a circuit diagram of another conventional example, and FIGS. 8 and 9 are explanatory diagrams of operation same as above. C1 is an integrating capacitor, R3 is a resistor, E is a DC power supply, Q
, C2 is a switching element, l is a discharge lamp, 5 is a frequency control circuit, 6 is an end-of-life detection circuit, and 7 is a rapid discharge circuit.

Claims (2)

[Claims] (1) In a discharge lamp lighting device that lights a discharge lamp using the oscillation output of a separately excited current resonant inverter circuit, the oscillation frequency of the inverter circuit changes depending on the rise in the charging voltage of the integral capacitor charged via the current limiting element. A frequency control circuit that smoothly changes the frequency from the preheating frequency to the lighting frequency, an end-of-life detection circuit that detects the end of the discharge lamp's life, and an integral capacitor of the frequency control circuit when the detection output of the end-of-life detection circuit occurs. and a rapid discharge circuit for rapidly discharging to an initial voltage so as to recharge the discharge lamp through the current limiting element. (2) The frequency during preheating is set higher than the natural resonant frequency of the resonant circuit, and the frequency during lighting is set lower than the natural resonant frequency of the resonant circuit and higher than the resonant frequency of the load circuit during lighting. A discharge lamp lighting device according to claim 1, characterized in that: