JP3251312B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at a high frequency.

FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device. Hereinafter, the circuit configuration will be described. At both ends of the DC power source E _1, transistors Q _1, Q ₂ is a main switching element through a power switch SW, the resistor R ₉
There are connected in series, to the transistor Q ₁ is diode D ₁
Are connected in anti-parallel, and a diode D ₂ is connected in anti-parallel to a series circuit of the transistor Q ₂ and the resistor R ₉ . At both ends of the transistor Q ₁ is, the inductor L ₁ through the coupling capacitor C ₀ for cutting a DC component (the primary winding n _1, 2 winding n _2), the resonance capacitor C ₁ and the discharge lamp DL Resonant circuit (load circuit) 2 is connected. Furthermore, the resonant circuit only to return the oscillating current flowing to 2 through the resistor R ₁ to the one control terminal of the transistor Q ₁ serving as the main switching element (base), only the transistor Q ₁ in a predetermined cycle determined by the oscillating current on-off control to the feedback means (2 windings n of the inductor L _1
2 ) is provided.

The other transistor Q_TwoIs a monostable multi
Vibrator MV₁On / off control.
Monostable multivibrator MV₁Is a general-purpose integrated circuit
(For example, μPD4538 manufactured by NEC)
From the “High” level to the “Low” level.
The output terminal Q goes to “High”
Output terminal NQ (outputs an inverted signal of the signal at output terminal Q).
Input terminal) becomes “Low” level. In this circuit
The transistor Q_TwoVoltage V_Q2Is the resistance R _Four, R
_FiveIs detected by dividing the voltage with a series circuit of
Vibrator MV₁Of the trigger signal. Monostable
Multivibrator MV₁Output terminal Q is “High” level
Time (when the output terminal NQ goes to "Low" level)
Between) is the resistance R₆And capacitor C_ThreeIs determined by the time constant
It is. The output terminal Q is a resistor R₇Drive for driving through
Star Q_FourAnd the output terminal NQ is connected to a resistor R₈
Through the driving transistor Q_FiveConnected to the base of
ing. Transistor Q_FourIs a DC power supply E_Twoof
Transistor Q_FiveIs the DC power supply E_Twoof
Each is connected to a negative electrode. Transistor Q_Fourof
Emitter and transistor Q_FiveIs a common connection
And the resistance R_TwoThrough the transistor Q_TwoContact the base of
Has been continued. Therefore, a monostable multivibrator
MV₁Is the transistor Q_TwoON period τ₁I decided
It operates as a timer circuit. Invar as above
1 is configured.

In the current detection circuit 3, a transistor
Star Q_TwoCurrent I flowing through_Q2Is the resistance R ₉And the resistance R
_TenAnd capacitor C_FourAnd the detection voltage V_C4Get
This is a comparator IC₁Input to the positive input terminal of
ing. Comparator IC₁To the negative input terminal of
Is the control power supply E_TwoIs the resistance R₁₁, R₁₂Group divided by
Reference voltage V_R12Is entered.

[0005] ST is a starting circuit, a resistor R ₃ , a diode D ₀ , a voltage-responsive switching element Q ₃ , a capacitor C ₂
It consists of, give the start-up signal to the base of the transistor Q _2. Reference numeral 4 denotes an oscillation stop circuit, which includes two diodes D ₃ and D ₄
It is composed of FIG. 5 is an operation waveform diagram of the circuit when the resonance circuit 2 is inductive. FIG.
Represents the load current I flowing through the inductor L _1, drawing I _Q1, I _Q2 collector current flowing through the transistor _{Q 1, Q 2, I D1} , I D2 represents the current flowing through the diode D _1, D ₂ . Also, the same figure (b) the collector-emitter voltage V _Q1 of the transistor Q _1, to FIG. (C) the collector-emitter voltage V _Q2 of the transistor Q _2, FIG. (D) shows the transistor Q ₁ Base-emitter voltage V
_BE1, FIG (e), shows (f) an output terminal Q of the monostable multivibrator MV _1, the output signal of NQ, respectively.

[0006] The operation of the circuit will be described with reference to the operation waveform diagram of FIG. When the power switch SW is turned on, the starter circuit ST transistor Q ₂ is turned on, since the voltage across V _Q2 (FIG. 5 (c)) becomes "Low" level, the trigger input terminal B of the monostable multivibrator MV ₁ Changes from the “High” level to the “Low” level. Thereby, the monostable multivibrator MV
₁ is triggered, its output terminal Q is at “High” level,
The output terminal NQ becomes “Low” level (FIG. 5 (e),
(F)). Accordingly, transistor Q ₄ for driving is turned on, the transistor Q ₅ is turned off, the transistor Q ₂ through the transistor Q _4, the resistor R ₂ from the DC power source E ₂
Base current is supplied, the on-state transistor Q ₂ is maintained. When transistor Q ₂ is turned on, and conducts the diode D _0, since the capacitor C ₂ will not be charged, the starting circuit ST is stopped. In this case, the secondary winding n ₂ of the inductor L ₁ is the base of the transistor Q ₁
Wound in polarity so as to apply a reverse bias voltage between the emitter, the transistor Q ₁ is kept off.

Next, after a lapse of a predetermined time t determined by the resistor R ₆ and the capacitor C ₃ , the monostable multivibrator M
Output terminal Q is "Low" level V _1, the output terminal NQ becomes a "High" level, the transistor Q ₄ is turned off, the transistor Q ₅ is turned on. Therefore, the transistor Q
₂ turns off. When the transistor Q ₂ in the point P shown in FIG. 5 (a) is turned off, the residual inductance of the inductor L ₁ generates an induced voltage in reverse by the collector current I _Q2 of the transistor Q ₂ is decreased, the inductor L ₁
Oscillating current I flowing in
Diode D ₁ is conducting, current I _D1 flows. Further, by the secondary winding n ₁ of the inductor L ₁ generates a reverse induced voltage, as shown in FIG. 5 (d), the transistor Q
₁ is forward biased, the transistor Q ₁ is turned on. When the current I _D1 of the diode D ₁ becomes zero, the collector current I _Q1 flows through the transistor Q _{1 using the} electric charge stored in the coupling capacitor C ₀ as a power supply. At this time, the core of the inductor L ₁ is linearly magnetized towards the saturation magnetic flux.

[0008] Eventually, when the core reaches the saturation magnetic flux,
The conductance suddenly goes to zero, and as a result
Transistor Q₁Collector current I_Q1Time change is infinite
It will be great. Transistor Q₁Collector current I_Q1But
Current h_feWhen it reaches double, the transistor Q₁Is unsaturated
State and the inductor L₁Each primary winding n₁And 2
Next winding n_TwoThe induced voltage of
Current also decreases and transistor Q₁Turns off. Tiger
Transistor Q₁Is turned off, the inductor L₁Flow
Since the oscillating current I tends to flow in the same direction,
Is the diode D _TwoConducts and the current I_D2Is the resonance circuit 2
Combined capacitor C₀, DC power supply E₁Flows along the path.

[0009] Diode D_TwoIs turned on, the transistor
TA Q_TwoVoltage V_Q2Becomes zero, so
BRATOR MV₁Falling trigger input terminal B is “Hig
The “h” level changes to the “Low” level and the monostable multi
Vibrator MV₁Output terminal Q is at “High” level.
Drive transistor Q_FourTurns on, Transis
TA Q_TwoAre forward biased. Diode D_TwoShake
Dynamic current I_D2Becomes zero, the DC power supply E₁More
Combined capacitor C₀, Resonance circuit 2, transistor Q _TwoSutra
Collector current I_Q2Flows.

Hereinafter, by repeating the above operation,
The oscillation operation of the inverter circuit 1 is continued. Further, in the normal operation the inverter circuit 1 are set so that the reference voltage V _R12 appearing between the detection voltage V _C4 appearing across the capacitor C ₄ to both ends of the resistor R ₁₂ is a V _R12> V _C4, the comparator output terminals of the IC ₁ 'a "Low" level, the oscillation of the inverter circuit 1 is continued. Note that the comparator IC ₁ is configured by a general-purpose linear IC (for example, a single power supply quad general-purpose operational amplifier circuit μPC451 manufactured by NEC Corporation).

[0011] Next, no-load or not connected to the discharge lamp DL, when the discharge lamp DL is close to unloaded condition nearing end of life, the current flowing through the transistor Q ₂ is increased, the detection voltage V _C4 There rises, V _R12 <V _C4, and the output terminal of the comparator IC ₁ becomes "High" level. This output signal is fed back to a point of the current detection circuit 3 through the diode D ₄ to form an oscillation stop circuit 4,
Since the above condition is set to be maintained, the output voltage V _O of the comparator IC ₁ holds the “High” level, and the input terminal B of the monostable multivibrator MV ₁ is set to “High” via the diode D _3. "Level. Therefore, the output terminal Q is "Low" level of the monostable multivibrator MV _1, is an output terminal NQ is "High" level, the transistor Q ₄ is turned off, the transistor Q ₅ is turned on, the main switching element transistor Q ₂ is turned off, the oscillation of the inverter circuit 1 is stopped.

[0012]

In the above-described discharge lamp lighting device, when the discharge lamp DL is removed,
Since at the time of end of life, that is immediately detected by the current detection circuit 3, removal of the discharge lamp DL by the oscillation stop circuit 4 is believed may be stopped oscillation immediate inverter circuit 1 (in FIGS. 3 (a) oscillation of the inverter circuit 1 indicates a waveform of a resonance current flowing in the resonant circuit 2 to a stop. time t ₁ is the removal time of the discharge lamp DL) is, as in the conventional example described above, instantaneous power Voltage E
_1, E ₂ of the voltage drop and overvoltage or due to noise or the like, and malfunction the current detection circuit 3, It will be a emitter depletion state and unloaded state, stops the oscillation operation of the inverter circuit 1, turn off the discharge lamp DL There is a possibility that it will be done.

[0013] In order to prevent such malfunction, 4
In the circuit of FIG. 2, the smoothing capacitor C _{4 is} used until the current detection circuit 3 detects the overcurrent flowing in the inverter circuit 1.
Has a certain delay time. Therefore, when the discharge lamp DL is removed and no load is applied, or when the emitter becomes exhausted, the current detection circuit 3 detects an overcurrent and the oscillation operation of the inverter circuit 1 is stopped.
Resonance current flowing through the resonance circuit 2 is as shown in FIG. 3 (b), the take significant stress to the transistor Q _1, Q _2, has the disadvantage that the transistors Q _1, Q ₂ is likely to lead to breakdown. The time t ₂ is the inverter circuit 1
Is the oscillation stop time. Time t ₃ is the oscillation stop time in FIG. 3 (a).

An object of the present invention is to reduce a stress applied to a switching element when stopping an oscillation operation of an inverter circuit by detecting a no-load state and an end-of-life state of a discharge lamp, and to reduce a power supply voltage. An object of the present invention is to provide a discharge lamp lighting device capable of preventing an erroneous stop of an inverter circuit due to a voltage drop, overvoltage, noise, or the like.

[0015]

According to the present invention, there is provided a discharge lamp lighting device comprising: an inverter circuit for converting a DC voltage to a high frequency voltage; a resonance circuit including a discharge lamp to which an output of the inverter circuit is supplied; A current detection circuit for detecting a current flowing through one of the circuit and the resonance circuit, and gently suppressing the oscillation operation of the inverter circuit when the current detected by the current detection circuit exceeds a predetermined value. And an oscillation stop circuit for stopping the oscillation operation of the inverter circuit after a lapse of a predetermined time.

[0016]

According to the above configuration, when the current detection circuit detects an abnormality in one of the conduction currents of the inverter circuit and the resonance circuit, the oscillation operation of the inverter circuit is moderated.
Suppressed in, thereafter it stops the oscillation operation of the predetermined time to the inverter circuit.

[0017]

[First Embodiment]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention. As shown in FIG. 1, this discharge lamp lighting device differs from the circuit configuration of FIG. 4 only in the configuration of the current detection circuit 3A and the oscillation stop circuit 4A. , The same reference numerals are given, and duplicate explanations are omitted. Note that the current detection circuit 3A
The capacitance of the capacitor C _4A is sufficiently smaller than that of the capacitor C _{4 of} FIG. 4 , and there is almost no time delay at the time of current detection.

In this discharge lamp lighting device, the discharge lamp DL
Is normally lit, the reference voltage V _R12 and the detection voltage V _C4 in the current detection circuit 3A are set so that the voltage V _R12 > V _C4 . Therefore, the output terminal of the comparator IC ₁ is at the “Low” level. There, the capacitor C ₅ via a resistor R ₁₃ is not charged. Therefore, since the positive input terminal of the impedance converter IC ₂ is a "Low" level, the output terminal becomes the "Low" level, it does not charge the capacitor C ₆ via the resistor R _16, a comparator IC
The positive input terminal of ₃ becomes “Low” level. The reference voltage V _R15 obtained by dividing the control power supply E ₂ by the resistors R ₁₄ and R ₁₅ is input to the negative input terminal of the comparator IC ₃ . Therefore, the output terminal of the comparator IC ₃ is the "Low" level, the oscillation of the inverter circuit 1 is continued. The comparators IC ₁ , IC ₃ and impedance converter IC ₂ are general-purpose linear ICs (for example,
NEC single-supply quad general-purpose operational amplifier μPC4
51).

Next, when it is the emitter depletion state at the end of life of the unconnected no load or discharge lamp DL in the discharge lamp DL, increased current flowing through the transistor Q ₂ is, the detection voltage V _C4 rises V _R12 becomes <V _C4, the output terminal of the comparator IC ₁ becomes "High" level. This output signal is gradually charges the capacitor C ₅ via a resistor R _13, the output of the impedance converter IC ₂ also outputs a voltage corresponding to the charging voltage of the capacitor C _5, the resistor R _17, the diode D ₅ the input to the T ₂ terminal of the monostable multivibrator MV ₁ through. In this case, the resistor R _6, resistor R _17, a capacitor C _3, since the time constant of the monostable multivibrator MV ₁ is determined by the level of the output voltage of the impedance converter IC _2, the output of the inverter circuit 1 gradually Limited. The output of the impedance converter IC ₂ charges the capacitor C ₆ via the resistor R _16, the voltage across the capacitor C ₆ is equal to or higher than the reference voltage V _R15, an output terminal of the comparator IC ₃ is "High" level become. This output signal is
Through _4, since it is fed back to the positive terminal of the comparator IC _3, the output terminal of the comparator IC ₃ is "High"
Holding the level, the B terminal of the monostable multivibrator MV ₁ through the diode D ₃ is held in the "High" level. Therefore, the output terminal Q of the monostable multivibrator MV ₁ represents the "Low" level, the output terminal NQ becomes "High" level, the transistor Q ₄ is turned off, the transistor Q ₅
There turned on, the transistor Q ₂ is a main switching element turned off, the oscillation of the inverter circuit 1 is stopped.

As described above, the discharge lamp DL
Oscillation stops when a load is applied or at the end of the life of the discharge lamp DL.
The waveform diagram of the resonance current flowing through the resonance circuit 2 until3
As shown in FIG.₁Since then, it has been gradually reduced
Time t when the fixed time has elapsed_TwoCauses the inverter circuit 1 to stop oscillating
It will stop. The discharge lamp lighting device of this embodiment is
Oscillation occurs when the current flowing through the data circuit 1 exceeds a predetermined value.
The oscillation operation of the inverter circuit 1 is gradually performed by the stop circuit 4A.
And after a lapse of a predetermined time from the start of suppression.
The configuration is such that the oscillation operation of the inverter circuit 1 is stopped.
Detects the no-load state and end-of-life state of the discharge lamp DL
To stop the oscillation operation of the inverter circuit 1 by
Transistor Q₁, Q_TwoTo reduce the stress on
Power supply voltage drop, overvoltage, noise, etc.
Erroneous stop of the inverter circuit due to
You.Especially, the oscillation operation of the inverter circuit 1 is moderately suppressed.
After a lapse of a predetermined time, the oscillation of the inverter circuit 1 is generated.
Operation is stopped.
The output level of path 1 is low,
Even if a spike voltage may occur,
The peak value can be kept low, and the transistor Q ₁ , Q
_Two Can be sufficiently suppressed.

[0021]

[0022] [No.2Example of FIG.2Is the first2Circuit of the discharge lamp lighting device of the embodiment
FIG. This discharge lamp lighting device has the circuit shown in FIG.
A voltage detection circuit 5 is added.
Is the same as The voltage detection circuit 5 includes a coupling capacitor.
Sa C₀Connection point between DC and discharge lamp DL and DC power supply E₁Negative
Diode D between poles₆, Resistance R₁₈, R₁₉Series times
Path and insert a resistor R₁₉Capacitor C at both ends of₇Connect
ing. And the resistance R₁₈And resistance R₁₉Connection point (point b and
Do) and monostable multivibrator MV₁Of the input end B of
Between the buffer IC_Four(For example, NEC µPD40
50) and diode D₇And a series circuit is inserted.
This current detection circuit 5 is used when the discharge lamp DL has no load.
The potential at point b becomes “Low” level,
Vibrator MV₁Input terminal B at “Low” level.
To stop the oscillation operation of the inverter circuit 1.
is there. The diode D₈Is the current detection circuit when there is no load
Capacitor C of 3₆The charge of the comparator IC_Three
Output to “Low” level and hold oscillation stop circuit 4A
To release the oscillation and hold the oscillation stop in the voltage detection circuit 5.
belongs to. The resistance R₂₀, R_{twenty one}Is the discharge resistor
is there.

This embodiment has a configuration in which the oscillation operation of the inverter circuit 1 is suppressed and stopped by the two circuits of the current detection circuit 3 and the voltage detection circuit 5, that is, a double safety configuration. The present invention is applied to a discharge lamp lighting device, and in this embodiment, the same effects as those of the above embodiments can be obtained. In each of the above embodiments, the current of the inverter circuit 1 is detected, but a configuration of detecting the current of the resonance circuit 2 may be used.

[0024]

According to the discharge lamp lighting device of the present invention, the oscillation stop circuit gently suppresses the oscillation operation of the inverter circuit, and then the oscillation operation of the inverter circuit is stopped after a predetermined time has elapsed. The inverter circuit does not inadvertently stop oscillating due to an instantaneous voltage drop, overvoltage, noise, or the like of the power supply voltage, and does not exert a large stress on the switching elements of the inverter circuit. In particular, slow the oscillation operation of the inverter circuit.
After a lapse of a predetermined time.
The oscillation operation is stopped.
The output level of the oscillator circuit is low, and oscillation is stopped.
Even if a spike voltage occurs,
The peak value can be kept low, and the switching element
The applied stress can be sufficiently suppressed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 3 shows an inverter circuit according to an embodiment and a conventional example.
FIG. 6 is a waveform chart showing an output change.

FIG. 4 is a circuit diagram showing a configuration of a conventional discharge lamp lighting device.
You.

FIG. 5 is a timing chart of each part of the discharge lamp lighting device shown in FIG . 4;
It is a chart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter circuit 2 Resonant circuit 3A Current detection circuit 4A Oscillation stop circuit 5 Voltage detection circuit

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 41/24

Claims (1)

(57) [Claims] 1. An inverter circuit for converting a DC voltage into a high-frequency voltage, a resonance circuit including a discharge lamp to which an output of the inverter circuit is supplied, and a current flowing through one of the inverter circuit and the resonance circuit. A current detection circuit for detecting, and oscillating operation of the inverter circuit when a current detected by the current detection circuit exceeds a predetermined value.
A discharge lamp lighting device comprising: an oscillation stop circuit that gently suppresses the oscillation and stops the oscillation operation of the inverter circuit after a lapse of a predetermined time.