JP3061147B2 - 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 apparatus for lighting a discharge lamp at a high frequency using a so-called self-excited inverter type inverter circuit.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional discharge lamp lighting device (Japanese Patent Application No. Hei.
It is a circuit diagram of No. 2-34234). Hereinafter, the circuit configuration will be described. At both ends of the DC power source E, it is connected first switching element Q ₁ a second series circuit of the switching element Q _2. Between both ends of the switching element Q _1, the discharge lamp La, the capacitor C _3, to connect the series circuit of the primary winding n ₁ of the inductor L _1, 2 of the inductor L ₁
The induced outputs of the primary winding n ₂ via the resistor R ₃ are input to the control terminal of the switching element Q ₁ (base-emitter). The non-power side of the filament of the discharge lamp La resonance and capacitor C ₄ for preheating current supply are connected in parallel. The switching element Q _1, a bipolar transistor is used, the diode D ₃ for reflux is connected in inverse parallel between its collector and emitter. Second as the switching element Q _2, the power MOSFET is used, anti-parallel diodes are built.
The across the switching element Q _2, a pair of resistors R _4,
A series circuit of R ₅ are parallelly connected. This resistance R
_4, a series circuit of R _5, by applying a voltage across V ₂ of the switching element Q ₂ min, constitute a on-period detecting unit 1 for detecting the ON of the switching element Q _1. When the switching element Q ₁ is on, the signal Sb obtained by dividing the voltage across V ₂ of the switching element Q ₂ min is High level, the switching element Q ₁ is turned off, the signal Sb is L
ow level. After the signal Sb detected by the resistors R ₄ and R ₅ is inverted by the inverting circuit G _2, the signal Sb is input to the AND circuit G ₁ together with the control signal Sa output from the astable multivibrator IC ₁ , and its logical product output Sc is output. set the oN period of the switching element Q ₂ by make up another励信No. generator 2. The astable multivibrator IC ₁ is a general-purpose integrated circuit for timer (for example, μP
D1555) consists, is set by the output pulse width resistor R ₁₂ and the time constant circuit of the capacitor C _6. The output pulse width of the separately-excited signal generator 2 is controlled by the on-period control unit 3 and can be made shorter by a preheating timer unit 4 for a certain period of time after power-on than during normal operation.

FIGS. 7 and 8 are operation waveform diagrams of the above circuit.
You. Hereinafter, the operation of the above circuit will be described. Separate excitation signal
When Sc becomes High level, the switching element Q_Two
Is turned on, the DC power source E, the discharge lamp La, and the capacitor C
_Three, Inductor L₁, Switching element Q_Two, DC power supply
The current I in the path E_TwoFlows. At this time,
L₁Primary winding n₁Contains the current I_TwoSame oscillating current I as
_ThreeFlows. On the other hand, the separately-excited signal Sc becomes Low level.
And the switching element Q_TwoTurns off, but the resonance
Capacitor C_FourAnd inductor L₁Energy stored in
The oscillating current I_ThreeTries to keep flowing.
At this time, the inductor L₁Secondary winding n _TwoInduced voltage V
_ThreeReverse the polarity. Here, from the separate excitation signal generator 2
The generated separate excitation signal Sc has an oscillating current I_ThreeShorter cycle than
It is set well. Switching element Q_TwoTurned off
Immediately after, the inductor L₁, Diode D_Three, Discharge lamp L
a, capacitor C_Three, Inductor L₁Current in the path
I₁Flows. In addition, inductor L₁Secondary winding n_TwoTo
The switching element Q₁Is biased
When the direction of the resonance current is reversed,
Inductor L₁, Capacitor C_Three, Discharge lamp La, switch
Ching element Q₁, Inductor L₁Current I₁
Flows. Then, the inductor L₁Primary winding n₁Flow
Oscillating current I_ThreeChanges in the inductor L₁2
Next winding n_TwoThe bias current flowing through the
Element Q₁Turns off. Switching element Q₁Is on
During the period where_TwoVoltage V_Two
Is almost equal to the output voltage of the DC power source E,
Child Q₁Is turned off, the switching element Q_TwoOf both ends
The pressure becomes almost zero. Therefore, the switching element Q_Two
R connected between both ends of the_Four, R_FiveVoltage signal at connection point
The switching element Q₁On / off
Can be detected. Switching is performed by the detection signal Sb.
Element Q₁, Q_TwoSwitching elements to prevent simultaneous
Q_TwoIs controlled.

As described above, the switching elements Q ₁ , Q
₂ are alternately turned on and off, so that the inductor L
Is oscillating current I ₃ flows through the _1, the discharge lamp La is lighted at a high frequency. The preheating timer unit 4 is configured such that the on-period of the external excitation signal output from the external excitation signal generating unit 2 is shortened by a fixed time set by the preheating timer unit 4 from the time of power-on,
By reducing the energy supplied to the discharge lamp La, the discharge lamp La
The preheating of the filament is performed without turning on.
When the time set by the preheating timer unit 4 elapses, the ON period of the separate excitation signal gradually increases, and the discharge lamp La is turned on.

As described above, to prevent the switching elements Q ₁ and Q ₂ from being simultaneously turned on, the output signal Sb from the connection point of the resistors R ₄ and R ₅ connected in parallel to the switching element Q ₂ is inverted by the inverting circuit G _2. after inversion, the control signal Sa output from the astable multivibrator IC _1, entered to the aND circuit G _1, it is achieved by setting the oN period of the switching element Q ₂ by the logical product signal Sc.
That is, in this configuration, the astable multivibrator IC
Regardless control signal Sa outputted from the _1, until the switching element Q ₁ is turned off, the output signal Sc from the AND circuit G ₁ is do not go High level, both switching elements Q _1, Q ₂ and the on-time Is prevented.

Astable multivibrator IC₁Is the resistance
R₁₂And capacitor C₆Of the output signal Sa by the time constant of
Loose width is set. And the capacitor C₆Filling
Electric velocity, that is, capacitor C₆Charging current i_TwoBy
Therefore, the pulse width changes. On-period control unit 3
Switching transistor Q₁₁Is on,
Capacitor C₆Charging current i_TwoIs the transistor Q₆,
Q₇Constant current i from the current mirror circuit of₁Equal to
i_Two= I₁Becomes Switching transistor Q₁₁But
The capacitor C₆Charging current i
_TwoIs the constant current i ₁Transistor Q₉, Q_TenMosquito
Constant current i to Rent mirror circuit_ThreeMinus i_Two=
i₁−i_ThreeBecomes Therefore, the switching transistor
Star Q₁₁Is off when the astable multivibrator
IC₁Has a longer pulse width. switch
Transistor Q₁₁Of the switching element
Child Q_TwoR connected in parallel to_Four, R_FiveOutput of connection point
Signal Sb and Astable Multivibrator IC₁Output signal
Circuit G for inputting the signal Sa_FourOutput signal Sd
Therefore, it is controlled. As described above, the resistance R_Four, R_Fiveof
The output signal Sb from the connection point is₁But
When it is on, it is at High level, and when it is off, it is
It becomes Low level. Switching element Q₁Is on
KINI, Astable Multivibrator IC₁Output from
When the control signal Sa rises, the NAND circuit G_FourOutput
Is the switching element Q₁Low level until is turned off
become. NAND circuit G_FourOutput is low level
And the switching transistor Q₁₁Turns off,
The on-period of the control signal Sa is extended.
That is, the switching element Q₁On period is longer
The external excitation signal Sc output from the external excitation signal generation unit 2
The duration of the maintenance period will be longer.

Thus, the switching element Q₁On
Switching element Q based on the period _TwoChange the ON period of
The variation of switching elements and temperature
A change in lamp current due to the change can be suppressed.
In particular, the switching element Q₁The longer the on period of
Switching element Q_TwoWhile reducing the on-time of
Switching element Q₁And switching element Q_TwoOn period
Control to increase the total time of the lamp current
The effect of suppressing the change in the height is increased.

[0008]

In the above-mentioned conventional example, when the discharge lamp La is turned on, there is an effect of suppressing a change in the lamp current with respect to the variation of the switching elements. in the same rate of change, since by changing the oN period of the switching element Q ₂ based on the oN period of the switching element Q _1, as described below,
In some cases, the inverter may enter an abnormal oscillation state due to transient vibration after the start of oscillation.

The present invention has been made in view of such a point, and an object of the present invention is to control a discharge lamp to a high frequency by an inverter that controls one of a pair of switching elements separately and controls the other by self-excitation. In the discharge lamp lighting device that controls the on-period of the switching element that is separately-excited, with the change of the on-period of the switching element that is self-excited, it is caused by transient vibration during preheating. An object of the present invention is to prevent occurrence of an abnormal oscillation state.

[0010]

The present invention SUMMARY OF], in order to solve the above problem, as shown in FIG. 1, first across the DC power supply switching device Q ₁ and the second switching element Q ₂ And a series circuit of a discharge lamp La, a capacitor C ₃ and an inductor L ₁ is connected in parallel to the first switching element Q ₁ , and the second switching element Q ₂
Is controlled by a separate excitation signal, and the first switching element Q ₁ is turned on / off by an induced output of a secondary winding provided in the inductor L ₁ , whereby the first
Switching element Q ₁ and the second switching element Q ₂
In preparative discharge lamp lighting apparatus that are turned on with a high frequency discharge lamp La alternately turns on and off, and on the period detecting section for detecting the first on period of the switching element Q _1, the first switching element and other励信No. generator for generating a No. other励信to turn the second switching element Q ₂ in the oFF period of Q _1, the second switching element Q ₂ based on the first on period of the switching element Q ₁ An on-period control unit for changing the on-period of the second switch;
Is characterized in further comprising a change rate switching unit for switching the rate of change of the ON period grayed element Q ₂ in the lit and during preheating of the discharge lamp La.

[0011]

According to the present invention, as described above, according to the ON period of _one switching element Q1, the other switching element Q1 is turned on.
_{Since the} rate of change for changing the ON period of ₂ is switched between preheating and lighting, by increasing the rate of change during preheating, a stable oscillation operation can be performed even in a transient vibration state at power-on or at the start of oscillation. It is possible to reduce the rate of change at the time of lighting, thereby suppressing a change in load current with respect to a change in power supply.

[0012]

FIG. 1 shows a circuit configuration of an embodiment of the present invention. This lighting device converts a DC voltage obtained by rectifying and smoothing a commercial power supply Vs by a voltage doubler rectifier circuit composed of diodes D ₁ and D ₂ and capacitors C ₁ and C ₂ to a high-frequency voltage by a so-called self-excited self-limiting series inverter circuit. Thus, the discharge lamp La is turned on at a high frequency. In the figure, IC ₁ is an astable multivibrator using a general-purpose integrated circuit (for example, μPD1555), and is determined by the collector current of the transistor Q ₇ flowing through the current mirror circuit of the transistors Q ₆ and Q ₇ and the capacitance of the capacitor C ₆ . Its output terminal (3
High-level period of the pin C) is determined, and the capacitor C
Low level period by the time constant of ₆ and a resistor R ₁₂ is determined. IC ₂ is a D flip-flop. Here, the inverted output terminal is connected to the data input terminal and used as a frequency dividing circuit. Inverting circuit G ₂ and AND circuit G
_1, resistor R _4, the R ₅ detects the on state switching element Q _1, when the switching element Q ₁ is in the ON state, D flip-flop I to the switching element Q ₂
Those that are controlled to the ON signal from the C ₂ is not given.

[0013] transistor Q ₃ are compares the charging voltage of the voltage across the capacitor C ₅ of the resistor R _8. Capacitor voltage of C ₅ are, (determined by the resistor and the control power supply voltage _{Vcc R 7, R 8, R} 9 , etc.) initialization voltage of the resistor R ₈ + Vb
While the voltage is lower than e ₃ (the voltage between the base and the emitter of the transistor Q ₃ ), the base potential of the transistor Q ₈ is the set voltage (constant value). Thereafter, in accordance with the voltage of the capacitor C ₅ is gradually increased by the time constant of the resistor R ₆ and the capacitor C _5, by also increases the base potential of the transistor Q _8, with it, also increases the emitter voltage of the transistor Q _8, current flowing through the resistor R ₁₀ is decreased.
Thus, the collector current of the transistor Q ₆ is reduced, the transistor Q constituting the current mirror circuit
₇ because the collector current is also decreased, the oscillation frequency of the astable multivibrator IC ₁ is decreased. That is, the transistor Q ₃ , the resistors R ₆ , R ₇ , R ₈ , and the capacitor C ₅
And the like operates as a pre-heating timer.

When the output of the inverting circuit G ₃ is at a high level during the period when the output of the D flip-flop IC ₂ is at a high level, the NAND circuit G ₄
The output becomes Low level. Thereby, the resistance R ₁₄
Since the bias current flowing to the base of the transistor Q ₁₁ is eliminated via a transistor Q ₁₁ is OFF, a current mirror circuit composed of the transistors Q _9, Q ₁₀ is operated. When the transistors Q ₉ and Q ₁₀ are turned on, a mirror current determined by the resistor R ₁₃ flows as a collector current of the transistor Q ₁₀ and thus acts as a discharge current of the capacitor C ₆ . That is, the charging current of the capacitor C _6, when the respective I _7, I ₁₀ the collector currents of the transistors _{Q 7, Q 10, (I} 7 -I 10) and the output terminal of the astable multivibrator IC ₁ by the value (3
(Pin No.) changes to the High level. Here, the period in which the output of the NAND circuit G ₄ becomes High level, the variations in the characteristics of the switching element Q ₁ made of bipolar transistors, the switching element Q
_When the on-period ₁ changes, the period during which the output of the astable multivibrator IC ₁ is at the High level also changes. At this time, the Q output of the D flip-flop IC ₂ Is High
Level, the D flip-flop IC ₂
The period during which the Q output at the High level is at the High level also changes. Accordingly, also changes the length of the on signal provided to the switching element Q ₂ through the AND circuit G _1. From the above,
By a change in the on-period switching elements Q _1, is capable of controlling the ON period of the switching element Q _2.

Transistor Q_Four, Q_FiveCurrent mirror
The circuit includes the switching element Q described above. ₁For the ON period of
And the switching element Q_TwoControl variable to control the ON period of
Provided to switch the conversion rate between the preheating state and the lighting state.
Have been. That is, during preheating,
Jista Q₈Is constant, the resistance R₉To
The flowing current is constant, and the current
Q_Four, Q_FiveTransistor through a current mirror circuit
Q₉Of the transistor Q
_TenCollector current I_TenIncrease and the switching element Q_Two
Are set large. Advance preheating timer
Capacitor C_FiveThe transient
Star Q₈Rises in the resistance R₉The current of
Decrease gradually, capacitor C_FiveVoltage is almost the control power supply
When the pressure rises to Vcc, the resistance R₉The current flowing through
0 amps and the transistor Q_Four, Q_FiveAre both off
And the transistor Q_TenCollector current I_TenIs the resistance R
₁₃Switching element Q_TwoNo
The period change rate is set small.

FIG. 2 shows the operation waveform of each part in this embodiment.
As shown in FIG. First, in FIG. 2 shows the base potential of the transistor Q ₃ in the timer unit for preheating a solid line shows the base potential of the transistor Q ₈ in broken lines. The base potential of the transistor Q ₃ is a transistor Q ₈
During the low period of time than the base potential, the base potential of the transistor Q ₈ is constant, this period is the pre-heating period.
In this period, as shown in FIG. 3 (a), the collector current of the transistor Q ₁₀ is provided with a current flowing through the resistor R ₁₃ resistors R
₉ is the sum of the currents flowing through. Next, when the base potential of the transistor Q ₃ exceeds the base voltage of the transistor Q _8, according to the potential difference is regulated within the base-emitter potential difference Vbe ₃ transistors Q _3, increase in the base potential of the transistor Q _3, transistor also increased the base potential of the Q _8, the operating frequency of the inverter is gradually reduced. This period is the soft start period. next,
When the base potential of the transistor Q ₃ reaches the control power source voltage Vcc, elevated base potential of the transistor Q ₃ are stopped, also constant base potential of the transistor Q _8. Thus, the operating frequency of the inverter becomes the frequency at the time of rated lighting. In this period, as shown in FIG. 3 (b), the collector current of the transistor Q ₁₀ is only the current flowing through the resistor R _13.

According to the present embodiment, thus, a switchable on-period change rate of the switching element Q ₂ in the preheating state lighting state. Thus increase the rate of change in the preheating state, preheat There is an effect that abnormal oscillation in the state can be suppressed. That is, at the time of start of oscillation of the power-on or the inverter, but not to start the operation from the preheat state, this time, as shown in FIG. 4, the load current flowing through the inductor L ₁ of the current limiting is transient vibration Wake up. As can be seen from Figure 4, the period in which current flows through the switching element Q ₁ or diode D ₃ changes the state of the load current. It is because the bias voltage to the switching element Q ₁ which is induced in the secondary winding of the inductor L ₁ by the transient oscillations is changed, presumably because the turn-off conditions of the switching element Q ₁ is changed. Here, the switching element Q _2, the on-signal is adapted to be provided after the switching element Q ₁ is the turn-off, as shown in FIG. 4, the gate signal of the switching element Q ₂ is longer in a transient state Become shorter or shorter. In this case, the control change rate by the on state switching element Q ₂ changes the ON signal of the switching element Q ₁ is small, in some cases, an ON signal to the gate of the switching element Q ₂ is very short, on signal May occur, and a so-called abnormal oscillation state may occur, which may cause stress on the switching element or generate noise.

[0018] In contrast, in the present invention, switching control rate of change of the ON signal of the switching element Q ₂ in the preheating state lighting state, because they increase the control rate of change in the preheat state, as described above on signal to the gate of the switching element Q ₂ is provided reliably even in the transient vibration state, in which it is possible to avoid problems such as that occurrence of an abnormal oscillation state. In addition, at the time of lighting, since the above-mentioned control change rate is reduced, the fluctuation of the load current with respect to the power supply fluctuation can be suppressed as compared with the case where the same control change rate is adopted at the time of preheating and at the time of lighting. .

Furthermore, according to the embodiment shown in FIG. 1, since the to perform gradual switching control rate of change of the ON signal of the switching element Q ₂ in the lighting state and the preheat state,
From the preheating state through the soft-start period, when the discharge lamp La is lighted, it is possible to gradually change the control state of the switching element Q _2, switching element Q
There is an advantage that an ON signal given to the _second gate can be generated stably and smooth lighting can be performed. If, at the moment when the discharge lamp La is shifted to the lighting state from the preheating state, when to switch the control rate of change of the ON signal of the switching element Q ₂ immediately against sudden changes in the impedance of the discharge lamp La, switching since the gate signal of the element Q ₂ also changes rapidly, for example, as shown in FIG. 5, waveform abnormality exits the gate signal of the switching element Q _2, which may fall into an abnormal oscillation state. In this embodiment, a soft start period is provided between the preheating period and the lighting period, and the control change rate is gradually switched during this period to avoid such an abnormal oscillation state.

[0020]

According to the present invention, the discharge lamp is turned on at a high frequency by an inverter that controls one of the pair of switching elements separately and the other is self-excited, so that the on-period of the switching element that is self-excited is controlled. In the discharge lamp lighting device that controls the on-period of the switching element that is separately excited and controlled in accordance with the change of the switching element, the rate of change that changes the on-period of the other switching element in accordance with the on-period of one switching element is calculated. Since switching is performed between preheating and lighting, by increasing the rate of change during preheating, a stable oscillation operation can be performed even in a transient vibration state at the time of power-on or at the start of oscillation. Has the effect that the fluctuation of the load current with respect to the fluctuation of the power supply can be suppressed.

If the rate of change of the ON period between preheating and lighting is gradually switched, the drive signal for the other switching element can be stably transmitted immediately after lighting the discharge lamp. There is an advantage that abnormal oscillation and the like can be prevented.

[Brief description of the drawings]

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

FIG. 2 is an operation explanatory diagram showing a soft start operation according to one embodiment of the present invention.

FIG. 3 is an operation waveform diagram at the time of preheating and at the time of lighting in one embodiment of the present invention.

FIG. 4 is a waveform chart showing a transient vibration state in one embodiment of the present invention.

FIG. 5 is a waveform diagram showing an abnormal oscillation state in one embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional example.

FIG. 7 is a waveform chart showing the operation of the conventional example.

FIG. 8 is a waveform chart showing the operation of the conventional example.

[Explanation of symbols]

La Discharge lamp Q ₁ switching element (bipolar transistor) Q ₂ switching element (power MOSFET) L ₁ inductor G ₁ AND circuit G ₂ inverting circuit IC ₁ astable multivibrator IC ₂ D flip-flop

Continuation of front page (56) References JP-A-4-163890 (JP, A) JP-A-3-238797 (JP, A) JP-A-3-129699 (JP, A) JP-A-2-144894 (JP) JP-A-2-284385 (JP, A) JP-A-2-280673 (JP, A) JP-A-2-1444891 (JP, A) JP-A-2-144892 (JP, A) JP-A-2-284383 (JP, A) JP-A-2-285965 (JP, A) JP-A-2-295098 (JP, A) JP-A-3-84897 (JP, A) JP-A-3-276599 (JP, A A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 41/24 H02M 7/538

Claims (1)

(57) [Claims] 1. A series circuit of a first switching element and a second switching element is connected between both ends of a DC power supply,
A series circuit of a discharge lamp, a capacitor, and an inductor is connected in parallel to the first switching element, and the second switching element is controlled to be turned on and off by a separate excitation signal, and the induced output of a secondary winding provided in the inductor is used. A discharge lamp lighting device in which a first switching element is turned on and off to alternately turn on and off a first switching element and a second switching element to light a discharge lamp at a high frequency. An on-period detection section for detecting an on-period of the first switching element, a separately-excited signal generation section for generating a separately-excited signal for turning on the second switching element during an off-period of the first switching element, the on period control unit for changing the oN period of the second switching element based on the oN period of the switching element, the second
A discharge lamp lighting device, comprising: a change ratio switching unit that switches a change rate of an on-period of the switching element between preheating and lighting of the discharge lamp.