JPH088152B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device using a separately excited drive inverter.

(Background Art) FIG. 7 is a circuit diagram of a conventional discharge lamp lighting device. Source voltage of the ac power supply AC is rectified by a diode bridge DB, a smoothing by the capacitor C _0, it is a DC voltage. This DC voltage is applied to the series circuit of the primary side of the leakage transformer T ₁ and the semiconductor switch element Q ₁ . The discharge transformer is connected to the secondary side of the leakage transformer T ₁ via a capacitor C _2.
DL ₁ and DL ₂ are connected, and a reactance element (capacitors C ₃ and C ₄ ) is connected to the non-power source side of each discharge lamp to form a preheating circuit for the discharge lamp filament. The diode D ₁ is connected in antiparallel to the semiconductor switch element Q ₁ . Also,
A capacitor C ₁ that exhibits a resonance state with the inductance component of the circuit is connected in parallel to both ends of the switch element Q ₁ . The position where this capacitor C ₁ is connected is the leakage transformer T ₁
Both ends of the primary coil may be used.

The output of the separately excited signal generating circuit SG is input to the control pole of the semiconductor switch element Q _{1 through} the drive transformer T ₂ and the conduction prohibiting circuit B. The separately excited signal generation circuit SG receives power supply from the control unit power circuit PW connected to the smoothing capacitor C ₀ .

FIG. 8A shows the separately excited signal for controlling the ON / OFF of the semiconductor switching device Q ₁ (referred to as the separately excited ON signal at the “High” level and the separately excited signal at the “Low” level). ) Is shown. When the semiconductor switch element Q ₁ is turned on by the separately excited ON signal, a current as shown in FIG. 8 (C) flows through the primary side of the leakage transformer T ₁ . When the semiconductor switching device Q ₁ is turned off by the separately excited off signal, the leakage transformer T ₁ resonates with the capacitor C ₁ due to the energy stored in the LC component of the circuit, and is shown in FIG. 8 (d). Such a resonant capacitor current flows, and a resonant voltage as shown in FIG. 8B is generated across the semiconductor switch element Q ₁ . When the resonance voltage becomes zero, the resonance current flows through the diode D _1, and when the diode current (Fig. 8 (e)) becomes zero, the external excitation signal causes the semiconductor switch element Q ₁ to be the same as in the previous cycle. An electric current flows through (Fig. 8 (c)). In this way, the oscillation continues. Then, the voltage generated on the secondary side of the leakage transformer T _{1 due to} this resonance is applied to the discharge lamp via the leakage inductance and the capacitor C ₂ to light it.

By the way, when the filament is broken, when the discharge lamp is not connected, or when there is no load such as a transient state due to the removal and installation of the discharge lamp, the reactance element is not connected, so the natural vibration cycle of the circuit is large. It changes and the cycle becomes large. Therefore, the natural vibration frequency of the circuit under no load is lower than that during lighting of the discharge lamp. As described above, even when the natural oscillation period of the circuit changes, the voltage of the resonance capacitor C ₁ is high because the semiconductor switch element Q ₁ is forcibly turned on in accordance with the period of the separately excited signal in the separately excited drive type. In this state, the semiconductor switching element Q ₁ may turn on, the rush current from the capacitor C ₁ may flow into the semiconductor switching element Q ₁ , causing a large power loss, and may also damage the semiconductor switching element Q _1. is there. Therefore, in the circuit of FIG. 7, a switch element voltage detection circuit A and a conduction prohibition circuit B are provided. The voltage across the semiconductor switch element Q ₁ is detected by the switch element voltage detection circuit A.
The detection output of the switch element voltage detection circuit A is input to the NOR circuit G ₂ of the conduction prohibition circuit B. The conduction prohibiting circuit B is a circuit for prohibiting the conduction of the semiconductor switching element Q ₁ even when the separately excited ON signal is generated during the period in which the semiconductor switching element Q ₁ has the voltage across the semiconductor switching element Q ₁ . A signal obtained by inverting the separately excited signal from the separately excited signal generation circuit SG by the NOT circuit G ₁ is input to the other input of the NOR circuit G ₂ .

At no load, the natural vibration cycle of the inverter circuit becomes longer than that at lighting, and the switch element voltage becomes a long cycle vibration voltage as shown in FIG.
The switching element voltage detection circuit A detects the generation period of this voltage, and during the period when the detection output (Fig. 8 (g)) is at "H" level, the conduction prohibition circuit B passes the external excitation ON signal. Drive vibration of the semiconductor switch element Q ₁ is
As shown in the figure (h), the semiconductor switching element Q ₁ is not turned on during the period when the semiconductor switching element Q ₁ has the voltage across it. Therefore, at no load, even if the natural frequency of the inverter circuit becomes lower than that at the time of lighting, the semiconductor switching element Q ₁ will not be conducted by the separately excited signal in the state where the voltage of the resonant capacitor C ₁ is high, It is possible to prevent the rush current from the resonance capacitor C ₁ from flowing to the semiconductor switch element Q ₁ .

In this circuit, by changing the on / off duty of the separately excited signal, the current flowing through the semiconductor switch element Q ₁ changes, so the resonance current value changes and the voltage applied to the discharge lamp is changed. It is possible to set the preheating state in which the discharge lamp cannot be turned on, the lighting state, and the dimming state. The duty of the separately excited signal can be easily changed by switching the resistance value in the CR time constant circuit for determining the oscillation frequency inside the separately excited signal generating circuit SG.

However, in the transitional state at the time of switching the duty, it takes time for the conductance of the discharge lamp to change and reach a constant state. Therefore, it takes time for the vibration of the inverter circuit to reach a steady state. In this transient state, if the operation of prohibiting the separately excited signal when (semiconductor switch element voltage)> 0 is performed, the oscillation mode shifts to another oscillation mode as shown in FIG. The discharge lamp does not light when switching from the on-duty for preheating to the on-duty for lighting because the frequency drops significantly and the output voltage drops, or the discharge lamp when switching to the on-duty for dimming Was found to disappear.

For this mode of operation has a preheating circuit including a reactance element to the non-power supply side of the discharge lamp, the vibrations of the secondary side of the leakage transformer T _1, 1 of leakage transformer T ₁
The waveform is superimposed on the vibration on the next side. As described above, if the external excitation signal is prohibited when (semiconductor switch element voltage)> 0, the semiconductor switch element voltage becomes zero due to a rapid change in the conductance of the discharge lamp in the transient state during duty switching. If there is a case where it does not return to, it will be stable with the transition to such a vibration mode, and it will not return to the original state.

(Object of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to distinguish a discharge lamp from a starting state, a lighting state, and a dimming state in a transient state. Another object of the present invention is to provide a discharge lamp lighting device using a separately-excited drive inverter, which can surely reach lighting without shifting to the oscillation mode.

DISCLOSURE OF THE INVENTION A discharge lamp lighting device according to the present invention, as shown in FIGS. 1 to 6, includes a DC power supply V _DC and a semiconductor switch element Q ₁ that is forward to the DC power supply V _DC . , A diode D ₁ connected in parallel to the semiconductor switching device Q ₁ in the opposite direction to the DC power supply V _DC , an inductance element such as a leakage transformer T ₁ connected in series with the semiconductor switching device Q ₁ , and an inductance element. And a capacitor that exhibits resonance
C ₁ and the discharge lamps DL ₁ and DL ₂ to which the resonance voltage generated by turning on and off the semiconductor switching element Q ₁ is applied via the stabilizing element.
And an external excitation signal generating circuit SG that repeatedly controls conduction of the semiconductor switching device Q ₁ under predetermined conduction conditions in each state of the discharge lamp, and at least when there is no load the semiconductor switching device Q ₁ has a voltage at both ends. In an inverter circuit including a continuity prohibition circuit B that prohibits a separately excited signal from being input to the conduction control pole of the semiconductor switch element Q ₁ , the operation of the continuity prohibition circuit B is performed during a transitional period when the state of the discharge lamp changes. It is provided with a circuit for stopping.

That is, in the present invention, the semiconductor switch element Q ₁
Of and when switching duty, etc. as in the fixed period after power-on, in a transition period in which the state changes of the discharge lamp, the conduction of the semiconductor switching element Q ₁ when the semiconductor switching element Q ₁ is a voltage across The operation of the prohibited circuit is stopped, and the semiconductor switch element Q ₁
Is driven on and off to overcome the transient state until the conductance of the discharge lamp stabilizes. The duration of this transient state varies depending on the discharge lamp and is approximately 0.1 to 1 msec.
Is.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the circuit of the embodiment, the same elements as those of the circuit of the related art are designated by the same reference numerals, and the duplicated description will be omitted.

Embodiment 1 FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram thereof. In this embodiment, a transistor is used as the semiconductor switch element Q ₁ . The output of separately excited signal generator SG is NOT circuit G
It is inverted at ₁ and input to NOR circuit G ₂ . The output of the switch element voltage detection circuit A is input to the other input of the NOR circuit G _2.
It is input via the AND circuit G ₅ . The output of the NOR circuit G ₂ is input to the base of the control pole of the transistor Q ₁ via the drive transformer T ₂ .

The control unit power supply circuit PW supplies the separately excited signal generation circuit SG with the power supply voltage (Fig. 2 (a)), and outputs a signal that becomes "L" level at the rise of the power supply voltage. Input to circuit G ₃ . The duty switching signal generation circuit CHG outputs a duty switching signal (Fig. 2 (b)) for changing the duty of the external excitation signal to the external excitation signal generation circuit SG, and at the time of its rising and falling, "L". "The signal that becomes the level is output, and this signal is AND
Input to circuit G ₃ . Accordingly, the output of the AND circuit G ₃ are a time of rising of the control unit supply voltage, during the time and falling rising duty switching signal, the "L" level, which is a timer trigger signal (FIG. 2 (c)) . The output of the timer circuit TM becomes "H" level for a predetermined timer period τ from the time when the timer trigger signal becomes "L" level, and the output becomes "L" level after the lapse of the timer period τ. The output of the timer circuit TM is NOT circuit G
It is inverted at _4, and is input to the AND circuit G ₅ as an inverted output of the timer circuit (FIG. 2 (d)). For this reason,
The detection output of the switch element voltage detection circuit A is AND circuit G ₅ only when the timer circuit inversion output is at the “H” level.
Through (Fig. 2 (e)). Therefore, the prohibition operation of the external excitation signal is stopped until the predetermined timer period τ elapses from the rising of the control unit power supply voltage or the rising or falling of the duty switching signal, and during this period. , The semiconductor switch element Q ₁ is driven as it is by the separately excited signal. FIG. 3 shows operation waveforms at the time of duty switching, and when the on-duty of the separately excited signal (FIG. 3 (b)) is switched at the timing t ₁ , the switching element voltage (FIG. )) Is high, the semiconductor switching device Q ₁ is still conducting. By doing so, it is possible to prevent inconveniences such as transitioning from a transient disturbance of the vibration mode at the time of switching the on-duty to oscillation in another mode and causing the discharge lamp to go out.

In the present embodiment, in the case of no load, the rush current flows because it is driven by the separately excited signal during the timer period τ at the time of switching the duty, but a transient state occurs due to the elapse of the timer period τ. When the conductance of the discharge lamp becomes stable and the vibration mode of the circuit becomes stable after passing through, the prohibition operation of the external excitation signal when (semiconductor switch element voltage)> 0 described above is restarted, so that the semiconductor switch element Q ₁ Rush current inflow is prevented and therefore power losses are not high.

Second Embodiment FIG. 4 is a circuit diagram of another embodiment of the present invention, and FIGS. 5 and 6 are operation explanatory diagrams thereof. In FIG.
The terminals a to d are connected to each other. In the present embodiment, the no-load detection circuit D is provided, and it is determined whether or not there is no load during the period when the vibration mode is stable (period other than τ). In addition, even when the duty is switched, conduction is prohibited when the switch element voltage is high. Therefore, in the present embodiment, the rush current does not flow in the semiconductor switch element Q ₁ even when the duty is switched without load.

The no-load detection circuit D in the circuit of FIG. 4 uses the fact that the cycle of natural vibration at no load is longer than the off period of the separately excited signal as a method for determining no load. When the separately excited ON signal appears when the element voltage is high, it is determined that there is no load. Figure 5 shows
It is a waveform diagram for explaining the principle of this no-load determination,
The figure (a) shows the switch element voltage when there is no load, and the figure (b) shows the separately excited signal. The shaded portion of the separately excited on signal in FIG. 11B corresponds to the case where the separately excited on signal appears when the switch element voltage is high, and the no-load detection circuit D detects this state. If it does, it is determined that there is no load.

In the no-load detection circuit D, when the no-load state is detected,
RS flip-flop FF ₁ for storing the detection result
Is provided. The signal that becomes "L" level when the power supply voltage output from the control unit power supply circuit PW rises is the NOT circuit G
It is inverted at ₆ and input to the reset input R of the RS flip-flop FF ₁ . Therefore, at the time of rise of the power supply voltage becomes the reset input R is "H" level, RS flip-flop FF ₁ is reset. The output of the other励信No. generating circuit SG, the output of the switching element voltage detecting circuit A, and the inverting output of the timer circuit is inputted to the AND circuit G _7, the output of the AND circuit G ₇ is a set of RS flip-flop FF ₁ It is an input S. Therefore, during the period when the timer period τ of the timer circuit TM has passed and the oscillation mode is stable, when the switch element voltage (Fig. 5 (a)) is high, the separately excited signal (Fig. 5 (b)) is generated. As a result, the set input S becomes "H" level, the RS flip-flop FF ₁ is set, and its Q output (Fig. 6 (e)) becomes "H" level. When the Q output of the RS flip-flop FF ₁ becomes “H” level, the OR circuit G
Since the output of ₈ is always "H" level, as shown in FIG. 6 (f), the AND circuit G ₅ causes always passes the detection output of the switch element voltage detection circuit A. Therefore, even if the duty switching signal (FIG. 6 (b)) is generated, the conduction prohibiting circuit B operates, and the rush current at the time of no load is prevented. If there is no load, the RS flip-flop FF ₁ is not set, and the operation is the same as that of the first embodiment.

In the embodiment, the timer circuit TM is used to
Although the switching period of the vibration mode is determined, the completion of the actual switching of the vibration mode may be detected.

(Effects of the Invention) As described above, according to the present invention, in the resonance-type separately excited inverter circuit, the conduction prohibiting circuit that prohibits conduction of the switch element during the period when voltage is applied to the semiconductor switch element is used. Since the operation is provided with a circuit that is stopped during a transitional period when the state of the discharge lamp changes, it is possible to prevent the oscillation mode of the inverter from shifting to another oscillation mode having a low frequency. There is an effect that it is possible to surely shift to the normal oscillation mode.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, FIGS. 2 and 3 are operational explanatory diagrams of the same, and FIG. 4 is a circuit diagram of another embodiment of the present invention. 5 and 6 are explanatory diagrams of the same operation as above, FIG. 7 is a circuit diagram of a conventional example, and FIGS.
The figure is a diagram for explaining the operation of the above. V _DC is a DC power supply, Q ₁ is a semiconductor switch element, D ₁ is a diode, C ₁ is a capacitor, T ₁ is a leakage transformer, DL ₁ ,
DL ₂ is a discharge lamp, SG is an external excitation signal generation circuit, CHG is a duty switching signal generation circuit, A is a switch element voltage detection circuit, B
Is a conduction prohibition circuit, TM is a timer circuit, and G ₅ is an AND circuit.

Claims (1)

[Claims] 1. A DC power supply, a semiconductor switch element that is forward to the DC power supply, a diode that is connected in parallel to the semiconductor switch element in a reverse direction to the DC power supply, and a series connection to the semiconductor switch element. An inductance element, a capacitor that exhibits a resonance state with the inductance element, a discharge lamp to which a resonance voltage generated by turning on and off a semiconductor switch element is applied via a stabilization element, and a semiconductor under predetermined conduction conditions in each state of the discharge lamp. Separate excitation signal generation circuit for repeatedly controlling conduction of the switch element, and conduction prohibition for prohibiting input of the separately excited signal to the conduction control pole of the semiconductor switch element at least during a period when the semiconductor switch element has a voltage across both ends when there is no load. An inverter circuit that includes a circuit The discharge lamp lighting apparatus characterized by comprising providing a circuit for stopping the operation.