JPH088151B2 - 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 . A discharge lamp is connected to the secondary side of the leakage transformer T ₂ 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 capacitor C ₁ may be connected at both ends of the primary coil of the leakage transformer T ₁ .

The output of the separately excited signal generation circuit SG is input to the control pole of the semiconductor switch element Q ₁ via the drive transformer T ₂ . The separately excited signal generator SG is an oscillation circuit OS that determines the oscillation cycle.
It has C and an off period generation circuit MV composed of a monostable multivibrator for determining on / off duty, and receives power supply from a 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.

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. In any of these states, the reactance element (capacitor C ₃ , C
_{Since 4} ) is connected, the natural vibration period of the circuit does not change significantly. However, when the filament is broken, or when the discharge lamp is not connected, or when there is no load such as when the discharge lamp is detached or in a transient state, 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.

Thus, even when the natural vibration period of the circuit changes, in the separately excited drive type, the semiconductor switch element Q ₁ turns on in accordance with the period of the separately excited signal, and as shown in FIG. The semiconductor switch element Q ₁ is turned on when the voltage of the resonance capacitor C ₁ is high.
As shown in, the rush current from the capacitor C ₁ flows into the semiconductor switch element Q ₁ , causing a large power loss, and the semiconductor switch element Q ₁ may be damaged.

By the way, the reason why the switch element Q ₁ is driven by the separately excited signal is as follows.

(I) As one of the inverter drive systems, there is a self-excitation system in which a feedback transformer is provided with a feedback winding and vibration is fed back to continue oscillation. According to this method, the above-mentioned problem does not occur in both the no-load state and the lighting state, because the switch element is driven with the natural vibration period in that state. Therefore, JP-A-60-255067 relating to a self-excited inverter circuit is irrelevant to the present invention.

In this self-exciting method, since oscillation is determined by the natural oscillation period of the circuit, it is difficult to control the lamp current such as preheating and dimming by changing the on / off duty, which can be easily done in the separately exciting method. There are drawbacks.

(Ii) Further, as another driving method, there is a driving method in which the natural vibration of the circuit is detected and the switching element is turned on for a predetermined time after the resonance capacitor voltage returns to zero. In this method, the rush current does not flow unlike the separately excited method because the voltage of the resonance capacitor returns to zero and then becomes conductive in both the no-load state and the lighting state.

However, with this drive system, when starting the discharge lamp,
When the discharge lamp shifts from glow discharge to arc discharge, the conductance of the lamp may suddenly change and the voltage of the resonance capacitor may not return to zero, which is a problem in that it is stabilized by vibration that does not lead to start.

If the separately excited method is adopted, the drawbacks of the driving methods (i) and (ii) above can be avoided, and the separately excited control circuit can be integrated into an IC, and the oscillation cycle can be caused by variations in the constants of the main circuit. Is not affected, and there is an advantage that the transformer is inexpensive because the feedback winding is not required. On the other hand, as described above, there is a problem of rush current when there is no load. Such a problem is caused not only by the circuit configuration shown in FIG. 7 but also by a circuit system in which the voltage generated in the resonance capacitor C ₁ is applied to the discharge lamp DL as shown in FIG. 9 (see Japanese Patent Publication No. 57-45040). ), The same problem occurs when the switch element Q ₁ is driven separately.

(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 provide a semiconductor switch device with electric power due to a rush current in a no-load state in which a discharge lamp is not connected. Another object of the present invention is to provide a discharge lamp lighting device using a separately-excited drive inverter, which is capable of suppressing loss and temperature rise and preventing damage to semiconductor switching elements.

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
And C _1, and other励信No. generating circuit SG repeatedly conducting controls the semiconductor switching element Q _1, the discharge lamp DL ₁ applied through the stabilizing element resonance voltage generated by the on-off semiconductor switching elements Q _1, DL ₂ In the inverter circuit in which the natural vibration frequency at the time of no load is lower than that at the time of lighting the discharge lamp, the vibration voltage or the vibration current of the circuit is detected, and at least at the time of no load, the semiconductor switch element Q ₁ has a voltage at both ends. Is provided with a circuit that prohibits the separately excited signal from being input to the conduction control electrode of the semiconductor switch element Q ₁ .

That is, according to the present invention, at least when there is no load, a circuit that inhibits the conduction of the switch element Q ₁ even if the external excitation ON signal is generated during the period when the semiconductor switch element Q ₁ has the voltage across it. Since it is configured in this way, it prevents the power loss and temperature rise of the semiconductor switch element Q ₁ due to the rush current in the no-load state, and damages the semiconductor switch element Q ₁ . Can be prevented.

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. In this embodiment, a transistor is used as the semiconductor switch element Q ₁ , and the switch element voltage detection circuit A is a voltage division circuit using resistors R ₁ and R ₂ . The switch element voltage detection circuit A is connected to the resistor R _2.
Zener diode ZD for controlling the output of is connected in parallel. The output of the separately excited signal generator SG is NOT circuit G ₁
It is inverted at and is 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 . The output of NOR circuit G ₂ is drive transformer T
It is input via ₂ to the base of the control pole of transistor Q ₁ .

FIG. 2 is an operation explanatory diagram of this embodiment. Figure 2 (a)
The voltage V _CE across the switch element Q ₁ shown in (1) is detected by the switch element voltage detection circuit A, and a detection output as shown in FIG. And the detection output, the inverted output (Fig. 2 (c)) of the No. Other励信is input to the NOR gate G _2, the output drive signal of the switching element Q ₁ (FIG. 2 (d)).

The waveform shown in FIG. 2 (a) is
When the switch element voltage generation period is shorter than the cycle of the external excitation signal, and the external excitation signal indicated by the "Low" level period in FIG. 2C is generated during V _CE > 0. Even
The switch element Q ₁ does not conduct, and the drive signal of the switch element Q ₁ is only during the "High" level period in FIG. 2D.
The waveform shown in FIG. 2 (b) is when the constants such as L and C of the circuit are different and the switch element voltage generation period is longer than the cycle of the separately excited signal when there is no load.

As described above, in the period in which the voltage is applied to both ends of the semiconductor switch element Q ₁ , by inhibiting the switch element Q ₁ from conducting, it is possible to prevent the rush current from flowing.

Second Embodiment FIG. 3 is a circuit diagram of a main portion of another embodiment of the present invention, and shows only a control circuit portion. In the previous embodiment, the semiconductor switch element Q ₁ is prohibited from conducting only during the period when it has the voltage at both ends, whereas in the present embodiment, there is a possibility that the switching element Q ₁ may be generated while the switch element has the voltage at both ends. Conduction of the switch element Q ₁ is prohibited for the entire period of the excitation ON signal.

In the control circuit of FIG. 3, the output of the separately excited signal generation circuit SG and the output of the switch element voltage detection circuit A are AND circuits G
₃ and NOR circuit G ₄ respectively. AND circuit G
The output of ₃ is connected to the set input S of the RS flip-flop FF _1, the output of NOR circuit G ₄ are connected to the reset input R of the RS flip-flop FF _1. The output of the separately excited signal generation circuit SG and the output of the RS flip-flop FF ₁ are AND circuits.
It is entered in G ₅ . The output of the AND circuit G ₅ is input to the control pole of the semiconductor switch element Q ₁ via the drive transformer T ₂ . In this embodiment, as the main circuit for lighting the discharge lamp, the same circuit as in the previous embodiment is used.

FIG. 4 is an operation explanatory diagram of this embodiment. Figure 4 (a)
The voltage V _CE across the switch element Q ₁ shown in (1) is detected by the switch element voltage detection circuit A, and a detection output as shown in FIG. And the detection output, the other励信No. (Fig. 4 (c)) are inputted to the AND circuit G _3, resulting set input S (FIG. 4 (d)) of the RS flip-flop FF ₁ and. Therefore, the set input S becomes "High" level when the detection output of the switch element voltage detection circuit A is "High" level and the separately excited signal is "High" level. On the other hand, the same two signals (Fig. 4 (b) and (c)) that were input to the AND circuit G ₃ are input to the NOR circuit G ₄ and RS
The reset input R (FIG. 4 (e)) of the flip-flop FF ₁ is generated. Therefore, the reset input R is "Hi" when the detection output of the switch element voltage detection circuit A is "Low" level and the external excitation signal is "Low" level.
gh "level. By inputting the set input S and the reset input R to the RS flip-flop FF ₁ , an output as shown in FIG. 4F is obtained. AND with the separately excited signal (Fig. 4 (c))
By inputting to the circuit G ₅ , a drive signal (FIG. 4 (g)) is obtained. This drive signal does not become "High" level during the period of the separately excited ON signal generated during the period of V _CE > 0. Therefore, in the present embodiment, the switching element Q ₁ has the voltage across the both ends. For the entire period of the separately excited ON signal that occurs in the period
The conduction of the switch element Q ₁ will be prohibited.

In addition, when the discharge lamp is normally connected, the switch element voltage generation period is set to be shorter than the off period of the external excitation signal during both preheating and lighting. The excitation ON signal is not prohibited and continues to oscillate according to the other excitation signal.

Embodiment 3 FIG. 5 is a circuit diagram of still another embodiment of the present invention. In the present embodiment, the circuit for detecting the period in which the semiconductor switch element Q ₁ has the voltage across both ends is different, and when the switch element voltage becomes zero, the diode connected in antiparallel to the switch element Q ₁ The generation period of the switch element voltage is detected by utilizing the oscillating current flowing in D ₁ .

In the circuit of FIG. 5, the output of the separately excited signal generation circuit SG is
It is inverted by the NOT circuit G ₁ and input to the OR circuit G ₆ through the delay circuit CR ₁ . The other excitation signal from the other excitation signal generation circuit SG is directly input to the other input of the OR circuit G ₆ . The output of the OR circuit G ₆ is input to the NOR circuit G ₇ . The current flowing in the diode D ₁ is detected by the current transformer CT and a detection voltage is generated in the resistor R ₃ . This detection voltage is used as the reset input R of the RS flip-flop FF ₂ and the NOR circuit
It is entered in G ₇ . The other input of NOR circuit G ₇ is OR
The output of circuit G ₆ is input. The output of NOR circuit G ₇ is R
It is used as the set input S of the S flip-flop FF ₂ . RS
The Q output of the flip-flop FF ₂ is input to the NOR circuit G ₂ as the detection output of the switch element voltage detection circuit A. The output of the NOT circuit ₁ G is input to the other input of the NOR circuit G ₂ . The output of NOR circuit G ₂ is drive transformer T
It is input to the control pole of the semiconductor switch element Q ₁ via ₂ .

FIG. 6 is a diagram for explaining the operation of this embodiment. Figure 6 (a)
Shows the waveform of the switch element voltage when there is no load. When other励信No. (FIG. 6 (b)) is in the "High" level, the output of the NOT circuit G ₁ becomes "Low" level, the output of the delay circuit CR ₁ than this little delay to "Low" It becomes a level. When the external excitation signal switches to the "Low" level, the output of the delay circuit CR ₁ goes to the "High" level with a slight delay after this.
During this delay time, each input of the OR circuit G ₆ is at “Low” level, so the output of the OR circuit G ₆ is at “Low” level only during this period, as shown in FIG. 6C. Become. Since the output of the OR circuit G ₆ temporarily becomes “Low” level, the NOR circuit ₇
Output becomes "High" level for a while, RS flip-flop FF ₂ is set, and its Q output (Fig. 6 (e)) becomes "H".
Since the Q output of the RS flip-flop FF ₂ is the detection output of the switch element voltage detection circuit A, during the period when this Q output is at the “High” level,
Even if the separately excited ON signal (FIG. 6 (B)) is generated, the drive signal (FIG. 6 (F)) is not generated. Next, when the switch element voltage becomes zero and the diode current (Fig. 6 (d)) flows, the reset input R of the RS flip-flop FF ₂ becomes "H".
IgH "a level. In this case, one input of the NOR circuit ₇ is""Because the level, the output of the NOR circuit ₇ is" High Low "
And the set input S is set to "Low" level.
Therefore, RS flip-flop FF ₂ is reset,
The Q output becomes "Low" level. When the separately excited ON signal (FIG. 6 (B)) is generated during this period, the drive signal (FIG. 6 (F)) is generated. That is, in this embodiment, the falling time of the separately excited ON signal is regarded as the rising time of the switch element voltage, the RS flip-flop FF ₂ is set, and the rising time of the diode current is regarded as the zero return time of the switching element voltage. , RS flip-flop FF ₂
Is reset, and the Q output of the RS flip-flop FF _{2 is used} as the detection output of the switch element voltage.

In each of the above embodiments, since the switch element voltage or the diode current is constantly detected, it is possible to prevent the rush current from flowing to the semiconductor switch element Q ₁ even in a transient state such as when the discharge lamp is attached or detached. It is possible.

(Effects of the Invention) As described above, in the present invention, in the resonance type separately excited inverter circuit, the vibration voltage or the vibration current of the circuit is detected, and the voltage is applied to the semiconductor switch element at least when there is no load. Even if an external excitation signal that turns on the semiconductor switch element is generated during the period, a circuit that prohibits conduction of the switch element is provided, so that power loss and temperature rise of the semiconductor switch element due to rush current occur. This has the effect of preventing this and preventing damage to the semiconductor switch element.

[Brief description of 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 of the same, FIG. 3 is a main part circuit diagram of another embodiment of the present invention, and FIG. Is an explanatory diagram of the same operation as above, and
FIG. 6 is a circuit diagram of still another embodiment of the present invention, FIG. 6 is an operation explanatory diagram of the above, FIG. 7 is a circuit diagram of a conventional example, FIG. 8 is an operational explanatory diagram of the same, and FIG. It is a circuit diagram of a prior art example. 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 a separate excitation signal generation circuit, A is a switch element voltage detection circuit, CT is a current transformer, G ₂ is a NOR circuit, 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 is in a resonance state with the inductance element, a separate excitation signal generation circuit that repeatedly controls conduction of the semiconductor switching element, and a discharge lamp to which a resonance voltage generated by turning the semiconductor switching element on and off is applied via a stabilization element. Including, and in an inverter circuit in which the natural vibration frequency at the time of no load is lower than that at the time of lighting the discharge lamp, the vibration voltage or the vibration current of the circuit is detected, and at least at the time of no load, the period in which the semiconductor switching element has the voltage across the end A circuit is provided to prohibit the external excitation signal from being input to the conduction control pole of the semiconductor switch element. The discharge lamp lighting device according to claim Rukoto.