JPH06132091A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent a filament from its ignition at the time of nonlighting by detecting only an output current reduced at the time of abnormality of lamp nonlighting or the like. CONSTITUTION:At the time of normal lighting, voltage VR5 generated in a resistor R5 obtains an AC component waveform of the voltage detected with positive/negative almost symmetrical. A detection level Vr1 of a comparator CP1 is set to a VR5 peak at the time of normal lighting to provide a setting limit level. This level is decreased low as compare with the conventional detection level Vr1. When an electric discharge lamp 1a is not lighted, since a resonance current flows in a capacitor C2, choke coil L2, transistor Q1 and the capacitor C2, choke coil L2, capacitor C1, a current iR4 flowing in a resistor R4 is increased. Further, a current of positive/negative almost symmetry flows in the resistor R4. Here is performed control so as to obtain a relation where VR5peak = Vr1, but since an iR4peak ( iL peak) is decreased low as compared with the conventional example, a load current is reduced from the conventional example.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for lighting a discharge lamp such as a fluorescent lamp at a high frequency. More specifically, it is used when the discharge lamp reaches the end of its life or when an abnormality such as a defect occurs. The present invention relates to a discharge lamp lighting device including a protection circuit.

[0002]

2. Description of the Related Art Inverter devices are used in discharge lamp lighting devices for lighting discharge lamps at high frequencies. A discharge lamp lighting device of this type is shown in FIG. This discharge lamp lighting device uses a one-stone inverter, and connects a direct current power source E to a transistor Q ₁ in which a diode D ₁ is connected in antiparallel via a parallel circuit of a capacitor C ₁ and a choke coil L _1. In addition, a series circuit of the discharge lamp la and the choke coil L ₂ is connected in parallel at both ends of the parallel circuit.

[0003] Then, Yes and the current transformer CT ₁ which is inserted in series with the choke coil L ₂ so as to supply a base current to turn the transistor Q _1, configured to turn off the transistor Q ₁ in the output of the control circuit 1 Has become. In this discharge lamp lighting device, the transistor Q ₁ is turned on / off by the current transformer CT ₁ and the control circuit 1 to generate an oscillating current in the resonance circuit including the choke coils L ₁ and L ₂ and the capacitors C ₁ and C _2. As a result, the DC power supplied from the DC power supply E is converted into high frequency power, and this high frequency power is supplied to the discharge lamp la for high frequency lighting.

The capacitor C ₂ connected in parallel to the discharge lamp la functions as a preheating capacitor for supplying a preheating current to the filament when the discharge lamp la is started, and the start necessary for starting the discharge lamp la. It has a function of applying a voltage, and after the discharge lamp la is turned on, the impedance of the discharge lamp la is lowered, so that the current flowing through the capacitor C ₂ is reduced.

The control circuit 1 is provided with a capacitor C ₅ which is charged by a control power supply Vcc through a resistor R _6, and the voltage across the capacitor C ₅ is compared with a reference voltage Vref by a comparator CP ₂ so that a transistor Q The ON period of ₁ is determined, and the capacitor C
Charging and discharging of ₅ is adapted to be controlled in a conducting state of the transistor Q _4, Q _5.

That is, in the control circuit 1, the current
Lance CT₁Output voltage V_CTFrom when the positive voltage
Capacitor C_FiveStart charging the capacitor C_Five
When the voltage across both ends exceeds the reference voltage Vref, the output
When it goes to L level, the transistor Q₁Turn off
To work. Now, something is wrong with the lamp
Occurs, as shown in (b) of FIG.
Star Q₁If an overcurrent flows into the comparator circuit 3,
Parator CP ₁Output becomes H level, which causes
Register Q₃Turns on as shown in (f) of (b) in the figure.
And capacitor C₃By shorting the voltage across both ends of
The reference voltage Vref is pulled as shown in (d) of FIG.
As a result, as shown in (c) of Figure (b),
Transistor Q₁ON period is shortened,
Overcurrent is prevented from flowing.

[0007] At this time, although the state of the current iQ ₁ current iQ ₁ peak = Vr flowing through the resistor R ₄ (detection level of the comparator CP ₁₎ is to be suppressed, the detection level Vr
Is large, the temperature rise of the component parts becomes high, which may lead to a failure. Therefore, it is desirable to make the detection level Vr as low as possible. However, it is obvious that it cannot be made lower than the iQ ₁ peak at the time of normal lighting in (a) of FIG. 9, and the iQ ₁ peak (at the normal time) is the detection level Vr.
Is the limit of setting.

Another conventional example is shown in FIG. This circuit operates in the same way as in FIG. 8, but differs from that in FIG. 8 in that the waveform of the current iR ₄ appears continuously because the way of connecting the capacitor C ₁ is different. That is, when the transistor Q ₁ is on, iQ ₁ = iR ₄ , and when the transistor Q ₁ is off, iC ₁ (oscillating current) + iD ₁ = iR ₄ . Therefore, iR ₄ = iQ ₁ + iC ₁ + iD ₁
The current of the inverter circuit can be detected by the voltage across the resistor R ₄ .

During normal lighting, the transistor Q₁On
Sometimes DC power supply E → discharge lamp la → choke coil L₂
→ Transistor Q₁Current flows in the order of
Q ₁When off, choke coil L₂And capacitor
C₁And resonate, and the oscillating current flows through the discharge lamp la. This
When the discharge lamp la is lit, the resonance energy
Is attenuated, the load current becomes positive-negative asymmetry
(See (a) of FIG. 11 (a)). On the other hand, the discharge lamp la
When lit, transistor Q₁DC power supply when
E → capacitor C₂→ Choke coil L₂→ Transis
Q₁Current flows in the order of, and transistor Q₁When off
Is the capacitor C₂, Choke coil L₂, Capacitors
C₁Resonates, and its oscillating current flows, but the discharge lamp la
The resonance energy has very little damping due to the flaws.
As shown in FIG. 11 (b) (a), the load current
Approaches positive and negative symmetry. That is, the negative current iL is large.
Become

A current waveform almost equal to this load current is observed at the current iR ₄ (see (a) in FIG. 11B). How to set as low as possible detection level Vr ₁ of the comparator CP ₁ is similar to FIG. 8, it is advantageous for protection when not in point, the limit level is a iR ₄ peaks (normal). Even if the detection level Vr ₁ is set to the above limit level, the load current cannot be sufficiently narrowed down because the negative side of iL increases as shown in FIG.

[0011]

[0007] FIG. 8, in any of FIG. 10, the limit level setting of the Vr and Vr _1, Vr, be set Vr _1, when the lamp is not a point, the output current iL ₁ However, there is a problem in that the filament of the discharge lamp la is red-heated and the temperature of the lighting fixture structure rises, and the temperature of the inverter component parts rises due to the rise in temperature inside the fixture.

[0012] Therefore, there are restrictions on the design of the luminaire, which hinders the miniaturization of the luminaire. Further, in order to solve these problems, instead of the transistor Q ₃ of the switch circuit 4 configured by the transistor Q ₃ of FIG.
As shown in FIG. 12, a latch circuit using a thyristor SCR or the like is used to turn on the thyristor SCR by the output of the comparison circuit 3 in the case of a lamp failure and hold the state in which the reference voltage Vref is lowered to the discharge lamp la. Although a method of keeping the output current of the device kept low is also used, there is a new problem that the latch circuit is likely to malfunction due to noise or the like.

In the case of using the latch circuit, when malfunctioning due to external noise or surge, the power is turned off and then turned on again in order to make the lamp light normally, that is, to eliminate the output down (light off) state. Must throw in. The present invention is provided in view of the above points, does not detect in a normal state, detects only the output current at the time of an abnormality such as a lamp defect, and restricts the output current to reduce the red heat of the filament at the time of the defect. (EN) An inverter device which is intended to prevent, improve the degree of freedom of equipment design, facilitate design for downsizing, and improve noise resistance.

[0014]

According to the present invention, an inverter circuit for converting a direct current power source into high frequency power to supply power to a discharge lamp by turning on / off a switching element, and a peak value of an output current of the inverter circuit. A current detection circuit for detecting and a suppression means for suppressing the output current by controlling the ON period of the switching element by the output of the current detection circuit are provided, and the output current becomes positive-negative asymmetry during normal lighting, and when there is no point. In a discharge lamp lighting device having a substantially positive and negative symmetry, a conversion unit that makes the detection output of the output current substantially positive and negative symmetric is provided, and at least one of the positive and negative peak values of the output current from the conversion unit is detected to detect the output current. The output current is suppressed by the suppression means.

In the second aspect, there is provided means for inhibiting the operation of the suppressing means for detecting the peak value of the output current for a certain period at the time of starting the discharge lamp.

[0016]

According to the present invention, by detecting the peak value of the output current, which is substantially symmetrical between positive and negative, and controlling the switching element, the output current at the time of a spot can be narrowed down, and The filament temperature does not rise excessively at the end of the lamp life, and the outer shell of the lighting fixture is not thermally deformed or melted. Therefore, the lighting fixture can be designed in a smaller size, and the degree of freedom in design is improved. Further, since the temperature rise of the filament portion of the discharge lamp is suppressed, the amount of heat generated inside the fixture is reduced, and the temperature of the components that make up the lighting device is also lowered. Therefore,
Design for smaller size is possible. Furthermore, it is not necessary to use the conventional holding circuit (latch circuit) because the circuit that narrows down the output current by detecting that the output current has become abnormal when there is a fault, etc. Even if a surge or a surge enters the circuit and the suppressing means operates to limit the output current, when the external noise or surge disappears, the normal lighting is automatically restored. Therefore, it is not necessary to turn off the power and then turn it on again in order to eliminate the output down (light off) state as in the conventional case.

Further, according to the present invention, the means for inhibiting the operation of the suppressing means for detecting the peak value of the output current is provided only for a certain period at the time of starting the discharge lamp, so that the discharge lamp can be reliably started. It can be performed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 shows the first embodiment, and the entire configuration of the discharge lamp lighting device is the same as that of the conventional circuit shown in FIG. But,
In the present embodiment, the configuration of the current detection circuit 5 is different from the conventional one, and a series circuit of a capacitor C ₆ and a resistor R ₅ is connected in parallel with the resistor R ₄ and the output current of the output current is changed via the capacitor C ₆ . The AC component is detected, and this detection signal is sent to the comparator CP.
It is what you are typing in ₁ .

Since the operation of the entire circuit is the same as the conventional one, the description thereof is omitted and the essential part will be described in detail. Incidentally, FIG.
(A) shows the waveform at the time of normal lighting, and (B) shows the waveform at the time of astigmatism. First, in the normal time of lighting of the discharge lamp la, current iR ₄ flowing through the resistor R ₄ is, iR ₄ ≒ iQ ₁ +
iC ₁ + iD ₁ (however, R ₄ << R ₅ ), and at the time of normal lighting, it has a positive / negative asymmetric waveform as shown in (a) of FIG.

However, the capacitor C of the current detection circuit 5₆
Through the resistor R_FiveGenerated voltage V _R5Is its AC component
It becomes a waveform, and as shown in (b) of FIG.
It is detected in a substantially symmetrical manner. Comparator CP₁Detection of
Level Vr₁Is V at the normal lighting, which is the set limit level.
_R5It is set to peak. This level is shown in Figure 10.
Conventional detection level Vr₁It is lower than

Here, when the discharge lamp la becomes defective, the capacitor C ₂ , the choke coil L ₂ , the transistor Q ₁ and the capacitor C ₂ , the choke coil L ₂ , the capacitor C are provided.
_Since the resonance current of ₁ flows, the current iR flowing through the resistor R _4
4 increases, and as shown in FIG. 2B, (a), a substantially positive / negative symmetrical current flows through the resistor R ₄ . At this time, the control is performed so that V _R5 peak = Vr ₁ , but the iR ₄ peak (≈iL peak) is lower than that of the conventional example, so the load current is narrowed down as compared with the conventional example.

(Embodiment 2) FIG. 3 shows Embodiment 2 in which a current transformer CT ₂ is used directly instead of the AC component detection circuit using the capacitor C ₆ and the resistor R ₅ of Embodiment 1 described above. The output current is detected. Since this current transformer CT ₂ is used, the output current on the secondary side of the current transformer CT ₂ and the detection voltage V _R7 generated in the resistor R ₇ are substantially positive and negative symmetrical, and the same operation and effect as those of the first embodiment. Can be obtained.

(Embodiment 3) Embodiment 3 is shown in FIG. In the present embodiment, a differential circuit is constructed by the operational amplifier OP ₁ , the capacitor C ₆ and the resistor R ₅ in the current detection circuit 5 of the embodiment 1 shown in FIG. 1 to detect the output current. Here, the output voltage V ₀ of the operational amplifier OP ₁ is expressed by the following equation.

V ₀ = -CR (dV _R4 / dt) (Example 4) Example 4 is shown in FIG. This embodiment is shown in FIG.
The timer circuit 6 is added to the embodiment of FIG. As described above, it is advantageous to set the detection level Vr ₁ of the comparison circuit 3 as low as possible in terms of protection performance in the case of a lamp failure, but in that case, the detection level Vr _{1 is set.}
There is a case in which the setting voltage of is too low and the starting voltage required to start the discharge lamp la is not sufficiently obtained. Especially when the ambient temperature is low such as 0 ° C, the discharge lamp l
The case where a cannot be lighted occurs.

Therefore, in the present embodiment, the timer circuit 6 is provided so that, as shown in FIG.
By prohibiting the output of the comparison circuit 3 by ₁ and obtaining a sufficient output current, the starting voltage generated in the capacitor C ₂ is increased to ensure a reliable lamp start. (Fifth Embodiment) FIG. 7 shows a fifth embodiment in which the inverter circuit of the second embodiment is replaced with the one-stone type by adding a transistor Q _{10 and the} like into a half-bridge type, and the operation is performed. The description is omitted because it is similar to the example.

[0026]

As described above, according to the present invention, an inverter circuit for converting a DC power supply into high frequency power to supply power to a discharge lamp by turning on / off a switching element, and a peak value of an output current of the inverter circuit. A current detection circuit for detecting and a suppression means for suppressing the output current by controlling the ON period of the switching element by the output of the current detection circuit are provided, and the output current becomes positive-negative asymmetry during normal lighting, and when there is no point. In a discharge lamp lighting device having a substantially positive and negative symmetry, a conversion unit that makes the detection output of the output current substantially positive and negative symmetric is provided, and at least one of the positive and negative peak values of the output current from the conversion unit is detected to detect the output current. Since the output current is suppressed by the suppression means, the switching element is detected by detecting the peak value of the output current, which is approximately positive and negative. It is possible to reduce the output current at the time of astigmatism, and the filament temperature does not rise excessively at the time of the astigmatism or at the end of the lamp life. It does not occur. Therefore, the lighting fixture can be designed in a smaller size, and the degree of freedom in design is improved.
Further, since the temperature rise of the filament portion of the discharge lamp is suppressed, the amount of heat generated inside the fixture is reduced, and the temperature of the components that make up the lighting device is also lowered. Therefore, it is possible to design for further miniaturization. Furthermore, it is not necessary to use the conventional holding circuit (latch circuit) because the circuit that narrows down the output current by detecting that the output current has become abnormal when there is a fault, etc. Even if a surge or a surge enters the circuit and the suppressing means operates to limit the output current, when the external noise or surge disappears, the normal lighting is automatically restored. Therefore, there is an effect that it is not necessary to turn the power off and then on again in order to eliminate the output down (light off) state as in the conventional case.

Further, according to the present invention, the means for inhibiting the operation of the suppressing means for detecting the peak value of the output current is provided only for a certain period at the time of starting the discharge lamp, so that the discharge lamp can be reliably started. It can be performed.

[Brief description of drawings]

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

FIG. 2 is an operation waveform diagram when the above discharge lamp is normally lit and when there is no point.

FIG. 3 is a specific circuit diagram of the second embodiment of the above.

FIG. 4 is a specific circuit diagram according to the fourth embodiment of the above.

FIG. 5 is a specific circuit diagram of the fifth embodiment of the above.

FIG. 6 is an operation explanatory diagram of the above.

FIG. 7 is a specific circuit diagram of the fifth embodiment of the above.

FIG. 8 is a specific circuit diagram of a conventional discharge lamp lighting device.

FIG. 9 is an operation waveform diagram when the above discharge lamp is normally lit and when there is no point.

FIG. 10 is a specific circuit diagram of another conventional example.

FIG. 11 is an operation waveform diagram when the above discharge lamp is normally lit and when there is no point.

FIG. 12 is a circuit diagram showing another example of the above switch circuit.

[Explanation of symbols]

1 Control Circuit 3 Comparison Circuit 4 Switch Circuit 5 Current Detection Circuit 6 Timer Circuit E DC Power Supply Q ₁ Transistor la Discharge Lamp

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshikazu Hongo 404-1 Nishinosue, Himeji City, Hyogo Prefecture Ikeda Electric Co., Ltd.

Claims (2)

[Claims] 1. An inverter circuit for converting a direct current power source into high frequency power to supply power to a discharge lamp by turning on / off a switching element, a current detection circuit for detecting a peak value of an output current of the inverter circuit, and A discharge lamp that has positive and negative asymmetry when the output current is normal lighting and has positive and negative asymmetry when there is no point, and a suppression unit that controls the ON period of the switching element by the output of the current detection circuit to suppress the output current The apparatus is provided with a conversion unit that makes the detected output of the output current substantially symmetrical in positive and negative, detects at least one of the positive and negative peak values of the output current from the conversion unit, and suppresses the output current by the suppression unit. Discharge lamp lighting device characterized in that. 2. The discharge lamp lighting device according to claim 1, further comprising means for prohibiting the operation of the suppressing means for detecting the peak value of the output current only for a certain period when the discharge lamp is started.