JP2810677B2 - Discharge lamp lighting device - Google Patents

Description

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

[Related Art] FIG. 8 shows a conventional discharge lamp lighting device of this type. The discharge lamp lighting device is using one stone inverter 1, turns on the switching element Q ₁ by the control circuit 2, and off, the voltage of the DC power source E is converted into high-frequency voltage, and applies the high-frequency voltage to the lamp L To turn on the lamp L.

When this discharge lamp lighting device is turned on switching elements Q ₁ is as shown in Figure No. 9 (a), through the serial circuit and the choke coil L ₁ of the lamp L and the choke coil L _2, as shown in (d) of FIG. current flows through the switching element Q _1. When the switching element Q ₁ is turned off, the choke coil
L _1, the energy stored in L ₂ current flows into the capacitor C _1. In the case of the choke coil L ₂ current the shaded portion shown in part section b of Figure No. 9 (b) flows into the capacitor C _1. The capacitor C charges accumulated in ₁ is discharged to the series circuit of the choke coil L ₂ and the lamp L as indicated by the hatched portion B of FIG. 9 (b). In this way, a vibration circuit is formed by the capacitor C ₁ , the choke coil L ₂ and the lamp L, and a high-frequency vibration current flows through the lamp L. Here, the inductance value of the choke coil L ₁ is L ₁ ≫L ₂
Therefore, the influence on the vibration circuit is small. That is,
Choke coil L _1, since DC-impedance to the series circuit of the choke coil L ₂ and the lamp L is small, the DC component flowing through the choke coil L _1. The capacitor C ₂ connected in parallel to the lamp L is intended to preheat the filament of the lamp L, also the diode D ₁ is a diode for reflux.

The lamp L is a cathode preheating discharge lamp, and at the end of its life, the emitter (thermo-electron emitting material) applied to the filament scatters. As a result, when the emitter on one side is lost, thermions are not emitted from one filament. With such use of the lamp L which emitter is depleted saturated choke coil L ₂ due to the increased DC current flowing in the lamp L, or by magnetic bias of the choke coil L ₁ of the choke coil L ₁ causes saturation, the choke coil
L ₁ and L ₂ generate heat. Also, since the increase current flowing through the switching element Q _1, causing problems such as heat generation and damage the switching element Q _1.

Therefore, conventionally, there has been a method using a thermal protector for detecting the above-mentioned heat generation of the element and shutting off the power supply. However, this method has a drawback that the detection takes time.

In addition, as a method of detecting an abnormality of the lamp L as described above, there is a method of detecting a lamp voltage. In this method, when the lamp current flows in the forward direction of the lamp L in the half-wave discharge state, the lamp voltage becomes a voltage determined by the lamp tube voltage, and when the lamp current flows in the reverse direction, the lamp current becomes This is to utilize the fact that the voltage is blocked and becomes the voltage generated by the inverter 1, and the lamp voltage rises as compared with the lamp voltage in the normal state.

FIG. 10 shows a circuit equivalently showing a lamp L that has generated a half-wave discharge, and the lamp L can be equivalently represented by a resistor Rla and a diode Dla. Note that indicates the inverter 1 as an AC power source AC, there is shown a choke coil L ₂ as a current limiting impedance I. When a forward lamp current flows through the lamp L, the lamp voltage is the same as that of the normal lamp L. However, when the lamp current flows in the reverse direction, the lamp voltage rises to the voltage level of the AC power supply AC.

Here, in such a case, as a method of grasping the lamp voltage of the circuit of FIG. 8, there is a method of providing a transformer at both ends of the lamp L and detecting a secondary winding voltage of the transformer.
The reason why the transformer is used is that the earth line of the inverter 1 and the earth line of the detection voltage are made common since the lamp L is connected to the DC power supply E in the circuit of FIG. However, in this method, the cost of the transformer for detecting the lamp voltage increases, and the detection voltage may change depending on the position where the primary winding and the secondary winding of the transformer are wound. There are disadvantages.

Further, as another method of detecting an abnormality of the lamp L, as shown in FIG. 11, a series circuit of resistors R ₁ and R ₂ is connected in parallel to a series circuit of a choke coil L ₂ and a switching element Q _1. There is a method in which the voltage divided by the resistors R ₁ and R ₂ is used as a lamp voltage detection voltage.

In this method, since the potential Vc of the connection point between the lamp L and the choke coil L ₂ is (series power supply E- lamp voltage Upushironla), and detects the lamp voltage. When the lamp L shown in FIG. 12A is normal, the equivalent circuit of the lamp L can be represented only by the resistor Rla as shown in FIG. A symmetrical waveform with E at the center. However, Fig. 12 (b),
When the lamp L is in a half-wave discharge state as shown in (c),
The lamp voltage has an asymmetric waveform. Therefore, an abnormality of the lamp L can be detected from the lamp voltage waveform.

However, this method can be applied if the DC power supply E has a small voltage fluctuation, but this type of DC power supply E
Is obtained by rectifying and smoothing the commercial power supply, which is affected by the voltage fluctuation of the commercial power supply, and the ripple component is superimposed on the smoothed output depending on the size of the smoothing capacitor and the load. The above-described detection method has a problem that the abnormality of the lamp L cannot be accurately detected. For example, an abnormality may be erroneously detected for the normal lamp L, or the abnormality may not be detected in spite of the abnormal lamp L.

[Problems to be Solved by the Invention] The present invention has been made in view of the above points, and an object of the present invention is to accurately detect an abnormality in a lamp without being affected by a voltage fluctuation of a DC power supply. It is an object of the present invention to provide a discharge lamp lighting device capable of using a common inverter and a ground line.

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for smoothing a voltage obtained by cutting a direct current component from a voltage between an end of a lamp not connected to a direct current power element and a ground. To the capacitor of
A lamp abnormality detection circuit is provided that feeds back the lamp voltage smoothed by the smoothing capacitor to the control circuit of the inverter.

[Operation] According to the present invention, as described above, the lamp abnormality detection circuit cuts the DC component from the potential of the lamp that is not connected to the DC power supply element, and further detects and smoothes the lamp voltage.
By not being affected by the voltage fluctuation of the DC power supply, and by detecting the voltage between the end on the side not connected to the DC power supply element and the ground, the inverter and the ground line can be made common. It was made.

Embodiment 1 An embodiment of the present invention is shown in FIG. This embodiment inserts an application of the present invention to one stone inverter 1, a resistor R _1, a capacitor C ₃ for DC cut the series circuit of R ₂ in FIG. 11 circuit in the conventional example in series, the resistor R ₁ , by applying a divided voltage of the R ₂ to the capacitor C ₄ for smoothing through the rectifying diode D _2, the control circuit 2 of the voltage across the capacitor C ₄ inverter 1
Feedback.

In this embodiment, the DC cut capacitor C _{3 is connected} to the resistors R ₁ , R
Since ₂ and are inserted in series, it appears lamp voltage υla similar waveform swings positive and negative about the zero potential across the resistor R _2. The rise of the lamp voltage when in the half-wave discharge state in the rectifier diode D ₂ and the smoothing capacitor C ₄ to detect a positive voltage. In accordance with the output of the abnormality detection circuit 3, the control circuit 2 performs the conduction control of the switching element Q _1. The control of the control circuit 2, by shortening the ON period of the switching element Q _1, or down the output of the inverter 1, the on-switching elements Q _1, stop-off, the inverter 1
Or stop the oscillation operation. Thereby, heat generation of the element or heat generation and breakage of the switching element can be prevented. Moreover, since it is not necessary to detect the voltage between both ends of the lamp L with a transformer or the like, the abnormality detection circuit 3 has a small size and a simple configuration. Further, the detection accuracy is increased without being affected by the voltage fluctuation of the DC power supply E, and the lamp voltage can be detected by using the ground line in common with the inverter 1. In addition, according to the abnormality detection circuit 3, the non-lighting state of the lamp L can also be detected.

Embodiment 2 FIG. 2 shows another embodiment of the present invention. In this embodiment, an abnormality detecting circuit 3 for detecting a peak-to-peak voltage corresponding to a lamp voltage is provided. . In particular,
In parallel to the choke coil L ₂ and the series circuit of the switching elements Q _1, to connect the series circuit of the DC cut capacitor C ₃ and the resistor R _1, the capacitor C ₄ and the diode D ₃ to both ends of the resistor R ₁ Connect a series circuit, connect the voltage dividing resistors R ₃ and R ₄ across the diode D ₃ , connect the capacitor C ₅ across the resistor R ₄ , and connect the DC voltage of the capacitor C ₅ according to the lamp voltage. Is fed back to the control circuit 2.

In this embodiment, when the voltage across the resistor R ₁ is negative, it charges the capacitor C ₄ in the direction indicated by the arrow in Figure 2 through the diode D _3. Then, when the voltage across the resistor R ₁ is positive, the cathode voltage of the diode D ₃ is a negative peak voltage Vp charged in the capacitor C _{4 -} shifted in the positive direction only, thus across diode D ₃ is As shown in FIG.
Vp ₊ -Vp _- voltage of appears.

Even when this voltage is used, the abnormality of the lamp L can be detected in the same manner as in the first embodiment.

Embodiment 3 FIG. 4 shows still another embodiment. In this embodiment, the present invention is applied to a half-bridge inverter 1 '. The inverter 1 'applies a high-frequency voltage to a lamp L by alternately turning on and off switching elements Q ₁ and Q ₂ connected in series to a DC power supply E by a control circuit 2, and the lamp L is switched. at both ends of the element Q ₁ via the capacitor C ₁ and the choke coil L ₁ of the DC blocking are connected. Incidentally, has been charged charges charged in the capacitor C ₁ is used as a power source for supplying a lamp current during the on transistor Q _1. Further, diodes D ₁ and D ₂ are connected to the transistors Q ₁ and Q ₂ in antiparallel, respectively. The potential at the connection point between the lamp L and the choke coil L ₁ in the discharge lamp lighting circuit becomes (E-Vc ₁ -υla). Incidentally, Vc ₁ is charged charges of the capacitor C _1. Abnormality detection circuit 3 of this embodiment
Is a first embodiment the same configuration, for cutting the DC component in the capacitor C _3, the voltage similar to the lamp voltage appearing at both ends of the resistor R _2. As described above, the present invention can be applied to the half-bridge inverter 1 '.

FIG. 5 shows the half-bridge inverter 1 '.
Those having different connecting portions of the capacitor C ₁ in the discharge lamp lighting apparatus using. Lamp L and capacitor in this case
The potential at the connection point between the C ₁ is (E-υla). Also in this case, the abnormality of the lamp L can be detected by using the same abnormality detection circuit 3 as in the case of FIG.

Embodiment 4 FIG. 6 shows another half-bridge inverter 1 ″ according to the present invention.
This half bridge 1 ″ is connected to a series circuit of capacitors C ₁₁ and C ₁₂ at both ends of a DC power source E, and charges the capacitors C ₁₁ and C _{12 with} the charge of the capacitor C ₁₁ .
_The high-frequency current is supplied to the lamp L by discharging when the switching elements Q ₁ and Q ₂ connected in parallel to the switches ₁₁ and C ₁₂ are turned on. In the half-bridge inverter 1 ″, the switching elements Q ₁ and Q ₂ are alternately turned on and off, and the switching elements Q ₁ and Q 2
₂ There are two modes to be turned on. Therefore, the lamp L
7, a high-frequency voltage and a DC voltage are alternately applied, such as a high-frequency voltage during a _THF period and a _DC voltage during a _TDC period. Note that T in the figure indicates one cycle. Here, the switching frequency of the switching elements Q ₁ and Q ₂ is 2
0 to 100 kHz, and the period T is several msec to several tens msec. Also,
The choke coil L ₁ is used as a current limiting element and the capacitor C ₁
Is provided to bypass high frequency components. Even in the discharge lamp lighting apparatus using the half-bridge inverter 1 ", be connected to one abnormality detection circuit 3 in parallel to the series circuit of the choke coil L ₁ and the transistor Q _2, the configuration of the abnormality detecting circuit 3 is first This is the same as that of the embodiment.

By the present embodiment which constitutes a closed circuit of the capacitor C ₁₂ → the capacitor C ₁ (the lamp L) → abnormality detecting circuit 3 → capacitor C _12, detecting a voltage corresponding to a change in the lamp voltage υla from both ends of the capacitor C ₄ can do.

As described in each of the above embodiments, the present invention can detect the abnormality of the lamp L regardless of the type of the inverter 1.

[Effects of the Invention] As described above, the present invention applies a voltage obtained by cutting a DC component from a voltage between the end of the lamp not connected to the DC power supply element and the ground to a smoothing capacitor, and And a lamp abnormality detection circuit that detects a lamp voltage smoothed by a capacitor for use and feeds back a voltage corresponding to the lamp voltage to a control circuit of the inverter.
Since the lamp abnormality detection circuit cuts the DC component from the potential of the discharge lamp that is not connected to the DC power element, and detects the lamp voltage after smoothing, the DC voltage component from the DC power supply can be cut. It is not affected by the voltage fluctuation of the DC power supply, and by smoothing with a capacitor, a DC voltage corresponding to the peak value of the lamp voltage can be obtained. There is an effect that the voltage can be detected. Further, by detecting the voltage between the end on the side not connected to the DC power supply element and the ground, there is an effect that the inverter and the ground line can be shared.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of another embodiment, FIG. 3 is an operation explanatory diagram of the above embodiment, FIG. 4 is a circuit diagram of still another embodiment, FIG. 5 is a circuit diagram of an application example of the above, FIG. 6 is a circuit diagram of still another embodiment, FIG. 7 is an operation explanatory view of the above, FIG. 8 is a circuit diagram of a conventional example, and FIG. 10 is an equivalent circuit diagram when the lamp is abnormal, FIG. 11 is a circuit diagram of another conventional example, and FIG. 12 is an operation explanatory diagram of the same. 1,1 ', 1 "inverter, the second control circuit, 3 the lamp abnormality detection circuit, Q _1, Q ₂ is a switching element, L is a lamp.

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Akira Yamamoto 1048 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Works Co., Ltd. (72) Inventor Seiji Soga 1048, Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Works, Ltd. (56) References JP-A-1-2511591 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , (DB name) H05B 41/24

Claims (1)

(57) [Claims] A switching circuit is turned on by a control circuit.
In a discharge lamp lighting device that turns off the inverter to oscillate and turn on the lamp with the high frequency output of the inverter, the DC component is cut from the voltage between the end of the lamp that is not connected to the DC power supply element and the ground. A discharge lamp lighting device including a lamp abnormality detection circuit that applies the obtained voltage to a smoothing capacitor and feeds back the lamp voltage smoothed by the smoothing capacitor to a control circuit of an inverter.