JPH02172192A - Discharge lamp lightup device - Google Patents

Abstract

PURPOSE:To sense abnormality in a lamp accurately and use an inverter and a ground line commonly by performing sensing in such a fashion that the DC portion is cut from the voltage between the ground and the end on the off- connection side of lamp to a DC power supply element. CONSTITUTION:DC power E is converted into high frequency power by an inverter I, and thereby a lamp L is driven. The output of this inverter I is controlled by a control circuit 2, and the lamp voltage is sensed by a sensor circuit 3, and its output from sensing is fed to the control circuit 2. On the off-connection side of lamp L to the power supply element, a capacitor C3 for cutting the DC portion is connected in series to resistances R1, R2, and a voltage with similar waveform to the lamp voltage is generated at the ends of the resistance R2, and this output is fed to the control circuit 2 through a diode D2. This control input indicates abnormality in the lamp accurately regardless of varying power E. The ground line can be common with the inverter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a discharge lamp lighting device for lighting a lamp at high frequency using an inverter.

[Prior Art 1] A conventional discharge lamp lighting device of this type is shown in FIG. This discharge lamp lighting device uses a single-stone inverter 1, and a control circuit 2 turns on and off a switching element Q, converts the voltage of a DC power supply E into a high-frequency voltage, and applies this high-frequency voltage to the lamp. , which lights up the lamp L.

In this discharge lamp lighting device, when the switching element Q is turned on as shown in FIG. 13(a), the switching occurs as shown in FIG. 13(d) through the series circuit of the lamp L and choke coil L2 and the choke coil L1. Current flows through element Q1. When switching element Q1 is turned off, current flows into capacitor C1 due to the energy stored in choke coils L, , L, and in the case of choke coil L2, the current flows in the shaded area A in FIG. 13(b). flows into capacitor C1, this capacitor C3
The charges accumulated by WI are discharged into the series circuit of the choke coil L2 and the first lamp L, as shown by the hatched part in FIG. 13(b). In this way, capacitor C4, chip 5-
An oscillating circuit is formed by the coil L2 and the lamp L, and a high frequency oscillating current flows through the lamp L. Here, the inductance value of the Chirok coil L1 is 1. , , >) L
2, the influence on the vibration circuit is small. That is, since the choke coil L has a small DC impedance with respect to the series circuit of the choke coil L2 and the lamp L, the DC component flows through the choke coil. Incidentally, a capacitor C2 connected in parallel with the lamp L is used to preheat the filament of the lamp L, and a diode D is a reflux diode.

The above-mentioned lamp is a cathode preheating discharge lamp, and at the end of the special mission, the emitter (thermionic emitting material) coated on the filament begins to scatter. As a result, when one emitter disappears, thermoelectrons are no longer emitted from one filament. Lamp L without emitter like this
When this lamp is used, the saturation of the choke coil L2 due to an increase in the direct current flowing through the lamp L, or the saturation of the choke coil L2 due to the biased magnetization of the chillo twill L1 is caused, and the choke coils L and L2 generate heat. In addition, the switching element Q
Since the current flowing through switching element Q1 also increases,
This may cause problems such as heat generation and damage.

Therefore, conventionally there has been a method of using a thermal protector that detects the heat generation of the above-mentioned element and cuts off the power supply, but this method has the disadvantage that detection takes time.

Further, as a method for detecting abnormality of the lamp L as described above, there is a method of detecting the lamp voltage.

In this method, when the lamp current flows in the forward direction of the lamp L in a half-wave discharge state, the lamp voltage becomes a voltage according to the type of lamp, and when the lamp current flows in the reverse direction, the lamp current changes. This utilizes the fact that the lamp voltage is increased compared to the normal lamp voltage due to the voltage being blocked and generated by the inverter 1.

FIG. 14 shows a circuit equivalently showing a lamp L that has generated a half-wave discharge.
and a diode D1a. Note that the inverter 1 is shown as an alternating current power supply AC, and the choke coil L
2 is shown as current-limiting impedance ■. When a forward lamp current flows through this lamp, the lamp voltage is the same as that of the lamp L during normal operation. However, if the lamp current flows in the opposite direction, the lamp voltage will rise to the voltage level of the alternating current power supply AC.

Here, as a method of suppressing the lamp voltage of the circuit shown in FIG. 12 in such a case, there is a method of providing a transformer at both ends of the lamp L and detecting the secondary winding voltage of the transformer.

The reason why a transformer is used here is that in the circuit shown in Figure 12, the lamp L is connected to the DC power supply E, so the earth fin of the inverter 1 and the detection voltage 7-s2 in are used in common. be. However, with this method, the cost of the transformer for detecting the lamp voltage is high, and the detected voltage may change depending on the winding position of the primary and secondary windings of the transformer, making it difficult to manage variations in the transformer. There is a drawback.

Furthermore, as a method for detecting an abnormality in another lamp L,
As shown in FIG. 15, a series circuit of resistors R, R2 is connected in parallel to a series circuit of a Chirok coil L2 and a switching element Q, and this resistor RI.

There is a method of using the voltage divided by R2 as the detection voltage of the lamp voltage.

In this method, the potential Vc at the connection point between the lamp I- and the Tyroku twill L2 is (DC N source E-lamp voltage vj!a)
Therefore, the lamp voltage is detected. When the lamp L shown in Fig. 16 (A) is normal, the equivalent circuit of the lamp L can be expressed only by the resistor R1m as shown in Fig. 16 (A) (C), and therefore the waveform of the potential Ve is The waveform is symmetrical with E as the center. However, when the lamp L enters a half-wave discharge state as shown in FIGS. 16(b) and 16(c), the two lamp voltages have an asymmetrical waveform. Therefore, an abnormality in the lamp L can be detected from this lamp voltage waveform.

However, this method can be applied if the DC power source E has small voltage fluctuations, but since this type of DC power source E is obtained by rectifying and smoothing the commercial power source, it is affected by the voltage fluctuations of the commercial power source. Also, depending on the size of the smoothing capacitor and load, ripple components may be superimposed on the smoothed output.
There is a problem in that the voltage fluctuations are large, and therefore the above-described detection method cannot accurately detect an abnormality in the lamp L. For example, it may happen that an abnormality is erroneously detected even though the lamp is normal, or that it cannot be detected even though the lamp is abnormal.

[Problem to be Solved by the Invention 1] The present invention has been made in view of the above points, and its purpose is to accurately detect lamp abnormalities without being affected by voltage fluctuations of a DC power supply. It is an object of the present invention to provide a discharge lamp lighting device which can be used as a common inverter and a ground fin.

[Means for Solving the Problems J] In order to achieve the above object, the present invention applies a voltage between the end of the lamp that is not connected to the DC power supply element and the ground, and extracts the DC component from this voltage. A lamp abnormality detection circuit is provided which detects the lamp voltage by cutting the lamp voltage and feeds back a voltage corresponding to the lamp voltage to the control circuit of the inverter.

[Function] As described above, the lamp abnormality detection circuit detects the lamp voltage by cutting off the DC component from the potential of the unconnected side of the lamp to the DC power supply element, thereby reducing the influence of voltage fluctuations of the DC power supply. By detecting the voltage between the end that is not connected to the DC power supply element and the ground, it is possible to use a common ground line with the inverter. be.

[Embodiment 11] An embodiment of the present invention is shown in FIG. 1. This embodiment applies the present invention to a single-stone imperter 1, and is a series circuit of resistors R, , R, of the conventional circuit shown in FIG. 15. A capacitor C1 for DC cut is inserted in series with the capacitor C1 for DC cut, and the divided voltage of the resistors R, , R, is connected to the smoothing capacitor C1 via the rectifier diode D2.
The voltage across the capacitor C4 is fed back to the control circuit 2 of the inverter 1.

In this embodiment, the DC cut capacitor C3 is replaced with a resistor R,
, R2, there is a lamp voltage t/''l across both ends of the resistor R2 that swings positive and negative around zero potential.
A waveform similar to a appears. Note that when the lamp L is normal, an alternating current voltage with equal positive and negative average values appears on both layers of the resistor R2, and when a half-wave discharge occurs, a positive and negative asymmetrical waveform occurs.

Therefore, even if the rectifying diode D2 and the smoothing capacitor C4 detect voltage only in the positive direction as shown in FIG. 1, an abnormality in the lamp L can be detected regardless of the direction of the half-wave discharge. In response to the output of the abnormality detection circuit 3, the control circuit 2 controls the conduction of the switching element Q1.The control circuit 2 controls the output of the inverter 1 by shortening the ON period of the switching element Q. Squeeze or
The oscillation operation of the inverter 1 is stopped by stopping the switching element Q1 from turning on and off. Thereby, it is possible to prevent the element from generating heat or the switching element from generating heat and being damaged. Moreover, since there is no need to detect the voltage across the lamp 4 using a transformer or the like, the abnormality detection circuit 3 is small and has a simple configuration. Furthermore, it is not affected by voltage fluctuations of the DC power supply E, and the detection accuracy is increased. Furthermore, the lamp voltage can be detected by using the 7-sline in common with the inverter 1. Furthermore, this abnormality detection circuit 3
According to the invention, it is also possible to detect the unlit state of the lamp L.

[Embodiment 2] FIG. 3 shows another embodiment of the present invention. In this embodiment, the peak to peak voltage corresponding to the lamp voltage is
k) is equipped with an abnormality detection circuit 3 for detecting.
Specifically, a DC cut capacitor C1 is connected in parallel to the series circuit of the choke coil L2 and the switching element Q.
A series circuit consisting of a capacitor C1 and a diode D is connected across the resistor R1, and a series circuit consisting of a capacitor C1 and a diode D is connected across the resistor R1.

Voltage dividing resistors R, , R, are connected to both ends of the voltage dividing resistors R, , R, and the divided voltages of the voltage dividing resistors R, , R, are fed back to the control circuit 2 .

In this embodiment, when the voltage across the resistor R1 is negative, the capacitor C2 is charged in the direction shown by the arrow in FIG. 3 via the diode D1. When the voltage across the resistor R is positive, the cathode voltage of the diode D is shifted in the positive direction by the negative peak voltage Vp- charged in the capacitor C2. 4
The voltages v p++ v p− shown in FIG. 3(b) appear.

Even using this voltage, it is possible to detect an abnormality in the lamp L in the same way as in the first embodiment described above.

Incidentally, as shown in FIG. 5, a capacitor C1 may be connected to both ends of the resistor R1 to feed back a DC voltage corresponding to the lamp voltage to the control circuit 2.

Furthermore, there is a circuit shown in FIG. 6 as an application of the third leap circuit. In this abnormality detection circuit 3, the voltage across the resistor R2 is rectified by the rectifying diode D2, and the voltage across the resistor R2 is rectified by the rectifying diode D2.
) Extract the voltage when the voltage across the resistor R2 is negative,
This voltage is shifted to the positive side by a series circuit consisting of a capacitor C4 and a diode D to obtain the voltage shown in FIG. 7(b).

In this way, an abnormality in the lamp L can be detected using only a negative voltage.

[Embodiment 3] FIG. 8 further shows an embodiment of a pond in which the present invention is applied to a huff-shable inverter 1. This inverter 1° applies a high frequency voltage to the lamp by alternately turning on and off the switching elements Q, Q, connected in series to the DC power supply E in the control circuit 2. It is connected to both ends of the element Q via a DC cut capacitor C3 and a choke coil L. Note that the charge stored in the capacitor C8 is used as a power source for supplying a lamp current when the transistor Q is turned on. Also, the transistor Q, -
Diodes D, D2 are connected in antiparallel to Qz, respectively. The potential at the connection point between the lamp L and the choke coil L in this discharge lamp lighting circuit is (E-ve, t/”fa
), where Vc is the charge on the capacitor C. The abnormality detection circuit 3 of this embodiment has the same configuration as the first embodiment, and since the DC component is cut by the capacitor C, a voltage similar to the lamp voltage appears at both ends of the resistor R2. In this way, the present invention can also be applied to the push-pull inverter 1'.

By the way, FIG. 9 shows a discharge lamp lighting ifi using the above-mentioned push-pull inverter 1. In this case, the connection point of the capacitor C1 is different. In this case, the potential at the connection point between the lamp L and the capacitor C9 is (E-1f1m).

In this case as well, the abnormality detection circuit 3 similar to that shown in FIG. 8 can be used to detect an abnormality in the lamp L.

[Embodiment 41] Fig. 10 shows the application of the present invention to a bar 7 bridge inverter 1'', in which a series circuit of capacitors C, , C, 2 is connected to both ends of a DC power source E. , the charge in the capacitor 01□C12 is discharged by turning on each of the switching elements Q, , Q, which are connected in parallel to the capacitors C, , c, □, thereby supplying a high frequency current to the lamp. It is something. In addition, this bar 7
Switching element in Blitzno inverter 1". I v
There are two modes: one in which Q2 is alternately turned on and off, and the other in which only one of the switching elements Q, , Q, is turned on. Therefore, as shown in FIG. 11, a high frequency voltage and a DC voltage are alternately applied to the lamp, such as a high frequency voltage during the THF period and a DC voltage during the T'oc period. Note that T in the figure indicates one cycle. Here, the switching frequency of the switching elements Q, ,Q, is 2O-
100kHz, period T is several m5ec-several tens of 1sec
It is. In addition, the choke coil L acts as a current limiting element.
Further, the capacitor CI is provided to bypass high frequency components. Even in the discharge lamp lighting device using this bar 7 blink inverter 1'', an abnormality detection circuit 3 is connected in parallel to the series circuit of the Chirok coil L and the transistor Q2, and the configuration of this abnormality detection circuit 3 is as follows. It is the same as that of the first embodiment.

In this embodiment, capacitor C1□→capacitor C+ (t
By configuring a closed circuit of lamp L)→abnormality detection circuit 3→capacitor C32, a voltage corresponding to a change in lamp voltage 1fla can be detected from both ends of capacitor C1.

As explained in each of the above embodiments, the present invention provides an inverter 1
It is possible to detect an abnormality in the lamp L regardless of its type.

[Effect of the invention 1] As described above, the present invention applies a voltage between the end of the lamp that is not connected to the DC power supply element and the ground, and detects the lamp voltage by cutting off the DC component from this voltage. At the same time,
It is equipped with a lamp abnormality detection circuit that feeds back a voltage corresponding to this lamp voltage to the inverter control circuit, and the lamp abnormality detection circuit cuts the DC component from the potential on the side of the discharge lamp that is not connected to the DC power supply element. Since the lamp voltage is detected using the DC power source, the DC voltage component caused by the DC power source can be cut, and therefore the lamp voltage can be accurately detected without being affected by voltage fluctuations of the DC power source. 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 explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of the same operation as above, FIG. 3 is a circuit diagram of another embodiment, FIG. 4 is an explanatory diagram of the same as above, and FIG. A circuit diagram of the above application example, Fig. 6 is a circuit diagram of another application example, Fig. 7 is an explanatory diagram of the same operation, Fig. 8 is a circuit diagram of still another embodiment, and Fig. 9 is an application of the same example. A circuit diagram of an example, FIG. 10 is a circuit diagram of yet another embodiment, t
Figure ltJ11 is an explanatory diagram of the same operation as above, Figure 12 is a circuit diagram of the conventional example, Figure 13 is an explanatory diagram of operation of the same as above, Figure 14 is an equivalent circuit diagram when the lamp is abnormal as above, Figure 15 is another conventional example. The example circuit diagram, vJ16 diagram, is an explanatory diagram of the same operation as above. 1.1°, 1″ is the inverter, 2 is the control circuit, 3 is the lamp abnormality detection circuit, Q, , Q is the switching element, L1
It is an earthen lamp. Agent Patent Attorney Ishi 1) Ai Figure 7 Figure 3 Figure 1 Figure L...Lamp Figure 4 Figure 2 Figure 5 Illustrations (A) (B) (C) Figure 7 Figure 9 Figure 11 Procedures Written amendment (voluntary)

Claims (1)

[Claims] (1) In a discharge lamp lighting device that turns on and off switching elements by a control circuit to cause an inverter to operate in oscillation, and lights a lamp with the high frequency output of this inverter, the end of the lamp that is not connected to the DC power supply element and A discharge lamp that is equipped with a lamp abnormality detection circuit that detects the lamp voltage by cutting off the DC component from the voltage applied to the ground and feeding back the voltage corresponding to the lamp voltage to the inverter control circuit. lighting device.