JPS60208093A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to a discharge lamp lighting device.

Technical Background of the Invention and Problems Therein Generally, in a device for lighting a discharge lamp using an inverter circuit, it is desirable to sufficiently preheat the filament and perform a warm start.

FIG. 1 shows a conventional example. In a lamp circuit consisting of an AC power supply 1, an inverter circuit 2, an inverter transformer 3, and a discharge lamp 4, a filament 4a of the discharge lamp 4,
A switch element 5 is connected between 4b and 4b, and the filament is preheated by turning the switch element 5 on and off by a timer circuit 6 for a certain period of time after the power is turned on. However, when the secondary circuit is opened and closed by the switch element 5 in this manner, a high voltage withstand element is required as the switch element, resulting in high cost and large drive power.

This is because b+·E of the transistor becomes smaller. Furthermore, in this method, the preheating current is small and preheating takes time. In this regard, in order to increase the preheating current, a method has been considered in which a differential winding is provided on the secondary side of the inverter transformer and short-circuited with a switch element at startup, but this switch element is also a high voltage withstand voltage element of 600 to 800 V class. is required.

On the other hand, there is also a rapid method as shown in FIG.

In this method, the input voltage of the inverter circuit is adjusted or the oscillation mode is changed to lower the secondary output voltage and perform a warm start. However, as the secondary voltage decreases, the filament 1 voltage also decreases, making it impossible to preheat the filament sufficiently in a short period of time.

OBJECTS OF THE INVENTION The present invention has been made in view of the above points, and provides a discharge lamp lighting device that can perform warm start by sufficiently preheating the filament in a short time without adding stress to the switching elements of the inverter circuit. The purpose is to obtain.

Summary of the Invention The present invention preheats the filament using a preheating transformer, and applies a DC voltage for a certain period of time to a control winding provided on the secondary side of an inverter transformer using a DC bias circuit to apply DC magnetic flux to the secondary side. By doing so, the secondary side of the inverter transformer is saturated and the secondary voltage is lowered, and after preheating the filament in a short time while the discharge lamp is not lit, a warm start is performed to start the lamp and turn it on. It is configured as follows.

Embodiment of the Invention An embodiment of the present invention will be explained with reference to FIG. First, an inverter circuit 12 including an inverter transformer 11 is connected to the AC power source 10 . Both ends of the secondary winding N2 of this inverter transformer 11 are connected to filaments 13a and 13b of the discharge lamp 13.

Here, the inverter transformer 1] is a leakage transformer consisting of two E-shaped cores facing each other with a gap (by a spacer) interposed therebetween, with a negative winding N1 and a secondary winding N2.
It is mainly equipped with a bias winding N on the negative side.
II and a negative side control winding Nc+ are provided, and a control winding NC2 is provided on the secondary side. -Next side control winding N
C1 has the opposite polarity to the control winding N and 2, and the number of turns is set to be smaller.

Then, a preheating transformer 1 is provided for the discharge lamp ′)”3.
4 are provided. In this preheating transformer 14, the secondary side preheating windings Np a and Np b are the filaments 13
a, 13b, and the -order winding NFI is connected to the bias winding NB via a switch element controlled by a timer circuit 15, such as a bidirectional thyristor 16. On the other hand, the negative side control winding NC1, the control winding N
c2 are connected in series, and a DC bias circuit 17 is provided to apply a DC voltage between them. This DC bias circuit 17 shares the bias winding N11 for the preheating transformer 14 as a power source, and also shares the timer circuit 15 and the thyristor 16.

In addition, a diode 18, a capacitor 19 and a coil 20
It is configured by an HF filter 21 based on.

In such a configuration, when the power switch is turned on, the timer circuit 15 is activated and the thyristor lZ is turned off for a certain period of time.
Do N. As a result, the preheating transformer]4 operates using the bias winding Nu as a power source, and the filaments 13a and 13b
A preheating current flows through the

At this time, the secondary voltage of the secondary winding N2 of the inverter transformer 11 is decreasing. That is, with the thyristor 16 ON, the control winding NC is
A DC voltage is applied to 2. This allows the control winding N
This is because c2 applies DC magnetic flux to the secondary side of the inverter transformer 11, and this secondary side core becomes saturated.

In this way, the secondary voltage of the inverter transformer 11 does not drop and discharge does not occur, and the filament 13a
, 13b, a sufficient preheating current flows through the filament mino] 4 without dropping, so that the filament temperature rises in a short time.

Thereafter, the timer circuit 15 provides a constant 11. '1 interval is t
When the thyristor 16 turns off after Y, the control winding Ne
The DC bias for 2 is cut. Due to this, the secondary winding N2 of the inverter transformer 11 is connected to the secondary winding N2.
As a result, the secondary voltage (lamp applied voltage) becomes high and the filament 13a becomes steady.

13b is applied to turn on the discharge lamp 13. This is a warm start.
However, at this time, the preheating transformer 14 also ceases to function, and filament cutting is also performed at the same time. In other words,
According to this embodiment, warm start control and filament power cut control can be performed simultaneously by the thyristor 16, and power saving can be achieved simply without providing a separate filament power cut circuit. In addition, the switching elements such as this thyristor 16 have a withstand voltage of 100V.
It does not need to be a high-voltage element and is therefore inexpensive.Furthermore, since it does not change the oscillation mode of the inverter circuit 12, no stress is applied to the switching transistor.

By the way, at 8 o'clock in the staff, a DC voltage is applied to the primary side control winding Nc1 as well as the control winding Nc2 for a certain period of time, and this secondary side control winding NC1 applies a DC magnetic flux to the primary side of the inverter transformer 11. become. This DC magnetic flux is smaller than the DC magnetic flux due to the control winding Nc2,
And, t! t% property, and prevents saturation on the primary side of the inverter transformer 11. Therefore, when the magnetic flux density on the negative side is small, it is not necessary to provide the primary side control winding Nc1, but when the magnetic flux density is large, it is effective.

Here, the core loss of the inverter transformer 11 is
Even if the secondary side is saturated, it is due to the DC magnetic field.

Since the hysteresis loop is small, there is no big difference from when the light is on.

By the way, it is also possible to connect one end of the -order winding NI-1 directly to the bias winding NB without using the thyristor 16, as shown by the broken line in Figure 3, so that the filament can be preheated at all times. . This is effective when lighting the discharge lamp 13 in a controlled manner. That is, since the lamp current decreases during dimming lighting, by constantly preheating the filament, the cathode spot temperature, which affects the lamp life, is compensated for and kept approximately constant. In addition, with this method, the filament is constantly preheated even when the full light is on, so the dimming detection circuit,
By using a timer circuit, a switch element, etc., the filament may be preheated only at the start when the full light is turned on, or the filament may be preheated at all times when the light is dimmed.

Next, an example of application will be explained with reference to FIG. this is.

The control winding NC2 is used to control the lighting. Therefore, the variable resistor 23 is connected to the gate of the thyristor 16 via the OR gate 22 together with the timer circuit 15.
A pulse generator 24 whose duty is adjusted by is connected.

According to this, for a certain period of time after power is turned on, the timer circuit 15
The thyristor 16 is ONL under the control of 0; filament preheating operation described above, warm star 1 to operating force '4.
(At this time, even if a pulse signal is output from the pulse generator 24, the OR gate 22 gives priority to the timer output and has no effect.)

After the timer circuit 15 reaches tie 11, dimming lighting control is performed in accordance with the pulse output from the pulse generator 24. That is, during the pulse output period by the pulse generator 24, the thyristor 16 is turned ON again and the control winding N
A DC voltage is applied to C2, and the lamp applied voltage is lowered. However, during the pulse rest period of the pulse generator 24, the thyristor 10 is turned off, the DC bias of the control winding NC2 is cut, and the secondary voltage ( (lamp applied voltage) increases.

Therefore, by adjusting the duty with the variable resistor 23, the duty of the voltage applied to the lamp can be changed, and dim lighting can be performed. Moreover, when the lamp 01.l. is used, the preheating transformer 14 is turned on.

As a result, the cathode spot temperature can be stabilized with extremely low power consumption, and a good light control point illusion can be achieved.

Note 7. In FIGS. 3 and 4, a current limiting impedance such as a resistor, inductance, capacitance, etc. may be connected in series with the diode 18.

Effects of the Invention As described above, the present invention applies a DC voltage to the control winding provided on the secondary side of the inverter transformer for a certain period of time using a DC bias circuit, and applies DC magnetic flux to the secondary side. Since the filament is preheated using preheating transformers while the filament is saturated and its secondary voltage is reduced, a sufficient preheating current can be passed without reducing the filament voltage. It is possible to raise the filament temperature over time. Therefore, it is possible to perform a warm start without applying stress to the switching transistor of the inverter circuit or using a high voltage switch element. Since the primary side control winding is provided, even if the magnetic flux density on the negative side is large, saturation can be prevented and normal operation can be performed.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional example, FIG. 2 is a circuit diagram showing a different conventional example, and FIG. 3 is a circuit diagram showing an embodiment of the present invention.
FIG. 4 is a circuit diagram showing an application example. 11... Inverter transformer, I3... Discharge lamp, 1
4... Preheating transformer, 17... DC bias circuit, N2... Secondary winding, Nu... Bias winding, Nc
l -Next side control winding, NC2...Control winding Application Person: Toshiba Electric Materials Corporation

Claims (1)

[Scope of Claims] 1. An inverter I-lance to which a discharge lamp is connected to the secondary winding is provided, a bias winding is provided on the primary side of this inverter transformer, and a DC magnetic flux stamp is provided on at least the secondary side.
A DC bias circuit includes a preheating transformer that uses the bias winding as a power source to preheat the filament of the discharge lamp, and applies a DC voltage to the control winding for a certain period of time after power is turned on. A discharge lamp lighting device characterized by being provided with. 2. The discharge lamp lighting device according to claim 1, wherein the bias winding is also used as a power source for a DC bias circuit. 3. The inverter transformer has a primary control winding on the primary side of the inverter transformer to which a DC voltage is applied to the control winding by a DC bias circuit and which applies a DC magnetic flux smaller than the DC magnetic flux due to the control winding and of opposite polarity. A discharge lamp lighting device according to claim 1.