JPS60207290A - One-element inverter 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 the Invention The present invention relates to a blocking oscillation type inverter for lighting a discharge lamp.

Technical Background of the Invention and Problems Thereof Generally, in a discharge lamp lighting device that uses an inverter to light a discharge lamp, a warm start is desired in which the filament is sufficiently preheated at the time of startup before lighting.

Figure 1 shows a rapid type discharge lamp lighting device.
A primary winding N1 of an inverter transformer 4 is connected to an AC power supply 1 via an inverter circuit 3 having a switching circuit 1 and a run transistor 2, and a discharge lamp 5 is connected to a secondary winding N2.
is connected, and a part of it is connected to the filament winding Np 1
, N 112 and connected to filaments 5a and 5L+. This field name, output voltage, i.e. secondary winding N2
If the voltage applied to the lamp is too high, the filament 5d,
A cold start occurs in which the discharge lamp 5b is discharged and lit before it is preheated, damaging the filaments 5a and 5b. Therefore, in order to perform a warm start, it is necessary to lower the output voltage to such an extent that the discharge lamp 5 does not light up. As a means for this, there is a method of lowering the output voltage by reducing the drive current of the switching transistor 2 to perform class A operation. In other words, the oscillation mode is changed between starting and steady state, which puts stress on the transistor 2 and generates a large amount of heat.

There is also a method in which a resistor is connected to the input part of the inverter circuit 3 and the output voltage is lowered by the voltage drop caused by the resistor.

However, it is necessary to provide a switch element with a high withstand voltage of about 200 to 400 V in parallel with the resistor, which is expensive, and also causes loss during normal operation.

Furthermore, there is also a method in which the inverter circuit 3 is configured as a single-block oscillation type, and the reset circuit is made inactive at startup to shorten the ON time of the transistor 2. but,
The output voltage also changes greatly due to fluctuations in the power supply voltage, resulting in a lack of stability.

Purpose of the Invention The present invention has been devised in view of the above points, and provides a discharge lamp lighting device that can stably lower the output voltage and perform a warm start without applying stress to the switching transistor or using a high-voltage switch element. The purpose is to obtain a one-way inverter for use.

Summary of the Invention The present invention adopts a blocking oscillation type LC series resonant circuit for its base drive, and at startup, a timer circuit reduces the capacitance for a certain period of time to shorten the ON time of the switching transistor. The lamp is configured to preheat the filament by lowering the voltage applied to the lamp to such an extent that the discharge lamp does not light up, and after a certain period of time, the capacity is increased to generate a steady lamp voltage for starting and lighting. .

Embodiment of the Invention An embodiment of the present invention will be described with reference to FIGS. 2 to 4. The symbols shown in FIG. 1 shall be used as they are. First, the output end of the full-wave rectifier circuit 10 connected to an AC power source has the primary winding N1 of the inverter transformer 4. The collector emitter of the switching transistor 2 and the diode 11 are connected. A capacitor 12 is connected in parallel to the -order winding N1, and an LC parallel resonant circuit 13 is formed by the inductance LP of the -order winding N1 and the capacitance Cp of the capacitor 12. Also, inverter transformer 4
A base winding Nu whose one end is connected to the diode 11 is provided on the primary side.

Therefore, between the base and emitter of the transistor 2 (
Here, the emitter side is the diode 11, the base □ winding N
(through the center tap of B), this transistor 2
1 for the base drive. A C series resonant circuit 14 is connected. Here, the inductance Ls of the LC series resonant circuit 14 is due to a choke coil 15, and a resistor 16 is connected in parallel to the choke coil 15.

Also, the capacitance Cs is secured by the capacitors 18 and 19 connected in parallel via the diode 17, but as will be described later, the capacitance C! A.

and the steady state capacitance CS 1 are different from each other. A thyristor 20 is connected to the capacitor 19 so as to be opposite to the diode 17, and a timer circuit 21 is connected to the gate of the thyristor 20. - This timer circuit 21 is composed of a resistor 22, a capacitor 23, a resistor 24, 25, and a diode 26, and the diode 26 is connected to the diode 11. In addition, a transistor 27 is connected to the capacitor 18.
A resistor 28 is connected in parallel through the resistors 1 to 2.
A resistor 29 is connected between the base of 7 and one end of the base winding Nu.
Diodes 30, 31 are connected.

Here, the capacitors 18 and 19 are mentioned above.

Letting each capacitance be C1e and Cts, C1B <
C1s, for example C1B: C15=1:
It is set as 10. Therefore, if we consider 18.19 capacitors with capacitance NC5K in parallel, it is a composite capacitance,
Cs = Ci & 1 + C1v, but capacitor 1
If 8 is considered alone, Cs = C1u.

In this way, a one-way blocking oscillation type inverter including the LC parallel resonant circuit 13 and the LC series resonant circuit 14 is configured.

In such a configuration, if the thyristor 20 is now
It is assumed that N. In a one-sided inverter,
The switching transistor 2 is controlled by the action of the LC parallel resonant circuit 13 and the LC series resonant circuit 14, and the base current generator II? A collector current Ic flows as shown in FIG. 3(,)(b), and a voltage V cy as shown in FIG. 3(c) is generated between the collector and emitter of the switching transistor 2 when it is turned off. In other words, upon power-on, resistance 3
When the base current In starts to flow through the transistors 2 and 2, the switching transistor 2 is turned on. As a result, the collector current 1c also flows, causing the LC parallel resonant circuit 13 to operate in oscillation.

On the other hand, the emitter current flows through the diode 11 to the LC series resonant circuit 14, and the base drive of switching 1 to transistor 2 is continued. When the pace drive by this LC series resonant circuit 14 causes the collector current Ic to flow]11, that is, the O of the switching transistor 2
This will control the N time. Here, thyristor 20
Since it is assumed that the capacitor 18.19 is ON-N, the capacitor 18.19 is charged every cycle, and the transistor 2.7
Since the resistor 28 discharges when turned ON, the capacitance JICs of the LC series resonant circuit 14 is constituted by the parallel connection of the capacitors 18 and 19, and Cs=C111+C19. Therefore, this value JICs=C1u + C
○N time T of switching transistor 2 due to ill
1 is set to produce a steady lamp voltage in the secondary winding N2.

However, since the timer circuit 21 is present when the power is turned on, the thyristor 20 is not ONL.

That is, current flows through the diode 11.26, but
This is because the charging operation of the capacitor 23 is delayed until t-1 and the gate of the thyristor 20 is not triggered. Therefore, in parallel with charging the capacitor 18, the capacitor 19 is also charged via the diode 17, but the transistor 27 is ONL, but the thyristor 20 is OFF.
NL, because I haven't.

The capacitor 19 is not discharged, but only the capacitor 18 is discharged. That is, the capacitor 19 is inactive for a certain period of time until the thyristor 20 is turned on by the timer circuit 21. As a result, for a certain period of time after the power is turned on, the capacitance Cs of the LC series resonant circuit 14 is changed to the capacitor 18.
Only FFI Cnu will be in charge of this. This is set as the starting capacitance C5O:C11l.

Here, CIll is a parallel composite capacitor 41 C1B + C1
9, the base current Iu is controlled by the LC series resonant circuit 14 as shown in FIG. 4(,), and the time during which collector current 1c flows is
It becomes shorter as shown in Ll). In other words, when transistor 2 is ON, 1111 T o becomes shorter, so
- The lamp voltage applied to the secondary winding N2 based on the secondary winding N1 is reduced to such an extent that the lamp does not bottom out. In this state, the filaments 5a and 5b are preheated by the filament windings Npt and N+.2.

When the thyristor 20 is turned on after a certain period of time determined by the timer circuit 21 has elapsed, the control as shown in FIG. 3 is performed as described above. In other words, the capacitance Jl(,s) of the LC series resonant circuit 14 is composed of the combined capacitance of the parallel capacitors 18 and 19, and this is expressed as the steady state capacitance C51=C
1&I+C19. At this time, since the ON time T1 of the transistor 2 is long, a steady lamp voltage is generated in the secondary winding Nl, and the discharge lamp 5 is lit.

Effects of the Invention Since the present invention is configured as described above, the capacity of the LC series resonant circuit for the drive is made different by 1 minute at the start and at the steady state, and this capacity is reduced when going to star 1. By simply shortening the time during which the collector current of the transistor flows, that is, the ON time of the switching transistor, the filament can be preheated while lowering the lamp applied voltage, and then the lamp can be turned on at a steady voltage, reducing stress on the switching transistor. It is possible to perform a stable warm start without applying stress to the high-voltage switch transistor, or using a high-voltage switch element.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional example, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Figs. 3 (,) to (C) are waveform diagrams during steady state, and Figs. 4 (,) to (e) is a waveform diagram at the start. 2... Switching transistor, 5... Discharge lamp,
13...LC parallel resonant circuit, 14...LC series resonant circuit, 18-19...capacitor, 21...timer circuit Applicant: Toshiba Electric Materials Corporation 3"

Claims (1)

[Claims] For lighting a blocking oscillation type discharge lamp in which an LC series resonant circuit for base drive is connected between the base and emitter of a switching transistor - In a stone-type inverter, a steady lamp voltage is applied to the secondary winding of the inverter transformer to which the discharge lamp is connected. The capacitance of the LC series resonant circuit is constituted by a parallel capacitor having a composite capacitance that controls the ON time of the switching transistor so as to generate . A stone-type inverter for lighting a discharge lamp, characterized in that it is equipped with a timer circuit that makes it possible to