JPH02207490A - Electronic lighting device for fluorescent lamp - Google Patents

Abstract

PURPOSE:To enhance the degree of allowance for the withstand voltage of a thyrister in use in the normal direction by disposing a series resistor for a Zener diode and a Zener diode in parallel in a circuit wherein a resistor for controlling gate load current and a negative direction diode are connected in series, and thereby providing the current control resistor furthermore with a negative characteristic temperature sensing element in parallel. CONSTITUTION:A current lighting device is additionally provided with a resistor 5, a Zener diode ZD1 and a thermister Th. When a device is formed in this way, increasing voltage is controlled to be definite one VZD1 by means of the resistor 5 and the diode ZD1 even if AC power voltage VE is increased, negative current flowing in a gate therefore acts as a resistor R4 so as to be remained roughly constant. In addition, high voltage pulses Vpp which are resultantly generated are maintained constant, at least, the cause which breaks down a SCR acting as a single direction thyrister with gate Thy is thereby dissolved.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a lighting device for a discharge lamp.
The present invention relates to a lighting starting device using a semiconductor element for a fluorescent discharge lamp having a preheating electrode, and particularly to an electronic lighting device whose purpose is to stabilize the generation of a starting pulse.

Conventionally, glow starters have been mainly used as starting devices for preheating fluorescent lamps, but they have drawbacks such as long starting times and short lifespans.

In recent years, so-called electronic lighting devices using semiconductor switches have been developed to eliminate the above drawbacks. However, this type of device has a complicated circuit configuration, high manufacturing costs, and limited demand.

Based on the above request, there is a circuit shown in Figure 1 as a known example. In the figure, E is a commercial AC power supply, FL is a fluorescent lamp, Thy is a gated unidirectional thyristor (hereinafter referred to as SCR for explanation), and ZD is a Zener. Diode, DI.

D2 is a rectifier diode, C1 is a capacitor, CH is a choke transformer, and R1-R3 are resistors.

Next, the circuit operation will be explained according to the waveform diagram of each part shown in FIG. In the figure, VE is the power supply voltage waveform, lh is the preheating current waveform, and V
p is the tube voltage of the fluorescent lamp, ie, the voltage waveform between 5CRThy(r)A-. Now, when the power supply voltage VE increases in the forward blocking state of SCH (point a), the tube voltage of the fluorescent lamp FL, that is, the voltage Vp at A- of the SCR also increases, and the divided voltage of resistors R1 and R2 changes the operation of the Zener ZD. When the voltage is reached, the waveform V
The SCR turns on at point B, and the preheating current Ih is connected to the power supply E.
More choke transformer CH-fluorescent lamp Hilament HL-3
CRA ~ 1 diode D2 - Hirament h2 - Power supply E
, and each filament is preheated. Also, in the reverse cycle of power supply E, power supply E - diode D1 - 3CR gate - 3CR cut, - do diode D2 - filament h2
A reverse bias voltage is applied to the -power supply and SCRG-. In such a state, the preheating current Ih decreases and S
The anode tl of CR is turned off at point C when it becomes below the holding current, and combined with the reverse bias voltage effect, a reaction voltage VPP of the choke transformer is generated, and this voltage is applied between both electrodes of the fluorescent lamp FL. Accordingly, the waveform vb in FIG. 0, which reaches lighting after several cycles, indicates the tube voltage peak value waveform after lighting, and after lighting is set between Vm, the maximum value of E. The capacitor c1 has a tube voltage peak value vb that becomes high especially at low temperatures, so the SCR
This is a filter capacitor to prevent re-ignition.

Therefore, in response to the voltage fluctuation, the generated pulse also fluctuates, and in particular, the forward breakdown voltage of the thyristor may be exceeded, leading to destruction of the thyristor.

2) The pulse generation voltage tends to increase due to the improvement of the breakdown characteristics of the thyristor and the increase in the holding current, especially at low operating temperatures, and may eventually exceed the forward breakdown voltage of the thyristor, causing destruction of the thyristor. It may lead to.

There was a practical restriction because it could lead to a breakdown in the evening.

[Objective of the invention 1 In the present invention, by solving the problems,
The purpose is to provide a practical starting device.

[Disclosure of the Invention] FIG. 3 shows an example of a circuit according to the present invention. In the figure, the same reference numerals refer to those in FIG. (hereinafter referred to as a thermistor).

FIG. 4 shows an example of a waveform for explanation.The operating principle related to lighting is as already explained in FIGS. 1 and 2, and will be omitted hereafter.
The negative gate bias circuit of the thyristor will be explained with reference to FIG. 4. The present invention is characterized by the addition of a resistor R5, a Zener diode ZDI, and a thermistor Th in the figure, whereas the conventional circuit is , 11IrL is applied to AC power supply E by a series circuit of diode D1, resistor R4, and diode D2, so it has dependence on voltage fluctuation of AC power supply E, and the gate bias current is also proportional to that voltage fluctuation. Changes to As a result, the generated high voltage pulse VPP naturally changes as shown by the solid line for the fifth factor. Due to variations in the thyristor gate characteristics, this generated voltage may break down when the AC power source rises, and as a result, the thyristor may sometimes be destroyed.

The present invention has been made to solve this problem, and when the AC power supply voltage VE increases, the resistor R5
The rising voltage is limited to a constant level by the Zener diode ZDl (VZD 1 ) in FIG. 4. Therefore, the negative gate current flowing into the gate is kept substantially constant by the resistor R4. The resulting high voltage pulse VpP is the fifth
As shown by the dotted line in the figure, the voltage is kept approximately constant, and the generated voltage depends on the characteristics of the Zener diode.

As a result, under the constant set to the rated state, even if the power supply voltage increases, the generated voltage remains approximately constant.
At least the factor that caused the thyristor to break down has been eliminated.

In the above explanation, it was due to fluctuations in the power supply voltage (VE), but next, when the operating temperature (T a ) changes, the breakdown characteristics of the thyristor are affected by temperature dependence, especially under low temperature conditions. Coupled with the improvement in performance and the increase in holding current, the number of generated pulses increases (dotted chain line in FIG. 5), sometimes leading to breakdown. In the present invention, the thermistor Th is inserted in parallel with the resistor R4, and if the operating temperature decreases, the dynamic resistance of the thermistor Th has a characteristic that increases.As a result, the resistance R4
As a result, the gate negative bias current acts to decrease, and therefore the generated pulse voltage VPP is limited and reduced. Conversely, when the temperature rises, the combined resistance with resistor R4 decreases,
As a result, the gate negative current rises, and the generated pulse acts in the rising direction and is corrected to be substantially constant.

[Brief explanation of the drawing]

FIG. 1 is a circuit example for explaining the operation of a conventional lighting device. FIG. 2 is a waveform diagram for explaining conventional operation. FIG. 3 shows an example of a circuit according to the present invention. FIG. 4 is a waveform diagram of the present invention. FIG. 5 shows characteristic diagrams of the present invention. [Effects of the Invention] As explained above, conventionally, due to fluctuations in power supply voltage and changes in operating temperature, the generated pulse voltage fluctuates and sometimes exceeds the forward withstand voltage of the thyristor, leading to breakdown, resulting in damage to the thyristor. The case that leads to destruction is the cause of death.

Claims (1)

[Claims] A unidirectional thyristor with a gate is connected tangentially between the series circuit of the AC power supply, the choke transformer, and the discharge lamp with a preheating electrode, and the non-power supply side preheating electrode of the discharge lamp, and the thyristor is rotated by the detected voltage on the non-power supply side. In addition, in a circuit in which a gate negative current limiting resistor and a negative diode are connected in series to supply a negative gate bias voltage for generating high voltage pulses to the gate of the thyristor from an AC power supply, An electronic lighting device for a fluorescent lamp, characterized in that a resistor and a Zener diode are interposed in parallel, and a negative temperature sensing element is connected in parallel to the current limiting resistor.