KR19980065080U - Electronic Fluorescent Ballast with Preheating Light Circuit - Google Patents

Abstract

An electronic fluorescent ballast employing a preheating lighting circuit is designed to extend the life of the fluorescent lamp by lighting it while soft starting the filament of the fluorescent lamp. The present invention rectifies and smoothes the input power when the fluorescent lamp is turned on to obtain a DC voltage, a resonant capacitor connected in parallel to both ends of the filament electrode of the fluorescent lamp, and an output end of the transformer which turns on the fluorescent lamp according to the induced voltage, and a smoothed An electronic fluorescent ballast composed of a half-bridge circuit for inducing a DC voltage to a transformer includes a preheating circuit for preheating by controlling a transient current upon initial lighting. The preheating circuit includes an electrolytic capacitor that charges and discharges a voltage induced in a transformer, a transistor that is turned on / off according to charging and discharging of an electrolytic capacitor, and operates for a time when the electrolytic capacitor is fully charged, and an emitter of the transistor. The gate is connected to the transistor and is turned on / off in conjunction with the transistor to form a field effect transistor (FET) that saturates the signal transformer connected to both the drain and the source. Therefore, the present invention reduces the initial resonant current of the resonant capacitor by saturating the signal transformer, so that only the preheating current flows through the filament of the fluorescent lamp, thereby providing an effect of reducing unnecessary power consumption and extending the lifetime of the fluorescent lamp.

Description

Electronic Fluorescent Ballast with Preheating Light Circuit

The present invention relates to an electronic fluorescent ballast, and more particularly, to an electronic fluorescent ballast employing a pre-heating circuit for controlling the transient current during the initial lighting of the fluorescent lamp and preheating the lamp to extend the life of the fluorescent lamp.

Fluorescent lamps are used in most homes and offices because they are more efficient and have a longer lifespan than incandescent bulbs, and are less dazzling and do not have a noticeable shade. In addition, the fluorescent ballast for the stable operation of the fluorescent lamp has a magnetic and electronic, and in terms of power consumption, most of the electronic is used.

However, when a conventional electronic ballast adopts a switching method to light a fluorescent lamp, a high voltage of about 1000 V is generated at both ends of the fluorescent lamp, thereby generating black black bands at both ends of the fluorescent lamp. As a result, the filament of the fluorescent lamp was quickly corroded, causing a short life of the fluorescent lamp.

Accordingly, an object of the present invention is to provide an electronic fluorescent lamp ballast employing a preheating lighting circuit that can extend the life of the fluorescent lamp by stabilizing the transient current flowing into the fluorescent lamp during initial lighting in order to light up gradually. In providing.

1 is a circuit diagram showing an electronic fluorescent ballast employing a preheating lighting circuit according to the present invention,

2 is a diagram illustrating a signal transformer of the half bridge circuit of FIG. 1;

3 is a waveform diagram illustrating the operation of the FIG. 1 preheating circuit;

Explanation of symbols for main parts of the drawings

11: rectifier 12: smoothing circuit

13: half bridge circuit 14: preheating lighting circuit

15: Output stage OSC1 to OSC4: Signal trans

T1: Trans FET: Field Effect Transistor

Q1 to Q3: transistor C12: electrolytic capacitor

The electronic fluorescent ballast employing the preheating lighting circuit of the present invention for achieving the above object is an input terminal for rectifying and smoothing the input power to obtain a DC voltage, and a resonance capacitor connected in parallel to both ends of the filament electrode of the fluorescent lamp, The output stage of the transformer which turns on the fluorescent lamp according to the induced voltage and the smoothed DC voltage obtained from the input terminal are induced in the transformer, and the amount of current switched under the control of the preheating lighting circuit is changed so that only the preheating current is applied to the filament at initial lighting. A flowing half bridge circuit and a preheating lighting circuit for charging and discharging the voltage induced in the transformer and controlling the amount of current switched in the half bridge circuit in order to gradually normalize the illumination without flickering the fluorescent lamp during initial lighting. do.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram of an electronic fluorescent ballast employing a preheating lighting circuit according to an embodiment of the present invention. The ballast shown in FIG. 1 is composed of a rectifier 11 and a smoothing circuit 12, a half bridge circuit 13, and an output stage 15 which largely rectify and smooth the input power, and preheat the present invention. The lighting circuit 14 is further included. The rectifier 11 is a single-phase electric wave bridge using four diodes D1 to D4, and the smoothing circuit 12 smoothes the rectified power source using two diodes D5 and D6 and electrolytic capacitors C4 and C5. Obtain DC voltage by The half-bridge circuit 13 includes the signal transformers OSC1 to OSC4 as shown in FIG. 2 and a plurality of transistors Q1 and Q2 which switch alternately with each other by the signal transformers OSC2 and OSC3. The output terminal 15 includes a transformer T1 for igniting a fluorescent lamp with a voltage induced by switching the transistors Q1 and Q2 of the half-bridge circuit 13 and a resonant capacitor C9 connected in parallel to both ends of the filament electrode. ). On the other hand, the preheating lighting circuit 14 is a diode (D10) for rectifying the voltage induced in the transformer (T1), the electrolytic capacitor (C12) to receive and discharge the induced voltage through the diode (D10), the diode to the collector The resistor R10 is connected to the signal transformer OSC1 through D13 and is turned on / off according to the charge / discharge of the electrolytic capacitor C12 and the emitter of the transistor Q3. A gate is connected to each other, and is formed of a field effect transistor (FET) that is turned on / off in conjunction with the transistor Q3. An operation of the electronic fluorescent ballast of FIG. 1 having such a configuration will be described in detail with reference to FIGS. 2 and 3.

In FIG. 1, when a fluorescent light switch (not shown) is operated by a user, power is input to the rectifier 11 via FUSE in response. The rectifier 11 is a single-phase full-wave bridge using four diodes D1 to D4. The rectifier 11 rectifies the input power and outputs the rectified circuit 12 to the smoothing circuit 12. The smoothing circuit 12 smoothes the rectified power using diodes D5 and D6 and electrolytic capacitors C4 and C5 to obtain a smoothed DC voltage. The smoothed DC voltage is induced in the transformer T1 of the output terminal 15 via the resistor R1 of the half-bridge circuit 13 and the diode D14, and is also applied to the collector of the first transistor Q1. The first transistor Q1 and the second transistor Q2 having the collector connected to the emitter of the transistor Q1 are switched by the signal transistors OSC2 and OSC3 so as to cross each other and the voltage is applied to the transformer T1. Induced, the fluorescent lamp is turned on. At this time, a high voltage of about 1000 V is induced across the fluorescent lamp by the resonance current of the ballast. Thus, when the initial input voltage is applied, the voltage induced in the transformer T1 is charged to the electrolytic capacitor C12 via the diode D10 and the resistor R7 of the preheating lighting circuit 14. The field effect transistor FET is continuously operated by turning on the third transistor Q3 for a time when the voltage induced in the transformer T1 is fully charged of the electrolytic capacitor C12. The operation of the field effect transistor FET saturates the entire signal transformer OSC1 to OSC4 as shown in FIG. 2 connected to both the drain and the source of the field effect transistor FET, resulting in a decrease in inductance. Accordingly, the transistors Q1 and Q2 have a small current drawn in each base to switch only a small amount of current, thereby reducing the initial resonant current. As the resonance current of the resonant capacitor C9 connected to both ends of the filament electrode of the fluorescent lamp decreases rapidly, the lighting is interrupted. Be sure to At this time, the preheat voltage applied to the fluorescent lamp becomes like the front end of the waveform shown in FIG. 3B. 3A and 3B, the preheating step is maintained for about 1 second immediately after the switch-on, and the charging of the electrolytic capacitor C12 is completed, so that the field effect transistor FET is connected to the third transistor Q3. It is turned off. As the field effect transistor FET is turned off, the signal transformers OSC1 to OSC4 as shown in FIG. 2 connected to both the drain and the source thereof operate in a normal state. At this time, the transistors Q1 and Q2 having a base connected to the signal transformers OSC2 and OSC4 initiate switching of the normal current through the resistors R2 and R4 so that a lighting current having a desired rating such as the rear end of the waveform shown in FIG. It keeps steadily lighting state while shedding. At this time, the preheat voltage applied to the fluorescent lamp is the same as the rear end of the waveform shown in FIG. 3B. Here, conventional lighting currents and voltage waveforms without a preheating step are shown in FIGS. 3C and 3D to help the present invention. Referring to the waveforms of FIGS. 3C and 3D, a short inrush current occurs within approximately 0.09 seconds immediately after the switch-on, and then turns on.

As described above, the electronic fluorescent ballast employing the preheating lighting circuit of the present invention reduces the initial resonant current of the resonant capacitor connected to both ends of the filament electrode of the fluorescent lamp during initial lighting, so that only the preheating current flows and gradually changes to normal illumination without flicker. By doing so, it has the effect of reducing unnecessary power consumption and extending the life of the fluorescent lamp.

Claims (4)

In electronic fluorescent ballasts, An input stage for rectifying and smoothing the input power to obtain a DC voltage; An output terminal comprising a resonant capacitor connected in parallel to both ends of the filament electrodes of the fluorescent lamp, and a transformer for lighting the fluorescent lamp according to the induced voltage; A half-bridge circuit which induces the smoothed DC voltage obtained from the input terminal to the transformer and flows only a preheating current to the filament at initial lighting due to a change in the amount of current switched under control of a preheating lighting circuit; And An electronic fluorescent ballast comprising a preheating and lighting circuit for charging and discharging the voltage induced in the transformer and controlling the amount of current switched in the half-bridge circuit according to the normal lighting without flicker of the fluorescent lamp during initial lighting. The method of claim 1, wherein the preheating lighting circuit An electrolytic capacitor for charging and discharging the voltage induced in the transformer; A transistor configured to be in an on / off state according to charging and discharging of the electrolytic capacitor; A field effect transistor having a gate connected to an emitter of the transistor, the field effect transistor being turned on / off in association with the transistor; And An electronic fluorescent ballast connected to both the drain and the source of the field effect transistor and controlling a switching current amount of the half bridge circuit according to an on / off state of the field effect transistor. . The method of claim 2, wherein the electrolytic capacitor charges a voltage induced in the transformer at the initial lighting, The transistor is turned on during the charging time of the electrolytic capacitor, and turned off when charging is completed. The field effect transistor is in an ON / OFF state in conjunction with the transistor, while saturating the signal transformer while in the ON state to drop inductance, and while in the OFF state, the signal transformer. Electronic fluorescent ballast characterized in that to operate in a normal state. The method of claim 3, wherein the half-bridge circuit When the inductance of the signal transformer falls, only a small amount of current is switched to reduce the resonance current of the resonance capacitor so that only preheating current flows. And the rated current flows by switching an appropriate amount of current when the signal transformer is in a normal operating state.