CN1180290A - Preheat starting circuit for electronic ballast of fluorescent lamp - Google Patents

Abstract

The present invention relates to an electric circuit for electronic ballast with high-frequency output. Its ouput circuit adopts a secondary winding for preheating filament, and is connected with a coupling capacitor, and is equipped with a delayed-trigger circuit, so that it can ensure such working mode of firstly preheating and then switching into conduction so as to solves the difficult problem of that matching electronic ballast with general preheating lamp tube and obtain the effect of delaying blackening speed of lamp tube and prolonging its service life. In addition to reducing working current, it retains the features of high-frequency starting, high-frequency working, no stroboflash, no noise, no electromagnetic interference and low starting voltage, and its power factor is above 0.97.

Description

The preheat starting circuit that is used for electronic ballast for fluoresent lamp

The present invention relates to the circuit arrangement of discharge lamp igniting or control.

The present a kind of electric ballast operating circuit that uses; adopt the filtering of AC power elder generation, protection, back rectification; filtering again; be high-frequency ac through the inversion of semibridge system vibration translation circuit then; be defeated by fluorescent tube with output transformer; transient starting work; though sort circuit utilizes high-frequency work; exempt to use starter, noise is little, and electromagnetic interference is little; can accomplish not have the effect of stroboscopic; but the fluorescent tube melanism is still relatively more serious, and particularly it can't be used for common some fluorescent tubes by ballast, filament, the work of starter series circuit, otherwise its melanism is with even more serious.

The object of the present invention is to provide a kind of new preheat starting circuit, it can effectively lower the melanism speed of fluorescent tube two ends, prolongs the life-span of fluorescent tube, solves the supporting and application with common fluorescent tube.

The present invention is on the basis of existing electric ballast operating circuit, change the circuit of its output,, be preheating to certain hour for its filament provides energy earlier with the output transformer of ballast, add operating voltage to lamp tube ends again after the time-delay, make its conducting rapidly and work.Filament is identical with the common lamp works condition of use at present through preheating, can be adaptive, and under high-frequency work voltage easier conducting lamp works, thereby can reduce operating current, reduce rush of current, the filament vaporization is slowed down, reach the purpose of prolonging lamp tube service life.

The preheat starting circuit that is used for electronic ballast for fluoresent lamp of the present invention, its the elementary winding L 1 of an output transformer T1, input higher-order of oscillation electric current, secondary winding L2, L3, L4, be access to wiring pile crown A behind the one end serial connection current limiting capacitance C1 of L2 winding, its centre cap wiring pile crown B, be used to produce filament pre-heating voltage, the other end and centre cap output are used to produce lamp works voltage, the electrode 2 of this termination bidirectional triode thyristor VS, its electrode 1 meet current limiting capacitance C2, C3 and connect with wiring pile crown D; One termination wiring pile crown C of L4 winding, a termination current limiting capacitance C3 receives wiring pile crown D again, and being picked out to an other end filament by C, D provides pre-thermal voltage; L3 provides the delay trigger circuit operating voltage, is connected into series loop with rectifier diode VD1 and capacitor C 5; Constitute delay trigger circuit by RC charging circuit, field effect transistor VT1, bidirectional triode thyristor VS, its divider resistance R2, R3 are in parallel with capacitor C 5, charging capacitor C4 is in parallel with divider resistance R3, and cross-over connection is between the grid and source electrode of field effect transistor VT1, the control utmost point of the drain electrode of field effect transistor and two-way silicon VS joins, in bidirectional triode thyristor VS electrode 1 and L3 series loop, also be connected to resistance R 1 between the interface of C5, VD1 and constitute active channel, wiring pile crown A, B; C, D be external tube filament respectively.

This circuit adopts high-frequency output transformer, uses high-frequency current work, and the preheating speed is adjustable, can make filament reach preheat temperature on demand.Use the electric ballast of sort circuit, can match with common fluorescent tube.After fluorescent lamp was opened, operating frequency reduces but still about 25 kilo hertzs, the lamp works electric current is 190mA/36W, and is obviously lower than the situation of the common lamp works electric current 320mA/30W tubule (starting current 530mA/215V, power loss≤8) of present use.Because operating current reduces, rush of current alleviates, and entry condition is improved, and the filament durability improves, and will obviously be prolonged in the life-span of external fluorescent tube.

Be described further below in conjunction with specific embodiment and accompanying drawing thereof.

Fig. 1 is the circuit diagram of correlation technique.

Fig. 2 is a circuit diagram of the present invention.

Fig. 3 is to use the circuit diagram of the electric ballast of circuit of the present invention.

As shown in Figure 1, this circuit is the output circuit that once adopted the commercially available prod, because it belongs to the type of transient starting work, can not match with common fluorescent tube, otherwise startup work under the impact of high-frequency current can be quickened the damage of filament on the contrary.The elementary winding L 1 input high-frequency current of output transformer T, secondary winding L2, L3 are used to connect filament, produce high pressure and directly power to the both sides filament.Capacitor C plays coupling and metering function, has the compensation effect that reduces power consumption concurrently.This is a requisite circuit in the electric ballast way circuit.

Circuit of the present invention shown in Figure 2 has changed the basic structure of Fig. 1 circuit.Except that the input circuit of output transformer T1 was identical, the secondary winding of output was as constituting filament pre-heating loop and output services circuit, and capacitor C 1, C3 play metering function and have the function that lowers the filament wattage loss concurrently and raise the efficiency effect.Main winding L2 output services electric current wherein, but must connect the filament that capacitor C 2 is access to lamp tube ends then by the delay trigger circuit control of delay process by bidirectional triode thyristor.A, B, C, D are a set of connections pile crown of external filament, and the output of this circuit can connect 1-6 set of connections pile crown, connects in an identical manner.Delay trigger circuit provides direct-current working volts by L3 and VD1, and the electrode 1 that R1 constitutes path and triode ac switch VS joins, and C5 provides operating voltage, and R2, R3 are that divider resistance and C4 constitute charging circuit, realize time-delay.Field effect transistor VT1 is used to amplify the triggering work of triggering signal control VS.L2, VS, C2, C3, fluorescent tube, the major loop of formation bidirectional triode thyristor work.The source electrode of VT1, the electrode 1 of R3, R2, R1, VS, the control utmost point (also claiming trigger electrode, gate pole) is formed control loop.

Its course of work is summarized as follows: output transformer is behind the input high-frequency current, and its output at first is passed to preheat curent the wiring pile crown, and external tube filament is carried out preheating.The alternating current of L3 winding charges to C4 by R2, R3 dividing potential drop through the VD1 rectification and delays time simultaneously, makes field effect transistor VT1 conducting after C4 voltage raises, and the output triggering signal makes bidirectional triode thyristor VS conducting thereupon, lamp works.

Fig. 3 has provided a circuit of electronic ballast embodiment who utilizes circuit of the present invention.Isolating output transformer T1 output connects four set of connections pile crowns and connects four tubes.Its left side is the input power circuit, and wherein V1 is the overvoltage protection piezo-resistance, L, and C1, C2 form anti-tampering input filter circuit, and VD1-VD4 constitutes bridge rectifier, and C3 is an electrolytic capacitor filter.The right is depicted as the semibridge system switch transformed circuit, and the dc inversion after the rectification is become higher-order of oscillation electric current.Wherein switch triode VT2, the work of VT3 alternate conduction is set up vibration by L7, L8 input positive feedback signal, and the elementary winding L 1 on the output transformer T1 is made oscillator coil and constituted high frequency oscillation circuit.Mainly as dividing potential drop, VD6, VD7 are protecting diode for C3, C4, and VD9, VD10 are the negative peak protecting diode, and C13 forms alternating current path, R4, R5 current limliting usefulness, and R6 setovers, R7, C12, ST forms circuits for triggering.The pre-thermal output winding of output transformer is identical with the circuit of delay trigger circuit and above-mentioned Fig. 2.This circuit of general technology index of electric ballast all can meet or exceed, power factor is higher than 0.97, and total harmonic component is lower than 20%, and crest factor is lower than 1.5, compare with traditional Inductive ballast and can economize on electricity 40%, operating voltage is lower than at 25% o'clock and still can normally starts.This circuit can with common fluorescent tube adapted.

Claims (1)

1, a kind of preheat starting circuit that is used for electronic ballast for fluoresent lamp, comprise output transformer T1 and output circuit thereof, it is characterized in that a said output transformer T1, its elementary winding L 1 input higher-order of oscillation electric current, secondary winding is L2, L3, L4, be access to wiring pile crown A behind the one end serial connection current limiting capacitance C1 of L2 coil, its centre cap wiring pile crown B, be used to produce the pre-thermal voltage of filament, the other end and centre cap output are used to produce lamp works voltage, the electrode 2 of this termination bidirectional triode thyristor VS, its electrode 1 meets current limiting capacitance C2, C3 also connects with wiring line pile crown D; One termination wiring pile crown C of L4 winding, a termination current limiting capacitance C3 receives wiring pile crown D again, and being picked out to fluorescent tube other end filament by C, D provides pre-thermal voltage; L3 provides the delay trigger circuit operating voltage, is connected into series loop with rectifier diode VD1 and capacitor C 5; By the RC charging circuit, field effect transistor VT1, bidirectional triode thyristor VS constitutes delay trigger circuit, its divider resistance R2, R3 are in parallel with capacitor C 5, charging capacitor C4 is in parallel with divider resistance R3, and cross-over connection is between the grid and source electrode of field effect transistor VT1, the control utmost point of the drain electrode of field effect transistor and bidirectional triode thyristor VS joins, connecting of C5, VD1 is connected to resistance R 1 and constitutes active channel between the mid point in the electrode 1 of bidirectional triode thyristor VS and L3 series loop, wiring pile crown A, B, C, D be external tube filament respectively.

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