CN2468259Y - Whole AC output fluorescent lamp electronic ballast - Google Patents

Abstract

The utility model discloses a whole AC output fluorescent lamp electronic ballast. A high-frequency electrical inductor L2 larger than 100m is connected in parallel to the output end of an ordinary electronic ballast that is both ends of a load lamp tube for filtering the DC part of the output voltage and realizing whole AC output; the emission of lamp filaments at both ends of the lamp tube is made to be in equilibrium. Thus, the phenomenon that one end of the lamp tube is blacked can be avoided; consequently, the service life of the lamp tube is prolonged.

Description

The full electronic ballast for fluoresent lamp that exchanges output

The utility model relates to a kind of fluorescent lamp ballast.

In order to prolong the life-span of fluorescent lamp, in electric ballast, adopt the delayed startup circuit at present mostly, incorporate thermistor in lamp tube ends.Situation for frequent switch has certain effect although it is so, but for the fluorescent lamp or the electricity-saving lamp that use continuously in public places, still there is life problems, what will solve in this case is not the problem of switch number of times, it mainly is the crest ratio of the output characteristic of improving electric ballast, especially output voltage.But we find to also have a very important problem, and the flip-flop of output voltage has been left in the basket.We often see such a case, and fluorescent tube is after use is long-time, and an end is excellent, and the other end seriously turns black, and are just bad soon.If the problem of output crest ratio should all be turned black at two ends simultaneously.We find that this is asymmetric the causing of positive-negative half-cycle of output voltage waveforms, i.e. another height of the integral area ratio of a half period directly just can measure the direct voltage of lamp tube ends with D.C. voltmeter, sometimes up to about 10V.If we are connected on the two ends of a direct current output circuit to a common fluorescent tube, even power match has only the working life about 100 hours after the startup, fluorescent tube is connecing the anodal whole blackhead of an end, and connects negative pole one end almost without any blackspot.This is because be in the ionization state all the time at the cathode material that connects on the positive terminal filament, the cathode material cation is subjected to the lasting bombardment from the electronics that connects negative pole end, same ion may be subjected to twice or above continuous bombardment and acceleration, breaks away from filament and deposits on pin.Under alternating voltage, power positive cathode constantly exchanges, even part cathode material ion breaks away from filament, major part change along with electric power polarity before arriving tube wall still can be got back on the filament under the exchange effect of electric field.So the lamp tube service life of working under alternating voltage will be grown.In order to obtain exchanging output, added capacitance at output, this does not also mean that output has been exactly full AC signal.Undoubtedly, the electric current I (t) by capacitance during continuous firing is zero to the integration of time, or in the one-period (T), the positive half period of current waveform and the integration of negative half-cycle and be zero ∫ I (t) dt=-∫ I (t+T/2) dt, and electric current does not contain flip-flop.Owing to bear the multiplication factor of two triodes of positive-negative half-cycle vibration, the parameter that matches and they (mainly contain magnetic core from the distance of thermal source, magnet ring, also to consider distance with filament for compact type energy-saving lamp) temperature that causes is inconsistent, and two filaments is inconsistent, per two points for the positive-negative half-cycle antiphase, not necessarily satisfy I (t) dt=-I (t+T/2) dt, if but load is pure resistance (linear element), ∫ U (t) dt=∫ RI (t) dt=R ∫ I (t) dt=-R ∫ I (t+T/2) dt=-∫ U (t+T/2) dt, output is not still for containing the alternating voltage of direct current signal.And fluorescent tube is a non-linear element, electric current and voltage are not necessarily proportional, so just cause the positive-negative half-cycle voltage integrating meter and be not 0, ∫ U (t) dt ≠-∫ U (t+T/2) dt, the direct voltage (just can measure with D.C. voltmeter) of several approximately volts appears in lamp tube ends.Though it is serious under DC power supply that this flip-flop of output voltage does not resemble on-line operation for the influence of lamp tube service life, but long-term accumulation also can cause fluorescent tube to engender that an end is black, thereby make fluorescent tube far not reach the desirable life-span, generally have only about 1,000 hours.So except that reducing output crest ratio, reduce or eliminate the flip-flop of output voltage, also extremely important for improving output characteristic, prolonging lamp tube service life.

The purpose of this utility model provides a kind of electronic ballast for fluorescent lamps, and it can effectively filtering flip-flop, realizes the full output that exchanges, thus the useful life of improving fluorescent tube.

For achieving the above object, solution of the present utility model is: at the output of ordinary electronic ballast, promptly incorporate a high-frequency inductor into greater than 100mH at the two ends of load fluorescent tube, the flip-flop of filtering lamp tube ends voltage, make two ends filament emission be in balance, avoid shortening lamp tube service life because of an end premature aging.

This with the beneficial effect that utility model is compared with prior art had is: owing to adopt above scheme to make the output voltage of ballast not contain flip-flop, can avoid fluorescent tube an end blackhead phenomenon to occur like this, thereby useful life of prolonging lamp tube greatly, especially low power electricity-saving lamp (5W～11W), effect is more remarkable, generally can reach the average life span more than 8000 hours.Problems such as life-span consistency that the difference of the dependence of selecting the different manufacturers fluorescent tube and filament caused with regard to the product quality that overcome electricity-saving lamp like this.

Fig. 1 is the circuit theory diagrams of the utility model electric ballast.

The circuit of electric ballast (comprises diode D and capacitor C by current rectifying and wave filtering circuit as shown in Figure 1 ₀), circuits for triggering (comprise diac DB, resistance R ₁, diode d and capacitor C _x), oscillating circuit (mainly comprises two triode T ₁And T ₂, magnet ring H, vibration main coil L ₁, capacitor C ₂), output circuit (comprises capacitor C ₁With load fluorescent tube G) form.Through diode D and capacitor C ₀Rectifying and wave-filtering obtains direct-current working volts, at triode T ₂The diode DB that is triggered triggers the back starting of oscillation.For overcome above we mention cause two asymmetric factors of half period, two triode T ₁With T ₂β value and the parameter that matches identical as far as possible, they are the position of each thermal source symmetry of should trying one's best relatively.Even but like this, the consistency of different lamp tube ends filaments is all variant, comprise the length, resistance of filament, around the ring number, be coated on the difference of what and electron work functon thereof of cathode material on the filament, all might cause the distortion of both end voltage waveform and produce dc partial voltage.We know that string is in the capacitor C of output ₁Just play a part to hand over, but it can only guarantee that output current does not contain flip-flop, can not solve output voltage problem in this respect fully every straight-through.By long-term practice, the effect that we adopt the perfectly straight flow resistance of inductance to exchange has well solved this problem, and it is just in time opposite with the effect of capacitor filtering.Shown in Fig. 1 dashed rectangle, and in the inductance L of lamp tube ends ₂For direct voltage is short circuit, if inductance value is enough big, for high-frequency ac voltage, still can regard open circuit as, the direct voltage of lamp tube ends is almost 0 like this, and very little for the alternating component influence, the output voltage that obtains does not contain flip-flop.

Inductance of so direct access almost is impossible on power-frequency voltage.Because the impedance of inductance is the product of electric voltage frequency and inductance value, exactly because the output of the high frequency of electric ballast, we could filter the flip-flop of output and make by its alternating current very little with the less high-frequency inductor of volume.This just requires the numerical value of this inductance enough big, otherwise exports by its shunting, and some electric current directly burns out it by it and heating.So its inductance value will be much larger than oscillation circuit main coil L ₁Inductance value, generally more than 20 times.We select the inductance greater than 100mH, and the high-frequency current that passes through is no more than 1mA, and heating is just very little like this, and power consumption is also very little under the situation of zero load.Certain L ₂Also be not to be the bigger the better, because inductance value is bigger, its resistance value is also big, will influence the effect of its filtering direct current, otherwise its volume will be bigger, is difficult to hold.Because main coil L ₁All less with the resistance of two filaments, so the inductance L that we added in Fig. 1 ₂Two ends can be connected on U point and vibration main coil L ₁Arbitrary end (P or Q) between, also can be connected between the in addition two ends (X and Y) of two filaments, promptly and in capacitor C ₂Two ends.

Claims (2)

1. an electric ballast is made up of rectification, triggering, vibration, output circuit, it is characterized in that: at the output of electric ballast, promptly incorporate a high-frequency inductor (L greater than 100mH at the two ends of load fluorescent tube ₂).

2. electric ballast according to claim 1 is characterized in that: the inductance (L that its output added ₂) two ends can be connected on U point and vibration main coil (L ₁) any end P or Q between, also can be connected between the in addition two ends X and Y of two filaments, promptly and at electric capacity (C ₂) two ends.

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