CN2209423Y - Electronic ballast - Google Patents

Abstract

The utility model belongs to an inversion type electronic ballast supplying current for a fluorescent lamp. An oscillation transformer in an inverter circuit of the ballast is a magnetic bias controlled oscillation transformer with an additional control winding; with a pre-heating and an abnormal circuit, the pre-heating and the abnormal protective circuit connected with the oscillation transformer make the electric voltage outputted to the strip lamp drop below the safety value with a method exerting control current to the transformer. A first winding connected in parallel with a bidirectional controlled silicon filament transformer can provide suitable preheating current for filaments, and can permit the bidirectional controlled silicon filament transforme to close after preheating is finished. The ballast has the advantages of low cost and safe reliability, and can prolong the service life of lamp tubes.

Description

Electric ballast

The utility model belongs to the inverse type electric ballast for the fluorescent lamp power supply.

The output of inverse type electric ballast will comprise a LC resonant circuit, is used for producing high pressure when opening, with lamp tube starting.But this voltage is harmful to when giving filament pre-heating, because it can make fluorescent tube produce harmful glow discharge, and promptly cold puncture and finish preheat mode in advance.Occur unusual as fluorescent tube wears out can not light the time safety of this high pressure entail dangers to ballast self at circuit for lamp equally.For this reason, a kind of electric ballast that increases the auxiliary inversion circuit was disclosed at U.S. Pat 005179326A in 1993, it is established an auxiliary inversion circuit in addition and is specifically designed to filament pre-heating, auxiliary inversion circuit working during preheating, main inverter circuit is closed, and when lighting fluorescent tube and main inverter circuit work behind the lamp tube starting, the auxiliary inversion circuit is closed, occur then closing two inverter circuits when unusual.This method has solved above-mentioned contradiction, but complex structure, the cost height.In addition, the Chinese patent CN2132381y of Granted publication in 1993 discloses the electric ballast of another structure, it adopts active device such as bidirectional triode thyristor to be directly parallel in lamp tube ends, when starting with the fluorescent tube short circuit, restriction fluorescent tube terminal voltage when having realized preheating, but it is fixed that preheat curent can not require according to fluorescent tube, this be because the decision size of current be frequency of oscillation and series inductance, lamp current was determined when frequency of oscillation and inductance value will be according to operate as normal.And do not mention abnormal protection; another Chinese patent CN2134029y adopts directly active electronic switch in parallel of lamp tube ends; short circuit fluorescent tube both end voltage when starting; but increase a controllable silicon and related circuit in addition and be responsible for abnormal protection; when unusual, force oscillator to enter into the pipeline start up by preheating state; equally, this design also exists the immutable shortcoming of preheat curent, and power consumption is also bigger during abnormal protection.

The purpose of this utility model provides a kind ofly has the perfect preheating and an electric ballast of abnormity protection function with what lower cost was realized; be that ballast can provide the electric current that can optimize when preheating, the voltage that can will output to lamp tube ends when preheating and circuit for lamp are unusual drops to below the lsafety level.Such ballast can prolonging lamp tube life-span and guarantee the safe and reliable of self.

Design philosophy of the present utility model is oscillation transformer in the inverter circuit to be increased by one control winding, with the D.C. magnetic field biasing that changes in the oscillation transformer, with the operating frequency of control inverter circuit, and controls the voltage that outputs to lamp tube ends indirectly.Fig. 1 shows a concrete scheme that realizes this design philosophy.Electric ballast is by current rectifying and wave filtering circuit 1; start triggering circuit 2; inverter circuit 3 and preheating and abnormity protection circuit 4 constitute; wherein the oscillation transformer T1 of inverter circuit 3 not only contains 2 ends that are connected on two main electronic switch MES1 and MES2 respectively and output winding T1-a and the T1-d between 3 ends; and be serially connected in beyond the T1-b and T1-c that contains as feedback excitation winding T1-b in the branch road of the elementary winding T2-a of the transformer T2 of current-limiting inductance or series connection mutually; be useful on the control winding T1-e that regulates D.C. magnetic field intensity adjusting inverter circuit operating frequency in the magnetic core thereby also contain, and make T1 become magnetic bias controllable oscillatory transformer.Contain with control winding one end of magnetic bias controllable oscillatory transformer T1 joiningly in preheating and the abnormity protection circuit 4, be used to provide magnetic bias to regulate the output JA of Control current.This is a major technique feature of the present utility model.The other end of control winding T1-e is connected on the intermediate point of T2 level of transformer.Transformer T2 four secondary winding of symmetry in twos obtains two groups of pulsating dc voltages through four diode D6, D7, D8, D9 full-wave rectification, is used for to preheating and abnormity protection circuit 4 provides power supply and as the abnormal state detection signal.Remaining the winding T1-a of magnetic bias controllable oscillatory transformer T1 and T1-b are respectively output winding and the feedback excitation windings that promotes main electronic switch MES1, same T1-d and T1-c then are respectively output winding and the feedback excitation windings that promotes main electronic switch MES2, therefore T1-a and T1-d are associated in respectively between 2 ends and 3 ends of MES1 and MES2, are connected on behind the T3-a at the beginning of the level of elementary T2-a, the capacitance C5 of T1-b and T1-c series transformer T2 and filament transformer between 1,3 ends of output MES2 of main electronic switch.The output of current rectifying and wave filtering circuit and meet energy storage capacitor C1 after be connected between 3 ends of 1 end of main electronic switch MES1 in the inverter circuit and MES2 and provide pulsating dc voltage for inverter circuit, start triggering circuit is connected on 2 ends of main electronic switch MES2 through diac TR1, be used for providing trigger current to MES2 when starting, clamp diode D5 is connected on the inversion electricity circuit output end JB and is used for closing start triggering circuit after inverter circuit work.Resistance R 6 is connected in parallel on and is used to prevent on 1 end of main electronic switch MES1 and 3 ends can not provide the essential electric current of vibration to make inverter output maintain electronegative potential and can not start owing to the voltage initial value on capacitor C 5, the C6.Parallel resonance capacitor C 4 is connected in parallel on the turn-off power loss that is used to reduce two main electronic switches between 1 end of main electronic switch MES2 and 3 ends.The elementary winding T2-a of transformer T2 plays current limliting and resonance effect, when capacitor C 6 starts fluorescent tube after preheating is finished and T2-a resonance produce higher voltage and light fluorescent tube, when the fluorescent tube operate as normal, adjust the phase place of electric current, make inverter circuit under state, move near zero voltage switch.When the ballast operate as normal, two main electronic switch alternate conduction produce the voltage that is similar to square wave at inverter circuit output JA.Increase shunt capacitance C4 in order to reduce turn-off power loss in the side circuit, also just when two switches replace, inserted one the two period of not conducting, and made the output wave mode be approximate ladder type ripple because the C4 both end voltage can not be suddenlyd change during this period of time.Still be assumed to square wave below for convenience of description, do not influence the problem that to discuss.This square-wave voltage will be through being connected on feedback excitation winding T1-b and the T1-c level transmission backward in the circuit, because coil winding-direction is selected, the electric current of these two feedback excitation windings of flowing through all is a positive feedback current concerning two main electronic switch MES1 and MES2, promptly providing the forward current of an increase to make it be tending towards full to 2 ends of switch when switch is opened closes, when turn-offing, switch provide one to reduce to make it be tending towards ending up to the Control current of reverse increase from forward to switch, because feedback voltage is taken from the series connection of same point and feedback winding, the different logical shutoff that has just determined another switch of a switch, vice versa.The end of each half period all be since the electric current that the switch of conducting provides to make that magnetic core enters saturated, make circuit from a stable state to another stable state conversion.The beginning of another half same period just simultaneously.So after the wire circle of main electronic switching circuit parameter and oscillation transformer T1 was determined, circuit work frequency was just determined by the saturation flux amount Φ m of magnetic core.Because the utility model has increased control winding T1-e, the direct current of T1-e is flow through in adjusting, regulated the magnetic bias in the magnetic core with regard to corresponding, the amplitude that alternating magnetic field can reach in the magnetic core has been dwindled in the increase of bias magnetic field, promptly dwindle magnetic field and arrived the saturated needed time, reduced each half period, improved frequency of oscillation, vice versa.When ballast starts preheating section or is in the abnormal protection state; preheating and abnormity protection circuit 4 apply the electric current of an approximate direct current for control winding T1-e by output JA; make the operating frequency of inverter circuit 3 be increased to higher value; owing to play the metering function of the T2-a of inductance effect in the circuit, the voltage that outputs to fluorescent tube dropped to below the safety value.From another angle, when fluorescent tube is in preheating or abnormality, there is not electric current in the fluorescent tube, the series resonant circuit that is used to start can produce harmful high pressure, and after the utility model improved operating frequency, circuit is the off-resonance point far away, and lamp tube ends voltage is dropped to below the safety value.

Magnetic bias controllable oscillatory transformer T1 is by two ring type magnetic cores and around thereon five winding T1-a, T1-b, T1-c, T1-d and control winding T1-e constitute, winding T1-a wherein, T1-b wears on one of them magnetic core, and T1-c, T1-d wear on another magnetic core, and control winding T1-e wears on two magnetic cores.Fig. 5 provides the structural representation of this transformer.Fig. 7 has provided the schematic diagram of the external equivalence of T1, marks simultaneously the same inscription end between each winding in the drawings and the polar relationship when connecting with external circuit.Why use two ring type magnetic cores, be in order to solve such problem, if promptly use single magnet ring, finishing inverter circuit is unchallenged to its self-oscillatory requirement, at this moment because winding T1-b, T1-c is simple series connection, so with a winding also be of equal value, but when increasing by a control winding again, because it is mutual that the lotus root of transformer is closed, alternating magnetic field can all induce alternating voltage on each winding, and the control winding is in order to reach the purpose with little Current Control, the number of turn is more again, so can on the control winding, respond to very high alternating voltage, this causes difficulty to applying the DC control electric current for the control winding, use two ring type magnetic cores with regard to good this problem that solved, since around to selection, it all is dextrad or left-hand simultaneously that commentaries on classics is executed to identical direction in the magnetic field that makes two magnet rings be produced when feedback current encourages, just equal and opposite in direction polarity is opposite when wearing around two magnetic fields that the control winding T1-e of two magnetic cores is associated in symmetry so simultaneously, with be zero, so will not respond to alternating voltage in control in the winding, and in control winding T1-e, apply direct current like this and just become and be easy to.Why Fig. 7 is externally equivalence on the principle, internal also inequivalence, be because if T1-e is divided into the independent winding of two series connection, T1 just can be divided into two independently transformers, these two independent winding are the magnetic core of each auto correlation oneself all, certainly all can induce very high alternating voltage on each independent winding, though can offset zero after these two Voltage Series that the opposite amplitude of polarity equates when symmetry, each winding itself is because high-tension existence can bring a series of problems such as interlayer puncture and electromagnetic radiation.

Magnetic bias controllable oscillatory transformer T1 can be by " day " font magnetic core and around thereon five winding T1-a, T1-b, T1-c, T1-d and control winding T1-e constitute, T1-a wherein, T1-b is on a frame, T1-c, T1-d is on another frame, control winding T1-e is on the stem stem of centre, this with the magnetic bias controllable oscillatory transformer by two ring type magnetic core coileds noted earlier principle still be the course of work all be identical, certainly, external equivalent relation shown in Figure 7 also is entirely true to this, here why listing narration respectively separately, is because " day " font magnetic core is EE, a series of magnetic cores commonly used such as EI are made the pattern of magnetic core behind the transformer.

4. preheat circuit of the present utility model also has bigger improvement, preheat circuit is by special-purpose filament preheating transformer T3, after lamp starts with the bidirectional triode thyristor TR2 of T3 primary short, and the magnetic bias that reduces the ballast output voltage when starting is regulated the control circuit formation, wherein behind the elementary T2-a of the T2 bidirectional triode thyristor TR2 in parallel, C6 is connected in parallel on lamp tube ends through the string resonant capacitance, and two secondary T2-b, the T2-c of T2 then are connected on respectively on the filament of lamp tube ends.The utmost point JC that C6 connects with filament links via T1-b, T1-c, T2-a and the series circuit of capacitance C6 composition and the output JA of inverter circuit.The control utmost point of controllable silicon TR2 is connected on output 4 ends of abnormality detection and timing control circuit TCC.When preheating, in order to prevent fluorescent tube generation glow discharge, and directly enter into the arc discharge state, require one to be that lamp tube ends voltage is lower than the voltage that produces glow discharge from preheat mode, the 2nd, have and satisfy the preheat curent that amplitude and duration require.The control winding T1-e one big electric current of T1 is given in last requirement by the magnetic bias control circuit, make inverter circuit be operated in higher frequency, thereby the lamp terminal voltage is dropped to below the safety value, and the latter then satisfies the requirement of different fluorescent tubes to optimum preheat curent by the step-down ratio that changes filament transformer.In order to reduce unnecessary power loss, the utility model has also increased the bidirectional triode thyristor TR2 that after fluorescent tube starts preheat circuit cuts out.The concrete course of work of preheat circuit is such, when power supply is added on the ballast, at first magnetic bias is regulated control circuit and is applied big electric current to control winding T1-e, the inverter circuit high-frequency work, export a low voltage to lamp, flow through the elementary electric current of filament transformer simultaneously and behind the step-down up-flow, the amplitude proper preheating current is provided for the filament of lamp tube ends by secondary winding T3-b, T3-c respectively.When preheating reaches the stipulated time, TCC reduces to be applied to the electric current of magnetic bias controllable oscillatory transformer on the one hand by the remaining circuit of magnetic bias adjusting control circuit, reduce the operating frequency of inverter circuit, thereby improve the lamp terminal voltage and light fluorescent tube, send to a trigger current on the other hand bidirectional triode thyristor TR2, make its conducting, thereby closed preheat circuit, the pipeline start up by preheating process finishes.

Described magnetic bias is regulated control circuit except that containing abnormality detection and timing control circuit TCC, also contain magnetic bias control triode Q1, high-pressure limit diode D19, D20, base resistance R5, R22, rectifier diode D6, D7, D8, D9, the secondary winding T2-b of transformer T2, T2-c, T2-d, T2-e, wherein the collector electrode JA of Q1 is the output that magnetic bias is regulated control circuit, be connected on the end of magnetic bias controllable oscillatory transformer control winding T1-e, the base stage of Q1 is connected on the output of abnormality detection and timing control circuit TCC, and one of the base resistance R5 of Q1 terminates on the other end of T1-e.

Abnormity protection circuit of the present utility model is regulated control circuit with the magnetic bias that the control winding T1-e of the shared secondary winding by Q1, R5, R22, D6, D7, D8, D9, D19, D20, T2 of preheat circuit, abnormality detection and timing control circuit TCC and T1 constitutes.It is according to the amplitude decision of the secondary pulsating direct current that obtains through D6, D9 full-wave rectification of T2 that TCC detects abnormality, when this amplitude surpasses a certain value regular hour, then think circuit abnormality, at this moment TCC just applies big electric current by magnetic bias diode Q1 to T1-e, the inverter circuit operating frequency is improved, the voltage that outputs to fluorescent tube is dropped to below the safety value, and always with this state continuance to removing power frequency supply.Instantaneous pressure when wherein the series circuit of diode D19, D20 is used to limit startup is too high, and the number of diode can be done suitable adjustment according to the first no-load voltage ratio of T2 from one to three in this series circuit.

At last, the time equalization circuit that also is parallel with R3, C3 and is unified on the control winding T1-e of T1, wherein the span of C3 is 0.1-1 μ, the span of R3 is 1-50 μ.Because there is individual difference in the saturation flux of two ring type magnetic cores of T1, this difference will cause two main electronic switch ON time not wait, thereby make output voltage waveforms asymmetric up and down.Resistance R 3, the parallel circuits of capacitor C 3 provide a low-impedance path for control winding T1-e, and the circulation that produces in this path will be offset by two magnetic core saturation fluxs and do not waited cause unbalanced, force the ON time of two electronic switches to be tending towards equal.

The utility model is owing to adopt magnetic bias controllable oscillatory transformer, contain the control winding, realized just can controlling the operating frequency of inverter circuit with less current, thereby control outputs to the voltage of lamp tube ends, control easily, with lower cost realized start preheating and when unusual to the restriction of lamp tube ends voltage.Close preheat circuit silicon controlled preheat circuit after containing special-purpose filament transformer and startup, both solved the nonadjustable problem of preheat curent in the general filament preheating circuit, can after lamp starts, preheat circuit cut out again, thus the life-span of saves energy and prolonging lamp tube.

Fig. 1 is a circuit diagram of realizing the concrete scheme of the utility model.

Fig. 2 is the embodiment of abnormality detection and timing control circuit TCC.

Fig. 3 is the embodiment of main electronic switch MES1.

Fig. 4 is the embodiment of main electronic switch MES2.

Fig. 5 is the structure chart of the magnetic bias controllable oscillatory transformer that constitutes with two ring type magnetic cores with around thereon five windings.

Fig. 6 is with " day " font magnetic core with around the structure chart of the magnetic bias controllable oscillatory transformer of thereon five windings formations.

Fig. 7 is the external equivalent electric circuit of magnetic bias controllable oscillatory transformer and polar relationship when connecting with circuit, and " * " is with inscription end mark.

Fig. 8 is when driving two fluorescent tubes, an embodiment of fluorescent tube and preheat circuit.

Fig. 3 and Fig. 4 are the embodiment of main electronic switch MES1 and MES2, wherein Q2, Q3 select BUT11 or MJE13007 or the similar triode of other parameter for use, D13, D16 quicken the diode that Q2, Q3 turn-off, the low tension switch diode of optional 1N4148, D14, D17 are the emitter series diodes, can select 1N4001 for use, and D15, D18 are clamp diode, select the high-voltage diode of similar 1N4007,1N5407 etc. for use, R20, R21 select 8.2 Ω resistance.Certain main electronic switch also can adopt based on MOS field-effect transistor etc. other from the electronic switch that turn-offs electronic switching element.

Fig. 2 has provided and has adopted based on the abnormality detection of comparator and the embodiment of timing controlled road TCC, first comparator IC1-A constitutes trigger with resistance R 11 capacitor C 9 diode D11, add sample resistance R7, R8 and just constituted abnormal detection circuit, second comparator IC1-B and R12, R13, C10 etc. finish the preheating timing function, diode D12 is used for bleeding off apace after the ballast outage electric charge on the timing capacitor C10, R15, Q3 are used to drive magnetic bias and regulate control triode Q1, also accept abnormal detection circuit C control simultaneously.The 3rd comparator IC1-C and R16, C11, R17, R18, R19 finishes lamp and starts the function that preheat circuit is turn-offed in the back, R6, D10, Q2, C7 provides working power for circuit, R6 gets 1K, R7 gets 47K, R8 gets 22K, R9, R10 all gets 2.2K, R11, R12 all gets 4.7K, and R13 gets 300K, and R14 gets 2.2K, R15 gets 4.7K, R16 gets 62K, R17, R18, R19 all gets 2.2K, C7, C8, C9, C10 all gets 4.7 μ, C11 gets 1 μ, D10 gets 13V voltage-stabiliser tube, D11, D12 all gets 1N4148, Q2, Q3 all gets 9013, IC1 gets LM339, this group parameter be one more convenient and through facts have proved feasible selection, the great majority of these parameters all allow bigger excursion and do not influence performance certainly, but that should particularly point out is R7 wherein, the ratio of R8 has determined to regard as the value of lamp tube ends voltage when unusual, capacitor C 10, resistance R 13 has determined warm-up time.

About the magnetic bias control transformer, warp is 7mm outside two ring type magnetic cores are got, the size of high 4mm, the electronic switch that provides for Fig. 2 .3 when to adopt magnetic permeability mu be 2000 manganese-zinc ferrite, design power is 40w, T1-a and T1-d are around 8 circles, and the normal working frequency that T1-b and T1-c wear ballast when 6 circles is about 38KHz, and T1-e wears around 30 circle left and right sides control circuits and gets final product operate as normal.As because the difference of the saturation magnetic field intensity of magnetic material makes operating frequency deviation occur, can increase coil turn in proportion can adjust.

About filament transformer, when the common single tube of design power 40w, built in 180V, when adopting 20 * 20 * 5 EI type M2000 magnetic core, T3-a is around 280 circles in startup control for lamp tube ends voltage, and around 70 circles, preheat curent is about 0.75A respectively for T3-b, T3-c.Change the primary and secondary no-load voltage ratio, can adjust preheat curent.

For driving two-tube circuit, only need in preheating transformer T3, increase a winding T3-d in the preheat circuit, and the no-load voltage ratio of corresponding adjustment transformer is just passable, Fig. 8 has provided the circuit diagram of tube circuit when driving two fluorescent tubes.

Claims (7)

1. one kind by current rectifying and wave filtering circuit 1; start triggering circuit 2; inverter circuit 3; the electronic ballast for fluoresent lamp that preheating and abnormity protection circuit 4 constitute; the oscillation transformer T1 that it is characterized in that described inverter circuit not only contains and is connected on 2 of two main electronic switch MES1 and MES2 respectively; output winding T1-a between 3 ends; T1-b; and be serially connected in beyond the T1-b and T1-c that contains as feedback excitation winding T1-b in the branch road of the elementary winding T2-a of the transformer T2 of current-limiting inductance or series connection mutually; be useful on the control winding T1-e that regulates D.C. magnetic field intensity adjusting inverter circuit operating frequency in the magnetic core thereby also contain; and make T1 become magnetic bias controllable oscillatory transformer, contain with the control winding of magnetic bias controllable oscillatory transformer joining in preheating and the abnormity protection circuit 4; be used to provide magnetic bias to regulate the output JA of Control current.

2. electric ballast according to claim 1, it is characterized in that described magnetic bias controllable oscillatory transformer T1 is made of with five winding T1-a, T1-b, T1-c, T1-d and T1-e wearing around thereon two ring type magnetic cores, wherein T1-a, T1-b wear on a magnetic core, T1-c, T1-d wear on another magnetic core, and control winding T1-e wears on two magnetic cores.

3. electric ballast according to claim 1, it is characterized in that described magnetic bias controllable oscillatory transformer T1 constitutes by " day " font magnetic core with around thereon five winding T1-a, T1-b, T1-c, T1-d and T1-e, wherein T1-a, T1-b are on a frame of magnetic core, T1-c, T1-d are on another frame, and control winding T1-e is on the stem stem of centre.

4. electric ballast according to claim 1, it is characterized in that described preheat circuit is by being with special-purpose filament preheating transformer T3, after lamp starts with the bidirectional triode thyristor TR2 of the primary short of T3, and the magnetic bias that reduces the ballast output voltage when starting is regulated the control circuit formation, wherein the elementary T2-a of T2 bidirectional triode thyristor TR2 in parallel is after 6 parallel connections of series resonance capacitor C, two secondary T2-b at lamp tube ends T2, T2-c then is connected on respectively on the filament of lamp tube ends, and the series circuit of capacitance C5 and the primary winding T2-a that plays the inductance effect is through the excitation winding T1-b of magnetic bias controllable oscillatory transformer, the output of T1-c and main switch circuit connects.The control utmost point of controllable silicon TR2 is connected on output 4 ends of abnormality detection and timing control circuit TCC.

5. according to claim 1,4 described electric ballasts, it is characterized in that described magnetic bias adjusting control circuit is by abnormality detection and timing control circuit TCC, magnetic bias control triode Q1, base resistance R5, R22, diode D6, D7, D8, D9, the secondary winding T2-b of transformer T2, T2-c, T2-d, T2-e and magnetic bias controllable oscillatory transformer control winding T1-e constitute, wherein the collector electrode of Q1 is connected on the end of T1-e, the base stage of Q1 is connected on output 2 ends of abnormality detection and timing control circuit TCC, and one of the base resistance R5 of Q1 is connected on the other end of T1-e.

6. electric ballast according to claim 1; it is characterized in that the shared secondary winding by Q1, R5, R22, D6, D7, D8, D9, D19, D20, T2 of described abnormity protection circuit and preheat circuit, the magnetic bias that abnormality detection and timing control circuit TCC and T1-e constitute is regulated control circuit.

7. electric ballast according to claim 1, it is characterized in that also being parallel with the time equalization circuit that is in parallel and forms by R3, C3 on the control winding T1-e of described magnetic bias control oscillation transformer T1, wherein the span of C3 is 0.1-1 μ, the span 1-50 μ of R3.

Images