A kind of electronic ballast for fluoresent lamp with frequency converting and preheating functions
Technical field
The utility model relates to a kind of ballast, especially a kind of electronic ballast for fluoresent lamp with frequency converting and preheating functions.
Background technology
Some widely popular filament preheating circuits mainly contain following three kinds of modes at present:
The filament preheating circuit that the first adopts the PTC thermistor to form, to be the PTC thermistor will not bear very high voltage in a period of time before the starter at lamp to the shortcoming that sort circuit exists, work many times in this state in long-time, the PTC thermistor lost efficacy easily.In addition, this preheat circuit still has extra heater current to flow through the PTC thermistor after starting, it can produce extra power consumption on filament and PTC thermistor, unnecessary power consumption can make temperature rise, and has reduced the reliability of whole lamp, and has reduced the light efficiency of whole lamp.
It two is to adopt the PTC thermistor to connect with diac, the shortcoming of sort circuit is need be according to the wattage of lamp, the length and the light tube electric voltage of fluorescent tube, the puncture voltage of choose reasonable diac, the general high triggering of puncture voltage, its price is more expensive, and its puncture voltage is relevant with ambient temperature, also can change with variation of temperature.
It three is to adopt general frequency modulation pipeline start up by preheating, the work of lamp by preheating, trigger starter, light three phases and carry out successively, and the operating frequency complementation in each stage is identical, this kind circuit shortcoming is the process that warm-up phase has a frequency to descend, longer to normally lighting time ratio, can't reach stable rapidly, also just can't guarantee the fluorescent light flux stability.
The utility model content
The purpose of this utility model is to provide a kind of electronic ballast for fluoresent lamp with frequency converting and preheating functions that descends and reach stable rapidly, can guarantee the fluorescent light flux stability rapidly in the warm-up phase frequency.
For achieving the above object; the utility model has adopted following technical scheme: a kind of electronic ballast for fluoresent lamp with frequency converting and preheating functions; comprise Switching Power Supply; Switching Power Supply is given control circuit and lamp tube power supply respectively; microprocessor, frequency converting and preheating circuit link to each other with control circuit respectively; control circuit links to each other with fluorescent tube by the half-bridge power control circuit, also comprises protective circuit, and fluorescent tube links to each other with microprocessor by protective circuit.
As shown from the above technical solution, frequency converting and preheating circuit in the utility model adopts frequency converting and preheating to start equally, operating frequency is higher during beginning, reach 60KHZ, frequency of oscillation descends rapidly afterwards, and is stable when reaching 30KHZ, guaranteed the fluorescent light flux stability, prolong the life-span of fluorescent lamp, increased the switch number of times of fluorescent tube.In addition, the Switching Power Supply supply power mode is adopted in load, has guaranteed the stability of control circuit, has guaranteed the stable of fluorescent lamp operation state simultaneously, and luminous flux has advantages of higher stability simultaneously.
Description of drawings
Fig. 1 is a circuit block diagram of the present utility model;
Circuit block diagram when Fig. 2 is the utility model application;
Fig. 3,4,5 be respectively in the utility model fluorescent tube bright/close the circuit theory diagrams of control circuit, sample circuit and signal processing circuit.
Embodiment
A kind of electronic ballast for fluoresent lamp with frequency converting and preheating functions, comprise Switching Power Supply, Switching Power Supply is given control circuit and fluorescent tube 6 power supplies respectively, described Switching Power Supply output 18V direct current is to control chip 3, the Switching Power Supply output DC is depressed into fluorescent tube 6, and fluorescent tube 6 adopts the Switching Power Supply power supply, has guaranteed the stability of control circuit, guaranteed the stable of fluorescent lamp operation state simultaneously, luminous flux has advantages of higher stability simultaneously.Microprocessor 1, frequency converting and preheating circuit 4 link to each other with control circuit respectively, and control circuit links to each other with fluorescent tube 6 by half-bridge power control circuit 5, also comprises protective circuit 7, and fluorescent tube 6 links to each other with microprocessor 1 by protective circuit 7, as shown in Figure 1, 2.Three fluorescent lamp ballasts are jointly by same Switching Power Supply power supply, and three fluorescent tubes are respectively by three fluorescent lamp ballast controls.
As shown in Figure 1, 2, described control circuit comprise fluorescent tube bright/close control circuit 2 and control chip 3, described control chip 3 adopts IC SG2525 chip, microprocessor 1 passes through fluorescent tube, and bright/pass control circuit 2 links to each other with the signal input part of IC SG2525 chip, described frequency converting and preheating circuit 4 comprises time-delay sample circuit 4a and analog switching circuit 4b, time-delay sample circuit 4a links to each other with the signal input part of IC SG2525 chip by analog switching circuit 4b, and the signal output part of IC SG2525 chip links to each other with fluorescent tube 6 by half-bridge power control circuit 5.Described protective circuit 7 is made up of sample circuit 7a and signal processing circuit 7b, and fluorescent tube 6 links to each other with signal processing circuit 7b by sample circuit 7a, and signal processing circuit 7b links to each other with microprocessor 1.Time-delay sample circuit 4a acquired signal by the operating frequency of analog switching circuit 4b control IC SG2525 chip, is sent to fluorescent tube 6 through half-bridge power control circuit 5 again, thus the operational factor of control fluorescent tube 6.By Switching Power Supply output 18V direct current after filtration wave circuit infeed the VCC end of IC SG2525 chip, produce the PWM waveform, produce alternating voltages through half-bridge power control circuit 5 again, light the fluorescent tube 6 of fluorescent lamp through the resonance effect that starts electric capacity and inductance.
As shown in Figure 3, described fluorescent tube is bright/and close control circuit 2 and comprise resistance R 20, microprocessor 1 connects the 2nd pin of optocoupler U2 by resistance R 20, the 1st pin of optocoupler U2 was connected resistance R 15 and was connect+the 5V direct current, the 3rd pin ground connection of optocoupler U2, the 4th pin of optocoupler U2 connects the base stage of triode Q2 by resistance R 5, the emitter of triode Q2 is by resistance R 6 ground connection, the collector electrode of triode Q2 is connected to the base stage of triode Q1 by resistance R 4, the collector electrode of triode Q1 links to each other with the positive pole of diode D1, the negative pole of diode D1 connects the feeder ear of control chip 3, one end of resistance R 3 links to each other with the emitter of triode Q1, and the other end of resistance R 3 links to each other with the collector electrode of triode Q2.Fluorescent tube is bright/and to close control circuit 2 be to come the power supply VCC of control IC SG2525 chip to realize by the signal that microprocessor 1 provides, be not to realize switch lamp by cutting off civil power output, can avoid the fluorescent tube 6 of fluorescent lamp is impacted, prolong the useful life of fluorescent lamp.
Shown in Fig. 4,5, described sample circuit 7a comprises diode D11, the positive pole of diode D11 links to each other with the filament of fluorescent tube 6, the negative pole of diode D11 links to each other with the positive pole of diode D7, the negative pole of diode D7 links to each other with an end of resistance R 27, resistance R 27 is connected with resistance R 28, and the other end of resistance R 28 links to each other with the negative pole of voltage stabilizing didoe D8 with signal processing circuit 7b respectively, the plus earth of voltage stabilizing didoe D8.Described signal processing circuit 7b comprises amplifier U3, the 3rd pin of amplifier U3 links to each other with resistance R 28, the 1st pin of amplifier U3 links to each other with the 2nd pin of linear optical coupling U4, the 5th pin of linear optical coupling U4 and the 3rd pin of amplifier U5, the 1st pin of amplifier U5 links to each other with microprocessor 1 through resistance R 32.Protective circuit 7 is to gather output voltage by amplifier U3 to send into linear optical coupling U4; outputing to amplifier U5 by linear optical coupling U4; send into microprocessor 1 by amplifier U5 again; the advantage of this kind protection be can be real-time the various abnormalities of judging fluorescent tube 6, as do not insert abnormalities such as fluorescent tube 6, open filament, filament short circuit can both be by microprocessor 1 reflecting accurately and timely.
Frequency converting and preheating partly by preheating, trigger starter, light three phases and carry out successively, it is very short to lighting process time to trigger starter, has guaranteed that like this fluorescent lamp enters stable state rapidly.The circuit frequency of starting working is 60KHZ, and lower in the pressure drop at fluorescent tube 6 two ends, deficiency avoids filament to sustain damage because of hard breakdown so that fluorescent tube 6 activates starter under cold conditions.After warm-up phase, circuit work frequency descends with fast speeds, and when dropping to the resonance frequency of half-bridge load, higher voltage appears in fluorescent tube 6 two ends lights fluorescent tube 6 starters, promptly enters normal ignition phase later on.Utilize the method for frequency converting and preheating, no consumption power, and warm-up time and preheat curent can be regulated by the parameter that outward element is set, easy to adjust and pre-heat effect good, prolonged the life-span of fluorescent lamp.