To the application, and solar cells, batteries, controller and the LED lighting system is made up of more seriously. However, with the price of electricity generated by the solar cells at present is more expensive, so the LED lighting system using energy-saving control. This paper discusses several LED control, analysis of the working principle of this, find energy-saving control, stressing the control green lights suitable for solar-powered LED lighting system 4th generation light source white LED is a semiconductor light-emitting devices. The luminescence mechanism, structure, production process is completely different from incandescent, fluorescent and HID lamps. Light emitting diode is a semiconductor injection electroluminescence devices, semiconductor light source as a novel, it features 111: low voltage-driven, small size, good direction, firm structure, high luminous efficiency (at present up to 10 long life (20000h), fast response and other characteristics, is one of the most competitive new energy-saving light sources. Less energy consumption LED, is an energy-saving light sources, currently white-light LED lighting effect has been to 251mW, exceeds the level of incandescent and LED technology is developing rapidly now. Ushered in the home LED lamp lighting, road lighting, moving lights, military lighting, equipment, stage lighting and buildings, and surgical lighting field of 121. due to the LED and low UV radiation (without filters) features, progressive application of white LED light sources for lighting the Chiang Kai-shek. Using solar power batteries, controller and LED the. Solar cells produce electricity, under the control of the controller to the battery, under the control of the same controller, batteries store electrical energy into the appropriate code-driven LED light. In such a system, due to the expensive solar cells and batteries are expensive, coupled with their large size and heavy weight, improved efficiency is particularly important (actually any use of LED lighting, primarily to energy-saving, non-solar powered LED lighting systems also stressed that efficient) from the efficiency point of view, solar lighting system there are three main issues which are worth focusing on. One is how to make a solar cell to power to charge a battery problem, the second is how to minimize energy consumption makes LED brightness issue needs, its three grouped together is how to reduce the LED luminous efficiency losses. On the first question will be covered in a future article, this article focuses on improving the efficiency of LED drive methods. Due to single LED by issued of flux also enough big, thus regardless of for lighting also is for signal, are of – lighting device or LED letter signal loaded Sun battery large LED to series and parallel of way connection in with using (LED of low radiated sex allows will they layout into close of displayed structure) this certainly will increased control of difficulty, but they of control principle is communicates of.
1 direct direct control mode control LED circuit as shown, r be played a limited role in the picture, VT control LED the work, for example LED operating current is 20mA, long more than this current work, easily LED, semiconductor chip burnt out. In order to ensure the LED current 20nA, according to the size of the power supply voltage and voltage drop of VT, determine the size of the resistor. You can find the control requirements are achieved by controlling ways, but due to current-limiting resistor r consumes power, power supply voltage, the higher the r consumes more power. For example a lot in TTL circuits use 5-volt power drive, in resistance to consume 50% even more power. The other hand, if the proposed lower driving voltage or LED in series to reduce ohmic losses, this is valid for a certain range, but resistance is too small it will be difficult to play a stabilizing role, little fluctuations in voltage will cause the brightness change.
Due to this method of control is simple, so use an LED control methods. Powered by solar energy or others aimed at the energy-saving LED lighting system, this control is not scientific.
After the diode conduction voltage slightly increased, flows through the led current rise very quickly, and the luminous intensity of the light emitting diodes as the current increases almost linearly increased, luminous intensity increased linearly with increasing current LEDs suitable for work with pulse and difficult to heat. In average current and DC current equal situation Xia, pulse work glow strength more big, combined glow diode response speed fast of features, so used by shows of control circuit, analysis the circuit of work principle, known in control voltage k for pulse signal low electric usually, VT as, LED ends of voltage for power voltage and inductance anti-potential of and, so circuit for LED boost control circuit. When the control voltage v; for high power pulse signal, control tubes VT-pass, flowing through the inductor current in r for the equivalent resistance of the circuit, that is to say l, r, more, the current rises faster, the maximum current is equal to the/R. when VT deadline at the current through the LED and not mutations, LED began to work. Resistor, current increases rapidly, but the maximum current, inductive energy storage of small, thus the supply resistors and LED time shorter and inductor, current rise slowly, current has not reached the maximum value, transistor has been closed, causes the inductance energy storage also smaller, thus supplying resistance and LED short elapsed time handy. This on need the circuit of parameter and pulse frequency has a reasonable of match, makes LED of maximum pulse work current should makes chip IN knot district temperature is equal to highest knot temperature can expressed for/=AeUT,U is PN knot ends of voltage, I is through diode of current, a, is reverse saturation, Ur called temperature voltage equivalent, glow diode of v-characteristics as by shows, by figure disc to see-Dang added voltage is greater than valve value voltage pass voltage and switch tube of saturated pressure drop and the switch tube of as frequency fT size. , Is the inductance value different switching cycle the LED voltage is the same as the measured waveform. From see, voltage waveform is 3 buck control way buck control way circuit as, analysis this circuit learned that, dang VT guide pass Shi, current from power e began flows through inductance l and switch tube VT to to, is inductance current established of process, its current of changes law available formula (1) expressed, dang VT as Shi, is will inductance in the of energy through LED discharge of process, its discharge current of changes law for a not continuous of, description in Guide pass stage inductance in the by storage of power insufficient to provides to LED, In voltage waveform in the appeared has oscillation, due to light pass density is with current density of increased and into are proportion increased, such LED of glow brightness on will weakened, this showed that pulse frequency and accounted for empty than of selected, should consider inductance size, and inductance had big, is in VT guide pass Shi, established up inductance current of time had long, such in whole guide pass during within, inductance in the by store of energy enough big, led to LED of brightness reduced; inductance had small, although in VT guide pass Shi, easy makes inductance in the of current reached maximum value, Of inductance energy storage is still insufficient to provide enough power to the LED, voltage Oscillation phenomenon can also occur, in addition, the cut-off frequency switch switch breakover time, thereby affecting the current process, so should optimize the configuration of circuit parameters. Is the inductance parameters and configure other parameters in the control circuit is more reasonable LED of voltage waveform.
I is VT as Shi of current, r is inductance of wire resistance and LED equivalent resistance of and, on also of initial current, r more big, 4 conclusion resistance of power also more big, to storage can on more fast to was resistance consumption off, due to LED of resistance is basic not variable of, can through reduced inductance of resistance, reached save power; l more big, inductance storage can more big, its discharge time more long, LED glow time more long, with discharge time of extended, discharge current gradually reduced, Flows through the led current is reduced, its luminous intensity is decreased, for which a fixed LED luminous intensity, pulse frequency and duty cycle when it should, considering the size of the power supply voltage, inductance, LED by founder.
Lighting systems, General design, configuration of solar panels and batteries are to be met in the case of 3-5 days in a row for the rainy days, still able to normal lighting. Discussed in the above three LED control, direct control methods are not economical.
This three species control way are available pulse signal control switch tube of guide pass, in pulse signal accounted for empty than not variable Shi, pulse of average current is equal to DC current pulse work Shi can makes LED glow more big, in seeking allows maximum peak current Shi, needed consider LED of maximum pulse work current should makes chip PN knot district temperature is equal to highest allows knot temperature, to guarantee LED to pulse work way of glow efficiency best, should optimization configuration control circuit in the of the parameter.