Four LED street lamp lighting will see solutions

LED street lamp is a very important application in LED lighting. On the premise of energy saving save electricity, the trend of LED street lamp to replace traditional street lamp is more and more obvious. On the market, there are many kinds of LED street lamp power supply design. Early design more emphasis on the pursuit of low cost; To the recent consensus gradually formed, high efficiency and high reliability is the most important thing.

the article is mainly aimed at several different applications of LED lights, put forward the suitable architecture, and analyzes their advantages and disadvantages, so that readers can according to the specific conditions and design of street lamp types, find the most suitable solution.

plan a direct AC input, LED respectively do constant current control of six strings

in this paper introduces several kinds of schemes, this scheme should be the highest efficiency, the circuit of the lowest cost solution ( FIG. 1) 。 With photoelectric coupler directly on primary side circuit back control, regulate the output voltage. Compared with other traditional schemes, the scheme of switching loss less. Fix the CS voltage on 0. 25 v, were LED constant current control of six strings. IC can detect the position of the FB, fix the lowest voltage the string of leds on 0. 5V。 At this time due to the string of leds Vf value is the sum of the different, the pressure drop will fall on the MOS tube, lead to some loss. If it is the general Vf points BIN the LED, after the screening loss should be controlled within 2%, less than the general switch loss.

the scheme has the advantage of high efficiency, low cost, the disadvantage is that the AC input, need more research and development costs. The scheme is suitable for AC could be used directly to the input of street lamp.

2 input DC or battery, LED respectively do constant current control of six strings

it USES more list of booster structure design, and before a similar LED drive way, difference from instead of DC or AC input from the battery input ( FIG. 2) 。 The design of the low voltage side sensing as long as selecting the appropriate MOS tube, LED to considerable number. Relative to the AC input scheme, its design is relatively simple. But due to the switch more a booster, efficiency is relatively low.

the scheme design of the method is simple, low cost of circuit, the disadvantage is low efficiency. It is suitable for the street lamp solar cells or by adapter input.

some scheme SanChan string step-down structure vendors still like to use a single string design, advantage is easy of maintenance, and can do modular design. Different power of street lamp can use the same article lamp, as long as the replacement panel, with different amounts of light, can make all sorts of different power street lamps. But its drawback is that each string need independent power supply module, cost is higher, and the structure of the step-down to withstand voltage of LED is limited by the number of IC. In the example shown in figure 3, LED up to 14, if you want to design article 20 w lamp, LED will need to use the 700 ma. In order to make the highest efficiency, it is necessary to adjust the input voltage on the number of leds, namely the output voltage of the adapter. 10 star LED, for example, if you want to achieve the highest efficiency, will have to adjust the input voltage to about 42 v.

the scheme has the advantage of high efficiency step-down structure, single string design, configuration, more flexible, high cost disadvantage is circuit, LED series number is limited by IC pressure. It is suitable for the street lamp through the adapter input.

scheme of four single string structure of booster RT8480

the same single string design, step-up structure ( Figure 4) Will a step-down structure efficiency is low, but the number of leds in series is no longer restricted to IC pressure, but is determined by MOS, thus it can be more leds in series. Because most of the solar cell output voltage is not high, so suitable for solar street lamps use booster structure. And selects the current mode of constant current design, can make the output current is less affected by the input voltage change, the battery full and fast without electricity, can let the brightness of the street lamps to maintain the same.

the scheme has the advantage of number series LED IC pressure without limit, the disadvantage is that the circuit cost is higher, lower efficiency is step-down structure. It is suitable for solar street lamps.

in the table below for the LED street lamp four kinds of power supply design schemes are compared and the advantages of sorting.

power network