Three common LED street lamp power supply design scheme
As a kind of LED power supply, LED street lamp power supply is an important component of the current domestic lighting market, and is gradually replacing the traditional road lighting mode. As far as the current market situation of street lamp power supply is concerned, high frequency and high reliability have gradually become the two directions that many new products focus on when designing.
First of all, the LED street lamp power supply scheme to share with you is an indirect AC output, and the design scheme to do constant current mastery for 6 series LED discrimination. This design idea is the design scheme with the highest frequency and the lowest channel profit on the market at present, and its circuit design diagram is shown in Figure 1 below. As can be seen from Figure 1, in this LED power supply scheme, the photoelectric meshing device is indirectly used to master the advanced side path stop backtracking and adjust the input voltage. Compared with some lighting schemes previously used in China, the switch consumption of this scheme is less. The voltage flow of CS is 0.25V, and the constant current master is done for the identification of 6 strings of leds. The IC will detect the position of FB and set the lowest voltage string of leds to flow at 0.5V. This is because the total number of Vf values of each string of leds is inconsistent, and the resulting pressure drop will fall on the MOS tube and cause some consumption. If it is normal for the Vf BIN to select the LED at that time, the consumption should be able to grasp within 2%, less than the normal switch consumption.
Compared with the traditional street lighting design scheme, this new scheme has the advantage of high frequency and low profit, and is suitable for street lamps that can be indirectly output with AC. Correspondingly, the biggest problem of this scheme is that AC output needs more development profits.
The second LED power supply solution to be shared next is a DC or battery pack output, which is a street lighting design with constant current mastery for 6 string LED discrimination. The scheme mainly adopts the idea of multi-series heating structure, its own LED driving form is similar to the first scheme, and the main difference between the two is that the AC output is changed to DC or by the battery pack output, the circuit design drawing of the scheme is shown in Figure 2 below.
From the design diagram in Figure 2, we can see that in this power system, if the high-voltage side sensing needs to meet the lighting needs, it is necessary to choose the appropriate MOS tube, and the LED can string equal number of lighting points under the premise of selecting the field effect tube. Absolutely in the AC output plan, this design scheme is relatively easy, but because there is a heating switch in this power system design, the frequency is absolutely lower. Compared with the first scheme, the advantages of this design scheme are easy to conceive and low channel profit, and its disadvantages are low frequency. In practical applications, the scheme is more suitable for the moonlight battery pack for night lighting or the street lamp with adaptive weight output.
The LED street light power supply with a single series of step-down structure is the third more common design scheme that we want to share with you. The circuit system drawing of this design scheme is shown in Figure 3 below. As a scheme that can achieve modular design, the change of the scheme is relatively simple, but its drawback is that each series requires an independent power module, compared with the first two schemes, the production profit is higher, and the buck structure will make the number of leds subject to the voltage of the limited IC. As can be seen from Figure 3, the LED in this power system is up to 14, if you want to imagine a 20W light strip, you need to use 700mA LED. In order to make the frequency reach the highest, it must be aligned with the number of leds to adjust the output voltage, that is, the input voltage that matches the weight. Taking 10 leds as an example, if you want to reach the highest frequency, you must adjust the output voltage to about 42V inside and outside.
Compared with the two schemes described above, the advantages of this LED power supply design scheme are that the buck construction frequency is higher, the sensitivity of the single series design and configuration is relatively high, and it is appropriate to go through the street lamp with adaptive weight output. The disadvantage is that the channel profit is higher, and the number of leds in parallel is limited by IC voltage resistance during the design process.
