How to design led fluorescent lamp better?
The matching of LED fluorescent lamp power supply and lamp board
Choose the most excellent series-parallel connection method. The voltage and current applied to each LED are the same, but the power supply can exert the best performance. Therefore, the best way is to communicate with the power supply manufacturer first and tailor it. Made to order.
LED working current
The rated working current of the general LED is 20 mA, and some factories use the maximum at the beginning, and the design is 20 mA. In fact, the working temperature is very serious under this current. After many comparison tests, it is ideal to design to 17 mA. 30ma is better designed as 25ma
LED working voltage
The recommended operating voltage for general LEDs is 3.0-3.5V. After testing, most of the work is at 3.125V, so the calculation formula of 3.125V is more reasonable.
Series-parallel connection and wide voltage of LED light panels
To make the LED fluorescent lamp work in a relatively wide range of input voltage (AC85-265V), the serial-parallel connection of the LED panel is very important. Since the current power supply is generally a non-isolated step-down power supply, when a wide voltage is required, the output voltage should not exceed 72V, and the input voltage range can reach 85-265V, that is to say, the number of series does not exceed 23 series, and the number of parallel connections Don't be too much, otherwise the working current will be too large and the heat will be serious. It is recommended to use 6-parallel, 8-parallel, 12-parallel, and the total current should not exceed 240 mA.
The relationship between LED series and parallel connection and PFC power factor and wide voltage
At present, there are three types of power supply PFC: one is about 0.65 without PFC dedicated circuit; the other is with passive PFC circuit is about 0.92; the other is made with active active 7527/6561 circuit, PFC can reach 0.99 , But the cost of this scheme is twice as expensive as the second scheme, so more people choose the second scheme. For passive PFC circuits, also called valley-filled PFC circuits, the operating voltage range is half of the peak value of the AC input voltage. Therefore, the number of LED lamp beads in series is up to 28.
Constant current accuracy
Some power supplies on the market have poor constant current accuracy. The popular PT4107, HV9910, BP2808, SMD802 and other constant current solutions have an error of ±8% or ±10%. The constant current error is too large, and it is generally required to be within ±3%. According to the error of 3%, 6 circuits are connected in parallel, and the error of each circuit is about ±0.5%. If 12 circuits are connected in parallel, the error of each circuit is about ±0.25%, which is sufficient. If the accuracy is too high, the cost will increase greatly.
Isolation, non-isolation
Generally, the transformer of the isolation power supply is very large, and it is difficult to put it in. So the general price of isolation is very expensive.
size
Height is the main limiting factor. Generally, the size of T6 tube/T8 requires that the height should not be too high ≤ 9 mm. The height of the T10 tube is ≤15 mm, and the length can be longer, which makes it easier to dissipate heat.
