Selection of suitable driving power supply for outdoor LED drive power supply in series and parallel mode

The function of LED driving power supply is to convert the input voltage of power grid into a constant current power supply suitable for LED work, which makes the whole LED lamp work steadily and reliably. Therefore, as an LED lamp design engineer, we must master how to connect in series and in parallel according to different LED modes. Choose the appropriate driving power supply.

Next, I will introduce several key points of the selection driver separately.

1. Input voltage, according to the occasion of lamp application and the state to determine the input voltage of the LED lamp, the input voltage range of the LED driving power supply must include the voltage range used by the lamp.

For example: LED lamps are used in China, we all know that China's electricity market is 220V+/-10%, so the driving power supply voltage should include the range of 198-242, then the driving power supply with input voltage of 176-264V should be selected. Of course, if the supplier's input voltage is 90-265V, it would be better.

2. Output current and LED are all driven by constant current, so the selection of constant current power supply needn't be said. The determination of output current depends on two factors: a. the number of parallel LEDs; B. the predetermined working current of a single LED (everyone knows that the rated working current of 1W is 350mA, but not all manufacturers do it according to the rated current in practice. It is mainly based on the heat dissipation capacity of its shell (like a cup with a capacity of 1 liter, but in practice, very few people use it to hold 1 liter of water, because it will spill out carelessly).

For example: 98 LEDs, with 14 series and 7 parallel, the working current of a single LED is set at 350 mA, so the output current is 300 mA (predetermined working current of a single LED)*7 (number of parallel connections)=2100 mA.

3. Output voltage range, the output voltage of constant current source must be a range, it will keep adjusting on voltage according to different loads, and output current is constant, the selection of output voltage is an estimated range, it is impossible to accurately put in place, the estimated source is the forward voltage drop range provided by the LED manufacturer. Number of cascades.

For example, the specification of an LED manufacturer describes that under 350mA, the maximum forward voltage drop of the LED is 3.5V and the minimum value is 2.8V. Then design a 98-LED lamp with 14 series and 7 parallel, then choose the output voltage range of the LED driver power supply should be: the minimum output value = 2.8V (the minimum voltage drop of the LED)* 14 = 39.2V, the maximum output. Value = 3.5V (maximum voltage drop of LED)* 14 = 49V, then the range of output voltage of the selected LED power supply should be 35V - 50V, which is more reasonable, leaving a little margin, so it will be more secure.

In fact, the most important is the above parameters, of course, it is impossible to find the same power supply as the parameters we calculated in the market at once, so when we choose, we should follow the following rules:

1. The input voltage range can only be wider than our actual input voltage range.

2. The difference of output current equals to each LED, and the error should not exceed 5%.

3. The range of output voltage can only be wider than that calculated by us, but not narrower than that calculated by us.

4. Others, such as power supply volume, temperature resistance, shell material, IP protection level, input and output wires, whether these parameters conform to a certain certification are determined according to the actual application. These parameters do not match at least can light up the LED, if the first three do not meet, even the LED will not normally light up.