The design of LED driving power supply is not difficult, but it must be well known. As long as we can calculate before debugging, measure during debugging and age after debugging, I believe anyone can do LED well.

1, LED current size

Everyone knows that too much LED ripple will affect LED life, but there is no specific index at present.

2, the chip is hot

This is mainly aimed at the high-voltage driver chip with built-in power modulator, which reduces the power consumption of the chip, does not introduce additional power consumption, and does a good job of heat dissipation.

3. Power tube heating

On this issue, I also saw someone posting on the forum. The power consumption of power tube is divided into two parts, switching loss and conduction loss. In the application of LED commercial power drive, the switching loss is much greater than the conduction loss. The switching loss is related to the cgd and cgs of the power tube, the driving ability of the chip and the working frequency, so the heating of the power tube can be solved from the following aspects:

A. MOS power transistors cannot be selected unilaterally according to the on-resistance, because the smaller the internal resistance, the larger the capacitance of cgs and cgd.

B, the rest is frequency and chip driving ability. Here, we only talk about the influence of frequency. The frequency is also proportional to the conduction loss, so when the power tube heats up, we should first think about whether the frequency is a bit high. When the frequency decreases, in order to obtain the same load capacity, it is necessary to increase the peak current or increase the inductance, which may cause the inductance to enter the saturation region. If the saturation current of the inductor is large enough, we can consider changing CCM (continuous current mode) to DCM (discontinuous current mode), so we need to add a load capacitor.

4. Frequency reduction of working frequency

Downconversion is mainly caused by two aspects. The ratio of input voltage to load voltage is small, and the system interference is large. For the former, be careful not to set the load voltage too high. Although the load voltage is high, the efficiency will be high. For the latter, we can try from the following aspects: a, set the minimum current to a smaller point; B, clean wiring, especially the critical path of sensing; C, selecting a small inductance point or an inductance point with a closed magnetic circuit; D, adding RC low-pass filtering, this effect is a bit bad, the consistency of C is not good, and the deviation is a bit big, but the lighting should be enough.

5, the choice of inductance or transformer

In view of the fact that the working voltage of high-power light-emitting diodes is only 3V, 220V alternating current is converted into direct current through full-bridge rectification, and the voltage drop across the full-bridge is about 1.8V, and the power utilization efficiency of only driving one light-emitting diode is only 60%. More than three LEDs must be connected in series to work, so that the total power efficiency can exceed 80%. According to the principle of synthesizing white light with three primary colors, three high-power light-emitting diodes (LEDs) of red, green and blue 1W are connected in series, and the brightness equivalent to 3W white light-emitting LED can be obtained. At the same time, six kinds of color lights can be combined to meet people's preferences for changing color lights.