The drive selection and design skills of LED street lighting design full revelation

Power consumption of the power tube is divided into two parts, switching losses and conduction losses. Note that most applications especially mains LED street light drive applications , damage to switches larger than conduction losses. Switching losses and power tube cgd and cgs and chip drive capability and working frequency, so the power to solve the heat pipe can be solved from the following aspects :
A, not one-sided based on resistance MOS power transistor size to choose , because resistance is smaller , cgs and cgd greater the capacitance . If the cgs is 250pF 1N60 around , 2N60 around the cgs is 350pF , 5N60 around the cgs to 1200pF , the difference is too great, choose the power tube, enough on it .
B, the rest is the frequency and chip drive capability , and here talk about frequency. Frequency and conduction losses are proportional , so the power tube heating , the first to think about is not frequency selection bit high. To find ways to reduce the frequency it ! But note that , when the frequency is lowered, in order to get the same load capacity , the peak current is bound to become large or larger inductance , which are likely to cause the inductor into saturation region . If the inductor saturation current is large enough , you can consider the CCM (continuous current mode ) to change into DCM ( discontinuous current mode ) , so you need to add a load capacitance of .

This is also the user during commissioning of the more common phenomenon , mainly by two aspects of down- lead . Input voltage and load voltage ratio is small, large system disturbances . For the former, be careful not to load voltage is set too high , although the load voltage, high efficiency will be high.
For the latter , you can try the following aspects:
a, the minimum current setting and then a small point ;
b, clean point wiring , in particular the critical path sense ;
c, the inductor selection of small dots or use closed circuit inductance ;
d, an RC low-pass filter it, this effect a little bad , C consistency is not good, the deviation little big, but it should be enough for lighting . In any case no benefit reduced frequency , only harm , they must be resolved.

Many user response , the same driving circuit for the production of the inductor is not a problem , the production of the inductor current with b becomes smaller. In such cases, to look at the inductor current waveform. Some engineers did not notice this phenomenon, directly regulates sense resistor or current operating frequency to achieve the required to do so may seriously affect LED street light life. So, before the design , reasonable calculation is necessary, if the parameters of theoretical calculations and debugging parameters a bit far worse , to consider whether reduced frequency and transformer is saturated . Transformer saturation , L becomes smaller , resulting in transmission delay caused by the sharp increase in the peak current increment , then the LED will also increase the peak current . In the premise of constant average current , can only look at a bad light .

We all know that LED ripple too large, then , LED life will be affected . For the LED ripple effect too much , some of the LED plant represents less than 30% are acceptable, but that was not validated . Recommendations or try to control a small point . If the heat is not good solution , LED must be derated . Some experts also hope to give specific indicators , otherwise affect LED promotion.
For this article, I believe you will find LED driver design is not difficult , we must be aware of, as long as computed before commissioning , commissioning measurements, debugging aging , I believe we can easily engage in the LED .

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