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LED Street Lighting Power supply

Jason

Hello All,

As we know, LED is used moreand more on street lighting, in the future, LED will replace the traditional street lighting bulb. Many supplier have there own power supply solution for LED street lighting, such as NXP, ON, PI,TI, Fairchild and so on, some solution is isolated Fly-back and some is non-isolated high voltage Buck to drive LED bulb, some solution use PFC controller and some use Valley PFC circuit to increase power factor. The question is which solution is more popular for the LED street lighting? isolated or non-isolated,  PFC controller or Valley PFC circuit?

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  • Hi Jason,

     

    The term ''valley PFC'' is probably the method to switch the PFC FET on when the voltage on the drain is the lowest. This is called ZVS (Zero Voltage Switching) and helps to reduce the turn on losses in the MOSFET. PFC techniques are often mandatory for a product (depends on power rating and field of use). Isolated or not has often to do with safety aspects. If you use a not isolated topology the chamber where the LEDS are (including heatsink) is connected to mains (live) and should have sufficient insulated towards any touchable parts. Flyback is an easy topology, but has less efficient than buck, the voltage on the MOSFET are higher (higher max Vds device) and the transformer is used less efficient (transformer = coupled inductor) but if you require an mains insulated application this would be an good choice.

     

    Best regards, Enrico Migchels

  • in reply to enrico.migchels

    Hi,Enrico

    Thanks for your help.

    I agree with what you said. There are so many method to light the LED when I want to design a LED street lighting, but it is difficult to choose. I want to know which is more popular, PFC+LLC+LED driver? Or PFC+Flyback? Or Valley fill+HV Buck? Or Single PFC? Too hard to choose.

    By the way,''valley PFC''  I've said means a very simple and low cost PFC circuit. You can see the circuit in the following picture. This circuit will improve power factor when you not use a initiative power factor correction.

     

    image

  • in reply to Jason

    Hi Jason,

     

    I know the Valley Fill circuit, it has disadvantages also. Factor factor is one thing, but the mains current distortion (MHR) is another. The MHR is not very good for the Valley Fill circuit, it draws nasty current spikes from the mains. The output voltage ripple is also high, but this is probably no issue for the second stage (feedback regulation is fast enough). I would probably go for the PFC (400Vdc boost converter) and LLC. The LLC can act as a current source for the LEDS.

     

    Best regards, Enrico Migchels

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  • in reply to Jason

    Hi Jason,

     

    I know the Valley Fill circuit, it has disadvantages also. Factor factor is one thing, but the mains current distortion (MHR) is another. The MHR is not very good for the Valley Fill circuit, it draws nasty current spikes from the mains. The output voltage ripple is also high, but this is probably no issue for the second stage (feedback regulation is fast enough). I would probably go for the PFC (400Vdc boost converter) and LLC. The LLC can act as a current source for the LEDS.

     

    Best regards, Enrico Migchels

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