In 2011, the world's lighting use entered a new era, Australia has taken the lead in prohibiting the use of incandescent lamps, which kicked off the large-scale popularization of LED lamps. In addition, with the EU countries, Japan, Canada and other countries will be banned in 2012. Incandescent lamps, LED lighting, lighting penetration will be further enhanced, which makes the Nuggets green lighting revolution in China thousands of LED lighting manufacturers rejoice - because a huge market is about to open, and this time is the Chinese manufacturers. However, it should be noted that LED lamps should be popularized, not only need to significantly reduce costs, but also need to solve the problem of energy efficiency and reliability. How to solve these problems, Doug Bailey, vice president of marketing for Power Integrations, shared the design of high-efficiency and high-reliability LED lamps. Five advices.
Try not to use electrolytic capacitors
Do you want to use electrolytic capacitors in the LED driver circuit? There are supporters and opponents. Supporters believe that if the temperature of the board can be controlled well, the purpose of extending the life of the electrolytic capacitor can be achieved in turn, for example, the high temperature of 105 degrees is 8000 hours. Electrolytic capacitor, according to the current electrolytic capacitor life estimation formula "every 10 degrees decrease in temperature, the life is doubled", then its working life is 16000 hours in a 95 degree environment, and the working life is 32000 hours in a 85 degree environment, at 75 The working life in the environment is 64000 hours. If the actual working temperature is lower, the life will be longer! From this point of view, as long as the selection of high-quality electrolytic capacitors has no effect on the life of the driving power supply!
Other proponents believe that the low-frequency flicker caused by the high ripple current caused by electroless capacitors will cause physiological discomfort to some people's eyes. The large amplitude of low-frequency ripple will also cause some digital camera equipment to appear poor. A brightly lit grid of flickering lights. Therefore, high-quality light source lamps still need electrolytic capacitors. However, opponents believe that electrolytic capacitors will naturally age. In addition, the temperature of LED lamps is extremely difficult to control, so the life of electrolytic capacitors will inevitably decrease, thus affecting the life of LED lamps.
In this regard, Doug Bailey believes that in the input part of the LED driver circuit, electrolytic capacitors can be considered. In fact, PI can be omitted by using LinkSwitch-PH of PI. PI's single-stage PFC/constant current design can save designers a big deal. Capacitance capacitors, in the output circuit, high-voltage ceramic capacitors can be used instead of electrolytic capacitors to improve reliability. "Some people design a two-stage circuit, using a 400V electrolytic capacitor at the output, which will seriously affect For the reliability of the circuit, it is recommended to use a ceramic capacitor for a single-stage circuit," he stressed. “For industrial applications that do not pay much attention to dimming, high temperature environments, and high reliability, I strongly recommend not using electrolytic capacitors for design.â€
If the LED luminaires are not designed to be very powerful, Doug recommends using an LED driver with integrated MOSFETs because the benefit of this is that the integrated MOSFETs have less on-resistance and generate less heat than discrete, in addition to integrated MOSFETs. The controller and the FET are generally together, and generally have a thermal shutdown function. When the MOSFET overheats, the circuit is automatically turned off to protect the LED illuminator. This is very important for the LED luminaire, because the LED luminaire is generally small and difficult to dissipate air. . "Sometimes LEDs can cause people to burn because of overheating, but our solution has never been like this," he said.
Try not to use electrolytic capacitors
Do you want to use electrolytic capacitors in the LED driver circuit? There are supporters and opponents. Supporters believe that if the temperature of the board can be controlled well, the purpose of extending the life of the electrolytic capacitor can be achieved in turn, for example, the high temperature of 105 degrees is 8000 hours. Electrolytic capacitor, according to the current electrolytic capacitor life estimation formula "every 10 degrees decrease in temperature, the life is doubled", then its working life is 16000 hours in a 95 degree environment, and the working life is 32000 hours in a 85 degree environment, at 75 The working life in the environment is 64000 hours. If the actual working temperature is lower, the life will be longer! From this point of view, as long as the selection of high-quality electrolytic capacitors has no effect on the life of the driving power supply!
Other proponents believe that the low-frequency flicker caused by the high ripple current caused by electroless capacitors will cause physiological discomfort to some people's eyes. The large amplitude of low-frequency ripple will also cause some digital camera equipment to appear poor. A brightly lit grid of flickering lights. Therefore, high-quality light source lamps still need electrolytic capacitors. However, opponents believe that electrolytic capacitors will naturally age. In addition, the temperature of LED lamps is extremely difficult to control, so the life of electrolytic capacitors will inevitably decrease, thus affecting the life of LED lamps.
In this regard, Doug Bailey believes that in the input part of the LED driver circuit, electrolytic capacitors can be considered. In fact, PI can be omitted by using LinkSwitch-PH of PI. PI's single-stage PFC/constant current design can save designers a big deal. Capacitance capacitors, in the output circuit, high-voltage ceramic capacitors can be used instead of electrolytic capacitors to improve reliability. "Some people design a two-stage circuit, using a 400V electrolytic capacitor at the output, which will seriously affect For the reliability of the circuit, it is recommended to use a ceramic capacitor for a single-stage circuit," he stressed. “For industrial applications that do not pay much attention to dimming, high temperature environments, and high reliability, I strongly recommend not using electrolytic capacitors for design.â€
If the LED luminaires are not designed to be very powerful, Doug recommends using an LED driver with integrated MOSFETs because the benefit of this is that the integrated MOSFETs have less on-resistance and generate less heat than discrete, in addition to integrated MOSFETs. The controller and the FET are generally together, and generally have a thermal shutdown function. When the MOSFET overheats, the circuit is automatically turned off to protect the LED illuminator. This is very important for the LED luminaire, because the LED luminaire is generally small and difficult to dissipate air. . "Sometimes LEDs can cause people to burn because of overheating, but our solution has never been like this," he said.
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