驅動高電壓、高亮度LED

　　hvhb發光二極管，當驅動在PFC升壓配置，具有小尺寸、高功率因數、效率高、成本低的優點，且復雜度低，CFL照明解決方案提供具有競爭力的替代。

　　作為消費者，公司，甚至國家尋找低成本、高效節能的照明光源，發光二極管（LED），和緊湊型熒光燈（CFL）已成為主要的替代品。這兩種解決方案都是可行的，但差別很大。CFL照明設備價格低廉，但開啟速度較慢，表現出較差的調光性能。另一方面，LED具有“抓拍”的特性和暗淡的效果，但由于成本的采用而變得緩慢。

　　半導體制造商繼續創造新的LED驅動組件，以降低系統復雜性和成本。與此同時，LED生產商們正在大力提高高亮度LED的效率（發光效率），以減少所需的LED數量，并減少調節它們所需的功率。

　　One such innovation is the introduction of high-voltage， high-brightness （HVHB） LEDs. These LEDs require a much higher voltage to start current flow and， therefore， light emission. These new LEDs present new challenges and opportunities. While originally designed to be self-driven directly off of an AC line， factors such as low efficiency， low power factor， and the inability to dim limit the number of applications they can serve.

　　In Figure 1 we see the problems in driving these LEDs directly off of the AC line. In an effort to meet the entire voltage range （90 to 135 Vac or 207 to 253 Vac）， the forward voltage drop （Vf） must be at the lowest AC voltage or lower. This means that when the voltage is at the upper limit of the scale， the voltage falls across the current-limiting resistor. This creates a loss and greatly reduces efficiency. This also creates heat， which may limit the life of the LED.