早期LED大部分都是應用於指示燈，而隨著技術逐漸成熟，提升了LED的發光效率，致使LED應用於照明領域。然而成本不斷下降，讓具有省電的LED 照明應用成為大家的省電的首選。 LED照明應用種類繁多，在此則選用杯燈作為此次LED燈源。杯燈的主要應用於商店內照明，通常使用於在櫥櫃裡投射商品，以突顯商品優質及與眾不同。在此之前則都由鹵素燈作為燈源，可是耗電與使用壽命短是主要問題。 LED杯燈規格應用為輸入電源交流與直流皆12V及負載電流350mA。LED在傳統控制模式應用時，主要會有降壓型與升降壓型控制模式。降壓型控制模有著整體效率高，但是當輸入電壓低於規格時，LED電流將非在設定範圍內。升降壓型則在輸入電壓較低時仍可以穩定LED於設定範圍內，但是整體效率較低。 本論文中所提出的LED 控制模式的改良型電路架構，則是整合降壓型與升降壓型兩著之間電路。藉由輸入電源經電阻分壓與參考電壓比較，並依輸入電源的高低來讓整體控制電路操作降壓型或升降壓型，致使LED電流穩定。Light-emitting diode (LED) always are applied in indicator lighting before.As the technique of the LED is mature, the luminous efficiency of the LED is upgraded.Therefore,the LED are applied in lighting area now. Moreover,the cost keep going down,the power-saving LED are attractive us . There are many species of LED applied in lighting area,In this thesis a cup light selected as the LED lighting source.The cup light is applied as a shop lighting.It is always used project onto commodity in cupboard.It is can highlight commodity quality and different.Prior to this is used lighting source of Halogen.However,its problems are high power consumption and short life. The application specification of the cup light LED is input voltage AC/DC 12 Volts and loading current is 350mA.The tradition control modes of the LED application are Buck and Buck-Boost modes.The Buck control mode has higher energy efficiency.But when the input voltage is under the specification,the LED current will not setting into the specification range.The Buck-Boost can stable LED current for setting range when input voltage is under.But it is lower efficiency. This thesis improves the circuit architecture of the LED control mode.It is integrate with Buck and Buck-Boost circuit.By input voltage via resistor divide and reference voltage compare,it is can control operating mode with Buck and Buck-Boost by input voltage.It is can stable LED current.
