| 主权项 |
1. An LED lamp for being mounted to a fixture prepared for a fluorescent lamp and a ballast used with the fluorescent lamp, the LED lamp replacing the fluorescent lamp, the LED lamp comprising a rectifier which receives AC power from the fixture and converts it to DC power, a microcontroller, at least one group of LEDs, and at least one MOSFET device, wherein:
a surge protection device is electrically connected between a DC output of the rectifier and a power supply input pin of the microcontroller; the group of LEDs includes multiple lines of serially connected LEDs, which are connected in parallel to form a first end connected to the DC output of the rectifier and a second end connected to one or more serially connected current-limiting resistors which in turn are connected to a common ground; the gate terminal of the MOSFET device is connected to an output pin of the microcontroller, the drain terminal of the MOSFET device is connected to the second end of the group of LEDs, and the source terminal of the MOSFET device is connected to the common ground, whereby the current-limiting resistors are connected in parallel with a channel that will be created between the drain terminal and the source terminal of the MOSFET device when the gate terminal of the MOSFET device is at a high voltage; and a voltage detection circuit is connected between the DC output of the rectifier and an input pin of the microcontroller for detecting the voltage at the DC output of the rectifier; whereby, according to the voltage detected at the DC output of the rectifier, the microcontroller generates a PWM signal to the output pin thereof which is connected to the gate of the MOSFET device, so that the current flowing through the LEDs is controlled by the PWM signal to flow through the channel created in the MOSFET device and thus the brightness of the LEDs can be controlled accordingly; in the case of an excessively high voltage being detected at the DC output of the rectifier, the microcontroller will generate a low voltage to the output pin thereof, so that the MOSFET device will be turned off and thus the current flowing through the LEDs is unable to flow through the MOSFET device but able to flow through the current-limiting resistors in series therewith, so the current flowing through the LEDs will be limited and thus the LEDs can be protected from damages. |
