Light emitting diode driver

A lighting system comprising:

• a ballast generating an AC (alternating current) voltage;
• and
• a light emitting diode (LED) tube including a plurality of LEDs and an LED driver;
• wherein the LED driver includes
• an AC-to-DC converting module coupled to the ballast for receiving the AC voltage from the ballast, and converting the AC voltage into an intermediate DC (direct current) voltage, and wherein a voltage value of the intermediate DC voltage is smaller than or equal to a voltage value of a predetermined threshold voltage, and
• a DC-to-DC converting module coupled to the AC-to-DC converting module for receiving the intermediate DC voltage, and converting the intermediate DC voltage to a DC output voltage for driving the plurality of LEDs;
• wherein the AC-to-DC converting module includes a rectifying-and-filtering circuit including:
• a first input terminal, a second input terminal, a third input terminal and a fourth input terminal coupled to the ballast for receiving the AC voltage,
• an output terminal coupled to the DC-to-DC converting module and configured to output the intermediate DC voltage,
• a first diode including an anode coupled to the first input terminal, and a cathode coupled to the output terminal,
• a second diode including an anode coupled to a reference node, and a cathode coupled to the second input terminal,
• a third diode including an anode coupled to the third input terminal, and a cathode coupled to the output terminal,
• a fourth diode including an anode coupled to the reference node, and a cathode coupled to the fourth input terminal,
• a first resistor coupled between the first and second input terminals, and
• a second resistor coupled between the third and fourth input terminals.

A light emitting diode (LED) driver of an LED tube, the LED tube including a plurality of LEDs and being operatively associated with a ballast, the LED driver comprising:

• an AC-to-DC converting module coupled to the ballast for receiving an AC (alternating current) voltage, and converting the AC voltage into an intermediate DC (direct current) voltage, and wherein a voltage value of the intermediate DC voltage is smaller than or equal to a voltage value of a predetermined threshold voltage;
• and
• a DC-to-DC converting module coupled to the AC-to-DC converting module for receiving the intermediate DC voltage, and converting the intermediate DC voltage to a DC output voltage for driving the plurality of LEDs;
• wherein the AC-to-DC converting module includes:
• a rectifying-and-filtering circuit coupled to the ballast for receiving the AC voltage, wherein the rectifying-and-filtering circuit is configured to generate, in response to the AC voltage, the intermediate DC voltage which is provided to the DC-to-DC converting module;
• and
• a voltage clamping circuit coupled to the rectifying-and-filtering circuit for receiving the intermediate DC voltage, and configured to clamp the intermediate DC voltage;
• wherein the rectifying-and-filtering circuit includes:
• a first input terminal, a second input terminal, a third input terminal and a fourth input terminal coupled to the ballast for receiving the AC voltage;
• an output terminal coupled to the voltage clamping circuit and the DC-to-DC converting module and configured to output the intermediate DC voltage;
• a first diode including an anode coupled to the first input terminal, and a cathode coupled to the output terminal;
• a second diode including an anode coupled to a reference node, and a cathode coupled to the second input terminal;
• a third diode including an anode coupled to the third input terminal, and a cathode coupled to the output terminal;
• a fourth diode including an anode coupled to the reference node, and a cathode coupled to the fourth input terminal;
• a first resistor coupled between the first and second input terminals;
• and
• a second resistor coupled between the third and fourth input terminals.