Light Emitting Diode Selection Circuit

An LED selection circuit, for switching between 120 Volts, Alternating Current (VAC) and 240 VAC operation of an LED driver, comprising

• a rectifier converting an input AC line voltage to a pulsating DC voltage;
• multiple LED strings comprising a first LED string and a second LED string;
• multiple current sources, each current source comprising
• an error amplifier having a first input end, a second input end and an output end;
• and
• a transistor having a drain, a source and a gate, the drain of the transistor being connected to a bottom side of the corresponding LED string, the source of the transistor being connected to the second input end of the error amplifier and a current sensing resistor, the gate of the transistor being connected to the output end of the error amplifier;
• a high voltage (HV) diode being coupled between the first LED string and the second LED string, wherein an anode of the HV diode is connected to the first LED string;
• a PMOS module being connected to the rectifier, the second LED string and a cathode of the HV diode;
• a peak sensing module being connected to the rectifier and sensing peak information of the pulsating DC voltage;
• a second NMOS transistor;
• and
• a controller receiving the peak information from the peak sensing module, and turning the second NMOS transistor to configure the first LED string and the second LED string being connected in parallel or in series.

An LED selection circuit, for switching between 120 VAC and 240 VAC operation of an LED driver, comprising

• a rectifier converting an input AC line voltage to a pulsating DC voltage;
• multiple LED strings comprising a first LED string and a second LED string, wherein the first LED string and the second LED string are connected in series as default;
• multiple current sources, each current source comprising
• an error amplifier having a first input end, a second input end and an output end;
• and
• a transistor having a drain, a source and a gate, the drain of the transistor being connected to a bottom side of the corresponding LED string, the source of the transistor being connected to the second input end of the error amplifier, the gate of the transistor being connected to the output end of the error amplifier;
• a high voltage (HV) diode being coupled between the first LED string and the second LED string, wherein an anode of the HV diode is connected to the first LED;
• a NMOS module comprising
• a switching component;
• a third NMOS transistor comprising
• a gate being coupled to the switching component;
• a source being connected to a cathode end of the HV diode;
• and
• a drain being connected to the rectifier;
• and
• a capacitor;
• a blocking diode;
• a resistor, the capacitor and the resistor are parallel connected between the gate and the source of the third NMOS transistor;
• a voltage source being coupled to the gate of the third NMOS transistor through the switching component and the blocking diode;
• and
• a fourth NMOS transistor comprising
• a gate being coupled to the controller;
• and
• a drain being connected to the source of the third NMOS transistor;
• and
• a controller determining current through a first feedback resistor, and turning the third NMOS transistor and the fourth NMOS transistor to configure the first LED string and the second LED string being connected in parallel or in series.