Three-terminal LED and drive circuit thereof

Abstract

A three-terminal LED and drive circuit thereof. The three-terminal LED ( 1 ) has an anode, a cathode and a gate. The three-terminal LED ( 1 ) includes a LED group ( 3 ) formed by connecting at least one LED in series and a gate circuit ( 2 ), the first end ( 21 ) of the gate circuit ( 2 ) and the anode of the LED group ( 3 ) are connected with the anode of the three-terminal LED ( 1 ), the second end ( 22 ) of the gate circuit ( 2 ) and the cathode of the LED group ( 3 ) are connected with the cathode of the three-terminal LED ( 1 ), the third end ( 23 ) of the gate circuit ( 2 ) is connected with the gate of the three-terminal LED ( 1 ).

I claim:   
     
       1. A three-terminal LED drive circuit comprising a DC source and at least one branch, wherein the branch is connected between a positive terminal and a negative terminal of the DC source; the branch comprises at least two three-terminal LEDs connected sequentially and a current source having an input end, an output end and a control end in series; each of the three-terminal LEDs comprises an anode, a cathode, a gate, and an LED string comprising one LED or at least two LEDs connected in series, and a gate circuit, a first end of the gate circuit and the anode of the LED string are connected with the anode of the three-terminal LED, a second end of the gate circuit and the cathode of the LED string are connected with the cathode, a third end of the gate circuit is connected with the gate; based on N-MOSFET, the gate circuit comprises a N-channel MOSFET (Q 20 ), a diode (D 20 ) and a resistor (R 20 ), the drain of N-channel MOSFET (Q 20 ) is connected with the first end of the gate circuit, the source of N-channel MOSFET (Q 20 ) is connected with the second end of the gate circuit, the anode of diode (D 20 ) is connected with the third end of the gate circuit, the cathode of diode (D 20 ) is connected with the gate of N-channel MOSFET (Q 20 ), one end of resistor (R 20 ) is connected with the cathode of diode (D 20 ), and the other end of resistor (R 20 ) is connected with the source of N-channel MOSFET (Q 20 ); controlled by the gate, the gate circuit has three operating states of cut-off, fully conduct and linear; for current flowing from the anode to the cathode: the current flows in the LED string when the gate circuit works in cut-off state; the voltage drop between the anode and the cathode is minimal and the LED string is bypassed when the gate circuit works in fully conduct state; the resistance between the anode and the cathode is variable and the voltage drop is variable accordingly, and equals a variable resistor when the gate circuit works in linear state; the at least two three-terminal LEDs are connected sequentially via connection of the anode of one three-terminal LED to the cathode of another three-terminal LED; and the control end provided by the current source is connected with all the gates of the at least two three-terminal LEDs. 
     
     
       2. The three-terminal LED according to  claim 1 , wherein the gate circuit further comprises a diode (D 21 ) and a zener (Z 20 ), the anode of the diode (D 21 ) is connected with the anode of the zener (Z 20 ), the cathode of the zener (Z 20 ) is connected with the drain of the N-channel MOSFET (Q 20 ), the cathode of the diode (D 21 ) is connected with the gate of the N-channel MOSFET (Q 20 ). 
     
     
       3. The three-terminal LED drive circuit of  claim 1 , wherein the current source comprises a N-MOSFET (Q 90 ), a NPN transistor (Q 91 ), a diode (D 90 ), a zener (Z 90 ), a capacitor (C 90 ), three resistors (R 90 , R 91 , and R 92 ), a N-MOSFET (Q 92 ) and a P-MOSFET (Q 93 ), the resistor (R 90 ) is a current sense resistor, one end of the resistor (R 90 ) is connected with the source of the N-MOSFET (Q 90 ), the other end of the resistor (R 90 ) is connected with the output end of the current source, the source of the N-MOSFET (Q 90 ) is also connected with the base of the transistor (Q 91 ), the emitter of the transistor (Q 91 ) is connected with the output end of the current source, the collector of the transistor (Q 91 ) is connected with one end of the resistor (R 91 ), the other one end of the resistor (R 91 ) is connected with the positive end of the DC source, the N-MOSFET (Q 92 ) and P-MOSFET (Q 93 ) are in totem pole connection, both gate of the N-MOSFET (Q 92 ) and P-MOSFET (Q 93 ) are connected with the collector of the transistor (Q 91 ), the drain of the N-MOSFET (Q 92 ) is connected with the positive end of the DC source, the drain of the P-MOSFET (Q 93 ) is connected with the output end of the current source, both sources of the N-MOSFET (Q 92 ), P-MOSFET (Q 93 ) are connected with the control end of the current source, the drain of the N-MOSFET (Q 90 ) is connected with the input end of the current source, the gate of the N-MOSFET (Q 90 ) is connected with the control end of the current source, the resistor (R 92 ) and capacitor (C 90 ) are in parallel and then in series with the diode (D 90 ), the anode of the diode (D 90 ) is connected with the collector of the transistor (Q 91 ), the other conjunction of the resistor (R 92 ) and the capacitor (C 90 ) is connected with the emitter of the transistor (Q 91 ), the cathode of the zener (Z 90 ) is connected with the collector of the transistor (Q 91 ), the anode of the zener (Z 90 ) is connected with the emitter of the transistor (Q 91 ). 
     
     
       4. The three-terminal LED drive circuit of  claim 1 , wherein the DC source is obtained from AC source via a rectifier, a filter, and a surge suppression circuit before the rectifier.