LED TUBE DRIVER CIRCUITRY FOR BALLAST AND NON-BALLAST FLUORESCENT TUBE REPLACEMENT

• US 20160081147A1
• Filed: 09/17/2014
• Published: 03/17/2016
• Est. Priority Date: 09/17/2014
• Status: Active Grant

• Current Assignee: Greco-Tech Industries Inc.
• Original Assignee: Greco-Tech Industries Inc.
• Inventors: GUANG, Luo Hua
• Granted Patent: US 9,338,853 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F21K 9/27 Retrofit light sources for lighting devices with two fittings for each light source, e.g. for substitution of fluorescent tubes
• CPC Class Codes: F21K 9/278 Arrangement or mounting of circuit elements integrated in the light source
• CPC Class Codes: F21V 23/002 Arrangements of cables or conductors inside a lighting device, e.g. means for guiding along parts of the housing or in a pivoting arm
• CPC Class Codes: F21V 23/006 the substrate being distinct from the light source holder
• CPC Class Codes: F21V 23/009 the casing being inside the housing of the lighting device
• CPC Class Codes: F21V 23/026 Fastening of transformers or ballasts
• CPC Class Codes: F21Y 2103/10 comprising a linear array of point-like light-generating elements
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05B 45/345 Current stabilisation; Maintaining constant current
• CPC Class Codes: H05B 45/3578 Emulating the electrical or functional characteristics of discharge lamps
• CPC Class Codes: H05B 45/36 Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An LED lamp tube and driver circuit that is direct replacement for fluorescent tubes with or without ballasts, that works with standard AC high voltage current input, with high frequency pulse current input, or with lower voltage input. The tube is wired to receive the current that is input from any two electrode pins from among the pairs of pins at the ends of the tube, which house the driver circuitry. The input current is converted to DC through a rectifier circuit, is filtered of unwanted frequencies and voltage through a filter circuit, and is controlled with a step-down constant current circuit to drive an LED array within the tube.

Claims

1. An LED driver circuit for fluorescent tube replacement comprising:

a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having respectively a first pair of electrode pins and a second pair of electrode pins;

b) a rectifier circuit comprising a first rectifier sub-circuit connected to the first pair of electrode pins and a second rectifier sub-circuit connected to the second pair of the electrode pins, each rectifier circuit having at least a first input diode and a second input diode, each of the input diodes having an input lead connected to one of the electrode pins, and the input diodes having output leads that arc connected to provide DC output from the rectifier circuit;

in which DC output from the rectifier circuit is conducted to a constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

2. The LED driver circuit for fluorescent tube replacement of claim 1, in which the DC output from the rectifier circuit is conducted to the constant current circuit via a filter circuit that filters out surge voltage from the DC output from the rectifier circuit.

3. The LED driver circuit for fluorescent tube replacement of claim 1, in which each of the first and second rectifier sub-circuits has a pair of additional diodes, each pair of additional diodes being looped in parallel with a capacitor connected to the DC output from the rectifier circuit, to provide a stabilizing flyback loop from the DC output of the rectifier circuit back to the input leads of the input diodes.

4. The LED driver circuit for fluorescent tube replacement of claim 1, in which at least three of the input leads each have a fuse in series between the input lead and the input lead'"'"'s-respective input diode.

5. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output.

6. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a temperature-sensitive relay switch that opens if the filter circuit exceeds a safe temperature range for the driver circuit.

7. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises a varistor that grounds excessive voltage spikes in the DC current from the rectifier circuit.

8. The LED driver circuit for fluorescent tube replacement of claim 5, in which the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with a capacitor in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output to ground.

9. The LED driver circuit for fluorescent tube replacement of claim 2, in which the filter circuit comprises at least one capacitor in series with DC output from the rectifier circuit to ground.

10. The LED driver circuit for fluorescent tube replacement of claim 1, in which the constant current circuit is a step-down constant current circuit that converts the DC output from the rectifier circuit to DC suitable for driving the LED light source.

11. The LED driver circuit for fluorescent tube replacement of claim 1, further comprising the LED light source, in which the LED light source is an array of LEDs mounted within the tube, the array receiving DC suitable for driving the LED light source from the constant current circuit.

12. The LED driver circuit for fluorescent tube replacement of claim 1, in which the rectifier circuit is on a first printed circuit board (PCB) located in the first end cap and the constant current circuit is on a second printed circuit board (PCB) located in the second end cap, with two conductor wires running the length of the tube to connect a first pair of electrode pins on the second end cap to their respective input diodes in the rectifier circuit and two short conductors connecting a second pair of electrode pins on the first end cap to their respective input diodes in the rectifier circuit.

13. The LED driver circuit for fluorescent tube replacement of claim 1, in which current output from the rectifier circuit via two rectifier output wires connected to a first 2-pin connector connected at a first end of an LED array board to two conductors to a second 2-pin connector at an opposite end of the LED array board, second 2-pin connector being connected to an input side of the constant current circuit, and an output side of the constant current circuit being connected by a third 2-pin connection to a positive terminal and a negative terminal for electrical supply to the LED array board.

14. The LED driver circuit for fluorescent tube replacement of claim 10, in which the step-down constant current circuit comprises a positive DC output lead to a positive DC output pin and branch circuits that adjust DC voltage and stabilize DC current for the LED light source across the DC output pin and a negative DC output pin.

15. The LED driver circuit for fluorescent tube replacement of claim 14, comprising an integrated circuit (IC) that drives the step-down constant current circuit, keeping the step-down constant current circuit in constant on time operation to achieve low switching losses and a high power efficiency.

16. The LED driver circuit for fluorescent tube replacement of claim 15, further comprising a transistor and in which the step-down constant current circuit performs switching to turn output from the transistor on when the transistor'"'"'s input voltage is low.

17. The LED driver circuit for fluorescent tube replacement of claim 15, in which the integrated circuit (IC) has a current sense pin, a ground pin, a loop compensation pin, an inductor current zero-crossing pin, a power supply pin, and a gate drive pin.

18. The LED driver circuit for fluorescent tube replacement of claim 17, in which a sense resistor is connected across the current sense pin to the ground pin, a resistor-capacitor network driven by the DC output from the rectifier circuit is connected across the loop compensation pin and the ground pin, the inductor current zero-crossing detection pin receives voltage from a resistor divider, the power supply pin receives power for the integrated circuit (IC) from resistors in series with the DC output from the rectifier circuit.

19. The LED driver circuit for fluorescent tube replacement of claim 18, in which the integrated circuit (IC) provides output over-voltage protection and line regulation in conjunction with a loop comprising a diode, a resistor a Zener diode, and a B-side of a DC to DC transformer, on a loop that comprises a resistor to the inductor current zero-crossing detection pin.

20. The LED driver circuit for fluorescent tube replacement of claim 19, in which the gate drive pin is connected to a gate of the transistor via a transistor loop resistor, with feedback current drawn from the sense pin to a ground pin resistor loops also being fed to the transistor loop resistor.

21. The LED driver circuit for fluorescent tube replacement of claim 20, in which a transistor feedback diode receives feedback current from the transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the transistor to receive a DC supply from the drive pin at consistent levels and to enable the transistor to turn off quickly upon the integrated circuit (IC) dropping the DC supply from the drive pin.

22. The LED driver circuit for fluorescent tube replacement of claim 19, in which the transistor feeds the transistor'"'"'s current output via two flyback diodes in series, wired in parallel with a series of a flyback capacitor and a flyback resistor to join the positive DC output lead, and also feeds the transistor'"'"'s current output to an A-side input of the DC to DC transformer having an A-side output connected to a negative output lead for the LED light source.

23. The LED driver circuit for fluorescent tube replacement of claim 22, in which the A-side output of the DC to DC transformer is also connected to an output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor, each of the output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor being bridged in parallel to the positive output pin in order to stabilize output current for the LED light source at a voltage appropriate for the LED array.

26. The LED driver circuit for fluorescent tube replacement of claim 2, in which:

a) the rectifier circuit has two pairs of additional diodes, each pair of additional diodes being looped in parallel with a capacitor connected to the DC output from the rectifier circuit, to provide a stabilizing flyback loop from the DC output of the rectifier circuit back to the input leads of the input diodes;

b) at least three of the input leads each have a fuse in series between the input lead and the input lead'"'"'s respective input diode;

c) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output;

d) the filter circuit comprises a temperature-sensitive relay switch that opens if the filter circuit exceeds a safe temperature range for the driver circuit;

c) the filter circuit comprises a varistor that grounds excessive voltage spikes in the DC current from the rectifier circuit;

f) the filter circuit comprises a combination of a resistor and an inductor in parallel, the combination being in series with a capacitor in series with the DC output of the rectifier circuit to filter out unwanted current frequencies of the DC output to ground;

g) the filter circuit comprises at least one capacitor in series with DC output from the rectifier circuit to ground.

27. The LED driver circuit for fluorescent tube replacement of claim 2, in which:

a) the constant current circuit is a step-down constant current circuit that converts the DC output from the rectifier circuit to DC suitable for driving the LED light source;

b) an LED light source which is an array of LEDs mounted within the tube, the array receiving DC suitable for driving the LED light source from the constant current circuit;

c) the step-down constant current circuit comprises a positive DC output lead to a positive DC output pin and branch circuits that adjust DC voltage and stabilize DC current for the LED light source across the DC output pin and a negative DC output pin;

d) an integrated circuit (IC) drives the step-down constant current, keeping the step-down constant current circuit in constant on-time operation to achieve low switching losses and a high power efficiency;

c) a transistor, the step-down constant current circuit performing switching to turn on output from the transistor when the transistor'"'"'s input voltage is low;

28. The LED driver circuit for fluorescent tube replacement of claim 27, in which:

a) the integrated circuit (IC) has a current sense pin, a ground pin, a loop compensation pin, an inductor current zero-crossing pin, a power supply pin, and a gate drive pin;

b) a sense resistor is connected across the current sense pin to the ground pin, a resistor-capacitor network driven by the DC output from the rectifier circuit is connected across the loop compensation pin and the ground pin, the inductor current zero-crossing detection pin receives voltage from a resistor divider, the power supply pin receives power for the integrated circuit (IC) from resistors in series with the DC output from the rectifier circuit;

c) the integrated circuit (IC) provides output over-voltage protection and line regulation in conjunction with a loop comprising a diode, a resistor a Zener diode, and a B-side of a DC to DC transformer, on a loop that comprises a resistor to the inductor current zero-crossing detection pin;

d) the gate drive pin is connected to a gate of the transistor via a transistor loop resistor, with feedback current drawn from the sense pin to a ground pin resistor loops also being fed to the transistor loop resistor;

e) a transistor feedback diode receives feedback current from the transistor through a transistor feedback resistor connected by at least one ground resistor to ground in order to assist the transistor to receive a DC supply from the drive pin at consistent levels and to enable the transistor to turn off quickly upon the integrated circuit (IC) dropping the DC supply from the drive pin.

29. The LED driver circuit for fluorescent tube replacement of claim 28 in which:

a) the transistor feeds the transistor'"'"'s current output via two flyback diodes in series, wired in parallel with a series of a flyback capacitor and a flyback resistor to join the positive DC output lead, and also feeds the transistor'"'"'s current output to an A-side input of the DC to DC transformer having an A-side output connected to a negative output lead for the LED light source;

b) the A-side output of the DC to DC transformer is also connected to an output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor, each of the output pin capacitor, a polarized electrolytic capacitor, and an LED output bridging resistor being bridged in parallel to the positive output pin in order to stabilize output current for the LED light source at a voltage appropriate for the LED array.

24. An LED driver circuit for fluorescent tube replacement comprising:

a) a tube for enclosing an LED light source, the tube having a first end cap and a second end cap, each of the first and second end caps having a pair of electrode pins;

b) each of the pairs of electrode pins being wired to a respective first rectifier circuit and a second rectifier circuit;

c) each of the first rectifier circuit and the second rectifier circuit having a pair of input diodes, each input diode having an input side that is wired to one of the electrode pins;

d) a first input capacitor connecting a first electrode pin connected to a first input diode in the first rectifier circuit to a first electrode pin connected to a first input diode in the second rectifier circuit, and a second input capacitor connecting a second electrode pin connected to a second input diode in the first rectifier circuit to a second electrode pin connection to a second input diode in the second rectifier circuit;

e) each input diode having an output lead, the output leads being connected to provide a combined DC output from the first rectifier circuit and the second rectifier circuit;

in which DC output from the rectifier circuit is conducted to filter circuit that filters to ground unwanted frequencies of electrical current and filters to ground harmful surges in voltage and in which tilter circuit output is conducted to a step-down constant current circuit that converts the DC output from the rectifier circuit into constant DC output for driving the LED light source.

25. The LED driver circuit for fluorescent tube replacement of claim 24, in which the step-down constant current circuit operates with ON time determined by an integrated circuit (IC) that increases with current to the rectifier circuit increasing to a minimum preselected level, up to a maximum preset ON time for output current when a full load for the LED light source is reached, at which time OFF time for the output current is dictated by the integrated circuit (IC).

30. The LED driver circuit for fluorescent tube replacement of claim 25, in which:

a) the rectifier circuit is on a first printed circuit board (PCB) located in the first end cap and the constant current circuit is on a second printed circuit board (PCB) located in the second end cap, with two conductor wires running the length of the tube to connect a first pair of electrode pins on the second end cap to their respective input diodes in the rectifier circuit and two short conductors connecting a second pair of electrode pins on the first end cap to their respective input diodes in the rectifier circuit;

b) current output from the rectifier circuit via two rectifier output wires connected to a first 2-pin connector connected at a first end of an LED array board to two conductors to a second 2-pin connector at an opposite end of the LED array board, second 2-pin connector being connected to an input side of the constant current circuit, and an output side of the constant current circuit being connected by a third 2-pin connection to a positive terminal and a negative terminal for electrical supply to the LED array board.