Multi-channel led driver with overheating protection capabilities

Patent metadata

Field	Value
Publication number	US-2017339756-A1
Application number	US-201715478986-A
Country	US
Kind code	A1
Filing date	Apr 4, 2017
Priority date	May 17, 2016
Publication date	Nov 23, 2017
Grant date	—

Abstract

An apparatus to drive a multi-channel light emitting diode (LED) array includes switching transistors connected to LED strings of the multi-channel LED array, error amplifiers connected to the switching transistors, each of the error amplifiers being configured to control current flowing through the LED string to have a target magnitude, and overheating protection circuits connected to the switching transistors, each of the overheating protection circuits being configured to regulate current flowing through a respective switching transistor to have a magnitude less than or equal to the target magnitude.

First claim

What is claimed is:

1 . An apparatus to drive a multi-channel light emitting diode (LED) array, comprising:
switching transistors connected to LED strings of the multi-channel LED array; error amplifiers connected to the switching transistors, each of the error amplifiers being configured to control current flowing through the LED string to have a target magnitude; and overheating protection circuits connected to the switching transistors, each of the overheating protection circuits being configured to regulate current flowing through a respective switching transistor to have a magnitude less than or equal to the target magnitude.

2 . The apparatus of claim 1 , wherein the LEDs included in the LED strings have different forward bias voltages.

3 . The apparatus of claim 1 , wherein each of the switching transistors is a lateral diffused metal-oxide-semiconductor field effect transistor (LDMOSFET), a junction gate field effect transistor (JFET), a metal-oxide-semiconductor field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or a bipolar junction transistor (BJT).

4 . The apparatus of claim 3 , wherein the error amplifiers are differential amplifiers or operational amplifiers.

5 . The apparatus of claim 1 , wherein each of the switching transistors is grounded via a sensing resistor, each of the switching transistors comprises a first terminal connected to the respective LED string and a second terminal connected to the respective sensing resistor, and wherein each of the overheating protection circuits is configured to provide a current dividing path between the first and second terminals of the respective switching transistor.

6 . The apparatus of claim 5 , wherein a resistive element and a switch are provided in the current dividing path.

7 . The apparatus of claim 6 , wherein the resistive element comprises a resistor, resistors connected in parallel, a metal-oxide-semiconductor field-effect transistor (MOSFET), or a bipolar junction transistor (BJT).

8 . The apparatus of claim 6 , wherein the switch comprises a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor (BJT).

9 . The apparatus of claim 8 , wherein the switch is configured to be switched on in response to an electrical quantity indicative of a magnitude of current flowing through the respective sensing resistor being greater than or equal to a voltage level.

10 . The apparatus of claim 9 , wherein the electrical quantity indicative of the magnitude of the current flowing through the respective sensing resistor comprises a voltage level at the second terminal of the respective switching transistor, each of the overheating protection circuits comprises a comparator configured to compare the voltage level at the second terminal of the respective switching transistor with the voltage level, and an output from the comparator is inputted into a control input terminal of the one transistor in accordance with a pulse width modulation (PWM) signal from a PWM signal generator.

11 . The apparatus of claim 8 , wherein the switch is configured to be switched in response to an electrical quantity indicative of a magnitude of current flowing through the respective sensing resistor and a pulse width modulation (PWM) signal from a PWM signal generator.

12 . An apparatus to protect a light emitting diode (LED) driver from overheating, comprising:
switching transistors connected to LED strings; and shunt current branches respectively connected in parallel to the switching transistors, wherein each of the shunt current branches comprises a resistive element and a switch connected in series, and the switch is configured to be switched on in response to a condition being met.

13 . The apparatus of claim 12 , wherein each of the switching transistors is grounded via a sensing resistor and the condition comprises a condition that an electrical quantity indicative of a magnitude of current flowing through the respective sensing resistor is greater than or equal to a voltage level.

14 . The apparatus of claim 13 , wherein the electrical quantity indicative of the magnitude of the current flowing through the respective sensing resistor comprises a voltage drop across the respective sensing resistor.

15 . The apparatus of claim 12 , wherein the resistive element comprises one of a resistor, resistors connected in parallel, a metal-oxide-semiconductor field-effect transistor (MOSFET), and a bipolar junction transistor (BJT).

16 . The apparatus of claim 12 , wherein the switch comprises one of a metal-oxide-semiconductor field-effect transistor (MOSFET) and a bipolar junction transistor (BJT).

17 . The apparatus of claim 12 , wherein a resistance of the resistive element is determined based at least in part on a magnitude of a drain-source voltage of the switching transistor prone to causing overheating of the switching transistor and a magnitude of current intended to be flowing into the shunt current branch.

18 . An apparatus for driving light emitting diode (LED) strings, comprising:
constant current control circuits connected to the LED strings, each of the constant current control circuits being configured to control current flowing through a respective LED string and comprising a switching transistor connected to the respective LED string; and overheating protection circuits connected to the constant current control circuits, each of the overheating protection circuits being configured to provide a current dividing path for the current flowing through the respective LED string in response to detection of the current having a magnitude greater than or equal to a magnitude of current, wherein the current is divided between the respective switching transistor and the current dividing path by the provision of the current dividing path.

19 . The apparatus of claim 18 , wherein each of the switching transistors comprises a first terminal connected to the respective LED string and a second terminal, and the magnitude of current is determined based, at least, in part on an amount of power consumption by the switching transistor prone to causing a temperature of the switching transistor to increase beyond a maximum allowable temperature and a maximum voltage drop between the first and second terminals of the switching transistor that is expected from a statistically determined deviation in forward bias voltage between the LED strings.

20 . The apparatus of claim 18 , wherein each of the switching transistors is grounded via a sensing resistor, each of the switching transistors comprises a first terminal connected to the respective LED string and a second terminal connected to the respective sensing resistor, the current dividing path is formed between the first and second terminals of the respective switching transistor, and a resistive element and a switch are provided in the current dividing path.

21 . The apparatus of claim 20 , wherein the switch is controlled to be switched on in response to a voltage drop across the respective sensing resistor being greater than or equal to a voltage level.

22 . The apparatus of claim 20 , wherein the resistive element comprises one of a resistor, resistors connected in parallel, a metal-oxide-semiconductor field-effect transistor (MOSFET), and a bipolar junction transistor (BJT).

23 . The apparatus of claim 20 , wherein the switch comprises one of a metal-oxide-semiconductor field-effe

Assignees

• Magnachip Semiconductor Ltd

Inventors

• Ahn Hyun Mo
• Cui zhi yuan
• Lee Seung Hwan
• Hwang In Ho
• Jung James
• Lim Gyu Ho

Classifications

• H05B45/395

  Linear regulators · CPC title

• H05B45/46 Primary

  having LEDs disposed in parallel lines · CPC title

• G09G2330/021

  Power management, e.g. power saving · CPC title

• H05B45/37 Primary

  Converter circuits · CPC title

• G09G2330/045

  Protection against panel overheating · CPC title