Detecting circuit for short of LED array and LED driving apparatus using the same

Patent metadata

Field	Value
Publication number	US-9888552-B2
Application number	US-201213693241-A
Country	US
Kind code	B2
Filing date	Dec 4, 2012
Priority date	Dec 7, 2011
Publication date	Feb 6, 2018
Grant date	Feb 6, 2018

Abstract

A detection circuit configured to detect a short in a plurality of LED arrays is provided. The detection circuit includes a voltage measuring unit, a short detecting unit, and a detection control unit. The voltage measuring unit is configured to measure respective feedback voltages of the plurality of LED arrays and output a lowest measured feedback voltage as a first feedback voltage. The short detecting unit is configured to detect the short in the LED arrays using the measured feedback voltages. The detection control unit is configured to control the short detecting unit to stop short detection operation, when the first feedback voltage exceeds a first preset reference voltage.

First claim

What is claimed is:

1. A detection circuit to detect a short in LED arrays, the detection circuit comprising:
a voltage measuring unit configured to measure respective feedback voltages of the LED arrays, and to output a first feedback voltage;
a short detecting unit configured to detect the short in the LED arrays, by using the measured feedback voltages; and
a detection control unit configured to control the short detecting unit to stop the detection of the short in each of the LED arrays, in response to the first feedback voltage exceeding a first preset reference voltage and to control the short detecting unit to perform the detection of the short, in response to the first feedback voltage being below a second preset reference voltage, the second preset reference voltage being below the first preset reference voltage.

2. The detection circuit of claim 1 , wherein the first preset reference voltage is preset to be greater than the first feedback voltage during a normal operation.

3. The detection circuit of claim 1 , wherein the voltage measuring unit is configured to output the first feedback voltage, based on a lowest measured feedback voltage among the LED arrays, except for a feedback voltage of an LED array in an ‘off’ state.

4. The detection circuit of claim 1 , wherein the detection control unit comprises a comparator configured to output a high signal, in response to the first feedback voltage exceeding the first preset reference voltage.

5. The detection circuit of claim 1 , wherein the detection control unit comprises a hysteresis comparator configured to:
output a ‘low’ signal, in response to the first feedback voltage exceeding the first preset reference voltage, and
output a ‘high’ signal, in response to the first feedback voltage being below a second preset reference voltage, the second preset reference voltage comprising a voltage level lower than the first preset reference voltage.

6. The detection circuit of claim 1 , further comprising:
a delay unit configured to:
delay the first feedback voltage, and
provide the delayed signal to the detection control unit, for a duration that a dimming signal to drive the LED arrays is ‘on’.

7. The detection circuit of claim 6 , wherein the delay unit comprises:
a delay device configured to delay the dimming signal;
an AND gate configured to:
receive the dimming signal and the delayed dimming signal, and
output a reduced dimming signal; and

a MUX configured to provide the detection control unit with the first feedback voltage, for the duration that the reduced dimming signal is ‘on’.

8. The detection circuit of claim 7 , wherein the MUX is configured to:
provide the detection control unit with the first feedback voltage, for the duration that the output signal of the AND gate is ‘high’, and
provide the detection control unit with ground voltage, for the duration that the output signal of the AND gate is low′.

9. An LED driving apparatus, comprising:
LED arrays;
an LED driving circuit configured to:
provide the LED arrays with a driving voltage and a constant current; and

a detection unit configured to:
measure respective feedback voltages of the LED arrays, and
detect a short in the LED arrays; and

a detection control unit configured to:
control the detection unit to perform the detection of the short in each of the LED arrays, in response to a first feedback voltage being below a second preset reference voltage; and
control the detection unit to stop the detection of the short in each of the LED arrays, in response to the first feedback voltage exceeding a first preset reference voltage,
wherein the first preset reference voltage is greater than the second preset reference voltage.

10. The LED driving apparatus of claim 9 , wherein the detection unit comprises:
a voltage measuring unit configured to:
measure respective feedback voltages of the LED arrays, and
output a lowest measured feedback voltage as a first feedback voltage.

11. The LED driving apparatus of claim 10 , wherein the first preset reference voltage is preset to be greater than the first feedback voltage during a normal operation.

12. The LED driving apparatus of claim 10 , wherein the voltage measuring unit is configured to output the first feedback voltage, based on the lowest feedback voltage among the LED arrays, except for a feedback voltage of an LED array in an ‘off’ state.

13. The LED driving apparatus of claim 10 , wherein the detection control unit comprises a comparator configured to output a ‘low’ signal, in response to the first feedback voltage exceeding the first preset reference voltage.

14. The LED driving apparatus of claim 10 , wherein the detection control unit comprises a hysteresis comparator configured to
output a ‘low’ signal, in response to the first feedback voltage exceeding the first preset reference voltage, and
output a ‘high’ signal, in response to the first feedback voltage being below a second preset reference voltage, the second preset reference voltage comprising a voltage level lower than the first preset reference voltage.

15. The LED driving apparatus of claim 10 , wherein the detection unit further comprises:
a delay unit configured to:
delay the first feedback voltage, and
provide the delayed signal to the detection control unit, for a duration that a dimming signal that drives the LED arrays is ‘on’.

16. The LED driving apparatus of claim 15 , wherein the delay unit comprises:
a delay device configured to delay the dimming signal;
an AND gate configured to:
receive the dimming signal and the delayed dimming signal, and
output a reduced dimming signal; and

a MUX configured to provide the detection control unit with the first feedback voltage, for the duration of an ‘on’ interval of the reduced dimming signal.

17. The LED driving apparatus of claim 16 , wherein the MUX is configured to
provide the detection control unit with the first feedback voltage, for the duration that the output signal of the AND gate is ‘high’, and
provide the detection control unit with ground voltage, for the duration that the output signal of the AND gate is low′.

18. The LED driving apparatus of claim 9 , further comprising:
a control unit configured to stop an operation of the LED driving circuit, in response to a detection of a short in the LED arrays.

19. A detection circuit to detect a short in LED arrays, the detection circuit comprising:
a voltage measuring unit configured to measure respective feedback voltages of the LED arrays, and to output a first feedback voltage;
a short detecting unit configured to detect the short in the LED arrays, by using the measured feedback voltages; and
a detection control unit configured to enable the short detecting unit to detect the short based on whether:
the first feedback voltage is increasing and is less than a first preset reference voltage, or

the first feedback voltage is decreasing and is below a second preset reference voltage, which is lower than the first preset reference voltage.

20. The detection circuit of claim 19 , wherein the detection control unit is further configured to, in response to the first feedback voltage exceeding the first preset reference voltage, control the short detecting unit to not detect the short.

Assignees

• Magnachip Semiconductor Ltd

Inventors

• Kang Tae Kyoung
• Lim Gyu Ho
• Ryu Beom Seon
• Min jun sik

Classifications

• H05B47/23 Primary

  of two or more light sources connected in series · CPC title

• H05B45/50 Primary

  responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits · CPC title

• H05B37/036 Primary

  Electricity · mapped topic

• H05B33/089

  Electricity · mapped topic

• G01R19/165

  Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values · CPC title