Dimmer compatible LED driving apparatus with adjustable bleeding current

Patent metadata

Field	Value
Publication number	US-9282609-B2
Application number	US-201514738609-A
Country	US
Kind code	B2
Filing date	Jun 12, 2015
Priority date	Jun 13, 2014
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

An LED driving apparatus includes a rectifier bridge generating a DC bus voltage, a bus capacitor coupled between the output terminal of the rectifier bridge and a reference ground, a voltage sensing circuit generating a voltage sensing signal indicative of the DC bus voltage, a bleeding circuit providing a bleeding current for the bus capacitor, a switching converter configured to convert the DC bus voltage into a driving signal to drive an LED, a dimming mode detector detecting whether the LED driving apparatus is coupled to a leading edge dimmer or a trailing edge dimmer based on the voltage sensing signal, and a bleeding control circuit generating a control signal to control the bleeding circuit based on the voltage sensing signal, the leading edge dimming mode signal and the trailing edge dimming mode signal.

First claim

We claim:

1. A controller used in an LED driving apparatus, wherein the LED driving apparatus includes a rectifier bridge providing a DC bus voltage at an output terminal, a bus capacitor coupled between the output terminal of the rectifier bridge and a reference ground, a bleeding circuit configured to provide a bleeding current for the bus capacitor and a switching converter configured to convert the DC bus voltage into a driving signal to drive an LED, and wherein the controller comprises:
a dimming mode detector configured to receive a voltage sensing signal indicative of the DC bus voltage, wherein based on the voltage sensing signal, the dimming mode detector detects whether the LED driving apparatus is coupled to a leading edge dimmer or a trailing edge dimmer, and generates a leading edge dimming mode signal and a trailing edge dimming mode signal; and
a bleeding control circuit coupled to the dimming mode detector, wherein based on the voltage sensing signal, the leading edge dimming mode signal and the trailing edge dimming mode signal, the bleeding control circuit generates a control signal to control the bleeding circuit; wherein
if the LED driving apparatus is coupled to a leading edge dimmer, the bleeding circuit will provide a first bleeding current when the voltage sensing signal becomes smaller than a first threshold voltage;
if the LED driving apparatus is coupled to a trailing edge dimmer, the bleeding circuit will provide a second bleeding current when the voltage sensing signal becomes smaller than a second threshold voltage.

2. The controller of claim 1 , wherein the dimming mode detector compares a rising time during which the voltage sensing signal increases from a fourth threshold voltage to a third threshold voltage with a first time threshold to detect whether the LED driving apparatus is coupled to a leading edge dimmer, and wherein the dimming mode detector compares a falling time during which the voltage sensing signal decreases from a fifth threshold voltage to a sixth threshold voltage with a second time threshold to detect whether the LED driving apparatus is coupled to a trailing edge dimmer.

3. The controller of claim 1 , wherein if the LED driving apparatus is not detected to be coupled to either a leading edge dimmer or a trailing edge dimmer in a predetermined time from the LED driving apparatus being powered on, the LED driving apparatus will be deemed as not being coupled to any dimmer and the bleeding circuit will stop providing the bleeding current.

4. The controller of claim 1 , wherein the bleeding control circuit comprises:
a first comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive the voltage sensing signal, the second input terminal is configured to receive the first threshold voltage, and wherein the first comparator compares the voltage sensing signal with the first threshold voltage and generates a first comparison signal at the output terminal;
a second comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive the voltage sensing signal, the second input terminal is configured to receive the second threshold voltage, and wherein the second comparator compares the voltage sensing signal with the second threshold voltage and generates a second comparison signal at the output terminal;
a first AND gate having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the dimming mode detector to receive the leading edge dimming mode signal, the second input terminal is coupled to the output terminal of the first comparator to receive the first comparison signal, the output terminal is configured to provide a first control signal; and
a second AND gate having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the dimming mode detector to receive the trailing edge dimming mode signal, the second input terminal is coupled to the output terminal of the second comparator to receive the second comparison signal, the output terminal is configured to provide a second control signal.

5. The controller of claim 1 , wherein the dimming mode detector comprises:
a third comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive the voltage sensing signal, the second input terminal is configured to receive a third threshold voltage, and wherein the third comparator compares the voltage sensing signal with the third threshold voltage and generates a third comparison signal at the output terminal;
a fourth comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive the voltage sensing signal, the second input terminal is configured to receive a fourth threshold voltage, and wherein the fourth comparator compares the voltage sensing signal with the fourth threshold voltage and generates a fourth comparison signal at the output terminal;
a first timing and comparing circuit having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output terminal of the third comparator, the second input terminal is coupled to the output terminal of the fourth comparator, and wherein based on the third and fourth comparison signals, the first timing and comparing circuit calculates a rising time of the voltage sensing signal, compares the rising time with a first time threshold and generates a leading edge detection signal at the output terminal;
a fifth comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a fifth threshold voltage, the second input terminal is configured to receive the voltage sensing signal, and wherein the fifth comparator compares the voltage sensing signal with the fifth threshold voltage and generates a fifth comparison signal at the output terminal;
a sixth comparator having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is configured to receive a sixth threshold voltage, the second input terminal is configured to receive the voltage sensing signal, and wherein the sixth comparator compares the voltage sensing signal with the sixth threshold voltage and generates a sixth comparison signal at the output terminal;
a second timing and comparing circuit having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is coupled to the output terminal of the fifth comparator, the second input terminal is coupled to the output terminal of the sixth comparator, and wherein based on the fifth and sixth comparison signals, the second timing and comparing circuit calculates a falling time of the voltage sensing signal, compares the falling time with a second time threshold and generates a trailing edge detection signal at the output terminal; and
a mode signal generator having a first input terminal, a second input terminal, a third input terminal, a first output terminal and a second output terminal, wherein the first input terminal is configured to receive a power on signal, the second input terminal is coupled to the output terminal of the first timing and comparing circuit, the third input terminal is coupled to the output terminal of the second timing and comparing circuit, and wherein based on the power on signal, leading edge detection signal and trailing edge detection signal, the mode signal generator generates the trailing edge dimming

Assignees

• Chengdu Monolithic Power Sys

Inventors

• Kuang Naixing
• Cai Jiali
• Feng Lin

Classifications

• H05B45/14

  using electrical feedback from LEDs or from LED modules · CPC title

• H05B33/0845 Primary

  Electricity · mapped topic

• H05B33/0815

  Electricity · mapped topic

• H05B45/3725 Primary

  Switched mode power supply [SMPS] · CPC title

• H05B45/385

  using flyback topology · CPC title