# US 9,049,762 B2 · Constant voltage dimmable LED driver

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- Number: US 9,049,762 B2
- Document ID: US9049762B2
- Status: Granted
- Kind: B2
- Application number: 13/944,611
- Filed: 2013-07-17
- Published: 2013-11-14
- Granted: 2015-06-02
- Earliest claimed: 2011-04-13
- Applicants: Gang Gary Liu
- Inventors: Gang Gary Liu
- Web page: https://patentgrep.com/patent/US9049762B2

## CPC

- H05B 45/46: having LEDs disposed in parallel lines
- H05B 41/2855: {against abnormal lamp operating conditions}
- H05B 45/37: Converter circuits
- H05B 41/2985: {against abnormal lamp operating conditions}
- Y02B 20/30: Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A constant voltage dimmable LED (Light Emitting Diode) driver is disclosed that is compatible with all types of dimmers, including conventional phase cut (TRIAC) dimmers, and behaves like a conventional constant voltage driver which can be connected to any size of LED load that has a matching voltage rating. The driver produces a continuous train of pulses for driving the LED load and obtains an averaged measure of the voltage at the AC input for controlling the duty cycle of the continuous train of pulses. Therefore, when the averaged measure of the voltage at the AC input is reduced by a dimmer, the duty cycle reduces, resulting in a dimmed LED. The driver can be created by adding a few components to a conventional wide input range AC-DC converter without or with very little modifications.

## Claims

### Claim 1

A circuit for adapting an AC input to drive a load comprising:
a) a measuring circuit for obtaining an averaged measure over many cycles of the voltage at the AC input;
b) a power converting module for converting the AC input into a form suitable for driving the load, wherein the power fed into the load is controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 2 (depends on 1)

The circuit of claim 1 wherein the load is an array of at least one LED.

### Claim 3 (depends on 1)

The circuit of claim 1 wherein the AC input is obtained from an AC power source through a dimmer.

### Claim 4 (depends on 3)

The circuit of claim 3 further including a bleeder for providing minimum holding current for the dimmer, wherein the bleeder can be an imperfect bleeder that can have a small amount of premature termination of the holding current and pulse to pulse variations.

### Claim 5 (depends on 1)

The circuit of claim 1 wherein the power converting module comprising an AC-DC converter and a switch for turning on and off a current path between the AC-DC converter and the load with a duty cycle controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 6 (depends on 5)

The circuit of claim 5 wherein the switch for turning on and off the current path between the AC-DC converter and the load is controlled by a pulse width modulator oscillating at a substantially fixed frequency above human's flickering perception threshold and having a pulse width controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 7 (depends on 6)

The circuit of claim 6 wherein the pulse width modulator comprising a first voltage comparator or op-amp for controlling charging and discharging of a capacitor to create, at the capacitor, a continuously running voltage waveform that ramps up and down corresponding to charging and discharging of the capacitor and a second voltage comparator or op-amp for comparing the voltage at the capacitor with a voltage representing the averaged measure obtained by the measuring circuit, wherein the output of the second voltage comparator or op-amp is used to control the switch for turning on and off the current path between the AC-DC converter and the load.

### Claim 8 (depends on 5)

The circuit of claim 5 wherein the AC-DC converter can operate stably over a wide range of the AC input to produce a substantially constant voltage output and, as the voltage at the AC input is gradually reduced, the duty cycle gradually reduces and can reach 0% before the voltage at the AC input reaches the low end of the stable operating range of the AC-DC converter.

### Claim 9 (depends on 5)

The circuit of claim 5 wherein the AC-DC converter comprising a rectifier, an isolation diode, and a DC-DC converter, wherein the input of the rectifier is connected to the AC input, the output of the rectifier is connected to the anode of the isolation diode, the cathode of the isolation diode is connected to the input of the DC-DC converter, and the measuring circuit obtains its input from the output of the rectifier before the isolation diode.

### Claim 10 (depends on 1)

The circuit of claim 1 wherein the averaged measure of the voltage at the AC input is approximately proportional to a simple average of the absolute value of the voltage at the AC input.

### Claim 11

A method for adapting an AC input to drive a load comprising:
a) obtaining an averaged measure over many cycles of the voltage at the AC input using a measuring circuit;
b) converting the AC input into a form suitable for driving the load, wherein the power fed into the load is controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 12 (depends on 11)

The method of claim 11 wherein the load is an array of at least one LED.

### Claim 13 (depends on 11)

The method of claim 11 wherein the AC input is obtained from an AC power source through a dimmer.

### Claim 14 (depends on 13)

The method of claim 13 further including using a bleeder for providing minimum holding current for the dimmer, wherein the bleeder can be an imperfect bleeder that can have a small amount of premature termination of the holding current and pulse to pulse variations.

### Claim 15 (depends on 11)

The method of claim 11 wherein converting the AC input into a continuous train of pulses for driving the load including using a power converting module comprising an AC-DC converter and a switch for turning on and off a current path between the AC-DC converter and the load with a duty cycle controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 16 (depends on 15)

The method of claim 15 wherein the switch for turning on and off the current path between the AC-DC converter and the load is controlled by a pulse width modulator oscillating at a substantially fixed frequency above human's flickering perception threshold and having a pulse width controlled by the averaged measure of the voltage at the AC input obtained by the measuring circuit.

### Claim 17 (depends on 16)

The method of claim 16 wherein the pulse width modulator comprising a first voltage comparator or op-amp for controlling charging and discharging of a capacitor to create, at the capacitor, a continuously running voltage waveform that ramps up and down corresponding to charging and discharging of the capacitor and a second voltage comparator or op-amp for comparing the voltage at the capacitor with a voltage representing the averaged measure obtained by the measuring circuit, wherein the output of the second voltage comparator or op-amp is used to control the switch for turning on and off the current path between the AC-DC converter and the load.

### Claim 18 (depends on 15)

The method of claim 15 wherein the AC-DC converter can operate stably over a wide range of the AC input to produce a substantially constant voltage output and, as the voltage at the AC input is gradually reduced, the duty cycle gradually reduces and can reach 0% before the voltage at the AC input reaches the low end of the stable operating range of the AC-DC converter.

### Claim 19 (depends on 15)

The method of claim 15 wherein the AC-DC converter comprising a rectifier, an isolation diode, and a DC-DC converter, wherein the input of the rectifier is connected to the AC input, the output of the rectifier is connected to the anode of the isolation diode, the cathode of the isolation diode is connected to the input of the DC-DC converter, and the measuring circuit obtains its input from the output of the rectifier before the isolation diode.

### Claim 20 (depends on 11)

The method of claim 11 wherein the averaged measure of the voltage at the AC input is approximately proportional to a simple average of the absolute value of the voltage at the AC input.