# US 9,883,560 B2 · Controller for a phase cut dimmable LED driver

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- Number: US 9,883,560 B2
- Document ID: US9883560B2
- Status: Granted
- Kind: B2
- Application number: 14/865,069
- Filed: 2015-09-25
- Published: 2017-03-30
- Granted: 2018-01-30
- Earliest claimed: 2015-09-25
- Assignees: Osram Sylvania Inc.
- Applicants: Richard Garner
- Inventors: Richard Garner
- Web page: https://patentgrep.com/patent/US9883560B2

## CPC

- H05B 45/10: Controlling the intensity of the light
- H05B 39/04: Controlling
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

A control scheme for a dimmable lighting driver is provided. The control scheme may operate with a phase cut type dimmer (leading or trailing edge). In an embodiment, the control scheme is programmed or otherwise configured into a controller as a control algorithm. The control algorithm is configured to measure phase cut and zero crossing angles of the input mains waveform, and to subsequently maintain constant LED current commensurate with a user-set dimming level, with no flicker. The control algorithm may be implemented in software, such as a firmware-based routine executable by one or more controllers of a given driver. The one or more controllers may be, for example, an existing general purpose controller of the given driver, or a dedicated dimming controller. Numerous configurations will be apparent in light of this disclosure.

## Claims

### Claim 1

A method for control of a phase cut dimmer for lighting systems, the method comprising:
receiving, at a controller of a lighting driver circuit, a representation of an input voltage waveform having a phase cut angle (φcut) and a waveform zero angle (φzero), as well as a known frequency;
acquiring, by the controller, data representative of a period of the waveform;
determining, by the controller, a plurality of Fourier series coefficients associated with the waveform;
extracting, by the controller, the phase cut angle (φcut) and the waveform zero angle (φzero) based on the coefficients;
determining, by the controller, a current for one or more light emitting diodes (LEDs) based on at least one of the phase cut angle (φcut) and the waveform zero angle (φzero); and
adjusting, by the controller, a duty cycle of a pulse width modulation (PWM) signal to provide the determined current to the one or more LEDs.

### Claim 2 (depends on 1)

The method of claim 1 wherein determining a plurality of Fourier series coefficients associated with the period comprises determining the two lowest order Fourier series coefficients (0th and 1st) associated with the waveform.

### Claim 3 (depends on 1)

The method of claim 1, further comprising:
storing the data representative of the waveform period.

### Claim 4 (depends on 1)

The method of claim 1 wherein acquiring data representative of a period of the waveform comprise acquiring data representative of one period of the waveform.

### Claim 5 (depends on 1)

The method of claim 1 wherein extracting the phase cut angle (φcut) and the waveform zero angle (φzero) based on the coefficients comprises extracting the phase cut angle (φcut) and the waveform zero angle (φzero) through inversion of an analytical representation of the coefficients, the inversion comprising:
determining the values of cos(φcut) and sin(φcut); and
determining the value of the waveform zero angle φzero based on cos(φcut) and sin(φcut).

### Claim 6 (depends on 5)

The method of claim 5 wherein determining the values of cos(φcut) and sin(φcut) is carried out using the follow equations:
cos
⁡
(
ϕ
cut
)
=
±
(
π
⁢
⁢
a
oM
2
⁢
A
-
1
)
;
and
sin
⁡
(
ϕ
cut
)
=
1
-
cos
2
⁡
(
ϕ
cut
)
,
where A is amplitude of the input waveform, π is the period of the waveform, and
a
0
⁢
M
=
2
N
⁢
∑
k
=
1
N
⁢
d
k
,
where N is a number of data points include in the data representative of the period, dk is the kth data point of the N data points, M indicates a0 is a measured valued, and the upper + sign of the ± symbol corresponds to leading edge phase cut waveforms and lower − sign of the ± symbol corresponds to trailing edge phase cut waveforms.

### Claim 7 (depends on 6)

The method of claim 6 wherein A is assumed based on a nominal RMS (root mean square) level of the waveform together with a division factor based on resistance values of resistors used in a voltage divider to generate the representation of an input voltage waveform.

### Claim 8 (depends on 1)

The method of claim 1 wherein determining the value of cos(φcut) is carried out using interpolation, and determining the value of sin(φcut) is carried out using the follow equation sin(φcut)=√{square root over (1−cos2(φcut))}.

### Claim 9 (depends on 8)

The method of claim 8 wherein the interpolation is carried out by accessing a pre-computed look-up table (LUT).

### Claim 10

A non-transitory computer program product encoding instructions that when executed by one or more processors cause a dimming control process for a light system to be carried out, the process comprising:
receiving, at a controller of a lighting driver circuit, a representation of an input voltage waveform having a phase cut angle (φcut) and a waveform zero angle (φzero), as well as a known frequency;
acquiring, by the controller, data representative of a period of the waveform;
determining, by the controller, a plurality of Fourier series coefficients associated with the waveform;
extracting, by the controller, the phase cut angle (φcut) and the waveform zero angle (φzero) based on the coefficients;
determining, by the controller, a current for one or more light emitting diodes (LEDs) based on at least one of the phase cut angle (φcut) and the waveform zero angle (φzero); and
adjusting, by the controller, a duty cycle of a pulse width modulation (PWM) signal to provide the determined current to the one or more LEDs.

### Claim 11 (depends on 10)

The computer program product of claim 10 wherein determining a plurality of Fourier series coefficients associated with the period comprises determining the two lowest order Fourier series coefficients (0th and 1st) associated with waveform.

### Claim 12 (depends on 10)

The computer program product of claim 10, further comprising:
storing the data representative of the waveform period.

### Claim 13 (depends on 10)

The computer program product of claim 10 wherein acquiring data representative of a period of the waveform comprises acquiring data representative of one period of the waveform.

### Claim 14 (depends on 10)

The computer program product of claim 10 wherein extracting the phase cut angle (φcut) and the waveform zero angle (φzero) based on the coefficients comprises extracting the phase cut angle (φcut) and the waveform zero angle (φzero) through inversion of an analytical representation of the coefficients, the inversion comprising:
determining the values of cos(φcut) and sin(φcut); and
determining the value of the waveform zero angle φzero based on cos(φcut) and sin(φcut).

### Claim 15 (depends on 10)

The computer program product of claim 10 wherein determining the values of cos(φcut) and sin(φcut) is carried out using the follow equations:
cos
⁡
(
ϕ
cut
)
=
±
(
π
⁢
⁢
a
oM
2
⁢
A
-
1
)
;
and
sin
⁡
(
ϕ
cut
)
=
1
-
cos
2
⁡
(
ϕ
cut
)
,
where A is amplitude of the input waveform, π is the period of the waveform, and
a
0
⁢
M
=
2
N
⁢
∑
k
=
1
N
⁢
d
k
,
where N is a number of data points include in the data representative of the period, dk is the kth data point of the N data points, M indicates a0 is a measured valued, and the upper + sign of the ± symbol corresponds to leading edge phase cut waveforms and lower − sign of the ± symbol corresponds to trailing edge phase cut waveforms.

### Claim 16 (depends on 15)

The computer program product of claim 15 wherein A is assumed based on a nominal RMS (root mean square) level of the waveform together with a division factor based on resistance values of resistors used in a voltage divider to generate the representation of an input voltage waveform.

### Claim 17 (depends on 10)

The computer program product of claim 10 wherein determining the value of cos(φcut) is carried out using interpolation, and determining the value of sin(φcut) is carried out using the follow equation sin(φcut)=√{square root over (1−cos2(φcut))}.

### Claim 18 (depends on 17)

The computer program product of claim 17 wherein the interpolation is carried out by accessing a pre-computed look-up table (LUT).

### Claim 19

A lighting driver controller, comprising:
a processor;
a memory accessible to the processor and encoding a plurality of instructions that when executed by the processor cause a dimming control process to be carried out, the process comprising:
receiving a representation of an input voltage waveform having a phase cut angle (φcut) and a waveform zero angle (φzero), as well as a known frequency;
acquiring data representative of a period of the waveform;
determining a plurality of Fourier series coefficients associated with the waveform;
extracting the phase cut angle (φcut) and the waveform zero angle (φzero) based on the coefficients;
determining a current for one or more light emitting diodes (LEDs) based on at least one of the phase cut angle (φcut) and the waveform zero angle (φzero); and
adjusting a duty cycle of a pulse width modulation (PWM) signal to provide the determined current to the one or more LEDs.

### Claim 20 (depends on 19)

The controller of claim 19 wherein determining a plurality of Fourier series coefficients associated with the period comprises determining the two lowest order Fourier series coefficients (0th and 1st) associated with the waveform.

### Claim 21 (depends on 19)

The controller of claim 19, further comprising:
storing the data representative of the waveform period.

### Claim 22 (depends on 19)

The controller of claim 19 wherein acquiring data representative of a period of the waveform comprise acquiring data representative of one period of the waveform.

### Claim 23 (depends on 19)

The controller of claim 19 wherein extracting the phase cut angle (φcut) and the waveform zero angle (φzero)based on the coefficients comprises extracting the phase cut angle (φcut) and the waveform zero angle (φzero) through inversion of an analytical representation of the coefficients, the inversion comprising:
determining the values of cos(φcut) and sin(φcut); and
determining the value of the waveform zero angle φzero based on cos(φcut) and sin(φcut).

### Claim 24 (depends on 19)

The controller of claim 19 wherein determining the values of cos(φcut) and sin(φcut) is carried out using the follow equations:
cos
⁡
(
ϕ
cut
)
=
±
(
π
⁢
⁢
a
oM
2
⁢
A
-
1
)
;
and
sin
⁡
(
ϕ
cut
)
=
1
-
cos
2
⁡
(
ϕ
cut
)
,
where A is amplitude of the input waveform, π is the period of the waveform, and
a
0
⁢
M
=
2
N
⁢
∑
k
=
1
N
⁢
d
k
,
where N is a number of data points include in the data representative of the period, dk is the kth data point of the N data points, M indicates a0 is a measured valued, and the upper + sign of the ± symbol corresponds to leading edge phase cut waveforms and lower − sign of the ± symbol corresponds to trailing edge phase cut waveforms.

### Claim 25 (depends on 24)

The controller of claim 24 wherein A is assumed based on a nominal RMS (root mean square) level of the waveform together with a division factor based on resistance values of resistors used in a voltage divider to generate the representation of an input voltage waveform.

### Claim 26 (depends on 19)

The controller of claim 19 wherein determining the value of cos(φcut) is carried out using interpolation, and determining the value of sin(φcut) is carried out using the follow equation sin(φcut)=√{square root over (1−cos2(φcut))}.

### Claim 27 (depends on 26)

The controller of claim 26 wherein the interpolation is carried out by accessing a pre-computed look-up table (LUT).