# US 9,049,773 B2 · Digital controller for an electronic ballast

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- Number: US 9,049,773 B2
- Document ID: US9049773B2
- Status: Granted
- Kind: B2
- Application number: 13/459,562
- Filed: 2012-04-30
- Published: 2012-12-06
- Granted: 2015-06-02
- Earliest claimed: 2011-04-28
- Assignees: Cistel Technology Inc.
- Applicants: John Lam; Praveen Jain
- Inventors: John Lam; Praveen Jain
- Web page: https://patentgrep.com/patent/US9049773B2

## CPC

- H05B 41/2824: {using control circuits for the switching element (H05B41/2822 takes precedence)}
- H05B 41/3927: {by pulse width modulation (H05B41/3922 takes precedence)}
- Y02B 20/00: Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- 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

Provided are circuits and methods for a digital controller for an electronic ballast for a fluorescent lamp, comprising a feed-forward loop that provides information about a voltage firing angle, and a pulse width modulator that controls a duty ratio of at least one power switch of the electronic ballast according to the information. The digital controller may include a duty ratio controller implemented in the pulse width modulator. The digital controller may include one or more functions such as dimming, maintaining high power factor throughout the dimming range, low lamp power detection, lamp soft-start, and DC-link capacitor over-voltage detection for end of life protection or lamp failure protection. In one embodiment the ballast is a single stage, single switch ballast.

## Claims

### Claim 1

A digital controller for an electronic ballast for a fluorescent lamp comprising:
a feed-forward loop that provides information about a voltage firing angle, wherein the feed-forward loop includes a gain circuit and an analog-to-digital converter;
a pulse width modulator that controls a duty ratio of at least one power switch of the electronic ballast according to the information,
wherein the digital controller provides low power shut-off and soft-start ignition;
wherein the digital controller is a single digital chip; and wherein the controller maintains a lamp current stability as the voltage firing angle of a line voltage increases as the lamp is dimmed.

### Claim 2 (depends on 1)

The digital controller of claim 1, including a duty ratio controller implemented in the pulse width modulator.

### Claim 3 (depends on 1)

The digital controller of claim 1, wherein the controller provides at least one of dimmability of the lamp, detection of lamp low power level, and DC-link capacitor over-voltage protection.

### Claim 4 (depends on 1)

The digital controller of claim 1, where in the controller provides soft-start lamp ignition.

### Claim 5 (depends on 1)

The digital controller of claim 1, wherein the controller provides detection of lamp low power level.

### Claim 6 (depends on 1)

The digital controller of claim 1, wherein the controller provides DC-link capacitor over-voltage protection.

### Claim 7 (depends on 1)

The digital controller of claim 1, wherein the electronic ballast is a single stage, single switch ballast.

### Claim 8 (depends on 1)

The digital controller of claim 1, wherein;
dimming of the lamp is controlled by varying phase of the firing angle; or
dimming of the lamp is controlled by varying duty cycle of a control signal.

### Claim 9 (depends on 1)

An electronic ballast for a fluorescent lamp, comprising the digital controller of claim 1.

### Claim 10 (depends on 9)

The electronic ballast of claim 9, wherein the ballast is a single stage, single switch ballast.

### Claim 11

A method of digitally controlling an electronic ballast for a fluorescent lamp, comprising:
using a feed-forward loop that provides information about a voltage firing angle, wherein the feed-forward loop includes a gain circuit and an analog-to-digital converter;
using a pulse width modulator that controls a duty ratio of at least one power switch of the electronic ballast according to the information, wherein the digital controller provides low power shut-off and soft-start ignition; and wherein the digital controller is a single digital chip; and wherein the controller maintains a lamp current stability as the voltage firing angle of a line voltage increases as the lamp is dimmed.

### Claim 12 (depends on 11)

The method of claim 11, further comprising providing at least one of dimmability of the lamp, soft-start lamp ignition, detection of lamp low power level, and DC-link capacitor over-voltage protection.

### Claim 13 (depends on 11)

The method of claim 11, further comprising providing soft-start lamp ignition.

### Claim 14 (depends on 11)

The method of claim 11, further comprising providing detection of lamp low power level.

### Claim 15 (depends on 11)

The method of claim 11, further comprising providing DC-link capacitor over-voltage protection.

### Claim 16 (depends on 11)

The method of claim 11, wherein the ballast is a single stage, single switch ballast.