# US 5,705,896 A · Control electronic ballast system using feedback

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- Number: US 5,705,896 A
- Document ID: US5705896A
- Status: Granted
- Kind: A
- Application number: 08/619,237
- Filed: 1996-03-21
- Granted: 1998-01-06
- Earliest claimed: 1995-03-30
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Nak Choon Choi
- Web page: https://patentgrep.com/patent/US5705896A

## CPC

- H05B 41/295: with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
- H05B 41/382: {during the transitional start-up phase}
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

A feedback control system for electronic ballast comprises a lamp, an electronic ballast, a multiplier, a time controller, a first adder-subtracter, a reference voltage generator, a second adder-subtracter, an error amplifier, a capacitor, a voltage controlled current source VCCS, a third adder-subtracter and an oscilloscope and output driver.

## Claims

### Claim 1

An illumination device including an electronic ballast and a feedback control system, comprising:
a lamp;
an electronic ballast for controlling lamp preheating, temporary lamp discharge, and lamp discharge maintenance, and for producing first and second signals for controlling feedback;
a multiplier for receiving and multiplying said first and second signals from said electronic ballast, thereby producing an output signal;
a time controller for producing a signal proportional to a lamp preheating time period and a lamp discharge time period;
a soft start controller for receiving said signal from said time controller and producing an output signal controlling a lamp preheating period and a lamp discharge period, said soft start controller including:
a second transistor having a base terminal for receiving said signal from said time controller;
a first resistor having a first terminal connected to an emitter terminal of said second transistor;
a third transistor having a collector terminal connected to a second terminal of said first resistor, a base terminal arranged to receive an ip bias current, and an emitter terminal for producing a first current;
a fourth transistor having an emitter terminal connected to said second terminal of said first resistor and said collector terminal of said third transistor, and a collector terminal connected to said first adder-subtracter;
a second resistor having a first terminal connected to said collector terminal of said third transistor and to said emitter terminal of said fourth transistor;
a fifth transistor having an emitter terminal connected to a second terminal of the second resistor, a base terminal connected to a base terminal of the fourth transistor, and a collector terminal connected to said base terminal of said fifth transistor;
a fourth resistor having a first terminal connected to said emitter terminal of said third transistor, and a second terminal connected to said collector terminal of said fifth transistor;
a third resistor having a first terminal connected to said second terminal of said fourth resistor and said collector terminal of said fifth transistor; and
a first transistor with an emitter terminal connected to a second terminal of said third resistor, a collector terminal, and a base terminal connected to said collector terminal of said first transistor, said collector terminal of said first transistor being arranged to pass a current to said collector terminal of said second transistor;
a first adder-subtracter for adding or subtracting said output signal from said multiplier and said output signal from said soft start controller;
a reference voltage generator for producing a reference voltage for determining an input voltage to said electronic ballast;
a second adder-subtracter for adding or subtracting an output signal produced by said first adder-subtracter passed through a resistor, and said reference voltage from said reference voltage generator;
an error amplifier for amplifying an output signal produced by said second adder-subtracter;
a capacitor for integrating an output current signal produced by said error amplifier so as to convert it into a voltage;
a voltage controlled current source (VCCS) for receiving said voltage from said capacitor and converting it into a current;
a third adder-subtracter for adding or subtracting said current from said VCCS, a reference current, and a signal produced by said electronic ballast passed through a resistor, thereby obtaining a resultant output current; and
an oscillator and output driver including an internal capacitor which is arranged so as to be charged by an output current from said third adder-subtracter, thereby determining a control frequency supplied to said electronic ballast.

### Claim 2 (depends on 1)

The device of claim 1, wherein said second transistor is constructed and arranged to be turned ON at a time at which lamp preheating ends and lamp discharge begins when said signal from said time controller increases relative to time and approaches a voltage at said base terminals of said fourth and fifth transistors.

### Claim 3 (depends on 1)

The device of claim 1, wherein said output signal from said soft start controller becomes zero at a time at which lamp discharge ends and lamp discharge maintenance begins when a collector current of said first transistor is equal to an emitter current of said third transistor.

### Claim 4 (depends on 1)

The device of claim 1, wherein a collector current of said first transistor increases and a collector current from said fourth transistor decreases between a beginning and an end of lamp discharge.

### Claim 5 (depends on 1)

The device of claim 1, wherein a rate of change of a current is controlled according to said first resistor between a beginning of lamp discharge and an end of lamp discharge, wherein a resistive value of said first resistor is inversely proportional to said rate of change of said current.