US 5,023,518 A · Ballast circuit for gaseous discharge lamp

Abstract

A ballast circuit for a gaseous discharge lamp, particularly a neon light, includes a diode bridge rectifier for producing a d-c voltage from an a-c input and a transformer with a secondary winding connected to the lamp and a primary winding connected to the rectifier. A switching circuit is connected to the transformer primary winding for controlling a flow of current therethrough from the rectifier. The switching circuit includes at least one MOSFET having a drain terminal connected to the transformer primary winding and a grounded source terminal. A control circuit is connected to a gate terminal of the MOSFET for controlling the on and off times thereof, the control circuit including a pulse generator for producing a train of pulse-width-modulated rectangular pulses of substantially a single frequency fed to the MOSFET's gate terminal. The pulse generator includes circuitry for changing the width of the rectangular pulses to enable a gradual energization of the gaseous discharge lamp from one end thereof towards an opposite end to create a writing effect of selectively different speeds in the gaseous discharge lamp. The circuitry in the pulse generator for changing the pulse width can be used to control the widths of the pulses so that the pulses are a train of square waves having a common duration equal to an interpulse period, whereby striations are generated in the gaseous discharge lamp.

Claims22

Dependent claims

An electronic ballast circuit for energizing a gaseous discharge lamp, comprising in combination:

power source means for producing a d-c voltage;
power supply means including a transformer operatively connected to said power source means and operatively connectable to the gaseous discharge lamp for transferring electrical power thereto from said power source means;
switching means connected to said power supply means for controlling a flow of current from said power source means through said power supply means, said switching means including at least one MOSFET having a drain terminal connected to said power supply means and a grounded source terminal;
control means connected to a gate terminal of said MOSFET for controlling the on and off times of said switching means, said control means including pulse generation means for generating a train of pulse-width-modulated rectangular pulses of substantially a single frequency fed to said gate terminal;
and
discharge means operatively connected to said supply means for discharging said transformer during an off period of said MOSFET, said discharge means including a resistor and a capacitor connected in parallel across a primary winding of said transformer.

3 more elements

An electronic ballast circuit for energizing, a gaseous discharge lamp, comprising in combination:

power source means for producing a d-c voltage;
a step-up transformer having a primary winding connected at one end to said power source means, said step-up transformer having a secondary winding connectable to the gaseous discharge lamp;
switching means connected to said primary winding for controlling the flow of current from said power source means through said primary winding, said switching means including at least one MOSFET having a drain terminal connected to said primary winding and a grounded source terminal;
and
control means connected to a gate terminal of said MOSFET for controlling the on and off times of said switching means, said control means including pulse generation means for generating a train of pulse-width-modulated rectangular pulses of substantially a single frequency fed to said gate terminal, said pulse generation means in turn including means for changing the width of said pulses to enable a gradual energization of said lamp from one end thereof at a variable rate towards an opposite end to create a writing effect of different speeds in said lamp.

2 more elements

An electronic ballast circuit for controlling the energization of a gaseous discharge lamp, comprising in combination:

power source means for producing a d-c voltage;
power supply means operatively connected to said power source means and operatively connectable to the gaseous discharge lamp for transferring thereto from said power source means electrical power of a single polarity;
switching means connected to said power supply means for controlling the flow of current from said power source means through said power supply means;
and
control means connected to said switching means for controlling the on and off times of said switching means, said control means including:
feedback means for generating a feedback voltage proportional to a voltage drop in said power supply means;
first reference means for generating a control voltage, said first reference means including oscillator means for generating a rectangular waveform having a pre-established amplitude and periodicity, said first reference means further including means for producing said control voltage from said rectangular waveform;
and
pulse-width-modulation means operatively connected to said feedback means and said reference means for producing a pulse-width-modulated train of rectangular pulses of essentially a single frequency in response to a difference between said feedback voltage and said control voltage, said pulse-width-modulation means having an output operatively connected to said switching means for controlling the on and off times of said switching means.

6 more elements

Dependencies are inferred from the claim text.

Ballast circuit for gaseous discharge lamp

Life of this patent

Ballast circuit for gaseous discharge lamp

Life of this patent

Abstract

Claims22