Reactor-type ballast circuit

• US 4,914,354 A
• Filed: 09/08/1988
• Issued: 04/03/1990
• Est. Priority Date: 09/08/1988
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Lemmers, Eugene, Hammer, Edward E.
• Primary Examiner(s): MIS, DAVID C
• Application Number:
  US07/241,991
• Time in Patent Office: 572 Days
• Field of Search: 315/94, 315/95, 315/97, 315/102, 315/103, 315/104, 315/105, 315/106, 315/107, 315/243, 315/245, 315/247, 315/290, 315/DIG. 5
• US Class Current: 315/247
• CPC Class Codes: H05B 41/08 heated by glow discharge
• CPC Class Codes: Y10S 315/05 Starting and operating circuit for fluorescent lamp

Abstract

An improved, more energy efficient reactor-type ballasting circuit for fluorescent lamps includes an inductive ballasting coil for directly applying an AC line voltage to the cathodes of a lamp without an intermediate autotransformer and also includes a glow type thermal switch in series with a positive temperature coefficient (PTC) resistor for electrical connection across the cathodes of the lamp to conduct pre-heating current to the lamp cathodes. The PTC resistor will effectively remove the glow switch from the ballast circuit if the switch fails to open after an appropriate time delay.

Claims

1. An improved reactor type ballast circuit for a plurality of fluorescent lamps, each having a cathode disposed at each end thereof and shaped so that the ends are proximate to each other, said ballast circuit comprising:

a first input terminal and a second input terminal said second terminal serving for electrical connection with one cathode of each lamp;

a plurality of inductive ballasting coils, each having one end electrically connected to said first input terminal and another end for electrical connection respectively to the other cathodes of the lamps;

separate switch means for electrical connection between the lamp cathodes of each lamp, each said switch means operating to close when line voltage is applied across said first and second input terminals to conduct pre-heating current to said cathodes of each lamp before the lamps are started and to open after a time delay;

whereby, said ballasting coils respectively induce a high voltage pulse across the cathodes of each lamp to start each lamp in response to said switch means openings;

means for effectively removing each said switch means from said ballast circuit in the event said switch means fails to open upon expiration of said time delay and

a power factor correction capacitor connected in series with one of said ballasting coils;

said series connection of said power factor correction capacitor with said one of ballasting coils forming a lead circuit whereas, said other ballasting coil being devoid of any connection to said power factor correction capacitor forming a lag circuit;

said lead and lag circuit counteracting each other for more efficient consumption of power of said line voltage during the steady state operation of said plurality of fluorescent lamps.

2. A ballast circuit according to claim 1, wherein each said switch means includes a glow type thermal switch.

3. A ballast circuit according to claim 1, wherein said switch removing means includes a separate positive temperature coefficient resistor connected in series with each said switch means.

4. A ballast circuit according to claim 1, which further includes means for shunting pre-heating current from said capacitor to prevent limitation of said pre-heating current by said capacitor.

5. A ballast circuit according to claim 4, wherein said capacitor shunting means includes a positive temperature coefficient resistor.

6. A ballast circuit according to claim 5, wherein said switch means includes a plurality of glow type thermal switches, one electrically connected between the cathodes of each lamp.

7. A ballast circuit according to claim 6 wherein said switch removing means includes a plurality of positive temperature coefficient resistors, one connected in series with each glow switch.

8. An improved reactor type ballast circuit for a pair of fluorescent lamps, each having a cathode disposed at each end thereof, said ballast circuit comprising:

a first input terminal and a second input terminal, said second terminal serving for electrical connection with one cathode of each lamp;

a first inductive ballasting coil having one end electrically connected to said first input terminal and another end for electrical connection to the other cathode of one lamp of the pair of lamps;

a first glow type thermal switch for electrical connection between the cathodes of the one lamp;

a second inductive ballasting coil having one end electrically connected to said first input terminal and another end for electrical connection to the other cathode of the other lamp;

a second glow type thermal switch for electrical connection between the cathodes of the other lamp, said first and second glow switches operating to close when line voltage is applied across said first and second input terminals to conduct pre-heating current respectively to the cathodes of the pair of lamps and to open after a time delay;

whereby, said first and second ballasting coils respectively induce a high voltage pulse across the cathodes of the pair of lamps to start the lamps in response to the opening of said first and second glow switches;

first and second positive temperature coefficient resistors respectively connected in series with said first and second glow switches, said first and second positive temperature coefficient resistors respectively operating to increase in resistance to effectively remove either of said glow switches from said ballast circuit in the event either of said glow switches fails to open upon expiration of said time delay;

a capacitor connected in series with one of said first and second inductive ballasting coils;

a third positive temperature coefficient resistor shunting said capacitor to shunt pre-heating current from said capacitor to prevent limitation of said pre-heating current by said capacitor,

said series connection of said power factor correction capacitor with one of said first and second ballasting coils forming a lead circuit, whereas, said other ballasting coil being devoid of any connection to said power factor correction capacitor forming a lag circuit;

said lead and lag circuit counteracting each other for more efficient consumption of power of said line voltage during the steady state operation of said pair of fluorescent lamps.