Electronically controlled magnetic fluorescent lamp ballast

• US 5,027,032 A
• Filed: 02/20/1990
• Issued: 06/25/1991
• Est. Priority Date: 10/18/1985
• Status: Expired due to Fees

• Current Assignee: Ole K Nilssen
• Original Assignee: Ole K Nilssen
• Inventors: Nilssen, Ole K.
• Primary Examiner(s): Mis, David
• Application Number:
  US07/488,366
• Time in Patent Office: 490 Days
• Field of Search: 315/70, 315/103, 315/105, 315/106, 315/200 R, 315/DIG. 7
• US Class Current: 315/103
• CPC Class Codes: H05B 41/046 using controlled semiconductor devices
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

A magnetic-type ballast powers two series-connected fluorescent lamps from a 277 Volt power line. Except when the lamps are loading the ballast, an electronic control circuit provides an intermittently interrupted short circuit across the two lamps: providing for socket voltages high enough to permit lamp ignition for a period of about 25 milli-seconds every two seconds or so, but keeping the average socket voltages low enough to satisfy safety requirements.

When initially connecting power to the lamp-ballast combination, the control circuit enters its short circuit state and remains there for two seconds. Then, after two seconds, the control circuit switches into an open circuit, thereby permitting the voltage across the lamps to become high enough to cause lamp starting within a few milli-seconds. If the lamps fail to start, the electronic circuit reverts back to a short circuit within 25 milli-seconds.

Normally the lamps do start, thereby causing a reduction in the voltage across the lamps compared with pre-starting. Due to this voltage reduction, the electronic circuit changes its mode into a continuous open circuit state.

The electronic control circuit comprises a bridge rectifier and a push-pull inverter that can be triggered into and out of self-oscillation. When the inverter oscillates, it acts as an short circuit, while also providing heating power for all lamp cathodes. When not oscillating, it acts as an open circuit.

Claims

1. An arrangement characterized by comprising:

a) impedance means connected with a source of electric power and operative to provide a current-limited supply voltage across a pair of ballast terminals;

b) gas discharge lamp means having a pair of lamp terminals and being connected with the ballast terminals by way of these lamp terminals;

the gas discharge lamp means including at least two individual gas discharge lamps;

the lamp means being operative to exist in either of two states;

i) a pre-ignition state during which no substantial amount of current flows through the lamp means; and

ii) a post-ignition state during which a substantial amount of current does flow through the lamp means;

the lamp means having at least one thermionic cathode with a pair of cathode terminals which are electrically isolated from the ballast terminals during the pre-ignition state; and

c) control means connected with the ballast terminals and operative to exist in either of two modes;

i) a first mode existing throughout the pre-ignition state and during which the control means alternates between relatively brief periods of effectively constituting an open circuit and relatively long periods of effectively constituting a short circuit, while also during these relatively long periods providing cathode heating power to the thermionic cathode by way of the cathode terminals; and

ii) a second mode existing throughout the post-ignition period and during which the control means effectively constitutes a continuous open circuit;

and by being operative to;

1. cause the thermionic cathode to become hot and thereby operative to permit effective ignition of the lamp means; and

2. cause the lamp means to ignite during one of the relatively brief periods and thereby to enter the second state.

2. The arrangement of claim 1 and means operative to cause the cathode heating power to be absent throughout the second state.

3. The arrangement of claim 1 wherein the cathode heating power is provided in the form of a voltage of frequency substantially higher than that of the supply voltage.

4. The arrangement of claim 1 wherein the duration of each of the relatively long periods is at least ten times longer than the duration of each of the relatively brief periods.

5. An arrangement characterized by comprising:

a) impedance means connected with a source of electric power and operative to provide a current-limited AC supply voltage across a pair of ballast terminals;

the AC supply voltage being characterized by having a cycle period;

b) gas discharge lamp means having a pair of lamp terminals and being connected with the ballast terminals by way of these lamp terminals;

the lamp means being operative to exist in either of two states;

i) a pre-ignition state during which no substantial amount of current flows through the lamp means; and

ii) a post-ignition state during which a substantial amount of current does flow through the lamp means;

the lamp means having a thermionic cathode with a pair of cathode terminals; and

c) control means connected with the ballast terminals and operative to exist in either of two modes;

i) a first mode existing throughout the pre-ignition state and during which the control means alternates between relatively brief periods of effectively constituting an open circuit and relatively long periods of effectively constituting a short circuit, while also during these relatively long periods providing cathode heating power to the thermionic cathode by way of the cathode terminals, each relatively brief period having a duration substantially longer than half the duration of said cycle period; and

ii) a second mode existing throughout the post-ignition period and during which the control means effectively constitutes a continuous open circuit;

and by being operative to;

1. provide cathode heating power for the cathode, thereby to cause the cathode to become hot and thereby operative to permit effective ignition of the lamp means; and

2. cause the lamp means to ignite during one of the relatively brief periods and thereby to enter the second state, the ignition taking place regardless of the particular moment in time at which this one relatively brief period starts.

6. The arrangement of claim 5 wherein the cathode heating power is caused to be absent throughout the second state.

7. The arrangement of claim 5 wherein the cathode is electrically isolated from the ballast terminals during the pre-ignition state.

8. The arrangement of claim 5 wherein the RMS magnitude of the voltage provided across the ballast terminals, as averaged over a period of at least one second, is lower before the lamp means ignites as compared with after is has ignited.

9. The arrangement of claim 5 wherein the cathode heating power is provided in the form of a voltage of frequency substantially higher than that of the supply voltage.

10. An arrangement characterized by comprising:

a) impedance means connected with a source of AC voltage and operative to provide a current-limited AC supply voltage across a pair of ballast terminals;

b) gas discharge lamp means having a pair of lamp terminals and being connected with the ballast terminals by way of these lamp terminals;

the lamp means being operative to exist in either of two states;

i) a pre-ignition state during which no substantial amount of current flows through the lamp means; and

ii) a post-ignition state during which a substantial amount of current does flow through the lamp means; and

c) control means connected with the ballast terminals and operative to exist in either of two modes;

i) a first mode existing throughout the pre-ignition state and during which the control means alternates between relatively brief periods of effectively constituting an open circuit and relatively long periods of effectively constituting a short circuit, while also during these relatively long periods providing cathode heating power to the thermionic cathode by way of the cathode terminals, this cathode heating power being provided in the form of a cathode voltage of frequency substantially higher than that of the AC supply voltage, the cathode heating power being provided by way of a frequency conversion means included as part of the control means; and

ii) a second mode existing throughout the post-ignition period and during which the control means effectively constitutes a continuous open circuit;

and by being operative to;

1. cause the thermionic cathode to become hot and thereby operative to permit effective ignition of the lamp means; and

2. cause the lamp means to ignite during one of the relatively brief periods and thereby to enter the second state.

11. The arrangement of claim 10 and means operative to cause the cathode heating power to be absent throughout the second state.

12. The arrangement of claim 10 wherein the duration of each of the relatively long periods is at least ten times longer than the duration of each of the relatively brief periods.

13. An arrangement characterized by comprising:

a) impedance means connected with a source of AC voltage and operative to provide a current-limited AC supply voltage across a pair of ballast terminals;

b) gas discharge lamp means having a pair of lamp terminals and being disconnectably connected with the ballast terminals by way of these lamp terminals;

the lamp means being operative to exist in either of two states;

i) a pre-ignition state during which no substantial amount of current flows through the lamp means; and

ii) a post-ignition state during which a substantial amount of current does flow through the lamp means; and

c) control means connected with the ballast terminals and operative to exist in either of two modes;

i) a first mode existing throughout the pre-ignition state as well as throughout any period when the lamp means may be non-connected with the ballast terminals, during which first mode the control means alternates between relatively brief periods of effectively constituting an open circuit and relatively long periods of effectively constituting a short circuit, and ii) a second mode existing only when the lamp means is connected and then only during the post-ignition period, during which the second mode the control means effectively constitutes a continuous open circuit.

14. The arrangement of claim 13 wherein:

i) the RMS magnitude of the voltage provided across the ballast terminals, absent the control means, is so large as to constitute a serious electric shock hazard to a person involved in connecting the lamp means with the ballast terminals, and

ii) wherein the control means is operative, during any period when the lamp means may not be fully connected, to prevent the RMS magnitude of the voltage actually present across the ballast terminals from becoming so large as to represent a serious electric shock hazard to a person involved in connecting the lamp means with the ballast terminals.

15. The arrangement of claim 13 wherein:

i) the lamp means has thermionic cathode means, and

ii) the control means is operative to provide cathode heating power to the thermionic cathode means.

16. The arrangement of claim 15 wherein the cathode heating power is provided in the form of a voltage of frequency substantially higher than that of the supply voltage.

17. An arrangement for powering a gas discharge lamp means having a pair of lamp terminals, comprising:

a) impedance means connected with a source of AC voltage and operative to provide a manifestly current-limited AC supply voltage across a pair of ballast terminals, these ballast terminals being adapted for connection with the lamp terminals, the AC supply voltage having an open circuit magnitude that is so large as to represent a serious electric shock hazard to a person involved with connecting or disconnecting the lamp terminals with/from the ballast terminals; and

b) control means connected in circuit with the impedance means and, whenever a lamp means is not connected with the ballast terminals, operative;

i) to cause the magnitude of the voltage present across the ballast terminals to cyclically alternate between a relatively brief period of relatively high magnitude and a relatively long period of relatively low magnitude, and in such manner as to cause the relatively high magnitude to exist for no more than about 25 mill-seconds before being reduced to the relatively low magnitude;

and functioning such that the voltage provided across the ballast terminals is prevented from representing a serious electric shock hazard to a person attempting to connect or disconnect the lamp means with/from the ballast terminals.

18. Control means for a gas discharge lamp ballast having a pair of ballast terminals, comprising:

input terminals operative to connect with the ballast terminals;

shorting means connected in circuit with the input terminals and conditionally operative;

i) to cause an effective short circuit to occur between the input terminals, this short circuit occurring only after the magnitude of any voltage present between the input terminals has exceeded a pre-determined level for a first brief period of time; and

ii) to cause the short circuit to disappear after a second brief period of time, this second brief period of time being at least ten times longer than the first brief period of time;

such that the control means is operative to provide said effective short circuit across the input terminals whether or not a gas discharge lamp is connected across the ballast terminals.

19. The control means of claim 18 wherein the first brief period of time is shorter than about 25 milli-seconds.

20. The control means of claim 18 wherein the shorting means comprises bridge rectifier means and an inverter means operable to be triggered into and out of self-oscillation.

21. The arrangement of claim 18 wherein the shorting means is operative to provide a cathode heating voltage across a pair of auxiliary terminals, but only as long as the shorting means is actually operative to cause a short circuit between the input terminals.

22. A ballast means adapted:

i) to be powered from the power line voltage of an ordinary electric utility power line, and ii) to operate a fluorescent lamp means, comprising;

inductor means connected with the power line and operative to provide a current-limited AC voltage at a pair of ballast terminals, the magnitude of this current-limited AC voltage being large enough to permit rapid-start ignition of the fluorescent lamp means, the frequency of this current-limited AC voltage being the same as that of the power line voltage;

connect means operable to connect a fluorescent lamp means across the ballast terminals, the fluorescent lamp means having a thermionic cathode;

control means connected with the ballast terminals, the control means being operative to exist in either of two states;

i) a first state wherein it constitutes a relatively low-magnitude impedance and wherein it provides electric heating power to the thermionic cathode, and ii) a second state where it represents a relatively high-magnitude impedance and wherein it does not provide electric heating power to the thermionic cathode; and

starting aid electrode being;

i) electrically connected with the power line, ii) positioned adjacent the lamp means, and iii) operative to constitute a starting aid for the lamp means;

thereby to cause the lamp means to ignite in a rapid-start manner during a period when the control means exists in its second state, but only after having been preceded by a period during which the control means existed in its first state.