Electronic ballast with frequency control

• US 5,757,140 A
• Filed: 03/16/1992
• Issued: 05/26/1998
• Est. Priority Date: 03/20/1978
• Status: Expired due to Term

• Current Assignee: CFL Technologies LLC
• Original Assignee: Ole K Nilssen
• Inventors: Nilssen, Ole K.
• Primary Examiner(s): Neyzari, Ali
• Application Number:
  US07/851,887
• Time in Patent Office: 2,262 Days
• Field of Search: 315/209 R, 315/219, 315/DIG. 4, 315/DIG. 5, 315/DIG. 7, 315/220, 315/224, 315/240, 315/53, 315/276, 315/278, 315/279, 315/307, 331/113 A
• US Class Current: 315/209.00R
• CPC Class Codes: H02M 7/53832 in a push-pull arrangement
• CPC Class Codes: H02M 7/53835 of the parallel type
• CPC Class Codes: H02M 7/53846 Control circuits
• CPC Class Codes: H02M 7/53862 using transistor type converters
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H03K 3/30 using a transformer for feedback, e.g. blocking oscillator
• CPC Class Codes: H05B 41/245 for a plurality of lamps
• CPC Class Codes: H05B 41/28 using static converters
• CPC Class Codes: H05B 41/2827 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 41/2856 against internal abnormal circuit conditions
• CPC Class Codes: H05B 41/295 with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
• CPC Class Codes: H05B 41/38 Controlling the intensity of light
• CPC Class Codes: H05B 41/3925 by frequency variation H05B41/3922 takes precedence
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

A half-bridge inverter is powered from a constant DC voltage and loaded by way of an L-C circuit that has a natural resonance frequency equal to or lower than the inverter'"'"'s operating frequency. A gas discharge lamp is disconnectably connected across the tank capacitor of the L-C circuit and, when indeed so connected, is provided with a current-limited high-frequency (30 kHz) voltage. The magnitude of the resulting lamp current decreases as the inverter'"'"'s operating frequency is increased; which operating frequency is controlled by way of a negative feedback arrangement that causes the frequency to increase as a function of increasing magnitude of the current flowing through the tank capacitor. Thus, particularly with the lamp disconnected, the magnitude of the current flowing through the capacitor--and therefore also the magnitude of the voltage existing across it--will be regulated so as to be lower than it would be in the absence of the negative feedback.

Claims

1. An arrangement comprising:

a pair of power line terminals at which is provided a power line voltage;

rectification and filtering circuitry connected with the power line terminals and operative to provide a DC supply voltage at a set of DC terminals;

the absolute magnitude of the DC supply voltage being substantially constant; and

inverter and load circuitry connected with the DC terminals and operative to provide an AC voltage at a pair of AC terminals with which is connected a gas discharge lamp;

thereby to cause an alternating lamp current to flow through the lamp;

the alternating lamp current having a peak magnitude and an RMS magnitude;

the AC voltage being of a frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the inverter and load circuitry being additionally characterized by causing the peak magnitude of the alternating lamp current to be distinctly lower than twice its RMS magnitude.

2. The arrangement of claim 1 wherein the absolute magnitude of the DC voltage is about twice as high as the peak absolute magnitude of the power line voltage.

3. The arrangement of claim 1 wherein:

(a) the gas discharge lamp (i) at certain times draws a lamp current from the AC terminals, (ii) at certain other times, such as if disconnected or otherwise non-functional, draws no lamp current; and

(b) the inverter and load circuitry is characterized by the fact that the frequency of the AC voltage is substantively higher during said certain other times as compared with during said certain times.

18. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including an L-C circuit electrically connected with the AC terminals and having a natural resonance frequency at or near the fundamental frequency of the AC voltage.

19. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including a transistor having a pair of transistor terminals across which exists a transistor voltage and between which periodically flows a transistor current;

the transistor current flowing only during periods when the absolute magnitude of the transistor voltage is substantially lower than that of the DC supply voltage.

20. The arrangement of claim 19 further defined in that current flows between the transistor terminals only during periods when the absolute magnitude of the transistor voltage is smaller than that of the DC supply voltage by a factor of ten or more.

21. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including a certain terminal at which, as referenced to one of the DC terminals, exists a substantially sinusoidal voltage of frequency equal to that of the AC voltage.

22. The arrangement of claim 21 further defined by:

(i) including a periodially conducting transistor having a transistor terminal; and

(ii) having a conductive path between the transistor terminal and said certain terminal, the ohmic resistance of which conductive path being of negligible magnitude.

23. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including a transistor having a pair of transistor terminals between which periodically flows a transistor current, which periodic transistor current has a period equal to that of the AC voltage and, for each complete cycle of the AC voltage, flows for a total time duration that is distinctly shorter than 50% of the total duration of said complete cycle.

24. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including a transistor having a pair of transistor terminals across which exists a periodic transistor voltage and between which flows a transistor current in the form of periodic unidirectional current pulses;

the duration of each unidirectional current pulse being distinctly shorter than half the duration of a complete cycle of the AC voltage.

25. The arrangement of claim 1 wherein the inverter and load circuitry is further defined in that the frequency of the AC voltage is distinctly higher just prior to lamp ignition than it is after the lamp has ignited.

26. The arrangement of claim 1 wherein the inverter and load circuitry is further defined in that the frequency of the AC voltage would increase if the gas discharge lamp were to be disconnected.

27. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including:

(i) a transistor having a pair of transistor terminals;

(ii) a first and a second conductor between which exists an alternating voltage of substantially sinusoidal waveform and with frequency equal to that of the AC voltage, the first conductor being characterized by having an AC potential substantially equal to that of one of the DC terminals, the second conductor being characterized by having a DC potential equal to one of the transistor terminals.

28. The arrangement of claim 27 yet additionally characterized by having a capacitor connected between said one of the transistor terminals and a termination point having an AC potential substantially equal to that of one of the DC terminals.

29. The arrangement of claim 1 wherein the inverter and load circuitry is also characterized by including:

(i) a transistor having a transistor terminal;

(ii) a first and a second conductor between which exists a substantially sinusoidal voltage of frequency equal to that of the AC voltage, the first conductor being characterized by having an AC potential substantially equal to that of one of the DC terminals, the second conductor being characterized by having a DC potential equal to the transistor terminal.

4. A ballasting arrangement for a gas discharge lamp, comprising:

a source providing a DC supply voltage at a set of DC terminals; and

an inverter circuit assembly connected with the DC terminals and operative to provide an inverter output current from a pair of inverter output terminals;

the inverter output current being an alternating current of frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the inverter circuit assembly also including a pair of lamp output terminals adapted to connect with and to supply a lamp current to a gas discharge lamp;

the inverter circuit assembly being otherwise characterized by having;

(i) an inductor means connected between one of the inverter output terminals and one of the lamp output terminals, the inductor means having a frequency-dependent impedance in the sense that its impedance increases with increasing frequency of any current flowing through it;

(ii) a frequency control sub-assembly operative, on receipt of a control action at a control action input, to control the frequency and thereby the magnitude of the inverter output current; and

(iii) an action-generating element-operative, in response to at least a part of the inverter output current, to provide a control action at a control action output;

the control action output being connected in communication with the control action input, thereby to supply thereto said control action, thereby to cause the frequency of the inverter output current to change in response to the magnitude of the inverter output current, thereby to cause the magnitude of the inverter output current to be different from what it would have been in the absence of providing the control action to the frequency control sub-assembly.

5. The ballasting arrangement of claim 4 wherein, by providing said control action to the frequency control sub-assembly, the magnitude of said part of the inverter output current is lower than it would have been in the absence of providing the control action to the frequency control sub-assembly.

6. The ballasting arrangement of claim 4 wherein the provision of said control action to the frequency control sub-asembly constitutes negative feedback in the sense that, if the magnitude of said part of the inverter output current were to change due to a change in the characteristics of a circuit element connected within the inverter circuit assembly, such a change in magnitude will be less because of the provision of said control action to the frequency control sub-assembly than it would have been without the provision of said control action to the frequency control sub-assembly.

7. The ballasting arrangement of claim 4 wherein, if the characteristics of a circuit element connected within the inverter circuit assembly were to be altered, such as by altering the inductance of the inductor means, the magnitude of said part of the inverter output current would change by a certain amount;

which certain amount will be less when actually providing said control action to the frequency control sub-assembly than when not providing said control action to the frequency control sub-assembly.

8. An arrangement comprising:

a source providing a DC supply voltage at a set of DC terminals;

an inverter circuit connected with the DC terminals and operative to provide an AC inverter output voltage at a pair of inverter output terminals;

the AC inverter output voltage being of frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the inverter circuit having a frequency-controlling sub-assembly having a control action input operative, on receipt of a control action signal, to control the frequency of the AC inverter output voltage;

an output circuit connected between the inverter output terminals and a pair of lamp current output terminals;

the output circuit being characterized by including;

(i) a frequency-dependent impedance element, such as an inductor; and

(ii) a an action-signal-generating element having a control action output connected in communication with said control action input and operative to provide said control action signal in response to a current flowing in the output circuit, thereby to affect the frequency of the AC inverter output voltage and, therefore, the magnitude of said current;

whereby the magnitude of said current is different from what it would have been if said control action signal had not been provided to the control action input; and

a gas discharge lamp connected with the lamp current output terminals.

9. The arrangement of claim 8 wherein the action-signal-generating element is operative to provide said control action signal to the control action input in such a manner that any change in the magnitude of said current that might occur due to a reason other than the provision of the control action signal itself will be reduced as a result of providing the control action signal.

10. A ballasting arrangement for a gas discharge lamp, comprising:

a source providing a DC supply voltage at a set of DC terminals; and

an assembly of components connected with the DC terminals and operative to provide an AC voltage at a pair of first terminals;

the assembly being characterized by including various electrical components in addition to output circuitry having an action-generating element operative to provide a control action at a control action output in response to a current flowing in a certain conductor included as part of the output circuitry;

the AC voltage being of frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the assembly also including a pair of second terminals connected with the first terminals by way of the output circuitry;

the second terminals being adapted to connect with and to supply lamp current to a gas discharge lamp;

the assembly being otherwise characterized by;

(a) including an inductor as part of the output circuitry;

(b) having a control sub-assembly operative, on receipt of a control action at a control action input, to control the frequency of the AC voltage, the control action input being functionally connected with the control action output; and

(c) causing a current to flow through the certain conductor;

thereby;

(i) to cause said control action to be supplied from the control action output to the control action input, (ii) to cause the frequency of the AC voltage to be controlled in response to the current flowing through the certain conductor, and (iii) to cause the magnitude of this current to be different from what it would have been in the absence of providing the control action to the control action input.

11. The ballasting arrangement of claim 10 wherein the action-generating element is functional to provide the control action to the control action input in such a manner that any change in the magnitude of the current flowing in said conductor which might occur due to a reason other than the provision of the control action output itself will be reduced as a result of actually providing the control action.

12. An arrangement comprising:

a source providing a DC supply voltage at a set of DC terminals;

an inverter circuit assembly connected with the DC terminals and operative to provide an AC inverter voltage at a pair of AC inverter terminals;

the AC inverter voltage being of a frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the inverter circuit assembly being characterized by including a control subassembly operative, on receipt of a control action at a control action input, to control the frequency of the AC inverter voltage; and

load circuitry connected with the AC inverter terminals;

the load circuitry being characterized by;

(a) including a disconnectable gas discharge lamp;

(b) including an inductor;

(c) including a conductor;

(d) including an action-generating element connected in circuit with the conductor and operative to provide a control action at a control action output in response to a current flowing through the conductor; and

(e) having the control action output connected in communication with the control action input, thereby;

(i) to provide the control action such as to cause;

(i) the frequency of the AC inverter voltage to be controlled in response to the magnitude of the current flowing through the conductor, and (ii) the magnitude of this current to be different from what it would have been in the absence of providing the control action to the control action input.

13. The arrangement of claim 12 wherein the effect of providing the control action is that of causing the frequency of the AC inverter voltage to increase as compared with a situation where the control action is absent.

14. The arrangement of claim 12 wherein the AC output voltage is characterized by having a waveform consisting of:

(i) a first time-segment during which the instantaneous magnitude of the AC inverter voltage remains at a substantially constant negative level;

(ii) a second time-segment during which the instantaneous magnitude of the AC inverter voltage increases in a substantially continuous manner;

(iii) a third time-segment during which the instantaneous magnitude of the AC inverter voltage remains at a substantially constant positive level; and

(iv) a fourth time-segment during which the instantaneous magnitude of the AC inverter voltage decreases in a substantially continuous manner.

15. An arrangement comprising:

a source providing a DC supply voltage at a set of DC terminals; and

inverter and load circuitry connected with the DC terminals and operative to provide an AC voltage at a pair of AC terminals;

the AC voltage being of a frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the inverter and load circuitry being characterized by including (i) an inductor, (ii) a capacitor, (iii) a gas discharge lamp, and (iv) an intermittently conducting transistor;

the AC voltage being characterized by having a waveform consisting of;

(i) a first time-segment during which the instantaneous magnitude of the AC voltage remains at a substantially constant negative level, (ii) a second time-segment during which the instantaneous magnitude of the AC voltage increases in a substantially continuous manner, (iii) a third time-segment during which the instantaneous magnitude of the AC voltage remains at a substantially constant positive level, and (iv) a fourth time-segment during which the instantaneous magnitude of the AC voltage decreases in a substantially continuous manner;

the inverter and load circuitry being further characterized in that substantially no current flows through the transistor during the second and fourth time-segments.

16. An arrangement comprising:

a source providing a DC supply voltage at a set of DC terminals; and

inverter and load circuitry connected with the DC terminals and operative to provide an AC voltage at a pair of AC terminals with which is connected a gas discharge lamp;

the AC voltage being of a frequency substantially higher than that of the power line voltage on an ordinary electric utility power line;

the gas discharge lamp being characterized by drawing a lamp current from the AC terminals at certain times and not at other times;

the inverter and load circuitry being characterized in that the frequency of the AC voltage is different during the times when lamp current is being drawn as compared with times when lamp current is not being drawn.

17. The arrangement of claim 16 wherein the frequency of the AC voltage is lower during the times when lamp current is being drawn as compared with the times when lamp current is not being drawn.