Two-mode electronic ballast

• US 4,935,669 A
• Filed: 01/20/1988
• Issued: 06/19/1990
• Est. Priority Date: 01/20/1988
• Status: Expired due to Term

• Current Assignee: Ole K Nilssen
• Original Assignee: Ole K Nilssen
• Inventors: Nilssen, Ole K.
• Primary Examiner(s): LaRoche, Eugene R.
• Assistant Examiner(s): Shingleton, Michael B.
• Application Number:
  US07/145,925
• Time in Patent Office: 881 Days
• Field of Search: 315/DIG. 5, 315/209 R, 315/291, 315/DIG. 7, 315/205, 315/278, 315/105
• US Class Current: 315/105
• 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: Y10S 315/05 Starting and operating circuit for fluorescent lamp
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

A self-oscillating inverter-type fluorescent lamp ballast has two modes of operation: (a) a first mode in which the inversion frequency is about 70 kHz and is resonant with a first tuned circuit by which power is supplied to the cathodes of the fluorescent lamp; and (b) a second mode in which the inversion frequency is about 30 kHz and is resonant with a second tuned circuit by which main lamp power is supplied. When the ballast is initially powered-up, it starts operation in its first mode, thereby providing cathode heating power without yet providing main lamp power. About one second later, after the cathodes have reached full incandescence, the inverter automatically changes into its second mode, thereby providing main lamp power while at the same time removing cathode heating power. If for some reason the lamp were not to ignite within about 10 milli-seconds, the inverter reverts back into its first mode; thereafter cycling between its two modes until the lamp does ignite.

Claims

1. An arrangement comprising:

self-oscillating inverter means connected with a source of DC voltage and operative to provide an inverter voltage at an inverter output, the inverter voltage having a frequency, the inverter means being self-oscillating by way of positive feedback means and having control means operative in response to a control input to control the self-oscillation frequency;

gas discharge lamp means having;

(i) main lamp terminals operative to receive main lamp operating power, and (ii) thermionic cathode means having cathode terminals operative to receive cathode heating power;

impedance means connected in circuit between the inverter output, the main lamp terminals, and the cathode terminals, the impedance means being operative to supply from the inverter output main lamp operating power to the main lamp terminals and cathode heating power to the cathode terminals, the amount of main lamp operating power and the amount of cathode heating power supplied both being dependent on the frequency of the inverter voltage; and

control means operative to provide the control input in such manner as to control the frequency of the inverter voltage, thereby to control the amount of main lamp operating power as well as the amount of cathode heating power.

2. The arrangement of claim 1 wherein:

(i) the amount of cathode heating power supplied to the cathode terminals is a first function of the frequency of the inverter voltage, and (ii) the amount of main lamp operating power is a second function of the frequency of the inverter voltage, the second function being substantively different from the first function.

3. The arrangement of claim 2 wherein the amount of cathode heating power supplied decreases as the amount of main lamp operating power increases.

4. The arrangement of claim 1 wherein the impedance means comprises a first and a second tuned circuit means, the first tuned circuit means being operative to determine the amount of cathode heating power being supplied to the cathode terminals, the second tuned circuit means being operative to determine the amount of main lamp operating power being supplied to the main lamp terminals.

5. The arrangement of claim 1 combined with current sensing means connected in circuit with the main lamp terminals as well as with the control means, the current sensing means being operative to sense lamp current flowing between the main lamp terminals and, in response to this lamp current, to provide at least part of the control input.

6. The arrangement of claim 1 wherein the impedance means comprises a series-tuned L-C circuit connected across the inverter output.

7. An arrangement comprising:

inverter means connected with a source of DC voltage and operative to provide an inverter voltage at an inverter output, the inverter voltage having a frequency, the inverter means having control means operative in response to a control input to control this frequency;

gas discharge lamp means having;

(i) main lamp terminals operative to receive main lamp operating power, and (ii) thermionic cathode means having cathode terminals operative to receive cathode heating power;

impedance means connected in circuit between the inverter output, the main lamp terminals, and the cathode terminals, the impedance means being operative to supply from the inverter output main lamp operating power to the main lamp terminals and cathode heating power to the cathode terminals, the amount of main lamp operating power and the amount of cathode heating power supplied both being dependent on the frequency of the inverter voltage; and

control means operative to provide the control input in such manner as to control the frequency of the inverter voltage between a first frequency and a second frequency;

such that the arrangement is operative to provide;

(i) a substantive amount of cathode heating power but only a negligible amount of main lamp operating power at the first frequency, and (ii) a negligible amount of cathode heating power but a substantive amount of lamp operating power at the second frequency.

8. An arrangement comprising:

inverter means connected with a source of DC voltage and operative to provide an inverter voltage at an inverter output, the inverter voltage having a frequency, the inverter means having control means operative in response to a control input to control this frequency;

gas discharge lamp means having;

(i) main lamp terminals operative to receive main lamp operating power, and (ii) thermionic cathode means having cathode terminals operative to receive cathode heating power;

impedance means connected in circuit between the inverter output, the main lamp terminals, and the cathode terminals, the impedance means being operative to supply from the inverter output main lamp operating power to the main lamp terminals and cathode heating power to the cathode terminals, the magnitude of the main lamp operating voltage and the magnitude of the cathode heating voltage both being dependent on the frequency of the inverter voltage; and

control means operative to provide the control input in such manner as to control the frequency of the inverter voltage between a first frequency and a second frequency;

such that the arrangement is operative to provide;

(i) at the first frequency, a substantive magnitude of cathode heating voltage but only a negligible magnitude of main lamp operating voltage, and (ii) at the second frequency, a substantive magnitude of main lamp operating voltage.

9. In a power supply means connected with and operative to power a gas discharge lamp, the lamp having a pair of main lamp terminals and a cathode, the cathode having a pair of cathode terminals, an improvement comprising:

(1) control input means operative in response to a control input to cause the power supply means to function in either of two modes;

(a) a first mode wherein;

(i) a first cathode voltage is provided to the cathode terminals, and (ii) a first lamp voltage is provided to the main lamp terminals, the magnitude of the first lamp voltage being insufficient to cause lamp ignition; and

(b) a second mode wherein;

(i) a second cathode voltage is provided to the cathodes, the magnitude of the second cathode voltage being substantially lower than that of the first cathode voltage, and (ii) a second lamp voltage is provided to the main lamp terminals, the magnitude of the second lamp voltage being sufficient to cause lamp ignition; and

(2) control output means connected with the control input means and operative to provide the control input, thereby to cause the power supply means to exist in the first mode for a period of time before causing it to change to the second mode.

10. The improvement of claim 9 wherein the magnitude of the second lamp voltage is substantially larger than that of the first lamp voltage.

11. The improvement of claim 9 wherein the first lamp voltage has a first frequency and the second lamp voltage has a second frequency, the first frequency being different from the second frequency.

12. An arrangement comprising:

power supply means operative to power a gas discharge lamp, the gas discharge lamp having a pair of main lamp terminals and a thermionic cathode, the thermionic cathode having a pair of cathode terminals, the power supply means having;

(i) a first and a second pair of output terminals operative, respectively, to connect with the main lamp terminals and the cathode terminals and to provide thereto, respectively, a main lamp voltage and a cathode voltage, and (ii) control input means receptive of a control input and operative in response thereto to control the magnitude of the main lamp voltage; and

control output means connected with the control input means and operative to provide the control input such as to cause the power supply means to exist in either of two modes;

(1) a first mode in which;

(i) the cathode voltage is of a first magnitude sufficient to cause the thermionic cathode to become incandescent, and (ii) the main lamp voltage is of a magnitude sufficient to cause the gas discharge lamp to ignite; and

(2) a second mode in which;

(i) the cathode voltage is of a second magnitude, the second magnitude being substantially lower than the first magnitude, and (ii) the main lamp voltage is of a magnitude sufficient to cause the gas discharge lamp to ignite.

13. The arrangement of claim 12 wherein:

(i) at any given time, the frequency of the main lamp voltage is the same as that of the cathode voltage, and (ii) the frequency of the main lamp voltage during the first mode is different from the frequency of the main lamp voltage during the second mode.

14. The arrangement of claim 12 wherein the control input means is operative to control the magnitude of the main lamp voltage by way of controlling its frequency.

15. The arrangement of claim 12 wherein the power supply comprises tuned circuit means.

16. An arrangement comprising:

inverter operative to provide an inverter output voltage at an inverter output means;

the inverter having switching transistor means including transistor drive input means;

the inverter being self-oscillating by way of positive feedback means connected in circuit between the inverter output means and the transistor drive input means;

the inverter having frequency control input means operative, on receipt of a control signal, to control the frequency of the inverter output voltage;

gas discharge lamp having;

(i) main lamp terminals receptive of a main lamp voltage, and (ii) a thermionic cathode having cathode terminals receptive of a cathode heating voltage;

frequency-discriminating circuit means connected between;

(i) the inverter output means, (ii) the lamp input terminals, and (iii) the cathode terminals;

the frequency-discriminating circuit means being operative to cause a cathode voltage to be applied at the cathode terminals and a main lamp voltage to be applied at the main lamp terminals;

the magnitude of the cathode voltage being a first function of the frequency;

the magnitude of the main lamp voltage being a second function of frequency;

the second function being substantially different from the first function; and

control means connected with the frequency control input means and operative to provide said control signal, thereby to cause the frequency of the inverter output voltage to vary such as;

(i) initially to cause the cathode voltage to be of a first magnitude and the main lamp voltage to be of a second magnitude, such as to provide a sufficient amount of cathode heating power to the termionic cathode to reach incandescence without causing the gas discharge lamp to ignite, and (ii) subsequently, after the termionic cathode has reached incandescence, to cause the first magnitude to decrease by a substantial degree while at the same time to cause the second magnitude to increase substantially, thereby to cause the gas discharge lamp to ignite and operate while at the same time causing the amount of cathode heating power provided to the thermionic cathode to decrease to a substantial degree.