Ballast control IC with power factor correction

• US 6,617,805 B2
• Filed: 10/19/2001
• Issued: 09/09/2003
• Est. Priority Date: 10/20/2000
• Status: Expired due to Term

• Current Assignee: Infineon Technologies Americas Corp. (Infineon Technologies AG)
• Original Assignee: International Rectifier Corporation (Infineon Technologies AG)
• Inventors: Wilhelm, Dana S., Ribarich, Thomas J.
• Primary Examiner(s): NGUYEN, HOANG V
• Application Number:
  US09/981,753
• Publication Number:
  US 20020047635A1
• Time in Patent Office: 690 Days
• Field of Search: 315/307, 315/70, 315/291, 315/209.R, 315/224, 315/308, 315/347, 315/247, 315/127, 315/91, 315/27, 315/DIG.4, 315/DIG.5, 315/DIG.7, 315/324
• US Class Current: 315/247
• CPC Class Codes: H05B 41/282 with semiconductor devices H05B41/2806, H05B41/288, H05B41/295 take precedence
• CPC Class Codes: H05B 41/2981 for protecting the circuit against abnormal operating conditions
• CPC Class Codes: H05B 41/2985 against abnormal lamp operating conditions
• CPC Class Codes: H05B 41/38 Controlling the intensity of light
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

An integrated circuit with both ballast control and driver circuitry and power factor correction (PFC) control circuitry. At the beginning of preheating, power is provided to the load circuit at a voltage below a voltage at which the lamp can ignite, and the PFC control circuitry can then bring the DC bus voltage up to its running value. For this purpose, the PFC circuitry is enabled depending on the mode of the ballast control and driver circuitry. The DC bus voltage is regulated at a lower loop speed when the lamp is running than when the lamp is ramping to ignition, to alleviate DC bus droop. A criterion is applied to determine whether over-current detect signals indicate an actual fault. For this purpose, detect signals during ignition ramping can be counted and compared with a fault number. A lamp end-of-life condition can be detected by comparing sensed voltage with upper and lower window voltages. When a lamp is off for only a short time, it can be quickly restarted without full preheating.

Claims

1. An integrated circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, and that responds to the sense signals by modifying the drive signals;

the ballast control and driver circuitry further having a set of two or more modes in any of which it can operate;

the ballast control and driver circuitry making transitions between the modes in response to the sense signals;

power factor correction circuitry that regulates the power provided to the load circuit by the power supply circuit;

enable circuitry that receives a first mode signal with information about the mode in which the ballast control and driver circuitry is operating and, in response, enables or disables the regulation circuitry; and

loop speed circuitry that receives a second mode signal with information about the mode in which the ballast control and driver circuitry is operating and, in response, causes the regulation circuitry to operate at a control loop speed that depends on the second mode signal;

the sense signals including current sense signals indicating current through the lamp and voltage sense signals indicating voltage across the fluorescent lamp;

the ballast control and driver circuitry including;

drive circuitry that provides the drive signals;

fault detection circuitry that receives current sense signals and provides a detect signal when current through the lamp exceeds a threshold;

filter circuitry that receives the detect signals and, if the detect signals meet a filter criterion, causes the drive circuitry to cease providing the drive signals; and

end-of-life detection circuitry that receives the voltage sense signals and, if the indicated voltage across the lamp indicates that the lamp is nearing the end of its life, causes the drive circuitry to cease providing the drive signals;

the ballast control and driver circuitry operating to;

provide a first sequence of drive signals that cause the power supply circuit to provide power to the load circuit to start the lamp;

the first sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided for a first duration;

in response to the sense signals, cease providing drive signals at a time while the lamp is running; and

provide a second sequence of drive signals that cause the power supply circuit to provide power to the load circuit for restarting the lamp;

the second sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided in the second sequence for a second duration that is shorter than the first duration.

2. An integrated circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, and that responds to the sense signals by modifying the drive signals; and

power factor control circuitry that regulates the voltage at which power is provided to the load circuit by the power supply circuit, further wherein

the power supply circuit includes a half bridge circuit with low and high side power devices, the drive signals including low side drive signals to control the low side power device and high side drive signals to control the high side power device;

the ballast control and driver circuitry including a low side drive output for providing the low side drive signals to the low side power device and a high side drive output for providing the high side drive signals to the high side power device.

3. A method of controlling a power supply circuit and a load circuit that includes a fluorescent lamp, the power supply circuit providing power to the load circuit, the method comprising the steps of:

beginning to operate the fluorescent lamp by providing preheat drive signals that cause the power supply circuit to provide power to the load circuit for preheating the lamp; and

at the beginning of the preheat drive signals, beginning to provide power at a non-operating voltage and increasing to an operating voltage, the non-operating voltage being a voltage at which the lamp cannot ignite.

4. The method of claim 3, further comprising maintaining the operating voltage while the lamp is running.

5. A control circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

driver circuitry that provides drive signals to the power supply circuit, the driver circuitry providing off drive signals that prevent the power supply circuit from providing power to the load circuit, then providing on drive signals that cause the power supply circuit to provide power to the load circuit for preheating the lamp;

power factor correction circuitry that boosts the voltage at which power is provided to the load circuit; and

enable circuitry that receives a coordination signal indicating whether the driver circuitry is providing off drive signals or on drive signals and, in response, disabling the power factor correction circuitry while off drive signals are provided and enabling the power factor correction circuitry no sooner than when on drive signals begin;

when the power factor correction circuitry is enabled at the beginning of the on drive signals, power being initially provided at an unboosted voltage at which the lamp cannot ignite.

6. The control circuit of claim 5 in which, as preheating continues, the power factor correction circuitry increases the voltage at which power is provided until reaching a boosted voltage.

7. A control circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, and that responds to the sense signals by modifying the drive signals;

the ballast control and driver circuitry further having a set of two or more modes in any of which it can operate, the ballast control and driver circuitry making transitions between the modes in response to the sense signals;

power factor correction circuitry that regulates the voltage at which power is provided to the load circuit; and

enable circuitry that receives a mode signal with information about the mode in which the ballast control and driver circuitry is operating and, in response, enables or disables the power factor correction circuitry.

8. The control circuit of claim 7, in which the set of modes includes operating modes and non-operating modes, and the mode signal indicates whether the ballast control and driver circuitry is in one of the operating modes or in one of the non-operating modes, if the mode signal indicates an operating mode, the enable circuitry enables the power factor correction circuitry;

if the mode signal indicates a non-operating mode, the enable circuitry disables the power factor correction circuitry.

9. The control circuit of claim 8, in which the operating modes include a preheat mode, an ignition ramp mode, and a run mode and in which the non-operating modes include a fault mode and an under voltage lockout mode.

10. The control circuitry of claim 9, in which the preheat mode follows the under voltage lockout mode;

during the non-operating modes, power is provided at a non-operating voltage below a voltage at which the lamp ignites;

the power factor correction circuitry beginning to operate not before the beginning of the preheat mode so that power is initially provided at the non-operating voltage during the preheat mode.

11. A method of controlling a power supply circuit which provides power from a DC bus to a load circuit that includes a fluorescent lamp, comprising the steps of:

providing drive signals that cause the power supply circuit to provide power to the load circuit, the drive signals including ignition ramp drive signals for ramping the fluorescent lamp to ignition and run drive signals for running the lamp;

while providing the ignition ramp drive signals, regulating voltage on the DC bus at a first control loop speed; and

while providing the run drive signals, regulating voltage on the DC bus at a second control loop speed that is less than the first control loop speed.

12. A control circuit for controlling a power supply circuit which provides power from a DC bus to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, and that responds to the sense signals by modifying the drive signals;

the ballast control and driver circuitry further having a set of modes in which it can operate;

the ballast control and driver circuitry making transitions between the modes in response to the sense signals;

regulation circuitry that regulates a voltage on the DC bus; and

loop speed circuitry that receives a mode signal with information about the mode in which the ballast control and driver circuitry is operating and, in response, causes the regulation circuitry to operate at a control loop speed that depends on the mode signal.

13. The control circuit of claim 12, in which the modes include an ignition ramp mode and a run mode during which the ballast control and driver circuitry provides drive signals that cause the power supply circuit to provide power to the load circuit for ramping the lamp to ignition and for running the lamp, respectively, the mode signal providing information about when the ballast control and driver circuitry makes a transition from the ignition ramp mode to the run mode;

the loop speed circuitry causing the regulation circuitry to go from a higher control loop speed to a lower control loop speed when the ballast control and driver circuitry makes the transition.

14. The control circuit of claim 12, in which the regulation circuitry includes PFC control circuitry.

15. An integrated circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives current sense signals indicating current through the lamp, and that responds to the current sense signals by modifying the drive signals;

the ballast control and driver circuitry including;

drive circuitry that provides the drive signals;

fault detection circuitry that receives the current sense signals and provides a detect signal when current through the lamp exceeds a threshold; and

filter circuitry that receives the detect signals and, if the detect signals meet a filter criterion, causes the drive circuitry to cease providing the drive signals.

16. The integrated circuit of claim 15, in which the filter circuitry includes a counter for counting the number of detect signals, the filter circuitry causing the drive circuitry to cease only if the number of detect signals reaches a fault number.

17. The integrated circuit of claim 16, in which the ballast control and driver circuitry has an ignition ramp mode during which it provides drive signals that cause the power supply circuit to provide power to the load circuit for ramping the fluorescent lamp to ignition;

the counter operating only during the ignition ramp mode to determine whether the number of detect signals reaches the fault number;

the fault number being larger than the number of times that current through the lamp would normally exceed the threshold during the ignition ramp mode.

18. The integrated circuit of claim 17, in which the ballast control and driver circuitry has a run mode during which it provides drive signals that cause the power supply circuit to provide power to the load circuit for running the fluorescent lamp;

the counter not operating during the run mode so that the filter circuitry causes the drive circuitry to cease each time a detect signal occurs.

19. A control circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives voltage sense signals indicating a voltage across the lamp, and that responds to the voltage sense signals by modifying the drive signals;

the ballast control and driver circuitry including;

drive circuitry that provides the drive signals;

end-of-life detection circuitry that receives the voltage sense signals and, if the indicated voltage across the lamp indicates that the lamp is nearing the end of its life, causes the drive circuitry to cease providing the drive signals.

20. An integrated circuit that includes the control circuit of claim 19, the integrated circuit further including a voltage sense pin for receiving the voltage sense signals.

21. The control circuit of claim 19, in which the end-of-life detection circuitry compares voltages indicated by the voltage sense signals with upper and lower window voltages;

the end-of-life detection circuitry causing the drive circuitry to cease if the indicated voltage exceeds the upper window voltage or is less than the lower window voltage.

22. The control circuit of claim 21, in which the ballast control and driver circuitry further includes threshold circuitry that receives the voltage sense signals and, when the indicated voltage exceeds a threshold voltage, causes the drive circuitry to cease providing the drive signals;

the threshold voltage being greater than the upper window voltage.

23. The control circuit of claim 22, in which the ballast control and driver circuitry has a set of modes including a run mode during which it provides drive signals that cause the power supply circuit to provide power to the load circuit for running the lamp;

the end-of-life detection circuitry providing an end-of-life signal when the indicated voltage exceeds the upper window voltage or is less than the lower window voltage;

the threshold circuitry providing a over-threshold signal when the indicated voltage exceeds the threshold voltage;

the ballast control and driver circuitry further including;

shutdown circuitry that receives the end-of-life signals and the over-threshold signals and that causes the drive circuitry to cease in response to the end-of-life signal only during the run mode but causes the drive circuitry to cease in response to the over-threshold signal during any of the set of modes.

24. A method of controlling a power supply circuit which supplies power to a load circuit that includes a fluorescent lamp, comprising the steps of:

providing a first sequence of drive signals that cause the power supply circuit to provide power to the load circuit to start the fluorescent lamp;

the first sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided for a first duration;

in response to sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, ceasing to provide drive signals at a time while the lamp is running; and

providing a second sequence of drive signals that cause the power supply circuit to provide power to the load circuit for restarting the lamp;

the second sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided in the second sequence for a second duration that is shorter than the first duration.

25. The method of claim 24, further comprising:

measuring an interval from when drive signals cease until a restart time after which the fluorescent lamp can be restarted; and

if the measured interval is less than a time after which the fluorescent lamp requires full preheating, providing the second sequence of drive signals with the second duration shorter than the first duration.

26. A control circuit for controlling a power supply circuit which delivers power to a load circuit that includes a fluorescent lamp, comprising:

ballast control and driver circuitry that provides drive signals to the power supply circuit, that receives sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, and that responds to the sense signals by modifying the drive signals;

the ballast control and driver circuitry operating to;

provide a first sequence of drive signals that cause the power supply circuit to provide power to the load circuit to start the lamp;

the first sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided for a first duration;

in response to sense signals indicating operating conditions of at least one of the power supply circuit and the load circuit, cease providing drive signals at a time while the lamp is running; and

provide a second sequence of drive signals that cause the power supply circuit to provide power to the load circuit for restarting the lamp;

the second sequence including preheat drive signals for preheating the lamp and run drive signals for running the lamp;

the preheat drive signals being provided in the second sequence for a second duration that is shorter than the first duration.

27. An integrated circuit that includes the control circuit of claim 26, the integrated circuit further including a sense pin for receiving the sense signals.