Method and firmware for controlling voltage and current in a fluorescent lamp array
View Patent ↗A method and firmware for controlling voltage and current in an electrical load includes steps of calculating a numerically quantized duty cycle of a pulse-width modulated, digital switch control signal by firmware in an inverter voltage microcontroller as a function of an inverter voltage and controlling the inverter voltage by adjusting the duty cycle of the digital switch control signal to generate a load current in the electrical load.
1. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the load current microcontroller is further configured to conditionally set a digital command signal to request a decrease in the inverter voltage output if the load current through the lamp is above a load current set point for the lamp and the duty cycle of the digital switch control signal is below a threshold.
2. The apparatus of claim 1 , wherein the load current microcontroller is further configured to measure the load current through the lamp of the array of lamps to determine whether to adjust the duty cycle.
3. The apparatus of claim 2 , wherein the load current microcontroller is configured to measure the load current through the lamp of the array of lamps by dual-slope integration.
4. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the load current microcontroller is further configured to conditionally set a digital command signal to request an increase in the inverter voltage output if the load current through the lamp is below a load current set point for the lamp and the duty cycle of the digital switch control signal is above a threshold.
5. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the load current microcontroller is further configured to conditionally set a digital command signal to maintain the inverter voltage output if the load current through the lamp is substantially equal to a load current set point for the lamp.
6. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the inverter voltage microcontroller is further configured to adjust the duty cycle of the digital switch control signal in response to a digital command signal from the load current microcontroller.
7. The apparatus of claim 6 , wherein the inverter voltage microcontroller is configured to increment the duty cycle by a numerically-quantized increment based on the digital command signal from the load current microcontroller.
8. The apparatus of claim 6 , wherein the inverter voltage microcontroller is configured to decrement the duty cycle by a numerically-quantized decrement.
9. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the load current microcontroller is further configured to set a digital command signal to indicate a load open-circuit condition in response to a determination that the load current through the lamp is below a load open-circuit threshold.
10. An apparatus, comprising:
an inverter voltage microcontroller configured to generate a digital switch control signal having a duty cycle, wherein the duty cycle of the digital switch control signal is configured to control an inverter voltage output for an array of lamps; and
a load current microcontroller configured to adjust the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps, wherein the load current microcontroller is further configured to set a digital command signal to indicate a load short-circuit condition in response to a determination that the load current through the lamp is above a load short-circuit threshold.
11. A method comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining that the load current through the lamp is above a load current set point for the lamp and the duty cycle of the digital switch control signal is below a threshold; and
decreasing the inverter voltage output based on said determining that the load current through the lamp is above the load current set point for the lamp and the duty cycle of the digital switch control signal is below the threshold.
12. The method of claim 11 , further comprising:
measuring the load current through the lamp of the array of lamps to determine whether to adjust the duty cycle.
13. The method of claim 12 , wherein said measuring the load current through the lamp comprises measuring the load current through the lamp of the array of lamps by dual-slope integration.
14. A method comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining the load current through the lamp is below a load current set point for the lamp and the duty cycle of the digital switch control signal is above a threshold; and
increasing the inverter voltage output based on said determining the load current through the lamp is below the load current set point for the lamp and the duty cycle of the digital switch control signal is above the threshold.
15. A method comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining that the load current through the lamp is substantially equal to a load current set point for the lamp; and
maintaining the inverter voltage output based on said determining that the load current through the lamp is substantially equal to the load current set point for the lamp.
16. A method comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps; and
incrementing the duty cycle by a numerically-quantized increment or decrementing the duty cycle by a numerically-quantized decrement based on a digital command signal from a load current controller.
17. A method comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps; and
indicating a load open-circuit condition in response to a determination that the load current through the lamp is below a load open-circuit threshold, or
indicating a load short-circuit condition in response to a determination that the load current through the lamp is above a load short-circuit threshold.
18. An article of manufacture including a computer-readable medium having instructions stored thereon that, upon execution by a computing device, cause the computing device to perform operations comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining that the load current through the lamp is above a load current set point for the lamp and the duty cycle of the digital switch control signal is below a threshold; and
decreasing the inverter voltage output based on said determining that the load current through the lamp is above the load current set point for the lamp and the duty cycle of the digital switch control signal is below the threshold.
19. The article of manufacture of claim 18 , wherein the operations further comprise:
measuring the load current through the lamp of the array of lamps to determine whether to adjust the duty cycle.
20. The article of manufacture of claim 19 , wherein said measuring the load current through the lamp comprises measuring the load current through the lamp of the array of lamps by dual-slope integration.
21. An article of manufacture including a computer-readable medium having instructions stored thereon that, upon execution by a computing device, cause the computing device to perform operations comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining the load current through the lamp is below a load current set point for the lamp and the duty cycle of the digital switch control signal is above a threshold; and
increasing the inverter voltage output based on said determining the load current through the lamp is below the load current set point for the lamp and the duty cycle of the digital switch control signal is above the threshold.
22. An article of manufacture including a computer-readable medium having instructions stored thereon that, upon execution by a computing device, cause the computing device to perform operations comprising:
generating a digital switch control signal having a duty cycle configured to control an inverter voltage output for an array of lamps;
adjusting the duty cycle of the digital switch control signal to regulate a load current through a lamp of the array of lamps;
determining that the load current through the lamp is substantially equal to a load current set point for the lamp; and
maintaining the inverter voltage output based on said determining that the load current through the lamp is substantially equal to the load current set point for the lamp.