Bi-modal voltage limit control to maximize ultra-capacitor performance
An electrical system that is operable to selectively provide electrical power to power a load includes an ultra-capacitor that selectively stores and discharges electrical power and a control module that determines an operating ratio based an ON power state and an OFF power state of the ultra-capacitor. The control module calculates a voltage limit of the ultra-capacitor based on the operating ratio and regulates operation of the ultra-capacitor based on the voltage limit.
1. An electrical system that is operable to selectively provide electrical power to power a load, comprising:
an ultra-capacitor that selectively stores and discharges electrical power; and
a control module that determines an operating ratio based on an ON power state and an OFF power state of said ultra-capacitor, that calculates a voltage limit of said ultra-capacitor based on said operating ratio and that regulates operation of said ultra-capacitor based on said voltage limit.
2. The electrical system of claim 1 wherein said control module calculates said voltage limit based on a target life expectancy (Y target ).
3. The electrical system of claim 2 wherein said Y target is equal to one of a minimum allowed life expectancy (Y operating ) and a minimum needed life expectancy (Y idle ) based on said power states of said ultra-capacitor.
4. The electrical system of claim 1 wherein said control module calculates a temporary ratio as a ratio between an operating time and a total time, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
5. The electrical system of claim 1 wherein said control module calculates a temporary ratio as a ratio between an operating time and a time threshold, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
6. The electrical system of claim 1 further comprising a temperature sensor that is responsive to a temperature of said ultra-capacitor, wherein said voltage limit is calculated based on said temperature.
7. The electrical system of claim 1 wherein said control module determines whether a power state of said ultra-capacitor is transitioning from said ON state to said OFF state and calculates said operating ratio as a ratio between an operating time and a total time when said power state is transitioning from said ON state to said OFF state and said total time is greater than a threshold time.
8. A method of increasing operating voltage range and energy storage capacity of an ultra-capacitor, comprising:
determining an operating ratio based on an operating period and a non-operating period of said ultra-capacitor;
calculating a voltage limit of said ultra-capacitor based on said operating ratio; and
regulating operation of said ultra-capacitor based on said voltage limit.
9. The method of claim 8 wherein said voltage limit is determined based on a target life expectancy (Y target ).
10. The method of claim 9 wherein said Y target is equal to one of a minimum allowed life expectancy (Y operating ) and a minimum needed life expectancy (Y idle ) based on a power state of said ultra-capacitor.
11. The method of claim 8 further comprising calculating a temporary ratio as a ratio between an operating time and a total time, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
12. The method of claim 8 further comprising calculating a temporary ratio as a ratio between an operating time and a time threshold, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
13. The method of claim 8 further comprising monitoring a temperature of said ultra-capacitor, wherein said voltage limit is calculated based on said temperature.
14. The method of claim 8 further comprising:
determining whether a power state of said ultra-capacitor is transitioning from an ON state to an OFF state; and
calculating said operating ratio as a ratio between an operating time and a total time when said power state is transitioning from said ON state to said OFF state and said total time is greater than a threshold time.
15. The method of claim 8 further comprising determining whether said power state is transitioning from said ON state to said OFF state.
16. The method of claim 15 further comprising calculating a temporary ratio as a ratio between an operating time and a total time when said power state is not transitioning from said ON state to said OFF state, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
17. The method of claim 15 further comprising calculating a temporary ratio as a ratio between an operating time and a time threshold when said power state is not transitioning from said ON state to said OFF state, wherein said operating ratio is set equal to said temporary ratio if a previous value of said operating ratio is less than said temporary ratio.
18. The method of claim 15 further comprising calculating said operating ratio as a ratio between an operating time and a total time when said power state is transitioning from said ON state to said OFF state and said total time is greater than a threshold time.
19. A method of increasing operating voltage range and energy storage capacity of an ultra-capacitor, comprising:
determining whether a power state of said ultra-capacitor is one of an ON state and an OFF state;
calculating an operating ratio of said ultra-capacitor based on said power state;
calculating a voltage limit of said ultra-capacitor based on said operating ratio; and
regulating operation of said ultra-capacitor based on said voltage limit.
20. The method of claim 19 wherein said voltage limit is determined based on a target life expectancy (Y target ).
21. The method of claim 20 wherein said Y target is equal to one of a minimum allowed life expectancy (Y operating ) and a minimum needed life expectancy (Y idle ) based on said power state of said ultra-capacitor.
22. The method of claim 21 wherein Y target is equal to Y operating when said power state is ON and Y target is equal to Y idle when said power state is OFF.
23. The method of claim 19 further comprising monitoring a temperature of said ultra-capacitor, wherein said voltage limit is calculated based on said temperature.