Methods and systems of a switching power converter for controlling average current and with frequency adjustment
A switching power converter for controlling average current and with frequency adjustment. One example embodiment is a method of operating a switching power converter, the method including: operating the switching power controller at a switching frequency that is variable, each switching period comprises a charge mode of an inductor of the switching power converter and a discharge mode of the inductor; controlling, by a current control loop, average current provided from the switching power converter by controlling peak current in each charge mode of the inductor; and regulating, by a frequency control loop, the switching frequency of the switching power. The regulating may include: adjusting a relationship of output voltage to a length of discharge modes of the inductor; and changing the peak current through the inductor during charge modes.
1. A method of operating a switching power converter, the method comprising:
operating the switching power converter at a switching frequency that is variable, each switching period comprises a charge mode of an inductor of the switching power converter and a discharge mode of the inductor;
controlling, by a current control loop, average current provided from the switching power converter by controlling peak current in each charge mode of the inductor; and
regulating, by a frequency control loop, the switching frequency of the switching power converter by:
adjusting a relationship of output voltage to a length of discharge modes of the inductor; and
changing the peak current through the inductor during charge modes.
2. The method of claim 1 ,
wherein adjusting the relationship of output voltage to the length of discharge modes further comprises adjusting proportional to a change in output voltage; and
wherein changing the peak current through the inductor during charge modes further comprises changing proportional to the change in output voltage.
3. The method of claim 2 , wherein adjusting proportional to a change in output voltage further comprises adjusting directly proportional to the change in output voltage.
4. The method of claim 3 , wherein changing proportional to the change in output voltage further comprises changing directly proportional to the change in output voltage.
5. The method of claim 1 , wherein adjusting the relationship of output voltage to length of discharge modes further comprises modifying a value in a control register of a power controller of the switching power converter, the value in the control register defines a mathematical relationship between the length of discharge modes of the inductor and the output voltage.
6. The method of claim 5 , further comprising updating a value indicative of off time of discharge modes, the value indicative of the off time of discharge modes held in an off-time register in the power controller, and the updating proportional to the value in the control register.
7. The method of claim 1 , wherein changing the peak current through the inductor during charge modes comprises:
modifying a value in a control register of a power controller of the switching power converter, the value in the control register defines a mathematical relationship between the length of discharge modes of the inductor and the output voltage; and
revising a value in a ripple-current register of the power controller, wherein the peak current through the inductor during charge modes is controlled based on the value in the ripple-current register.
8. The method of claim 7 , wherein revising the value in the ripple-current register further comprises revising based on the value in the control register and a proportionality value held in a proportionality register of the power controller of the switching power converter.
9. The method of claim 1 ,
wherein adjusting the relationship of output voltage to the length of discharge modes further comprises modifying a value in a control register of a power controller of the switching power converter, the value in the control register defines a mathematical relationship between the length of discharge modes of the inductor and the output voltage;
wherein changing peak current through the inductor during charge modes further comprises revising a value in a ripple-current register of the power controller, wherein the peak current is controlled based on the value in the ripple-current register.
10. The method of claim 1 , wherein, prior to adjusting the relationship of output voltage to the length of discharge modes, and prior to changing the peak current through the inductor during charge modes, the method further comprises updating a first value indicative of off time held in an off-time register in the switching power converter, the updating based on a change of output voltage and a value in a control register of the switching power converter, the value in the control register defines a mathematical relationship between the length of discharge modes of the inductor and the output voltage.
11. A controller for a switching power converter for driving light-emitting diodes (LEDs), the controller comprising:
an input voltage terminal, an output voltage terminal, a switch-node terminal, and a bus interface;
a bus controller coupled to the bus interface;
an average current register accessible by the bus controller, the average current register configured to hold the value indicative of a set point average current;
a ripple-current register accessible by the bus controller, the ripple-current register configured to hold a value indicative of ripple current;
an off-time register accessible by the bus controller, the off-time register configured to hold a value indicative of off time of discharge modes of an inductor;
a control register accessible by the bus controller, the control register configured to hold a value indicative of a mathematical relationship between a length of discharge modes of the inductor and an output voltage of the switching power converter;
a power switch that has first lead coupled to the switch-node terminal, a second lead coupled to the input voltage terminal, and a control input;
a current controller coupled to the ripple-current register, the current controller configured to control an average current provided from the switching power converter by controlling peak current during charge modes of the inductor;
a frequency controller coupled to the control register, the off-time register, and the ripple-current register, the frequency controller configured to regulate switching frequency of the switching power converter by the frequency controller being configured to:
adjust the value indicative of the mathematical relationship between the length of discharge modes of the inductor and the output voltage of the switching power converter; and
change the peak current during charge modes of the inductor.
12. The controller of claim 11 ,
wherein when the frequency controller adjusts the relationship of the output voltage to the length of discharge modes, the frequency controller is further configured to adjust proportional to a change in output voltage; and
wherein when the frequency controller changes the peak current through the inductor during charge modes, the frequency controller is further configured to change proportional to the change in the output voltage.
13. The controller of claim 12 , wherein when the frequency controller adjusts the relationship of the output voltage to the length of discharge modes, the frequency controller is further configured to adjust directly proportional to the change in the output voltage.
14. The controller of claim 11 , wherein when the frequency controller changes the peak current through the inductor during charge modes, the frequency controller is further configured to revise the value in the ripple-current register, and wherein the peak current through the inductor during charge modes controlled based on the value in the ripple-current register.
15. The controller of claim 14 , further comprising:
a proportionality register accessible by the bus controller, the proportionality register configured to hold a proportionality value;
wherein when the frequency controller revises the value in the ripple-current register, the frequency controller is further configured to revise based on the value in the control register and the proportionality value in the proportionality register.
16. A system for operating a light-emitting diodes (LED), the system comprising:
a lighting microcontroller;
a switching power converter communicatively coupled to the lighting microcontroller;
an LED coupled to the switching power converter by way of an inductor;
the switching power converter configured to:
operate at a switching frequency that is variable, and the operation using a length of discharge modes of the inductor, the length of discharge modes is variable based on an output voltage of the switching power converter;
control, by a current controller, average current provided to the LED, the current controller configured to control average current by control of peak current through the inductor during charge modes; and
regulate, by a frequency controller, the switching frequency of the switching power converter by the frequency controller being configured to:
adjust a relationship of the output voltage to the length of discharge modes; and
change a peak current through the inductor during charge modes.
17. The system of claim 16 ,
wherein when the frequency controller adjusts the relationship of the output voltage to the length of discharge modes, the frequency controller is further configured to adjust proportional to a change in the output voltage; and
wherein when the frequency controller changes the peak current through the inductor during charge modes, the frequency controller is further configured to change proportional to the change in the output voltage.
18. The system of claim 17 , wherein when the frequency controller adjusts the relationship of the output voltage to the length of discharge modes, the frequency controller is further configured to adjust directly proportional to the change in the output voltage.
19. The system of claim 16 , wherein the switching power converter further comprises:
a ripple-current register accessible by the lighting microcontroller, the ripple-current register configured to hold a value indicative of ripple current; and
wherein when the frequency controller changes the peak current through the inductor during the charge modes, the frequency controller is further configured to revise the value in the ripple-current register, and wherein the peak current through the inductor during the charge modes is controlled based on the value in the ripple-current register.
20. The system of claim 19 , wherein the switching power converter further comprises:
a proportionality register accessible by the lighting microcontroller, the proportionality register configured to hold a proportionality value; and
wherein when the frequency controller revises the value in the ripple-current register, the frequency controller is further configured to revise based on the value in the control register and the proportionality value in the proportionality register.