Method and device for switching frequency modulation in interleaved power factor correction for onboard charging applications
An interleaved switched mode power supply and control method therefor are disclosed. The interleaved switched mode power supply includes a first switched mode power supply; a second switched mode power supply; and a controller. The controller controls the first and second switched mode power supplies so that the controller and the first and second switched mode power supplies form an interleaved switched mode power supply with power factor correction. The controller modulates a switching frequency of each of the first and second switched mode power supplies such that the switching frequency varies based upon ripple current cancellation between the ripple current of the first switched mode power supply and the ripple current of the second switched mode power supply.
1. An interleaved switched mode power supply apparatus, comprising:
a plurality of parallel-connected switched mode power supplies comprising at least a first switched mode power supply having supply input terminals to receive a supply input voltage and a second switched mode power supply having supply input terminals to receive the supply input voltage; and
a controller having at least one first output coupled to at least one control input of the first switched mode power supply, and at least one second output coupled to at least one control input of the second switched mode power supply, the controller is configured to control the first and second switched mode power supplies so that the controller and the first and second switched mode power supplies comprise an interleaved switched mode power supply with power factor correction,
wherein the controller is configured to modulate a switching frequency of each of the first and second switched mode power supplies such that the switching frequency varies based upon ripple current cancellation between the ripple current of the first switched mode power supply and the ripple current of the second switched mode power supply.
2. The interleaved switched mode power supply apparatus of claim 1 , wherein the switching frequency of the first and second switched mode power supplies varies based upon duty cycle thereof.
3. The interleaved switched mode power supply apparatus of claim 2 , wherein the controller is configured to determine the duty cycle of the first and second switched mode power supplies based at least partly upon the supply input voltage, and determine the switching frequency of the first and second switched mode power supplies based upon the determined duty cycle.
4. The interleaved switched mode power supply apparatus of claim 3 , further comprising a non-transitory memory that is part of or coupled to the controller, the non-transitory memory having stored therein data corresponding to a relationship between duty cycle and switching frequency.
5. The interleaved switched mode power supply apparatus of claim 4 , wherein the data is in the form of a lookup table stored in the non-transitory memory.
6. The interleaved switched mode power supply apparatus of claim 4 , wherein the data is in the form of an equation for the relationship between the duty cycle and the switching frequency.
7. The interleaved switched mode power supply apparatus of claim 2 , wherein the determined switching frequency is highest at
D=n /( N -phases*2),
where D is duty cycle, “N-phases” is the number of switched mode power supplies, and n are odd integers between one and 2*(N-phases).
8. The interleaved switched mode power supply apparatus of claim 2 , wherein the determined switching frequency is lowest at
D=n /( N -phases),
where D is duty cycle, “N-phases” is the number of switched mode power supplies, and n are integers between zero and N-phases.
9. The interleaved switched mode power supply apparatus of claim 1 , further comprising a third switched mode power supply having supply input terminals to receive the supply input voltage, wherein the controller is configured to modulate the switching frequency of each of the first, second and third switched mode power supplies such that the switching frequency varies based upon ripple current cancellation between the ripple current of the first, second and third switched mode power supplies.
10. The interleaved switched mode power supply apparatus of claim 1 , wherein a summed ripple current at at least two predetermined duty cycles is the same as a summed ripple current for interleaved switched mode power supplies operating at a fixed switching frequency, and the summed ripple current of the interleaved switched mode power supply apparatus at duty cycles other than at the at least two predetermined duty cycles is different from the summed ripple current for the interleaved switched mode power supplies operating at the fixed switching frequency.
11. The interleaved switched mode power supply apparatus of claim 1 , wherein the interleaved switched mode power supply apparatus forms at least part of an onboard battery charging apparatus for a vehicle and the supply input voltage is an AC voltage.
12. A method for controlling interleaved switched mode power supply apparatus having a plurality of parallel-connected switched mode power supplies, the method comprising:
receiving an input supply voltage;
modulating, by a controller, a switching frequency of the switched mode power supplies based upon the received input supply voltage;
determining, by the controller, a duty cycle for the switched mode power supplies based upon the received input supply voltage;
determining, by the controller, a switching frequency for the switched mode power supplies based upon the determined duty cycle; and
controlling, by the controller, the switched mode power supplies using the determined duty cycle and the determined switching frequency, wherein modulating the switching frequency forms part of controlling the switched mode power supplies.
13. The method of claim 12 , wherein determining the switching frequency comprises accessing data stored in non-transitory memory of or associated with the controller which provides a relationship between duty cycle and switching frequency.
14. The method of claim 13 , wherein the data is in the form of a lookup table.
15. The method of claim 13 , wherein the data is in the form of an equation describing the relationship between the duty cycle and the switching frequency.
16. The method of claim 12 , wherein the determined switching frequency is highest at
D=n /( N -phases*2),
where D is duty cycle, “N-phases” is the number of switched mode power supplies, and n are odd integers between one and 2*(N-phases).
17. The method of claim 12 , wherein the determined switching frequency is lowest at
D=n /( N -phases),
where D is duty cycle, “N-phases” is the number of switched mode power supplies, and n are integers between zero and N-phases.
18. A computer program product stored in non-transitory memory having instructions which, when executed by a controller of an interleaved switched mode power supply, causes the controller to perform a method comprising:
receiving an indication of an input supply voltage;
modulating a switching frequency of the interleaved switched mode power supplies based upon the input supply voltage;
determine a duty cycle for the interleaved switched mode power supplies based upon the received input supply voltage;
determine a switching frequency for the interleaved switched mode power supplies based upon the determined duty cycle; and
control the interleaved switched mode power supply using the determined duty cycle and the determined switching frequency, wherein modulating the switching frequency forms part of controlling the interleaved switched mode power supplies.