Synchronization of hysteretic power converters
A novel method to synchronize the switching frequency of hysteretic power converters is presented. The method includes the generation of a clock signal and the injection of a periodic disturbance signal operating at the frequency of the generated clock in the main loop of the converter to synchronize the hysteretic power converter to switch at the frequency of the clock. The presented approach provides significant advantages with respect to the more traditional means of utilizing Frequency Lock Loop, Phase Lock Loop or Delay Lock Loop circuits, mainly for its simplicity, faster locking and much reduced phase error. The switching frequency can be higher or lower than the free running frequency of the power converter provided that the free running frequency is close enough to the desired switching frequency. The method is presented for buck and boost hysteretic high frequency switching power converters.
1. A hysteretic power converter,
wherein the switching frequency of said hysteretic power converter is synchronized to a desired frequency,
wherein synchronization is obtained with an open loop system, by means of injection of a disturbance signal into a feedback network of said hysteretic power converter, and
wherein said disturbance signal is a periodic signal operating at said desired frequency.
2. The hysteretic power converter of claim 1 , wherein said hysteretic power converter is a hysteretic boost power converter.
3. The hysteretic power converter of claim 1 , wherein said disturbance signal is a current signal.
4. The hysteretic power converter of claim 1 , wherein said disturbance signal is generated by a switch in series to at least one passive component;
wherein said switch is driven by a signal operating at said desired frequency;
wherein said switch is coupled to a positive or a negative terminal of a power source, and to said at least one passive component, and
wherein said at least one passive component is coupled to a node of said feedback network of said hysteretic power converter.
5. The hysteretic power converter of claim 1 , wherein said disturbance signal is generated by a current source operated at said desired frequency.
6. The hysteretic power converter of claim 1 , wherein said desired frequency is independent from a free running switching frequency of said hysteretic power converter.
7. The hysteretic power converter of claim 1 , wherein an amplitude of said disturbance signal is adaptively varied depending on operating conditions of said hysteretic power converter in order to reach an adequate level required to synchronize said hysteretic power converter with minimum adverse effects.
8. The hysteretic power converter of claim 1 , wherein a free running frequency of said hysteretic power converter is adjusted to be in locking range of said disturbance signal.
9. The hysteretic power converter of claim 1 , wherein said synchronization to said desired frequency occurs only in Continuous Conduction Mode.
10. A method to synchronize the switching frequency of a hysteretic power converter to a desired frequency comprising:
generating a clock signal operating at said desired frequency;
generating a periodic signal operating at said desired frequency with very small duty cycle;
generating a disturbance signal with substantially equivalent period and duty cycle of said periodic signal, and
injecting said disturbance signal into a feedback network of said hysteretic power converter,
whereby synchronization between said desired frequency of said clock signal and said switching frequency of said hysteretic power converter is obtained with an open loop system.
11. The method of claim 10 wherein said hysteretic power converter is a hysteretic boost power converter.
12. The method of claim 10 , wherein said disturbance signal is a current signal.
13. The method of claim 10 , wherein said disturbance signal is generated by a switch in series to at least one passive component;
wherein said switch is driven by said periodic signal operating at said desired frequency;
wherein said switch is coupled to a positive or a negative terminal of a power source, and to said at least one passive component, and
wherein said at least one passive component is coupled to a node of said feedback network of said hysteretic power converter.
14. The method of claim 10 , wherein said disturbance signal is generated by a current source operated at said desired frequency.
15. The method of claim 10 , wherein said desired frequency is independent from a free running switching frequency of said hysteretic power converter.
16. The method of claim 10 , wherein an amplitude of said disturbance signal is adaptively varied depending on operating conditions of said hysteretic power converter in order to reach an adequate level required to synchronize said hysteretic power converter with minimum adverse effects.
17. The method of claim 10 , wherein a free running frequency of said hysteretic power converter is adjusted to be in locking range of said disturbance signal.
18. The method of claim 10 , wherein said synchronization to said desired frequency occurs only in Continuous Conduction Mode.
19. A hysteretic power converter,
wherein the switching frequency of said hysteretic power converter is synchronized to a desired frequency by means of injection of a disturbance signal into a hysteretic comparator of said hysteretic power converter,
wherein synchronization is obtained with an open loop system, and
wherein said disturbance signal is a periodic signal operating at said desired frequency.
20. A hysteretic power converter,
wherein the switching frequency of said hysteretic power converter is synchronized to a desired frequency by means of injection of a disturbance signal into a voltage reference of said hysteretic power converter,
wherein synchronization is obtained with an open loop system, and
wherein said disturbance signal is a periodic signal operating at said desired frequency.
21. The hysteretic power converter of claim 1 , wherein said hysteretic power converter is a hysteretic buck power converter.
22. The method of claim 10 wherein said hysteretic power converter is a hysteretic buck power converter.