Chargers with voltage amplitude modulation

Abstract

Chargers and methods are provided which increase the charging efficiency of the chargers by implementing voltage amplitude modulation (VAM) instead of voltage frequency modulation. The charging voltage amplitude is modulated using feedback from at least one energy storage device that is being charged by the charger, while maintaining a charging voltage frequency constant at a LLC resonance frequency of the charger. A buck/boost configuration may be used to reduce maximal voltage levels and further optimize the charger's design.

1 . A method of increasing a charging efficiency of a charger, the method comprising modulating a charging voltage amplitude using feedback from at least one energy storage device that is being charged by the charger, while maintaining a charging voltage frequency constant at a LLC resonance frequency of the charger. 
     
     
         2 . The method of  claim 1 , further comprising using a buck/boost PFC (power factor correction) unit for enabling charging with voltage amplitude modulation below a maximum input voltage to the charger. 
     
     
         3 . The method of  claim 1 , further comprising implementing a bypass of a PFC unit of the charger when an input voltage to the charger is equal to the modulated voltage. 
     
     
         4 . The method of  claim 1 , wherein the at least one energy storage device comprises at least one fast charging lithium ion battery. 
     
     
         5 . A charger for an energy storage device, comprising a PFC unit configured to implement charging voltage amplitude modulation, while maintaining a charging voltage frequency constant at a LLC resonance frequency of the charger, according to a feedback to the PFC unit from at least one energy storage device that is being charged by the charger. 
     
     
         6 . The charger of  claim 5 , wherein the PFC unit is configured in a buck/boost configuration to enable the charging with voltage amplitude modulation below a maximum input voltage to the charger. 
     
     
         7 . The charger of  claim 6 , configured to charge at least one fast charging lithium ion battery as the at least one energy storage device.