US Patent 9603388 Electrically heated smoking system comprising at least two units

An electrically heated smoking system is provided, including a secondary unit capable of receiving a smoking article having an aerosol-forming substrate. The secondary unit includes at least one heating element and an interface for connection to a primary power supply, and further includes a secondary power supply and secondary circuitry. The secondary circuitry is arranged to control supply of electrical power from the secondary power supply to the at least one heating element: (a) in a pre-heating mode during which the substrate temperature is increased to an operating temperature; (b) in a smoking mode, during which the substrate temperature is maintained at substantially the operating temperature; and (c) in a charging mode, so that the secondary power supply has sufficient charge to increase the substrate temperature to the operating temperature in the pre-heating mode and to maintain the substrate temperature at substantially the operating temperature during the smoking mode.