US Patent 7403232 Intelligent power management system

An intelligent power management system is particularly applicable to accessory devices that can be coupled to a basic device to provide the basic device with an enhanced feature. The accessory device includes a control processor and a power supply unit, wherein the power supply unit supplies electrical energy to the control processor in response to a control signal received from the basic device. The power supply unit includes a power management circuit that maintains the electrical energy supplied to the control processor during fluctuations of the control signal.