Patent ID: 8214667

Claim:
A central processing unit (CPU) start-up circuit for controlling a CPU of a portable electronic device, comprising: a power management unit (PMU) connected to the CPU; an awaking circuit connected to the CPU; a main power supply connected to the CPU, the PMU and the awaking circuit; and a subsidiary power supply connected to the PMU and the awaking circuit; wherein the main power supply provides a first working electric power to the CPU, and the subsidiary power supply provides a second working electric power to the PMU and the awaking circuit; the PMU detects a status of the main power supply and generates a status signal (SS) according to the status of the main power supply detected by the PMU, the awaking circuit detects the status of the main power supply and generates a waking signal (WS) according to the status of the main power supply detected by the awaking circuit, and the SS and the WS are both transmitted to the CPU to cooperatively control the CPU to be switched on and switched off, wherein each of the SS and the WS has a predetermined high voltage level and a predetermined low voltage level, the CPU is switched on when the SS and the WS are at their high voltage levels respectively, and is switched off when the SS is at the low voltage level of the SS.