Abstract: A switch mode power supply includes a PWM controller, a voltage converter, an output detector and a communicator. The PWM controller is to receive an actuation signal, and generates a PWM signal based on the actuation signal. The voltage converter is to receive the PWM signal and an external voltage, and converts, based on the PWM signal, the external voltage into first and second output voltages. The output detector is to receive the first and second output voltages, and generates an enable signal based on a target voltage value and a magnitude difference between the first and second output voltages. The communicator is to receive the enable signal, and generates the actuation signal corresponding to the enable signal.

Abstract: A charge and power supply circuit includes: a first switch coupled between a first node and a positive terminal of a battery; a second switch coupled between a USB connector and one of the first node and a second node; a third switch coupled to a load in series between the first and second nodes; and a control unit controlling the switches. In a USB charge mode, an input voltage from the USB connector is permitted to charge the battery via the conducting first and second switches. In a battery supply mode, the battery is permitted to supply a battery voltage to the load via the conducting first and third switches. In a USB supply mode, the input voltage is permitted to be supplied to the load via the conducting second and third switches.

Abstract: A voltage stabilizer receives a direct-current (DC) input voltage, and includes four resistors, two transistors, and a diode that cooperatively provide a stable DC output voltage. The voltage stabilizer is configured such that the diode does not directly receive the DC input voltage and does not conduct all the time, so as to reduce power consumption.