Switch-mode power supply, charging current source and associated method

摘要

A switch-mode power supply includes a converter, a controller and a charging current. The charging current includes a logic circuit, a first current source and a second current source, to generate a charging current proportional to an input voltage of the switch-mode power supply, and also to generate a logic control signal indicative of either of two operation modes.

主权项

1. A switch-mode power supply comprising a converter, a controller and a charging current source, wherein the switch-mode power supply is configured to convert an input voltage to an output voltage, and wherein the charging current source comprises:
a multi-functional pin, coupled to the input voltage or a system reference ground via a first resistor, wherein the multi-functional pin outputs a frequency signal, and an initial value of the frequency signal is generated according to the input voltage or a zero voltage on the system reference ground; a logic circuit coupled to the multi-functional pin, wherein the logic circuit generates a logic control signal according to the initial value of the frequency signal and an enable signal, and wherein the logic control signal is coupled to the controller configured to indicate either of two operation modes of the controller; a first current source coupled to the logic circuit and the multi-functional pin, wherein the first current source generates a first output current according to the frequency signal, the enable signal and the logic control signal; a second current source coupled to the logic circuit and the multi-functional pin, wherein the second current source generates a second output current according to the frequency signal, the enable signal and the logic control signal; and wherein the first output current is incorporated with the second output current to comprise a charging current provided to the controller, wherein the charging current is proportional to the input voltage.