Patent ID: 8049478

Claim:
A switching regulator eliminating beat oscillation, comprising: a first transistor, a second transistor, and an inductor connected to a common node, wherein the first and second transistors operate to convert an input voltage to an output voltage; a comparator comparing a voltage signal with a saw tooth wave to generate a control signal controlling at least one of the first and second transistors; a feedback loop obtaining a feedback signal from the output voltage and generating the voltage signal according to the feedback signal; and an inductorless filter circuit located in the feedback loop for filtering frequencies in the vicinity of a frequency of the saw tooth wave but not filtering other high frequencies; and wherein the inductorless filter circuit includes an inductor equivalent circuit that comprising: a first resistor, a second resistor, a third resistor, a capacitor, and a fourth resistor connected in series sequentially between the input of the inductor equivalent circuit and ground; a first operational amplifier comparing a voltage at the input of the inductor equivalent circuit with a voltage at a node between the second and third resistors, the output of the first operational amplifier being coupled to a node between the third resistor and the capacitor; and a second operational amplifier comparing the voltage at the node between the second and third resistors and a voltage at the node between the capacitor and the fourth resistor, the output of the first operational amplifier being coupled to a node between the first and second resistors.