Noise-free control circuit for switching converter and associated control method
AssigneeChengdu Monolithic Power Systems Co., Ltd.
InventorLei Li
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Abstract
Noise-free control circuit and control method for a switching converter. The noise-free control circuit has a timer used to set a noise-free frequency threshed. When the switching frequency of the switching converter is decreased to the noise-free frequency threshold, the switching frequency of the switching converter is limited to the noise-free frequency threshold. The noise-free frequency threshold is higher than a maximum audible frequency of an audio noise.
Claims20
A noise-free control circuit for a switching converter having a high-side switch and a low-side switch, comprising:
- a timer, configured to generate a clock signal having a frequency used as a noise-free frequency threshold;
- a zero-cross detection circuit, configured to sense an inductor current signal flowing through an output inductor of the switching converter, and further configured to receive a feedback signal to generate a noise-free current threshold, and further configured to compare the inductor current signal with the noise-free current threshold to generate a zero-cross signal;
- and
- a frequency controller, configured to receive the feedback signal, the zero-cross signal and the clock signal to generate a high-side control signal and a low-side control signal to respectively control the high-side switch and the low-side switch on and off in a complementary manner, wherein when the switching frequency of the switching converter is decreased to the noise-free frequency threshold, the frequency controller is configured to limit the switching frequency to the noise-free frequency threshold based on the clock signal, and wherein when the inductor current signal is reversely increased to the noise-free current threshold, the frequency controller is configured to turn the low-side switch off based on the zero-cross signal.
A noise-free switching converter, comprising:
- a switching circuit, comprising a high-side switch, a low-side switch and an output inductor, wherein an input voltage signal is converted to an output voltage signal by switching the high-side switch and the low-side switch on and off in a complementary manner;
- a feedback circuit, coupled to the switching circuit to receive the output voltage signal to generate a feedback signal;
- and
- a control circuit, configured to receive the feedback signal to generate a high-side control signal and a low-side control signal to respectively control the high-side switch and the low-side switch, and further configured to generate a noise-free current threshold based on the feedback signal, wherein when the switching frequency of the switching converter is decreased to a noise-free frequency threshold, the control circuit is configured to limit the switching frequency to the noise-free frequency threshold, and wherein when an inductor current signal flowing through the output inductor is reversely increased to the noise-free current threshold, the control circuit is configured to turn the low-side switch off.
A noise-free control method for a switching converter having a high-side switch and a low-side switch, comprising:
- determining whether the switching frequency of the switching converter is decreased to a noise-free frequency threshold;
- limiting the switching frequency of the switching converter to the noise-free frequency threshold when the switching frequency of the switching converter is decreased to the noise-free frequency threshold;
- detecting an inductor current signal flowing through an output inductor of the switching converter;
- generating a noise-free current threshold based on a feedback signal of the switching converter;
- determining whether the inductor current signal is reversely increased to the noise-free current threshold;
- and
- turning the low-side switch off when the inductor current signal is reversely increased to the noise-free current threshold.
Dependencies are inferred from the claim text.