Dynamic cancellation circuit applicable to output direct-current offset of buck converter

Abstract

The invention discloses a dynamic cancellation circuit applicable to output direct-current offset of a buck converter and belongs to the technical field of electronic circuits. The dynamic cancellation circuit comprises a ripple generation circuit and a ripple superposition circuit. The dynamic cancellation circuit has the advantages that duty ratio information is added into the ripple generation circuit, voltage at a connection node SW of an upper power tube S1 and a lower power tube S2 is sampled directly to simulate to generate ripples as same as inductive current in phase, and the ripples are superposed on VFB (voltage feedback) to enable the VFB to be equal to preset VREF (voltage reference), so that a PWM (pulse-width modulation) comparator is controlled to overturn normally, system stability is enhanced, the resonance problem caused by output voltage phase lag which results from too small equivalent series resistance of an output capacitor is avoided, output voltage precision of the converter is improved, contradictions between the system stability and the precision of a valley value detection mode under traditional ripple control are overcome, and direct-current offset of output voltage can be dynamically cancelled under different application conditions, namely under different input and output voltages.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and in particular relates to a dynamic elimination circuit for DC offset output of a step-down DC-DC converter based on ripple control with constant turn-on time. Background technique [0002] With the wide application of portable electronic devices, the market demand for power management integrated circuits continues to rise, and step-down (Buck) DC-DC converters are widely used in communications, computers, industrial automation and other fields. Traditional step-down DC-DC converters have three control modes, namely current mode, voltage mode and hysteresis control. The Ripple-based Constant On-time Control scheme (Ripple-based Constant On-time Control) is a type of hysteretic mode control, and is widely used due to its simple control, no need for external compensation, excellent load regulation and efficiency, etc. . [0003] For traditional step-down converters, there is a cert...

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Problems solved by technology

[0003] For the traditional step-down converter, there is a certain compromise in its system performance: the ripple amount superimposed on the positive side of the PWM comparator by the loop is too small, which may cause the decrease of loop stability, and the output jitter of the PWM comparator may cause false triggering and other problems.

If the ripple is too large, the Q value of the system at half the switching frequency will be too low, making the system response slow; and the DC offset introduced by the inherent valley detection mode of the constant turn-on time is too large, which will Under the premise that the buck converter outputs low voltage, it will have a great impact on the system accuracy

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