Buck-Boost DC/DC Converter DCM Control Without Zero-Current Detection
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Solution Overview
Problem
Buck-boost DC/DC converters operating in discontinuous current mode require a zero-current detection circuit, which increases complexity and cost.
Innovation Solution
A buck-boost DC/DC converter design that operates in discontinuous current mode without a zero-current detection circuit by using a sensing circuit to estimate the duration of a switching period based on a sampling value of the input current, allowing control circuits to manage switch operations effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a zero-current detection circuit is used to detect when inductor current reaches zero in DCM mode, then the converter can operate correctly in discontinuous current mode, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the zero-current detection function from a separate detection circuit and integrates it into the existing current sensing circuit. The sensing circuit that already measures inductor current for control purposes is modified to also detect when current reaches zero, eliminating the need for a dedicated zero-current detection circuit and its associated components.
Solution Approach 2:
The current sensing circuit is given dual functionality: it continues to provide current measurement for normal control operations while simultaneously detecting the zero-current condition required for DCM mode operation. This multi-functionality eliminates the need for separate detection circuitry.
2Reliability
If a zero-current detection circuit is used to detect when inductor current reaches zero, then accurate DCM control is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent removes the need for expensive dedicated zero-current detection components by extracting this detection capability from separate circuitry and incorporating it into the existing sensing infrastructure, thereby reducing component count and manufacturing cost.
Solution Approach 2:
The patent uses the existing current sensing circuitry that is already present in the converter design, rather than adding expensive dedicated detection components. By repurposing existing inexpensive sensing elements, the solution achieves zero-current detection without increasing manufacturing cost.
3Device complexity
If the converter operates in DCM mode without zero-current detection, then circuit complexity is reduced, but the ability to accurately control switching timing deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the inductor current through the sensing circuit and using this information to determine when the current reaches zero. This feedback mechanism ensures accurate detection of the zero-current condition and precise control of switching timing without requiring complex additional circuitry.
Solution Approach 2:
The patent replaces complex mechanical or dedicated electronic zero-current detection mechanisms with a simplified sensing approach that uses electrical measurement of current magnitude. The control circuits process the sensed current signal to accurately determine zero-crossing points, substituting complex detection hardware with simpler signal processing.
Data Source
AI summary
The present disclosure provides sensing a peak current and estimating a turn-off time of a switch using the peak to perform a discontinuous current mode (DCM) operation. According to the present disclosure, the buck-boost DC/DC converter includes: a first control circuit configured to build up a current, input through an input node, in an inductor during a first time period of a switching period; a sensing circuit configured to sense a current input through the input node to generate a sampling value for estimating a duration of a second time period; and a second control circuit configured to receive the sampling value from the sensing circuit and to output the current built up in the inductor through an output side during the second time period estimated based on the sampling value.