Buck-Boost Converter Timing Control for Low-Power Overcurrent Sensing
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Solution Overview
Problem
Existing DC-DC converters face challenges in accurately detecting overcurrent conditions during low-power operating modes, where the voltage across shunt resistors is very low, making precise measurement difficult.
Innovation Solution
A control module for a switching buck-boost converter that operates in low-power mode by alternating between first and second time periods, using a diode to prevent capacitor discharge and an overcurrent detection circuit that compares the duration of second time periods with a limit duration to indicate overcurrent conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shunt resistor is used to detect overcurrent conditions, then overcurrent detection capability is provided, but measurement precision deteriorates in low-power modes due to very low voltage across the shunt resistor
Solution Approach 1:
The patent changes the detection parameter from voltage measurement (which becomes too small to measure accurately in low-power mode) to time duration measurement. By measuring how long the capacitor takes to discharge during second time periods, the system can accurately detect overcurrent conditions even when operating currents are very low, resolving the measurement precision issue while maintaining overcurrent detection capability
Solution Approach 2:
The patent introduces a capacitor as an intermediary element between the shunt resistor and the detection circuit. The capacitor accumulates charge during first time periods and discharges during second time periods, converting the small voltage signal into a measurable time duration signal, thereby enabling accurate overcurrent detection in low-power modes
2Use of energy by moving object
If the converter operates in low-power mode with reduced current, then power consumption is reduced, but overcurrent detection accuracy deteriorates due to difficulty in measuring very low voltage
Solution Approach 1:
The system changes the measurement parameter from voltage (analog domain) to time duration (digital domain). This allows accurate overcurrent detection in low-power mode because time measurement is not affected by the low voltage levels present when the converter operates at reduced current, thus maintaining both low power consumption and high measurement accuracy
Solution Approach 2:
The patent replaces the analog voltage measurement system with a digital time measurement system. By using a controller to measure the duration of second time periods rather than directly measuring voltage, the system achieves accurate overcurrent detection while operating in low-power mode with reduced current
Data Source
AI summary
A control module is used to control a switching buck-boost converter that includes an inductor, a capacitor, a first top switch and a second top switch, a first bottom switch and a second bottom switch and a diode coupled to the second top switch. The control module controls the switching buck-boost converter so as to alternate: first time periods, in which the second top switch is open and cycles of charge and discharge of the inductor are carried out, during which the inductor is traversed by a current that also passes through the diode and charges the capacitor; and second time periods, in which the first and second top switches are open and the first and second bottom switches are closed so that the current in the inductor recirculates, and the capacitor is discharged by a current that flows in the load.