Buck-Boost Converter Control for Precise Low-Power Overcurrent Detection
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Solution Overview
Problem
Existing DC-DC converters face challenges in accurately detecting overcurrent conditions during low-power operating modes due to the low voltage across shunt resistors, making it difficult to implement precise overcurrent detection and load protection mechanisms.
Innovation Solution
A control module for a switching buck-boost converter that alternates between time periods to enhance overcurrent detection by monitoring the duration of specific time intervals, using a diode to prevent capacitor discharge and recirculating current through switches, enabling precise overcurrent detection even in low-power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the converter operates in low-power mode with a shunt resistor to detect overcurrent, then power consumption is reduced, but measurement precision deteriorates due to very low voltage across the shunt resistor
Solution Approach 1:
The patent introduces a capacitor as an intermediary element connected in parallel with the shunt resistor. During low-power mode, the capacitor accumulates voltage from the small voltage drop across the shunt resistor over multiple switching cycles, thereby amplifying the measurement signal without increasing instantaneous power consumption. This mediator allows precise overcurrent detection while maintaining low average power consumption.
2Use of energy by moving object
If the converter operates in low-power mode with reduced current, then power consumption is reduced, but reliability deteriorates due to difficulty in detecting overcurrent conditions
Solution Approach 1:
The patent employs periodic sampling and accumulation of voltage across the shunt resistor over multiple switching cycles. By periodically measuring and accumulating the small voltage signals through the capacitor during low-power mode, the system builds up sufficient voltage for reliable overcurrent detection. This periodic action enables reliable protection while maintaining low instantaneous power consumption during normal operation.
3Loss of energy
If the shunt resistor has low resistance to minimize power loss, then energy efficiency is improved, but measurement precision deteriorates due to very low voltage signal
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor during normal operation and low-power mode before an overcurrent event occurs. The capacitor accumulates voltage from the small voltage drop across the low-resistance shunt resistor over time. When an overcurrent condition occurs, the pre-charged capacitor provides a sufficiently large voltage signal for accurate detection, thus enabling the use of low-resistance shunts without sacrificing measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate overcurrent detection and load protection in low-power modes by utilizing time period monitoring and diode-based current recirculation, reducing power consumption and improving detection precision.
Implementation Method 1
a diode coupled to conduction terminals of the second top switch and configured to prevent discharging of the capacitor through the second internal node, when the second top switch is open
Implementation Method 2
the inductor being coupled to the first and second internal nodes... execute cycles of charge and discharge of the inductor, during which the inductor is traversed by a current
Implementation Method 3
the capacitor being coupled to the output node... the capacitor is discharged by a current that flows in the load
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.