Paralleled LDO Current Sharing With Lossless Offset Compensation
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Solution Overview
Problem
High-performance mixed-signal products face challenges in achieving ultralow noise and high load current requirements, as paralleled LDO regulators often suffer from output voltage mismatches due to tolerance errors, leading to load current unbalance and potential current-limit protection issues, while existing current sharing methods either degrade load regulation or consume additional power.
Innovation Solution
The solution involves paralleling monolithic embedded LDO power rails with lossless current sensing to maintain accurate current sharing and balancing between LDOs, using an offset generator to cancel DC offsets by comparing master and slave channel voltages and adding offset voltages between input reference and output regulated voltages, without additional power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If paralleled LDO regulators are used to increase load current capacity, then the load current capability is improved, but output voltage mismatches due to tolerance errors cause load current unbalance and potential current-limit protection issues
Solution Approach 1:
The patent implements a feedback mechanism where current sensing resistors monitor the output current of each LDO regulator, and the sensed voltages are fed back to differential amplifiers. These amplifiers compare the sensed voltages and generate correction signals that are applied to the error amplifiers of each LDO, dynamically adjusting the output voltages to compensate for manufacturing tolerances and achieve balanced current sharing.
Solution Approach 2:
The patent dynamically changes the output voltage parameter of each LDO regulator based on the sensed current conditions. By adjusting the voltage output of individual LDOs through the feedback mechanism, the system compensates for fixed manufacturing tolerances and achieves optimal current distribution across the paralleled regulators.
2Manufacturing precision
If existing current sharing methods are used to balance load current, then current unbalance is reduced, but load regulation degrades or additional power is consumed
Solution Approach 1:
The patent employs lossless current sensing techniques where the current sensing is achieved without introducing additional power loss to the main power path. The sensing resistors are placed in the feedback path rather than the main current path, allowing the system to sense and balance current automatically without consuming additional power from the regulated output.
Solution Approach 2:
The patent introduces differential amplifiers as intermediary components that compare the sensed voltages from current sensing resistors and generate appropriate correction signals. These amplifiers act as mediators between the current sensing stage and the LDO control stages, enabling precise current balancing without directly affecting the main power flow or consuming significant power.
Data Source
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AI summary
The subject disclosure includes paralleling of monolithic embedded low drop-out (LDO) linear regulator power rails to provide additional load current, while maintaining accurate current sharing and balancing between the paralleled LDOs without additional power consumption for different load current requirements. Lossless current sensing is used to sense the current for each channel. An offset generator compares the voltages for a master channel and one or more slave channels, and generates an offset voltage according to the sensed error. The offset voltage is added between an input reference voltage and an output regulated voltage to cancel the offset of each channel, so the current of each channel is substantially the same. The lossless current sensing can be realized with equivalent series resistance compensation or current limit sensing. The offset generator can be realized with a resistor and current mirror topology or an input pair added to an error amplifier input.