Boost Converter Body Switching for Leakage Reduction
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Solution Overview
Problem
Boost converter circuits in battery-powered devices face challenges in controlling shutdown current leakage and efficiency due to large area occupation by pMOS devices and increased switching loss, as well as shutdown current associated with voltage sensing and power consumption by amplifier/comparator circuits.
Innovation Solution
The proposed circuit includes a boost converter with a rectification transistor, a first transistor coupled between the input and body terminal, and a second transistor between the body and output node, utilizing a softstart circuit and drive circuit to control transistor actuation during load and pulse drive phases, and a body control circuit to manage body diodes for reverse biasing, thereby minimizing leakage current and area occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pMOS devices are used for rectification in boost converter, then the device can handle high voltage and current, but the area occupation on integrated circuit increases and shutdown current leakage occurs
Solution Approach 1:
The patent segments the rectification function by using separate nMOS transistors (first and second transistors) with their body terminals connected to different voltage potentials. This segmentation allows each transistor to be optimized for specific voltage ranges, reducing the area required compared to using a single large pMOS device while maintaining the ability to handle high voltage and current.
2Reliability
If pMOS devices are used for rectification, then the converter can operate at high voltages, but shutdown current leakage increases
Solution Approach 1:
The patent changes the voltage parameter at the body terminal of the rectification transistors by connecting them to different voltage potentials (first voltage potential for the first transistor, second voltage potential for the second transistor). This parameter change enables the nMOS transistors to maintain proper off-state characteristics during shutdown, preventing leakage current while still allowing high voltage operation during normal operation.
3Reliability
If voltage sensing circuits and amplifier/comparator circuits are added to control the boost converter, then the converter can regulate output voltage, but shutdown current and power consumption increase
Solution Approach 1:
The patent implements a self-service control mechanism where the body terminals of the rectification transistors are automatically connected to appropriate voltage potentials based on the operating state. This eliminates the need for external voltage sensing circuits, amplifier/comparator circuits, and associated control logic, thereby achieving voltage regulation without the shutdown current and power consumption penalties of traditional control circuits.
4Ease of operation
If body terminals of rectification transistors are connected to fixed voltage potentials, then the transistor operation is simplified, but the ability to minimize leakage current during shutdown is reduced
Solution Approach 1:
The patent implements dynamic body terminal voltage assignment where the voltage potential at the body terminals changes based on the operating state. During normal operation, the body terminals are connected to appropriate potentials for optimal rectification. During shutdown, the body terminals are dynamically reconfigured to minimize leakage current, achieving both operational simplicity and leakage reduction through state-dependent configuration.
Data Source
AI summary
A first softstart signal indicates operation in a load phase for a boost rectifier and a second softstart signal indicates operation in a pulse drive phase which follows the load phase. A rectification transistor is actuated for the duration of the load phase in response to the first softstart circuit to generate a rising output voltage. The rectification transistor is further repeatedly actuated during the pulse drive phase in response to the second softstart circuit to generate a boosted output voltage. A first transistor coupled between a first conduction terminal and a body terminal of the rectification transistor is actuated, and a second transistor coupled between the body terminal and a second conduction terminal of the rectification transistor is deactuated, during the load phase. The first transistor is deactuated, and the second transistor is actuated, during the pulse drive phase.