Back-to-Back Transistor Power Supply for Precise Bidirectional Current Control
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Solution Overview
Problem
Existing power supply circuits, particularly switching regulators, face challenges in efficiently managing current flow between batteries and power supply rails, especially during varying charging and discharging phases, requiring accurate gate voltage regulation to accommodate different use cases.
Innovation Solution
A power supply circuit with back-to-back transistors and independent gate control circuits and current sense circuits is employed to regulate the gate voltages of the transistors, allowing for accurate current management during different charging and discharging phases, including linear charging and soft start scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current sense circuit is used for back-to-back transistors, then device complexity is reduced, but current management accuracy deteriorates during different charging and discharging phases
Solution Approach 1:
The current sense circuit is segmented into two separate circuits: a first current sense circuit coupled to the first transistor and a second current sense circuit coupled to the second transistor. This segmentation allows independent and accurate sensing of currents flowing through each transistor during different operating phases (charging vs. discharging), resolving the contradiction between device simplicity and measurement accuracy.
2Measurement precision
If separate gate control circuits are used for back-to-back transistors, then current flow control accuracy is improved, but device complexity increases
Solution Approach 1:
The gate control function is segmented into separate control circuits for each transistor. The first gate control circuit independently controls the gate voltage of the first transistor, while the second gate control circuit independently controls the gate voltage of the second transistor. This enables precise control of current flow direction and magnitude during different phases without excessive complexity.
Solution Approach 2:
Each transistor is provided with localized gate control and current sensing specifically tailored to its operational role. The first transistor's gate and current sense circuit are optimized for one phase of operation, while the second transistor's components are optimized for the opposite phase, achieving local optimization of control accuracy.
3Adaptability or versatility
If back-to-back transistors are used for bidirectional current control, then adaptability to different charging phases is improved, but device complexity increases
Solution Approach 1:
The back-to-back transistor configuration provides dynamic adaptability, where the first transistor conducts during charging phases and the second transistor conducts during discharging phases. The separate gate control circuits dynamically adjust the conduction state of each transistor based on the operational phase, enabling the system to adapt to different charging and discharging conditions.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques and apparatus for supplying power, including battery charging. One example power supply circuit generally includes a switching regulator including an output node coupled to a power supply node, a battery node for coupling to a battery, a first transistor including a drain coupled to the power supply node, a second transistor including a source coupled to a source of the first transistor and a drain coupled to the battery node, a first current sense circuit coupled to the drain of the first transistor, and a second current sense circuit coupled to the drain of the second transistor.