Configurable M-Level Buck Converter for Efficient Battery Charging
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Solution Overview
Problem
Conventional synchronous buck-based battery charging circuits face limitations in harnessing high input power due to maximum efficiency constraints, leading to inefficiencies in switch resistance and switching charge losses.
Innovation Solution
The proposed solution involves an M-level buck converter with 2×N×(M−1) number of transistors, where N is greater than one, allowing the converter to operate in two modes: high-current and low-current charge modes. In the high-current mode, all transistors are switched ON and OFF, while in the low-current mode, a subset of transistors are switched ON and OFF, and the remaining transistors are fully deactivated.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional synchronous buck-based charging circuit is used, then the circuit structure is simple, but the maximum efficiency is constrained and high input power cannot be fully harnessed
Solution Approach 1:
The switching element is designed to perform multiple functions by incorporating both a first transistor and a second transistor that can be activated based on operating conditions. In high-current mode, both transistors are active to handle high power with low on-resistance. In low-current mode, only the first transistor is active to minimize capacitance. This multi-functionality allows the same switching element to optimize for both high-power and low-power operations, overcoming the efficiency constraints of conventional single-transistor designs.
Solution Approach 2:
The system changes its effective parameters (on-resistance and input capacitance) by dynamically activating or deactivating the second transistor. When the second transistor is activated in high-current mode, the effective on-resistance decreases to reduce conduction losses. When deactivated in low-current mode, the effective input capacitance decreases to reduce switching charge losses. This parameter changes approach allows the circuit to maintain high efficiency across different operating conditions without requiring a completely different circuit topology.
Data Source
AI summary
According to an embodiment, a method of operating an M-level buck converter in a battery charging circuit is provided. The M-level buck converter includes 2×N×(M−1) number of transistors. M and N are greater than one. The method includes operating the M-level buck converter in a first mode of the battery charging circuit corresponding to a high-current charge mode. The method further includes operating the M-level buck converter in a second mode of the battery charging circuit corresponding to a low-current charge mode. In the first mode, 2×N×(M−1) number of transistors are switched ON and OFF. In the second mode, 2×(M−1) number of transistors are switched ON and OFF and 2×N×(M−1)−2×(M−1) number of transistors are fully deactivated.