Uninterrupted Current Sense in DC-DC Converters
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Solution Overview
Problem
Current DC-DC converters experience current sense staggering due to the non-overlap period between high-side and low-side power switches, causing discontinuities in current sensing signals which affect the control and efficiency of the power transistors.
Innovation Solution
Implementing uninterrupted current sensing by using a sample-and-hold circuit to copy and adjust current sense signals during non-overlap periods, ensuring continuous and accurate current sensing through both high-side and low-side power transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-overlap time is used between power transistors to prevent shoot-through, then transistor safety is improved, but current sense signal continuity deteriorates
Solution Approach 1:
A current sense copy circuit acts as an intermediary to provide continuous current sensing information during the non-overlap period. When the low-side transistor is OFF, the copy circuit generates a copy of the high-side current sense signal, and vice versa, ensuring uninterrupted current information for the control circuit while maintaining the necessary non-overlap time for transistor safety
Solution Approach 2:
The patent creates a copy of the current sense signal from one transistor channel and uses it during the non-overlap period when the other channel is active. This copying mechanism allows the control circuit to maintain continuous current information without requiring both transistors to be simultaneously monitored, thus preserving signal continuity while allowing non-overlap operation
2Loss of energy
If current sensor is de-biased during non-overlap period, then power loss is reduced, but sensing response time increases
Solution Approach 1:
Instead of keeping the inactive current sensor powered and ready (which would cause power loss), the system copies the current sense signal from the active sensor and uses it during the non-overlap period. This eliminates the need to power the inactive sensor while still providing continuous current information, reducing power loss without sacrificing sensing effectiveness
Solution Approach 2:
The active current sensor serves dual purposes: it senses current for its own transistor channel and simultaneously provides copy signals to represent the current state during the non-overlap period. This self-service approach allows one sensor to fulfill both sensing needs, eliminating the requirement for a second powered sensor during idle periods
Data Source
AI summary
A method includes driving a first transistor to conduct a first current into an inductor when conductive and driving a second transistor to conduct a second current into the inductor when conductive. A first sense current is generated in response to the first current and a copy of the second current. A second sense current is generated in response to the second current and a copy of the first current. The first sense current is adjusted in response to the copy of the second current when the first transistor is nonconductive. The second sense current is adjusted in response to the copy of the first current when the second transistor is nonconductive. On times of the first and second transistors are controlled in response to a sum of the first and second sense currents.