Dual-Mode Current Sensing for Multi-Phase DRMOS Load Balancing
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Solution Overview
Problem
Existing current sensing techniques in high power converter circuits, particularly in DRMOS modules, struggle with accurately measuring and balancing current between phases to prevent overheating and overloading, while also being cost-effective and compact.
Innovation Solution
A dual mode current sensing circuit (DMCSC) integrated with a controller in a multi-phase power supply system, which operates in data collection and sensing modes to measure current imbalance, compensate for gain errors, and regulate output current, all within a compact 5 mm×5 mm package, using direct current resistance and active resistance sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional current sensing techniques (shunt resistors, current transformers, Hall-effect sensors) are used in DRMOS modules, then current measurement accuracy is improved, but device size, cost, and complexity increase
Solution Approach 1:
The patent combines the current sensing function with the existing low-side driver circuit by utilizing the source follower transistor's inherent resistance characteristics. This integration eliminates the need for separate sensing components (shunt resistors, current transformers, or Hall-effect sensors), thereby reducing device complexity while maintaining measurement capability through digital compensation techniques.
Solution Approach 2:
The patent replaces traditional electrical sensing mechanisms (physical resistors, magnetic sensors) with a digital sensing approach. By measuring voltage drops across the low-side driver transistor and using digital signal processing to compensate for resistance variations, the system substitutes analog hardware sensing with a digitally-based measurement method, reducing component count and complexity.
2Measurement precision
If multiple current sensing circuits are implemented for each phase, then current balancing precision is improved, but component count and cost increase
Solution Approach 1:
The low-side driver circuit serves multiple functions simultaneously: it drives the power switch and provides current sensing capability. The source follower transistor's resistance is utilized for sensing purposes, allowing the same circuit component to perform both switching control and current measurement, thereby eliminating the need for separate sensing circuits in each phase.
Solution Approach 2:
The system uses the inherent electrical characteristics of the low-side driver transistor (its source-to-drain resistance) for current sensing purposes. The circuit essentially senses current through its own operational parameters, eliminating the need for external sensing components and reducing overall component count while maintaining precision through digital compensation.
3Stability of the object's composition
If large ground plates are integrated for current sensing, then measurement stability is improved, but package size increases
Solution Approach 1:
The patent replaces the need for large physical ground plates with a digital reference voltage approach. By using a stable reference voltage and digital signal processing to establish the measurement baseline, the system achieves measurement stability without requiring extensive physical grounding structures, thereby reducing package area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively balances current between multiple power phases with a maximum 5% difference, preventing overcurrent and overheating, while reducing component count and size, and improving thermal management.
Implementation Method 1
the DMCSC may generate a current balancing input to the controller based on a direct current resistance of the current sensing circuit and an active resistance in the low side driver circuit
Data Source
AI summary
Apparatus and associated methods relate to circuit load balancing in a multi-phase power supply system (MPPSS). In an illustrative example, a MPPSS may include multiple power phases, each driven by a corresponding power phase driver (e.g., a DRMOS). A controller, for example, may include multiple current balancing inputs, each corresponding to one of the power phases. For example, the current balancing inputs may be generated by a dual mode current sensing circuit (DMCSC). For example, in a data collection mode of a power phase, the DMCSC may store information of an output current. In a sensing mode of the power phase, the DMCSC may generate a current balancing input to the controller based on a direct current resistance of the current sensing circuit and an active resistance in the low side driver circuit. Various embodiments may advantageously measure current imbalance in a cost effective manner.