Dual-Stage DUT Power Supply Glitchless Current Range Switching
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Solution Overview
Problem
Existing device under test (DUT) power supply (DPS) systems face challenges in providing accurate output voltage while sourcing and sinking a wide range of currents, especially under transient conditions and varying capacitive loads, often resulting in glitches and instability during current range switching.
Innovation Solution
The DPS employs a dual-stage current sourcing and sinking architecture with a measure current circuit that remains independent of the forcing function, allowing for glitchless transitions between current ranges without series resistance, thereby maintaining stability and enabling full current delivery across all ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large external capacitances are employed to provide transient currents, then transient response is improved, but stability under capacitive loads deteriorates
Solution Approach 1:
The current output stage is divided into two independent parallel stages: a first current stage for low current ranges and a second current stage for high current ranges. Each stage has its own current source circuit and sense resistor, allowing independent optimization without compromising overall stability or transient response.
2Measurement precision
If current measurement ranges are switched to measure different current levels, then measurement precision is improved, but output voltage stability deteriorates due to glitches
Solution Approach 1:
The measurement system is segmented into multiple independent current stages, each with its own sense resistor optimized for specific current ranges. This allows precise measurement across wide current variations without requiring switching that would cause glitches.
Solution Approach 2:
Both current stages share the same amplifier and output node, allowing a single unified output to serve multiple current measurement functions. The parallel architecture enables the system to measure both low and high currents simultaneously through appropriate stage selection.
3Measurement precision
If series sense resistors are used for current measurement, then measurement precision is improved, but current delivery capability deteriorates due to voltage drops
Solution Approach 1:
The sense resistor function is segmented and distributed to individual current stages rather than using a single series sense resistor. Each stage has its own low-value sense resistor that minimizes voltage drops while maintaining measurement precision for its specific current range.
Solution Approach 2:
The patent uses current mirror circuits to replicate and scale currents for measurement purposes without requiring large series resistance. The measurement is achieved by copying the output current through matched transistors and measuring the copied signal, preserving the original current delivery capability.
4Reliability
If current limiting is implemented to protect the circuit, then reliability is improved, but current delivery capability deteriorates
Solution Approach 1:
Current limiting is segmented and implemented independently in each current stage through its own sense resistor and amplifier control. This allows each stage to self-limit at appropriate levels while the other stage can still deliver full current, maintaining overall system reliability without compromising total current delivery capability.
Data Source
AI summary
A power supply includes a first amplifier, a first current stage, and a second current stage. The first amplifier is configured to set an output voltage equal to a fixed input voltage for supplying to a device. The first current stage is configured to source and sink a first range of first output currents and provide a first measurement current representing a first output current. The second current stage is configured to source and sink a second range of second output currents and provide a second measurement current representing a second output current in response to the first range being exceeded. The first output current and the second output current are summed for supplying to the device. The first measurement current and the second measurement current are summed at a node.