Power Gate Replica Current Sensing for Stable Digital Voltage Regulation
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Solution Overview
Problem
Digitally controlled power gates in voltage regulators face challenges with loop stability, transistor reliability, self-heat issues, and inaccurate current sensing due to process variations, leading to unbounded transient current steps and difficulty in measuring power gate current.
Innovation Solution
A power gate replica circuit is used to measure and regulate current per branch, employing a feedback loop to maintain stable current delivery, improve loop stability, and reduce self-heat, while using a centralized amplifier to sense and convert the current into a digital code for accurate load current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If digitally controlled power gates are switched from OFF to fully ON, then power delivery is improved, but loop stability deteriorates and transient current steps become unbounded
Solution Approach 1:
The patent implements dynamic current limiting that adapts to different operating conditions. The current limit is not fixed but varies based on the power gate's operating state, allowing full power delivery when safe while preventing unbounded transient current steps that would destabilize the loop. This dynamic adjustment resolves the contradiction between maximizing power delivery and maintaining loop stability.
Solution Approach 2:
The patent employs feedback control to monitor the power gate's current and voltage conditions in real-time. This feedback mechanism detects approaching unsafe conditions and adjusts the current limit accordingly, preventing transient current steps that would cause loop instability while still allowing optimal power delivery under normal conditions.
2Power
If power gate current is increased to meet load demands, then power delivery is improved, but transistor self-heat and reliability deteriorate
Solution Approach 1:
The patent applies preliminary anti-action by establishing current limits before transistors reach dangerous temperature levels. The system proactively prevents excessive current that would cause self-heat and reliability issues, rather than reacting after damage occurs. This is achieved through predictive current limiting based on measured voltage drops and inferred current values.
Solution Approach 2:
The patent changes the operating parameters of power gate transistors by dynamically adjusting current limits based on measured conditions. When voltage drops indicate approaching unsafe current levels, the system modifies the current parameter to prevent self-heat accumulation, thereby maintaining transistor reliability while still meeting load demands within safe operating boundaries.
3Device complexity
If voltage drop across power gate is measured to infer current, then current sensing is simplified, but measurement accuracy deteriorates due to small signal magnitude
Solution Approach 1:
The patent merges the voltage measurement function with the existing power gate control circuitry. The same circuit that controls the power gate also measures its voltage drop, eliminating the need for separate sensing circuitry. This integration maintains simplicity while improving accuracy through coordinated measurement and control.
Solution Approach 2:
The patent makes the power gate control circuitry multi-functional by having it perform both control and measurement functions. The circuit that drives the power gate also measures its voltage drop to infer current, providing dual functionality without additional complexity. This universal approach simplifies the overall system while maintaining measurement accuracy.
Data Source
AI summary
A reduced-size replica of power gate transistors may be used within a closed-loop voltage regulator to measure the average current delivered by the transistors in the non-replica power gate. The measured current is compared against a known reference current, and a feedback loop is used to modify the gate bias of the power gate and replica power gate transistors. An improved current sensing power gate replica solution may include measuring current from a small replica of the power gate and extrapolating the total current by digitally multiplying the replica current by the ratio of the size of the enabled power gates to the size of the replicas. The current through the replicas, which substantially matches the current in equivalent power gate devices, may be collected on an analog bus and conducted across a known resistor to generate a voltage that determines an estimated current of the power gate devices.