Voltage Regulator Dynamic Overcurrent Threshold for Load Transients
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Solution Overview
Problem
Voltage regulators face a challenge in maintaining output voltage stability during transient load conditions, often requiring a trade-off between transient performance and the reliability of power FETs, as they can sustain peak currents only briefly above their continuous rating.
Innovation Solution
Implementing a voltage regulator circuit with a state machine and comparators to dynamically adjust the overcurrent limit threshold, setting it higher than the continuous current rating initially, then reducing it when an overcurrent state is detected, and increasing it back when the state returns to normal, allowing the regulator to manage peak currents without compromising FET reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the overcurrent limit is set to the continuous current rating to protect FET reliability, then FET reliability is improved, but transient response performance deteriorates due to voltage undershoot
Solution Approach 1:
The patent applies dynamics by making the overcurrent limit threshold adjustable rather than fixed. The controller dynamically changes the overcurrent limit between a first value (higher than continuous rating) during normal operation and a second value (equal to continuous rating) during overcurrent states, allowing the system to adapt to different operating conditions and resolve the contradiction between transient response and FET reliability
Solution Approach 2:
The patent changes the parameter of overcurrent limit threshold from a static value to a dynamic value that switches between two states. This parameter change allows the voltage regulator to achieve better transient response during normal operation while still protecting FETs during sustained overcurrent conditions
2Stability of the object's composition
If the overcurrent limit is set higher than continuous current rating to improve transient response, then transient performance is improved, but FET reliability deteriorates due to sustained peak currents
Solution Approach 1:
The system dynamically adjusts the overcurrent limit based on the detected state. During transient loads, the higher first value allows improved voltage response, while during sustained overcurrent states, the controller switches to the lower second value equal to the continuous rating, preventing FET damage from prolonged peak currents
Solution Approach 2:
The controller uses feedback from the overcurrent state detection to adjust the overcurrent limit. When an overcurrent state is detected, the controller responds by decreasing the limit to the continuous rating, creating a feedback mechanism that protects FETs while allowing flexible transient response
Data Source
AI summary
Described embodiments include a voltage regulator circuit comprising a first comparator having a first comparator input coupled to a waveform input source, a second comparator input coupled to an output voltage terminal and a first comparator output. There is a second comparator having third and fourth comparator inputs and a second comparator output, the third comparator input coupled to a voltage source configured to provide a voltage representing a current limit, and the fourth comparator input coupled to the output voltage terminal. There is also a state machine having a first state machine input coupled to the first comparator output, a second state machine input coupled to the second comparator output and a state machine output, wherein a state of the state machine is determined by the first and second comparator outputs, and the state machine output provides a PWM signal responsive to the state of the state machine.