Soft-Start Reference Delay Circuit for Regulator Overshoot Control
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Solution Overview
Problem
Existing soft-start circuits for voltage regulators in System-on-Chips (SoCs) are bulky and costly due to their complexity, leading to overshoot issues during startup that can damage functional circuits.
Innovation Solution
A soft-start circuit comprising a comparator, delay circuit, logic gate, latch, buffer, and minimal components like a resistor, switch, and capacitor, which compares output voltage to a reference voltage, delaying its increase to prevent overshoot, thus reducing the circuit's size and manufacturing cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional soft-start circuit with current sources, switches, unbalanced differential pair of transistors, and differential amplifier is used, then the output voltage overshoot can be mitigated, but the circuit size and manufacturing cost increase
Solution Approach 1:
The patent extracts the essential function of soft-start (delaying reference voltage during startup) from the complex conventional circuit and implements it using only a comparator and a delay circuit. This removes unnecessary components (current sources, unbalanced differential pair, differential amplifier) while retaining the core overshoot mitigation capability.
Solution Approach 2:
The patent changes the reference voltage parameter over time by introducing a delay circuit that provides a delayed version of the reference voltage during startup. This temporal parameter change allows the voltage regulator to start up gradually, preventing overshoot without requiring complex circuitry.
2Reliability
If a conventional soft-start circuit with current sources, switches, unbalanced differential pair of transistors, and differential amplifier is used, then the output voltage overshoot can be mitigated, but the manufacturing cost increases
Solution Approach 1:
The patent extracts the essential function of soft-start from the complex conventional circuit and implements it using only a comparator and a delay circuit. This removal of unnecessary components (current sources, unbalanced differential pair, differential amplifier) directly reduces manufacturing cost while retaining overshoot mitigation.
Solution Approach 2:
The patent replaces expensive, complex components with simpler, cheaper alternatives. The delay circuit using basic RC components and the comparator provide the same soft-start function at a fraction of the manufacturing cost of the conventional approach.
3Speed
If the reference voltage increases at a significant rate during SoC power-up, then the voltage regulator can respond quickly, but the output voltage overshoot increases which can damage functional circuits
Solution Approach 1:
The patent applies preliminary action by delaying the reference voltage signal before it reaches the voltage regulator during startup. The delay circuit pre-processes the reference voltage to ensure it rises gradually, preventing the harmful overshoot effect before it can occur in the output voltage.
Solution Approach 2:
The patent provides beforehand cushioning by introducing a delayed version of the reference voltage that acts as a buffer during startup. This cushioned, delayed signal prevents the sharp rise that would cause overshoot, protecting functional circuits from damage while still allowing the voltage regulator to eventually reach its target voltage.
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
The proposed soft-start circuit effectively mitigates output voltage overshoot during startup, reducing the overall size and manufacturing cost of the SoC by using fewer and simpler components compared to conventional designs.
Implementation Method 1
The comparator can be coupled with the voltage regulator, and configured to compare an output voltage and a reference voltage to generate a comparison signal
Implementation Method 2
During a start-up of the voltage regulator, the second reference voltage can be a delayed version of the first reference voltage
Implementation Method 3
The capacitor can be coupled between the resistor and a ground terminal, and configured to output the second reference voltage
Data Source
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AI summary
A soft-start circuit for a voltage regulator includes a comparator and a delay circuit. The comparator compares an output voltage, that is generated by the voltage regulator, and a reference voltage to generate a comparison signal. Further, the delay circuit receives the reference voltage and a control signal that is outputted based on the comparison signal, and outputs and provides another reference voltage to the voltage regulator. During a start-up of the voltage regulator, the reference voltage outputted by the delay circuit is a delayed version of the reference voltage received by the delay circuit. Thus, the soft-start circuit mitigates an overshoot of the output voltage during the start-up. Further, on completion of the start-up, the reference voltage outputted by the delay circuit is equal to the reference voltage received by the delay circuit.