Bandgap Voltage Reference Buffer with Feed-Forward Capacitor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Low current buffer designs for bandgap voltage references face a conflict between fast start-up and low current consumption, leading to slower start-up times, which is a challenge in applications like USB type-C where rapid voltage bus detection is required within a tight time budget.
Innovation Solution
Incorporating a feed-forward capacitor into the bandgap voltage reference path, which has no impact during normal conditions but significantly improves power-up time by acting like a high current buffer during start-up, and using a bypass circuit with a transistor to manage series resistance, allowing the buffer to operate efficiently like a high current buffer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low current buffer is used in the bandgap voltage reference path, then current consumption is reduced, but start-up time increases significantly
Solution Approach 1:
A feed-forward capacitor is added to the buffer circuit to pre-charge the output capacitor during start-up. This preliminary action allows the capacitor to charge faster before the normal low-current operation begins, thus reducing start-up time without increasing steady-state current consumption.
Solution Approach 2:
The buffer circuit parameters are changed by adding a feed-forward capacitor that alters the charging behavior during transient start-up conditions. This parameter modification enables the buffer to exhibit high-current-like behavior during start-up while maintaining low-current operation during normal conditions.
2Loss of time
If a high current buffer is used to reduce start-up time, then start-up speed improves, but current consumption increases
Solution Approach 1:
The buffer operates in two distinct phases: a high-current phase during start-up (when the feed-forward capacitor charges the output capacitor quickly), and a low-current phase during normal operation. This periodic action allows the system to achieve fast start-up without sustaining high current consumption.
Solution Approach 2:
The feed-forward capacitor acts as an intermediary element that enables fast charging during start-up by providing an additional current path. This intermediary component allows the low-current buffer to temporarily behave like a high-current buffer without requiring a high-current buffer design.
3Productivity
If a bypass circuit with transistor is added to manage series resistance, then buffer efficiency improves, but device complexity increases
Solution Approach 1:
The bypass circuit uses a transistor that dynamically switches based on the buffer output voltage. When the output exceeds the transistor's threshold voltage, the transistor turns on to bypass the series resistor, optimizing performance. This dynamic behavior improves buffer efficiency without requiring complex control circuits.
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
This approach improves the start-up time of a low current buffer by more than ten times compared to traditional designs, enabling it to perform like a high current buffer while maintaining low current consumption, thus meeting the demands of fast start-up in applications like USB type-C.
Implementation Method 1
a capacitor in parallel with the buffer circuit configured to increase a current rise time of the buffer
Implementation Method 2
A bypass circuit may include a first transistor configured to allow the resistor to pass a series current when output of the buffer circuit exceeds a threshold voltage of the first transistor
Data Source
AI summary
A reference voltage circuit with current buffer including a low voltage reference to output a low voltage, a first resistor-capacitor (RC) filter to filter the low voltage, a buffer circuit to output a current to be used by a load, a second RC filter associated with the load, and a capacitor in parallel with the buffer circuit configured to increase a rise time of the buffer.