Dual-Input Pair Voltage Regulator for Soft-Start and Inrush Control
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Solution Overview
Problem
Implementing soft-start functionality in voltage regulators, particularly track regulators, is challenging due to the limitations of n-channel transistors, which cannot swing low input voltages, making it difficult to control inrush currents and overshoot voltages during startup.
Innovation Solution
A voltage regulator design that includes a soft-start circuit with p-type transistors and an error amplifier with n-type transistors, using control logic to gradually increase the output voltage during the soft-start mode and maintain it during normal-operation mode, while also incorporating a track regulator with operational amplifiers of opposite transistor types to effectively manage voltage transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If n-channel transistors are used in the error amplifier, then the regulator can provide stable voltage regulation, but the input voltage cannot swing low enough to enable soft-start control during startup
Solution Approach 1:
The patent divides the error amplifier into two separate amplifiers: a first error amplifier using p-channel transistors for soft-start control and a second error amplifier using n-channel transistors for normal voltage regulation. This segmentation allows each amplifier to operate in its optimal voltage range without compromising the other function.
Solution Approach 2:
The patent introduces a third amplifier (using n-channel transistors) as an intermediary to control the enable signal that gates the output of the first amplifier. This intermediary allows the n-channel based control logic to interface with the p-channel based soft-start amplifier, resolving the conflict between the two transistor types.
2Object-affected harmful factors
If soft-start circuitry is added to control startup voltage, then inrush currents and overshoot can be minimized, but the device complexity increases
Solution Approach 1:
The patent merges the soft-start control functionality with the existing error amplifier structure by using the third amplifier's output to control the enable signal for the first amplifier. This integration approach incorporates soft-start capability into the existing voltage regulation architecture rather than adding completely separate control circuitry.
3Adaptability or versatility
If track regulator is used to mirror voltage output, then a second voltage supply can be created, but soft-start control becomes more difficult due to additional constraints
Solution Approach 1:
The patent makes the first error amplifier (with p-channel transistors) serve multiple functions: it acts as the error amplifier for the track regulator during normal operation and as the soft-start control amplifier during startup. The enable signal mechanism allows this single amplifier to fulfill both roles, simplifying the overall design.
Data Source
AI summary
A voltage regulator includes two input pairs of opposite type transistors, p-type and n-type, to provide a soft-start functionality for gradually increasing the voltage regulator's output voltage from zero, or a voltage below the thresholds of the n-type transistors, to an operational voltage. The voltage regulator operates in a soft-start mode during which a variable input voltage signal is ramped up to allow the output voltage to reach the operational voltage, and a normal-operation mode during which the operational voltage is maintained.