Voltage Regulator Feedforward Transient Rejection

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Solution Overview

Problem

Existing voltage regulators face challenges in maintaining a constant output voltage during sudden changes in current demand and are susceptible to noise and transients in the power supply, particularly in automotive environments, which can lead to instability and potential damage from short circuits or overload conditions.

Innovation Solution

A voltage regulator circuit utilizing a PMOS pass device with an error amplifier and a current mirror configuration, coupled with a capacitor for frequency compensation, prevents the output voltage from rising during supply transients by maintaining current flow through the output stage, thus enhancing power supply rejection without requiring external components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If a large load capacitor is used to meet immediate current demand, then the ability to respond to load transients is improved, but the power supply rejection ratio deteriorates due to coupling of supply line noise and transients

Engineering Contradiction:

Improveresponse speed to load transientsVSAvoidpower supply rejection ratio

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

A feedforward path is introduced as an intermediary mechanism that detects power supply transients before they affect the output. The feedforward path includes a transistor whose gate receives the power supply voltage, allowing it to anticipate and counteract supply variations before they couple into the output through the load capacitor.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The feedforward path performs preliminary action by detecting power supply transients in advance and generating a compensating signal before the transients can affect the output voltage. This allows the regulator to preemptively counteract supply variations rather than reacting after they have already coupled into the output.

Inventive Principle:

Principle #10Preliminary action

2Speed

If the control loop is designed for high speed response, then the ability to meet sudden current demand is improved, but stability deteriorates due to the tradeoff between stability and speed of response

Engineering Contradiction:

Improvespeed of responseVSAvoidcontrol loop stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The control system is segmented into two independent paths: a feedback path that ensures stability by comparing output voltage to reference voltage, and a feedforward path that provides high-speed response by directly sensing power supply transients. This segmentation allows each path to be optimized for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The feedback path continues to provide stable voltage regulation by comparing the output voltage to a reference voltage and adjusting the pass transistor accordingly. This feedback mechanism ensures stability while the feedforward path handles high-speed transient response.

Inventive Principle:

Principle #23Feedback

3Reliability

If the regulator uses a pass transistor to control output voltage, then the ability to maintain constant voltage is improved, but susceptibility to damage from short circuit or overload conditions worsens due to excessive currents

Engineering Contradiction:

Improvevoltage regulation capabilityVSAvoidvulnerability to short circuit and overload damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Overcurrent protection is implemented through preliminary action by detecting excessive current conditions and shutting down the pass transistor before damage can occur. The protection circuit monitors current flow and preemptively disables the regulator when overload or short circuit conditions are detected.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The potential harmful effect of excessive current is converted into a useful protective function. The overcurrent protection circuit uses the presence of excessive current as a signal to trigger shutdown, transforming the harmful condition into a protective mechanism that prevents damage to the pass transistor and other circuit components.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS7907003B2Method for improving power-supply rejection

Publication Date: 2011.03.15 MICROCHIP TECHNOLOGY INC

AI summary

An electronic circuit may comprise an input stage powered by a supply voltage and configured to receive a reference signal. The circuit may further comprise an output stage powered by the supply voltage and coupled to the input stage, and configured to generate an error signal based on: the reference signal, and a feedback signal based on an output signal. The circuit may also include a pass transistor powered by the supply voltage and configured to generate the output signal based on the error signal. A capacitor coupled between the supply voltage and the output stage may increase the current flowing in the output stage, resulting in the output stage conducting current even during a rising edge of the supply voltage, preventing the output signal from reaching the level of the supply voltage during the rising edge of the supply voltage.