DC-DC Converter Transient Response Control

Solution Overview

Problem

Conventional DC-DC converters face limitations in achieving high-speed transient response due to restrictions in frequency bandwidth, leading to increased AC loss and reduced efficiency when attempting to suppress overshoot, which necessitates decreasing the inductance of the choke coil and capacitance of the output capacitor.

Innovation Solution

Incorporating a first transistor in parallel with the series circuit and a second transistor in parallel with the output capacitor, allowing for high-speed adjustment of the output voltage by controlling the gate voltages of these transistors, thereby enabling rapid transient response without lowering the efficiency or reducing the parameters of passive components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the frequency bandwidth of the control circuit is increased to improve transient response speed, then the response time is reduced, but the AC loss increases and efficiency decreases

Engineering Contradiction:

Improvetransient response speedVSAvoidAC loss

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent segments the transient response control into two independent parts: (1) a fast response component handled by the parallel transistor circuit that directly adjusts output voltage, and (2) a steady-state component handled by the conventional control circuit. This segmentation allows the fast response function to operate independently without being constrained by the bandwidth limitations of the control circuit, thereby achieving rapid transient response without increasing AC loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The parallel transistor circuit acts as an intermediary between the control signal and the output voltage. When a transient condition occurs, this intermediary circuit rapidly adjusts the output voltage by shunting current through the parallel transistor, bypassing the slow control circuit. This intermediary mechanism achieves fast response without requiring the control circuit to operate at high bandwidth, thus avoiding increased AC loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Speed

If the inductance of the choke coil and capacitance of the output capacitor are decreased to improve transient response, then the response time is reduced, but the ripple increases and efficiency decreases

Engineering Contradiction:

Improvetransient response speedVSAvoidconverter efficiency

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent segments the transient response control into two independent parts: (1) a fast response component handled by the parallel transistor circuit that directly adjusts output voltage, and (2) a steady-state component handled by the conventional control circuit. This segmentation allows the fast response function to operate independently without being constrained by the bandwidth limitations of the control circuit, thereby achieving rapid transient response without increasing AC loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The parallel transistor circuit acts as an intermediary between the control signal and the output voltage. When a transient condition occurs, this intermediary circuit rapidly adjusts the output voltage by shunting current through the parallel transistor, bypassing the slow control circuit. This intermediary mechanism achieves fast response without requiring the control circuit to operate at high bandwidth, thus avoiding increased AC loss.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of time

If the bandwidth of the control circuit is increased to reduce settling time, then the transient response is improved, but the stability of the output voltage deteriorates due to overshoot

Engineering Contradiction:

Improvesettling timeVSAvoidoutput voltage stability

Core Design Contradiction:

Loss of timeVSStability of the object's composition

Solution Approach 1:

The patent segments the transient response control into two independent parts: (1) a fast response component handled by the parallel transistor circuit that directly adjusts output voltage, and (2) a steady-state component handled by the conventional control circuit. This segmentation allows the fast response function to operate independently without being constrained by the bandwidth limitations of the control circuit, thereby achieving rapid transient response without increasing AC loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The parallel transistor circuit applies preliminary anti-action by preemptively adjusting the output voltage during transient conditions before the conventional control circuit can respond. By acting in advance and in opposition to the impending voltage deviation, this circuit prevents overshoot and instability that would otherwise occur if the control circuit attempted to handle the fast response alone.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS7812578B2DC-DC converter

Publication Date: 2010.10.12 FUJI ELECTRIC CO LTD

AI summary

A DC-DC converter includes a series circuit of a main switch and a choke coil and an output capacitor connected to one end of the series circuit and outputs a DC voltage from the one end of the series circuit. A first MOS transistor is connected in parallel to the series circuit and a second MOS transistor is connected in parallel to the output capacitor. A control circuit controls the gate voltages of the first MOS transistor and/or the second MOS transistor so that the first MOS transistor and/or the second MOS transistor outputs a changed target output voltage, whereby the output voltage is made equal to the target voltage at high speed.