Soft-Switching Control Circuit for Boost-Type PFC Converter

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The existing control methods for three-phase six-switch boost-type power factor correction (PFC) converters are complex, resource-intensive, costly, and difficult to reproduce, with complications in controlling switching transistors and inhibiting diode reverse recovery, leading to inefficiencies and electromagnetic interference.

Innovation Solution

A control circuit using a one-cycle control algorithm for primary switching transistors and an auxiliary switch control circuit with phase-reversed clock signals and reset signals to manage the auxiliary switching transistor, simplifying the control and reducing costs, while achieving soft-switching operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If improved space vector modulation method is used to control three-phase boost-type PFC converter, then soft-switching operation and diode reverse recovery inhibition are achieved, but control algorithm complexity increases

Engineering Contradiction:

Improvesoft-switching operationVSAvoidcontrol algorithm complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control algorithm is segmented into three independent parts: sector determination (identifying which 60-degree sector the voltage vector is in), basic vector selection (choosing two adjacent basic vectors), and pulse width modulation (calculating duty cycles). This segmentation simplifies the overall control structure while maintaining soft-switching capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediary variable 'm' (modulation index) is introduced to simplify the relationship between reference voltage and switching duties. The modulation index serves as a mediator that linearizes the control relationship, making the algorithm easier to implement while achieving the same soft-switching effect.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Extent of automation

If smart chip such as DSP or MCU is used to fulfill the control algorithm, then control functionality is achieved, but development period and cost increase

Engineering Contradiction:

Improvecontrol automationVSAvoiddevelopment period

Core Design Contradiction:

Extent of automationVSLoss of time

Solution Approach 1:

The control system uses self-service by implementing the simplified algorithm directly in hardware control circuits rather than relying on external smart chips. The system serves itself through inherent circuit properties and simple logic, eliminating the need for complex programming and long development cycles associated with DSP/MCU implementation.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention replaces expensive smart chips (DSP/MCU) with simple, low-cost control circuits that can be easily implemented using basic electronic components. This substitution reduces both hardware cost and development time, making the system more economically viable.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If auxiliary circuits are added to achieve soft-switching, then switching transistor and diode performance improve, but circuit complexity increases

Engineering Contradiction:

Improveswitching transistor performanceVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control circuit performs multiple functions using the same components: it determines sectors, selects basic vectors, calculates pulse widths, and generates switching signals all through a unified control mechanism. This multi-functionality reduces the need for separate auxiliary circuits while maintaining soft-switching performance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention converts the inherently complex three-phase control problem into a beneficial simplified structure by exploiting the symmetry and periodicity of three-phase systems. The 12-sector division and basic vector method transform a potentially harmful complexity into a structured, manageable control approach that actually reduces overall system complexity.

Inventive Principle:

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

Data Source

PatentUS10186957B2Soft-switching control circuit of boost-type PFC converter

Publication Date: 2019.01.22 INSTITUTE OF GEOLOGY AND GEOPHYSICS CHINESE ACADEMY OF SCIENCES

AI summary

A soft-switching control circuit of a boost-type PFC converter is provided. The boost-type PFC converter is a three-phase six-switch boost-type PFC converter, which includes six primary switching transistors and an auxiliary switching transistor. The control circuit includes a primary switch control circuit configured to output driving signals for the primary switching transistors by a one-cycle control algorithm to drive two of the primary switching transistors, and an auxiliary switch control circuit configured to provide a reset signal to the primary switch control circuit for governing a command from the primary switch control circuit to the primary switching transistors. The auxiliary switch control circuit outputs a driving signal for the auxiliary switching transistor to control the auxiliary switching transistor. The primary switch control circuit includes a section selecting circuit, an integrating circuit, a merging circuit and a comparing circuit. Therefore, the disclosure can reduce cost with the simple control.