CrM Totem Pole PFC Digital Control With Average Current Sharing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing control methods for totem pole power factor correction (PFC) circuits in critical conduction mode face issues with uneven phase currents, large ripple generation, and slow dynamic response, particularly in multi-phase systems, due to inconsistent inductance values and noise during current sampling.

Innovation Solution

A hybrid voltage-current mode dual closed-loop control method using a digital signal processor (DSP) and micro-controller (MCU) to determine the on-time of PFC switches based on average inductor current and input/output voltages, incorporating a feedforward coefficient to enhance dynamic response and current sharing, and a phase closed loop control to stabilize phase error.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If voltage mode control is used in multi-phase PFC, then the control simplicity is improved, but uneven phase currents and large ripple are generated

Engineering Contradiction:

Improvecontrol simplicityVSAvoidphase current uniformity

Core Design Contradiction:

Ease of operationVSStability of the object's composition

Solution Approach 1:

The patent introduces a phase current detection mechanism that monitors each phase's current and feeds this information back to the control system. The controller adjusts the switching duty cycle of each phase based on the detected current differences, ensuring balanced current distribution across all phases while maintaining voltage mode control simplicity.

Inventive Principle:

Principle #23Feedback

2Volume of moving object

If operating frequency is increased to reduce inductor size, then power density is improved, but inductance tolerance variations cause more uneven current

Engineering Contradiction:

Improveinductor sizeVSAvoidcurrent balance

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The patent implements dynamic adjustment of switching duty cycles for each phase based on real-time current detection. The control system continuously adapts the switching parameters to compensate for inductance variations, allowing the system to maintain current balance despite fixed inductor tolerances and high operating frequencies.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system varies the switching duty cycle parameter for each phase according to the detected current levels and inductance variations. By dynamically changing this parameter, the system compensates for component tolerances and maintains balanced operation at high frequencies with reduced inductor size.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If current mode control is used to address uneven current, then current balance is improved, but noise and slow dynamic response are introduced

Engineering Contradiction:

Improvephase current uniformityVSAvoiddynamic response

Core Design Contradiction:

Stability of the object's compositionVSSpeed

Solution Approach 1:

The patent applies partial current mode control by detecting phase current levels and using this information to adjust duty cycles, rather than implementing full current mode control with separate current loops for each phase. This partial approach achieves current balance while avoiding the noise and complexity of complete current mode control.

Inventive Principle:

Principle #16Partial or excessive action

4Device complexity

If single voltage loop control is used, then control simplicity is improved, but input and output dynamic characteristics performance is reduced

Engineering Contradiction:

Improvecontrol loop structureVSAvoiddynamic characteristics performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent enhances the single voltage loop control by adding multi-functionality to the controller. The same controller that manages voltage regulation also performs phase current detection and balancing, and coordinates multi-phase switching. This universal controller achieves improved dynamic performance without requiring separate dedicated control loops for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS20250350194A1System and methods for digital control of totem pole power factor correction circuits in critical conduction mode

Publication Date: 2025.11.13 NAVITAS SEMICON LTD

AI summary

A CrM totem pole PFC digital control method. In one aspect, the method includes mixed use of control of voltage outer loop and average current inner loop to improve dynamic performance and achieve current sharing performance. In another aspect, a PFC circuit includes a first switch coupled to a second switch, an inductor coupled between a switch node and an AC input terminal, and a control circuit arranged to: detect an input voltage at the AC input terminal; detect a current in the inductor and generate a signal corresponding to an average of the current; detect an output voltage of the PFC circuit at an output terminal; generate a reference current based on the detected output voltage and the detected input voltage and control a first on-time of the first switch and a second on-time of the second switch based on comparison of the signal to the reference current.