Synchronous Converter Body Diode Conduction Reduction

Solution Overview

Problem

Synchronous converters face challenges in minimizing deadtime to reduce power losses and EMI issues due to body diode conduction, as existing solutions struggle to align the timing of turning off one switch and turning on another to redirect current and charge without causing shoot-through current.

Innovation Solution

The implementation of an electronic pull-down switch that redirects current and charge from the body diode within a nanosecond, using a redirection/removal diode to minimize body diode conduction time, allowing seamless transition without timing alignment requirements, thereby reducing reverse-recovery charge and associated losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If deadtime is minimized to reduce power losses and EMI problems, then converter efficiency is improved, but the risk of shoot-through current increases

Engineering Contradiction:

Improvepower lossesVSAvoidshoot-through current risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The body diode is turned off before the main switch is turned on, preventing shoot-through current. The control circuit detects when the body diode current reaches zero and only then enables the main switch, ensuring no overlapping conduction occurs between the body diode and main switch.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit continuously monitors the body diode current and uses this feedback to determine the optimal timing for turning off the body diode and turning on the main switch. This closed-loop control ensures deadtime is minimized while preventing shoot-through current by adapting to real-time operating conditions.

Inventive Principle:

Principle #23Feedback

2Reliability

If deadtime is extended to prevent shoot-through current, then reliability is improved, but power losses and EMI problems increase

Engineering Contradiction:

Improveshoot-through current preventionVSAvoidpower losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The body diode is turned off before the main switch is turned on, preventing shoot-through current. The control circuit detects when the body diode current reaches zero and only then enables the main switch, ensuring no overlapping conduction occurs between the body diode and main switch.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control circuit continuously monitors the body diode current and uses this feedback to determine the optimal timing for turning off the body diode and turning on the main switch. This closed-loop control ensures deadtime is minimized while preventing shoot-through current by adapting to real-time operating conditions.

Inventive Principle:

Principle #23Feedback

3Reliability

If precise timing alignment is implemented to switch between body diode and main switch, then shoot-through current is avoided, but device complexity increases

Engineering Contradiction:

Improveshoot-through current avoidanceVSAvoidtiming control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The control circuit automatically detects the zero-current crossing point of the body diode and autonomously triggers the main switch without requiring external timing signals or complex synchronization. This self-service approach simplifies the overall system by making the switching timing self-determined based on actual current conditions.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The control circuit continuously monitors the body diode current and uses this feedback to determine the optimal timing for turning off the body diode and turning on the main switch. This closed-loop control ensures deadtime is minimized while preventing shoot-through current by adapting to real-time operating conditions.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10291128B1Minimizing body diode conduction in synchronous converters

Publication Date: 2019.05.14 ANALOG DEVICES INT UNLTD CO

AI summary

A synchronous converter that includes a power source, an inductor, an output terminal, and a control circuit. The control circuit may include: an electronic energizing switch that, when activated, delivers energy from the power source to the inductor; an electronic de-energizing switch that, when activated, delivers energy from the inductor to the output terminal, the electronic de-energizing switch including a body diode; and an electronic pull-down switch that, when activated, turns off the electronic de-energizing switch, redirects current flowing though the body diode of the electronic de-energizing switch, and removes charge from the body diode of the electronic de-energizing switch. The electronic energizing switch and the electronic de-energizing switch may never both be activated at the same time.