Half-Bridge Converter Pre-Charging Circuit Voltage Imbalance

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Solution Overview

Problem

Conventional half-bridge power converters experience voltage imbalance between capacitor banks, leading to asymmetrical peak voltage stress on secondary-side devices, which reduces efficiency and increases power losses.

Innovation Solution

Incorporating a pre-charging circuit that charges the bootstrap capacitor while minimizing discharge current from one capacitor bank, thereby reducing voltage imbalance between the capacitor banks and alleviating peak voltage stress on secondary-side devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional half-bridge power converter is used without a pre-charging circuit, then the circuit structure is simpler, but voltage imbalance occurs between capacitor banks causing asymmetrical peak voltage stress on secondary-side devices

Engineering Contradiction:

Improvevoltage stress on secondary-side devicesVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pre-charging circuit charges the bootstrap capacitor before the main switching operation begins. By pre-charging the bootstrap capacitor through a dedicated charging current flowpath that includes a pre-charging switch and resistor, the circuit ensures that when the main switching starts, the capacitor banks are already balanced, preventing voltage imbalance and asymmetrical stress on secondary-side devices.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If capacitor banks are charged during switching operation, then the charging process occurs dynamically, but discharge current from one capacitor bank causes voltage imbalance

Engineering Contradiction:

Improvecharging speedVSAvoidvoltage balance between capacitor banks

Core Design Contradiction:

ProductivityVSStability of the object's composition

Solution Approach 1:

The charging process is segmented into two distinct phases: a pre-charging phase before switching operation, and a normal charging phase during switching operation. The pre-charging phase uses a dedicated flowpath with a pre-charging switch and resistor to balance the capacitor banks first, ensuring stable voltage distribution before the dynamic switching charging begins.

Inventive Principle:

Principle #1Segmentation

3Use of energy by moving object

If the bootstrap capacitor is charged during normal switching operation, then the charging occurs continuously, but voltage imbalance leads to increased power losses

Engineering Contradiction:

Improveenergy efficiencyVSAvoidpower losses

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The pre-charging circuit performs the energy-balancing action before normal switching operation begins. By pre-charging the bootstrap capacitor and balancing the voltage between capacitor banks in advance, the system avoids the energy losses that would otherwise occur during voltage imbalance conditions, improving overall energy efficiency.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The pre-charging circuit effectively reduces voltage imbalance and peak voltage stress, enhancing the reliability and service life of secondary-side devices by allowing the use of equally rated rectification devices, thus improving conversion efficiency.

Implementation Method 1

a first capacitor bank and a second capacitor bank in series with the first capacitor bank, and also a bootstrap capacitor configured to be charged by current flowing through a charging current flowpath

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

a transformer dividing the half-bridge power converter into a primary side and a secondary side

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Data Source

PatentUS10536087B1Half-bridge power converter with pre-charging circuit

Publication Date: 2020.01.14 TDK LAMBDA AMERICAS

AI summary

A half-bridge power converter includes a transformer dividing the half-bridge power converter into a primary side and a secondary side. Disposed on the first side is a first capacitor bank and a second capacitor bank in series with the first capacitor hank, and also a bootstrap capacitor configured to be charged by current flowing through a charging current flowpath. The charging current flowpath extends at least through a pre-charging circuit located on the primary side, the pre-charging circuit being configured to reduce a voltage imbalance between the first capacitor bank and the second capacitor bank. The half-bridge power converter also includes a discharging current flowpath that extends at least through a primary winding of the transformer and the pre-charging circuit.