Multilevel Boosting Converter Overvoltage Protection

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Solution Overview

Problem

Conventional power conversion devices fail to swiftly suppress overvoltage on semiconductor elements during operation, leading to potential deterioration, especially in multi-level boosting converters where semiconductor elements have lower withstand voltages.

Innovation Solution

A power conversion device with a boosting converter, smoothing capacitor, and inverter, controlled by a unit that fixes semiconductor switching elements in OFF states when the smoothing capacitor voltage exceeds a reference value, preventing excessive voltage application to semiconductor elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If manual operation to open capacitor is performed for overvoltage suppression, then overvoltage can be suppressed, but response time is delayed and swift elimination is impossible

Engineering Contradiction:

Improveovervoltage suppressionVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system automatically detects overvoltage conditions and triggers the switching element to transition to the off state without requiring manual intervention. The control unit monitors the voltage across the smoothing capacitor and autonomously executes the protection sequence, eliminating the time delay associated with manual operations while maintaining reliable overvoltage suppression

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The control unit continuously monitors the voltage across the smoothing capacitor and uses this feedback to automatically control the switching element's state. When overvoltage is detected, the feedback mechanism triggers the switching element to turn off, creating a closed-loop system that responds swiftly to voltage changes without manual intervention

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If multi level boosting converter is used to output multilevel voltages, then voltage output capability is improved, but semiconductor elements have lower withstand voltage and are more susceptible to overvoltage

Engineering Contradiction:

Improvevoltage output capabilityVSAvoidsemiconductor element withstand voltage

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control unit proactively monitors voltage levels and preemptively transitions the switching element to the off state before overvoltage can damage the semiconductor elements. This preliminary protective action prevents the harmful effect from occurring, allowing the system to maintain the benefits of multilevel voltage output while protecting the vulnerable semiconductor components

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The system performs preliminary monitoring of the smoothing capacitor voltage and prepares to switch off the semiconductor element before overvoltage conditions become critical. This advance preparation and execution of protective action ensures that the semiconductor elements are protected from overvoltage damage while the system maintains its multilevel voltage output capability

Inventive Principle:

Principle #10Preliminary action

3Productivity

If switching elements are controlled during operation, then power conversion function is maintained, but overvoltage can be applied to semiconductor elements during operation

Engineering Contradiction:

Improvepower conversion functionVSAvoidovervoltage application

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The control unit dynamically adjusts the state of the switching element based on real-time voltage conditions. During normal operation, the switching element remains on to maintain power conversion function. When overvoltage is detected, the control unit dynamically transitions the switching element to the off state, creating a flexible system that adapts its behavior to prevent overvoltage damage while maintaining productivity during normal conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the operational parameter of the switching element from on-state to off-state in response to voltage conditions. This parameter change allows the system to maintain power conversion function during normal operation while preventing overvoltage application to semiconductor elements when voltage thresholds are exceeded

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11233453B2Power conversion device including a boosting converter for boosting output voltage from a DC power supply

Publication Date: 2022.01.25 MITSUBISHI ELECTRIC CORP

AI summary

The power conversion device includes a multilevel boosting circuit and a smoothing capacitor for smoothing output voltage of the multilevel boosting circuit. The multilevel boosting circuit includes: a leg portion in which four semiconductor elements, i.e., a first diode, a second diode, a first switching element, and a second switching element are connected in series; and an intermediate capacitor connected between a connection point of the first diode and the second diode, and a connection point of the first switching element and the second switching element. When voltage of the smoothing capacitor becomes a reference voltage value or more, the control unit executes a protection mode to fix the first switching element and the second switching element in OFF states.