Parallel Diode Circuit Layout for Free-Wheeling Current Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
When the switching device of the lower arm is turned off, the current flowing through it can cause breakdown of the free-wheeling diode due to the parasitic diode in the upper arm having a higher forward voltage, leading to excessive current flow through the free-wheeling diode.
Innovation Solution
The use of a Schottky junction diode with a lower forward voltage in parallel with a PN junction diode, coupled via wiring members with controlled inductance to manage current flow and prevent excessive current through the free-wheeling diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free-wheeling diode with low forward voltage is used to prevent breakdown, then the diode becomes vulnerable to excessive current flow when the parasitic diode has higher forward voltage
Solution Approach 1:
An inductor is introduced as an intermediary component in series with the free-wheeling diode. This inductor acts as a mediator that limits the rate of current change (di/dt), thereby preventing excessive current from flowing through the free-wheeling diode while still allowing it to perform its breakdown protection function. The inductor's opposing magnetic field during current changes effectively mediates between the conflicting requirements of low forward voltage and current protection.
2Ease of operation
If the forward voltage of the parasitic diode is higher than the free-wheeling diode, then current preferentially flows through the free-wheeling diode, but this causes breakdown of the free-wheeling diode
Solution Approach 1:
The inductor is configured to provide preliminary anti-action by opposing the rapid increase of current that would otherwise flow through the free-wheeling diode. When voltage is applied to the free-wheeling diode, the inductor generates a back-EMF that counteracts the current surge, preventing the diode from experiencing excessive current before it can be damaged. This preliminary opposition prevents the harmful effect before it occurs.
3Object-generated harmful factors
If wiring inductance is increased to limit current flow through the free-wheeling diode, then current distribution improves, but the overall circuit performance may be affected
Solution Approach 1:
The inductor is placed locally only in series with the free-wheeling diode branch, rather than increasing the inductance of the entire circuit. This localized approach ensures that current distribution is improved specifically in the free-wheeling diode path without significantly affecting the overall circuit performance. The inductor's effect is confined to where it is needed, maintaining low loss in the main power path while providing current limitation where required.
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
This configuration prevents breakdown of the free-wheeling diode by distributing current flow through both diodes, ensuring safe operation during dead time periods.
Implementation Method 1
a second diode having a Schottky junction where the forward voltage is a second voltage that is smaller than the first voltage
Implementation Method 2
a second wiring member coupling the first terminal to the second terminal via the second diode, the second wiring member having an inductance larger than an inductance of the first wiring member
Data Source
AI summary
An electronic circuit having a first terminal and a second terminal. The electronic circuit includes a first diode having a PN junction where a forward voltage is a first voltage, a second diode having a Schottky junction where the forward voltage is a second voltage that is smaller than the first voltage, a first wiring member coupling the first terminal to the second terminal via the first diode, and a second wiring member coupling the first terminal to the second terminal via the second diode. The second wiring member has an inductance larger than an inductance of the first wiring member.