Power Conversion Apparatus Snubber Circuit Design
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Solution Overview
Problem
Conventional power conversion apparatuses face challenges in reducing energy loss and avoiding size increase due to high parasitic inductance and switching losses, especially when switching speed is low, and require larger DC capacitors, which complicates miniaturization.
Innovation Solution
A power conversion apparatus with an inverter cell, upper and lower arms, and regenerative rectification circuits that include switching elements, diodes, and capacitors, where the switching elements are sequentially switched to reduce turn-on, turn-off, and recovery losses by storing energy in capacitors and regenerating it efficiently through a floating capacitor, thereby minimizing switching losses without increasing switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching speed is increased to reduce switching loss, then switching loss is reduced, but surge voltage increases due to parasitic inductance
Solution Approach 1:
A snubber circuit is introduced as an intermediary component between the switching element and the load. This snubber circuit absorbs the surge voltage generated by parasitic inductance during switching operations, allowing high-speed switching to be performed without excessive surge voltage. The snubber circuit acts as a mediator that decouples the relationship between switching speed and surge voltage.
Solution Approach 2:
The energy that would normally be lost as surge voltage is converted into useful energy storage in the snubber capacitor. When the switching element turns off, the parasitic inductance generates surge voltage, but this voltage is used to charge the snubber capacitor rather than causing harmful effects. The stored energy can then be dissipated or recycled, transforming a harmful phenomenon into a beneficial energy management mechanism.
2Object-affected harmful factors
If switching speed is decreased to suppress surge voltage, then surge voltage is suppressed, but switching loss increases
Solution Approach 1:
The snubber circuit serves as a mediator that allows the system to maintain high switching speeds without experiencing excessive surge voltage. By providing this intermediate energy absorption mechanism, the system can operate at optimal switching speeds while the snubber handles the surge voltage management, preventing the need to reduce switching speed.
3Reliability
If DC capacitor is enlarged to handle primary and secondary component currents, then current handling capability is improved, but apparatus size increases
Solution Approach 1:
The energy storage function is segmented between multiple components: the DC capacitor handles only the basic wave component current, while the snubber capacitor handles the secondary component currents. This segmentation allows each capacitor to be sized appropriately for its specific function, reducing the total capacitance required and thereby reducing the overall apparatus size while maintaining current handling capability.
Solution Approach 2:
The snubber circuit provides self-service by absorbing and managing the secondary component currents that would otherwise flow through the DC capacitor. This self-service mechanism protects the DC capacitor from excessive current stress, allowing it to be smaller while maintaining system reliability.
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 solution effectively reduces energy loss and prevents size increase by efficiently managing switching losses and parasitic inductance, allowing for compact design without high-speed switching.
Implementation Method 1
a power conversion apparatus including a snubber circuit which suppresses parasitic inductance existing in a switching loop, and a surge voltage occurring due to switching, energy efficiency can be improved by regenerating the energy of the surge voltage absorbed in the snubber circuit to a DC power supply
Implementation Method 2
energy efficiency can be improved by regenerating the energy of the surge voltage absorbed in the snubber circuit to a DC power supply
Data Source
AI summary
According to an embodiment, there is provided an apparatus which can hold down an energy loss and can avoid an increase in size. The apparatus includes a cell including a floating capacitor connected in parallel to an upper-side switching element and a lower-side switching element; an upper arm include including first switch circuits, each including a first switching element, a first diode and a first capacitor, are connected in series; a lower arm including second switch circuits, each including a second switching element, a second diode and a second capacitor, are connected in series; and a circuit which connects a low-side terminal of the cell and a low-side terminal of the first capacitor and connects a high-side terminal of the cell and a high-side terminal of the second capacitor.