Power Conversion Apparatus Snubber Capacitor Timing Control
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Solution Overview
Problem
Existing power conversion apparatuses for high-voltage DC/DC conversion are limited by the breakdown voltage of semiconductor switching devices, restricting the maximum DC voltage to half the breakdown voltage, and suffer from increased loss and reliability issues due to snubber capacitors' discharge current and large component counts.
Innovation Solution
A power conversion apparatus with a primary and secondary bridge circuit, each leg containing multiple semiconductor switching devices in series and snubber capacitors in parallel, controlled to provide a dead time period between arm turn-ons, allowing for high-voltage handling without excessive loss or reliability reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a plurality of switching devices are connected in series to increase voltage handling capability, then the maximum DC voltage can be increased to equal or higher than the breakdown voltage, but the discharge current from snubber capacitors increases causing excessive loss and reliability reduction
Solution Approach 1:
The control unit controls the timing of turning on the semiconductor switching devices such that the turning on is completed before the snubber capacitors are fully charged. This preliminary action prevents the discharge current from flowing into the switching devices, thereby reducing loss while maintaining high voltage handling capability through series connection
Solution Approach 2:
The control unit monitors the charge state of the snubber capacitors and adjusts the turning on timing of the semiconductor switching devices accordingly. This feedback mechanism ensures that switching occurs at the optimal moment to minimize discharge current and energy loss
2Object-affected harmful factors
If snubber capacitors are connected in parallel with switching devices to suppress overvoltage, then voltage spikes are reduced, but discharge current flows into switching devices causing loss and reliability issues
Solution Approach 1:
The semiconductor switching devices are turned on before the snubber capacitors complete charging. This timing control ensures that when the switching devices conduct, the snubber capacitors have minimal charge, preventing harmful discharge currents while maintaining overvoltage suppression capability
Solution Approach 2:
The invention converts the potential harmful discharge current from snubber capacitors into a beneficial timing control mechanism. By intentionally allowing the capacitors to charge partially and then switching, the system utilizes the charging process to achieve soft switching conditions, reducing loss and improving reliability
3Stability of the object's composition
If the resonant frequency of the resonant circuit is matched with the on/off frequency of switching devices to prevent sudden voltage increase, then voltage stability is improved, but the on/off frequency must be kept low requiring large resonant circuit components
Solution Approach 1:
The invention extracts the voltage stabilization function from the resonant circuit frequency matching approach and implements it through timing control of the semiconductor switching devices. This eliminates the need for large resonant circuit components while maintaining voltage stability through controlled switching sequences
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
Enables handling of voltages equal to or higher than the switching device breakdown voltage with reduced losses and improved reliability by optimizing snubber capacitor charge/discharge times and series inductance to manage discharge currents.
Implementation Method 1
a plurality of snubber capacitors CS11P, CS11N, CS12P, and CS12N respectively connected in parallel with the semiconductor switching devices Q11P, Q11N, Q12P, and Q12N
Implementation Method 2
a transformer 101 having a primary-side winding connected to the first bridge circuit 10 and a secondary-side winding connected to the second bridge circuit 20
Data Source
AI summary
A first bridge circuit includes a first leg and a second leg. The first leg includes an upper arm and a lower arm. The upper arm includes a plurality of switching devices connected in series, a plurality of freewheeling diodes connected in antiparallel with the switching devices, respectively, and a plurality of snubber capacitors connected in parallel with the switching devices, respectively. A control circuit controls the first and second bridge circuits such that a dead time period is provided between a turn-on period of an upper arm and a turn-on period of a lower arm included in each of the first and second legs, in each of the first and second bridge circuits.