ZVS+ZCS DC/DC Converter with Controlled Saturation Inductance
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Solution Overview
Problem
Conventional phase shifted full bridge ZVS DC/DC converters face issues such as circulating current on the secondary side, inability to achieve ZVS voltage soft switch on across a wide load range, duty cycle loss due to leakage inductance, and electromagnetic compatibility problems, limiting the efficiency and stability of high-power switch tubes, and restricting the capacity of a single module to less than 5 KW.
Innovation Solution
The implementation of a ZVS+ZCS integrated soft switching DC/DC converter with a nanocrystal high permeability ring magnetic core, controlled saturation inductance on the primary side, and an RCD buffer circuit on the secondary side, along with PWM switching frequency and duty cycle adjustments, ensures double soft switching and eliminates circulating currents, maintaining phase alignment of primary voltage and current, and optimizing electromagnetic compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional phase shifted full bridge ZVS DC/DC converter is used, then the converter can operate with voltage soft switching, but circulating current appears on the secondary side and duty cycle loss occurs due to leakage inductance
Solution Approach 1:
The patent extracts and eliminates the harmful circulating current component from the converter operation by implementing ZCS for the lag arm switches, separating the useful power transfer from the harmful circulating current that causes duty cycle loss
Solution Approach 2:
The patent converts the harmful leakage inductance effect into a beneficial resonant element by using it to enable current soft switching (ZCS) for the lag arm, transforming the source of duty cycle loss into the mechanism that achieves lossless current commutation
2Power
If conventional ZVS DC/DC converter is used, then voltage soft switching is achieved, but the converter capacity is restricted to less than 5 KW
Solution Approach 1:
The patent merges ZVS and ZCS techniques into an integrated soft switching scheme where lead arm switches achieve voltage soft switching (ZVS) and lag arm switches achieve current soft switching (ZCS), combining the advantages of both methods to enable high-power operation with improved stability
Solution Approach 2:
The patent employs composite magnetic materials including nanocrystal high permeability ring magnetic core and new high permeability material in the transformer, combining different material properties to achieve both high power capacity and operational stability
3Object-affected harmful factors
If conventional ZVS DC/DC converter is used, then the converter can operate, but electromagnetic compatibility problems occur
Solution Approach 1:
The patent uses the leakage inductance that traditionally causes harmful electromagnetic interference and duty cycle loss to instead enable resonant current soft switching, converting the harmful effect into a beneficial resonant mechanism that improves both EMI performance and efficiency
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 solution achieves high efficiency, reduces switch losses, and enhances electromagnetic compatibility, allowing for increased capacity beyond 5 KW, with the highest efficiency reaching 95.5% in a 30 KW DC/DC converter module.
Implementation Method 1
The transformer establishes an electromagnetic induction relation of 'voltage ratio between the primary coil N1 and the secondary coil N2 is proportional to the turns; current ratio between the primary coil N1 and the secondary coil N2 is inverse proportional to the turns n=V1/V2=N1/N2, l/n=I1/I2=N2/N1' by absorbing the exciting current Im to generate the main flux
Implementation Method 2
Q1 and Q3 are on the lead arm; Q4 and Q2 are on the lag arm; Q1, Q2, Q3 and Q4 are four high capacity IGBT. Each IGBT comprises a collector, an emitter and a gate to constitute a voltage controlled switch
Implementation Method 3
A built-in reverse diode Di and a commutating capacitor Cpi (a sum of the built-in capacitor and the parallel connected capacitor, i=1, 2, 3, 4) are parallel connected to two ends of the switch
Implementation Method 4
A nanocrystal high permeability ring magnetic core is adopted to produce the transformer T1; the secondary side coil N2 is winded on the inner side to reduce the leakage inductance Lσ2
Implementation Method 5
an RCD buffer circuit on the secondary side of the transformer
Data Source
AI summary
A ultra-high power ZVS+ZCS integrated soft switching DC/DC converter is disclosed, which adopts a phase shifted full bridge ZVS (zero voltage switching) DC/DC converter circuit. A saturation inductance Lk=Lk1+Lk2 controlled by a load current is series connected to a primary side of a high permeability ring transformer. A RCD buffer circuit for ZCS (zero voltage switching) current zero-crossing switching off is connected to a secondary side of the transformer. When a lead arm commutates, a refringence of a load current is blocked; the ZVS (zero voltage switching) is ensured; exciting current disappears; a lag arm realizes ZCS zero current commutating. The controlled inductance LK assists to establish a corresponding load refringenced current and the exiting current and recovers electromagnetic induction; The RCD buffer circuit softens the reverse current of bridge rectifier and oscillations caused by the leakage inductance on secondary side of the transformer and the buffer capacitor are attenuated.