DC-DC Converter Phase Control for Switching Loss Reduction
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Solution Overview
Problem
Existing DC-DC converters face high switching losses due to the lack of zero voltage switching, leading to increased disturbance in output current waveforms and noise, especially at low output voltage bands, and high costs.
Innovation Solution
A DC-DC converter design incorporating a primary-side and secondary-side converter with full bridge circuits, parallel semiconductor switching devices and capacitors, and a control unit that adjusts switching control to achieve a predetermined phase difference and phase offset, reducing switching losses and saturations in reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional switching control is used in DC-DC converters, then the converter can operate with simple control logic, but switching loss increases and zero voltage switching cannot be achieved
Solution Approach 1:
The patent implements dynamic switching control where the switching timing is continuously adjusted based on real-time voltage detection. The control unit dynamically modifies the switching phase to achieve zero voltage switching conditions, transforming the static switching approach into a dynamic adaptive system that optimizes switching timing for minimal loss.
Solution Approach 2:
The patent employs feedback mechanisms by detecting the voltage across switching devices and using this information to adjust switching timing. The control unit receives voltage feedback signals and modifies the switching control accordingly to maintain zero voltage switching conditions, creating a closed-loop control system that actively compensates for variations in operating conditions.
2Device complexity
If high potential voltage is applied to switching devices without zero voltage switching, then the converter can maintain simple circuit structure, but switching loss becomes great
Solution Approach 1:
The patent applies preliminary action by pre-charging or pre-discharging capacitors connected in parallel with switching devices before switching occurs. This preparatory action ensures that the voltage across the switching device is reduced to zero or near-zero before the switching event, enabling lossless switching without complicating the overall circuit structure.
Solution Approach 2:
The patent introduces capacitor elements as intermediary components connected in parallel with switching devices. These capacitors act as mediators that temporarily store or release energy to maintain zero voltage conditions across the switching devices during switching transitions, thereby reducing switching loss while preserving circuit simplicity.
3Speed
If conventional switching control is used, then the converter can operate with standard switching frequencies, but disturbance in output current waveforms and noise increase at low output voltage bands
Solution Approach 1:
The patent changes the timing parameter of switching operations by introducing phase adjustments and timing offsets based on detected voltage conditions. This parameter modification allows the converter to operate at standard switching frequencies while eliminating waveform disturbances and noise, particularly in low output voltage bands, by optimizing the exact moment of switching transitions.
4Power
If the converter operates at high power levels, then it can meet high power transmission requirements, but the primary-side and secondary-side reactors become saturated
Solution Approach 1:
The patent implements periodic switching action with optimized timing that prevents continuous high current stress on reactors. By using controlled periodic switching with zero voltage switching, the converter can transmit high power levels while allowing reactors to recover between cycles, preventing saturation and maintaining reliability at high power operation.
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 switching losses, suppresses noise and disturbance in output current waveforms, and lowers costs by optimizing power transmission and reactor inductance.
Implementation Method 1
The predetermined phase difference is an offset from 180 degrees by an angle corresponding to approximately 1/4 the inverse of resonance frequency. The resonance frequency is determined by the primary-side reactor and the primary-side capacitors.
Implementation Method 2
a transformer having a primary winding and a secondary winding
Implementation Method 3
The primary-side reactor includes at least one of (1) a coil connected to the primary winding and (2) leakage inductance of the primary winding. The secondary-side reactor includes at least one of (A) a coil connected to the secondary winding and (B) leakage inductance of the secondary winding.
Data Source
AI summary
[Object] To realize a DC-DC converter that can reduce switching loss when zero voltage switching is not achieved.[Solution] When starting second control in conjunction with first control, a control unit (10) performs reduction of predetermined phase difference and increase of phase offset at the same time. A smallest value of output power of the DC-DC converter (CON1) performing reduction of the predetermined phase difference is lower than power at which a primary-side reactor (6) is saturated by current flowing through the primary-side reactor (6) under the first control and lower than power at which a secondary-side reactor (7) is saturated by current flowing through the secondary-side reactor (7) under the first control, at a desired output voltage under the first control.