Phase Shift Full Bridge Converter with Secondary Clamp Circuit
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Solution Overview
Problem
Existing PWM full bridge converters for battery chargers face issues such as high circulation current, severe voltage stress, and significant switching losses on the secondary side, leading to increased conduction and switching losses, as well as a larger output filter size.
Innovation Solution
A phase shift full bridge converter with a clamping circuit connected to the center-tapped clamp circuit on the secondary side, utilizing a clamping circuit with rectifier diodes and capacitors to clamp voltages and reduce circulating currents, thereby lowering voltage stress and switching losses, and resizing the output filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PWM PSFB converter is used for battery charger, then primary switches can achieve zero-voltage switching turn-on operation, but conduction loss increases due to high circulation current
Solution Approach 1:
The patent extracts and removes the circulation current from the system by introducing a clamp circuit connected to the center-tap of the transformer on the secondary side. This clamp circuit provides an alternative path for the circulating current, effectively eliminating it from the main power conversion path and reducing conduction losses while preserving the zero-voltage switching capability of the primary switches
2Ease of operation
If PWM PSFB converter is used for battery charger, then it can be simply controlled compared to frequency-modulation converter, but voltage stress in rectification stage seriously increases
Solution Approach 1:
The patent introduces a clamp circuit as an intermediary component connected to the center-tap of the transformer on the secondary side. This clamp circuit acts as a mediator that limits and controls the voltage stress in the rectification stage, preventing excessive voltage peaks while maintaining the simple PWM control scheme
3Power
If PWM PSFB converter is used for battery charger, then it can operate in power range of several kW, but switching loss occurring in rectification stage is very large
Solution Approach 1:
The patent converts the harmful effect of large reverse recovery current in the rectification stage into a beneficial outcome. By introducing the clamp circuit connected to the center-tap, the circuit controls and reduces the reverse recovery current, thereby converting the previously harmful large switching loss into a reduced loss condition while maintaining several kW power operation
4Power
If output voltage is large in PWM PSFB converter, then it can meet battery charger requirements, but size of output filter stage is increased
Solution Approach 1:
The patent extracts and removes the circulation current that would otherwise require large output filter components. By eliminating the circulation current through the clamp circuit, the patent reduces the ripple current and voltage stress on the output filter, allowing for a smaller output filter size while maintaining the required output voltage level for battery charging
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 proposed converter effectively removes circulation currents, reduces voltage stress and switching losses, and minimizes the size of the output filter, achieving improved efficiency and power density while maintaining zero-voltage switching.
Implementation Method 1
Voltages of second rectifier diode and the fourth rectifier diode are clamped two times to a clamp voltage when the first clamping diode becomes conductive
Implementation Method 2
a phase shift full bridge (PSFB) converter includes a primary-side circuit and a secondary-side circuit, the secondary-side circuit uses a voltage applied by the primary-side circuit
Data Source
AI summary
Disclosed are a new phase shift full bridge (PSFB) converter using a clamp circuit connected to a center-tapped clamp circuit and an operating method thereof. The new PSFB converter using a clamp circuit connected to a center-tapped clamp circuit includes a primary-side circuit including a plurality of inductors connected to one end between a first switch and a second switch which are connected in series and to one end between a third switch and a fourth switch which are connected in series and a secondary-side circuit using a voltage applied by the primary-side circuit and including a clamping circuit configured with a first rectifier diode, a second rectifier diode, a third rectifier diode, a fourth rectifier diode, a first clamping diode, a second clamping diode and a capacitor in a center-tapped clamp circuit.