Switched Mode Power Converter Duty Cycle Control
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Solution Overview
Problem
Existing switched mode power converters operate with poor efficiency, especially in lower power modes, due to inefficient energy transfer across the transformer, which is costly and inefficient, particularly in applications like personal computer power supplies.
Innovation Solution
The implementation of a switched mode power converter with primary and secondary side active switch devices and control means that adjust the duty cycle of the primary side switch based on the secondary side switch, reducing energy transfer time and magnetic losses, allowing for continuous or discontinuous output current modes to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the duty cycle of the primary side switch is maintained at conventional levels during stand-by mode, then the transformer continues to transfer energy at normal rates, but energy efficiency deteriorates due to unnecessary energy transfer and magnetic losses
Solution Approach 1:
The patent implements dynamic duty cycle adjustment where the primary side switch duty cycle is dynamically reduced during stand-by mode based on the secondary side switch duty cycle. This dynamic adaptation allows the system to optimize energy efficiency by minimizing unnecessary energy transfer while maintaining required output power, directly resolving the contradiction between reducing magnetic losses and maintaining productivity.
Solution Approach 2:
The patent changes the operational parameters by reducing the primary side switch duty cycle to be substantially equal to or less than the secondary side switch duty cycle during stand-by mode. This parameter change transforms the transformer's operation from continuous energy transfer to a more efficient mode with reduced magnetic losses, while still delivering required power output.
2Loss of energy
If the primary side switch duty cycle is reduced to improve efficiency, then energy transfer time is minimized, but the complexity of coordination between primary and secondary side switching increases
Solution Approach 1:
The patent employs feedback control where the primary side control means receives information about the secondary side switch duty cycle and adjusts the primary side switch duty cycle accordingly. This feedback mechanism ensures proper coordination between primary and secondary switching, maintaining system stability and proper operation while achieving reduced energy losses, thus resolving the contradiction between efficiency improvement and control complexity.
3Loss of energy
If active switch devices are used on both primary and secondary sides to enable duty cycle reduction, then efficiency in stand-by mode improves, but device complexity and cost increase compared to conventional diode-based rectifiers
Solution Approach 1:
The patent introduces dynamic control capability by replacing conventional static rectifying diodes with active switch devices on the secondary side. This enables the system to dynamically adjust the duty cycle during stand-by mode, achieving significant efficiency improvements. The active switches provide the necessary controllability to reduce energy losses while maintaining required output power.
Solution Approach 2:
The patent changes the operational parameters enabled by using active switch devices instead of passive diodes. The active switches allow for variable duty cycle control on the secondary side, which is essential for the coordinated duty cycle reduction strategy. This parameter flexibility resolves the contradiction by enabling efficient stand-by operation while maintaining system controllability.
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 configuration significantly increases efficiency in stand-by mode by reducing the duty cycle and frequency of the primary side switch, leading to improved energy transfer and reduced magnetic losses, achieving efficiencies of 50% or better in lower power modes.
Implementation Method 1
a transformer having a primary winding and at least one secondary winding
Implementation Method 2
Energy is stored in an output inductor and a regulated voltage is supplied to the load on the secondary side by switching the flow of current into the output inductor
Data Source
AI summary
The invention relates to a switched mode power converter and a method of operating such a converter A switched mode power converter according to the invention includes a transformer (2) having a primary winding (2a) and at least one secondary winding (2b) and a secondary side rectifier circuit including an output filter (6, 10) coupled to the at least one secondary winding (2b), and a secondary side active switch device (S3) coupled between the at least one secondary winding and the output filter. The converter further includes primary side and secondary side control means (12, 16, 18) for regulating the switching of the primary side and secondary side switches, respectively, and configured so as to reduce the duty cycle of the primary side switch device (S1) during a lower power mode of operation of the converter, the reduction of the duty cycle of the primary side switch being determined with reference to the duty cycle of the secondary side switch (S3). This leads to a substantial increase in the efficiency of operation in the low power mode.