Isolated Power Converter Controller Supply Across Wide Output Voltages
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Solution Overview
Problem
Power adapters require a wide output voltage range (3.3V to 24V) and a self-supply method for efficient operation across a wide input voltage range (90 Vac to 264 Vac), but existing designs face challenges in meeting efficiency and power density requirements, especially at varying load conditions.
Innovation Solution
An isolated power converter with a transformer having primary and secondary auxiliary windings and a resonant capacitor, where a voltage supply circuit selects an appropriate voltage for the controller based on the secondary side voltage, using a combination of auxiliary winding and resonant capacitor voltages to ensure efficient operation across the wide voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single auxiliary winding is used for controller supply, then the design is simple, but the efficiency and power density requirements cannot be met across wide voltage ranges
Solution Approach 1:
The auxiliary winding is divided into multiple segments (first auxiliary winding and second auxiliary winding) with different turn ratios. Each segment provides optimized voltage transformation for specific output voltage ranges, enabling high efficiency across the full 3.3V to 24V output range while maintaining manageable design complexity through modular segmentation.
Solution Approach 2:
The controller supply voltage is dynamically selected based on the output voltage level. A voltage selection circuit automatically switches between the first auxiliary winding (for lower voltages) and the second auxiliary winding (for higher voltages), adapting the auxiliary supply configuration to match the current operating conditions and maintain optimal efficiency.
2Adaptability or versatility
If the output voltage range is extended to 24V, then more devices can be powered, but the controller supply voltage becomes insufficient at low output voltages
Solution Approach 1:
The auxiliary winding system is segmented into two independent windings with different turn ratios. The first auxiliary winding provides sufficient voltage for controller supply when output voltage is low (3.3V-12V), while the second auxiliary winding provides adequate supply voltage when output voltage is high (18V-24V), ensuring continuous adaptability across the full output range.
Solution Approach 2:
A voltage selection circuit acts as an intermediary between the two auxiliary windings and the controller. This intermediary automatically selects the appropriate auxiliary winding based on the output voltage level, ensuring the controller receives adequate supply voltage regardless of whether the output is at low or high end of the 3.3V to 24V range.
3Device complexity
If fixed frequency flyback is used, then the control is simple, but the efficiency at light-load conditions is poor
Solution Approach 1:
The controller implements dynamic frequency modulation based on load conditions. At light-load conditions, the switching frequency is automatically adjusted to operate in discontinuous conduction mode (DCM), improving light-load efficiency. At full-load conditions, the frequency is adjusted to achieve zero-voltage switching (ZVS), maintaining high efficiency across the entire load range while keeping the control circuitry relatively simple.
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 enables efficient power supply design for wide output voltage ranges, reduces component stress, and optimizes costs by allowing the use of cost-effective components, while ensuring adequate power supply to the controller across varying output voltages.
Implementation Method 1
a resonant capacitor electrically connected to the primary winding
Implementation Method 2
a transformer comprising a primary winding, a first auxiliary winding, and a second auxiliary winding
Data Source
AI summary
An isolated power converter includes: a transformer having primary winding and first and second auxiliary windings on the primary side; a converter stage configured to convert a DC input for driving the primary winding and having a resonant capacitor electrically connected to the primary winding; a controller configured to control switching of the converter stage; and a voltage supply circuit configured to select a first voltage as a supply voltage for the controller if a voltage proportional to a secondary side voltage of the transformer is at a first level or select a second voltage as the supply voltage if the voltage proportional to the secondary side voltage is at a second level greater than the first level. The first voltage corresponds to a summation of voltages across the first auxiliary winding and the resonant capacitor. The second voltage corresponds to a voltage across the second auxiliary winding.