Isolated Switching Converter Controller for Shoot-Through Prevention
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Solution Overview
Problem
Isolated switching converters face inefficiencies due to shoot-through issues and high switching losses, particularly in high-frequency applications, caused by delays in turning off secondary switches and electromagnetic interference.
Innovation Solution
A controller for isolated switching converters is introduced, comprising a valley detection circuit, pulse frequency modulation circuit, primary on enable circuit, primary off detection circuit, zero cross detection circuit, secondary logic circuit, isolation circuit, and primary logic circuit, which work together to precisely control the primary and secondary switches, avoiding shoot-through and reducing switching losses through quasi-resonant and current continuous modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous rectification is used to improve efficiency, then rectification efficiency is improved, but shoot-through occurs between primary and secondary switches due to timing delays
Solution Approach 1:
The patent uses feedback signals from the primary switch state and resonant voltage detection to dynamically adjust the secondary switch control timing. The controller receives feedback about primary switch on/off states and uses this information to precisely time the secondary switch operations, preventing shoot-through while maintaining synchronous rectification efficiency.
Solution Approach 2:
The patent detects resonant voltage valleys in advance to determine the optimal moment to turn on the primary switch. By detecting the resonant voltage waveform characteristics before switching occurs, the system prepares the switching sequence in advance, ensuring the secondary switch is properly timed to avoid shoot-through conditions.
2Power
If primary switch switching frequency is increased to improve power density, then power density is improved, but switching losses and electromagnetic interference increase
Solution Approach 1:
The patent exploits resonant voltage oscillations in the circuit to time the primary switch operations. By synchronizing switch transitions with the natural resonant frequency of the circuit, the system achieves soft switching conditions that reduce switching losses and electromagnetic interference while maintaining high power density operation.
Solution Approach 2:
The patent dynamically adjusts switching parameters based on detected resonant voltage characteristics. By monitoring the resonant voltage waveform and adapting the switching timing and frequency accordingly, the system optimizes the balance between power density and switching losses, reducing EMI while maintaining efficient power conversion.
3Reliability
If secondary switch turn-off delay is reduced to prevent shoot-through, then shoot-through risk is reduced, but control circuit complexity increases
Solution Approach 1:
The patent uses the circuit's own resonant voltage signal to automatically determine the optimal secondary switch turn-off timing. The resonant voltage waveform inherently provides the timing information needed, eliminating the need for complex external timing circuits or multiple delay stages. The system serves itself by using its natural oscillations to control the switching sequence.
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 controller effectively reduces switching losses and electromagnetic interference, enhancing the efficiency of isolated switching converters by precise control of switching operations, thereby improving the overall performance.
Implementation Method 1
the valley detection circuit coupled to the secondary switch and configured to provide a valley pulse signal in response to one or more valleys of a resonant voltage during off-time of the secondary switch
Data Source
AI summary
A controller of an isolated switching converter having a primary and secondary switch, the controller includes a valley detection circuit for providing a valley pulse signal in response to valleys of a resonant voltage, a pulse frequency modulation circuit for providing a pulse frequency modulation signal based on a feedback signal indicative of an output voltage, a primary on enable circuit for providing a primary on enable signal based on the pulse frequency modulation signal and valley pulse signal, a secondary logic circuit for generating a secondary control signal to control the secondary switch based on a primary off detection signal, a zero cross detection signal and the primary on enable signal, and a primary logic circuit for generating a primary control signal to control the primary switch based on a synchronous signal electrically isolated from the primary on enable signal.