Primary-Side Output Current Control Circuit for Variable Frequency Power Converters
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Solution Overview
Problem
Existing power converter control circuits are inefficient in managing output current for power converters with changeable switching frequencies, leading to significant power loss, increased cost, and space requirements due to separate current and voltage detection circuits.
Innovation Solution
A control circuit that integrates current-detection, voltage-detection, and signal-processing components to generate switching signals for transformers, allowing for output current regulation in power converters with changeable switching frequencies by correlating primary-side switching currents, reflected voltages, and discharge times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate output current detection and control circuit is equipped at the output of the power converter, then the output current can be precisely controlled, but considerable power loss is consumed and the PCB space and cost increase
Solution Approach 1:
The patent combines the output current detection function with the existing switching control circuit by detecting the primary-side current signal, which is proportional to the output current. This merging eliminates the need for a separate output current detection circuit, thereby reducing power loss and PCB space while maintaining control precision.
Solution Approach 2:
The switching control circuit is designed to perform multiple functions: it controls the switching of power devices and simultaneously detects the output current through primary-side current sensing. This multi-functionality reduces the overall circuit complexity and component count, addressing both power loss and space constraints.
2Measurement precision
If a separate output current detection and control circuit is equipped at the output of the power converter, then the output current can be precisely controlled, but the PCB space and cost increase
Solution Approach 1:
The patent merges the output current detection function into the existing switching control circuit by utilizing primary-side current sensing. This integration eliminates separate detection circuits and reduces PCB footprint while maintaining the ability to precisely control output current through the unified control mechanism.
Solution Approach 2:
The switching control circuit is designed to simultaneously perform switching control and output current detection functions. By making the control circuit multi-functional, the patent reduces the number of separate components needed, thereby reducing PCB space requirements while preserving control precision.
3Adaptability or versatility
If prior art control circuits are used, then the switching frequency is predictable and output current detection is facilitated, but the circuits cannot be applied to power converters with changeable switching frequency such as resonant power converters
Solution Approach 1:
The patent employs dynamic detection methods that can adapt to changing switching frequencies. By detecting primary-side current signals and reflected voltages in real-time and using dynamic calculation to determine output current, the circuit maintains functionality across variable frequency operations without requiring fixed-frequency design constraints.
Solution Approach 2:
The control circuit is designed to handle parameter changes in switching frequency by using proportional relationships between primary-side current, reflected voltage, and output current. These relationships remain valid across frequency variations, allowing the circuit to adapt to different operating conditions without increasing complexity.
Data Source
AI summary
A control circuit controls the output current of the power converter at the primary side of the transformer. The control circuit includes a current-detection circuit for generating a primary-current signal in response to the switching current of the transformer. A voltage-detection circuit is coupled to the transformer to generate a period signal and a discharge-time signal in response to the reflected voltage of the transformer. A signal-process circuit is utilized to generate a current signal in response to the primary-current signal, the period signal and the discharge-time signal. The period signal is correlated to the switching period of the switching signal of the power converter. The discharge-time signal is correlated to the duty cycle of switching current at the secondary-side of the transformer. The current signal is correlated to the output current of the power converter.