Transformer Current Counting for Valley Switching Loss Reduction
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Solution Overview
Problem
The challenge is to reduce energy loss in power adapters without increasing their overall size, particularly in high-power density applications where heat dissipation becomes a bottleneck due to increased switching losses in power transistors.
Innovation Solution
A converter and control method that monitors the current on a transformer to determine when it reaches a specified current threshold, triggering the main power transistor to turn on at a valley voltage, thereby minimizing energy loss without adding external components or increasing the adapter's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an auxiliary winding of a transformer is added to monitor voltage and an RC circuit is used to generate delay duration, then the switching loss of the power transistor can be reduced by turning on at valley voltage, but the peripheral circuit of the power transistor chip becomes complex and the overall size of the power adapter is increased
Solution Approach 1:
The patent merges the voltage monitoring function and delay generation function into the existing transformer and controller. The controller uses the transformer's existing windings to obtain voltage information and generates the delay duration internally without requiring external RC circuits or auxiliary windings, thus reducing peripheral circuit complexity while maintaining valley voltage switching capability
Solution Approach 2:
The controller performs self-service by generating the delay duration internally based on resonance period detection, eliminating the need for external RC circuits. The system uses its own resources (controller processing capability and existing transformer windings) to achieve voltage monitoring and timing functions
2Power
If higher power density is achieved by increasing power in the same size, then the power adapter meets miniaturization requirements, but the loss caused by the power transistor increases and heat dissipation becomes a bottleneck
Solution Approach 1:
The patent changes the switching timing parameter by detecting the valley voltage of the power transistor and turning it on at this optimal moment. This parameter optimization reduces switching losses, enabling higher power density without proportionally increasing power transistor losses and heat dissipation
Data Source
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AI summary
This application provides a converter, a converter control method, and a power adapter. The converter includes: an input DC power supply, a main power transistor, an auxiliary power transistor, a first capacitor, a transformer, and a controller. The first capacitor is connected in series to the transformer to form a series circuit. The series circuit is connected in parallel to the auxiliary power transistor. A source of the main power transistor is connected to a drain of the auxiliary power transistor. A source of the auxiliary power transistor is connected to another electrode of the input DC power supply. An input negative electrode of the input DC power supply is grounded. The controller is configured to: monitor a value of a current on the transformer to obtain a quantity of times that the value of the current on the transformer reaches a specified current threshold, and when the quantity of times that the value of the current on the transformer reaches the specified current threshold is N, control the main power transistor to be turned on, where N is a positive odd number. The converter provided in this application can reduce an energy loss of the main power transistor, to reduce an energy loss of power density without increasing an overall size of the power adapter.