Switching Converter Compensation Time Selection Circuit
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Solution Overview
Problem
Power factor correction converters experience high switching losses due to hard switching instances, particularly when the MOSFET operates under critical or continuous conduction modes, and existing methods to minimize these losses require additional power components, increasing size and cost.
Innovation Solution
A switching converter with a programmable controller that includes a compensation time selection circuit, which selects a compensation time based on a resistor value to ensure the power MOSFET turns on at its valley switching point, mitigating hard switching by compensating for the inherent delay in switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero current detection (ZCD) is used to trigger MOSFET switching, then the switching timing can be determined, but an inherent time delay occurs between zero current point and valley voltage point causing hard switching
Solution Approach 1:
The patent applies preliminary action by introducing a compensation time mechanism that anticipates the inherent delay between zero current detection and actual valley switching point. The controller pre-calculates and applies a compensation time value based on resistor feedback, allowing the MOSFET to be triggered at the correct timing to reach valley switching point, thereby eliminating hard switching losses while maintaining simple ZCD circuitry
2Loss of energy
If additional power components are added to minimize switching losses, then switching efficiency improves, but device size and cost increase
Solution Approach 1:
The patent implements self-service by utilizing the existing resistor component already present in the ZCD circuit to generate feedback current that indicates valley switching point timing. The controller uses this existing resistor feedback to determine compensation time and trigger MOSFET switching, eliminating the need for additional sensing components or complex circuits while achieving soft switching
Solution Approach 2:
The patent applies universality by making the resistor serve multiple functions: it is both part of the zero current detection circuit and the valley switching point sensing mechanism. The same resistor provides feedback current used for both ZCD operation and compensation time determination, thereby achieving soft switching without adding dedicated valley detection components
Data Source
AI summary
A switching converter is provided that includes a power MOSFET, a controller having a drive pin connected to a gate terminal of the power MOSFET, and a resistor connected to the gate terminal. A compensation time selection circuit is included that has compensation times stored therein. A compensation time is selected from the compensation times based on a value of the resistor and stored in the controller. The selected compensation time compensates for an inherent delay in switching the power MOSFET to an ON state after the power MOSFET receives a signal to switch to the ON state to allow the power MOSFET to switch to the ON state when a drain voltage of the power MOSFET's reaches its lowest value during a switching cycle.