Valley Detecting Circuit for Switching Device Voltage
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Solution Overview
Problem
Conventional methods for reducing switching loss in high-frequency switching mode power supplies rely on differentiators to detect the minimum voltage across power switches, which is inefficient and requires alternative approaches to achieve precise timing for minimizing switching loss.
Innovation Solution
A valley detecting circuit and method that produces a detection voltage proportional to the voltage across the switching device, clamps it, level shifts it, and compares it to determine the valley, allowing precise timing for turning on the power switch without using differentiators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If differentiators are used to detect the minimum voltage across the power switch, then the valley detection can be achieved, but the circuit complexity increases and the reliability decreases
Solution Approach 1:
The patent extracts and eliminates the differentiator component from the conventional valley detection circuit. By removing this complex component and replacing it with a simplified capacitor-based voltage sampling and comparison mechanism, the circuit achieves valley detection without the complexity and reliability issues associated with differentiators.
Solution Approach 2:
The patent changes the detection parameter from derivative-based (conventional differentiator output) to direct voltage comparison. By monitoring the voltage across the switch directly and comparing it with a reference voltage, the system achieves accurate valley detection through parameter transformation rather than mathematical differentiation.
2Measurement precision
If differentiators are used to detect the minimum voltage across the power switch, then the valley detection can be achieved, but the switching loss reduction becomes less effective
Solution Approach 1:
The patent implements preliminary voltage sampling and comparison actions before the power switch is turned on. By detecting the valley point in advance through the simplified circuit and generating a detection signal that triggers the switch turn-on at the optimal moment, the system minimizes switching loss by ensuring the switch transitions occur precisely when the voltage is at its minimum.
3Weight of moving object
If higher switching frequency is implemented, then the size and weight of the power supply decrease, but the switching loss increases
Solution Approach 1:
The patent implements a feedback mechanism where the valley detection circuit continuously monitors the voltage across the power switch and generates turn-on signals based on real-time voltage conditions. This feedback control ensures that even at higher switching frequencies, the switch is turned on precisely at voltage valleys, thereby minimizing switching loss while allowing the use of smaller, lighter magnetic components.
Data Source
AI summary
A valley detecting circuit and method are provided for a voltage across a switching device, which detect a voltage across the switching device to produce a first voltage proportional to the voltage across the switching device, clamp the first voltage to produce a second voltage, level shift the second voltage to produce a third voltage, and compare the second voltage with the third voltage to determine a valley for the first voltage.