SMPS Miller Plateau Sensing for Zero-Voltage Switching
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Solution Overview
Problem
Existing switched-mode power supplies (SMPS) require excess components to determine the voltage across its switches, increasing the PCB footprint and complexity.
Innovation Solution
A switched-mode power supply (SMPS) that includes a reactive circuit and a control circuit to short-circuit a voltage across a first switch based on a drive voltage, measures the duration of a Miller plateau in the emerging waveform of the drive voltage, and operates the SMPS depending on this duration to determine the voltage without additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage across switches is determined using traditional methods, then voltage measurement is achieved, but PCB footprint and component quantity increase
Solution Approach 1:
The patent uses the Miller plateau duration as an intermediary parameter to indirectly determine the voltage across the switch. Instead of directly measuring the drain-source voltage which would require additional components, the control circuit measures the duration of the Miller plateau in the gate-source voltage waveform, which correlates with the switch voltage. This intermediary measurement approach eliminates the need for additional voltage sensing components across the switch.
Solution Approach 2:
The control circuit utilizes its existing drive terminal and waveform measurement capabilities to self-determine the switch voltage. By analyzing the Miller plateau duration from the drive voltage waveform that the control circuit already generates and monitors, the system performs voltage determination using its own internal resources without requiring external measurement devices or additional PCB real estate.
2Measurement precision
If voltage across switches is determined using traditional methods, then voltage measurement is achieved, but device complexity increases
Solution Approach 1:
The Miller plateau duration serves as an intermediary that translates switch voltage information into a measurable time parameter. The control circuit measures this duration and uses it to infer the voltage across the switch, avoiding the need for additional voltage sensing components, dividers, or measurement circuits that would increase device complexity.
Solution Approach 2:
The patent replaces physical voltage measurement mechanisms (such as voltage dividers, sensing resistors, or additional measurement circuits) with a temporal measurement approach. By substituting direct voltage sensing with Miller plateau duration measurement, the system eliminates the mechanical/electrical measurement infrastructure while achieving the same voltage determination function through timing analysis.
3Loss of energy
If Miller plateau duration is minimized, then zero-voltage switching efficiency is improved, but switch voltage stress increases
Solution Approach 1:
The control circuit measures the Miller plateau duration and uses this information as feedback to regulate the conduction time of the first switch. By adjusting the conduction time based on the measured Miller plateau duration, the system optimizes the balance between achieving zero-voltage switching (minimizing switching losses) and managing switch voltage stress, ensuring efficient operation while protecting the switch from excessive voltage stress.
Data Source
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AI summary
Disclosed is a switched-mode power supply, SMPS (1, 1A, 1B), comprising a reactive circuit (11); a first switch (12, S1), interposed between the reactive circuit (11) and a ground electric potential of the SMPS (1, 1A, 1B), and configured to short-circuit a voltage (VDS) across the first switch (12, S1) in accordance with a first drive voltage (VGS) applied to the first switch (12, S1); and a control circuit (14), multi-connected to a drive terminal of the first switch (12, S1), and configured to apply the first drive voltage (VGS) to the first switch (12, S1) in accordance with a conduction time to short-circuit the voltage (VDS) across the first switch (12, S1); measure a duration (31, t) of a Miller plateau (3) in an emerging waveform of the first drive voltage (VGS); and operate the SMPS (1, 1A, 1B) in dependence of the measured duration (31, t) of the Miller plateau (3). This enables determining the voltage (VDS) across the first switch (12, S1) without requiring any excess components.