Variable Current Bleed Unit for USB-PD Audio Noise
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Solution Overview
Problem
Buck converters used in USB-PD power delivery systems generate audible noise when the pulse frequency modulation (PFM) frequency drops into the audible range due to varying load currents, causing vibrations in inductors and capacitors.
Innovation Solution
Implementing a variable current bleed unit that adjusts the current load on the voltage regulator based on the PFM signal frequency to maintain the frequency above the audible range, using either a digital or analog circuit to manage the bleed current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PFM frequency is reduced to improve power efficiency at light loads, then power consumption is reduced, but audible noise is generated due to vibrations in inductors and capacitors
Solution Approach 1:
The patent applies preliminary anti-action by introducing a bleed current that proactively counteracts the frequency reduction before audible noise can occur. The bleed current is specifically designed to prevent the PFM frequency from dropping into the audible range (20Hz-20kHz) by maintaining a minimum load on the voltage regulator, thus eliminating the harmful vibrations in inductors and capacitors before they can be generated.
Solution Approach 2:
The patent changes the electrical parameter (bleed current) to control the PFM frequency. By dynamically adjusting the bleed current based on the detected PFM frequency, the system modifies the load characteristics of the voltage regulator, which in turn controls the switching frequency to remain above the audible threshold while still allowing power efficiency improvements at light loads.
2Object-generated harmful factors
If PFM frequency is increased to avoid audible range, then audible noise is eliminated, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the bleed current adjustable rather than fixed. The system dynamically adapts the bleed current magnitude based on real-time monitoring of the PFM frequency and load conditions. This allows the frequency to be kept above the audible threshold only when necessary, and reduces the bleed current when higher frequencies are not needed, thereby optimizing power consumption while eliminating audible noise when required.
Solution Approach 2:
The patent implements feedback by continuously monitoring the PFM frequency and using this information to adjust the bleed current. The frequency detection circuit provides feedback about the current operating frequency, and this feedback is used by the control logic to modulate the bleed current, creating a closed-loop system that automatically maintains frequency above the audible range while minimizing power consumption.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Prevents audible noise generation while conserving power by ensuring the PFM frequency remains above the audible range, thus improving user experience and reducing unnecessary power consumption.
Implementation Method 1
a voltage regulator configured to generate a power supply voltage based on a pulse frequency modulation (PFM) signal
Implementation Method 2
a variable current bleed unit configured to generate a variable current bleed load on the voltage regulator based on a frequency of the PFM signal
Data Source
AI summary
In an embodiment of the techniques presented herein, a universal serial bus power delivery (USB-PD) power adaptor includes a USB port, and a USB controller configured to deliver power to the USB port, wherein the USB controller includes a voltage regulator configured to generate a power supply voltage based on a pulse frequency modulation (PFM) signal, and a variable current bleed unit configured to generate a variable current bleed load on the voltage regulator based on a frequency of the PFM signal to maintain the frequency of the PFM signal above an audible frequency range.