Valley-Fill RF Power Converter for High Power Factor Output
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Solution Overview
Problem
Traditional power converting systems that generate RF power from AC line voltage have poor power factor efficiency, making them ineffective for applications requiring high RF output and are not cost-effective.
Innovation Solution
A power converting system that includes a Valley Fill rectifier and a phase shifter-controlled RF power amplifier, operating between 100 kHz and 100 MHz, specifically designed to maximize AC line to RF power conversion efficiency and power factor, while minimizing heating of MOSFET devices, thus extending their lifespan and meeting international standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a full wave bridge rectifier is used to generate RF power from AC line voltage, then the system can provide RF power output, but the power factor is poor and conversion efficiency is low
Solution Approach 1:
The patent changes the operating parameters of the rectifier by using Valley Fill rectification instead of traditional full-wave bridge rectification. This parameter change in the rectification method improves power factor while maintaining RF power output capability, directly resolving the contradiction between energy loss and productivity.
2Loss of energy
If peak output voltage is delivered to maximize RF power, then power conversion efficiency improves, but MOSFET heating increases and device lifespan decreases
Solution Approach 1:
The patent applies preliminary action by pre-positioning the MOSFET switching events to occur at optimal moments in the AC cycle (at voltage valleys). This timing optimization allows the system to achieve high power conversion efficiency while preventing excessive current stress and heating on the MOSFETs, thereby extending their lifespan.
Solution Approach 2:
The patent converts the potentially harmful effect of high peak currents into a benefit by strategically timing the MOSFET switching to occur when AC voltage is at its minimum. This transforms what would normally be a stress condition into an opportunity for efficient power transfer with reduced thermal stress on components.
3Reliability
If standard AC line current protection ratings are used, then system safety is maintained, but maximum RF output power cannot be achieved
Solution Approach 1:
The patent changes the current waveform parameters through Valley Fill rectification, transforming the current profile to have lower peak values and improved sinusoidal characteristics. This parameter change allows the system to deliver higher average RF power while keeping peak currents within standard AC protection device ratings, thus maintaining safety while increasing power output.
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
The system achieves maximum RF output power within standard AC line current ratings, reduces heating of MOSFET devices, and provides a cost-effective solution for applications like dryers, medical devices, and radio transmitters by optimizing power factor and efficiency.
Implementation Method 1
the RF power amplifier can be powered by a Valley Fill rectifier
Implementation Method 2
a power converting system that converts an alternating current (AC) line voltage to radio frequency (RF) energy
Implementation Method 3
a phase shifter to control output of a RF power amplifier
Implementation Method 4
minimize heating of a RF power metal-oxide-semiconductor field-effect transistor (MOSFET) or other switching devices
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A power converting system that includes: a rectifier configured to convert an input voltage into a output voltage and including an output node that is coupled to floating ground; a radio frequency (RF) power amplifier coupled to the rectifier and configured to generate a load voltage based on an RF clock and the output voltage; a detector coupled to the RF power amplifier and configured to detect the load voltage of the RF power amplifier; an integrator coupled to the detector and configured to generate a direct current (DC) voltage based on the detected load voltage; and a controller coupled to the integrator and configured to, based on the DC voltage, generate a control signal to adjust one or more features of the RF power amplifier is disclosed.