RF Power Supply PWM Control for Continuous Overmodulation
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Solution Overview
Problem
The existing RF band power supply devices face a challenge in maintaining continuous pulse width modulation due to the jump phenomenon, where the pulse width shifts to a duty ratio of 50% in overmodulation control, leading to discontinuous pulse widths, which affects efficiency and output power.
Innovation Solution
A pulse width modulation control method and RF band power supply device that uses a modulation wave frequency and a carrier wave frequency, where the carrier wave frequency is an even number times higher than the modulation wave frequency, and the modulation factor is controlled to prevent the pulse width from shifting to a duty ratio of 50%, ensuring continuity by setting an upper limit value for the modulation factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If overmodulation control is performed to reduce the number of intersections between modulation wave and carrier wave, then switching loss is reduced and power efficiency is improved, but the pulse width becomes discontinuous due to jump phenomenon
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the carrier wave frequency based on the modulation factor. When the modulation factor increases toward the overmodulation region, the carrier wave frequency is increased to prevent the pulse width from jumping to 50% duty ratio. This dynamic parameter adjustment maintains continuous pulse width modulation while allowing operation in the overmodulation region for reduced switching loss.
2Power
If the modulation factor is increased to enhance the fundamental wave component ratio and output power, then power efficiency is improved, but the pulse width shifts to duty ratio of 50% causing discontinuity
Solution Approach 1:
The patent implements feedback control by monitoring the modulation factor and adjusting the carrier wave frequency accordingly. When the modulation factor approaches values that would cause pulse width jump to 50% duty ratio, the system increases the carrier wave frequency to maintain continuous pulse width modulation. This feedback mechanism enables operation at high modulation factors for enhanced output power while preventing discontinuity.
3Productivity
If the number of switching operations is reduced to minimize switching loss, then efficiency is improved, but the pulse width becomes discontinuous
Solution Approach 1:
The patent resolves this contradiction by dynamically changing the carrier wave frequency parameter in response to modulation factor variations. This allows the system to operate with fewer switching operations for improved efficiency while maintaining continuous pulse width through adaptive frequency adjustment that prevents the jump phenomenon.
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 the jump phenomenon, maintains continuous pulse width modulation, increases output power by enhancing the fundamental wave component ratio, and reduces switching loss by minimizing the number of switching operations.
Implementation Method 1
a single-phase PWM inverter configured to perform pulse width modulation on a bridge circuit that switches on and off semiconductor switching elements
Implementation Method 2
The single-phase PWM inverter is used as a power conversion device for performing PWM control on a bridge circuit that switches on and off semiconductor switching elements of the bridge circuit to convert a DC voltage in a DC power source into an AC voltage
Implementation Method 3
a low-pass filter circuit configured to remove a harmonic component in an AC output of the single-phase PWM inverter to output a sine wave
Data Source
AI summary
A pulse width modulation control according to the present invention is performed such that, when changing a modulation rate of a modulation wave, the modulation rate is continuously changed from a normal modulation region to an overmodulation region, and, the modulation rate is controlled not to be discontinuous between the normal modulation region and the overmodulation region. In the overmodulation region, limiting the modulation rate α prevents a jump phenomenon in pulse width from occurring and the continuity of the pulse width from disappearing due to the jump phenomenon. The upper limit αupper of the modulation rate α is a threshold at which the pulse width of a PWM pulse signal jumps to a duty ratio of 50%, and limits the modulation rate α to less than the threshold.