PWM Output Stage Pulse Remodulation for Saturation Control
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Solution Overview
Problem
High-frequency electronic switching apparatuses face challenges in controlling output saturation due to limitations in rise and fall times of switching signals, leading to overvoltages and undervoltages, which can damage components and result in electromagnetic emissions that fail compatibility tests.
Innovation Solution
A pulse-remodulator circuit is introduced between the modulator and the switching-type output power stage to measure and adjust pulse widths, ensuring the output pulse width is either equal to a minimum value or proportional to the input pulse width, thereby maintaining modulation index and preventing saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high switching frequency is used, then filter dimensions are reduced and regulation performance is improved, but control of output duty cycle becomes difficult due to rise/fall time limitations
Solution Approach 1:
The patent applies preliminary action by measuring the pulse width of the input signal before it reaches the switching output stage and comparing it with a predetermined minimum value. Based on this advance measurement, the system determines whether remodulation is needed and adjusts the pulse width accordingly, preventing saturation before it occurs. This proactive approach allows high-frequency operation while maintaining proper duty cycle control.
2Productivity
If pulse width is reduced for high-frequency operation, then switching frequency increases, but output saturation occurs due to minimum rise/fall time requirements
Solution Approach 1:
The patent implements feedback by measuring the actual pulse width of the input signal and using this information to control the remodulation process. The measurement unit continuously monitors pulse width, and based on this feedback, the system adjusts the pulse width through remodulation when necessary. This closed-loop feedback mechanism ensures that the output stage operates reliably without saturation even at high switching frequencies.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the pulse width parameter of the PWM signal. When the measured pulse width is below the minimum required value, the system increases it to the minimum value or a proportional value, thereby changing the pulse width parameter to prevent saturation while maintaining high-frequency operation.
3Reliability
If rise/fall times are limited by parasitic inductance, then component damage is prevented, but electromagnetic emissions fail compatibility tests
Solution Approach 1:
The patent applies dynamics by making the pulse width adjustable rather than fixed. The system dynamically adapts the pulse width based on the measured input signal characteristics, increasing it when necessary to prevent saturation. This dynamic adjustment allows the system to maintain component protection while optimizing electromagnetic emissions performance through proper pulse width control.
Data Source
AI summary
An embodiment apparatus comprises a switching-type output power stage, a modulator circuit configured for carrying out a pulse-width modulation and converting an electrical input signal into an input signal pulsed between two electrical levels, having a mean value proportional to the amplitude of the input signal, and a circuit arrangement for controlling saturation of an output signal supplied by the switching-type output power stage. The circuit arrangement comprises a pulse-remodulator circuit, between the output of the modulator circuit and the input of the switching-type output power stage, that is configured for supplying, as a driving signal to the switching-type output power stage, a respective modulated signal pulsed between two electrical levels, measuring a pulse width as pulse time interval elapsing between two consecutive pulsed-signal edges of the pulsed input signal, and, if the measurement indicates that the latter is below a given minimum value, remodulating the pulsed input signal.