Variable Frequency Modulator Gain Linearity Control
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Solution Overview
Problem
Conventional variable frequency pulse width modulators experience non-linear modulator gain, leading to regulator design challenges such as large overshoots, inconsistent dynamic response, and non-linear AC response due to increasing gain with switching frequency, which worsens with larger load steps and repetitive transients.
Innovation Solution
A linearity controller is introduced to compensate for gain changes in response to switching frequency variations, maintaining gain linearity and reducing ringback by adjusting the slew rate of control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If variable frequency operation is used to achieve fast dynamic response, then dynamic response speed is improved, but modulator gain linearity deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the modulator gain is continuously monitored and adjusted based on the switching frequency. A gain control circuit receives the switching frequency signal and dynamically adjusts the modulator gain to maintain linearity across the frequency range, thus resolving the contradiction between fast dynamic response and gain linearity.
Solution Approach 2:
The patent changes the modulator gain parameter as a function of switching frequency. By making the gain a variable parameter that adapts to frequency changes, the system maintains linear modulator characteristics even during variable frequency operation, thereby preserving both fast dynamic response and gain linearity.
2Speed
If switching frequency is increased to improve dynamic response, then response time is reduced, but modulator gain increases causing large overshoots
Solution Approach 1:
The patent applies preliminary anti-action by preemptively adjusting the modulator gain downward when switching frequency increases. The gain control circuit detects frequency increases and compensates before the overshoot occurs, preventing the harmful effect rather than correcting it afterward.
Solution Approach 2:
A feedback loop continuously monitors the switching frequency and dynamically adjusts the modulator gain to prevent overshoots. When frequency increases are detected, the feedback mechanism reduces gain proportionally, maintaining stable output and preventing the large overshoots that would otherwise occur.
3Speed
If conventional variable frequency modulation is used, then fast dynamic response is achieved, but inconsistent dynamic response occurs during repetitive load transients
Solution Approach 1:
The patent uses feedback to continuously adjust the modulator gain based on real-time switching frequency measurements. This ensures that during repetitive load transients, the gain is consistently adjusted to maintain linear operation, resulting in consistent dynamic response characteristics across multiple transient events.
Solution Approach 2:
The patent makes the modulator gain dynamic rather than fixed, allowing it to adapt to changing operating conditions. The gain control circuit dynamically adjusts the gain parameter in response to frequency variations, ensuring consistent dynamic response behavior across different load transient scenarios.
Data Source
AI summary
A variable frequency modulator including a compensation network, first and second pulse control networks and a linearity controller. The compensation network is configured to provide a compensation signal indicative of an output load condition. The first pulse control network is configured to initiate pulses on a pulse control signal and to adjust operating frequency based on changes of the compensation signal. The second pulse control network is configured to terminate the pulses on the pulse control signal based on a predetermined timing parameter. The linearity controller is configured to adjust timing of terminating the pulses based on a predetermined steady state operating frequency and an actual operating frequency to maintain modulator gain at a constant level.