Hysteretic Power Converter Controller Mode Transition
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Solution Overview
Problem
Existing power converter controllers face challenges in accurately controlling the transition between critical conduction mode (CRM) and discontinuous conduction mode (DCM) due to distortion in current output, particularly during mode transitions, which can lead to increased costs and noise interference in digital and analog implementations, respectively.
Innovation Solution
A mixed signal implementation that combines analog and digital circuitry to generate the calculated discontinuous conduction time (TDCM) using an analog timer and measure thresholds with a low-resolution digital counter, allowing real-time determination of the operating mode and reducing distortion by ignoring the first valley of the voltage waveform during DCM operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a power converter controller locks the power converter in either CRM or DCM operation mode to prevent mode transitions, then distortion in current output is reduced, but operational efficiency is compromised because the controller cannot dynamically adapt to optimal operating conditions
Solution Approach 1:
The controller dynamically determines operating mode (CRM or DCM) for each switching cycle based on real-time comparison of actual TDCM with a threshold value, rather than locking into a fixed mode. This dynamic adaptation allows the system to achieve both low distortion through accurate mode control and high efficiency through optimal operating point selection
Solution Approach 2:
The controller uses feedback from the actual TDCM measurement (derived from valley detection of the drain voltage waveform) to adjust mode selection for the next switching cycle. This closed-loop control enables precise current output by comparing measured TDCM against threshold and dynamically switching modes accordingly, while maintaining efficiency through adaptive operation
2Measurement precision
If a digital implementation is used to calculate TDCM with high precision, then measurement accuracy is improved, but cost and noise interference increase
Solution Approach 1:
The patent introduces an intermediary analog timer circuit that measures TDCM by charging a capacitor through a current source, converting the time measurement into a voltage signal. This analog intermediary provides sufficient measurement precision for mode determination without requiring complex digital counters, thereby reducing noise interference and cost while maintaining adequate measurement accuracy
Solution Approach 2:
The patent replaces complex digital timing circuits with a simpler analog timing mechanism using RC charging. The analog timer generates a voltage proportional to TDCM duration, which is then compared against a threshold voltage corresponding to the TDCM threshold. This substitution eliminates the need for high-resolution digital counters and associated digital noise, achieving cost-effective precision measurement
Data Source
AI summary
At least some aspects of the present disclosure provide for a circuit. In one example, the circuit includes a logic circuit having multiple inputs and multiple outputs, a calculated discontinuous conduction (DCM) (TDCM) timer having an input coupled to one of the logic circuit outputs and an output coupled to one of the logic circuit inputs, an on-time (TON) timer having an input coupled to one of the logic circuit outputs and an output coupled to one of the logic circuit inputs, and a hysteresis timer having an input coupled to one of the logic circuit outputs and multiple outputs coupled to multiple of the logic circuit inputs.