Pulse Frequency Modulation Circuit for Precise Power Adapter Timing
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Solution Overview
Problem
Conventional power adapters are unable to control the zero crossing of current and the ON time of the MOS tube precisely, leading to imprecise timing for switching the operating status of the power adapter.
Innovation Solution
A pulse frequency modulation circuit comprising multipliers, dividers, and an adder is used to compute and output control signals for controlling the OFF/ON time of a transistor, enabling precise timing control of the power adapter's operating status through precise computation and modulation of the switching time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional zero-crossing detection method is used, then the power adapter can achieve critical operating mode, but the timing control precision of MOS tube ON time and zero crossing is insufficient
Solution Approach 1:
The patent replaces the conventional hardware-based zero-crossing detection mechanism with a software-based pulse frequency modulation circuit. The PFM circuit uses computational algorithms to calculate the precise ON time of the MOS tube based on input parameters, substituting the mechanical/electrical zero-crossing detection approach with a digital computation system that achieves higher timing precision without requiring complex hardware modifications
Solution Approach 2:
The patent changes the control parameter from zero-crossing detection timing to pulse frequency modulation parameters. By adjusting the frequency and duty cycle of control pulses generated by the PFM circuit, the system achieves precise control over MOS tube ON time and zero crossing timing, transforming the control approach from event-triggered (zero-crossing) to parameter-triggered (pulse frequency)
2Measurement precision
If default ON time is used for MOS tube, then the control is simple, but the switching timing of power adapter operating status cannot be controlled precisely
Solution Approach 1:
The patent introduces a pulse frequency modulation circuit as an intermediary between the control system and the MOS tube switching mechanism. This PFM circuit acts as a mediator that translates desired switching timing requirements into precise control pulse signals, enabling accurate timing control while maintaining operational simplicity through standardized interface connections
Solution Approach 2:
The patent implements preliminary calculation of switching timing parameters within the PFM circuit before actual MOS tube activation. The circuit pre-calculates the required ON time and zero-crossing timing based on input parameters, preparing precise control signals in advance, which eliminates the need for complex real-time adjustments during operation and maintains ease of use
Data Source
AI summary
Disclosed are a pulse frequency modulation circuit and a power adapter. The pulse frequency modulation circuit includes a first multiplier, a second multiplier, a third multiplier, a divider and an adder sequentially and electrically connected to one another. The second multiplier includes an output terminal connected to an input terminal of the divider, a first input terminal, and a second input terminal connected to an input terminal circuit of the adder. To prevent the uncertain timing of the critical operating status of the time control circuit detected by the conventional zero-crossing detection method, the pulse frequency modulation circuit and power adapter adopt the pulse frequency modulation circuit for computation and output a control signal to control the OFF/ON time of a transistor in the power adapter, so as to control the timing of the operating status of the power adapter precisely.