Tickle Pulse Injection for PWM Controller Frequency Control
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Solution Overview
Problem
Switching power supplies in audio applications experience poorly controlled switching during low-load conditions, leading to undesirable audible artifacts and performance issues like 'holes' in audio reproduction due to reduced switching frequencies or complete cessation of switching.
Innovation Solution
A power supply system that includes a tickle pulse generator to inject pulses into the PWM controller, ensuring it generates PWM pulses at a minimum, preferably supersonic, switching frequency, and adjusts pulse width and shape to maintain a near-constant output voltage, thereby preventing audible artifacts and resonances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power supply operates in low-load condition without tickle pulses, then energy consumption is reduced, but switching frequency becomes uncontrolled and produces audible artifacts
Solution Approach 1:
The tickle pulse generator introduces periodic test pulses at a supersonic frequency (above 20kHz) to the PWM controller during low-load conditions. These periodic pulses force the controller to maintain regular switching action at a controlled frequency, preventing the uncontrolled low-frequency switching that causes audible artifacts, while still allowing the power supply to operate in energy-saving low-load mode.
2Loss of energy
If the switching frequency is reduced during low-load condition, then energy loss is decreased, but switching control becomes poor and performance deteriorates
Solution Approach 1:
The tickle pulse generator provides a feedback mechanism by continuously monitoring the need for switching action and injecting corrective pulses when detected. The generator responds to the power supply's load conditions and controller state, ensuring that switching frequency remains within acceptable bounds even during low-load operation, thereby maintaining reliable switching control while allowing energy efficiency improvements.
3Reliability
If tickle pulses are injected into the PWM controller, then switching frequency is maintained at minimum level, but device complexity increases
Solution Approach 1:
The tickle pulse generator acts as an intermediary component between the power supply's control system and the PWM controller. It provides a simple pulse injection mechanism that mediates the interaction between the controller and power switches, maintaining switching frequency control without requiring complex modifications to the existing PWM controller or power supply architecture.
Data Source
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AI summary
A power supply injects a series of "tickle" pulses into a pulse width modulated (PWM) controller to induce the controller to generate PWM pulses at a minimum switching frequency, preferably one that is super-sonic (especially for audio applications). The switching frequency may also be selected or controlled such that it avoids resonances in the power supply. The "tickle" pulses may be clocked by the same clock that times the PWM controller, and they may be shaped to help ensure that the power supply maintains some regulation during low-load conditions.