Hysteretic Power Converter Synchronization via Disturbance Injection
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Solution Overview
Problem
Hysteretic switching power converters face challenges in synchronizing their switching frequency to a desired value, either higher or lower than the free running frequency, with existing methods often requiring complex Phase Lock Loop circuits, experiencing slow locking speeds, and being prone to noise and phase errors, especially during transitions from Discontinuous to Continuous Conduction Mode.
Innovation Solution
A method involving the injection of a periodic disturbance signal into specific nodes of the feedback network to synchronize the power converter's switching frequency, using an open-loop approach that adjusts the amplitude and duty cycle to minimize jitter and power consumption, allowing quick transitions between modes without affecting the regulated output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Phase Lock Loop circuits are used to regulate switching frequency, then frequency control is achieved, but device complexity increases and locking speed decreases
Solution Approach 1:
The patent extracts the frequency control function from the complex PLL circuit and implements it through a simplified hysteretic comparator mechanism. The switching frequency is naturally regulated by the hysteresis window and feedback network without requiring separate frequency control circuits, thereby reducing device complexity while maintaining reliable frequency control.
Solution Approach 2:
The hysteretic comparator serves multiple functions simultaneously: it regulates output voltage, controls switching frequency, and provides mode detection. This multi-functionality eliminates the need for dedicated frequency control circuits, resolving the contradiction between reliability and complexity.
2Reliability
If Phase Lock Loop circuits are used to regulate switching frequency, then frequency control is achieved, but locking speed becomes slow
Solution Approach 1:
The patent implements preliminary frequency determination through the hysteresis window configuration and feedback network design. The switching frequency is pre-established by the hysteresis levels and component values, allowing immediate operation without requiring time-consuming locking procedures associated with PLL circuits.
3Reliability
If complex frequency control circuits are used, then frequency regulation is achieved, but power consumption increases
Solution Approach 1:
The hysteretic comparator performs frequency regulation as part of its voltage control function, eliminating the need for separate frequency control circuits. This multi-functionality reduces overall power consumption while maintaining reliable frequency regulation.
4Device complexity
If hysteretic control is used, then circuit simplicity is maintained, but switching frequency varies with operating conditions
Solution Approach 1:
The patent implements self-service frequency stabilization where the feedback network and hysteresis mechanism automatically adjust to maintain stable switching frequency. The system uses its own operating conditions (output voltage, load current) to naturally regulate frequency without external control circuits, preserving simplicity while achieving stability.
Data Source
AI summary
A novel method to synchronize the switching frequency of hysteretic power converters is presented. The method includes the generation of a clock signal and the injection of a periodic disturbance signal operating at the frequency of the generated clock in the main loop of the converter to synchronize the hysteretic power converter to switch at the frequency of the clock.The presented approach provides significant advantages with respect to the more traditional means of utilizing Frequency Lock Loop, Phase Lock Loop or Delay Lock Loop circuits, mainly for its simplicity, faster locking and much reduced phase error.The switching frequency can be higher or lower than the free running frequency of the power converter provided that the free running frequency is close enough to the desired switching frequency.The method is presented for buck and boost hysteretic high frequency switching power converters.