Comb Waveform Oscillator Circuit for Ultra-Low Short-Circuit Current
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Solution Overview
Problem
Low frequency oscillators in small, portable devices face challenges in minimizing short-circuit current, which limits their ultra-low power operation due to slow signal transitions in sawtooth waveforms, leading to high current consumption and increased quiescent current.
Innovation Solution
A comb waveform generator circuit is used to convert slow sawtooth waveforms into fast edge comb waveforms, reducing short-circuit current by employing a PMOS transistor to generate a fast edge rate, thereby minimizing additional current consumption beyond conventional circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a sawtooth waveform is used in a low frequency oscillator, then the oscillator can operate at low frequency, but the slow rise time of the sawtooth waveform causes high short-circuit current consumption
Solution Approach 1:
The patent introduces a comb waveform generator as an intermediary circuit between the sawtooth waveform source and the oscillator core. This generator converts the slow-rising sawtooth waveform into a comb waveform with sharp, fast edges. The intermediary transformation allows the system to maintain low-frequency operation while eliminating the high current consumption caused by slow signal transitions, as the comb waveform's rapid edges minimize the duration of short-circuit current in CMOS inverters
2Use of energy by moving object
If the rise time of the waveform is increased to reduce short-circuit current, then current consumption decreases, but the oscillator frequency becomes too low for practical applications
Solution Approach 1:
The patent changes the temporal parameter of the waveform by generating a comb waveform with multiple sharp edges within each sawtooth cycle. Instead of uniformly increasing or decreasing the rise time, the invention transforms the waveform shape to have concentrated, fast transitions at specific moments (the comb teeth) while maintaining the overall low-frequency envelope. This parameter transformation allows fast signal edges for low current consumption while preserving the low operating frequency needed for portable devices
Data Source
AI summary
In described examples, a sawtooth waveform generator generates a sawtooth waveform having a first rise time. A comb waveform circuit has a power terminal coupled to receive the sawtooth waveform from an output of the sawtooth waveform generator. The comb waveform circuit generates a comb waveform in response to the sawtooth waveform. The comb waveform has a second rise time that is faster than the first rise time.