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The Secret of the Relaxation Oscillator: Why Does It Produce a Unique Waveform?
In electronics, a relaxation oscillator is a nonlinear electronic oscillator circuit capable of producing a non-sinusoidal repetitive output signal, such as a triangle or square wave. This type of circuit consists of a feedback loop with a switching device such as a transistor, comparator, relay, op amp, or negative resistance device (such as a tunnel diode) that continuously charges a capacitor or inductor through a resistance. Until a certain threshold is reached, and then discharge is performed. The period of the oscillator mainly depends on the time constant of the capacitor or inductor circuit.
"The relaxation oscillator is a powerful tool for producing discontinuously changing repetitive waveforms. Its characteristic is that it relies on the process of rapid charge and discharge to produce signals."
Relaxation oscillators operate on a completely different principle than other types of electronic oscillators, such as harmonic or linear oscillators. Although relaxation oscillators are suitable for the low frequency range, their applications include flashing lights (such as turn signals) and electronic buzzers, voltage controlled oscillators (VCOs), inverters, switching power supplies, dual-slope analog-to-digital converters and function generators, etc. What's more noteworthy is that the term "relaxation oscillator" is not limited to electrical engineering. It is widely used in many scientific fields to describe those dynamic systems that can produce nonlinear oscillations.
Relaxation oscillations usually consist of two processes that alternate on different time scales: one is a long relaxation time, during which the system tends to an equilibrium point, and the other is a short impulse time, when the equilibrium point changes occur. I hope you have thought about why these systems are ubiquitous in nature?
The history of electronic relaxation oscillators
One of the early circuits for relaxation oscillators was the astable multi-oscillator, invented by Henry Abraham and Eugene Bloch during World War I using vacuum tubes. By 1920, Balthasar van der Poel distinguished relaxation oscillations from harmonic oscillations for the first time, and then created the concept of relaxation oscillators and designed the famous Van der Poel oscillator model.
"In the world of relaxation oscillators, the process of charging and discharging is like stress relief in machinery. This is the natural and beautiful thing about it."
Relaxation oscillators can be divided into several types, including sawtooth, sweep, or playback oscillators. The stored energy of these oscillators is slowly charged but quickly discharged through the switching device, so that only a small amount of energy appears in the output waveform. Contains a "ramp". Another type is the astable multi-oscillator. The capacitor of this oscillator also charges and discharges slowly, so its output waveform consists of increasing and decreasing slopes.
Wide range of applications
The application scope of relaxation oscillators covers the generation of low-frequency signals, such as flashing lights and electronic buzzers commonly found in electronic devices. In the vacuum tube era, they were widely used as time bases in electronic organs and oscilloscopes. With the development of microelectronics technology, today's relaxation oscillators are generally constructed using dedicated integrated circuits (such as 555 timer chips).
Relaxation oscillators are widely used mainly because their design is relatively simple and does not require inductive components like LC oscillators, making them easier to fabricate on integrated circuits. However, the disadvantages of relaxing the oscillator are greater phase noise and poor frequency stability.
As for the implementation of the relaxation oscillator, there are many methods to choose from: including using a 555 timer, and many off-the-shelf implementations are also designed using comparators as components, all of which are designed to capture and generate That unique waveform.
The essence of a relaxation oscillator is its ability to simulate various natural phenomena, including the eruption of a volcano, the biological signals of nerve cells or even the rhythm of a biological heartbeat. Because of this, as technology advances, relaxation oscillators continue to play a vital role in many emerging fields. Are you curious about how these complex but wonderful systems will continue to impact our lives?
