Please tell us about the principle of LC oscillation and the principle of LC oscillation circuit

It is very helpful to make a scintillation circuit composed of RC oscillation, analyze the principle, and learn the principle.

The LC oscillation circuit uses the energy storage characteristics of capacitance and inductance to convert electromagnetic energy alternately, that is to say, there will be a maximum and minimum value of electrical energy and magnetic energy, and there will be oscillation. However, this is only an ideal situation, in fact, all electronic components will have losses, and the energy will either be lost in the process of conversion between capacitance and inductance, or leak out of the outside, and the energy will continue to decrease.

The above is copied from the encyclopedia, but there is no explanation of the mechanism.

To put it simply, let's say that at the beginning, the capacitor has a forward voltage and the inductor current is 0. The capacitance voltage causes the forward current of the inductor to gradually increase, and at the same time it gradually decreases on its own, and when it decreases to 0, the forward current of the inductor increases to the maximum. This process is the conversion of capacitive energy into inductive energy.

Now the capacitor voltage is 0, the inductor current is the maximum, and the capacitor voltage is 0, this current will charge the capacitor, but it should be noted that the charging effect of the inductor forward current is that the reverse voltage of the capacitor gradually increases (draw a diagram to understand), and the forward current gradually decreases. When the current decreases to 0, the capacitor reverse voltage reaches its maximum. In this process, the inductor energy is converted into voltage energy.

The above is what happens in the half cycle of LC**, this moment is only the opposite direction of the starting voltage compared with the initial state, and the process is exactly the same.

If you still don't understand, think about the process of converting spring potential energy and particle kinetic energy into each other in a spring-particle simple harmonic vibration system in high school physics. LC** is also essentially a simple harmonic vibration, mathematically identical.

LC oscillation circuit.

LC oscillation circuit refers to the oscillation circuit composed of frequency selection network with inductor L and capacitor C, which is used to generate high-frequency sine wave signals, and the common LC sine wave oscillation circuits include transformer feedback LC oscillation circuit, inductance three-point LC oscillation circuit and capacitor three-point LC oscillation circuit. The radiated power of the LC oscillation circuit is proportional to the fourth power of the oscillation frequency, and in order for the LC oscillation circuit to radiate strong enough electromagnetic waves, the oscillation frequency must be increased and the circuit must have an open form.

How it works. The electrical disturbance generated at the moment of start-up is amplified by an amplifier composed of transistor V, and then the resonant frequency F0 is selected from many frequencies by the LC frequency selection loop. The signal is fed back to the base of the transistor through the mutual inductance coupling between the coils L1 and L2.

Let the instantaneous voltage polarity of the base be positive. The instantaneous polarity of the inverted set voltage is negative, according to the symbol of the same name of the transformer, it can be seen that the voltage polarity of the upper end of L2 is negative, and the voltage polarity of the feedback back base is positive, which satisfies the phase balance condition, and the signal that deviates from other frequencies of F0 does not meet the phase balance condition because of the additional phase shift, as long as the transistor current amplification coefficient B and the turns ratio of L1 and L2 are appropriate and the amplitude condition is met, the oscillation signal of frequency F0 can be generated.

RC oscillation circuit.

The RC oscillation circuit is a circuit consisting of a resistor R and a capacitor C, and is suitable for generating low-frequency signals. RC oscillation circuit, composed of RC frequency selection network, is suitable for low-frequency oscillation, and is generally used to generate low-frequency signals of 1Hz 1MHz (FO=1 2 RC). For RC oscillation circuits, increasing the resistance r can reduce the oscillation frequency, while increasing the resistance does not require increasing the cost. For LC oscillation circuit, the sine wave frequency is generally higher, and if the sine oscillation with lower frequency is generated, it is necessary to require the oscillation circuit to have a large inductance and capacitance, which not only the component is large, bulky, inconvenient to install, but also difficult to manufacture and costly.

Therefore, for sinusoidal oscillation circuits below 200kHz, RC oscillation circuits with a low oscillation frequency are generally used.

How it works. The RC oscillation circuit is first of all the initiation process; secondly, it enters the stage of stable oscillation; This is followed by the oscillation frequency, which is determined by the phase equilibrium condition. ja = 0, only at f 0 jf = 0

The phase equilibrium condition is satisfied, so the oscillation frequency f 0 = 1 2 rc.

The resistance of the frequency selection network can be changed by changing the position of the switch to achieve frequency coarse adjustment; The frequency can be fine-tuned by changing the size of the capacitor c. In addition, in terms of the conditions of initiation and stable oscillation, the starting conditions auf > are considered

1. Generally, it should be selected.

The rf is slightly larger by 2R1. If this ratio is too large, it will cause severe distortion of the oscillating waveform. The RC series-parallel sine wave oscillation circuit composed of op amps does not rely on the transistors inside the op amp to enter the nonlinear region to stabilize the amplitude, but achieves the purpose of amplitude stabilization by introducing negative feedback externally.

The LC oscillation module of the induction cooker is the core circuit of the induction cooker, and its working principle is the principle of LC parallel resonance, which continuously charges and discharges through the inductance coil and the oscillating capacitor to generate an oscillation waveform. where L is the inductance coil and C is the oscillating capacitance.

An LC oscillation circuit is a circuit that consists of an inductor L and a capacitor C that is used to generate a high-frequency sine wave signal. In many cases, LC oscillation circuits are also referred to as oscillator circuits, resonant circuits, resonant circuits, or tuned circuits. Common LC sine wave oscillation circuits include transformer feedback LC oscillation circuits and inductive three-point LC oscillation circuits and capacitor three-point LC oscillation circuits.

The radiated power of the LC oscillation circuit is proportional to the fourth power of the oscillation frequency, allowing the oscillating LC circuit to radiate sufficiently strong electromagnetic waves, the oscillation frequency must be increased, and the circuit is in the form of an open circuit. LC oscillators use an oscillating circuit (consisting of an inductor and a capacitor) that provides the positive feedback needed to maintain the oscillation of the electricity. As the name suggests, in this circuit, a charged capacitor (c) is connected to an uncharged inductor (l), as shown in the figure below.

The LC oscillation module of the induction cooker is the core circuit of the induction cooker, and its working principle is the principle of LC parallel resonance, which continuously charges and discharges through the inductance coil and the oscillating capacitor to generate an oscillation waveform. where L is the inductance coil and C is the oscillating capacitance.

The LC circuit is an oscillation circuit composed of an electric shirt macro sensition and a capacitor, and its oscillation principle is based on the exchange of energy between the inductor and the capacitor.

In LC circuits, when there is an electric charge present on the capacitor, it generates an electric field and stores electrical energy; Inductors, on the other hand, convert electrical energy into magnetic energy. When the charge on the capacitor flows through the inductance, the magnetic energy is converted back into electrical energy and stored in the capacitor. This periodic exchange of electrical and magnetic energy between inductors and capacitors or liters results in periodic oscillations of charge and voltage.

Specifically, when the charge on the capacitor reaches its maximum, the magnetic energy stored in the inductor is minimal, so the current of the inductor also reaches the maximum. And when the charge flows out of the capacitor, the magnetic energy in the inductor starts to increase and the current gradually decreases. When the charge on the capacitor flows out completely, the magnetic energy stored in the inductor is maximum, and the current is also zero.

At this point, the capacitor is recharged by the inductor and the above oscillation process is repeated.

Therefore, the oscillation frequency in an LC circuit depends on the parameters of the inductor and capacitor as well as the initial conditions.

An LC circuit is a circuit composed of inductors and capacitors, and its functions include:

1. Filtering: LC circuits can be used to filter out signals of specific frequencies, so that only the required frequencies pass through the circuit.

2. Tuning: The LC circuit can be adjusted to the resonance state, at this time it has a high impedance to a specific frequency, and a lower impedance to other frequencies, so as to achieve the role of frequency selection amplification or filtering.

3. Storing energy: Since both inductors and capacitors can store energy, LC circuits can be used to store electrical energy. In an AC circuit, electrical energy is converted between inductance and capacitance.

4. Time delay: LC circuits can introduce time delay, which is useful in some applications, such as making digital delay lines.

5. Generate oscillation: When the LC circuit is in a stable resonance state, it can generate periodic oscillation signals. This kind of oscillator is widely used in wireless communication, computer clocks and other fields.

Principle analysis of LC oscillation circuit:

The inductor and the capacitor are connected in parallel, and when the current generated by the capacitor is discharged, the inductor will block the current from passing through and convert the electric field into a magnetic field and store it. After the capacitor is discharged, the inductor will hinder the disappearance of the current, the magnetic field in the inductor is converted into an electric field, and the resulting current charges the other electrode of the capacitor; After the charging is completed, the capacitor begins to reverse discharge again; The energy that forms oscillations. If you don't take into account the loss of energy, this oscillation will continue forever.

In an LC oscillation circuit, the time to complete an oscillation is called a period, and the frequency refers to the number of times the energy oscillates per second in the circuit.

In the process of energy oscillation, there is a loss of energy, and if it is not replenished, this oscillation will slowly weaken until it disappears. In practical applications, we need to make energy replenishment of the LC oscillation circuit.

Oscillating circuits often require positive feedback. The following illustrates the principle of a capacitive three-point (Corbetz) oscillator.

The Corbetz oscillator is based on a common emission amplifier and a parallel capacitive bandpass filter.

The co-injection amplifier is inverting amplification, and its voltage amplification factor is negative, and the resonant divider-voltage ratio of the parallel capacitive bandpass filter is also negative, a<0, as shown in the figure, f0=-c2 c1, because the negative is positive, the feedback signal voltage is introduced to the base to form positive feedback.

According to the Fourier series theory, the square wave voltage when closing and powering on contains many sinusoidal voltages of different frequencies, among which the sinusoidal voltage that meets the resonance condition constitutes positive feedback, which is amplified like a snowball to form a sinusoidal oscillation voltage.

The presence of inductance always prevents the change in magnetic flux, which is a bit like the inertia of an object that always prevents the change in kinetic energy. The inertia of an object makes it require an acceleration process to move when it is stressed, and the same is true when it is blocked to stop, it will not stop instantly, but will continue to travel for a while. This is a hysteresis of external incentives.

The role of a capacitor is to generate a voltage at a certain amount of electricity. I'll give you an example and say it's like a spring:

As in the diagram, the object is in reciprocating motion here under the action of inertia and springs. I think the oscillatory motion of this object is far more intuitive than the oscillation in the circuit, and the two systems are inherently dual.

If you ignore the wear and tear, it will continue to be simple and harmonious. In fact, due to the mechanical loss of the spring in the diagram or the influence of air resistance, the object will do damping oscillation, which is the same reason as considering the damping oscillation of the RLC circuit. With a power supply, you can imagine the effect of adding gravity.

In fact, both the electrical system and the mechanical system are dual, and the mechanical system is more intuitive for us.

Of course, if you can, please try to have an intuitive understanding of the electrical system. Intuitive understanding of electrical systems is important, especially the underlying physical processes, and this understanding does not mean that I come up with known formulas and know how to deduce this conclusion; By understanding only the relationship between quantities, you will be forced to come up with formulas to solve the problems you face many times unnecessarily.

Inductors and capacitors are energy storage components, and the basic physics we have learned are coils and capacitor plates. Coil: Due to the "Lenz's law", when there is a change in current, the coil will induce an electromagnetic field on its own, which is exactly the opposite of the electromagnetic field generated by the applied current (preventing it from changing).

Capacitive plates: are two parallel "conductive plates" that are non-conductive between the plates. When there is a change in the current, the plate stores the charge that increases or decreases due to the change in the current on the "plate".

1) When the capacitor (plate) and the inductor (coil) are connected in series: the impedance of the capacitor is 1 JWC, the impedance of the inductor is JWL (both are related to the frequency of the charged signal), the impedance of the circuit is Z=(1 JWC)+JWL, when the applied voltage is U, the instantaneous amount of current is U [(1 JWC)+JWL], when W 2=1 LC, the capacitor charge is provided by the current induced by the inductor, and the current that causes the inductance to change and generate the magnetic field is precisely provided by the capacitor discharge current. When the frequency is (1 lc) 1 2, w is the resonant frequency. (2) When the capacitor and inductor are connected in parallel, the circuit impedance Z=JWC+1 (JWL).

The algorithm is the same as the concatenation. The LC oscillation circuit is actually a positive and negative change in the direction of the current, and the so-called "oscillation" is not the kind of mechanical oscillation, but when observing with an oscilloscope, the output voltage is positive and negative alternately, so it is called "LC oscillation circuit". I also studied electronics, and I understand it like this.

Hope it helps.