Views: 1 Author: Site Editor Publish Time: 2019-05-07 Origin: Site
In circuit design, we often need to use capacitors, and their functions will be different in different circuits. The following describes the 9 major functions of the lower capacitor and 27 applications.
What is the role of the capacitor?
1. The function of blocking DC is to prevent the passage of DC and let the AC pass.
2. Bypass (decoupling) action means providing a low impedance path for some associated components in the AC circuit. The general bypass is to filter the interference in the input signal, and the decoupling is to use the interference of the output signal as Filter out the object to prevent interference signals from returning to the power source.
3. Coupling, as a connection between two circuits, allows AC signals to pass through and be transmitted to the next stage of the circuit.
4. Filtering effect, this function is very important for the output of the AC-DC power module. Generally, the capacitance behind the CPU basically acts as a filter.
5. The temperature compensation function compensates for the influence of insufficient adaptability of other components to the temperature, which helps to improve the stability of the circuit.
6. Timing function, capacitor and resistor used together to determine the time constant of the circuit.
7. Tuning, system tuning of frequency-related circuits, such as mobile phones, radios, televisions, etc.
8. Rectification, opening or closing the semi-closed conductor switching element at a predetermined time.
9. Energy storage, storing electrical energy for release when necessary.
The main application of the capacitor:
1. Filter application, such as connecting between the positive and negative poles of the DC output of the power module, can filter out the unnecessary AC components in the DC module, which can make the DC power smoother.
2. The decoupling application is connected between the positive and negative poles of the power supply of the amplifier circuit to prevent parasitic oscillation caused by positive feedback formed by the internal resistance of the power supply.
3. Bypass application, in the circuit of AC/DC signal, connect the capacitor to the resistor terminal or to a common potential from a certain point of the circuit, and set a path for the AC signal or pulse signal to avoid the AC signal component. The voltage drop is attenuated by the resistance.
4, coupling application, in the AC signal processing circuit, used to connect the signal source and signal processing circuit or as an interstage connection of the two amplifiers, used to block the DC, let the AC signal or pulse signal pass, so that the DC of the front and rear stage amplifying circuit The working points do not affect each other.
5. The tuning application is connected to both ends of the oscillating coil of the resonant circuit to play the role of selecting the oscillating frequency.
6. Pad application, auxiliary capacitor in series with the main capacitor of the resonant circuit. Adjusting it can make the frequency range of the oscillating signal smaller, and can significantly increase the oscillating frequency at the low frequency end.
7. Compensation application, auxiliary capacitor in parallel with the main capacitor of the resonant circuit. Adjusting the capacitor can expand the frequency range of the oscillating signal.
8. The neutralization application is connected between the base and the emitter of the triode amplifier to form a negative feedback network to suppress the self-oscillation caused by the inter-electrode capacitance of the triode.
9. Stabilized frequency application plays a role in stabilizing the oscillation frequency in the oscillation circuit.
10, timing application, in the RC time constant circuit and the resistor R in series to determine the length of the charge and discharge capacitor.
11. Accelerate the application and connect it to the oscillator feedback circuit to accelerate the positive feedback process to increase the amplitude of the oscillating signal.
12. Shorten the application, the capacitor connected in series in the UHF tuner circuit to shorten the length of the oscillating inductor.
13. The Crab capacitor, which is in series with the inductor oscillating coil in the capacitor three-point oscillating circuit, plays a role in eliminating the influence of the transistor junction capacitance on the frequency stability.
14. The application of the Thira, in the capacitor three-point oscillation circuit and the capacitor connected in parallel with the two ends of the inductor oscillation coil, to eliminate the influence of the transistor junction capacitance, so that the oscillator is easy to start at the high frequency end.
15. Stabilized application, used in the discriminator to stabilize the amplitude of the output signal.
16. Pre-emphasis application, in order to avoid the attenuation and loss of the frequency division amount during the processing of the audio modulation signal, the set RC high-frequency component increases the network capacitance.
17. To increase the application, in order to restore the original audio signal, it is required to attenuate the high frequency component and noise boosted by the pre-emphasis in the audio signal, and set the capacitance of the RC in the network.
18. Phase shifting application, used to change the capacitance of the phase of the AC signal.
19. A feedback application that is connected across the input and output of the amplifier to return the output signal to the input capacitor.
20, buck current limiting application, connected in series in the AC loop, using the capacitive reactance characteristics of the capacitor to the AC current limit, thus forming a voltage divider circuit.
21. The reverse process application is used for the line scan output circuit and is connected between the collector and the emitter of the row output tube to generate a high-voltage line scan sawtooth wave reverse pulse, and the withstand voltage is generally above 1500 volts.
22. The S correction application is connected in series in the deflection yoke loop for correcting the extended linear distortion of the edge of the picture tube.
23, bootstrap boost application, using the charge and discharge energy storage characteristics of the capacitor, to raise the potential of a certain point of the circuit, the point potential can reach 2 times the voltage value of the power supply terminal.
24, the bright spot application, often set in the video amplifier circuit, used to eliminate the residual bright spot capacitance on the picture tube when shutting down.
25, soft start application, often connected to the base of the switching tube of the switching power supply, in order to prevent excessive surge current or excessive peak voltage applied to the base of the switch tube when the power is turned on, resulting in damage to the switch tube.
26. Start the application and connect it in series with the secondary winding of the single-phase motor to provide a phase-shifting AC voltage for the motor, which is disconnected from the secondary winding after the motor is in normal operation.
27. Operational application, in series with the secondary winding of the single-phase motor, to provide phase-shifting alternating current for the secondary winding of the motor. It is connected in series with the secondary winding during normal operation of the motor.
Commonly for the three major misunderstandings of capacitors, the larger the capacitor capacity, the better the capacitance of the same capacity; the more parallel the smaller the smaller the capacitor, the lower the ESR; the better the effect. Capacitance has many functions, and it needs to be selected according to actual conditions in practical applications.
