Theoretical basis of power amplifier: the role of power supply filter capacitor

The power supply of the power amplifier should use the "large water pool" filter capacitor. Because the large-capacity capacitor has a large inductance, a small-capacity capacitor should be connected in parallel to "increase the speed of the power supply".

The approach is correct, but the theory of "increasing the speed of the power supply" is too vague. The author believes that the role of the filter capacitor in the power amplifier power supply has three functions:

1. Filter the pulsed DC power obtained after rectification to reduce AC interference.

2. High-speed power supply.

3. Provide a path for audio signals. The filtering effect of the capacitor on the power supply only shows whether there is AC interference in the power amplifier; the energy storage function of the capacitor can provide power for the transient high current of the power amplifier, but the transformer power is insufficient to charge it in time, its energy storage function It is not obvious; and it provides a path for the audio signal to affect the sound quality and timbre is also crucial.

As shown in the figure, the positive half-cycle audio signal is taken as an example. The signal is divided into two channels through a power amplifier tube, an emitter resistor, a speaker, and a ground. One part forms a loop through a power transformer and a rectifier, and the other forms a loop through a filter capacitor. Obviously, the inductance of the transformer is very large, which is not conducive to the passage of the high-frequency part of the audio. It can only pass low-frequency audio signals with a very low frequency and can only provide a path for the subwoofer. The power supply filter capacitor forms a loop. Capacitors and transformer secondary complement each other to provide audio frequency band path from DC to high frequency.

Capacitors have parasitic inductance, which is undesirable. Inductance is not conducive to the passage of high-frequency signals. Generally, the larger the capacitance, the larger the volume, and the larger the inductance. Paralleling small-capacity capacitors can provide higher frequency bandwidth for the signal. path.

"Improve the speed of the power supply" is not correct in itself. The power transmission regardless of frequency is the speed of light.

The only difference is that inductance and capacitance have an effect on the phase of the AC.

Filtering a small-capacity capacitor in parallel uses the small-capacitance capacitor's small inductance to filter out interference waves other than 50 Hz.

BAM Power Transmission Capacitors

BAM Power Transmission Capacitors

Shunt Capacitor,High Voltage Capacitor,Parallel Capacitor,Parallel Capacitor


Posted on