Analytical variable damping coefficient of the power amplifier
Release Date: [2016-11-11 17:45:51]   Total read [321] Times

Damping coefficient of the power amplifier is a relatively important indicators of the power amplifier, it is relative, says it is relative, because it is closely related to the impedance of the load, it also related to the frequency in a strict sense. The parameters of the damping coefficient calculation for the load impedance and the ratio of internal resistance. Theory is the damping coefficient of the power amplifier, the greater the control of the load ability stronger, whereas the smaller damping coefficient of load control ability is weak. But it only represents the electrical damping coefficient, for the same load following these rules. But different load (speaker), have different physical damping force, so the larger the damping coefficient of the better concept is not entirely correct, because it does not necessarily apply to all load (different load of the physical and mechanical force damping coefficient).

First we analyze what change the damping coefficient, power amplifier resistance and load impedance.

We usually use the formula for the Rs = Rt (Vo/n - 1)

Rs said amplifier resistance

Rt said output connection terminal equivalent resistance

Vo said open circuit output voltage power amplifier

Vt said terminal voltage resistance

The above formula is the circuit principle is used to calculate internal resistance of the power amplifier, and then calculated by the ratio of load and resistance electrical damping coefficient. Change the damping coefficient of the power amplifier principle not change the resistance parameters (power amplifier design is completed the entire circuit structure and the work way to determine the internal resistance ＆#118alue, the ＆#118alue of physical fixed ＆#118alue), but change the voltage closed condition to load position. Usually during transmission wire loss of voltage, and the length of the wire rod which resulted in increased internal resistance of the power amplifier. Reduce the electrical damping coefficient, impact so the worst effects of the low frequency control. The following is analyzed by calculation:

Equivalent load impedance is 8 o, suppose we measure open circuit output voltage of the power amplifier is 8 V, all under the condition of invariable state to join 8 o load (load directly connected to the output terminal of the power amplifier, no middle wire loss), the load on both ends of the voltage of 7.99 V, we use the formula to calculate the power amplifier resistance:

Rs = Rt (Vo/n - 1)

Rs = 8 (8/7.99-1)

Rs = 0.01

Power amplifier resistance is 0.01, load equivalent impedance is 8, calculated electrical damping coefficient of the power amplifier offline for 800. The theory of ＆#118alue is not contain any wire conditions, but must have a wire in the actual application as power amplifier and speaker load between the carrier, but should not be ignored by the following formula to calculate the impedance of the wire for the voltage and the influence of damping coefficient. Using ohm's law R = U/I and R represents the resistance, voltage, U said I said current, the parameter formula with power amplifier in the current state of current:

R = U/I

8 = 7.99 / I

I = 0.99875

Calculated power amplifier working in 8 theory under the load current is 0.99875 amp.

The damping coefficient of the bigger the good concept is not entirely correct, because it does not necessarily apply to all loads

Assuming that between load and power amplifier circuit resistance is 0.1 euro, through the formula to calculate wire together with the load condition, the load on both ends of the voltage. First calculate the wastage of the wire voltage:

R = U/I

0.1 = U / 0.99875

U = 0.099875

Calculated wire loss voltage of 0.099875 V, with no line loss under ideal state voltage 0.099875 V, 7.99 V minus the line loss voltage wire together with the load condition, the load on both ends of the voltage of 7.890125 V.

Wire can be calculated by formula and load under the condition of electrical damping coefficient, we use the formula to calculate the current state of power amplifier resistance:

Rs = Rt (Vo/n - 1)

Rs = 8.1 (8/7.890125-1)

Rs = 0.1142

Power amplifier resistance is 0.1142, load equivalent impedance for 8.1 euro, calculated wire together with the load condition, electrical damping coefficient of the power amplifier for 72.

The above calculation results visible wires for the influence of damping coefficient of the power amplifier is very huge.

Through the above analysis, it can be seen) variable damping coefficient function is very important, the amplifiers fully considering the practical application, the wastage of the wire damage damping coefficient, affect the ability of the load control problem.

Analysis of its working principle is: the power amplifier hardware architecture of the digital products must have a closed-loop detection function, by controlling the output voltage difference between open and closed circuit adjust the damping coefficient of the power amplifier. Input the parameters of the wire (line length and the impedance of the line diameter or wire), power amplifier software automatically based on the input wire impedance parameters to increase the output voltage of CCTV, which kept its contains the line loss, load application side to get the characteristics of high effective electrical damping coefficient.

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