SU516175A1 - Push-pull power amplifier - Google Patents

Description

one

The invention relates to radio engineering and can be used in high-power output devices of a rado-equipment, operating one, for complex load.

A push-pull power amplifier is known, which contains in one arm n transistors of the same conductivity type, in the other p transistors of the opposite conductivity type, with the transistors in each arm connected in series to the power supply circuit, the emitters of the first arm transistors are interconnected and connected , the collectors of the last transistors and terminals are connected to the terminals of the power supply with maximum and minimum potentials, respectively, and the collectors of the remaining transistors are connected via rows to the taps of a power source iromezhutochny .mi potentials.

However, efficiency Known power amplifiers are reduced when operating at a complex load, i.e., the power loss increases.

The purpose of the invention is the power loss due to the complex nature of the load.

For this purpose, in the proposed power amplifier, the collector of the first transistor of one arm and the collector of the p-1 transistor of the other side are connected to one power supply source, to the next branch - the collector of the second transistor and p-2 transistor of the other arm, etc.

2

On fng. 1 shows a circuit diagram of an amplifier with a power supply with four taps; in fig. 2 shows the current H voltage curves for the circuit of FIG. 1 with active-capacitive load.

The push-pull power amplifier contains in one arm n transistors 1 of one conductivity type (-b), in the other - n transistors 2 of opposite conductivity (2i-24), with transistors 1, 2 ii each arm connected in series to a power supply circuit (in the drawing is specified), the emitters of the first shoulder transistors are interconnected and connected to the total load 3, the collectors of the tractors 2 and U are connected to the leads (taps) 4i and 4) of the power supply with maximum and minimum potentials, respectively, and KO.Ilectors of the remaining transistors B, 1z, and 2z are connected via diodes 5 and 6 to the taps 49 and 4z of the power supply with intermediate potentials, to the power supply taps 42 are connected the collector of the first transistor li of one arm and the collector of the transistor 2z of the other arm, to the outlet 4z - transistor 1z collector of one shoulder and transistor 2i of the other shoulder.

Diodes 7 and 8 serve to create the necessary bias on the bases of transistors 1, 2 when the transistor operates in a mode close to saturation. Diodes 9 and 10 protect transistors 1, 2 from breakdown. The bias voltage sources And and 12 and the resistors 13 and 14 create the necessary bias on the bases of the transistors 1, 2.

In the voltage circuit at the taps 4h and 44, the power sources are positive, and at the taps 4i and 42 - negative. At the same time, the following ratios are fulfilled: the voltage on the tap 44 is greater than the voltage on the tap 4h, and the voltage module on the tap 42 is less than the voltage module on the tap 41. Such an arrangement of the amplifier with four tapes of the power source takes place when the amplifier with a symmetrical two-pole pny input signal.

In power consumption mode, the push-pull power amplifier operates as follows.

At low positive voltages on the load 3, the amplifier is powered by a tap 4 of the power supply. The transistor btransistors li and b are fully open. When the voltage on the load exceeds the voltage of the 4z tap of the source, the transistor 1z opens fully, and in the active mode, the transistor C operates, which is powered by the tap 44 of the power supply. This process of switching the source taps (if there are transistors 1 in shoulder p) goes to the maximum voltage value at load 3, and when voltage decreases at load 3, it repeats in the reverse order until the current in load 3 coincides with voltage (time period from to to 4 in FIG. 2).

As soon as the current in the load 3 changes sign, the chain of transistors h-q turns off and the chain of transistors 2i-24 begins to work.

In the time period 4-4 (Fig. 2), the complex load 3 does not consume energy from the source, but gives it away. Capacity is discharged not to the minimum voltage level, but to the closest voltage level. If, at the same time, the input voltage of the amplifier is between the voltage levels at the taps 44 and 4h (time tz in Fig. 2), then the active mode will have transistor 2i, and the capacitance will be discharged to the tap 4z of the power supply. When the voltage on the load 3 is less than the voltage on the tap 4, the diode 6 is closed by reverse voltage, in active mode the transistor 2 is working, and the capacitance is discharged to ground through the open transistor 2i.

If in a chain of n transistors, then this process goes on until the capacitor is completely discharged (time period / 2- (:, in Fig. 2), and as the voltage at the input changes further, the current and voltage of one sign Capacity recharge occurs, load 3 consumes power. Switching the power supply and transistor 1 taps,

2 comes as described above. The transistors 2z and 24 provide the capacitance charge of the negative half-wave, and the transistors b and b provide the discharge of the capacitance.

Increase efficiency by reducing losses in transistors 1, 2 with a capacitive load 3 according to the scheme of FIG. 1 is illustrated in the drawing of FIG. 2, where:

U (t) is the load voltage;

I (t) is the current in the load;

 - voltages at the taps 4i-44, respectively.

In the period from / o to tz and from 4 to / 6, the load 3 consumes energy. In the interval from / 2 to 4 and from t to / 8 load

3 Puts energy into the power source. The rare hatching in FIG. 2 is shown

part of the voltage of the power source, which falls on the transistors with this form of voltage U (t) on the load 3 when the circuit operates in the usual mode with two power sources. Thick hatching shows the portion of the supply voltage that falls on the control transistors as shown in FIG. 1, using four power sources and with the same voltage form on the load. The ratio of areas shaded with thick and sparse shading indicates that in the proposed amplifier, the voltage across the transistors is much smaller. Therefore, the proposed amplifier is more generic than usual.

The closer the phase shift between the voltage and the current in the load is to 90 °, the more efficient is the use of additional connections in the amplifier, ensuring the discharge of the load capacitance 3 to successive power supply taps.

Claims (1)

Invention Formula A push-pull power amplifier containing n transistors of the same conductivity type in one shoulder and n transistors of the opposite conductivity type in the other, with transistors in each arm connected in series to the power supply circuit, the emitters of the first shoulder transistors are interconnected and connected to the common load, the collectors of the last transistors The cells are connected to the terminals of the power supply with the maximum and minimum potentials, respectively, and the collectors of the remaining transistors are connected via diodes to Am of a power source with intermediate potentials, characterized in that, in order to reduce power losses during complex loading, the collector of the first transistor of one arm and the collector of p-1 transistor of the other arm are connected to one lead of the power source, to the next tap - collector of the second transistor and / 1-2 transistors of the other arm, etc.