SU406293A1 - AMPLIFIER CLASS D - Google Patents

Description

The invention relates to amplifiers and can be used in high-power radio transmitters with anodic modulation used in broadcasting and communications.

A class D amplifier is known, which contains a storage capacitor, a regenerative diode, a power source, a switch controlled from an input source, an inductor, and a load.

A disadvantage of the prior art amplifier is its low efficiency. low power and high voltage power supply.

The purpose of the invention is to increase the efficiency. power and reduce the voltage of the power source.

This is achieved by connecting in series parallel to the inductor a storage capacitor with a regenerative diode and a choke, while parallel to the diode there are connected in series an additional inductor and a power source, the junction of which is connected to the common bus.

The invention is explained in a functional diagram in FIG. 1 and 2, with the difference of amplifiers made in accordance with FIG. 1 and FIG. 2, consists only in the method of connecting the low pass filter and the load.

A class D amplifier contains key 1 controlled from an input source with

voltage f / i, storage capacitor 2, regenerative diode 5, choke 4, inductor 5, low pass filter 6, load 7, power supply 8 and additional inductor 9. Switch / can be performed on a lamp or a transistor parallel to it inductance coil 5 and load 7 are connected in series. A low pass filter 6 is necessary if high demands are made on the suppression of the high frequency components of the rectangular pulses at the anode of the key lamp. Otherwise, the role of the low-pass filter can be performed by the inductor 5 and the decoupling capacitor in the load 7, which can be a high-frequency generator modulated on the anode, with parallel or series power, a resistor with a capacitor, and others.

Parallel to the inductor 5 are connected in series connected storage capacitor 2, a regenerative diode 3 and a low frequency choke 4. Parallel to diode 5, there are connected in series an additional inductance 9 and a power source 8, the junction of which is connected to the common bus. The low pass filter 6 and the load 7 can be connected in parallel to the choke 4 (Fig.)

or in series with it (Fig. 2). In the latter case, when using the high-frequency cascade modulated on the anode as a load, the cathodes of the key lamp and the high-frequency cascade lamp can be grounded, which is an advantage of this amplifier.

Class D amplifier works as follows. The voltage / in, supplied to the input of the key 1, is a high-frequency pulse voltage of a rectangular shape. In the absence of a modulating signal (in the carrier frequency mode of the generator), these pulses have a duration close to half of their repetition period, chosen so that the average value of the anode current of the key lamp is equal to the average value of the anode current of the generator. Since the average value of the current of the key lamp is constant, the voltage at the input of the low-pass filter 6 is almost constant and equal to the voltage of the power source 8. In the open state during the action of the trigger pulses on the grid of the key lamp the last is in saturation mode, the voltage drop its anode is small; on the inductance 5 it is almost equal to the voltage of the power source. When the lamp is locked, the voltage on its anode rises, and the current flows through the storage capacitor 2 and the regenerative diode 3. The storage capacitor 2 has a large enough capacity and the voltage on it almost does not change during one pulse, and the voltage is almost equal power supply voltage. In the absence of a modulating signal, the pause between pulses is approximately equal to the duration of the pulses and the energy accumulated by the coil inductance 5 is almost completely recovered except for the losses in the diode and the key lamp, which are small.

When a variable modulating signal appears, the duration of the high-frequency pulses changes in proportion to the level of the signal, remaining on average equal to half the period of their repetition frequency, since the constant component of the modulating signal

the signal is zero. When the pulse duration varies, the average value of the current of the key lamp changes according to the law of change of the modulating signal, which causes a corresponding change in voltage on the low frequency choke 4.

K.P.D. the amplifier is defined by the following expression:

1 3 (/ a pass g, 1

and a max

where At us is the voltage drop on the key lamp in saturation mode, (7a max is the maximum voltage at the load.

Since f / a is about (1.5-2.5%) of & max, then the efficiency can reach values of 92-95%.

In order to reduce the capacitance capacitance 2 and the inductances of the coil 9 and the throttle 4, the latter can be made inductively coupled on a single core of ferromagnetic material.

Subject invention

A class D amplifier containing a storage capacitor, a regenerative diode, a power supply, a switch controlled from an input source and in parallel with which series-connected inductors and a load are connected, in order to increase the efficiency power supply and power supply voltage reduction, parallel to the inductor, are connected in series said capacitor with a diode and choke, while parallel to the diode are connected in series auxiliary coil and power supply, the junction of which is connected to the common busbar.