SU1131022A1 - Class d amplifier - Google Patents

Abstract

CLASS D USER, containing a sawtooth generator, the output of which is through. connected in series the first level offset unit, the first adder and the first comparator are connected to the first input of the key amplifier, as well as through the second level offset sequentially connected, the second adder, and the second comparator is connected to the second input of the key amplifier, to the output of which the lower output filter is connected frequencies, the second inputs of the first and second blocks of the level offset and the first and second adders are connected to a common fault, and the second inputs of the first and second comparators are connected between themselves and are an input to a class D amplifier, characterized in that, in order to reduce non-linear distortions, the output of the saw-head voltage generator is connected to the third input of the first adder via a third-level level offset and amplitude negative-polarity selector inputted in series and through serially connected the fourth JV unit of displacement of the level and the amplitude selector of positive polarity with the third input of the second adder, while the second inputs of the third and fourth to the second blocks, see Levels are connected respectively to the positive and negative power supply buses.

Description

The invention relates to radio engineering and can be used in medium and high power amplifying devices. An amplifier is known in which the input signal is converted into a push-pull sequence of latitude-modulated pulses, the polarity of which corresponds to the polarity of the input signal, the push-pull gain after the pulse sequence is performed by highly efficient push-pull key amplifiers, for example, made using a bridge circuit, whose channels are switched with the input frequency signal, which significantly reduces losses due to through currents lj. This amplifier has high efficiency, on the order of 85-90. However, this amplifier has a small dynamic gain range. This is due to the fact that in such amplifiers, small input signal levels correspond to a minimum pulse duration, which leads to significant distortions of the signal j applied to the load due to the inertia of switching of key elements, and reducing the dynamic gain range to 30-35 dB. The closest technical solution to the proposed is a class D amplifier containing a voltage generator, the output of which is through a serially connected first level bias unit, the first adder and the first comparator connected to the first input of a key amplifier as well as serially connected second level bias unit , the second adder and the second comparator are connected to the second input of the key amplifier, the output of which is connected to an output low-pass filter, the second inputs of the first and second first biasing layer pervogoi blocks and second adders are connected to a common bus, and the second inputs of the first and second comparators are interconnected and are input amplifier D 2J. However, a class D limestone amplifier has significant distortion of the amplitude-frequency characteristic. The purpose of the invention is to reduce non-linear distortion. The goal is achieved by the fact that in the class D amplifier, containing a sawtooth generator, the output of which is connected through the first input of the key amplifier through the serially connected first level displacement unit, and the first comparator, as well as through the serially connected second displacement unit URO. , the second adder and the second comparator are connected to the second input of the key amplifier, the output of which is connected to the output of the low-pass filter, the second inputs of the first and second level offset blocks and the first The second and second adders are connected to a common bus, and the second inputs of the first and second comparators are interconnected and are the input of a class D amplifier, the output of the sawtooth generator is connected to the third input of the first adder via serially connected third level offset and amplitude the negative polarity selector and through the fourth level offset and amplitude selector of positive polarity entered in series with the third input of the second adder, wherein orye inputs of the third and fourth level shifting unit are respectively connected to positive and negative power supply rails. FIG. 1 shows the structural electrical circuit of the proposed Class D amplifier; in fig. 2 and 3 -. diagrams for the formation of sawtooth stresses; in fig. 4 diagrams that describe the operation of the amplifier; in fig. 5 - amplitude characteristic of class D amplifier. Class D amplifier contains a sawtooth voltage generator (PN) 1, first and second level displacement blocks 2 and 3, first and second adders 4 and 5, amplitude selector 6 negative and amplitude selector 7 of positive polarity , the first and second comparators 8 and 9, the key amplifier 10 and the output low-pass filter. (LPF) 11, the third and fourth blocks 12 and 13 of the level bias. The FPG 1 is designed to form a sawtooth-shaped voltage Vj (Fig. 2a and Za) with a constant amplitude and repetition rate. GPN 1 can be run on the generator

clock pulses of type -andr and integrator.

Blocks 2 and 3, 12 and 13 of the level bias are designed to bias the signal arriving at their first j input, respectively, on the larger and smaller side with respect to the voltage arriving at their second input. Blocks 2, 3, 12, and 13 of the level bias can be performed on the vertical sator and diode, and in blocks 3 and 13 of the level bias a diode is connected between the output and the second input in the forward direction, and in blocks 2 and 12 of the level bias in the opposite. At the outputs of blocks 2, 3, 12 and 13 of the level offset, sawtooth voltage is formed (the minimum value coincides with the zero level) U, U the minimum value equal to - U 20 (the maximum value is 0) j (the maximum value is + L1), the shape and amplitude of which is determined by the signal V, arriving at 1M at the first input of the level offset blocks 25 (Fig. 2 a, b, c, fig. 3 a, b, c).

The amplitude selector 6 of negative polarity is designed to switch the voltage (2, coming to its input from the output of the level shifter 12, to the input of the adder 4, when O) The output of the amplitude selector 6 is formed by triangular pulses of negative polarity.

Amplitude selector 7 of positive polarity transmits to the input of a sump 5 a voltage of 1/22 the input of an amplitude selector 7, triangular pulses of positive 40 polarity are formed. Amplitude selectors 6 and 7 can be extended on diodes, respectively, included in the reverse and forward directions.

Adders 4 and 5 are designed to sum the input signals and can be made resistive, provided that the resistances of the corresponding resistors of adders 4 and 5 are equal. At the outputs of adders 4 and 5, sawtooth voltages Vj yU are formed. moreover, the rate of change of the sawtooth stresses V and Vj in the range from -55 1 to 4 and two times more than in the rest of the area (Fig. 2 g, d, Fig. 3 g, d).

The proposed amplifier class D works as follows.

Output voltage PN 1. enters through the level 2 bias unit to the first input and through the level bias unit 12 and the amplitude selector 6 to the third input of the adder 4, and also through the level bias unit 3 to the first input and through the level bias unit 13 and the amplitude selector 7 to the third the input of the adder 5. In this case, the outputs of the adders 4 and 5 are formed, respectively, of the voltage Uz U and (Fig. 4a), having a common range of change from - C to 4 U, and in this area the rate of change of the sawtooth voltage V, and V in twice as high. The voltages V and V are fed to the inputs of comparators 8 and 9, where they are compared with the voltage of the amplified signal. With Vi. U at the output of the comparator 8 a positive polarity pulse is generated, and at 2 Uv a negative polarity pulse is formed at the output of the comparator 9. The output pulses of the comparators 8 and 9 are amplified by the key amplifier 10 and transmitted through the output of the low-pass filter 11 to the output of the class D amplifier.

When and, at the output of the key amplifier 10, a push-pull pulse sequence is formed (Fig. 46, the polarity of which is determined by the polarity of the amplified signal. At 11m / and at the output of the key amplifier 10, a sequence of polarized pulses is formed, in a pause. Between which both channels key amplifier 10 are closed

state (Fig. 4b).

Thus, in the proposed class D amplifier, the formation of a mixed pulse sequence, push-pull at high levels} U ,, and one-cycle - at small levels of the amplified signal U. This allows the proposed amplifier class D to obtain a dynamic range of at least known ( 40-45 dB).

Since the rate of change of the sawtooth voltage and Vg in single-ended mode in the field from to and twice as long as in the rest of the field, the pulse duration in the proposed Class D amplifier is as follows with U and single-cycle mode of positive pulse duration , “-G; G duration of negative impulses. . U-UM. (2) at | Ujn (U push-pull mode of operation lUwl-U 2U, the rate of change of pygde o (, uniform voltage in a push-pull region. From (1), (2) and (3) it follows that in the proposed class D amplifier, as in single-stroke and two-stroke modes of operation maintain proportionality between the input and output signals. 2 UH where k is the gain factor of the amplifier. Thus, in the proposed Class D amplifier, unlike the well-known, providing a mixed mode of operation. leads to distortion of the amplitude response. In the proposed class D amplifier The amplitude characteristic is almost linear (Fig. 5, solid line). As a result of adding additional nodes and connections to a known amplifier, in the proposed Class D amplifier, the distortion of the output signal is substantially less than that of the known. So, the known amplifier has , the output-signal distortion1 is in the order of 4-5%, in the proposed distortion it does not exceed 2%.

FL9.1

o-c / AA / V V V ig.gl WV L L TU Fig.Z

FIG L

-1-0,5 -and O U O, SUM

FIG. five

Claims (1)

CLASS D AMPLIFIER, comprising a sawtooth generator, the output of which is connected through a series one connected to the first input of the key amplifier, the first adder and the first comparator connected to the first input of the key amplifier, and also connected through a series connected to the second block of the level, the second adder and the second comparator connected to the second input key amplifier, to the output of which is connected an output low-pass filter, and the second inputs of the first and 'second bias blocks' of the level and the first and second adders under are connected to the common bus, and the second inputs of the first and second comparators are interconnected and are an input of a class D amplifier, characterized in that, in order to reduce non-linear distortions, the output of the sawtooth generator is connected to the third input of the first adder through the third bias unit introduced in series the level and the amplitude selector of negative polarity and through the fourth block of level displacement and the amplitude selector of positive polarity introduced in series connected with the third input ohm of the second adder, while the second inputs of the third and fourth blocks of the level offset are connected respectively to the positive and negative buses of the power source. 1 1131022 2