G.A. Belov

Transistor power amplifiers of class D which basic advantage is the high efficiency, have found wide enough application both in audio equipment, and as the inverters of pressure feeding with an alternating current of adjustable frequency various loadings. Depending on a way of formation of bearing fluctuations of the pulse form subjected to pulse-width modulation (PWM), amplifiers of class D it is possible to divide into schemes with external synchronisation and self-oscillatory. Advantage of self-oscillatory amplifiers consists in simplicity of their technical realisation, and the basic lack  in instability of frequency of bearing fluctuations. By the form characteristics of a relay element (RE) self-oscillatory amplifiers of class D can be divided into schemes with unequivocal characteristic RE and schemes with hysteresis characteristic of RE. In work the analysis of the typical scheme of the amplifier of class D with the unequivocal characteristic of RE, differing higher stability of frequency of self-oscillations, than schemes with hysteresis RE is given. Features of the scheme of the amplifier are considered; with use of the analytical parities received by a method of harmonious balance, the analysis of dependences of frequency and amplitude of self-oscillations from parameters of the scheme and delay in the closed contour is made. The linearized amplifier block diagram is proved, allowing to carry out the analysis and calculation of its frequency characteristics and synthesis of chains of a feedback. The received analytical parities show, that for increase of stability of frequency of self-oscillations it is necessary, that constants of time of a chain of a feedback were much more time of delay, and the constant of time of numerator of transfer function of a chain of a feedback should be much more a constant of time of a denominator.