Linearisierung eines digitalen Leistungsverstaerkers mit Phasensteuerung

摘要

1,254,233. Control of D.C. motors. GENERAL ELECTRIC CO. 24 Nov., 1969 [16 Dec., 1968], No. 57446/69. Heading H2J. [Also in Division G3] In a system in which A.C. power to a motor is regulated in response to a speed error signal by phase angle control, non-linearity of the system (due, e.g. to the A.C. supply being sinusoidal) is compensated for by passing the error signal through a digital amplifier 6 whose gain varies at at lest one predetermined value of the error signal. Thus, the inherent non-linearity, which approximates to curve 131, is balanced by the response of the amplifier, curve 151, to produce the desired linearity 141; A 1 represents the error signal at which the gain is is varied. In the motor speed control system shown the actual speed from a pulse generator 5 and the required speed are expressed in digital form, the error being supplied to the amplifier 6 as a binary number. The amplifier (Fig. 4, not shown) comprises logic circuits; the error is entered into a six bit shift register (five bits for the binary number and one to indicate sign), which is examined to determine whether it is above or below the prescribed value. If below, the register is connected directly to the output, but if above a mathematical operation, based on theoretical considerations, is performed in which a constant is subtracted by a serial subtractor, the result is shifted one step in the register (to divide by two) and another constant is added in a serial adder. This is fed back to the shift register and hence to the output To compensate also for non-linearity due to the back e.m.f. of the motor, positive feedback is provided by adding a speed signal, from a tachogenerator 7, to the output of amplifier 6; for this purpose the signals may be in analogue form. The result is used to adjust the firing angle of thyristors in power amplifier 3 (and Fig. 1A, not shown).