SU1363459A1 - A.c. a-d converter - Google Patents

Abstract

The invention relates to a measurement technique and can be used to accurately convert alternating voltage into a digital code. The conversion process consists of three cycles. In the first cycle, the control unit 12 forms an AC voltage-to-DC converter circuit consisting of series-connected diodes 4, 5 and a resistor 9. The output voltage of the AC-DC converter converted to a DC connection point is converted into an ADC constant current and is fed to the summing input of the device 12 addition and subtraction. By the end of the conversion signal of the first cycle, the control unit 13 forms a circuit of an alternating voltage converter into a constant, consisting of series-connected diodes 4, 5 and a resistor 9. The output voltage, also taken at the junction point of the diodes, is digitized by the DC / DC converter and supplied to the summing input of the device 12 addition and subtraction. On the signal of the end of the conversion of the second cycle, the control unit 13 forms a circuit of an alternating voltage converter into a constant consisting of series-connected diodes 4, 5 and a resistor 9, but the output voltage is removed from the resistor a 9 This is digitized by the ADC 11 direct current, is fed to the subtracting input device (L with O) co;

Description

12 addition and subtraction. As a result of the three conversion cycles in the addition and subtraction device 12, the result is

The invention relates to a measurement technique and can be used to accurately convert an alternating voltage to a digital code.

The purpose of the invention is to improve accuracy.

FIG. 1 shows a block diagram of an analog-digital converter of alternating current; in fig. 2 is a control block diagram.

The device contains a scale converter 1, a converter of alternating voltage into a constant voltage, made in the form of a switch 3, diode A and 5, switches 6-8 and a resistor 9, a low-pass filter 10, an analog-to-digital converter 11 of direct current, a device 12 addition and subtraction, which can be performed in the form of a reversible counter, and a control unit 13, performed on two D-triggers 14 and 15 and an OR-NOT 16 element, which is a loop-closed shift register, controlled by the signals of the end of conversion for example a digital code from an analog-to-digital converter, for example, a pulse

th type.

 I-, -

The measurement process consists of three conversion cycles.

In the first cycle, the signal control unit 13 and 2 (Fig. 3) acts on the commutators of the alternating voltage converter to a constant one and connects the input of the switch 3 to the output 17, the input of the switch 8. to the exit. 18 and through the switch 7 to the low-pass filter Yu and the input of the switch 6 to the output 19. The V-sensor of the analog-to-digital converter 11 is connected to the summing input of the device 12 of the addition and subtraction.

input voltage to the digital code, not depending on the voltage drop across the diodes, their temperature and time drift. 1 hp f-ly, 2 ill.

Thus, in the first step of converting pho1), the circuit of the alternating voltage converter is constant, consisting of successively connected diodes 4 and 5 and a resistor 9. The output voltage is removed from the low-pass filter 10 connected to the diode junction point . This voltage is U 8t ,, xi ,,

10 where Ug is the input voltage, Ug is the voltage drop on the first diode.

 The voltage, 1 in the analog-digital converter 11 constant, current is converted to digital,

/ B code M.

According to the signal of the end of the conversion and the first clock cycle, the signal control unit Uj connects the input of the switch 3 to the output 20, the input of the switch

20 6 to the output 21 and through the switch 7 to the low-pass filter and the input of the switch B to the output 22. The output of the analog-digital converter 11 of the direct current remains connected to the summing input of the device 12 of the AND subtraction.

Thus, in the second conversion cycle, an alternating voltage converter circuit is a constant consisting of diodes 4 and 5 and a resistor 9 connected in series. The output voltage is removed from the low-pass filter 10 connected to the junction point diode, ix, x, where Ugj is the voltage drop on the second diode.

This voltage is applied to the input 40 of the analog-to-digital converter 11 and is formed into a digital code Nj, which is fed to the summing input of the device 12 of addition and subtraction.

As a result of the first two conversion cycles in the last 25

thirty

45

is the sum (i-uj-),

where is the conversion factor of the analog-to-digital converter.

The signal and, the end of the second conversion signal block 13 controls the signal and connects the output of the switch 7 connected to the low-pass filter to the resistor 9 and switches the output of the analog-digital converter 11 from the summing input of the device 12 of addition and subtraction to subtract. Further, the circuit is similar to that described for the previous clock cycle.

Thus, in the third conversion cycle, an AC / DC converter circuit is formed, consisting of series-connected diodes 4 and 5 and a resistor 9, the output voltage being removed from the low-pass filter 10 connected to the resistor 9. A value equal to U i, U - Ua - V qt in the analog-digital converter is converted into a digital code N, which is fed to the subtractive input of the device 12 of the addition and subtraction.

As a result of all three conversion cycles in the device 12, the addition and subtraction accumulates the result, " pUj ,.

The signal and, at the end of the third conversion cycle, the circuit returns to the initial state.

Thus, the result at the output of the analog-digital converter does not depend on the voltage drops on diodes 4 and 5, and hence the error of the analog-digital converter does not depend on the characteristics of the diodes, their identity and is invariant to their time and temperature drift.

Claims (2)

1. Analog-to-digital AC converter containing a control unit and a series-connected scale converter whose input is an input bus, an AC-DC converter, a low-pass filter, an analog-digital DC converter, an adder and subtractor The control input of which is connected to the first output of the control unit, the input of which is connected to the output. Conversion end of the analog-digital converter of the direct current, which is different In order to increase accuracy, the AC / DC converter is made on four switches, two diodes and a resistor, the first output of which is connected to the common bus, the second output is combined with the first information input of the first switch and connected to the first outputs the second and third switches, the second output of the second switch is combined with the second information input of the first switch, the anode of the first diode and connected to the first output of the fourth switch, the second output of which is combined with output of the third switch and connected to the anode of the second diode and the third information input of the first switch, the output of which is the output of an AC / DC converter, whose input is the information input of the fourth switch, and the cathode of the first diode is connected to the information input of the third switch, the cathode of the second diode is connected to the information input of the second switch; the first control inputs of the first, second, third, and fourth switches are connected to the first output control unit, a second output connected to the gate second inputs of said first, second, third and fourth switches, the third output - with the third control input of the first switch and a second control input device kntsim addition and subtraction. 2. The converter according to claim 1, which is characterized by the fact that the control unit is completed on two D-triggers and a W-NOT element, the output of which is the first output of the block and is connected to the D input of the first D-trigger - a pa whose C input is combined with the C input of the second D-flip-flop and is a block input, the output of the first D-flip-flop is the second output of the block and is connected to the D input of the second B-flip-flop, the output of which is the third output of the block and is connected to the first input of the element OR-NOT, the second input of which is connected to the output of the first D-flip-flop, and the R-inputs of the first and the third D-triggerE are connected to the zero setting bus. ig Uif one FIG. 2 Us