JPH04103729U - Digital high precision voltage detection circuit - Google Patents

Abstract

(57) [Summary] [Purpose] Increase the resolution of the analog/digital conversion circuit used for control means of conversion with analog values that always occurs in digital control by 2 to 3 bits without limiting the accuracy to the number of bits used. The aim is to increase the resolution to a level equivalent to that of the other devices, thereby increasing the accuracy of the device. [Structure] Rather than using the analog/digital converted value as is, the value is detected a certain number of times at higher speed, the number of populations is increased, the number of digits is increased, and then the accuracy is increased by averaging. As a means for increasing the value, a digital filter circuit is provided at the output of the analog/digital conversion circuit, and this output is added to and subtracted from the set value to obtain a deviation, resulting in a feedback circuit.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention can also be used as a means of controlling conversion with analog values, which always occurs in digital control. The resolution of the analog/digital conversion circuit to be used is determined by the precision in terms of the number of bits used. Increase the resolution by 2 to 3 bits without limiting it to the limit, increasing the precision of the device This invention relates to a digital high-precision voltage detection circuit that provides optimal means for achieving this.

0002

[Conventional technology]

It is generally well known that analog/digital conversion (hereinafter referred to as A/D conversion) is used as a setting and feedback signal in digital control of general industrial machinery. FIG. 3 shows a block diagram of an example of a conventional thyristor Leonard in which current control of a DC motor and digital setting are used to perform A/D conversion of current feedback to perform digital control. In FIG. 3, a DC motor 10 is driven by a thyristor converter 8. In FIG. AC input power 7 is converted into DC power by a thyristor converter 8 and applied to a DC motor 10 through a shunt 9. The current of the DC motor 10 is detected as an analog value _IFA as a current feedback to the digital control circuit 2 via the shunt 9, and is further detected as a digital value _IFD by the A/D conversion circuit 5.

[0003] The digital control circuit 2 uses the digital setting device 1 to set a gate pulse with an ignition phase according to the deviation Δε between the digital current command I _SD and the digital current detection value I _FD described above. The voltage is applied to the thyristor converter 8 via the circuit 4 and the gate pulse amplifier 6, and the voltage applied to the DC motor 10 is varied to control the magnitude of the current.

Next, this control operation will be briefly explained with reference to FIG. 4. FIG. 4 is a status diagram of each part performed in the digital control circuit 2 using a 4-bit circuit for the digital setting device 1 and the A/D conversion circuit 5 of the feedback, and 2-1 is a 4-bit digital setting I _SD , 2-2 is the analog detection voltage, 2-3 is the digital feedback I _FD resulting from 4-bit A/D conversion, and 2-4 to 6 are the waveforms of the input deviation Δε of the PI (arithmetic circuit) 3. . In terms of control, the components after the PI calculation circuit operate so that the deviation Δε becomes zero by canceling I _SD and I _FD . At that time, the deviation Δε is always offset controlled by increasing or decreasing by a minimum of 1 bit, such as 2-5, so the control accuracy is also higher than the resolution of 1 bit of the circuit configuration / (number of A/D conversion bits) = resolution. will not rise. In addition, in order to improve accuracy, there are cases where a very large filter is installed on the analog side and A/D conversion is performed while averaging as much as possible, but the only way to improve accuracy is to increase the number of bits.

[0005]

[Problem that the idea aims to solve]

However, in control with such a configuration, the deviation Δε is Even if it is controlled to ±0, it is always ±1 bit (in this explanation, it is a 4-bit circuit). This results in offset control of 1/16), and this value affects the accuracy of the device. i.e. , in a 4-bit circuit, it will not increase by more than 1/16. To increase this accuracy, you can use an 8-bit circuit (=1/256) or a 10-bit circuit ( = 1/1024) and reduce the offset amount by at least 1 bit to increase the resolution. It's fleeting. In this case, it is disadvantageous in terms of hardware, space, and economy.

[0006] This invention takes into account that there is some ripple in the analog voltage, and the circuit configuration is A device that can obtain the same resolution as increasing several bits without increasing the number of bits in terms of hardware. This paper proposes a digital high-precision voltage detection circuit.

[0007]

[Means to solve the problem]

In conventional control, the set value and A/D conversion feedback value are calculated at regular intervals. It was controlled by the difference between settings and feedback. Regardless of the set value, the feedback side may use the average value of several times. Ru. A/D conversion with a 4-bit circuit is used for current control in Figure 3, and the full bit is 10 Assuming A/10V/4 bits, the resolution is 10A x 1/16 = 0.625A. 0 The detection voltage will not change unless there is a change of .625A. At the current of 6A in Figure 5, the detection rate is 9/16. It's out. Even if you use several average values, the same 4-bit operation will have the same resolution. control remains unchanged. With the 6A setting in Figure 6, the current value with ripple is detected four times and average value control is performed. When 6.3A, 6.8A, 6.1A, 5.8A, (6.3+6.8+6.1+5.8) /4 = 6.25A, which is exactly 10/16 detection. Both as the minimum detection value is 1/16. As a means of increasing resolution, this A/D output is used for a certain period of time T. A digital filter that measures the interval N times and uses the average value as the detection voltage for each fixed period T. Set up a circuit.

[0008]

[Effect]

As mentioned above, the value at the resolution of the A/D converted bit number can be used as an instantaneous value or an average value. Even if used as an average value, the result will be the resolution of the minimum detected voltage. The present invention does not use the A/D converted value as is, but further increases the value. By detecting a certain number of times at high speed, increasing the number of groups in each group, increasing the number of digits, and then averaging. This has the effect of increasing accuracy. Especially for a fixed analog value, there is no change in the number of output bits even after digital conversion. Although the effect is weak, it works effectively on analog/digital conversion including ripple. Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

[0009] Figure 1 is a block diagram showing an embodiment of the present invention, and Figure 2 is its time chart. be. In FIG. 1, as the feedback value in the digital arithmetic circuit 2, The output of the A/D conversion circuit 5 is further added to and subtracted from the set value by the digital filter circuit 11. It was used in a feedback circuit to obtain the deviation Δε. Figure 2 also shows numerical values in operation. As an example, if the proposed method operates under the same conditions as the conventional calculation in Figure 6 above, This is an explanation of what values the means act on and how they actually operate.

[0010] The feedback value used at _T1 is the average value of N times during the previous period T, and the feedback value used at _T2 is similarly the average value of N times during the previous period T. It is what you use. The value at T ₁ is [{(10+10+10+11+11)/16}/5] = 52/80, and the value at T ₂ is [{(10+11+11+11+10)/16}/5] = 53/80, and the difference is |(52/80)-(53/80)|=1/80.

[0011] When conventional control is similarly compared, at T ₁ , it is 11/16, and at T ₂ , it is 10/16, and the difference is |(10/16)−(10/16)|=1/16, as described above. However, in the present invention, the detection resolution is 1/80, making it possible to detect levels that are (80/16) = 5 times higher than conventional methods. In perfect DC detection without ripples, [{(10+10+10+10+10)/16}/5] 110/16, [{(11+11+11+11+11)/16}/5] = 11/16, and |(10/16)-(11/ 16) |=1/16, which is limited by the resolution of A/D conversion. Therefore, it can be seen that the present invention is effective in detecting voltage with second ripple.

0012 As explained above, you can easily use 2 to 3 bits without increasing the number of bits in terms of hardware. (For example, 8 bits is equivalent to 10 bits) The detection accuracy is the same as that of adding the number of bits. can get. In particular, there is no hardware problem with voltage detection with ripples (A/D converter chip and If there are restrictions on the Always convenient.

[0013]

[Brief explanation of drawings]

FIG. 1 is a current control block configuration diagram of the present invention.

FIG. 2 is a detection time chart diagram for explaining the present invention.

FIG. 3 is a block diagram of a device for conventional thyristor Leonard current control;

FIG. 4 is a time chart of calculation signals during the control.

FIG. 5 is an input/output time chart in A/D conversion.

FIG. 6 is an actual conversion time chart of A/D conversion.

[0014]

[Explanation of symbols]

1 Digital setting device 2 Digital control circuit 3 PI calculation circuit 4 Gate phase control circuit 5 A/D conversion circuit 6 Gate pulse amplifier 7 AC input power supply 8 Thyristor converter 9 Flow divider 10 DC motor 11 Digital filter circuit

Claims (1)

[Scope of utility model registration request] Claim 1: In a circuit that digitally converts an analog voltage and uses it as a reference or feedback value including ripple, the digitally converted output is measured a certain number of times faster than the ripple period, and the average value of the certain number of times is measured at a certain period. 1. A digital high-precision voltage detection circuit characterized by having a digital filter circuit for reducing ripples and increasing the resolution determined by the number of bits of the digital conversion circuit by a certain number of measurements.