JPS6029976B2 - analog output circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an analog output circuit that insulates, samples and holds a plurality of time-series data signals and outputs the same.

'2) Conventional technology When switching, sample-holding, and outputting multiple time-series data signals using a central processing unit, a simpler and more reliable circuit is desired when the data can be updated at a low speed. .

In this case, a photocoupler is used for isolation,
It is conceivable to use a semiconductor analog switch such as a FET as the switching circuit, and use a simple sample-and-hold circuit consisting of a sufficient capacitor and an amplifier as the sample-and-hold circuit if data updating is slow.

However, since all circuit elements, including the photocoupler, operate in an analog manner, response is slow and mutual interference between channels is likely to occur, causing errors. For example, as shown in Figure 3, the rise and rise of the point selection signals for each channel overlap, and in this case, the switches of two channels are driven at the same time, causing mutual interference and resulting in errors. . OBJECT OF THE INVENTION In view of the above points, an object of the present invention is to eliminate mutual interference between channels and provide a highly accurate isolated analog output.

'4 - Structure of the Invention This invention provides a central processing unit that generates a plurality of data signals, a location selection signal, and a clock signal for sending these signals, and an isolated transmission system for the data signals generated by the central processing unit. a first photocoupler, a DA converter that converts the output of the first photocoupler into an analog signal, a switching circuit including a plurality of analog switches that switches the output of the DA converter; A plurality of sample and hold circuits that sample and hold the output, a gate circuit to which the location selection signal of the central processing unit is fed, and an isolated transmission of the output of the gate circuit to supply it to the analog switch of the kirifusuma circuit. a second photocoupler; and a monostable multipipe plate which generates a pulse signal for a predetermined period of time when a clock signal is generated and supplies it to the gate circuit; This is an analog output circuit characterized in that a location selection signal is prohibited and none of the analog switches in the sliding door circuit are driven.

{5) Embodiment of the Invention FIG. 1 is a configuration explanatory diagram showing an embodiment of the invention.

In the figure, 1 is a central processing unit such as a microprocessor that generates a plurality of time-series data signals, a location (channel) selection signal, and a clock signal for transmitting these signals, and 21 is a central processing unit. A first register that temporarily holds the data signal of the device 1 and outputs it in response to a clock signal; 31 is a first photocoupler that insulates and transmits the data of the first register 21; 4 is a first photocoupler 31
5 is a D-A converter that converts the output of
- A semiconductor analog switch 51 such as a plurality of FETs that sequentially switches and selects the analog output of the A converter 4.
, 52 . . . The cut-sliding circuit 61, 62 . . .
Resistors R, , R2 sample and hold the output taken out by each analog switch 51, 52... of the switching circuit 5
,..., a time constant circuit consisting of capacitors C,, C2,... and a sample-and-hold circuit including amplifiers A,, A2,..., 71, 72,... are sample-and-hold circuits 61, 62,...
It is an output terminal that takes out the output of...

Further, 22 is a second register 8 that temporarily holds the location selection signal of the central processing unit 1 and outputs it in response to a clock signal.
32 is a gate circuit consisting of a plurality of AND circuits to which the output of the second register 22 is supplied; 32 is an insulated transmission of the output of the gate circuit 8 and supplies it to the switching circuit 5; A second photocoupler 9 for driving . This is a monostable multipipulator that prohibits the location selection signal from passing through the gate circuit 8. In other words, the central processing unit 1
generates a data signal and a location selection signal corresponding to each channel at a predetermined period, and the data signal is sent to the first register 21 and the first photocoupler 31 by the clock signal.
, and is supplied to the switching circuit 5 via the DA converter 4. Second
As shown in the figure, the location selection signal corresponding to each location (CH2, CH3, . . . ) for each clock signal is supplied to the gate circuit 8 via the second register 22. Every time a signal is generated, the monostable multipipelator 9 generates a pulse signal for a predetermined time t, and during this time, no location selection signal passes through the gate circuit 8.
None of the analog switches 51, 529, . . . of the cutting-sliding circuit 5 is driven. Outside this prohibited time, the location selection signal passes through the second photocoupler 32, sequentially drives any of the analog switches 51, 52, . . . of the switching circuit 5, and The output signals are sampled and held by sample and hold circuits 61, 62, . . . and outputted from output terminals 71, 72, . Note that this series of operations is repeated in sequence to obtain continuous output for each channel. In other words, when the clock signal 1 shown in FIG. is closed and no location selection signal passes through. After a certain period of time has elapsed, the location selection signal of channel CHI rises as shown in FIG. Again, see Figure 2. When the clock signal 2 is supplied to the monostable multipipetrator 9, the monostable multipipelator 9 generates a pulse signal for a certain period of time, and during this pulse generation time, the gate circuit 8 is closed.
The location selection signal of channel CHI rises. This CH
The location selection signal I completely falls within time t. When time t has elapsed, the location selection signal of channel CH2 rises, and the same operation is repeated thereafter. In this way, when the location selection signal is switched, a period is created in which no location selection signal passes through the gate 8, and the location selection signal of the next channel is switched on after the location selection signal of the previous channel has completely fallen. Because they are standing up, there is no risk of them interfering with each other and causing malfunctions.

{6} Effects of the Invention As described above, the present invention operates a monostable multipipulator using a clock signal, prohibits a point selection signal from passing through a gate circuit, and transfers data to a photocoupler, a switching circuit, and a sample. This is an analog output circuit that outputs through a hold circuit.

Therefore, the point selection signal that drives each channel of the switching circuit is designed to have a prohibited state in which no switch is driven for each channel, so there is no mutual interference between signals, and the output is isolated with high precision. can be obtained.

In addition, the circuit configuration and drive program are simple, and it is not affected by response delays caused by photocouplers, analog switches, etc., and is inexpensive and highly reliable.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, and FIG.
3 are waveform diagrams for explaining the operation. 1...Central processing unit, 21, 22...Register, 3
1, 32... Photocoupler, 4... D-A converter,
5...Kirifusuma circuit, 51, 52... Analog switch, 61, 62... Sample hold circuit, 8... Gate circuit, 9... Monostable multi-piperator. Qin Z Tuduo 3 European mouse ship

Claims (1)

[Claims] 1. A central processing unit that generates a plurality of data signals, a location selection signal, and a clock signal for transmitting these signals, a first photocoupler that insulates and transmits data signals generated by this central processing unit, and A DA converter that converts the output of the photocoupler No. 1 into an analog signal, a switching circuit consisting of a plurality of analog switches that switches the output of this DA converter, and a plurality of sample holds that sample and hold the output of this switching circuit. a gate circuit to which the point selection signal of the central processing unit is supplied; a second photocoupler which insulates and transmits the output of the gate circuit and supplies it to the analog switch of the switching circuit; and a monostable multivibrator that generates a pulse signal for a predetermined period of time and supplies it to the gate circuit, and when the pulse signal of the monostable multivibrator is generated, the point selection signal is prohibited and any analog switch of the switching circuit is activated. An analog output circuit characterized in that it does not drive any of the signals.