CN102497197A - Isolated bidirectional digital input output circuit - Google Patents

The invention relates to an isolated bidirectional digital input output circuit. The circuit comprises an I/O port. When the I/O port is taken as an input port, a power supply is added to the I/O port; after an electric signal of the I/O port passes through a voltage division circuit and a first filter circuit, a first optical coupler device is conducted; and after the electric signal of the first optical coupler device passes through a first current limiting resistor and a second filter circuit, the signal is transmitted to a signal input port which can be connected with a programmable logic device. When the I/O port is taken as an output port, after a driving signal output by a programmable controller CPLD passes through a second current limiting resistor, a first triode is triggered; after the electric signal of a collector electrode of the first triode passes through a third current limiting resistor and a third filter circuit, a second optical coupler device is triggered; after the electric signal of the second optical coupler device is amplified by a second triode, the electric signal is transmitted to the I/O port. By using the circuit, a user can conveniently configure and save the number of the I/O. A complete isolation mode is used to improve reliability.

Band is isolated the bi-directional digital imput output circuit

Technical field

The present invention relates to a kind of digital in-output circuit, relate in particular to a kind of band and isolate the bi-directional digital imput output circuit, this circuit can make the user can freely select input and output mode under the cooperation of software.

Background technology

In the commercial Application, along with the continuous development of power electronic technology, microelectric technique and modern control theory, frequency converter has been widely used in the frequency control of alternating current motor in modern times.Because frequency converter is driveability and better controlling characteristic efficiently, and it is widely used in industry-by-industries such as iron and steel, chemical industry, weaving, mechanical electric power, papermaking.In each application scenario, digital input/output port is absolutely necessary, and it is widely used in control external devices action and accepts switching signal, to reach frequency converter and external system is cooperated normally.

At present, in the frequency converter of each brand, digital input/output port definition has nothing in common with each other; Major part is all separated; Be that input port and delivery outlet are irrelevant, the digital input and output of required usefulness can not be satisfied concrete demand under a lot of situation, and this just causes the waste of input and output terminal.Though the product that has in addition have can be multiplexing digital input and output terminal, it is not externally isolated, therefore outside interference might influence internal circuit, thereby has influenced the normal operation of entire product.

Fig. 1 is existing digital input circuit; Fig. 2 is existing digital output circuit; Numeral input port DI and digital output DO separate separately, and external power source DC receives input port DI through K switch, make the input conducting of optocoupler U1 through divider resistance R1, R2; The level of the output of optocoupler U1 is pulled down to 0.7V by VCC and makes that importing detection signal CDI changes, and accomplishes once digital input function at this moment; Optocoupler U2 sends the conducting of drive signal DO_DRIVE control optocoupler U2 input as the isolating chip of digital quantity output by CPLD, and this moment, output port needed external power supply DC and load RL to accomplish the digital quantity output function.

There is following shortcoming in this numeral input circuit that output is separated with numeral: 1, occupy the I/O resource, can not reasonably distribute the I/O mouth according to user's real needs, cause the waste of I/O mouth.2, digital output circuit can not provide external power supply, needs external power supply could accomplish digital output function, has limited the use occasion of product with this.

Summary of the invention

Technical problem to be solved by this invention provides a kind of band and isolates the bi-directional digital imput output circuit; The input/output port of this circuit is same port; Avoided the waste of I/O mouth, and can under the cooperation of software, make the user can freely select input and output mode.

The present invention for the technical scheme that problem adopted of the above-mentioned proposition of solution is:

A kind of band is isolated the bi-directional digital imput output circuit, and it includes the I/O mouth;

When I/O mouth the time as input port; Additional power source is to the I/O mouth; The signal of telecommunication of I/O mouth is behind the bleeder circuit and first filter circuit; Make the first optocoupler conducting, the signal of telecommunication that first optocoupler comes out behind first current-limiting resistance and second filter circuit, pass the signal along to signal input that programmable logic device is connected on;

When I/O mouth the time as output port; The drive signal of Programmable Logic Controller CPLD output triggers first triode behind second current-limiting resistance; The signal of telecommunication that the collector electrode of first triode comes out is behind the 3rd current-limiting resistance and the 3rd filter circuit; Trigger second optocoupler, the signal of telecommunication that second optocoupler comes out arrives the I/O mouth with electrical signal transfer after second triode amplifies.

Press such scheme, the Standard resistance range of described first current-limiting resistance is 66 Ω-3300 Ω; The Standard resistance range of described the 3rd current-limiting resistance is 100 Ω-500 Ω.

Press such scheme, when the I/O mouth was as input port, the I/O mouth connect a dummy resistance.

Press such scheme, described first filter circuit and the second filtered electrical routing capacitance and resistance are composed in series.

Press such scheme, described the 3rd filtered electrical routing capacitance and resistance are formed in parallel.

Press such scheme, described first optocoupler and second optocoupler are made up of light-emitting diode and phototriode.

When I/O mouth the time as digital output port; See DO DRIVE off as output drive signal by Programmable Logic Controller CPLD; First triode conducting this moment, the collector electrode of first triode is pulled down to the 0.7V effect, after the second optocoupler conducting; The signal that second optocoupler comes out is loaded into the I/O mouth after second triode amplifies, realize digital output function.When I/O mouth the time as digital input port; External voltage is added on the I/O mouth; Behind bleeder circuit and filter circuit, make the input of first optocoupler produce pressure reduction, the first optocoupler conducting; The signal that first optocoupler comes out passes the signal along on the digital signal input port that is connected with Programmable Logic Controller CPLD behind first current-limiting resistance and the second filtering road.

Beneficial effect of the present invention is: 1, independently optocoupler is all adopted in digital input and output, realizes the isolation fully of user interface and internal circuit.2, when I/O mouth during as delivery outlet, second triode amplifies voltage signal, so just operating power can be provided externally, has also improved the load capacity of digital output certainly accordingly.3, the input/output port of this circuit is same port, has avoided the waste of I/O mouth, and can under the cooperation of software, make the user freely select input and output mode, and is very easy to use.

Description of drawings

Fig. 1 is existing digital input circuit schematic diagram.

Fig. 2 is existing digital output circuit schematic diagram.

Fig. 3 isolates bi-directional digital imput output circuit schematic diagram for band of the present invention.

Fig. 4 isolates bi-directional digital imput output circuit Saber artificial circuit for band of the present invention.

Embodiment

Further specify embodiments of the invention below in conjunction with accompanying drawing.

The second optocoupler U1, the first optocoupler U2 bear the isolation of numeral output, digital input signals respectively.When port the time as digital output mode; It is high level that host computer or keyboard are provided with the I/O mouth, and this moment, CPLD output drive signal DO DRIVE was a high level, first triode Q1 conducting this moment; The collector electrode of the first triode Q1 is pulled down to the 0.7V effect; The light-emitting diode conducting of the second optocoupler U1, VCC voltage is loaded into the I/O mouth through phototriode and the second triode Q2 composition common collector amplifying circuit of the second optocoupler U1, realizes digital output function.When port the time as digital input pattern; External voltage is added on the IO port; The bleeder circuit of being made up of resistance R 7, R8 makes the light-emitting diode conducting of the optocoupler U2 that wins; The phototriode work of the first optocoupler U2 makes the voltage VDD of digital input signals CDI become 0.7V, oppositely realizes the variation of digital input signals again through Programmable Logic Controller CPLD.Numeral output drive signal DO DRIVE and digital input signals CDI carry out bus and latch in CPLD.

In the present embodiment, the Standard resistance range of first current-limiting resistance is 66 Ω-3300 Ω; The Standard resistance range of the 3rd current-limiting resistance is 100 Ω-500 Ω.

Public one of digital input/output port of the present invention, the pattern of port is selected by software, the user is had select the space more freely.

Circuit simulation experiment of the present invention is as shown in Figure 4; It includes the I/O mouth; I/O mouth external load resistance R L, the I/O mouth is connected with the emitter of triode q2, and the base stage of triode q2 is connected with the emitter of triode q2 through resistance r2; The collector electrode of triode q2 is connected with the collector electrode of the phototriode of optocoupler U1; The collector electrode of triode q2 is connected with voltage VCC, and the base stage of triode q2 is connected with the emitter of the phototriode of optocoupler U1, and the anode of optocoupler U1 is connected with voltage VCC; The parallel connection back of the anode connecting resistance r9 of optocoupler U1 and electric capacity c3 is connected with the negative electrode of optocoupler U1; The negative electrode of optocoupler U2 is connected the back and is connected with the collector electrode of triode q1 with the 3rd current-limiting resistance r8, the grounded emitter of triode q1, and the base stage of triode q1 links to each other with signal generator V_pulse after current-limiting resistance r3 connection and is driven by it control figure and exports.

Through Saber software circuit is carried out emulation, all parameters are all set by actual requirement in the circuit.Obtain table one simulation result according to different loads RL.

Table one Saber simulation result VCC=24V

In the table: RL: load resistance; W _RL: load power consumption; UO: output voltage; I _RL: load current.Can find out by test result, guarantee the precision of output voltage ± 5%, can be with in theory and carry 1.5A.

The actual band of circuit of the present invention carries experiment

Carry out on the high-performance transducer EC550 product of this experiment based on Wisdri's research and development production; Method adds a slide rheostat (firm and hard existing by test fixture) at the I/O end makes load change to 90 Ω from 1M Ω, records the digital quantity output characteristic shown in table two through ammeter.

Table two, actual band carry experimental result VCC=22.47

In the table: RL: load resistance; W _RL: load power consumption; UO: output voltage; I _RK: load current.

Experiment is linked on the frock plate and is tested, and the VCC of this moment is the precision that 22.47V. considers output voltage ± 5%, can be loaded into 164mA.

Further verified the feasibility of circuit of the present invention through test and emulation.Digital in-output circuit under more original technology, visible circuit of the present invention can make things convenient for the user to dispose and save I/O quantity under the prerequisite that does not reduce product function; Adopt full isolation method to improve reliability; The load driving power extension product scope of application can externally be provided, also improve competitiveness of product simultaneously.

The above; Only being preferred embodiment of the present invention, is not that the present invention is done any pro forma restriction, and those skilled in the art utilize the technology contents of above-mentioned announcement to make a little simple modification; Equivalent variations or modification all drop in protection scope of the present invention.