CN101895290A - Level converting circuit - Google Patents
Level converting circuit Download PDFInfo
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- CN101895290A CN101895290A CN2009100572847A CN200910057284A CN101895290A CN 101895290 A CN101895290 A CN 101895290A CN 2009100572847 A CN2009100572847 A CN 2009100572847A CN 200910057284 A CN200910057284 A CN 200910057284A CN 101895290 A CN101895290 A CN 101895290A
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Abstract
The invention discloses a level converting circuit which comprises two level converting modules, wherein the first level converting module comprises a first input resistor and a first optical coupler, and the first input resistor is connected in series with an anode or a cathode of an LED in the first optical coupler; the second level converting module comprises a second input resistor and a second optical coupler; the anode of the LED in the second optical coupler is connected with an emitting electrode of a phototriode in the first optical coupler; the second input resistor is connected between the emitting electrode of the phototriode in the first optical coupler and the anode of the LED in the second optical coupler or connected to the cathode of the LED of the second optical coupler; a resistance value of the first input resistor is set to ensure that an input level of an input point is larger than a critical detectable level of a first system; and a resistance value of the second input resistor is set to ensure that the phototriode in the second optical coupler is saturated and conducted. The circuit of the invention is particularly suitable for critical low-level shunt conversion.
Description
Technical field
The present invention relates to a kind of level shifting circuit.
Background technology
Employed PLC control appliance in the factory at home at present, having much is the product of the seventies in last century, as the CP80 series of German AEG company.The operating voltage of these equipment is generally 60V, and the detectable significant level of input point is 10～60V.Since use of the remote past, aging circuit, reasons such as signal source load capacity reduction have only 10～11V in the signal level of some input point of these equipment, are in that these equipment are critical to be detected near the level.
Along with factory to automaticity require growing, inevitable requirement is transformed original system, but improvement cost is too high sometimes, this just needs to increase the advanced control system of an other cover, reach requirement, to remedy the defective of original system to many-sided control such as safety, production, logistics.In this case, often need signal along separate routes from the input point of legacy system, carry out level conversion after, import new system (operating voltage is generally 24V).
On the basis of original system 20, increase the new system 30 of a cover, satisfy requirement, when needs carry out level conversion to signal, adopt mode as shown in Figure 1 mostly many-sided control such as safety, production, logistics.Because it is of the remote past, drawing is preserved reasons such as imperfect, in the time of need obtaining original signal 10 in the time of most of, be directly original signal to be carried out shunt, and the signal that comes out along separate routes converted to by a level converter 40 import new PLC system 30 behind the required level at the input point place of former PLC system 20.
The method is effective when normal signal level is carried out shunt transition.But, for the signal that is in the critical low-level state, can reduce the signal strength signal intensity of original signal, influence the stability of original system.
Figure 2 shows that PLC input point circuit and level converter circuit theory schematic diagram.In level converter, generally adopt the light-coupled isolation mode, and in order to keep the normally of optocoupler, the electric current that optocoupler is flow through in requirement is 6～10mA, can guarantee the saturation conduction of optocoupler output, reduce the pressure drop between optocoupler output collector electrode and emitter, reduce changing the influence of back level.Just owing to this requirement, the input resistance of general level converter is smaller.For example, when input signal is 60V,, also just require the input resistance of level converter can not surpass 6k Ω in order to satisfy the conducting electric current of 10mA.This has just equaled in former PLC input point place's parallel connection a resistance, reduced the resistance at this input point place, also just reduced the output loading of signal source, also just reduced the voltage at this input point place, cause gather at these input point places critical when detecting level, can cause the level subcritical level of input point, make old equipment can't normally detect level signal.
And if the input resistance of level converter is strengthened, though can reduce influence to signal level, but can cause input current to reduce, cause the optocoupler in the level converter can't saturation conduction, cause the output pressure drop of optocoupler to strengthen, also just reduce output voltage, can cause new PLC equipment can't detect level signal.For example, the detectable significant level of Siemens S7 series input module is 13～24V, but reliable detectable level range is 18～24V.If the output pressure drop at optocoupler surpasses 6V, Siemens PLC C system just might detect less than this signal.
Summary of the invention
The technical problem to be solved in the present invention provides a kind of level shifting circuit, and it can convert required level signal to new system desired level under the prerequisite that does not influence legacy system stable operation.
For solving the problems of the technologies described above, level shifting circuit of the present invention is used for the incoming level of the input point of first system is converted to the required operation level of second system:
Comprise first level switch module and second level switch module;
Described first level switch module comprises first input resistance and first optical coupler, the both positive and negative polarity of incoming level is connected to light-emitting diode positive pole and the negative pole in described first optical coupler respectively, and described first input resistance is serially connected in the positive pole of the light-emitting diode in described first optical coupler or the negative pole of the light-emitting diode in described first optical coupler;
Described second level switch module comprises second input resistance and second optical coupler, the positive pole of the light-emitting diode in described second optical coupler connects the emitter of the phototriode in described first optical coupler, light-emitting diode minus earth in described second optical coupler, photosensitive triode emitter outputs level signals in described second optical coupler is given described second system, described second input resistance is connected between the emitting stage and the light-emitting diode positive pole in described second optical coupler of the phototriode in described first optical coupler, or is connected to the light-emitting diode negative pole in described second optical coupler;
The resistance of described first input resistance is made as the incoming level that the makes input point critical level that detects greater than described first system, and the resistance of described second input resistance is made as the phototriode saturation conduction that makes in described second optical coupler.
Level shifting circuit of the present invention adopts the two-stage isolation design.In order to solve signal along separate routes to the influence of original signal intensity, the first order adopts big input resistance, can reduce the influence to original signal to the full extent.In the case, first order optocoupler does not have saturation conduction, and is bigger at the pressure drop ratio of optocoupler output.Therefore, second level optocoupler adopts little input resistance according to the output pressure drop of first order optocoupler, does not have under the situation of saturation conduction to guarantee last aurora coupling, still can guarantee the saturation conduction of the second aurora coupling.Like this, can be under the prerequisite that does not influence former level signal, guarantee that the required level signal of the new system of output gives new PLC system.Therefore, the present invention realizes level conversion to signal under situation about at utmost reducing the influence of former critical low-level signal.
Description of drawings
The present invention is further detailed explanation below in conjunction with accompanying drawing and embodiment:
Fig. 1 is concrete application system schematic diagram of level shifting circuit;
Fig. 2 is signal input point circuit and level converter circuit diagram;
Fig. 3 is of the present invention one concrete level shifting circuit.
Embodiment
Level shifting circuit of the present invention is used under the situation that increases the new system of a cover on the basis of original system, with the signal of the input point in the original system along separate routes, and is the new system of input behind the required operation level of new system with this conversion of signals.The present invention adopts the two-stage isolation design, reduces to the full extent under the influence to former critical low-level signal, described conversion of signals can be become the desired level of new system.
Of the present invention one concrete level shifting circuit (see figure 3) comprises two level switch modules, first level switch module and second level switch module;
First level switch module comprises the first input resistance R1 and the first optical coupler UA1, the termination of the first input resistance R1 is from the incoming level of input point, the other end of R1 is connected to the light-emitting diode positive pole among the first optical coupler UA1, it is leg 1, light-emitting diode negative pole among the first optical coupler UA1 (being leg 2) connects the negative pole of input signal, phototriode collector electrode 16 among the first optical coupler UA1 connects power supply, and emitter 15 meets the second input resistance R2 in second level switch module;
Second level switch module comprises the second input resistance R2 and the second optical coupler UB1, photosensitive triode emitter 15 among a termination first optical coupler UA1 of the second input resistance R2, light-emitting diode positive pole 3 among another termination second optical coupler UB1 of the second input resistance R2, light-emitting diode negative pole 4 ground connection in second optical coupler, the level signal after the phototriode emitter 13 among the second optical coupler UB1 will be changed is exported to new system.
In level shifting circuit of the present invention, the resistance of the first input resistance R1 is made as higher value, it can guarantee critical the detect level of the incoming level of input point greater than original system, and the resistance of the second input resistance R2 should be made as smaller value according to the output pressure drop of first order optocoupler, can guarantee the phototriode saturation conduction in second optical coupler.
In level shifting circuit of the present invention, also be provided with three light-emitting diodes, be used for intuitively showing current signal, be respectively and before the first input resistance R1, be connected to the first light-emitting diode DS1, between the first optical coupler phototriode emitter 15 and the second input resistance R2, be provided with the second light-emitting diode DS2, and after the phototriode emitter 13 of second optical coupler, be provided with the 3rd light-emitting diode DS3.
Level shifting circuit of the present invention, in order to solve the influence of signal shunt to original signal intensity, the resistance of the input resistance in the first order should be made as and can guarantee to make critical the detect level of the incoming level of input point greater than original system, here the first input resistance R1 should be made as big resistance, as adopt 10k Ω, can reduce influence to the full extent, guarantee the stability of original system original signal.And in the case, first order optocoupler does not have saturation conduction, so bigger at the pressure drop ratio of optocoupler output.And the resistance of partial input resistance should be made as the saturation conduction that can guarantee second level optocoupler, the second concrete input resistance R2 should be made as smaller value according to the output pressure drop of first order optocoupler, as adopt 1k Ω, guarantee that last aurora coupling does not have under the situation of saturation conduction, still can be the second aurora coupling provides the electric current of 6～10mA, guarantees the saturation conduction (saturation conduction of the second aurora coupling means the pressure drop minimum between terminals 13 and the terminals 14) of the second aurora coupling.Like this, being equipped with of two input resistances makes can be under the prerequisite that does not influence former level signal, and the level signal that guarantees output 18～24V is given new PLC system.
The first input resistance R1 among the present invention also can be serially connected in the negative pole (being leg 2 ends) of the light-emitting diode among the first optical coupler UA1, and the second input resistance R2 can be serially connected in the negative pole (being leg 4 ends) of the light-emitting diode among the second optical coupler UA1.
Claims (3)
1. level shifting circuit is used for the incoming level of the input point of first system is converted to the required operation level of second system, it is characterized in that:
Comprise first level switch module and second level switch module;
Described first level switch module comprises first input resistance and first optical coupler, the both positive and negative polarity of incoming level is connected to light-emitting diode positive pole and the negative pole in described first optical coupler respectively, and described first input resistance is serially connected in the positive pole of the light-emitting diode in described first optical coupler or the negative pole of the light-emitting diode in described first optical coupler;
Described second level switch module comprises second input resistance and second optical coupler, the positive pole of the light-emitting diode in described second optical coupler connects the emitter of the phototriode in described first optical coupler, light-emitting diode minus earth in described second optical coupler, photosensitive triode emitter outputs level signals in described second optical coupler is given described second system, described second input resistance is connected between the emitting stage and the light-emitting diode positive pole in described second optical coupler of the phototriode in described first optical coupler, or is connected to the light-emitting diode negative pole in described second optical coupler;
The resistance of described first input resistance is made as the incoming level that the makes input point critical level that detects greater than described first system, and the resistance of described second input resistance is made as the phototriode saturation conduction that makes in described second optical coupler.
2. level shifting circuit as claimed in claim 1, it is characterized in that: the positive pole of the light-emitting diode in described first optical coupler is serially connected with first light-emitting diode, the positive pole of the light-emitting diode in described second optical coupler is serially connected with second light-emitting diode, is serially connected with the 3rd light-emitting diode in described second optical coupler after the emitter of phototriode.
3. level shifting circuit as claimed in claim 1 is characterized in that: the collector electrode of the photosensitive triode in the collector electrode of the phototriode in described first optical coupler and described second optical coupler connects power supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100572847A CN101895290A (en) | 2009-05-20 | 2009-05-20 | Level converting circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100572847A CN101895290A (en) | 2009-05-20 | 2009-05-20 | Level converting circuit |
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| Publication Number | Publication Date |
|---|---|
| CN101895290A true CN101895290A (en) | 2010-11-24 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009100572847A Pending CN101895290A (en) | 2009-05-20 | 2009-05-20 | Level converting circuit |
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| CN (1) | CN101895290A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040026621A1 (en) * | 2002-05-31 | 2004-02-12 | Hayn Armin Heinz | Particle detectors |
| CN1719958A (en) * | 2004-12-31 | 2006-01-11 | 彭洲龙 | Energy-savig long-life LED illuminating lamp and mfg. method thereof |
| CN2872496Y (en) * | 2006-03-07 | 2007-02-21 | 李荣泰 | Photoelectric isolator |
-
2009
- 2009-05-20 CN CN2009100572847A patent/CN101895290A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20040026621A1 (en) * | 2002-05-31 | 2004-02-12 | Hayn Armin Heinz | Particle detectors |
| CN1719958A (en) * | 2004-12-31 | 2006-01-11 | 彭洲龙 | Energy-savig long-life LED illuminating lamp and mfg. method thereof |
| CN2872496Y (en) * | 2006-03-07 | 2007-02-21 | 李荣泰 | Photoelectric isolator |
Non-Patent Citations (1)
| Title |
|---|
| 张东旭等: "《DALI系统电平转换电路的实现》", 《低压电器》 * |
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Application publication date: 20101124 |