CN104716953A - Two-wire system field bus power decoupling circuit - Google Patents
Two-wire system field bus power decoupling circuit Download PDFInfo
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- CN104716953A CN104716953A CN201410852851.9A CN201410852851A CN104716953A CN 104716953 A CN104716953 A CN 104716953A CN 201410852851 A CN201410852851 A CN 201410852851A CN 104716953 A CN104716953 A CN 104716953A
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Abstract
The invention discloses a two-wire system field bus power decoupling circuit. The two-wire system field bus power decoupling circuit arranged at the low-voltage end of a bus comprises an operation amplifier, an N type switching tube, a first resistor, a second resistor, a first capacitor and a biasing circuit. The in-phase input end of the operation amplifier is connected into the low-voltage end of two-wire system field bus through the first resistor, an anti-phase input end of the operation amplifier is connected into the low-voltage end through the first capacitor, and the output end of the operation amplifier is connected into the control electrode of the N type switching tube. The input electrode of the N type switching tube is connected with the in-phase input end of the operation amplifier, and the output electrode of the N type switching tube is connected with the negative electrode of a bus power source. The positive input end and the negative input end of the biasing circuit are connected to the bus power source, the output end of the biasing circuit is connected into the anti-phase input end of the operation amplifier through the second resistor, and the small size and the high integration of the two-wire system field bus power decoupling circuit are achieved.
Description
Technical field
The present invention relates to technical field of automation in industry, more particularly, relate to two-wire system fieldbus power source deoupling circuit.
Background technology
Two-wire system fieldbus (such as FF bus and Profibus-PA bus) is the focus of industrial automation research, and its outstanding advantage is, can realize the transmission of signal and electric energy on same bus transmission line simultaneously.
The two ends of described bus are provided with terminal impedance, and described terminal impedance has two effects: one is the coupling to bus characteristics impedance; Two is convert bus modulated current to bus voltage signal.
Two-wire system fieldbus power source deoupling circuit is installed between described bus and DC source (i.e. bus power source), the AC impedance of this circuit is far longer than described terminal impedance, DC source bus modulated current can being avoided to flow to AC impedance be less than described terminal impedance.In addition, for reducing the power consumption of DC source, the DC impedance of described two-wire system fieldbus power source deoupling circuit should be as far as possible little.Based on this 2 point, prior art is designed to two-wire system fieldbus power source deoupling circuit the structure of inductance and resistant series usually, and this cascaded structure can be arranged on bus low-voltage end, as shown in Figure 1a, also can be arranged on bus high voltage end, as shown in Figure 1 b.
But the representative value of signal transmission rate is 31.25kbit/s in bus, undistorted for ensureing signal, usually require that the inductance value of two-wire system fieldbus power source deoupling circuit is not less than 5mH, the inductance coil number of turn can be many thus; In addition, the direct current in bus is comparatively large, and therefore in two-wire system fieldbus power source deoupling circuit, the wire diameter of inductance will design thicker; And the magnetic core of large volume just must be selected to meet these two conditions simultaneously, the inductance component causing final design to go out is bulky, is unfavorable for very much small size and the high integration of two-wire system fieldbus power source deoupling circuit.
Summary of the invention
In view of this, the invention provides a kind of two-wire system fieldbus power source deoupling circuit, to realize small size and the high integration of two-wire system fieldbus power source deoupling circuit.
A kind of two-wire system fieldbus power source deoupling circuit, comprises operational amplifier, N type switch tube, the first resistance, the second resistance, the first electric capacity and biasing circuit, wherein:
The in-phase input end of described operational amplifier accesses the low-voltage end of two-wire system fieldbus through described first resistance, its inverting input accesses described low-voltage end through described first electric capacity, and its output accesses the control pole of described N type switch tube;
The input pole of described N type switch tube connects the in-phase input end of described operational amplifier, and its output stage connects the negative pole of bus power source;
The positive-negative input end of described biasing circuit is connected in described bus power source, and the output of described biasing circuit accesses the inverting input of described operational amplifier through described second resistance.
Wherein, described biasing circuit comprises the 3rd resistance, diode and the second electric capacity, wherein:
Described 3rd resistance connects the positive pole of described bus power source and the anode of described diode;
The negative electrode of described diode connects the negative pole of described bus power source;
Described second Capacitance parallel connection is on described diode.
Wherein, described N type switch tube is NPN type triode.
Wherein, described N type switch tube is NMOS tube.
Wherein, described N type switch tube is N-type Darlington transistor.
A kind of two-wire system fieldbus power source deoupling circuit, comprises operational amplifier, P type switching tube, the first resistance, the second resistance, the first electric capacity and biasing circuit, wherein:
The high voltage end of the output stage access two-wire bus of described P type switching tube, its input pole is through the positive pole of described first resistance access bus power source, and it controls the output that pole connects described operational amplifier;
The input pole of P type switching tube described in the positive input termination of described biasing circuit, the negative pole of bus power source described in its negative input termination, it exports the inverting input of operational amplifier described in termination;
The in-phase input end of described operational amplifier accesses the positive pole of described bus power source through described first electric capacity, and accesses the output stage of described P type switching tube through described second resistance.
Wherein, biasing circuit comprises the 3rd resistance, diode and the second electric capacity, wherein:
Described 3rd resistance connects the negative pole of described bus power source and the negative electrode of described diode;
The anode of described diode connects the positive pole of described bus power source;
Described second Capacitance parallel connection is on described diode.
Wherein, described P type switching tube is PNP type triode.
Wherein, described P type switching tube is PMOS.
Wherein, described P type switching tube is P type Darlington transistor.
As can be seen from above-mentioned technical scheme, the present invention utilizes operational amplifier, switching tube, resistance, electric capacity and biasing circuit to build two-wire system fieldbus power source deoupling circuit, and this circuit is with directly equivalent by the two-wire system fieldbus power source deoupling circuit of inductance and resistant series.Compared to prior art, the present invention does not arrange inductance component, therefore there is not the problem that inductance component in two-wire system fieldbus power source deoupling circuit is bulky, achieves small size and the high integration of two-wire system fieldbus power source deoupling circuit.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to the accompanying drawing provided.
Fig. 1 a is a kind of two-wire system fieldbus power source deoupling circuit structural representation being arranged on bus low-voltage end disclosed in prior art;
Fig. 1 b is a kind of two-wire system fieldbus power source deoupling circuit structural representation being arranged on bus high voltage end disclosed in prior art;
Fig. 2 is a kind of two-wire system fieldbus power source deoupling circuit structural representation being arranged on bus low-voltage end disclosed in the embodiment of the present invention;
Fig. 3 is for being applied in the bias circuit construction schematic diagram in the fieldbus of two-wire system shown in Fig. 2 power source deoupling circuit;
The two bar current path schematic diagrames of Fig. 4 for being in parallel in the fieldbus of two-wire system shown in Fig. 2 power source deoupling circuit;
Fig. 5 is a kind of two-wire system fieldbus power source deoupling circuit structural representation being arranged on bus high voltage end disclosed in the embodiment of the present invention;
Fig. 6 is for being applied in the bias circuit construction schematic diagram in the fieldbus of two-wire system shown in Fig. 5 power source deoupling circuit;
The two bar current path schematic diagrames of Fig. 7 for being in parallel in the fieldbus of two-wire system shown in Fig. 5 power source deoupling circuit.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
See Fig. 2, the embodiment of the invention discloses a kind of two-wire system fieldbus power source deoupling circuit, this circuit is arranged on bus low-voltage end, small size and the high integration of two-wire system fieldbus power source deoupling circuit can be realized, specifically comprise operational amplifier A, N type switch tube Q, the first resistance R1, the second resistance R2, the first electric capacity C1 and biasing circuit Bias, wherein:
The in-phase input end of operational amplifier A accesses the low-voltage end of two-wire system fieldbus through the first resistance R1, its inverting input accesses described low-voltage end through the first electric capacity C1, the control pole of its output access N type switch tube Q;
The input pole of N type switch tube Q connects the in-phase input end of operational amplifier A, and its output stage connects the negative pole of bus power source E;
The positive-negative input end of biasing circuit Bias is connected on bus power source E, and the output of biasing circuit Bias accesses the inverting input of operational amplifier A through the second resistance R2.
Biasing circuit Bias in the present embodiment is used for providing quiescent point, namely, the introducing of biasing circuit Bias is to provide suitable direct current biasing to N type switch tube Q, thus described two-wire system fieldbus power source deoupling circuit is regulated in rational voltage change range, ensure that the signal in bus is undistorted.V shown in Fig. 2
+and V
-represent the generating positive and negative voltage of bus power source E respectively, Vref represents the DC offset voltage that biasing circuit Bias exports, and described Vref is with V
-as a reference point.
The implementation of biasing circuit Bias is various, and Fig. 3 only gives the comparatively simple topological structure of one, and it comprises the 3rd resistance R3, diode D and the second electric capacity C2, wherein:
3rd resistance R3 connects the positive pole of bus power source E and the anode of diode D;
The negative electrode of diode D connects the negative pole of bus power source E;
Second electric capacity C2 is connected in parallel on diode D.
In the biasing circuit Bias shown in Fig. 3, the anode of diode D is the output of biasing circuit Bias, for exporting DC offset voltage Vref.Described Vref is with the negative pole V of bus power source E
-as a reference point, Vref=Vd+V
-(Vd is the forward conduction voltage drop of diode D to=Vd, its representative value is 0.6 ~ 0.7 volt), in alternating current path, because Vref is a constant pressure drop, it is for alternating current circuit change in voltage without any contribution, and therefore in alternating current path, visual its exchanges pressure drop is 0.In addition, biasing circuit Bias also can adopt special reference data chip to realize.
N type switch tube Q in the present embodiment can adopt NPN type triode (Fig. 2 only with N type switch tube Q for NPN type triode exemplarily), N-type Darlington transistor or NMOS (N-Metal OxideSemiconductor FET, n channel metal oxide semiconductor field effect transistor).When N type switch tube Q be NPN type triode or N-type Darlington transistor time, the control very base stage of N type switch tube Q, the input very collector electrode of N type switch tube Q, the output very emitter of N type switch tube Q.When N type switch tube Q is NMOS, the control very grid of N type switch tube Q, the input of N type switch tube Q very drains, the output very source electrode of N type switch tube Q.
Below, based on above-mentioned open, circuit analysis is done to described two-wire system fieldbus power source deoupling circuit.
The topological structure of described two-wire system fieldbus power source deoupling circuit meets profound and negative feedbck, and " empty short " and " empty disconnected " characteristic of operational amplifier A therefore can be utilized to do circuit analysis.Wherein, so-called " empty short ", namely the in-phase input end of operational amplifier A is equal with the voltage of inverting input; So-called " empty disconnected ", namely the in-phase input end of operational amplifier A and the input current of inverting input are zero.
First set the bus access point of described two-wire system fieldbus power source deoupling circuit as M, if the alternating voltage of M point is u; If the alternating current on R1 is I1, if the alternating current on C1 is I2, so:
Known according to " empty short ", it is equal that the interchange pressure drop of R1 two ends and C1 two ends exchange pressure drop, namely
(formula 1.1);
According to " empty disconnected ", known, enter viewed from bus access point M, have the negative pole V that two current paths lead to DC power supply E
-(as the black of two in Fig. 4 adds shown in thick line), therefore meet following 1)-2),
1) on this current path at C1 place, because Vref is 0 to the contribution of alternating voltage, therefore C1 with R2 two ends exchange pressure drop sum and equal u, namely
(formula 1.2);
2) these two current paths are parallel relationship, the input impedance Z=u/ (I1+I2) (formula 1.3) therefore entered viewed from bus access point M.
Aggregative formula 1.1-formula 1.3, can derive
Analyze known, as R1*C1*w<<1, Z ≈ R1+R1*R2*C1*wj=R1+L*wj (wherein, L=R1*R2*C1).That is, when R1*C1*w<<1, described two-wire system fieldbus power source deoupling circuit is equivalent to the series connection of a first resistance R1 and inductance L (induction reactance size is R1*R2*C1), the equivalence of it and existing two-wire system fieldbus power source deoupling circuit, and the puzzlement not having inductance component bulky.
See Fig. 5, the embodiment of the invention discloses another two-wire system fieldbus power source deoupling circuit, this circuit is arranged on bus high voltage end, small size and the high integration of two-wire system fieldbus power source deoupling circuit can be realized, specifically comprise operational amplifier A, P type switching tube Q, the first resistance R1, the second resistance R2, the first electric capacity C1 and biasing circuit Bias, wherein:
The high voltage end of the output stage access two-wire bus of P type switching tube Q, its input pole first resistance R1 accesses the positive pole of bus power source E, and it controls the output that pole connects operational amplifier A;
The input pole of the positive input termination P type switching tube Q of biasing circuit Bias, the negative pole of its negative input termination bus power source E, it exports the inverting input of termination operational amplifier A;
The in-phase input end of operational amplifier A accesses the positive pole of bus power source E through the first electric capacity C1, and accesses the output stage of P type switching tube Q through the second resistance R2.
Biasing circuit Bias in the present embodiment is used for providing quiescent point, that is, the introducing of biasing circuit Bias is to provide suitable direct current biasing to P type switching tube Q.V shown in Fig. 5
+and V
-represent the generating positive and negative voltage of bus power source E respectively, Vref represents the DC offset voltage that biasing circuit Bias exports, and described Vref is as a reference point with the node N on the right side of the first resistance R1, and note N point current potential is V
n.
The implementation of biasing circuit Bias is various, and Fig. 6 only gives the comparatively simple topological structure of one, and it comprises the 3rd resistance R3, diode D and the second electric capacity C2, wherein:
3rd resistance R3 connects the negative pole of bus power source E and the negative electrode of diode D;
The anode of diode D connects the positive pole of bus power source E;
Second electric capacity C2 is connected in parallel on diode D.
In the biasing circuit Bias shown in Fig. 6, the negative electrode of diode D is the output of biasing circuit Bias, for providing DC offset voltage Vref.Described Vref is as a reference point with N, Vref=V
n-Vd (wherein Vd is the forward conduction voltage drop of diode D, and its representative value is 0.6 ~ 0.7 volt), same, in alternating current path, because Vref is a constant pressure drop, its contribution for alternating voltage is 0, and therefore in alternating current path, visual its exchanges pressure drop is 0.In addition, biasing circuit Bias also can adopt special reference data chip to realize.
P type switching tube Q in the present embodiment can adopt PNP type triode (Fig. 5 only with P type switching tube Q for PNP type triode exemplarily), P type Darlington transistor or PMOS (P-Metal Oxide SemiconductorFET, P-channel metal-oxide-semiconductor field-effect transistor).When P type switching tube Q be PNP type triode or P type Darlington transistor time, the control very base stage of P type switching tube Q, the input very emitter of P type switching tube Q, the output very collector electrode of P type switching tube Q.When P type switching tube Q is PMOS, the control very grid of P type switching tube Q, the input of P type switching tube Q very drains, the output very source electrode of P type switching tube Q.
The topological structure of described two-wire system fieldbus power source deoupling circuit meets profound and negative feedbck, and " empty short " and " empty disconnected " characteristic of operational amplifier A therefore can be utilized to do circuit analysis.Concrete:
First set the bus access point of described two-wire system fieldbus power source deoupling circuit as M, if M point is u relative to the interchange pressure drop of V+; If the alternating current on R1 is I1, if the alternating current on C1 is I2, so:
Known according to " empty short ", the alternating voltage contributed in alternating current path due to Vref is 0, and therefore R1 two ends exchange pressure drop and C1 two ends to exchange pressure drop equal, namely
(formula 1.1);
According to " empty disconnected ", known, from the positive pole V of DC power supply E
+see into, have two current paths and lead to bus access point M (as the black of two in Fig. 7 adds shown in thick line), therefore meet following 1)-2),
1) by the current path that C1 and R2 is formed, C1 with R2 two ends exchange pressure drop sum and equal V
+-u take V+ as alternating voltage reference zero point, so,
(formula 1.2);
2) these two current paths are parallel relationship, therefore from the positive pole V of DC power supply E
+the input impedance Z=(-u) seen into/(I1+I2) (formula 1.3);
Aggregative formula 1.1-formula 1.3, has
Analyze known, as R1*C1*w<<1, Z ≈-(R1+R1*R2*C1*wj)=-(R1+L*wj) (wherein, L=R1*R2*C1).That is, when R1*C1*w<<1, described two-wire system fieldbus power source deoupling circuit is equivalent to the cascaded structure of a first resistance R1 and inductance L (induction reactance size is R1*R2*C1), with existing two-wire system fieldbus power source deoupling circuit equivalence, and the puzzlement not having inductance component bulky.
In sum, the present invention utilizes operational amplifier, switching tube, resistance, electric capacity and biasing circuit to build two-wire system fieldbus power source deoupling circuit, and this circuit is with directly equivalent by the two-wire system fieldbus power source deoupling circuit of inductance and resistant series.Compared to prior art, the present invention does not arrange inductance component, therefore there is not the problem that inductance component volume in two-wire system fieldbus power source deoupling circuit is too large, achieves small size and the high integration of two-wire system fieldbus power source deoupling circuit.
To the above-mentioned explanation of the disclosed embodiments, professional and technical personnel in the field are realized or uses the present invention.To be apparent for those skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein can without departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.
Claims (10)
1. a two-wire system fieldbus power source deoupling circuit, is characterized in that, comprises operational amplifier, N type switch tube, the first resistance, the second resistance, the first electric capacity and biasing circuit, wherein:
The in-phase input end of described operational amplifier accesses the low-voltage end of two-wire system fieldbus through described first resistance, its inverting input accesses described low-voltage end through described first electric capacity, and its output accesses the control pole of described N type switch tube;
The input pole of described N type switch tube connects the in-phase input end of described operational amplifier, and its output stage connects the negative pole of bus power source;
The positive-negative input end of described biasing circuit is connected in described bus power source, and the output of described biasing circuit accesses the inverting input of described operational amplifier through described second resistance.
2. two-wire system fieldbus power source deoupling circuit according to claim 1, is characterized in that, described biasing circuit comprises the 3rd resistance, diode and the second electric capacity, wherein:
Described 3rd resistance connects the positive pole of described bus power source and the anode of described diode;
The negative electrode of described diode connects the negative pole of described bus power source;
Described second Capacitance parallel connection is on described diode.
3. two-wire system fieldbus power source deoupling circuit according to claim 1, is characterized in that, described N type switch tube is NPN type triode.
4. two-wire system fieldbus power source deoupling circuit according to claim 1, is characterized in that, described N type switch tube is NMOS tube.
5. two-wire system fieldbus power source deoupling circuit according to claim 1, is characterized in that, described N type switch tube is N-type Darlington transistor.
6. a two-wire system fieldbus power source deoupling circuit, is characterized in that, comprises operational amplifier, P type switching tube, the first resistance, the second resistance, the first electric capacity and biasing circuit, wherein:
The high voltage end of the output stage access two-wire bus of described P type switching tube, its input pole is through the positive pole of described first resistance access bus power source, and it controls the output that pole connects described operational amplifier;
The input pole of P type switching tube described in the positive input termination of described biasing circuit, the negative pole of bus power source described in its negative input termination, it exports the inverting input of operational amplifier described in termination;
The in-phase input end of described operational amplifier accesses the positive pole of described bus power source through described first electric capacity, and accesses the output stage of described P type switching tube through described second resistance.
7. two-wire system fieldbus power source deoupling circuit according to claim 6, is characterized in that, biasing circuit comprises the 3rd resistance, diode and the second electric capacity, wherein:
Described 3rd resistance connects the negative pole of described bus power source and the negative electrode of described diode;
The anode of described diode connects the positive pole of described bus power source;
Described second Capacitance parallel connection is on described diode.
8. two-wire system fieldbus power source deoupling circuit according to claim 6, is characterized in that, described P type switching tube is PNP type triode.
9. two-wire system fieldbus power source deoupling circuit according to claim 6, is characterized in that, described P type switching tube is PMOS.
10. two-wire system fieldbus power source deoupling circuit according to claim 6, is characterized in that, described P type switching tube is P type Darlington transistor.
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| CN201410852851.9A CN104716953A (en) | 2014-12-31 | 2014-12-31 | Two-wire system field bus power decoupling circuit |
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