CN1053535C - Isolated amplifier - Google Patents
Isolated amplifier Download PDFInfo
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- CN1053535C CN1053535C CN94107446A CN94107446A CN1053535C CN 1053535 C CN1053535 C CN 1053535C CN 94107446 A CN94107446 A CN 94107446A CN 94107446 A CN94107446 A CN 94107446A CN 1053535 C CN1053535 C CN 1053535C
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Abstract
The present invention relates to an isolated amplifier, which is used for transmitting and amplifying an electrical signal under the condition that an output terminal and an input terminal require favorable electric insulation. The present invention has the technical scheme that a feedback method is utilized to enhance linearity and reduce requirement of components; a feedback circuit and an output circuit are symmetrical; a current signal and a current-limiting resistor which is arranged on the basis of double diode rectification are adopted to overcome the discreteness of the performance of a diode; a modulator in an input circuit is composed of a transistor, a diode and a capacitor; a modulation circuit converts a deviation signal into excitation current so as to be supplied to an excitation winding of a coupling transformer.
Description
The present invention relates to electronic amplification circuit, particularly the amplifying circuit of its output and input isolation.
Isolated amplifier is to be used for transmission, amplification signal, and guaranteeing simultaneously has the excellent electric insulating energy between its output and the input.It has wide practical use in fields such as industrial instrument, power, medical treatment, and the subject matter that adopts isolated amplifier is the contradiction between performance and the price, and this contradiction is especially outstanding in the multi-channel detection of computer.It is to utilize the symmetry of feedback circuit and output circuit to reduce requirement to the components and parts performance index than the superior part of input modulation---transformer---the output demodulation principle of open loop type that isolated amplifier adopts the reaction type principle.There is a kind of reaction type isolated amplifier that three winding coupled transformers are arranged, wherein two windings provide feedback voltage and output voltage through two rectification circuits that are made of diode, capacitor and resistance respectively, the tertiary winding is accepted the driving voltage after the modulation that input circuit provides, the difference response of this driving voltage and input voltage and feedback voltage.But adopt voltage unfavorable to the operating state of the rectifier diode in feedback circuit and the output circuit as signal by usual practice, at this moment diode will be born bigger reverse voltage, and the leakage current that causes the thus particularly instability of leakage current will make feedback signal and output signal unbalanced and influence is linear.The difference of diode forward conducting voltage also can not be ignored in addition, and it is unbalanced and influence is linear that it also directly has influence on feedback signal and output signal.
The objective of the invention is to influence linear main factor on the basis of reaction type isolated amplifier---and the reverse leakage and the inconstant influence of forward voltage of diode are eliminated; Simplify modulator, make that isolated amplifier is simple in structure, cost reduces.
The present invention adopts current signal, feedback is exported with electric current, there are the serial connection diode pair and first capacitor that join with unlike pole to connect into triangular shape in the feedback circuit, the mid point of diode pair connects first end of first winding by first resistance, first end of first capacitor is the output of feedback current, and second end of first capacitor and second end of first winding join and be attempted by the common port of input circuit; Output circuit also has pair of diodes, a capacitor and a resistance, between them and the method for attachment of they and above-mentioned second winding identical with above-mentioned feedback circuit.The constructive method of the modulation circuit in the input circuit be by a transistor and between transistor collector and the emitter by a rightabout diode in parallel, indirect one second capacitor of first end of the collector electrode and the above-mentioned tertiary winding, emitter connects the common port of input circuit, is added with ac-excited voltage between second end of this common port and the above-mentioned tertiary winding.
Because diode pair is actually reversal connection in parallel, so the reverse voltage that diode bears will be no more than forward conduction voltage, so reverse leakage current just can be ignored in feedback circuit.Because diode pair has been connected in series the current-limiting resistance working point and has just improved, make coupling transformer high doubly more a lot of than Voltage Feedback formula to the voltage magnitude that feedback circuit and output circuit provide, so just make diode forward conducting voltage and total voltage amplitude more only account for a minimum share, so, the influence that difference produced of diode forward conducting voltage just can be ignored.The existence of current-limiting resistance also is improved antijamming capability after having improved the working point.
Modulator in the input circuit of known reaction type isolated amplifier is all more complicated of switching regulator or pulse-width modulation type, modulator of the present invention is simple especially, be added on the transistor base with direct voltage during work and change transistorized ducting capacity and reach control flows and cross the amplitude that capacitor just flows through the alternating current of coupling transformer excitation winding, thereby realize which amplitude modulation.
The description of the drawings:
The main body line map of Fig. 1 isolated amplifier
Fig. 2 voltage U
1Hour, the substitutional connection of modulation circuit
Fig. 3 voltage U
1When enough big, the substitutional connection of modulation circuit
The complete schematic diagram of Fig. 4 isolated amplifier
The detail explanation of optimum implementation:
Fig. 1 is an isolated amplifier line map, wherein has input circuit, coupling transformer 20, feedback circuit 30 and output circuit 40 to constitute.Coupling transformer 20 has three windings, and first winding 22 and second winding, 23 structures are symmetry substantially.First end of first termination, first resistance 31 of first winding 22, the second termination common port 12 of first winding 22, second of first resistance 31 terminates at a series diode that joins with unlike pole to 32,33 mid point, the diode pair and first capacitor 34 connect into triangular shape, and the input of the first termination input circuit of first capacitor 34 also is feedback current I
2The second termination common port 12 of output 11, the first capacitors 34.The input 11 of input circuit is the electric current comparison point, when the current potential of input 11 during very near the current potential of common port 12, and feedback current I
2Equal input current I
1Theoretical value, and its small deviation forms voltages at input 11, and produces a direct voltage U who is exaggerated at the output 14 of the amplifier 13 with high-gain
1, U
1Be applied in the base stage of transistor 15 and influence the ducting capacity of transistor 15.By opposite conducting direction diode 16 in parallel, connect a capacitor 17, ac-excited voltage U between first end of the winding 21 of collector electrode and coupling transformer 20 between the emitter of transistor 15 and the collector electrode
2The emitter that is applied to second end 18 of winding 21 and transistor 15 is just between the common port 12.
As above-mentioned direct voltage U
1When very little, transistor 15 not conductings, its substitutional connection because diode 16 and capacitor 17 are connected in series, do not have lasting electric current and occurs as shown in Figure 2 in the winding 21, and winding 22,23 can not induced potential.Work as voltage U
1When enough big, transistor 15 complete conductings, equivalence be a diode as shown in Figure 3, in winding 21, will produce the exciting current of maximum, the voltage U of inducting in the winding 22,23
3, U
4The amplitude maximum.In working order down, voltage U
3, U
4Amplitude be subjected to direct voltage U
1Control.
In feedback circuit 30,34 rectifications of diode 32,33 and capacitor, filter action, resistance 31 accounts for the voltage U of inducting in the winding 22 as current-limiting resistance
3The overwhelming majority of amplitude, voltage U
3Amplitude can be than diode forward conducting voltage up to nearly 50 times.Like this, feedback current I
2Be subjected to the influence of diode behavior discreteness hardly.Output circuit 40 and feedback circuit 30 be symmetry fully, and resistance 41 equates with the resistance of resistance 31.Node 45 is the output common port, and output current point 46 also is down a current potential near common port 45 as the current potential of node 11 in working order.The winding 23 of coupling transformer is structurally symmetrical with winding 22, so, output current I
3Just with feedback current I
2Just with input current I
1Keep good linear relationship.
When input signal and output signal are voltage signal, as shown in Figure 4, an amplifier 50 is set at input, it is with input voltage U
5Zoom into output voltage U
6, and the output 53 by connecting amplifier 50 and the resistance 54 between the electric current comparison point 11 provide input current I to input circuit
1Output is provided with an amplifier 60, and it is with the output current I of output circuit
3Be transformed into voltage U
7, in lead-out terminal 61,62 outputs.Terminal 81 and 82 are the direct voltage U as power supply
8, providing alternating voltage to rectifier 54 and 63 respectively by oscillator 80 and three-winding transformer 70, rectifier 54 inputs provide power supply to amplifier 50,13, and rectifier 63 provides power supply to output amplifier 60.Owing to have high dielectric strength between transformer 20,70 each winding, therefore reach input, output and power end three ends and isolate.
Claims (2)
1. isolated amplifier has one to have three-winding coupling transformer, the structure of its first winding and second winding is symmetry substantially, first winding provides an input that feeds back signal to input circuit by feedback circuit, its second winding is by signal of telecommunication of output circuit output, signal after the output of input circuit will be modulated provides exciting current to the tertiary winding of coupling transformer, it is characterized in that above-mentioned feedback circuit has the serial connection diode pair and first capacitor that join with unlike pole to connect into triangular shape, the mid point of diode pair connects first end of first winding by first resistance, first end of first capacitor is the feedback current output, and second end of first capacitor and second end of first winding join and be attempted by the common port of input circuit; Output circuit also has pair of diodes, a capacitor and a resistance, between them and the method for attachment of they and above-mentioned second winding identical with above-mentioned feedback circuit.
2. isolated amplifier according to claim 1, the formation that it is characterized in that the modulation circuit in the above-mentioned input circuit be by a transistor and between transistor collector and the emitter by opposite conducting direction diode in parallel, indirect one second capacitor of first end of the collector electrode and the above-mentioned tertiary winding, emitter connects the input circuit common port, between second end of this common port and the above-mentioned tertiary winding, be added with ac-excited voltage, base stage as the modulation circuit input is connected on the output of amplifier in the input circuit and accepts the theoretical value of sign input current and the direct voltage of feedback current difference, thereby control flows is crossed the exciting current of the above-mentioned tertiary winding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN94107446A CN1053535C (en) | 1994-07-22 | 1994-07-22 | Isolated amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN94107446A CN1053535C (en) | 1994-07-22 | 1994-07-22 | Isolated amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1115520A CN1115520A (en) | 1996-01-24 |
| CN1053535C true CN1053535C (en) | 2000-06-14 |
Family
ID=5033053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN94107446A Expired - Fee Related CN1053535C (en) | 1994-07-22 | 1994-07-22 | Isolated amplifier |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1053535C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1085906C (en) * | 1998-11-25 | 2002-05-29 | 中国科学院空间科学与应用研究中心 | Logarithmic amplifier circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4968949A (en) * | 1986-07-25 | 1990-11-06 | Meyer Sound Laboratories Incorporated | Ohmically isolating input circuit |
| CN1079345A (en) * | 1992-05-16 | 1993-12-08 | 丘雪明 | Capacity coupled isolated amplifier |
-
1994
- 1994-07-22 CN CN94107446A patent/CN1053535C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4968949A (en) * | 1986-07-25 | 1990-11-06 | Meyer Sound Laboratories Incorporated | Ohmically isolating input circuit |
| CN1079345A (en) * | 1992-05-16 | 1993-12-08 | 丘雪明 | Capacity coupled isolated amplifier |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1115520A (en) | 1996-01-24 |
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| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C19 | Lapse of patent right due to non-payment of the annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |