Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
  • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
  • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
  • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M3/00—Conversion of dc power input into dc power output
  • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
  • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
  • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
  • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
  • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
  • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
  • H02M3/1563—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators without using an external clock
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
  • H02M1/00—Details of apparatus for conversion
  • H02M1/0083—Converters characterised by their input or output configuration
  • H02M1/0087—Converters characterised by their input or output configuration adapted for receiving as input a current source

Definitions

• This invention relates to a converter circuit arrangement for transferring power from an electrical two- conductor current loop to a functional unit.
• the circuit comprises an inductive coupling (transformer) and an AC/DC converter based on the switch mode. More specifically this is here derived from a DC/DC converter of the "Boost Mode" type.
• the current loop conducts an alternating current of a fixed frequency and amplitude for the power transfer, and signals to and from the functional unit are superimposed on the power transfer current in the current loop.
• the current loop constitutes a primary winding and a rectifier device is located at the secondary side for DC supply to the functional unit. More ⁇ over there is included a voltage regulator for controlling an electronic switch for operation in switch mode as men ⁇ tioned, a power coil and at least one capacitor.
• the invention has been primarily developed in connec- tion with a so-called fieldbus for interconnecting several functional units, as for example measuring instruments or control units in process control installations, and the like.
• a current loop bus of the type Current Bus Mode according to IEC 1158-2 can be of interest here.
• This fieldbus or current loop constitutes a two-conductor line, where functional units connected to it communicate, by means of signals, through this line, at the same time as they are supplied with required power in the form of current supply through the same pair of conductors.
• the functional units are connected in series in the bus. Power for current supply from the bus is tapped over the equivalent impedance introduced by the functional unit concerned, into the two-conductor line.
• each of the functional units appears as a series load in the current loop bus, and draws power being proportional to the real part of the series load.
• connection of functional units to the current loop is effected inductively by the bus' forming one or more windings at the primary side of a transformer. With such an inductive connection the secondary side of this transformer can be an integrated part of the functional unit concerned.
• the inductive coupling can also be adapted to provide for signal transfer or communication between the fieldbus and the respective functional units.
• signals are super ⁇ imposed on the power feed, and in practice will normally have a signal strength lying several decades lower than the current amplitude for power transfer. Accordingly it is very important that the power signal has a sinusoidal shape as closely as possible, so that required filtering at the individual functional units will be simplified.
• the load represented by each unit with respect to the current loop bus should be as linear as possible in order to prevent the functional units from introducing harmonic noise into the fieldbus network. Such noise will be disturbing and detrimental for said signal communication. Harmonic noise components from the power supply part or from non-linearities in the individual functional unit, will be spread into the signal band for communication and thereby reduce the signal-to-noise ratio.
• the feed frequency of the AC supply is substantially higher than the common mains frequency, namely 16 kHz in a specific fieldbus embodiment.
• the converter circuits for the functional units comprise an electronic switch, such as a transistor switch, adapted to be controlled at a fixed rate or repetition frequency, which typically can be about 350 kHz.
• the examples of typical frequencies given here form a part of the background for the particular solutions to be described in the following description.
• It is desirable that the voltage drop over each connected functional unit for its current supply, is as low as possible and preferrably an ohmic (resistive) load. Possible imaginary voltage drops occurring, will mean that the feed voltage for the AC supply of the current loop will be unnecessarily high, and the total efficiency of the power or the current supply to the complete fieldbus network will be lower.
• US 4.959.766 relates to an AC/DC converter having a tuned circuit at the input.
• switch mode represents an uninteresting solution in that connection.
• the solution described comprises thyristor control whereby a larger or smaller portion of the alternating voltage half period is utilized.
• the starting point is also different from that of the present invention, since signal transfer is not included, nor does any feeding at a constant current take place.
• US 4.698.790 describes an AC/DC converter which is not based on a supply at a constant current either. However, there is described a solution with switch mode, so that this point in the patent specification has a certain sim ⁇ ilarity to the present invention.
• US 3.906.337 relates to a DC/DC converter with a conventional rectifier bridge, i.e. rather remote from the basis of the present invention, as discussed above.
• An advantageous converter circuit arrangement for connecting a functional unit to an electric current loop as referred to above, is obtained according to this invention by means of novel and specific features as more closely defined in the claims.
• Fig. 1 shows a schematic circuit diagram of a first embodiment of the converter or circuit arrangement according to the invention
• Fig. 2 shows the converter circuit in fig. 1 and besides a particular signal circuit
• Fig. 3 shows another embodiment of the invention and an associated signal circuit
• Fig. 4 shows a first practical exemplary embodiment somewhat more in detail, based upon the basic diagram in fig. 3, but without any signal circuit
• Fig. 1 shows a schematic circuit diagram of a first embodiment of the converter or circuit arrangement according to the invention
• Fig. 2 shows the converter circuit in fig. 1 and besides a particular signal circuit
• Fig. 3 shows another embodiment of the invention and an associated signal circuit
• Fig. 4 shows a first practical exemplary embodiment somewhat more in detail, based upon the basic diagram in fig. 3, but without any signal circuit
• Fig. 5 shows another practical exemplary embodiment being also based on the basic diagram of fig. 3, and without any signal circuit.
• conductor 1 represents the fieldbus or current loop which is here shown with an inductive coupling to a converter circuit arrangement, having output terminals 10A-10B for connection of a functional unit 2 to the fieldbus.
• This circuit thus comprises a transformer 4 with conductor 1 as a primary winding in the form of one or more turns, whereas the secondary winding Lo preferrably has a higher number of turns so as to obtain a desired conversion ratio in transformer 4.
• a capacitor Co In parallel to the secondary winding there is shown a capacitor Co. Then follows a series coupling of a capacitor Cl and a power coil LI.
• a rectifier device is generally denoted LR. The direct voltage provided by it is applied over terminals 10A and 10B for the required power supply to the functional unit 2, for example a 5 volt DC.
• a large capacitor C2 as commonly used.
• a regulator circuit SR which by means of pulse width modulation controls an electronic circuit breaker or switch S at a suitable rate and time relationship. Accordingly, the DC at the output 10A-10B will be maintained at an approximate constant, desired magnitude, for example 5 volt, at varying loads and possible disturbances in the system, including the current loop 1.
• a connection to a small series resistor Rl for sensing the curve shape or wave form of the alternating current delivered by transformer 4.
• the output DC appearing at terminals 10A-10B is applied to the circuit SR.
• the voltage sensed across resistor Rl implies the control of switch S by regulator circuit SR with a pulse width variation being preferrably proportional to the instantaneous value of the current through resistor Rl.
• the pulse width is also controlled by the output DC so as to maintain this constant.
• the electronic switch S is preferrably controlled at a fixed frequency, but with a varying pulse width.
• the voltage regulator circuit SR controls the operation of switch S with a pulse width modulated control signal, it will be possible to provide for a tapping of electric energy which on average is linear and in-phase over the amplitude of the AC feed signal.
• the power coil LI which together with capacitor Co forms a low pass filter, performs an advantageous and necessary smoothing effect with respect to the switching taking place in switch S, so that the complete rectifier circuit with its load appears as a purely linear circuit to the fieldbus being represented by conductor 1 in fig. 1.
• Capacitor Cl which lies in series with coil LI, to ⁇ gether with the latter is adapted to be in resonance at a frequency equal to, or approximately equal to, the feed frequency of the current supply from current loop 1.
• the power coil LI described acts as a filter for high frequency noise.
• the circuit arrangement of fig. l with associated components has the property, being particularly important here, that the circuit represents a linear load with respect to current loop 1. If switch S is closed, the voltage across the secondary side of transformer 4 is low and only determined by the resistance in series resonance circuit Ll-Cl, switch S and series resistor Rl.
• the novel converter circuit being described with reference to fig. 1 makes possible a design with a small number of components and has an optimal performance when connected to a current loop 1, both with respect to AC power efficiency and low noise contribution to the current loop. Of more specific advantages obtained, the following can be mentioned:
• the secondary side or inductance Lo in fig. 1 and fig. 2 together with capacitor Co forms a parallel resonance circuit having a high impedance at the feed frequency, so that a relatively low inductance Lo in coupling transformer 4 does not represent a load on the input of the rectifier/ converter.
• the parallel capacitor Co contributes to the magnetizing of coupling transformer 4 from current loop 1 and provides for the coupler by itself to appear as resis- tive as seen from current loop 1.
• capacitor Co With a separate coupling transformer 4X as in the embodiment of fig. 2, capacitor Co will act as a low impedance (short circuit) with respect to the signaling path over the separate transformer 4X, which obviously is favourable. In this case it is desirable that power coupler 4 will attenuate the communication signals to a minimum degree.
• the resonance capacitor Co as a coupling capacitor for the signaling by having it removed to the signaling circuit as shown in fig. 3.
• power coil LI acts as a high-ohmic insulator, since this does not present a load to the signaling circuit.
• the signaling circuit in fig. 3 can comprise two drive circuits (not shown) connected to the functional unit 2. Such drive circuits must be very low-ohmic in order that parallel resonance circuit Lo-Co shall be efficient.
• a first, more practical and detailed embodiment as shown in fig. 4, is based on the basic diagram of fig. 3, but is simplified in relation to it in so far as the signaling circuit has now not been included.
• resistor RL representing the functional unit 2 which is shown in figs. 1, 2 and 3.
• diodes D6 and D7 there are inserted two diodes D6 and D7.
• the rectifier arrangement con ⁇ sists of the diodes D1-D6.
• the electronic switch S is formed by a transistor Tl.
• the bridge circuit D1-D4 serves to secure that the current flows only in one direction through switch Tl so that the current can be broken in both half periods.
• the switch circuit also makes it possible to read off the sinus curve over resistor Rl in both half periods. This will simplify the implementation of regul- ator circuit SR.
• Diode bridge D1-D4 gives a practical im ⁇ plementation of a switch circuit and a circuit for current reading.
• the off-time of transistor Tl is pulse width modulated at a fixed high frequency (about 350 kHz) so that the off-time is proportional to the instantaneous value of the alternating current measured by means of resistor Rl. Besides, the average width of the off-time is controlled so that a constant output voltage is maintained.
• the booster configuration discussed at the beginning of this description is represented in fig. 4 by power coil LK1, switch transistor Tl, as well as the diodes D5 and D6 for the main current. A corresponding arrangement is also found in fig. 5
• a particularly interesting embodiment is shown in fig. 5. This is the embodiment of the invention that for the time being is preferred in practice. In this embodiment rectification and switch function are combined in transistors Tla-d. Increased efficiency is obtained because of a lower voltage drop in transistors than in diodes.
• the rectifier here consists of the diodes D6 and D5 together with the FET-transistors.
• the switches consist of the transistors Tla and Tic, these being active each in its half period of the feed current.
• the transistors Tla-d are controlled by voltage regulator SR so that Tla conducts together with Tld in one half period of the alternating current (feed current) .
• Tib conducts in the whole half period whereas Tla is pulse width modulated at described above.
• Tic and Tld operate in a corresponding manner in the other half period of the alternating current.
• the converter or circuit arrangement described here involves advantages with respect to efficiency, negligible introduction of noise into the fieldbus, a minimum use of chokes and transformers, as well as small physical dimensions.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Dc-Dc Converters (AREA)
• Supply And Distribution Of Alternating Current (AREA)
• Control Of Electrical Variables (AREA)
• Rectifiers (AREA)
• Ac-Ac Conversion (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=19897877

Family Applications (1)

Country Status (9)

Cited By (2)

Families Citing this family (11)

Citations (4)

Family Cites Families (5)

• 1995
  • 1995-02-01 NO NO950365A patent/NO301917B1/no unknown
• 1996
  • 1996-01-29 AU AU46354/96A patent/AU4635496A/en not_active Abandoned
  • 1996-01-29 US US08/860,643 patent/US5978242A/en not_active Expired - Lifetime
  • 1996-01-29 JP JP8523441A patent/JPH11503898A/ja active Pending
  • 1996-01-29 DE DE69629212T patent/DE69629212T2/de not_active Expired - Fee Related
  • 1996-01-29 BR BR9606843A patent/BR9606843A/pt not_active IP Right Cessation
  • 1996-01-29 AT AT96902014T patent/ATE245868T1/de not_active IP Right Cessation
  • 1996-01-29 EP EP96902014A patent/EP0878050B1/en not_active Expired - Lifetime
  • 1996-01-29 WO PCT/NO1996/000017 patent/WO1996024191A1/en active IP Right Grant

Patent Citations (4)

Also Published As

Similar Documents

Legal Events