Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F38/00—Adaptations of transformers or inductances for specific applications or functions
  • H01F38/14—Inductive couplings

Definitions

• the invention relates to a unitary magnetic coupler.
• the invention also relates to a switching power supply and information transmission equipment using such a coupler.
• the field of the invention is that of power supplies having the function of delivering DC voltages from an AC or DC network.
• “Flyback” or “Forward” type power supplies are low-power switching power supplies, frequently used in particular because of their simplicity of control.
• the “Flyback” type power supply is particularly interesting because of its reduced size since it requires only one magnetic element to carry out the energy conversion.
• a “flyback” type supply diagrammatically shown in FIG. 1a) is a switching power supply with energy accumulation.
• a primary circuit P comprising connected in series, a voltage source V * n> a switch M, for example a transistor OS and an inductance Lp consisting of a winding of Np turns, and a secondary circuit S comprising connected in series , an inductance Ls consisting of a winding of Ns turns, magnetically coupled to Lp, a capacitance C out connected to a load represented here by a resistor R cha rge and a rectifier D, for example a diode.
• phase ⁇ corresponding to the direction of the winding, is identified by a circle.
• the first and second windings have the same phase.
• the transformer T designates the coupling circuit comprising the primary inductance Lp and the secondary inductance Ls.
• the current flowing through the primary circuit is i p , and the voltages across the primary circuit and the switch are V * n and VM respectively; the current flowing through the secondary circuit is i s , and the voltages across the secondary circuit and the diode are V or t and V D respectively .
• inductive storage In this “Flyback” type supply, the two windings are not traversed simultaneously by the current.
• the operation of this power supply, called inductive storage is based on the realization of energy transfer cycles comprising a phase of magnetic energy accumulation in the inductive element of the primary circuit (in this case Lp), followed a phase of restitution of this energy to a secondary source through the secondary circuit.
• FIGS. 1d) and 1e the waveforms in continuous mode, according to which the current i s does not cancel at the end of operation of the secondary diode D. It is furthermore assumed for simplicity that the current i p instantly goes from its maximum value to 0.
• V * _ P across the inductance Lp varies as a function of time between a maximum value equal to V * n and a minimum value equal to -V or t * Np / N s .
• the current i p shown in FIG. 1e) varies as a function of time between a maximum value i Ma ⁇ and 0; the current i s varies as a function of time between 0 and a maximum value equal to i-viax * Ns / N p .
• a “Forward” type supply diagrammatically represented in FIG. 2a) is a switching power supply with direct energy transfer.
• a primary circuit P comprising connected in series, a voltage source V * n , a switch M, for example a MOS transistor and an inductance Lp consisting of a winding of Np turns, and, mounted in parallel with the inductance Lp and the switch M, a demagnetization circuit of the transformer which can be a diode D of m in series with an inductance L e m , magnetically coupled to Lp, consisting of a winding of N em turns.
• the diode Dd ⁇ m and the inductance Ldem can be replaced by other components.
• the secondary circuit S comprises in series an inductance
• Ls consisting of a winding of Ns turns, magnetically coupled to Lp, a capacitance C or t connected to a load represented here by a resistance
• Rc h arge an inductor L, a first rectifier D1, for example a diode, and mounted in parallel with the inductor Ls and the rectifier D1, a second rectifier D2 which can also be a diode.
• phase ⁇ of each of the windings of Lp, L of m and Ls is identified by a circle.
• the windings of Lp and Ls have the same phase, contrary to the phase of the winding of L of m-
• the transformer T designates the coupling circuit comprising the primary inductance Lp, the secondary inductance Ls and the inductance L d em-
• the current flowing through the primary circuit is i p and the voltages across the primary circuit and the switch are Vj n and V respectively; the current passing through the secondary circuit is i S) and the voltages at the terminals of the secondary circuit and of the diode D1 are respectively V out and V D * ⁇ .
• the two windings operate simultaneously; there is a direct transfer of energy between the inductances Lp and Ls.
• the diode D1 When the switch M is open (FIG. 2c), the diode D1 is blocked, and the diodes D2 and D of m turn on.
• the freewheeling diode D2 ensures the continuity of the current i s in the inductance L and the diode Ddem ensures the continuity of the magnetic energy stored in the inductance Lp during the previous phase (ie during T on ) by transferring this stored energy to V ⁇ for a time equal to T on * Ndem / N p : D em demagnetizes the transformer T.
• FIGS. 2e) and 2f) represent the waveforms. For simplicity, it is assumed that the current i p instantly passes from its maximum value to O.
• V * _ p across the inductance Lp varies as a function of time between V * n and -V in * Np / Ndem-
• the current i p shown in FIG. 2f) varies as a function of time between a maximum value i Maxp and 0; the current i s varies as a function of time between a maximum value equal to ii iax s and a minimum value i m ⁇ n .
• a primary circuit P comprises at least one switch M mounted in series with a voltage source V * n and a first inductance Lp
• a secondary circuit comprises at least one rectifier D mounted in series with a second inductance Ls and a capacitance C out connected to a load
• the primary and secondary circuits are coupled by means of a coupling circuit comprising at least the primary inductances Lp and secondary Ls magnetically coupled together.
• FIG. 15 conventionally modeled by a leakage inductance Lf in series with the inductance Lp, as shown in FIG. 3a) for a “Flyback” type supply and FIG. 3b) for a “Forward” type supply.
• V v storageM V v in + ⁇ - -v ⁇ * N v ou, t + '- ⁇ * N v in * - - ⁇ -
• the leakage inductance creates an overvoltage term at the terminals of the switch, of the form
• the energy stored in the leakage inductor is generally dissipated during the switching phases.
• the switching losses at the opening of the switch are proportional to T fa ⁇ .
• Dissipative R, C, D circuits that is to say comprising Resistance, Capacitance and Diode
• R, C, D circuits are very effective in limiting the overvoltage but they dissipate all the energy contained in the leakage inductance, which reduces the overall efficiency.
• the capacitance C limits the overvoltage term at the opening of the switch M; resistor R discharges the voltage across C and thus dissipates the energy contained in the leakage inductance.
• Switching assistance circuits are often used to reduce overvoltages at the terminals of switch M.
• FIG. 5 An example of a “Flyback” type supply using a poorly dissipative CALC circuit is shown in FIG. 5.
• the capacity limits the overvoltages at the terminals of the switch M.
• an oscillating assembly with L and C makes it possible to reverse the voltage at the terminals of C.
• the losses in the diodes D1, D2 and in the inductance L limit the share of energy recovered by the assembly; in addition it is also necessary to dampen the oscillations of the assembly L, C, which also degrades the yield.
• An important object of the invention is therefore to propose a circuit making it possible to reduce in “Flyback” or “Forward” type power supplies, the overvoltages at the terminals of the switch M, the switching losses and the energy losses contained in the leakage inductance.
• the invention provides a unitary magnetic coupler comprising a first inductance Lp consisting of a first phase winding ⁇ and having a number N of turns between the two ends of the first winding and, magnetically coupled to the first inductance Lp , a second inductance Ls consisting of a second winding of the same phase ⁇ and having the same number N of turns between the two ends of the second winding, characterized in that the ends of the first and second windings are connected together by a connection comprising a capacity of the same value.
• Such a coupler whose inductance of the primary circuit has the same number of turns as the inductance of the secondary circuit makes it possible to have the same voltage across the terminals of the primary and secondary windings of the same phase and therefore to use a capacitive link to counter the effect of the leakage inductance, without increasing the switching losses.
• the invention also relates to a switching power supply comprising a primary circuit P coupled to a secondary circuit S by means of a magnetic coupling circuit, characterized in that the magnetic coupling circuit is a unitary magnetic coupler as described. "_-" - "
• the power supply can be of the “FLYBACK” or “FORWARD” type.
• the primary P and secondary S circuits are capable of generating across the terminals of each capacity of the unit magnetic coupler, a voltage not varying as a function of the switching frequency.
• the invention also relates to information transmission equipment comprising at least one information transmission-reception device connected to a two-wire data bus, characterized in that it comprises a unitary coupler as described, capable of connect the information transmission / reception device to the two-wire data bus.
• FIGS. 1a) to 1e) already described show diagrammatically, respectively a “Flyback” type supply, its operating phases when the switch is closed and then open, and its waveforms
• FIGS. 2a) to 2f) already described schematically respectively represent a “Forward” type supply, its operating phases when the switch is closed and then open, then when the diode D of is also open, and its waveforms
• FIG. 4 already described schematically represents a supply of “Flyback” type comprising a dissipative R, C, D circuit
• FIG. 5 already described diagrammatically represents a “Flyback” type supply comprising a poorly dissipative CALC circuit
• FIG. 6 diagrammatically represents a unit coupler according to the invention
• the figures 7a) and 7b) schematically represent, respectively, a “Flyback” type supply and a “Forward” type supply, comprising a unitary coupler according to the invention
• FIG. 8 schematically represents an example of an information transmission system comprising a unitary coupler according to the invention.
• the circuit used to reduce in a supply, the overvoltages at the terminals of the switch M, the losses by switching and the losses of energy contained in the leakage inductance, is a unitary coupler.
• a unitary coupler is a transformer in which the winding of the inductance Lp of the primary circuit has the same number of turns and the same phase as the winding of the inductance Ls of the secondary circuit.
• a first link (link 1) comprising a first capacitor C1 connects the ends of the windings of the inductors Lp and Ls; and a second link (link 2) comprising a second capacitor C2, of the same value as the first capacitor C1, connects the other ends of the inductors Lp and Ls.
• This coupler allows coupling at relatively low frequencies (a few tens of kHz), up to a few tens of MHz while reducing losses.
• the capacitor chosen for the capacitive connections preferably has very low parasitic inductance and series resistance.
• This coupler is advantageously used in “Flyback” or “Forward” type power supplies as shown in FIGS. 7a) and 7b).
• the capacitive links cancel the overvoltage at the terminals of the switch M when opening M. It is therefore not necessary to add circuits R, C, D or CALC, nor to oversize the switch M in tension.
• the energy stored in the leakage inductance is directly transferred into the capacitive links which transfer this energy into the secondary circuit.
• the configurations minimizing the common mode voltages between the primary and secondary circuits are chosen so that the capacitive links can be used, that is to say the configurations allowing the voltage across the capacitors C1 (respectively C2) to vary not depending on the switching frequency.
• FIG. 7a A “Flyback” type supply not generating high common mode voltages at the switching frequency, and using a unit coupler according to the invention is shown in FIG. 7a).
• It comprises a primary circuit P comprising connected in series, a voltage source V * n ,, an inductance Lp and a switch M, and a secondary circuit S comprising connected in series, a capacitance C or t, connected to a load shown here by a resistor Rcharge, a rectifier D and an inductance Ls.
• the coupling circuit between the primary P and secondary S circuits comprises a unitary coupler according to the invention; the inductances Lp and Ls are therefore identical and connected by capacitive links of the same value.
• a “Forward” type power supply that does not generate high common mode voltages at the switching frequency, and using a unit coupler according to the invention is shown in FIG. 7b).
• It comprises a primary circuit P comprising connected in series, a voltage source V * n ,, an inductance Lp and a switch M, and mounted in parallel with the inductance Lp and the switch M, means for demagnetize the transformer, such as for example those of FIG. 2a); it also includes a secondary circuit S comprising connected in series, a capacitance C out , connected to a load represented here by a resistance Rcharge, an inductance L, a first rectifier D1 and an inductance Ls, and mounted in parallel with the rectifier D1 and inductance Ls, a rectifier D2.
• the coupling circuit between the primary P and secondary S circuits comprises a unitary coupler according to the invention; the inductances Lp and Ls are therefore identical and connected by capacitive links of the same value.
• the unitary coupler according to the invention is applicable in particular to power supplies in which a M transistor is used as switch M, and / or as rectifiers D1, D2 and or Ddem, uncontrolled rectifiers such as diodes, or even controlled rectifiers such only Mos.
• the unitary coupler according to the invention is in particular applicable to converters with inductive storage as described in patents Nos. 2,729,471, 2,729,516 and 2,773,013.
• the power supplies described allow better efficiency and lower overvoltages at the terminals of the switch without significantly increasing the complexity of the circuits, as in the case of circuits including R, C, D or CALC circuits.
• the use of capacities enables high frequency coupling, which can exceed 100 MHz.
• the unitary coupler according to the invention can then be used to transmit information at high frequency: capacitive coupling allows rapid transmission of information which is relayed by magnetic coupling at frequencies of a few tens of KHz to several tens of MHz.
• FIG. 8 An example of an information transmission system is shown in FIG. 8. It comprises two pieces of equipment E1 and E2 linked together by a two-wire data bus B. Each of the pieces of equipment E1 and E2 comprises a device for transmitting and receiving information T / R connected to the data bus B by means of a unit coupler according to the invention and resistors R.
• the coupler according to the invention can be applied to any device using a magnetic transformer.

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• 2002
  • 2002-05-03 FR FR0205580A patent/FR2839381B1/fr not_active Expired - Fee Related
• 2003
  • 2003-04-25 WO PCT/FR2003/001319 patent/WO2003094181A1/fr active Application Filing
  • 2003-04-25 EP EP03740672A patent/EP1504459A1/de not_active Withdrawn
  • 2003-04-25 US US10/513,019 patent/US6975097B2/en not_active Expired - Fee Related

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