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WO1996005648A1 - Appareil d'excitation - Google Patents

Appareil d'excitation Download PDF

Info

Publication number
WO1996005648A1
WO1996005648A1 PCT/GB1995/001915 GB9501915W WO9605648A1 WO 1996005648 A1 WO1996005648 A1 WO 1996005648A1 GB 9501915 W GB9501915 W GB 9501915W WO 9605648 A1 WO9605648 A1 WO 9605648A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
phase difference
current
switching
output
Prior art date
Application number
PCT/GB1995/001915
Other languages
English (en)
Inventor
Andrew Cunningham Davies
Original Assignee
Cheltenham Induction Heating Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cheltenham Induction Heating Limited filed Critical Cheltenham Induction Heating Limited
Priority to AU32276/95A priority Critical patent/AU3227695A/en
Publication of WO1996005648A1 publication Critical patent/WO1996005648A1/fr

Links

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
    • H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
    • H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
    • H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of DC power input into AC 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
    • H02M7/537—Conversion of DC power input into AC 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, e.g. single switched pulse inverters
    • H02M7/538—Conversion of DC power input into AC 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, e.g. single switched pulse inverters in a push-pull configuration
    • H02M7/53803—Conversion of DC power input into AC 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, e.g. single switched pulse inverters in a push-pull configuration with automatic control of output voltage or current

Definitions

  • This invention relates to apparatus for driving a parallel resonance circuit and in particular, but not exclusively, to apparatus for driving an induction heating coil in such a circuit.
  • the present invention consists in apparatus for driving a parallel resonance circuit comprising, an electrical path or inputs thereto, means for connecting or coupling the resonance circuit in the electrical path and switching means for alternating the direction of the current in the electrical path characterised in that the switching means includes means for determining the phase difference between the voltage across the electrical path and current flowing through it and means for controlling the rate of switching to maintain the phase difference to a predetermined value or range.
  • This apparatus is based on the realisation that the shape of the current pulse that passes through the switching means is a function of the phase difference between the voltage and the current and by obtaining a suitable phase difference one can achieve an apparatus which locks on to the appropriate frequency for any parallel resonance circuit, but which can follow changes in the resonant frequency due to the application or removal of loads or changes in the magnetic nature of those loads.
  • a voltage pulse can be achieved which results in the switches being switched on quickly and hence avoids significant heating in the switches.
  • phase-difference determining means determines the phase difference between the start of a voltage cycle and the start of the succeeding current cycle.
  • the phase determining means may include means for squaring the positive or negative parts of the voltage and current cycles to form pulses, and the apparatus may further comprise time-controlled gating means which provide an output in response to any current pulse received in a predetermined period after the receipt of a voltage pulse.
  • the gating means operates on the leading edge of these pulses.
  • the phase-difference determining means may determine the phase difference from the period between the beginning of a voltage pulse and the associated output of the gating means.
  • the switching means may include a voltage controlled oscillator which determines the rate of switching in accordance with the difference between the determined phase difference and the predetermined value. This difference may be indicated by the output of a phase locked loop or a phase comparator.
  • the apparatus may further include start-up means for providing a start-up output to the voltage controlled oscillator to initiate switching.
  • the switching means may provide an initial low voltage in the electrical path until the means for controlling the rate of switching is maintaining a phase difference. The low voltage may be provided for a period determined by delay means.
  • the switching means may include a pair of switches connected in series, a pair of capacitors connected in series with each other and in parallel with the switches, and the electrical path may extend between the respective junctions between the switches and the capacitors.
  • the switches are FETs.
  • Figure 1 is a schematic view of a parallel resonance circuit mounted in its switching circuit
  • Figure 2 is a flow diagram of apparatus for driving the circuit
  • Figures 3a to 3i are graphs indicating respectively the voltage in the resonance circuit; the voltage after squaring; the current in the switching devices; the current after squaring; an alternative current in the switching devices; that alternative current squared; timing windows; current signals passed by those timing windows; and the rising edges of the voltage and current as presented to a phase comparator;
  • Figure 4 is a flow diagram indicating the control logic of the apparatus; and Figure 5 is a schematic more detailed representation of the circuit of Figure 2.
  • a parallel resonance circuit is generally indicated at 10 and includes an induction coil 11, which is typically an induction heating coil, and a capacitance 12.
  • the resonance circuit is located in an electrical path 13 which extends between junctions 14 and 15.
  • Junction 14 lies between two series connected FETs 16, 17, whilst junction 15 lies between two capacitors 18, 19.
  • the FETs 16, 17 and capacitors 18, 19 extend in series between high voltage lines 20, 21. It will be readily understood that when FET 16 is off and FET 17 is on current will pass through the resonance circuit 10 from right, to left, whereas, when FET 16 is on and FET 17, is off current will pass in the other direction. Thus, by alternately switching the FETs 16 and 17 on and off, an alternating current passes along the electrical path 13 and through the resonance circuit 10.
  • the parallel resonance circuit 10 can be driven so that the peak current is at a minimum by controlling the phase difference between the voltage across the circuit 10 and the current flowing in the electrical path 13.
  • FIG. 2 illustrates schematically an apparatus for achieving control of this phase difference.
  • the apparatus generally indicated at 23 has a current input 24 and a voltage input 25. These inputs represent the current measured at 26 in the electrical path 13 and the voltage measured between points 27 and 28 in that path 13.
  • Each of the inputs is connected to a respective squaring amplifier 29, 30.
  • the output of the voltage squaring amplifier 30 passes directly to a phase comparator 31 and at the same time to a gating mechanism 32 which maintains a predetermined time window so that it produces an output if the current pulse is received from the current squaring amplifier 29 within a predetermined period after the pulse from the voltage squaring amplifier 30 has initiated the gating means 32.
  • the output of the gating means 32 is also fed to the phase comparator or phase locked loop 31, which produces, in turn, its own output at 33 which is representative of the period between the receipt of the output from the voltage squaring amplifier 30 and the output of the gating means 32, which period constitutes the phase difference between the current and voltage signals.
  • the output at 33 is fed to a voltage controlled oscillator 34 which is also fed an offset at 35.
  • the offset which is conveniently variable, maybe provided, for example, by a variable resisistence, capacitance or voltage. This offset is representative of the desired phase difference, and the output of the voltage controlled oscillator 34 is a frequency selected to adjust the driving of the circuit so that that phase difference is achieved.
  • This output, at 36 is fed to the FETs 16, 17 via pulse steering control and isolation devices 37, 38.
  • the frequency of operation of the FETs 16, 17 can be rapidly locked on to a desired phase difference at a given operating frequency for the parallel resonance circuit. If the load conditions in the coil 11 suddenly change then there will be a sudden change in the detected phase difference and the output of the voltage controlled oscillator will immediately be corrected so as to re ⁇ establish the desired phase difference. There is thus only a change in the frequency of operation, when conditions demand it. This is in contrast to the earlier apparatus which was always hunting for a better frequency and was therefore often operating off the best frequency.
  • Figures 3a to 3i illustrate the desirability of the voltage squaring and window circuits.
  • the raw voltage and current circuits produce rather imprecise indications of zero cross over.
  • the resultant squared pulses in Figures 3b and 3d give a clear indication of the cross over point and if the current pulses were always as shown in Figure 3c, then it would be possible to detect the phase difference directly from the squared outputs.
  • the current can, under certain circumstances, have additional zero cross overs in the middle of a cycle and thus can produce the output shown in Figure 3f from the current squaring amplifier 29. In this situation it would be difficult to determine which pulses should be ignored.
  • the window gating mechanism 32 therefore opens the window indicated in Figure 3g so that the phase comparator 31 only sees the input shown in Figure 3h and, as the phase comparator 31 only detects the leading edge of the pulses shown in Figure 3b and Figure 3h, it detects the phase difference ⁇ indicated in Figure 3i.
  • FIG. 5 is a schematic but more detailed view of the apparatus outlined in connection with Figure 2 and for convenience sake certain parts of the circuit appear more than once.
  • a voltage supply to the HT lines is indicated at 39 and this in turn feeds to the electrical path 13 in which is disposed primary coil 40.
  • This is linked by its transformer 41 to the resonance circuit 10 and also to a voltage detection coil 42 which provides an output to the voltage squaring amplifier 30.
  • the current in the electrical path 13 is detected by a current sensing device 43 and is fed to the current amplifier 29.
  • the output of the two amplifiers pass, as previously indicated, to the phase comparator 31 and the phase indicating output appears at 33.
  • a voltage divider generally indicated at 44, the upper resistance of which is the offset resistor 35.
  • a switch 45 is provided between the resistors, so that, in the start-up mode, a voltage can be fed from the start-up voltage device 46 to the voltage control oscillator 34. This provides the tune volts previously described.
  • the output from the voltage control oscillator passes through the pulse steering control generally indicated at 37 where it is gated in accordance with the start up condition of the apparatus and in response to any apparatus-condition latches, generally indicated at 47, which may have been tripped.
  • Isolator delays 48 are provided to ensure that there is no overlapping between the switching of the FETs 16, 17.
  • the connection of these two switches with the electrical path 13 are again indicated as is the transformer 41 and the resonance circuit 10.
  • the apparatus can be initiated by the turning on of the "heat on" switch 53.
  • This allows the start up voltage to be supplied to the voltage controlled oscillator, but itself passes through a tune volts delay 49 for the reasons previously described. It also causes an HT voltage control 50 to provide low level voltage on the lines 20, 21 so that there is some current passing through the electrical path 13 when the FETs begin to switch.
  • the output from the tune volts delay 49 is also fed back to the HT control 50 through a delay 51 so that, when the apparatus is phase locked, the HT control 50 enables the power supply 52 to supply full voltage to the lines 20, 21.
  • On switch off the gates fire delay 53 allows sufficient time for the capacitors 18, 19 to discharge.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • General Induction Heating (AREA)

Abstract

Appareil destiné à exciter un circuit (10) de résonance parallèle qui comporte une bobine d'induction (11) et un condensateur (12). Le circuit de résonance est situé dans le trajet électrique (13) qui s'étend entre les jonctions (14, 15). La jonction (14) se trouve entre deux transistors à effet de champ (16, 17) connectés en série, tandis que la jonction (15) se trouve entre deux condensateurs (18, 19). Ledit appareil d'excitation (23) possède une entrée de courant (24) et une entrée de tension (25). Ces dernières sont connectées à des condensateurs (29, 30) de mise au carré. Le mécanisme (32) de déclenchement produit une sortie si une impulsion de courant provenant des amplificateurs (29) est reçue pendant un laps de temps prédéterminé après l'impulsion de tension et cette sortie est acheminée vers une boucle (31) à verrouillage de phase qui produit une sortie (33) représentative de la différence de phase entre les signaux de courant et de tension. Cette sortie est utilisée pour commander la commutation des transistors à effet de champ (16, 17) de manière à obtenir l'excitation désirée de la bobine de chauffe par induction.
PCT/GB1995/001915 1994-08-13 1995-08-14 Appareil d'excitation WO1996005648A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU32276/95A AU3227695A (en) 1994-08-13 1995-08-14 Driving apparatus

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9416411.8 1994-08-13
GB9416411A GB9416411D0 (en) 1994-08-13 1994-08-13 Driving apparatus

Publications (1)

Publication Number Publication Date
WO1996005648A1 true WO1996005648A1 (fr) 1996-02-22

Family

ID=10759854

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1995/001915 WO1996005648A1 (fr) 1994-08-13 1995-08-14 Appareil d'excitation

Country Status (3)

Country Link
AU (1) AU3227695A (fr)
GB (1) GB9416411D0 (fr)
WO (1) WO1996005648A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1168589A1 (fr) * 2000-06-28 2002-01-02 Seb S.A. Procédé et dispositif de contrôle d'un générateur de chauffage à induction
US8116683B2 (en) 2003-02-04 2012-02-14 Access Business Group International Llc Adaptive inductive power supply with communication
US8129864B2 (en) 2008-01-07 2012-03-06 Access Business Group International Llc Inductive power supply with duty cycle control
US8222827B2 (en) 1999-06-21 2012-07-17 Access Business Group International Llc Inductively coupled ballast circuit
US8882378B2 (en) 2010-02-15 2014-11-11 Access Business Group International Llc Heating and dispenser system
US8921746B2 (en) 2008-05-23 2014-12-30 Access Business Group International Llc Inductively-heated applicator system
US9013895B2 (en) 2003-02-04 2015-04-21 Access Business Group International Llc Adaptive inductive power supply

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2085243A (en) * 1980-09-03 1982-04-21 Cheltenham Induction Heating L Apparatus for driving a heating load circuit
US4700285A (en) * 1986-11-18 1987-10-13 National Semiconductor Corporation Combined PWM-FM control method and circuit for the high efficiency control of resonant switch mode inverters/converters
EP0320410A1 (fr) * 1987-12-09 1989-06-14 Merlin Gerin Dispositif de commande d'un interrupteur statique
EP0473957A2 (fr) * 1990-08-31 1992-03-11 Pacesetter AB Système de transfert d'énergie à résonance interrompue
GB2270214A (en) * 1992-08-24 1994-03-02 Usi Lighting Inc Frequency stabilized electronic ballast for discharge lamps

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2085243A (en) * 1980-09-03 1982-04-21 Cheltenham Induction Heating L Apparatus for driving a heating load circuit
US4700285A (en) * 1986-11-18 1987-10-13 National Semiconductor Corporation Combined PWM-FM control method and circuit for the high efficiency control of resonant switch mode inverters/converters
EP0320410A1 (fr) * 1987-12-09 1989-06-14 Merlin Gerin Dispositif de commande d'un interrupteur statique
EP0473957A2 (fr) * 1990-08-31 1992-03-11 Pacesetter AB Système de transfert d'énergie à résonance interrompue
GB2270214A (en) * 1992-08-24 1994-03-02 Usi Lighting Inc Frequency stabilized electronic ballast for discharge lamps

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9397524B2 (en) 1999-06-21 2016-07-19 Access Business Group International Llc Inductively coupled ballast circuit
US10014722B2 (en) 1999-06-21 2018-07-03 Philips Ip Ventures B.V. Inductively coupled ballast circuit
US9590456B2 (en) 1999-06-21 2017-03-07 Access Business Group International Llc Inductively coupled ballast circuit
US8222827B2 (en) 1999-06-21 2012-07-17 Access Business Group International Llc Inductively coupled ballast circuit
US8855558B2 (en) 1999-06-21 2014-10-07 Access Business Group International Llc Adaptive inductive power supply with communication
US9368976B2 (en) 1999-06-21 2016-06-14 Access Business Group International Llc Adaptive inductive power supply with communication
US9299493B2 (en) 1999-06-21 2016-03-29 Access Business Group International Llc Inductively coupled ballast circuit
US9036371B2 (en) 1999-06-21 2015-05-19 Access Business Group International Llc Adaptive inductive power supply
FR2811161A1 (fr) * 2000-06-28 2002-01-04 Seb Sa Procede et dispositif de controle d'un generateur de chauffage a induction
EP1168589A1 (fr) * 2000-06-28 2002-01-02 Seb S.A. Procédé et dispositif de contrôle d'un générateur de chauffage à induction
US9246356B2 (en) 2003-02-04 2016-01-26 Access Business Group International Llc Adaptive inductive power supply
US9190874B2 (en) 2003-02-04 2015-11-17 Access Business Group International Llc Adaptive inductive power supply
US9013895B2 (en) 2003-02-04 2015-04-21 Access Business Group International Llc Adaptive inductive power supply
US9906049B2 (en) 2003-02-04 2018-02-27 Access Business Group International Llc Adaptive inductive power supply
US8116683B2 (en) 2003-02-04 2012-02-14 Access Business Group International Llc Adaptive inductive power supply with communication
US10439437B2 (en) 2003-02-04 2019-10-08 Philips Ip Ventures B.V. Adaptive inductive power supply with communication
US10505385B2 (en) 2003-02-04 2019-12-10 Philips Ip Ventures B.V. Adaptive inductive power supply
US9257851B2 (en) 2008-01-07 2016-02-09 Access Business Group International Llc Inductive power supply with duty cycle control
US8129864B2 (en) 2008-01-07 2012-03-06 Access Business Group International Llc Inductive power supply with duty cycle control
US10170935B2 (en) 2008-01-07 2019-01-01 Philips Ip Ventures B.V. Inductive power supply with duty cycle control
US8921746B2 (en) 2008-05-23 2014-12-30 Access Business Group International Llc Inductively-heated applicator system
US8882378B2 (en) 2010-02-15 2014-11-11 Access Business Group International Llc Heating and dispenser system

Also Published As

Publication number Publication date
GB9416411D0 (en) 1994-10-05
AU3227695A (en) 1996-03-07

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