GB2085243A - Apparatus for driving a heating load circuit - Google Patents
Apparatus for driving a heating load circuit Download PDFInfo
- Publication number
- GB2085243A GB2085243A GB8126514A GB8126514A GB2085243A GB 2085243 A GB2085243 A GB 2085243A GB 8126514 A GB8126514 A GB 8126514A GB 8126514 A GB8126514 A GB 8126514A GB 2085243 A GB2085243 A GB 2085243A
- Authority
- GB
- United Kingdom
- Prior art keywords
- load circuit
- circuit
- power
- heating
- anyone
- Prior art date
- Legal status (The legal status 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 status listed.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/06—Control, e.g. of temperature, of power
-
- 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
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- General Induction Heating (AREA)
Abstract
A work coil 11 is connected between the mid-points 13,14 of a pair of power supply leads 15,16 which are connected to form a parallel circuit 30. Power field effect transistors 18,19 are connected in the lead 15 on respective sides of mid-point 13 so that both halves of the lead 15 are normally open circuit. A control circuit 22 is provided to switch F.E.T.'s 18,19 alternately on and off, causing current flow through the work coil first in the direction of arrows X and then in the direction of arrows Y. The circuit 22 comprises a frequency generator 23, which supplies a pulse train to pulse width modulator 25, which in turn feeds a two phase generator 28. The generator 28 feeds the triggering pulses alternately to F.E &cirf& T.'s 18,19 via respective galvanic isolators 36,37. Automatic power and tuning control is provided. <IMAGE>
Description
SPECIFICATION
Apparatus for driving a heating load circuit
This invention relates to apparatus for driving a heating load circuit and in particular, but not exclusively, a work coil of induction heating apparatus.
In known induction heating apparatus a work coil, which is connected in an oscillatory circuit, is driven by a thermionic valve oscillator, which is connected for positive feed back to the oscillatory circuit. In such apparatus the oscillator is connected across a high voltage A.C. power source and typically the supply voltage is of the order of 10,000 volts. This voltage has to be stepped down to, typically, less than 10% before it is supplied to the work coil.
The high supply voltage may cause safety problems and require the use of expensive components.
Further considerable energy is dissipated in heat in the step-down transformer, causing an expensive waste of energy and necessitating a complicated cooling system. The resultant apparatus is extremely large. In addition if the work coil is to be used at any distance from the apparatus great care has to be taken to ensure that losses are kept to a minimum.
It is an object of the present invention to provide apparatus for driving a heating load circuit, which overcomes some or all of the above mentioned disadvantages.
From one aspect the present invention consists in apparatus for driving a heating load circuit, including switching means for alternately connecting the load circuit across a power source so that an electric current flows through the circuit first in one direction and then in the other.
The apparatus may further include an inductance connectable in series with the load circuit to limit the peak current flowing through the load circuit. The switching means may include a pair of switches or switching devices, which in a preferred embodiment are normally open. In this latter case the switching means may be arranged such that when one switch is closed current flows through the circuit in one direction and when the other switch is closed the current flows in the opposite direction. The switches or switching devices may be pulse operated and may, for example, be power field effect transistors.
Alternatively they may be semi-conductor devices arranged in a cascode configuration, or indeed, any suitable device or configuration.
The switching means may include a control circuit for alternately switching the switches or switching devices. The control means may comprise a pulse generator for generating a pulse train and gating apparatus for feeding successive pulses or groups of pulses in the train to alternate switches. At least two of the pulse generator, the gating apparatus and the pulse width modulator may be formed in a single integrated chip. The switching means may further include means for galvanically isolating a part of the control circuit from the power source. The isolating means may include a transformer or an optical isolator.
The apparatus may further include means for maintaining the power supplied to the load circuit. In the case where the control circuit includes a pulse width modulator, the power maintaining means may include monitoring means for detecting the power in the load circuit and means for varying the width modulation of the pulse width modulator in accordance with the detected power.
The apparatus may further include means for detecting the current supplied to the load circuit and means for adjusting the frequency of operation of the apparatus so that the total current supplied in unit time is a minimum for a given load or so that the peak current occurring in the current flowing to the load circuit in unit time is a minimum for a given load.
The invention further consists in a heating apparatus comprising driving apparatus as hereinbefore defined, an electrical power source, and a load circuit. The load circuit may include an inductive or resistive load.
From another aspect the invention consists in apparatus for heating including a heating load circuit and means for supplying electrical power to the load circuit in the form of pulses.
The quantity of power supplied to the load circuit may be varied by varying the width of the pulses.
Preferably alternate pulses are in a different sense e.g. a positive pulse followed by a negative pulse.
The means for supplying power to the load circuit may include a power source and the load circuit may be connected to the power source such that it sees substantially the full voltage at the power source outputs.
From a further aspect the invention consists in apparatus for heating including load circuit, a power supply connectable to the load circuit such that the load circuit sees substantially the full voltage at the outputs of the power source.
From a still further aspect the invention consists in apparatus for heating including an oscillatory heating load circuit, means for supplying an oscillting current to the load circuit and means for tuning the frequency of oscillation of the current to minimise the current flowing through the load circuit orto minimise the peak current occurring in the current flowing to the load circuit in unit time for a given load.
From another aspect the invention consists in apparatus for heating comprising a heating load circuit, wherein the load circuit is remotely connected to the power supply by means of a lead or leads, none of which constitutes a feedback path.
The apparatus may be for induction heating and the load circuit may contain a work coil. The power supply means may be or may include a D.C. source or a rectified A.C. source.
From a further aspect the invention consists in an apparatus for induction heating, including a heating load circuit and an energy storage device connected in series with the load circuit for limiting the peak current flowing through the load circuit.
The energy storage device is preferably an inductance.
The invention may be performed in a number of ways a specific example of which will now be described, with modifications, with reference to the accompanying drawings, in which:
Figure 1 is a circuit diagram of an induction heating apparatus;
Figure 2 is a diagram showing the voltages at different parts of the circuit at resonance;
Figure 3 is a diagram showing the current flowing through the switches under different circuit conditions; and
Figure 4 is a circuit diagram of a control circuit for the apparatus.
In Figure 1 an oscillatory circuit 10 comprises a work coil 11 connected in parallel with a capacitor 12. Circuit 10 will resonate at a frequency which is dependent on the capacitance of the capacitor 12, the inductance of the work coil 11 and the characteristics of the load which it surrounds.
Circuit 10 is connected between the midpoints 13, 14 of a pair of power supply leads 15,16 which are connected to form a parallel circuit 30, which is itself connected across the outputs 17 of a D.C. power supply (not shown). Typically the power supply will provide 400 volts but in certain applications voltages of 2000 or more volts may be required.
Power field effect transistors (F.E.T.'s) 18, 19 are connected in the lead 15 on respective sides of its midpoint 13so that both halves of the lead 15 are normally open circuit. Capacitors 20, 21 are connected in lead 16On either side of the midpoint 14to split the rail voltage from the D.C. power supply so that the midpoint 14 is preferably at earth potential.
When F.E.T. 18 is switched on, in the manner described below, current flows from the power supply, through the oscillatory circuit 10, to earth as indicated by solid arrows X. Conversely when F.E.T.
19 is switched on current flows through the oscillatory circuit 10 in the direction of the dotted arrows Y.
Thus it will be appreciated that if F.E.T.'s 18, 19 are switched on alternately, the oscillatory circuit 10 will be forced to oscillate, which it will do at its resonant frequency.
F.E.T.'s 18, 19 are switched on and off by a control circuit generally indicated at 22. The circuit 22 comprises a frequency generator 23 having a manual frequency control 24, a pulse width modulator 25, which is connected to the output 26 of the frequency generator 23 and has a manual control 27, and a two phase generator 28. The input 29 of the two phase generator 30 is connected to the output 31 of the pulse width modulator 25 and has outputs 32, 33, which are connected to the gates 34,35 of respective
F.E.T.'s 18,19 via respective galvanic isolators 36, 37.
The control circuit is powered from a low voltage supply, typically 1 5v or a logic supply 38.
In use, the frequency generator 23 generates a pulse train at a frequency pre-set by the manual control 24, this pulse train is width modulated by the pulse width modulator 25 and fed to the two phase generator 28, which gates the pulses in the train to alternate outputs 32,33 such that the pulses on the outputs 32 and 33 are 1800 out of phase.
Each time a pulse is fed to the gate of one of the
F.E.T.'s 18 or 19, that F.E.T. is turned on for the duration of the pulse and power is fed to the oscillatory circuit, in a sense dependent on which of the F.E.T.'s is switched on.
As the pulses are 180 out of phase it will be appreciated that the oscillatory circuit will be forced to oscillate in the manner described above. The power supplied during each cycle will be dependent on the width of each pulse. The broader the pulse the greater the power supplied, provided other circuit parameters are constant. Thus the power supplied to the work coil can be set at the manual control 27.
Whilst the manual control of the frequency and of the pulse width or power enable the apparatus to be set up in the correct operating range it is desirable to provide an automatic control of these variables for easy and efficient operation of the apparatus.
The basis on which the circuit 22 is controlled depends on a number of considerations. From the point of view of efficient power consumption it is desirable to drive the circuit 10 at its resonant frequency. However for reasons which will be explained below, this mode of operation gives rise to extremely high currents through the F.E.T.'s 18 and
19. At relatively low frequencies this is not necessanly a problem, because fairly cheap, robust but slow switching, devices are available. At present the commercially-available faster-acting devices, which .are needed for higher frequency work, have a poor tolerance to high currents and they will often be blown, if the circuit 22 is driven at resonant frequency.
Thus an alternative mode of operation is to drive the circuit 22 in a manner to minimse the peak current flowing through F.E.T.'s 18 and 19. Surprisingly, in practice, the frequency at which this current is a minimum is close to the resonant frequency.
If the circuit 10 is driven at its resonance frequency the total current through the circuit is a minimum.
Thus resonant frequency driving can be achieved by controlling the circuit 22 to minimise this current.
The current supplied to the circuit 10 is measured buy a detector 39 disposed in the power supply circuit. The signal representing the detected current is fed to a tuning device 40, which adjusts the output frequency of the frequency generator 23 until minimum current flow is achieved. As heating takes place the characteristic of the load and work coil can vary and the automatic tuning device may adjust the frequency at any time during heating operation. The importance of this tuning control is that the power transfer from the circuit 10 to the load is most efficient at resonance.
If the load circuit 10 is driven at resonantfrequen- cy, as can be seen from Figure 2, the voltage pulse arrives at point 13 at the instant that the voltage across circuit 10 (VLc) is at or near its zero crossing point. The result is that point 13 is taken to the rail voltage (either V+ or V-) and hence, as is shown in broken line in Figure 3, there is a current surge through whichever of F.E.T.'s 18 or 19 is on. If the frequency at which the F.E.T.'s are driven is adjusted, the point at which switching occurs can be varied relative to the VLC waveform in a sense to
reduce the voltage change across the F.E.T.'s and hence the current peaks.
The circuit 22 can be controlled in this way by an alternative automatic tuning circuit 50 shown in
Figure 4.
In the circuit 50, a current transformer 51 monitors the current flowing into the resonant circuit. Its output is fed to a peak detector 49, which stores the maximum current value detected by transformer 51 in a sample period. This value appears on the inputs of Sample/Hold circuits 52 and 53, which are controlled by a programme sequencer 54, which is driven by a clock 55. The sequencer 54 initially causes
Sample/Hold circuit 52 to store a sample S1 and then causes an increment controller 56 to step one increment either up or down. The change in the increment controller output alters the output of a DigitallAnalogue Converter 57, which is connected to the "tune" input 58 of frequency converter 23, driving the frequency generator 23 away friom its pre-set frequency.
The Sample/Hold circuit 52 is then caused to store a sample S2. A comparator 59 compares S1 and S2 for magnitude and polarity and produces a control signal in a sense to allow the increment controller 56 to pass the next increment in the direction which will tend to make S1 > S2 i.e. the current peak will decrease with each successive step. If the condition S1 = S2 is detected, the increment controller is inhibited and S1 is held, sampling taking place for S2 only. Not until S1 * S2 is a further increment fed into the Digital/Analogue Converter 57.A limiting device 60 is connected to the output of D/A converter 57, whereby if the output reaches the top and bottom limits set by the device the circuit will only continue the incrementing of the D/A converter 57 in a sense to drive the output towards the other limit. On start up of after a S1 = S2 condition the first increment is taken in a random direction.
In either mode of frequency control, or even if no control exists, it is advantageous to insert an inductance 61 (or other energy storing component) between the point 13 and the circuit 10. This inductance will limitthe initial current surge to a manageable level and will modify the subsequent current wave shape by releasing the stored energy, so that a waveform similar to that shown in solid line in
Figure 3 can be achieved. it will be seen that this is a substantially constant current pulse of relatively low maximum amplitude.
As has been stated the power supplied to the circuit 10 is a function of the length of the "on" period of each F.E.T. and hence the pulse width.
Therefore by feeding the current signal detected by the detector 39, which is proportional to the power supplied for constant input voltage, to a comparator 41 the pulse width modulation can be controlled by an error signal generated by the comparator 41, which compares the detected current with a predetermined value set on the manual control 42.
The isolators 36, 37 may be constituted by suitable transformers or alternatively they may be optical isolators. In this latter case the isolator may comprise a light emitter, which is switched on by a pulse received from the two phase generator 28 and an aligned light sensitive detector, which is energised by the emitted light.
Each F.E.T. 18, 19 may be replaced by a number of
F.E.T.'s in parallel, each linked to the respective isolator, in order to allow higher currents to be handled. The capacitors 20, 21 may be replaced by one or more F.E.T.'s in which case the F.E.T. or
F.E.T.'s corresponding to capacitor 21 are switched on and off with F.E.T. 18 and the F.E.T. or F.E.T.'s corresponding to the capacitor 20 are switched on and off with F.E.T. 19. The F.E.T.'s may be replaced by any other suitabie switching device, for example semi-conductor switching devices arranged in the cascode mode may be used.
It is envisaged that the apparatus of this type will operate at frequencies up to at least 1 MHZ, although it may be necessary to supply a range of apparatus to cover the frequency range. For example, a typical embodiment may be designed to operate at 100 KHZ + 75 KHZ.
It will be appreciated that the work coil can be connected to the mid-points 13 and 14 by remote leads. The only factor which need determine the selection of the leads is that the voltage drop along their length should not be unacceptably high. They do not form a part of or constitute a feedback loop and therefore their frequency characteristics are not crucial as in the case with known remote work coil apparatus.
Whilst the described apparatus is for use with a
D.C. power source, apparatus of this type can equally be used in conjunction with a rectified A.C.
power source.
The work coil 11 can be utilised without the capacitor 12. In some applications it may be convenient to connect the primary coil of a transformer between the mid-points 13 and 14 and to connect the work coil or the oscillatory circuit to the secondary of the transformer. For resistive, rather than induction heating, the oscillatory circuit 10 is replaced by a resistive workpiece.
Claims (29)
1. Apparatus for driving a heating load circuit, including switching means for alternately connecting the load circuit across a power source so that an electric current flows through the circuit first in one direction and then in the other.
2. Apparatus as claimed in claim 1 including an inductance connectable in series with the load circuit to limit the peak current flowing through the load circuit.
3. Apparatus as claimed in claim 1 or 2 wherein the switching means includes a pair of switches or switching devices.
4. Apparatus as claimed in claim 3 wherein the switches or switching devices are normally open.
5. Apparatus as claimed in claim 4wherein the switching means is so arranged that when one switch is closed, current flows through the load circuit in one direction and when the other switch is closed, the current flows in the opposite direction.
6. Apparatus as claimed in anyone of claims 3 to 5 wherein the switching means includes a control circuit for alternately switching the switches or switching devices.
7. Apparatus as claimed in claim 6 wherein the switches or switching devices are pulse operated.
8. Apparatus as claimed in claim 7 wherein the control means comprises a pulse generator for generating a pulse train and gating apparatus for feeding successive pulses or groups of pulses in the train to alternate switches.
9. Apparatus as claimed in anyone of claims 6 to 8 wherein the switching means further include isolating means for galvanically isolating at least a part of the control circuit from the power source.
10. Apparatus as claimed in anyone of the preceding claims further including means for maintaining the power supplied to the load circuit at a predetermined level.
11. Apparatus as claimed in anyone of claims 7 to 9 wherein the control circuit includes a pulse width modulator.
12. Apparatus as claimed in claim 10 wherein the control circuit includes a pulse width modulator and wherein the power maintaining means includes monitoring means for detecting the power in the load circuit and means for varying the width modultion of the pulse width modulator in accordance with the detected power.
13. Apparatus as claimed in anyone of claims 3 to 12 wherein the switching devices are power field effect transistors.
14. Apparatus as claimed in anyone of claims 3 to 12 wherein the switches are constituted by semiconductor switching devices arranged in a cascode configuration.
15. Apparatus as claimed in anyone of the preceding claims including means for detecting the current supplied to the load circuit and means for adjusting the frequency of operation of the apparatus so thatthetotal current supplied in unit time is a minimum for a given load or so that the peak current occuring in the current flowing to the load circuit in unit time is a minimum for a given load.
16. Heating apparatus comprising driving apparatus as claimed in anyone of the preceding claims, an electrical power source and a load circuit.
17. Heating apparatus as claimed in claim 16 wherein the load circuit is an inductive or resistive load.
18. Apparatus for heating including a heating load circuit and means for supplying electrical power to the load circuit in the form of pulses.
19. Apparatus as claimed in claim 18 wherein the quantity of power suplied to the load circuit can be varied by varying the width of the pulses.
20. Apparatus as claimed in claim 18 or claim 19 wherein the power supplying means supplies alternate pulses which are in a different sense.
21. Apparatus as claimed in anyone of claims 16 to 18 wherein the power supply means include a power source and wherein the load circuit is connected to the power source such that it sees substantially the full voltage at the power source outputs.
22. Apparatus for heating including a heating load circuit, a power supply connectable to the load circuit such that the load circuit sees substantially the full voltage at the outputs of the power source.
23. Apparatusforheating including an oscillatory heating load circuit, means for supplying an oscillating current to the load circuit, and means for automatically tuning the frequency of oscillation of the current means to minimise the current flowing through the load circuit orto minimise the peak current occuring in the current flowing to the load circuit.
24. Apparatus for heating comprising a heating load circuit, power supply means for supplying power to the load circuit, wherein the load circuit is remotely connected to the power supply by means of a lead or leads, none of which constitutes a feed back path.
25. Apparatus as claimed in anyone of claims 16 to 24 wherein the apparatus is for induction heating and wherein the load circuit contains a work coil.
26. Apparatus as claimed in anyone of the claims 14 to 23 wherein the power supply means are or include a D.C. source or a rectified A.C. source.
27. Apparatus for induction heating, including a load circuit and an energy storage device connected in series with the load circuit for limiting the peak current flowing through the load circuit.
28. Apparatus as claimed in claim 27, wherein the energy storage device is an inductance.
29. Apparatus for driving a heating load circuit, substantially as hereinbefore described with referpence to Figure 1 orthe accompanying drawings or
Figure 1 as modified by Figure 4.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8126514A GB2085243B (en) | 1980-09-03 | 1981-09-01 | Apparatus for driving a heating load circuit |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8028464 | 1980-09-03 | ||
| GB8126514A GB2085243B (en) | 1980-09-03 | 1981-09-01 | Apparatus for driving a heating load circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2085243A true GB2085243A (en) | 1982-04-21 |
| GB2085243B GB2085243B (en) | 1984-11-21 |
Family
ID=26276767
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8126514A Expired GB2085243B (en) | 1980-09-03 | 1981-09-01 | Apparatus for driving a heating load circuit |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2085243B (en) |
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2117192A (en) * | 1982-02-26 | 1983-10-05 | Transtar Limited | Lamp control circuit |
| GB2164473A (en) * | 1984-09-10 | 1986-03-19 | Bard Inc C R | Electrosurgical generator power supply |
| WO1986002211A1 (en) * | 1984-10-05 | 1986-04-10 | Portescap | Current supply circuit of an essentially inductive charge |
| FR2576476A1 (en) * | 1985-01-23 | 1986-07-25 | Balay Sa | INDUCTION HEATING SYSTEM FOR ELECTRIC STOVE PLATES |
| EP0537565A2 (en) * | 1991-10-14 | 1993-04-21 | Siemens Aktiengesellschaft | Induction heating circuit |
| FR2712763A1 (en) * | 1993-11-15 | 1995-05-24 | Moulinex Sa | Corrugated current generator with saturable self. |
| WO1996005648A1 (en) * | 1994-08-13 | 1996-02-22 | Cheltenham Induction Heating Limited | Driving apparatus |
| US5680301A (en) * | 1992-09-02 | 1997-10-21 | Exide Electronics Corporation | Series/parallel resonant converter |
| WO1998018199A1 (en) * | 1996-10-18 | 1998-04-30 | A. Ahlstrom Corporation | Electronic power control having a switched-mode power supply |
| US6255635B1 (en) | 1998-07-10 | 2001-07-03 | Ameritherm, Inc. | System and method for providing RF power to a load |
| EP1134882A2 (en) * | 2000-03-06 | 2001-09-19 | Vacon Oyj | Frequency converter |
| ES2362523A1 (en) * | 2009-08-27 | 2011-07-07 | Bsh Electrodomesticos España S.A. | Control of at least one induction heating load. (Machine-translation by Google Translate, not legally binding) |
| EP3151632A1 (en) * | 2015-10-02 | 2017-04-05 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| EP3151631A1 (en) * | 2015-10-02 | 2017-04-05 | Electrolux Appliances Aktiebolag | Induction heating method and system |
-
1981
- 1981-09-01 GB GB8126514A patent/GB2085243B/en not_active Expired
Cited By (29)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2117192A (en) * | 1982-02-26 | 1983-10-05 | Transtar Limited | Lamp control circuit |
| GB2164473A (en) * | 1984-09-10 | 1986-03-19 | Bard Inc C R | Electrosurgical generator power supply |
| US4727874A (en) * | 1984-09-10 | 1988-03-01 | C. R. Bard, Inc. | Electrosurgical generator with high-frequency pulse width modulated feedback power control |
| WO1986002211A1 (en) * | 1984-10-05 | 1986-04-10 | Portescap | Current supply circuit of an essentially inductive charge |
| FR2576476A1 (en) * | 1985-01-23 | 1986-07-25 | Balay Sa | INDUCTION HEATING SYSTEM FOR ELECTRIC STOVE PLATES |
| EP0537565A2 (en) * | 1991-10-14 | 1993-04-21 | Siemens Aktiengesellschaft | Induction heating circuit |
| EP0537565A3 (en) * | 1991-10-14 | 1993-05-26 | Siemens Aktiengesellschaft | Induction heating circuit |
| US5680301A (en) * | 1992-09-02 | 1997-10-21 | Exide Electronics Corporation | Series/parallel resonant converter |
| WO1995014364A1 (en) * | 1993-11-15 | 1995-05-26 | Moulinex S.A. | Ripple current generator with a saturable self-inducting coil |
| FR2712763A1 (en) * | 1993-11-15 | 1995-05-24 | Moulinex Sa | Corrugated current generator with saturable self. |
| WO1996005648A1 (en) * | 1994-08-13 | 1996-02-22 | Cheltenham Induction Heating Limited | Driving apparatus |
| WO1998018199A1 (en) * | 1996-10-18 | 1998-04-30 | A. Ahlstrom Corporation | Electronic power control having a switched-mode power supply |
| US6521874B2 (en) | 1998-07-10 | 2003-02-18 | Ameritherm, Inc. | RF power supply |
| US6255635B1 (en) | 1998-07-10 | 2001-07-03 | Ameritherm, Inc. | System and method for providing RF power to a load |
| US6271508B1 (en) | 1998-07-10 | 2001-08-07 | Ameritherm, Inc. | System and method for providing RF power to a load |
| US6730894B2 (en) | 1998-07-10 | 2004-05-04 | Ameritherm, Inc. | Resonant frequency tracking system and method for use in a radio frequency (RF) power supply |
| US6316756B1 (en) | 1998-07-10 | 2001-11-13 | Ameritherm, Inc. | Resonant frequency tracking system and method for use in a radio frequency (RF) power supply |
| EP1134882A2 (en) * | 2000-03-06 | 2001-09-19 | Vacon Oyj | Frequency converter |
| EP1134882A3 (en) * | 2000-03-06 | 2001-09-19 | Vacon Oyj | Frequency converter |
| ES2362523A1 (en) * | 2009-08-27 | 2011-07-07 | Bsh Electrodomesticos España S.A. | Control of at least one induction heating load. (Machine-translation by Google Translate, not legally binding) |
| EP3151632A1 (en) * | 2015-10-02 | 2017-04-05 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| EP3151631A1 (en) * | 2015-10-02 | 2017-04-05 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| WO2017055529A1 (en) * | 2015-10-02 | 2017-04-06 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| WO2017055528A1 (en) * | 2015-10-02 | 2017-04-06 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| CN108141923A (en) * | 2015-10-02 | 2018-06-08 | 伊莱克斯家用电器股份公司 | Induction heating method and system |
| CN108141922A (en) * | 2015-10-02 | 2018-06-08 | 伊莱克斯家用电器股份公司 | Induction heating method and system |
| US10448460B2 (en) | 2015-10-02 | 2019-10-15 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| US10448463B2 (en) | 2015-10-02 | 2019-10-15 | Electrolux Appliances Aktiebolag | Induction heating method and system |
| CN108141923B (en) * | 2015-10-02 | 2020-11-06 | 伊莱克斯家用电器股份公司 | Induction heating method and system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2085243B (en) | 1984-11-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20000901 |