[go: up one dir, main page]

WO1998011655A1 - Procede et dispositif d'apport d'energie a un magnetron - Google Patents

Procede et dispositif d'apport d'energie a un magnetron Download PDF

Info

Publication number
WO1998011655A1
WO1998011655A1 PCT/SE1997/001520 SE9701520W WO9811655A1 WO 1998011655 A1 WO1998011655 A1 WO 1998011655A1 SE 9701520 W SE9701520 W SE 9701520W WO 9811655 A1 WO9811655 A1 WO 9811655A1
Authority
WO
WIPO (PCT)
Prior art keywords
voltage
power
actual
current
control
Prior art date
Application number
PCT/SE1997/001520
Other languages
English (en)
Inventor
Kjell LIDSTRÖM
Original Assignee
Ikl Skellefteå Aktiebolag
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 Ikl Skellefteå Aktiebolag filed Critical Ikl Skellefteå Aktiebolag
Priority to AU41439/97A priority Critical patent/AU4143997A/en
Publication of WO1998011655A1 publication Critical patent/WO1998011655A1/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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4225—Arrangements for improving power factor of AC input using a non-isolated boost converter
    • 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
    • H02M5/00—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC
    • H02M5/42—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters
    • H02M5/44—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC
    • H02M5/453—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M5/4585—Conversion of AC power input into AC power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into DC by static converters using discharge tubes or semiconductor devices to convert the intermediate DC into AC using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
    • 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
    • H05B6/64—Heating using microwaves
    • H05B6/66—Circuits
    • H05B6/68—Circuits for monitoring or control
    • H05B6/681—Circuits comprising an inverter, a boost transformer and a magnetron
    • H05B6/682—Circuits comprising an inverter, a boost transformer and a magnetron wherein the switching control is based on measurements of electrical values of the circuit
    • H05B6/685—Circuits comprising an inverter, a boost transformer and a magnetron wherein the switching control is based on measurements of electrical values of the circuit the measurements being made at the low voltage side of the circuit
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Definitions

  • the present invention refers to a method and a device for providing power to a magnetron.
  • Magnetrons are devices which are used in microwave systems for converting electrical energy into microwaves. Magnetrons are for example used as microwave sources in radar equipment, microwave ovens and plasma lamps.
  • the power supply to a magnetron essentially consists of the voltage which is applied between the anode and cathode (filament) of the magnetron, which is generally called the anode voltage. This anode voltage may be of the order of a few kilovolts.
  • the current passing through the magnetron caused by this voltage is generally called the anode current.
  • Fig. 1 there is shown a schematic diagram of a typical relationship between the anode voltage U and the anode current I of the magnetron. Except for extremely small currents, the magnetron shows a relatively low dynamic impedance. This means that very small changes in the anode voltage will give rise to very large changes in the anode current. To compensate for this, the anode current from a power supply unit is preferably provided at a relatively high, preferably inductive, generator impedance.
  • the magnetron characteristics or conditions changes, for example because of the magnetron successively being heated and the temperature hence changing during operation, the emission capacity of the filament slowly decaying after use for a longer period of time, the load changing or because of similar circumstances, the voltage to current relationship of Fig. 1 may be shifted in relation to the initial position.
  • the applied anode voltage and/or the applied anode current may vary considerably.
  • a known technique for controlling the power supply to the magnetron is based upon the principle that the anode current is controlled under the assumption that the anode voltage is, or is being held, constant.
  • a magnetron power supply comprising a first, rectifying step and a second, high voltage generating step, supplies power to a magnetron, wherein the current is detected just before the magnetron and the high voltage generation is controlled based thereupon.
  • An object of the invention is to provide a more stable magnetron performance, especially during difficult load conditions.
  • Another object of the invention is to provide more accurate control of the power supply to a magnetron.
  • Another object of the invention is to provide a power supply which exhibits very small losses.
  • power supply to a magnetron from an alternating voltage source comprises rectifying the alternating voltage from the alternating voltage source into a rectified voltage which is then converted into a rectified high voltage for powering said magnetron. Furthermore, the power provided to said conversion is controlled based upon an actual power.
  • the invention is hence based upon the insight as to the advantage of controlling the power in a step preceding the conversion from rectified low voltage to rectified high voltage. Since the power control is performed prior to this conversion, the conversion itself need not comprise power controlling elements, whereby the conversion efficiency is increased considerably.
  • the inventors have hence come to the insight that the effect of load changes, mains power supply disturban- ces, temperature and the like, upon the operation of the magnetron can be suppressed by continuously making sure that the power which is provided by an initial power supply stage is constant.
  • the detected actual power is compared to a set desired power and the power provided to said conversion is controlled in order to keep the detected actual power essentially equal to the desired power.
  • the inventors have realized the advantage of performing this power control based upon a power detected in association with the initial rectifying and, in any case, prior to the conversion into high voltage.
  • the power is preferably detected prior to said conversion.
  • this conversion may be designed without the incorporation of controlling or feedback elements, i.e. the conversion may be given an optimal design showing small losses. This means that the power losses in the conversion step will be under good control.
  • the current provided by said alternating voltage source is also controlled to be sinusoidal, or to have the same wave form as the alternating voltage, and/or to be essentially in phase with the alternating voltage.
  • the power supply unit wil] show a very high power factor, and it is ensured that no harmonics of the mains frequency will be sent back to the public supply network.
  • the control hence comprises high frequency switching of the rectified signal for providing a controlled, constant and power factor corrected power.
  • an actual current and an actual voltage is detected, together providing said actual power.
  • These actual current and voltage values may then be used for providing power control as well as current control as described above.
  • the measured current and voltage is used in a processing operation, wherein the quotient between the desired power and the mean value of said actual voltage is calculated, resulting in a value of the desired current mean value.
  • This desired mean value is then multiplied with the quotient between said actual voltage and the mean value of the actual voltage, resulting in the voltage phase factor, to provide an instantaneously desired current value.
  • control is performed by comparing the desired current value with the actual current.
  • the current and the vol- tage is then controlled so as to keep the power constant, and to increase or decrease the current based upon this comparison.
  • the invention has the advantage that the conversion step may be designed to exhibit a high efficiency.
  • the conversion from rectified low voltage to rectified high voltage is performed by inverting the rectified voltage at a comparatively high frequency, after which the inverted voltage is transformed into an alternating high voltage which is then rectified into said rectified high voltage for powering the magnetron.
  • incorporated circuits and functions may be tuned in a very preferable manner so that each inverting switching is performed at a zero current crossing and hence essentially without losses.
  • the inversion is advantageously performed by the use of two transistors which are kept active alternately for providing the generally pulse shaped, alternating voltage.
  • the inversion operation performed by the transistors may take place at a 100% duty cycle, thus allowing for said tuning, which in turn allows for the switching at zero current crossings. This is one of the primary factors which contribute to the high efficiency. Further advantages, aspects and features of the present invention will become more clear from the description below.
  • Fig. 1 schematically shows a typical relationship between the anode voltage and the anode current of a magnetron
  • Fig. 2 shows a block diagram of a power supply unit using control according to prior art
  • Fig. 3 schematically shows a block diagram of a power supply unit according to a first embodiment of the present invention
  • Fig. 4 schematically shows a block diagram of a power supply unit according to a second embodiment of the present invention
  • Fig. 5 schematically shows a block diagram of a power supply unit according to a third embodiment of the present invention
  • Fig. 6 schematically shows a block diagram of a power supply unit according to a fourth embodiment of the present invention.
  • Fig. 7 schematically shoes a detailed exemplifying embodiment of a device according to the present invention.
  • Fig. 8a to 8e schematically show signal wave forms present in the circuit of Fig. 7;
  • Fig. 8f schematically shows a simplified diagram of elements included in the circuit of Fig. 7;
  • Fig. 8g and 8h schematically show signal wave forms present in the circuit of Fig. 8f. Detailed description of preferred embodiments
  • I Fig. 1 there is shown a schematic diagram of a typical relationship between the magnetron anode voltage U and anode current I. Except for extremely small currents, the magnetron shows a comparatively low dynamic impedance .
  • FIG. 2 there is schematically shown a block diagram of an example of a prior art magnetron power supply comprising a rectifying stage 1, which rectifies the alternating voltage from an alternating voltage source into a rectified voltage, and a voltage converting step 2, which converts the rectified voltage into a rectified high voltage for providing power to a magnetron 3.
  • the anode current is used as a feedback signal for a control stage incorporated in the voltage converting stage 2.
  • Fig. 3 schematically shows a block diagram of a power supply unit according to a first embodiment of the present invention.
  • a power control step 4, 5 is provided between the rectifying stage 1 and the voltage converting stage 2.
  • the power control step 4, 5 detects the power of the voltage being provided to the converting stage 2, compares this power with a set desired power Pset and continuously controls the power based thereupon. Since there is neither feedback nor control in stage 2, the converting stage may be designed to show an optimized high efficiency, as will be described more fully below.
  • FIG. 4 there is shown a block diagram of a power supply unit according to a second embodiment of the invention.
  • the power supply unit in Fig. 4 comprises a first rectifying stage 11, a power control stage 12, a preferably high frequency switching, inverting stage 14, a step-up transformation stage 15, and a second rectify- ing stage 16, and the magnetron 17 itself.
  • a detecting/- controlling stage 13 detects the power provided to the inverting stage 12 and controls the power control stage 12 so as to keep said power equal to Pset, i.e. so as to keep the power provided to the following stage 14 constant .
  • stages 14, 15, and 16 lack monitoring, cont- rol, feedback, and the like, these stages are tuned so that each inverting switching takes place at a zero current crossing and hence essentially without losses.
  • the inversion in stage 14 is achieved by the use of two transistors operating alternately. Since power control has already been accomplished in stage 12, 13, the transistors of stage 14 may operate at a 100% duty cycle. Inductances and capacitances present in the three circuits are dimensioned so as to get a resonance frequency having a ratio, generally equal to 1/1, to the switching frequency in stage 14, thus allowing for said tuning with switching at zero current crosses.
  • the block diagram of Fig. 4 has been supplemented with a power factor controlling stage 18 which makes sure that the current supplied from the AC mains follows the shape of the voltage wave form, which generally is sinusoidal, and that no harmonics are passed to the public power network.
  • a power factor controlling stage 18 which makes sure that the current supplied from the AC mains follows the shape of the voltage wave form, which generally is sinusoidal, and that no harmonics are passed to the public power network.
  • Fig. 6 there is schematically shown how the power controlling and the power factor controlling functions may be integrated into on single control unit 19.
  • the control unit 19 in Fig. 6 detects the actual power at the output from the rectifying stage, but could 3ust as well detect the power at the input of stage 14, as described in the embodiments above.
  • the power supply unit in Fig. 7 comprises four functional blocks: a power control block SI, a high voltage generating block S2, a filament current control block S3 and a processing/control block S4. Furthermore, the power supply unit is arranged to power a magnetron VI. In Fig. 7, the different blocks are schematically separated by dashed lines.
  • the power control block SI will now be described in detail .
  • the power control block SI of the power supply unit has inputs 10 and 20 connected to an AC voltage power line, which is preferable obtained from the public electricity supply network which provides an alternating voltage of 50 or 60 Hz.
  • the inputs 10 and 20 are connected to a full wave rectifying diode bridge Brl.
  • the positive output of the diode bridge Brl is con- nected to a first output 30 of the block SI via an inductor LI provided in series with a diode Dl .
  • the negative output of the diode bridge Brl is connected to a second output 40 of the block SI via a resistor Rs .
  • a transistor Tl has its collector/drain connected to a point between the inductor LI and the diode Dl and has its emitter/- source connected to the second output 40 of the block SI.
  • a capacitor Cl is connected between the outputs of the block SI. Together, the inductor LI, the diode Dl, the transistor Tl, and the capacitor Cl form a high frequency switched power controller.
  • the on-off-periods of the switch transistor Tl are controlled by a control circuit R which in this example consists of a power factor control circuit, more specifically an integrated circuit of the type UC3854 from Unitrode Integrated Circuits, its incorporation having been modified for obtaining the object of the invention.
  • the control circuit R comprises a squared signal provider X, a multiplier/divider M/D, a comparator C and a control unit PWC1.
  • a control signal Pset (Power Set) from the processing/control block S4 is connected to an input A of the multiplier/divider M/D.
  • the positive output of the diode bridge Brl is connected to an input B of the multiplier/divider M/D and via a low- pass filter LF and the squared signal provider X to an input C of the multiplier/divider M/D.
  • the output of the multiplier/divider M/D is connected to a first input of the comparator C and to the negative output of the diode bridge Brl via a resistance Rl.
  • the second input of the comparator C is connected to the second output of the power control block SI.
  • the output C of the comparator is connected to an input of the control unit PWC1, which output is connected to the gate of the transistor Tl .
  • the power control block SI is arranged to ensure that a constant power, the magnitude of which is determined by the signal Pset from the processing/control block S4, is provided to the following blocks/steps independent of variations in the mains voltage or variations in the load or in the inherent characteristics of the magnetron.
  • the power control block SI also makes sure that the current supply from the mains is sinusoidal and in phase with the voltage.
  • the incoming mains AC voltage is full-wave rectified in a conventional manner in the diode bridge Brl so that a pulsating direct voltage V in is obtained between the positive and negative output of the diode bridge Brl.
  • Examples of voltage curves for the network voltage AC and the rectified voltage V ⁇ n from the diode bridge Brl are shown in Fig 8a and 8b, respectively.
  • the current from the rectifying bridge Brl is then switched at a high frequency by the power controller LI, Dl, Tl, Cl so that it flows alternately through the transistor Tl and the diode Dl .
  • the high frequency switched power controller "chops" the low frequency (typically 50 or 60 Hz) pulsating current at a frequency of the order 100 kHz or higher.
  • the high frequency switched power controller provides a rectified output voltage which is always larger than the input voltage.
  • the following block must therefore be designed so that it may always be fed with a voltage which is higher than the highest peak value of the mains voltage.
  • the operation of the high frequency switched voltage converter will now be described in detail.
  • the curves of Fig, 8c, 8d, and 8e show the currents passing through the energy storing inductor LI at three different pulse width relationships but at the same total time period.
  • the active time is 20% of the total period
  • the active time is 50% of the total period
  • the active time is 80% of the total period.
  • the derivative of the increasing cur- rent in the curves in Fig 8c to 8e is proportional to the voltage from the rectifying bridge Brl
  • the derivative of the decreasing current is proportional to the difference between the voltage over the capacitor Cl and the voltage from the diode bridge Brl.
  • the interaction between the transistor Tl and the control circuit R thus makes sure that the power provided by the power control block SI is constant and independent of load or variations in the mains voltage, considering the desired power level set by the signal Pset which is provided by the processing/control block.
  • the selected power level which is represented by the control voltage Pset (Power Set) is provided to the input A of the multiplier/divider M/D.
  • the voltage V ⁇ n from the rectifying bridge Brl is filtered in the low- pass filter LF, squared in the squared signal provider X and then fed to the input C of the multiplier/divider M/D.
  • the voltage V ⁇ n is also provided directly to the input B of the multiplier/divider M/D.
  • the voltage from the rectifying bridge Brl is used as a sample or standard for the wave form of the current.
  • the network power line voltage is sinusoidal.
  • the mean value V m of the rectified network voltage V ⁇ n is obtained from the low-pass filter LF and is fed via the squared signal provider X to the input C.
  • the relationship between the voltage V ⁇ n and its mean value V m is given by:
  • the function of the multiplier/divider M/D may schematically be described as follows.
  • a value is obtained corresponding to the mean value that the current has to show in order to give rise to the desired power Pset.
  • V ⁇ n By dividing the instantaneous value of the voltage V ⁇ n with the value V m of the actual voltage V in , a factor representing the shape of the voltage wave form is obtained.
  • the desired mean value of the current (which ensures the correct power) multiplied by the wave form of the voltage (which ensures that the current is in phase with the voltage) thus gives a measure of the instantaneous value that the current must have in order to accommodate both these requirements.
  • the output K from the multiplier/divider M/D is hence generated as the currently desired current. This is compared by the comparator C with the actual current Is.
  • the output signal K is represented as a voltage K x Rl, which is provided to one input of the comparator and which has its point of reference at the negative output of the rectifying bridge Brl.
  • the current Is is represented using the resistance Rs as a voltage Is x Rs, which is provided to the other input of the comparator and which also has its point of reference at the negative output of the rectifying bridge Brl.
  • the current Is follows the wave form of Vj .n . Furthermore, the power is obtained as the mean value of the voltage V ⁇ n multiplied by the current Is:
  • the power control block SI thus accomplishes several preferable functions: the power from the diode bridge Brl is controlled to be constant, based upon Pset, and the current Is supplied from the mains is controlled to have the same wave form as the voltage and to be in phase therewith.
  • the power supply unit thereby shows a high power factor.
  • the power control block SI further comprises a mains filter (not shown) which makes sure that no high frequency components in the current is submitted to the mains . )
  • the high voltage converting block ⁇ 2 comprises a high frequency switched half bridge having capacitive voltage division, a transformer and a voltage doubling rectifier. Furthermore, a pulse width control circuit is provided for reasons to be describe below. More specifically, the block S2 comprises a pulse width control circuit PWC2 having an input, which receives a control signal from the processing/control block S4, and two outputs which are connected to the primary coil of a first transformer Trl.
  • Two transistors T2 and T3 are connected in series between the outputs 30 and 40 of the block SI. Furthermore, two capacitors C2 and C3 are connected in series parallel to the transistors T2 and T3.
  • a first secondary coil of the transformer Trl is in one of its ends connected to the gate of the transistor T2 and is in its other end connected to the emitter/source of the transistor T2.
  • a second secondary coil of the transformer T2 is in one of its ends connected to the gate of the transistor T3 and is m its other end connected to the emitter/source of the transistor T3.
  • the high voltage converting block S2 comprises a second transformer Tr2 which has a primary coil having one end connected to a point between the two transistors Tl and T2 and having the other end connected to a point between the two capacitors C2 and C3 via an inductor L2.
  • the high voltage converting block S2 further has a first 50 and a second 60 output connected to the cathode and anode, respectively, of the magnetron VI.
  • the anode is connected to ground.
  • An inductor L3 and two capacitors C4 and C5 are connected in series between the outputs 50 and 60.
  • two diodes D2 and D3 are connected in series parallel to the capacitors C4 and C5.
  • the secondary coil of the transformer Tr2 is in one of its ends connected to a point between the two diodes D2 and D3 and is in its other end connected to a point between the two capacitors C4 and C5.
  • the block S2 further comprises a third transformer Tr3, having a primary coil in series with the primary coil of the transformer Tr2 and having a secondary coil which in one of its ends is connected to the second output 40 of the block SI and in the other end is connected via a diode D4 to an input of the pulse width control circuit PWC2.
  • the output signal from the pulse width control circuit PWC2 controls, via the transformer Trl, the transistors T2 and T3 to pass current alternately.
  • the switching frequency of the transistors is for example 50 kHz. The choice of frequency depends among other on the power level at which the magnetron is designed to operate.
  • the high voltage converting block S2 is operated at a 100% duty cycle, i.e. the ratio between the time that any one of the transistors T2, T3 of the high voltage generating block S2 is passing current and the total period is equal to 1.
  • the signal from the pulse width control circuit PWC2 makes each of the transistors T2, T3 pass current 50% of the period time.
  • the transistors T2 and T3 are activated a shorter time, i.e. at a duty cycle lower than 1. This kind of converter start up is commonly known as slow-start.
  • this initial control of the duty cycle of the high voltage converter block S2 is provided but for achieving a soft start of the converter and i s hence not intended to be used for continuos control of the power provided to the magnetron during normal operation, as is however the case in prior art.
  • the converter S2 operates at a full duty-cycle
  • half the output voltage from the power control block SI which is kept at a relatively constant level, is applied with alternating polarity to the primary coil of the transformer Tr2, which up-transforms the voltage considerably, generally to a few kilovolts.
  • the leakage inductance of the transformer Tr2, in this case supplemented with a separate inductor L2 is approximately tuned to the switching frequency using the capacitors C2 and C3.
  • the transistors T2 and T3 will thus be turned on and off when the current passing through them is very close to zero. The switching losses will hence be very small.
  • the function of the quasi-resonant converter may partly be illustrated by the schematic block diagram in Fig. 8f.
  • the power to the resonance circuit which schematically comprises an inductor L and a capacitor C, is switched between plus and minus half the supplied voltage E using the transistors Ta and Tb, and the load, which is schematically illustrated by the resistor r, is connected to ground.
  • Fig. 8g and 9h examples of the wave forms of the voltage V and current I in Fig. 8f are shown, said figures clearly illustrating that the current at the time of the switching is very close to zero.
  • the serially connec- ted diodes D2 and D3 and capacitors C4 and C5 form a voltage doubling rectifier which puts a lower demand on the ration of the transformer Tr2 and contributes to the protection against overload at flash-overs in the magnetron, which will be discussed below.
  • the diodes and the capacitors are connected at one arm each of a bridge, wherein the secondary coil of the transformer Tr2 is con- nected at that diagonal which is formed by the connection points for the two diodes and the two capacitors, respectively, and wherein the output voltage is collected at the other diagonal, where the diodes are connected to the capacitors.
  • the inductor L3 ensures that the magnetron is being provided with an inductive generator impedance, which is generally required for stable operation.
  • the current is monitored using the transformer Tr3 which provides a signal via the diode D4 to the pulse width control circuit PWC2 to temporarily deactivate the switching of the transistors T2 and T3 when a flash-over or a transient occurs in the magnetron.
  • the energy which at that moment may be supplied to the magnetron during a half period is limited to the energy which is stored in the capacitor C3 or C4 since the previous half period, depending on during which half period of the switching that the break is made.
  • the filament current control block S3 in Fig. 7 comprises a control unit FCC.
  • the control unit FCC conventionally provides a filament current supplied through the cathode of the magnetron VI.
  • the control unit FCC recei- ves its power supply from the power control block SI, but may be designed to use a control function of its own, independent of the operation of the power controller, for controlling the magnitude of the filament current.
  • the operation of the control, unit FCC may also be based upon different parameters received from the processing/control block S4.
  • the processing/control block S4 comprises a microprocessor CPU which provides control and monitoring of the operation of the power supply unit. The microprocessor sends control signals to, and monitors (not shown) , the other function blocks.
  • the microprocessor is connected to the input A of the multiplier/- divider M/D in the control circuit R for providing the signal Pset thereto, said signal indicating the desired power level.
  • the microprocessor CPU is also connected to the pulse width control circuit PWC2 in the high voltage converting block S2 for controlling the above mentioned slow-start function which is used during slow start or build up of a steady oscillation in the high voltage converting step S2.
  • the microprocessor CPU is connected to the control unit FCC of the filament current control block S3 for providing control signals thereto.
  • the microprocessor may communicate externally using an analogue control voltage (for controlling the power of the magnetron) or using a digital, preferably serial, interface (not shown) which may be bi-directional.
  • the interface may use the power supply as a communication link.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of High-Frequency Heating Circuits (AREA)

Abstract

La présente invention concerne un procédé et un dispositif servant à alimenter en énergie un magnétron, à partir d'une source de tension alternative. Selon l'invention, on exécute cette alimentation en rectifiant la tension alternative, afin d'obtenir une tension rectifiée que l'on convertit ensuite en courant continu destiné à alimenter le magnétron, l'énergie apportée en vue de ladite conversion étant régulée sur la base d'un effet réel détecté dans les moyens d'alimentation.
PCT/SE1997/001520 1996-09-10 1997-09-09 Procede et dispositif d'apport d'energie a un magnetron WO1998011655A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU41439/97A AU4143997A (en) 1996-09-10 1997-09-09 Method and device for providing power to a magnetron

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9603292A SE510033C2 (sv) 1996-09-10 1996-09-10 Förfarande och anordning för kraftmatning av en magnetron från en växelspänningskälla.
SE9603292-5 1996-09-10

Publications (1)

Publication Number Publication Date
WO1998011655A1 true WO1998011655A1 (fr) 1998-03-19

Family

ID=20403835

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1997/001520 WO1998011655A1 (fr) 1996-09-10 1997-09-09 Procede et dispositif d'apport d'energie a un magnetron

Country Status (3)

Country Link
AU (1) AU4143997A (fr)
SE (1) SE510033C2 (fr)
WO (1) WO1998011655A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7026590B2 (en) * 2003-09-25 2006-04-11 Lg Electronics Inc. Low-output microwave, lighting system and flicker removing method using the same
WO2020112921A1 (fr) * 2018-11-30 2020-06-04 Eagle Harbor Technologies, Inc. Générateur rf à impédance de sortie variable

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076996A (en) * 1975-09-12 1978-02-28 Matsushita Electric Industrial Co., Ltd. Power supplier for magnetron
US4318165A (en) * 1980-04-21 1982-03-02 General Electric Company Resonant-flyback power supply with filament winding for magnetron and the like loads
US5208432A (en) * 1990-04-14 1993-05-04 Goldstar Co., Ltd. Magnetron driving power supply circuit
US5451750A (en) * 1992-02-14 1995-09-19 Samsung Electronics Co., Ltd. Microwave output stabilizing apparatus of a microwave oven and a method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076996A (en) * 1975-09-12 1978-02-28 Matsushita Electric Industrial Co., Ltd. Power supplier for magnetron
US4318165A (en) * 1980-04-21 1982-03-02 General Electric Company Resonant-flyback power supply with filament winding for magnetron and the like loads
US5208432A (en) * 1990-04-14 1993-05-04 Goldstar Co., Ltd. Magnetron driving power supply circuit
US5451750A (en) * 1992-02-14 1995-09-19 Samsung Electronics Co., Ltd. Microwave output stabilizing apparatus of a microwave oven and a method thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 13, Nr. 429, E-823; & JP,A,01 159 994 (NEW JAPAN RADIO CO LTD), 22 June 1989. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7026590B2 (en) * 2003-09-25 2006-04-11 Lg Electronics Inc. Low-output microwave, lighting system and flicker removing method using the same
WO2020112921A1 (fr) * 2018-11-30 2020-06-04 Eagle Harbor Technologies, Inc. Générateur rf à impédance de sortie variable
CN113348613A (zh) * 2018-11-30 2021-09-03 鹰港科技有限公司 可变输出阻抗rf发生器
US12198898B2 (en) 2018-11-30 2025-01-14 Eagle Harbor Technologies, Inc. Variable output impedance RF generator

Also Published As

Publication number Publication date
AU4143997A (en) 1998-04-02
SE9603292L (sv) 1998-03-11
SE9603292D0 (sv) 1996-09-10
SE510033C2 (sv) 1999-04-12

Similar Documents

Publication Publication Date Title
JP2559033Y2 (ja) ガス放電ランプ用安定器
KR0160311B1 (ko) 고역률 전원장치
US6396717B2 (en) Switching power supply having an improved power factor by voltage feedback
US11056979B2 (en) Power conversion apparatus
KR100221705B1 (ko) 교류.직류 변환용 전원 회로
JP3749579B2 (ja) 複結合一次巻線を備える入力高調波電流補正ａｃ−ｄｃ変換器
US7283379B2 (en) Current controlled switch mode power supply
KR101223220B1 (ko) 직렬 공진형 컨버터 회로
JPH08336235A (ja) 力率補正回路
US20130051096A1 (en) AC/DC Converter with a PFC and a DC/DC Converter
US7158389B2 (en) Switching power supply circuit
US12438470B2 (en) Peak efficiency tracking in an LLC converter of a multi-stage power conversion system
JP3484904B2 (ja) 力率改善回路
KR100420964B1 (ko) 역률보상 단일단 컨버터
WO1998011655A1 (fr) Procede et dispositif d'apport d'energie a un magnetron
JP4359973B2 (ja) 電源回路
JP2002078323A (ja) 電源装置
JP4275223B2 (ja) 電源装置
JP4306234B2 (ja) スイッチング電源装置
JPH07147780A (ja) 電源装置
Komeda et al. Load voltage regulation method for an isolated AC-DC converter with power decoupling operation
JPH04368471A (ja) 電源装置
JP3560717B2 (ja) プッシュプル型スイッチング電源装置
JPH0678537A (ja) スイッチング電源装置
JP3494036B2 (ja) 電源装置

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AL AM AT AT AU AZ BA BB BG BR BY CA CH CN CU CZ CZ DE DE DK DK EE EE ES FI FI GB GE GH HU IL IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MD MG MK MN MW MX NO NZ PL PT RO RU SD SE SG SI SK SK SL TJ TM TR TT UA UG US UZ VN YU ZW AM AZ BY KG KZ MD RU TJ TM

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): GH KE LS MW SD SZ UG ZW AT BE CH DE DK ES FI FR

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
WWE Wipo information: entry into national phase

Ref document number: 09254239

Country of ref document: US

NENP Non-entry into the national phase

Ref country code: JP

Ref document number: 1998513567

Format of ref document f/p: F

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA