EP0711099A2 - Microwave oven with induction heating function - Google Patents
Microwave oven with induction heating function Download PDFInfo
- Publication number
- EP0711099A2 EP0711099A2 EP95402456A EP95402456A EP0711099A2 EP 0711099 A2 EP0711099 A2 EP 0711099A2 EP 95402456 A EP95402456 A EP 95402456A EP 95402456 A EP95402456 A EP 95402456A EP 0711099 A2 EP0711099 A2 EP 0711099A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- heating circuit
- circuit
- induction heating
- microwave
- mode selection
- 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.)
- Withdrawn
Links
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
- H05B6/062—Control, e.g. of temperature, of power for cooking plates or the like
-
- 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
- H05B6/687—Circuits for monitoring or control for cooking
Definitions
- the present invention relates to a microwave oven with an induction heating function, and in particular to an improved microwave oven with an induction heating function capable of selectively using a microwave oven or an induction heat function without interruptions from a microwave oven heating circuit and an induction heating circuit when cooking food.
- a conventional microwave oven with an induction heating function includes a power supply circuit 100 for converting an input alternating current AC into a ripple direct current using a bridge diode BD, for smoothing the thusly converted direct voltage using a coil L1 and capacitances Cl and C2, and for supplying the thusly smoothed direct current to a microwave oven with an induction heating function, a microwave heating circuit 101 for generating a microwave oven after increasing the voltage supplied thereto up to a predetermined level, an induction heating circuit 102 having an induction coil IC, a capacitance C5, and a damper diode D3, a key input circuit 103 having a cooking mode selection key and various kinds of function keys, a microwave oven 104 for generating a pulse width modulation signal CS2 so as to drive the cooking mode selection control signal CS1, the microwave heating circuit 101, and the induction heating circuit 102 in accordance with a predetermined mode selected by the key input circuit 103 and for controlling a heating circuit selection operation of a microwave
- the microwave heating circuit 101 includes a high voltage transformer 11 for increasing the voltage level outputted from the power supply circuit 100 up to a predetermined level, a high voltage generating circuit 21 having high voltage diodes D1 and D2 and a high voltage capacitance C4 for converting the high voltage increased by the high transformer 11 into a current high voltage, and a magnetron 31 for generating a microwave in accordance with the thusly converted direct high voltage.
- the cooking mode selection circuit 105 includes a relay drive circuit 15 for generating a relay drive signal and for driving a relay 25 in accordance with a cooking mode selection drive circuit CS1 outputted from the microcomputer 104, and a relay 25 for switching the microwave heating circuit 101 or the relay switch RS connected to the induction heating circuit 102 in accordance with a relay driving signal outputted from the relay drive circuit 15.
- the alternating current AC is rectified to a current voltage by the bridge diode BD and is smoothed by the coil L1 and the capacitances C1 and C2.
- the relay switch RS is connected to a terminal b2 of the microwave heating circuit 101 or a terminal b3 of the induction heating circuit 102.
- the microcomputer 104 recognizes a key input signal applied thereto, and generates a cooking mode selection control signal CS1 and a pulse width modulation signal CS2.
- the relay drive circuit 15 of the cooking mode selection circuit 105 receives the cooking mode selection control signal CS 1 outputted from the microcomputer 104 and outputs a relay drive signal in accordance with a cooking mode selection control signal CS1 applied thereto.
- the relay 25 switches the relay switch RS connected to the terminal b3 of the invertor 102 to the terminal b2 of the microwave heating circuit 101.
- the switching device Q1 of the heating drive circuit 106 is turned on or turned off in accordance with a pulse width modulatien signal CS2 outputted from the microcomputer 104.
- the switching device Q1 when the switching device Q1 is turn on, the direct current voltage outputted from the power supply circuit 100 is supplied to the capacitance C3 and the high voltage transformer 11.
- the capacitance C3 and a primary coil of the high voltage transformer 11 become a resonant state by a direct current outputted from the power supply circuit 100 in accordance with a turn-on/turn-off operation of the switching device Q1 of the heating drive circuit 106 and are applied to both ends of the capacitance C3, and the resonant voltage is inducted to a secondary coil of the high voltage transformer 11.
- the resonant voltage inducted to the secondary coil of the high voltage transformer 11 is converted into a direct current through the high voltage diodes D1 and D2 and the high voltage capacitance C4 of the high voltage generating circuit 21 and drives the magnetron 31.
- the magnetron 31 generates a magnetron so as to cook food.
- the microcomputer 104 recognizes the induction heating mode key and outputs a cooking mode selection control signal CS1 and a pulse width modulation signal CS2 in accordance with the recognition.
- the relay drive circuit 15 of the cooking mode selection circuit 105 receives the cooking mode selection control signal CS1 outputted from the microcomputer 104 and outputs a relay drive signal so as to drive the relay 25.
- the relay switch RS is connected to the terminal b3 of the induction heating circuit 102.
- the direct current voltage outputted from the power supply circuit 100 is applied to the induction coil IC and the resonant capacitance C5 of the induction heating circuit 102 because the power supply circuit 100, the induction heating circuit 102, and the heating drive circuit 106 are closed.
- the switching device Q1 of the heating drive circuit 106 is turned on and turned off in order in accordance with a pulse width modulation signal SC2 outputted from the microcomputer 104, and the resonant voltage outputted from the capacitance C5 and the induction coil IC and applied to both ends of the capacitance C5, and a relatively big resonant voltage level is applied to the induction coil IC.
- a metal pan is heated by the induction heating of the induction coil IC, and the food in the cavity of the microwave oven is heated.
- the conventional microwave oven with an induction heating function has disadvantages in that when a user selects a predetermined cooking mode between a microwave cooking mode and an induction cooking mode, since the food in the cavity of the microwave oven is heated by a cooking mode selected by a relay switch for a predetermined time, it is impossible to achieve a desired cooking state because the cooking operation is performed in state that a predetermined unstable component is contained in the electric power because the power is supplied through the relay switch.
- a pulse width modulation signal of a high level is applied to the gate terminal of the transistor, the transistor is turned on, and the collector terminal, as shown in Fig. 2B, may receive a short voltage therefrom, so that the transistor can be damaged by the short voltage.
- a microwave oven with an induction heating function which includes a microcomputer for generating a cooking mode selection control signal and a pulse width modulation signal in accordance with a cooking mode selection key input and for controlling a selection operation of the microwave heating circuit and the induction heating circuit; a relay drive circuit for generating a first drive signal and a second drive signal in accordance with a cooking mode selection control signal outputted from the microcomputer and for outputting a certain drive signal; and first and second relays, selectively switched by the first drive signal or the second drive signal outputted from the relay drive circuit, for supplying an electric voltage of a power supply circuit to the microwave heating circuit and the induction heating circuit.
- a microwave oven with an induction heating function which includes a microcomputer for generating a cooking mode selection control signal and a pulse width modulation signal in accordance with a cooking mode selection key input and for controlling a selection operation of the microwave heating circuit and the induction heating circuit; a cooking mode selection circuit for selecting one of the microwave heating circuit and the induction heating circuit corresponding to a cooking mode selection control signal outputted from the microcomputer and for supplying a voltage of a power supple circuit to a heating drive circuit; and a switching device protection circuit for cutting off a pulse width modulation signal of the microcomputer, which determines an ON/OFF interval of the switching device of the heating drive circuit when a resonant voltage exceeds a predetermined level by detecting the resonant voltage outputted from one of the microwave heating circuit and the induction heating circuit and for protecting the switching device.
- Fig. 1 is a block diagram of a conventional microwave oven with an induction heating function.
- Fig. 2A is a wave form of a collector-emitter voltage of a switching device of a heat driving circuit of Fig. 1.
- Fig. 2B is a wave form of a collector current of a switching device of a heat driving circuit of Fig. 1.
- Fig. 2C is a wave form of a gate voltage of a switching device of a heat driving circuit of Fig. 1.
- Fig. 3 is a block diagram of a microwave oven with an induction heating function of a first embodiment according to the present invention.
- Fig. 4 is a block diagram of a microwave oven with an induction heating function of a second embodiment according to the present invention.
- Fig. 5A is a wave form of a collector-emitter voltage of a transistor of a heat driving circuit of Fig. 4.
- Fig. 5B is a wave form of a collector current of a transistor of a heat driving circuit of Fig. 4.
- Fig. 5C is a wave form of a gate voltage of a transistor of a heat driving circuit of Fig. 4.
- Fig. 5D is a wave form of a base-emitter voltage of a transistor of a switching device protector of Fig. 4.
- a microwave oven with an induction heating function of a first embodiment according to the present invention includes a power supply circuit 1 for converting an externally supplied alternating current voltage AC into a direct voltage using a bridge diode BD, for smoothing the thusly converted direct current voltage using a coil L11, capacitances C11 and C12, and for supplying the thusly smoothed voltage to a microwave oven with an induction heating function, a microwave heating circuit 2 for generating a microwave and for executing a microwave heating operation after increasing an electric power supplied thereto through relay switches RS1 and RS2, an induction heating circuit 3, having an induction coil IDC, a resonant capacitance C15, and a damper diode D13, for generating a high frequency magnetic field in accordance with a power supplied from the power supply circuit 1 and for heating a metal plate MTP, a microcomputer 5 for generating a pulse width modulation signal PWM so as to enable a cooking mode selection control signal and so as to drive the microwave
- the microwave heating circuit 2 includes a high voltage transformer 21 for increasing the power supplied from the power supply circuit 1 through the relay switches RS1 and RS2 up to a predetermined level, a high voltage generating circuit 22, having high voltage diodes D11 and D12 and a high voltage capacitance C14, for converting the thusly increased high voltage into a direct current voltage, and a magnetron 23 for generating a microwave in accordance with a supply of the high direct current voltage converted by the high voltage generating circuit 22.
- the cooking mode selection circuit 6 includes a relay drive circuit 61 for outputting drive signals DSI and DS2 so as to drive first and second relays 62 and 63 in accordance with a cooking mode selection control signal CSC outputted from the microcomputer 5, and first and second relays 62 and 63 for selectively switching the relay switches RSI and RS2 in accordance with drive signals DS1 and DS2 outputted from the relay drive circuit 61.
- the alternating current voltage AC is supplied to the power supply circuit 1, when an alternating current voltage AC is supplied to the power supply circuit 1,.
- the alternating current voltage AC is rectified to a direct current voltage by a bridge diode BD and smoothed by the coil L11 and the capacitances C11 and C12.
- the relay switch RS1 is connected to the terminal b13 of the invertor RS 1, and the relay switch RS2 is connected to the terminal C12 of the microwave heating circuit 2, and there is thusly a disconnection between the microwave heating circuit 2 and the induction heating circuit 3.
- the microcomputer 5 recognizes a key input signal in accordance with a microwave cooking key selected by the user and generates a cooking mode selection control signal CSS and a pulse width modulation signal PWM.
- the relay drive circuit 61 of the cooking mode selection circuit 6 receives a cooking mode selection control signal CSS outputted from the microcomputer 5 and outputs a relay drive signal DS1 in accordance with the thusly received cooking mode selection control signal CSS.
- the relay switch RS1 is connected to the terminal b12 of the microwave heating circuit 2 by the first relay 62 in accordance with a relay drive signal DS1 outputted from the relay drive circuit 61.
- the switching device Q11 of the heating drive circuit 6 is turned on and turned off in order in accordance with a pulse width modulation signal PWA outputted from the microcomputer 5.
- a certain resonant voltage is generated at the capacitance C13 and a primary coil of the high voltage transformer 21 by a direct current voltage supplied thereto from the power supply circuit 1 and is applied to both ends of the capacitance C13 and is inducted to a secondary coil of the high voltage transformer 21.
- the resonant voltage inducted to the secondary coil of the high voltage transformer 21 is converted into a direct current voltage through the high voltage diodes D11 and D12 and the high capacitance C14 of the high voltage generating circuit 22 and drives the magnetron 23.
- the magnetron 23 generates a high frequency wave so as to heat food.
- a cooking completion control signal is outputted from the microcomputer 5, and the delay drive circuit 61 of the cooking mode selection circuit 6 receives the cooking completion control signal outputted from the microcomputer 5, stops the drive of the first relay 62, and sets the relay switch RS1 to the initial stage. That is, the relay drive circuit 61 is connected to the terminal b13 of the induction heating circuit 3.
- the direct current outputted from the power supply circuit 1 is not supplied to the microwave heating circuit 2 and the induction heating circuit 3.
- the microcomputer 5 recognizes a key input signal corresponding to the induction heating mode and outputs a selection control signal CSS and a pulse width modulation signal PWM in accordance with the recognition.
- the relay drive circuit 61 of the cooking mode selection circuit 6 receives a cooking mode selection control signal CSS outputted from the microcomputer 5 and outputs a relay drive signal DS2 so as to driving the second relay 63.
- the second relay 63 switches the relay switch RS2 to the terminal c13 by a driving signal DS2 outputted from the relay drive circuit 61.
- the switching device Q11 of the heating drive circuit 7 is turned on and turned off in order in accordance with a pulse width modulation signal PWM outputted from the microcomputer 5.
- the direct voltage outputted from the power supply circuit 1 is supplied to the induction coil IDC and the resonant capacitance C15 because the power supply circuit 1, the induction heating circuit 3 and the heating drive circuit 7 are disconnected therefrom.
- the microcomputer 5 outputs a cooking completion control signal, and the relay drive circuit 61 stops the drive of the second relay 63, and the relay switch RS2 is connected to the terminal c12.
- the microwave oven with an induction heating function of a second embodiment according to the present invention has the same construction as the first embodiment except a switching device protection circuit 8 for protecting the switching device Q11 by cutting off the pulse width modulation signal PWM of the microcomputer 5, which is subject to determining an ON/OFF interval of the switching device Q11 of the heating drive circuit 7 when a resonant level is higher than a predetermined level by detecting the resonant voltage level outputted from the induction heating circuit 6.
- the switching protection circuit 8 includes a zenor diode ZD1 for passing through the resonant voltage outputted from the microwave heating circuit 2 or the induction heating circuit 6 when it exceeds a predetermined level, and a transistor Q12 for receiving the voltage outputted from the zenor diode ZD1 through the capacitances Rl and R2 and for cutting off the pulse width modulation signal PWM outputted from the microcomputer and applied to the heating drive circuit 7.
- the relay switch RS1 is connected to the terminal b12 by the first relay 62 and the second relay 63 for selecting the microwave heating circuit 2.
- the power outputted from the power supply circuit 1 is applied to the capacitance C13 and a primary coil of the high voltage transformer 21 and applied to both ends of the capacitance C13 in accordance with a switching operation of the switching device Q11 of the heating drive circuit 7.
- the transistor Q12 is turned on in accordance with a high voltage applied to the base terminal thereof and by-passes the pulse width modulation signal PWM outputted from the microcomputer 5 to the ground terminal.
- a low level voltage as shown in Fig. 5C, is applied to the gate terminal of the switching device Q11 of the heating drive circuit 7, and a certain level of voltage lower than that of the zenor voltage VZ is not applied to the collector terminal of the switching device Q11, the switching device Q11 is safely protected.
- the relay switch RS2 of the first and second relays 62 and 63 are turned on, and since the relay switch RSI maintains a turned-on state, a certain resonant voltage is applied to both ends of the capacitance C15 of the induction heating terminal 3.
- the microwave oven with an induction heating function is capable of selectively using a microwave oven and an induction heat function without any interruptions from a microwave oven heating circuit and an induction heating circuit when cooking food by providing first and second relays which is selectively used for a certain mode.
- the microwave heating circuit and the induction heating circuit can be safely used irrespective of the internal pressures of the high voltage resonant and relays due to use of the electric power of 220V.
- the present invention is directed to expanding the life span of the product by preventing damages of the switching device due to a relatively high resonant voltage by stopping the drive of the switching device for a predetermined time when the resonant voltage exceeds a predetermined level by detecting the resonant voltage which occurs due to the noise components contained in the input voltage and electric power between turn on/off intervals of the switching device of the heating drive circuit.
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Control Of High-Frequency Heating Circuits (AREA)
Abstract
An improved microwave oven with an induction heating function capable of
selectively using a microwave oven or an induction heat function without any interruptions
from a microwave oven heating circuit and an induction heating circuit when cooking food,
which includes a microcomputer for generating a cooking mode selection control signal and
a pulse width modulation signal in accordance with a cooking mode selection key input and
for controlling a selection operation of the microwave heating circuit and the induction
heating circuit; a relay drive circuit for generating a first drive signal and a second drive
signal in accordance with a cooking mode selection control signal outputted from the
microcomputer and for outputting a certain drive signal; and first and second relays,
selectively switched by the first drive signal or the second drive signal outputted from the
relay drive circuit, for supplying an electric voltage of a power supply circuit to the
microwave heating circuit and the induction heating circuit.
Description
The present invention relates to a microwave oven with an induction heating
function, and in particular to an improved microwave oven with an induction heating
function capable of selectively using a microwave oven or an induction heat function
without interruptions from a microwave oven heating circuit and an induction heating
circuit when cooking food.
Referring to Fig. 1, a conventional microwave oven with an induction heating
function includes a power supply circuit 100 for converting an input alternating current
AC into a ripple direct current using a bridge diode BD, for smoothing the thusly
converted direct voltage using a coil L1 and capacitances Cl and C2, and for supplying
the thusly smoothed direct current to a microwave oven with an induction heating
function, a microwave heating circuit 101 for generating a microwave oven after
increasing the voltage supplied thereto up to a predetermined level, an induction heating
circuit 102 having an induction coil IC, a capacitance C5, and a damper diode D3, a key
input circuit 103 having a cooking mode selection key and various kinds of function keys,
a microwave oven 104 for generating a pulse width modulation signal CS2 so as to drive
the cooking mode selection control signal CS1, the microwave heating circuit 101, and
the induction heating circuit 102 in accordance with a predetermined mode selected by
the key input circuit 103 and for controlling a heating circuit selection operation of a
microwave oven with an induction heating function, a cooking mode selection circuit 105
for selecting the microwave heating circuit 101 or the induction heating circuit 102 in
accordance with a switching operation of a relay switch RS connected between the
microwave heating circuit 101 and the induction heating circuit 102, and a heat driving
circuit 107, having a switching device Q1 and switched by the pulse width modulation
signal CS2 outputted from the microcomputer, for driving the microwave heating circuit
101 and the induction circuit 102 in accordance with a selection of the cooking mode
selection circuit 105.
The microwave heating circuit 101 includes a high voltage transformer 11 for
increasing the voltage level outputted from the power supply circuit 100 up to a
predetermined level, a high voltage generating circuit 21 having high voltage diodes D1
and D2 and a high voltage capacitance C4 for converting the high voltage increased by
the high transformer 11 into a current high voltage, and a magnetron 31 for generating
a microwave in accordance with the thusly converted direct high voltage.
The cooking mode selection circuit 105 includes a relay drive circuit 15 for
generating a relay drive signal and for driving a relay 25 in accordance with a cooking
mode selection drive circuit CS1 outputted from the microcomputer 104, and a relay 25
for switching the microwave heating circuit 101 or the relay switch RS connected to the
induction heating circuit 102 in accordance with a relay driving signal outputted from the
relay drive circuit 15.
The operation of the conventional microwave oven with an induction heating
function will now be explained with reference to Fig. 2.
To begin with, when an alternating power AC is supplied to the power supply
circuit 100, the alternating current AC is rectified to a current voltage by the bridge diode
BD and is smoothed by the coil L1 and the capacitances C1 and C2.
At this time, the relay switch RS is connected to a terminal b2 of the microwave
heating circuit 101 or a terminal b3 of the induction heating circuit 102. In state that the
relay switch RS is connected to the terminal b3 of the induction heating circuit 102, when
a user selects a microwave cooking mode key of the key input circuit 103, the
microcomputer 104 recognizes a key input signal applied thereto, and generates a cooking
mode selection control signal CS1 and a pulse width modulation signal CS2.
Thereafter, the relay drive circuit 15 of the cooking mode selection circuit 105
receives the cooking mode selection control signal CS 1 outputted from the microcomputer
104 and outputs a relay drive signal in accordance with a cooking mode selection control
signal CS1 applied thereto.
Therefore, the relay 25 switches the relay switch RS connected to the terminal b3
of the invertor 102 to the terminal b2 of the microwave heating circuit 101.
Meanwhile, the switching device Q1 of the heating drive circuit 106 is turned on
or turned off in accordance with a pulse width modulatien signal CS2 outputted from the
microcomputer 104.
Therefore, when the switching device Q1 is turn on, the direct current voltage
outputted from the power supply circuit 100 is supplied to the capacitance C3 and the
high voltage transformer 11. The capacitance C3 and a primary coil of the high voltage
transformer 11 become a resonant state by a direct current outputted from the power
supply circuit 100 in accordance with a turn-on/turn-off operation of the switching device
Q1 of the heating drive circuit 106 and are applied to both ends of the capacitance C3,
and the resonant voltage is inducted to a secondary coil of the high voltage transformer
11.
Thereafter, the resonant voltage inducted to the secondary coil of the high voltage
transformer 11 is converted into a direct current through the high voltage diodes D1 and
D2 and the high voltage capacitance C4 of the high voltage generating circuit 21 and
drives the magnetron 31.
Therefore, the magnetron 31 generates a magnetron so as to cook food.
Meanwhile, when the relay switch Rs at an initial state is connected to the
terminal b2 of the microwave heating circuit 101, and when a user inputs an induction
heating mode key of the key input circuit 103 so as to cook food using the induction
heating circuit 102, the microcomputer 104 recognizes the induction heating mode key
and outputs a cooking mode selection control signal CS1 and a pulse width modulation
signal CS2 in accordance with the recognition.
Thereafter, the relay drive circuit 15 of the cooking mode selection circuit 105
receives the cooking mode selection control signal CS1 outputted from the microcomputer
104 and outputs a relay drive signal so as to drive the relay 25. The relay switch RS is
connected to the terminal b3 of the induction heating circuit 102.
Therefore, the direct current voltage outputted from the power supply circuit 100
is applied to the induction coil IC and the resonant capacitance C5 of the induction
heating circuit 102 because the power supply circuit 100, the induction heating circuit
102, and the heating drive circuit 106 are closed.
At this time, the switching device Q1 of the heating drive circuit 106 is turned on
and turned off in order in accordance with a pulse width modulation signal SC2 outputted
from the microcomputer 104, and the resonant voltage outputted from the capacitance C5
and the induction coil IC and applied to both ends of the capacitance C5, and a relatively
big resonant voltage level is applied to the induction coil IC.
Therefore, a metal pan is heated by the induction heating of the induction coil IC,
and the food in the cavity of the microwave oven is heated.
However, the conventional microwave oven with an induction heating function has
disadvantages in that when a user selects a predetermined cooking mode between a
microwave cooking mode and an induction cooking mode, since the food in the cavity
of the microwave oven is heated by a cooking mode selected by a relay switch for a
predetermined time, it is impossible to achieve a desired cooking state because the
cooking operation is performed in state that a predetermined unstable component is
contained in the electric power because the power is supplied through the relay switch.
In addition, when an electric power of 220V is supplied thereto, since the resonant
voltage level is higher than that of the relay switch during a cooking operation, it is
nearly impossible to execute a stable microwave heating operation.
Moreover, in state that a relatively high resonant voltage, as shown in Fig. 2A, is
applied between the collector terminal and the emitter terminal of the switching device,
a pulse width modulation signal of a high level, as shown in Fig. 2C, is applied to the
gate terminal of the transistor, the transistor is turned on, and the collector terminal, as
shown in Fig. 2B, may receive a short voltage therefrom, so that the transistor can be
damaged by the short voltage.
Accordingly, it is an object of the present invention to provide a microwave oven
with an induction heating function, which overcome the problems encountered in a
conventional microwave oven.
It is another object of the present invention to provide an improved microwave
oven with an induction heating function capable of selectively using a microwave oven
or an induction heat function without any interruptions from a microwave oven heating
circuit and an induction heating circuit when cooking food.
To achieve the above objects, in accordance with a first embodiment, there is
provided a microwave oven with an induction heating function, which includes a
microcomputer for generating a cooking mode selection control signal and a pulse width
modulation signal in accordance with a cooking mode selection key input and for
controlling a selection operation of the microwave heating circuit and the induction
heating circuit; a relay drive circuit for generating a first drive signal and a second drive
signal in accordance with a cooking mode selection control signal outputted from the
microcomputer and for outputting a certain drive signal; and first and second relays,
selectively switched by the first drive signal or the second drive signal outputted from the
relay drive circuit, for supplying an electric voltage of a power supply circuit to the
microwave heating circuit and the induction heating circuit.
To achieve the above objects, in accordance with a second embodiment, there is
provided a microwave oven with an induction heating function, which includes a
microcomputer for generating a cooking mode selection control signal and a pulse width
modulation signal in accordance with a cooking mode selection key input and for
controlling a selection operation of the microwave heating circuit and the induction
heating circuit; a cooking mode selection circuit for selecting one of the microwave
heating circuit and the induction heating circuit corresponding to a cooking mode
selection control signal outputted from the microcomputer and for supplying a voltage of
a power supple circuit to a heating drive circuit; and a switching device protection circuit
for cutting off a pulse width modulation signal of the microcomputer, which determines
an ON/OFF interval of the switching device of the heating drive circuit when a resonant
voltage exceeds a predetermined level by detecting the resonant voltage outputted from
one of the microwave heating circuit and the induction heating circuit and for protecting
the switching device.
Fig. 1 is a block diagram of a conventional microwave oven with an induction
heating function.
Fig. 2A is a wave form of a collector-emitter voltage of a switching device of a
heat driving circuit of Fig. 1.
Fig. 2B is a wave form of a collector current of a switching device of a heat
driving circuit of Fig. 1.
Fig. 2C is a wave form of a gate voltage of a switching device of a heat driving
circuit of Fig. 1.
Fig. 3 is a block diagram of a microwave oven with an induction heating function
of a first embodiment according to the present invention.
Fig. 4 is a block diagram of a microwave oven with an induction heating function
of a second embodiment according to the present invention.
Fig. 5A is a wave form of a collector-emitter voltage of a transistor of a heat
driving circuit of Fig. 4.
Fig. 5B is a wave form of a collector current of a transistor of a heat driving
circuit of Fig. 4.
Fig. 5C is a wave form of a gate voltage of a transistor of a heat driving circuit
of Fig. 4.
Fig. 5D is a wave form of a base-emitter voltage of a transistor of a switching
device protector of Fig. 4.
Referring to Fig. 3, a microwave oven with an induction heating function of a first
embodiment according to the present invention includes a power supply circuit 1 for
converting an externally supplied alternating current voltage AC into a direct voltage
using a bridge diode BD, for smoothing the thusly converted direct current voltage using
a coil L11, capacitances C11 and C12, and for supplying the thusly smoothed voltage to
a microwave oven with an induction heating function, a microwave heating circuit 2 for
generating a microwave and for executing a microwave heating operation after increasing
an electric power supplied thereto through relay switches RS1 and RS2, an induction
heating circuit 3, having an induction coil IDC, a resonant capacitance C15, and a damper
diode D13, for generating a high frequency magnetic field in accordance with a power
supplied from the power supply circuit 1 and for heating a metal plate MTP, a
microcomputer 5 for generating a pulse width modulation signal PWM so as to enable
a cooking mode selection control signal and so as to drive the microwave heating circuit
2 and the induction heating circuit 3 in accordance with a cooking mode selection signal
outputted from the key input circuit 4 and for controlling a heating selection operation,
a cooking mode selection circuit 6 for switching one of the relay switches RS1 and RS2
connected to the microwave heating circuit 2 and the induction heating circuit 3 at an
initial stage and for selecting one of the microwave heating circuit 2 and the induction
heating circuit 3, and a heating drive circuit 7, switched by a pulse width modulation
signal PWM outputted from the microcomputer 5 and having a switching device Q11, for
supplying an electric power outputted from the power supply circuit 1 to the microwave
heating circuit 2 or the induction heating circuit 3 in accordance with a selection of the
cooking mode selection circuit 6 and for driving one of the microwave heating circuit 2
and the induction heating circuit 3.
The microwave heating circuit 2 includes a high voltage transformer 21 for
increasing the power supplied from the power supply circuit 1 through the relay switches
RS1 and RS2 up to a predetermined level, a high voltage generating circuit 22, having
high voltage diodes D11 and D12 and a high voltage capacitance C14, for converting the
thusly increased high voltage into a direct current voltage, and a magnetron 23 for
generating a microwave in accordance with a supply of the high direct current voltage
converted by the high voltage generating circuit 22.
The cooking mode selection circuit 6 includes a relay drive circuit 61 for
outputting drive signals DSI and DS2 so as to drive first and second relays 62 and 63 in
accordance with a cooking mode selection control signal CSC outputted from the
microcomputer 5, and first and second relays 62 and 63 for selectively switching the relay
switches RSI and RS2 in accordance with drive signals DS1 and DS2 outputted from the
relay drive circuit 61.
The operation of the microwave oven with an induction heating function of a first
embodiment according to the present invention will now be explained with reference to
the accompanying drawings.
To begin with, when an alternating current voltage AC is supplied to the power
supply circuit 1,. the alternating current voltage AC is rectified to a direct current voltage
by a bridge diode BD and smoothed by the coil L11 and the capacitances C11 and C12.
At this time, the relay switch RS1 is connected to the terminal b13 of the invertor
RS 1, and the relay switch RS2 is connected to the terminal C12 of the microwave heating
circuit 2, and there is thusly a disconnection between the microwave heating circuit 2 and
the induction heating circuit 3.
Thereafter, in order to select a microwave heating mode, when a user selects a
microwave cooking mode of the key input circuit 4, the microcomputer 5 recognizes a
key input signal in accordance with a microwave cooking key selected by the user and
generates a cooking mode selection control signal CSS and a pulse width modulation
signal PWM.
Thereafter, the relay drive circuit 61 of the cooking mode selection circuit 6
receives a cooking mode selection control signal CSS outputted from the microcomputer
5 and outputs a relay drive signal DS1 in accordance with the thusly received cooking
mode selection control signal CSS.
Therefore, the relay switch RS1 is connected to the terminal b12 of the microwave
heating circuit 2 by the first relay 62 in accordance with a relay drive signal DS1
outputted from the relay drive circuit 61.
Meanwhile, the switching device Q11 of the heating drive circuit 6 is turned on
and turned off in order in accordance with a pulse width modulation signal PWA
outputted from the microcomputer 5.
Thereafter, when the switching device Q11 is turned on, the direct current voltage
outputted from the power supply circuit 1 is supplied to the capacitance C13 and the high
voltage transformer 21 through the relay switches RS1 and RS2.
In addition, as the switching device Q11 of the heating drive circuit 7 is turned
on and turned off in order, a certain resonant voltage is generated at the capacitance C13
and a primary coil of the high voltage transformer 21 by a direct current voltage supplied
thereto from the power supply circuit 1 and is applied to both ends of the capacitance
C13 and is inducted to a secondary coil of the high voltage transformer 21.
Thereafter, the resonant voltage inducted to the secondary coil of the high voltage
transformer 21 is converted into a direct current voltage through the high voltage diodes
D11 and D12 and the high capacitance C14 of the high voltage generating circuit 22 and
drives the magnetron 23.
Therefore, the magnetron 23 generates a high frequency wave so as to heat food.
Thereafter, when the cooking operation is completed, a cooking completion control
signal is outputted from the microcomputer 5, and the delay drive circuit 61 of the
cooking mode selection circuit 6 receives the cooking completion control signal outputted
from the microcomputer 5, stops the drive of the first relay 62, and sets the relay switch
RS1 to the initial stage. That is, the relay drive circuit 61 is connected to the terminal b13
of the induction heating circuit 3.
Therefore, the direct current outputted from the power supply circuit 1 is not
supplied to the microwave heating circuit 2 and the induction heating circuit 3.
Meanwhile, when the user selects an induction heating mode from the key input
circuit 4, the microcomputer 5 recognizes a key input signal corresponding to the
induction heating mode and outputs a selection control signal CSS and a pulse width
modulation signal PWM in accordance with the recognition.
Thereafter, the relay drive circuit 61 of the cooking mode selection circuit 6
receives a cooking mode selection control signal CSS outputted from the microcomputer
5 and outputs a relay drive signal DS2 so as to driving the second relay 63.
That is, the first relay 62 is not driven by the relay drive circuit 61. The second
relay 63 switches the relay switch RS2 to the terminal c13 by a driving signal DS2
outputted from the relay drive circuit 61.
Meanwhile, the switching device Q11 of the heating drive circuit 7 is turned on
and turned off in order in accordance with a pulse width modulation signal PWM
outputted from the microcomputer 5.
Therefore, the direct voltage outputted from the power supply circuit 1 is supplied
to the induction coil IDC and the resonant capacitance C15 because the power supply
circuit 1, the induction heating circuit 3 and the heating drive circuit 7 are disconnected
therefrom.
In addition, since the switching device Q11 of the heating drive circuit 7 is turned
on and turned off in order, a predetermined resonant voltage occurs at the capacitance
C15 and the induction coil IDC and is applied to both ends of the capacitance C15. At
this time, a relatively high resonant voltage occurs at the induction coil IDC.
Therefore, since a high frequency magnetic field is formed by the induction coil
IDC and applied to the metal plate MPT, the metal pan is heated, the food in the pan is
heated.
Thereafter, the cooking operation mode is completed, and the microcomputer 5
outputs a cooking completion control signal, and the relay drive circuit 61 stops the drive
of the second relay 63, and the relay switch RS2 is connected to the terminal c12.
Referring to Fig. 4, the microwave oven with an induction heating function of a
second embodiment according to the present invention has the same construction as the
first embodiment except a switching device protection circuit 8 for protecting the
switching device Q11 by cutting off the pulse width modulation signal PWM of the
microcomputer 5, which is subject to determining an ON/OFF interval of the switching
device Q11 of the heating drive circuit 7 when a resonant level is higher than a
predetermined level by detecting the resonant voltage level outputted from the induction
heating circuit 6.
The switching protection circuit 8 includes a zenor diode ZD1 for passing through
the resonant voltage outputted from the microwave heating circuit 2 or the induction
heating circuit 6 when it exceeds a predetermined level, and a transistor Q12 for receiving
the voltage outputted from the zenor diode ZD1 through the capacitances Rl and R2 and
for cutting off the pulse width modulation signal PWM outputted from the microcomputer
and applied to the heating drive circuit 7.
The operation of the microwave oven with an induction heating function of the
second embodiment according to the present invention will now be explained with
reference to Fig. 5.
To begin with, as described in the first embodiment, when a user inputs a
corresponding key of the key input circuit 4 so as to select a microwave cooking mode,
the relay switch RS1 is connected to the terminal b12 by the first relay 62 and the second
relay 63 for selecting the microwave heating circuit 2.
Thereafter, the power outputted from the power supply circuit 1 is applied to the
capacitance C13 and a primary coil of the high voltage transformer 21 and applied to both
ends of the capacitance C13 in accordance with a switching operation of the switching
device Q11 of the heating drive circuit 7.
Here, when a relatively high resonant voltage is applied to both ends of the
capacitance C13 as shown in Fig. 5A, that is, a voltage VCE is applied between the
collector terminal and the emitter terminal of the switching device Q11, since the voltage
VCE between the collector terminal and the emitter terminal of the switching device Q11
is high than that of the zenor voltage VZ of the zenor diode ZD1 of the switching device
protection circuit 8, the voltage VCE is divided by the capacitances R1 and R2.
Therefore, a high voltage as shown in Fig. 5D is applied to the base terminal of the
transistor Q12.
Therefore, the transistor Q12 is turned on in accordance with a high voltage
applied to the base terminal thereof and by-passes the pulse width modulation signal
PWM outputted from the microcomputer 5 to the ground terminal.
A low level voltage, as shown in Fig. 5C, is applied to the gate terminal of the
switching device Q11 of the heating drive circuit 7, and a certain level of voltage lower
than that of the zenor voltage VZ is not applied to the collector terminal of the switching
device Q11, the switching device Q11 is safely protected.
Meanwhile, when the user inputs a corresponding key from the key input so as to
select the induction heating circuit 3, the relay switch RS2 of the first and second relays
62 and 63 are turned on, and since the relay switch RSI maintains a turned-on state, a
certain resonant voltage is applied to both ends of the capacitance C15 of the induction
heating terminal 3.
As shown in Fig. 5A, when a relatively high resonant voltage VCE is applied to
both ends of the capacitance C15, the zenor diode ZD and the transistor Q12 become
activated, and since a certain voltage higher than that of the zenor voltage VZ is not
applied to the collector terminal of the switching device Q11, the switching device Q11
is safely protected.
As described above, the microwave oven with an induction heating function is
capable of selectively using a microwave oven and an induction heat function without any
interruptions from a microwave oven heating circuit and an induction heating circuit when
cooking food by providing first and second relays which is selectively used for a certain
mode. In addition, the microwave heating circuit and the induction heating circuit can be
safely used irrespective of the internal pressures of the high voltage resonant and relays
due to use of the electric power of 220V.
Moreover, the present invention is directed to expanding the life span of the
product by preventing damages of the switching device due to a relatively high resonant
voltage by stopping the drive of the switching device for a predetermined time when the
resonant voltage exceeds a predetermined level by detecting the resonant voltage which
occurs due to the noise components contained in the input voltage and electric power
between turn on/off intervals of the switching device of the heating drive circuit.
Claims (6)
- A microwave oven with an induction heating function having a microwave heating circuit and an induction heating circuit which are selectively used by a user, comprising:a microcomputer for generating a cooking mode selection control signal and a pulse width modulation signal in accordance with a cooking mode selection key input and for controlling a selection operation of said microwave heating circuit and said induction heating circuit;relay drive means for generating a first drive signal and a second drive signal in accordance with a cooking mode selection control signal outputted from said microcomputer and for outputting a certain drive signal; andfirst and second relays, selectively switched by said first drive signal or said second drive signal outputted from said relay drive means, for supplying an electric voltage of power supply means to the microwave heating circuit and the induction heating circuit.
- The microwave oven of claim 1, wherein of said first or second relays, one is at an initial stage, and the other is switched to one of the microwave heating circuit and the induction heating circuit corresponding to its cooking mode.
- The microwave oven of claim 1, wherein said first and second relays switch the microwave heating circuit or the induction heating circuit to either the power supply means or the cooking drive means.
- The microwave oven of claim 1, wherein said relay drive means drives one of the first and second relays in accordance with a mode selection control signal of said microcomputer.
- A microwave oven with an induction heating function having a microwave heating circuit and an induction heating circuit which are selectively used by a user, comprising:a microcomputer for generating a cooking mode selection control signal and a pulse width modulation signal in accordance with a cooking mode selection key input and for controlling a selection operation of said microwave heating circuit and said induction heating circuit;cooking mode selection means for selecting one of said microwave heating circuit and said induction heating circuit corresponding to a cooking mode selection control signal outputted from said microcomputer and for supplying a voltage of power supple means to a heating drive means; anda switching device protection means for cutting off a pulse width modulation signal of said microcomputer, which determines an ON/OFF interval of the switching device of said heating drive means when a resonant voltage exceeds a predetermined level by detecting the resonant voltage outputted from one of the microwave heating circuit and the induction heating circuit and for protecting the switching device.
- The microwave oven of claim 5, wherein said switching device protection means includes a zenor diode which becomes activated when a resonant voltage at the switching device of the heating drive means exceeds a predetermined level, and a transistor for receiving a voltage outputted from said zenor diode through first and second capacitances and for cutting off a pulse width modulation signal applied to the gate terminal of the switching device.
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR2906294 | 1994-11-07 | ||
KR1019940029062A KR960020611A (en) | 1994-11-07 | 1994-11-07 | Inverter selector of compound cooker |
KR2916294 | 1994-11-08 | ||
KR1019940029162A KR0141793B1 (en) | 1994-11-08 | 1994-11-08 | Switching element protection device for complex cooker |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0711099A2 true EP0711099A2 (en) | 1996-05-08 |
EP0711099A3 EP0711099A3 (en) | 1997-01-08 |
Family
ID=26630673
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP95402456A Withdrawn EP0711099A3 (en) | 1994-11-07 | 1995-11-03 | Microwave oven with induction heating function |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0711099A3 (en) |
CN (1) | CN1092778C (en) |
BR (1) | BR9505113A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103763803A (en) * | 2014-01-23 | 2014-04-30 | 美的集团股份有限公司 | Electromagnetic resonance control circuit, electromagnetic heating device and method for controlling transistor |
WO2019106488A1 (en) * | 2017-11-29 | 2019-06-06 | BSH Hausgeräte GmbH | Domestic appliance device |
WO2024099254A1 (en) * | 2022-11-09 | 2024-05-16 | 广东美的厨房电器制造有限公司 | Variable-frequency driving circuit and cooking apparatus |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101442220B (en) * | 2007-08-28 | 2011-08-10 | 上海中策工贸有限公司 | Transmission system |
CN101377312B (en) * | 2007-08-28 | 2012-07-04 | 上海中策工贸有限公司 | Power transmission system of microwave oven |
CN106287863B (en) * | 2015-06-10 | 2018-09-11 | 佛山市顺德区美的电热电器制造有限公司 | Electromagnetic heater and its control method and control circuit |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2288442A1 (en) * | 1974-10-18 | 1976-05-14 | Matsushita Electric Ind Co Ltd | HIGH FREQUENCY HEATING DEVICE |
JPS63299081A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
JPS63299089A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
JPS63299075A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
EP0318645A1 (en) * | 1987-11-28 | 1989-06-07 | Kabushiki Kaisha Toshiba | Composite cooking system having microwave heating and induction heating |
DE4038560A1 (en) * | 1990-12-04 | 1992-06-11 | Licentia Gmbh | Power control of microwave and induction heating cooker - involves microprocessor limiting load on inverter by switching of microwave oscillator and regulation of induction energy |
-
1995
- 1995-11-03 EP EP95402456A patent/EP0711099A3/en not_active Withdrawn
- 1995-11-07 BR BR9505113A patent/BR9505113A/en not_active Application Discontinuation
- 1995-11-07 CN CN95118285A patent/CN1092778C/en not_active Expired - Fee Related
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2288442A1 (en) * | 1974-10-18 | 1976-05-14 | Matsushita Electric Ind Co Ltd | HIGH FREQUENCY HEATING DEVICE |
JPS63299081A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
JPS63299089A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
JPS63299075A (en) * | 1987-05-29 | 1988-12-06 | Matsushita Electric Ind Co Ltd | High-frequency heating device |
EP0318645A1 (en) * | 1987-11-28 | 1989-06-07 | Kabushiki Kaisha Toshiba | Composite cooking system having microwave heating and induction heating |
DE4038560A1 (en) * | 1990-12-04 | 1992-06-11 | Licentia Gmbh | Power control of microwave and induction heating cooker - involves microprocessor limiting load on inverter by switching of microwave oscillator and regulation of induction energy |
Non-Patent Citations (3)
Title |
---|
PATENT ABSTRACTS OF JAPAN vol. 013, no. 132 (E-736), 31 March 1989 & JP-A-63 299075 (MATSUSHITA ELECTRIC IND CO LTD), 6 December 1988, * |
PATENT ABSTRACTS OF JAPAN vol. 013, no. 132 (E-736), 31 March 1989 & JP-A-63 299081 (MATSUSHITA ELECTRIC IND CO LTD), 6 December 1988, * |
PATENT ABSTRACTS OF JAPAN vol. 013, no. 132 (E-736), 31 March 1989 & JP-A-63 299089 (MATSUSHITA ELECTRIC IND CO LTD), 6 December 1988, * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103763803A (en) * | 2014-01-23 | 2014-04-30 | 美的集团股份有限公司 | Electromagnetic resonance control circuit, electromagnetic heating device and method for controlling transistor |
CN103763803B (en) * | 2014-01-23 | 2016-01-20 | 美的集团股份有限公司 | The control method of electromagnetic resonance control circuit, electromagnetic heater and transistor |
WO2019106488A1 (en) * | 2017-11-29 | 2019-06-06 | BSH Hausgeräte GmbH | Domestic appliance device |
WO2024099254A1 (en) * | 2022-11-09 | 2024-05-16 | 广东美的厨房电器制造有限公司 | Variable-frequency driving circuit and cooking apparatus |
Also Published As
Publication number | Publication date |
---|---|
CN1128337A (en) | 1996-08-07 |
BR9505113A (en) | 1997-09-09 |
CN1092778C (en) | 2002-10-16 |
EP0711099A3 (en) | 1997-01-08 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0517226B1 (en) | Power source apparatus for microwave oven | |
US4730147A (en) | Method and arrangement for the operation of a gas discharge lamp | |
CN104782033A (en) | Soft-start for resonant converters | |
KR920004988B1 (en) | Microwave range | |
EP0711099A2 (en) | Microwave oven with induction heating function | |
KR910006177B1 (en) | Composite cooking system having microwave heating and induction heating | |
KR101093539B1 (en) | Induction heating apparatus | |
JP3376227B2 (en) | Inverter device | |
CN111901914B (en) | Control circuit and method of electromagnetic heating appliance and electromagnetic heating appliance | |
CN110944420B (en) | Electromagnetic heating device and heating control method thereof | |
EP1255421A2 (en) | Induction cooking apparatus with improved characteristics | |
JP2001357970A (en) | High frequency heating device | |
JP2982364B2 (en) | Inverter for induction heating | |
CN113452357B (en) | Driving circuit and driving method of IGBT | |
KR20200045796A (en) | Electronic cooking device having enhanced stability | |
JPH07327377A (en) | Inverter | |
EP3836753B1 (en) | Method and system to control a qr-inverter in a induction cooking appliance | |
CN210670622U (en) | Low-power heating circuit and cooking utensil | |
KR910006178B1 (en) | Composite cooking system having microwave heating and induction heating | |
JP2001023770A (en) | Heating cooker | |
KR910006175B1 (en) | Composite cooking system having microwave heating and induction heating | |
JPH05326128A (en) | High-frequency invertor | |
JPH09223577A (en) | Induction heating cooking appliance | |
JP3060562B2 (en) | High frequency inverter | |
EP0269414A2 (en) | Induction heating circuits for cooking appliances |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): DE FR GB |
|
PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): DE FR GB |
|
17P | Request for examination filed |
Effective date: 19970419 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN |
|
18W | Application withdrawn |
Withdrawal date: 19980511 |