EP0981265A1 - Microwave oven providing a security to the high-voltage-transformer - Google Patents
Microwave oven providing a security to the high-voltage-transformer Download PDFInfo
- Publication number
- EP0981265A1 EP0981265A1 EP99302489A EP99302489A EP0981265A1 EP 0981265 A1 EP0981265 A1 EP 0981265A1 EP 99302489 A EP99302489 A EP 99302489A EP 99302489 A EP99302489 A EP 99302489A EP 0981265 A1 EP0981265 A1 EP 0981265A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- voltage transformer
- rectifying
- power
- microwave oven
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/64—Heating using microwaves
- H05B6/66—Circuits
- H05B6/666—Safety circuits
-
- 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
Definitions
- the present invention relates to a microwave oven including a high-voltage transformer and overcurrent protection means for protecting the high-voltage transformer from an initial overcurrent condition, the overcurrent protection means comprising a resistor in series between a power in terminal and a primary winding of the high-voltage transformer and a relay in parallel with the resistor.
- FIG. 2 is a circuit diagram of a known power control circuit of a microwave oven.
- the microwave oven has a power supply part 101, a high-voltage transformer 109 for stepping up the normal voltage from the power supply part 101 to a high level and a magnetron 110 for generating microwaves which is powered from the output of high-voltage transformer 101.
- a thermal switch 103 responsive to the temperature in the cooking chamber (not shown), a door switch 105 responsive to opening and closing of the oven door (not shown) and a monitor switch 107 for controlling supply of power to said high-voltage transformer 109 on the basis of the states of the thermal and door switches 103, 105 are connected between the power supply part 101 and the high-voltage transformer 109.
- the thermal switch 103 is disposed between the power supply part 101 and the monitor switch 107
- the door switch 105 is disposed between the power supply part 101 and the high-voltage transformer 109.
- An overcurrent protection relay 121 connected in series between the door switch 105 and the high-voltage transformer 109.
- An overcurrent protection resistance unit 123 is connected in parallel with the overcurrent protection relay 121.
- the coil 115 of the relay 121 is connected in parallel with the monitor switch 107.
- the monitor switch 107 has a bypass connecting node 131 and a branch connecting node 133.
- the bypass connecting node 131 is a point on a bypass line 130 disposed between the relay coil 115 and the high-voltage transformer 109, for supplying power from said power supply part 101 to the bypass line 130.
- the branch connecting node 133 is a point on the line connected to the high-voltage transformer 109 for supplying power to the relay coil 115 and the high-voltage transformer 109.
- the thermal and door switches 103, 105 are closed.
- the moving contact of the monitor switch 107 contacts the branch connecting node 133 and the power supply part 101 is connected in series with the overcurrent protection resistance unit 123 and the high voltage transformer 109. Therefore, the initial current supplied from said power supply part 101 is reduced by the overcurrent protection resistance unit 123.
- the relay coil 115 is energised and the overcurrent protection relay 121 is closed.
- an overcurrent protection relay is operated when AC power is applied.
- the AC power changes regularly and periodically. Therefore, the known microwave oven has a shortcoming in that the operation of the overcurrent protection relay becomes unstable.
- a microwave oven according to the present invention is characterised by rectifying means for rectifying current input to the oven for energising the coil of the relay.
- an oven according to the present invention includes smoothing means for smoothing the output of the rectifying circuit.
- the rectifying means comprises a bridge rectifier and the smoothing means comprises a capacitor in parallel with said coil.
- resistor means is included for reducing the voltage of the current to be rectified by the rectifying means.
- a microwave oven has a power supply part 1, a magnetron 10 for generating microwaves and a high-voltage transformer 9 for stepping up mains voltage to a high level.
- a thermal switch 3 responsive to the temperature in the cooking chamber (not shown) and a door switch 5 responsive to opening and closing of the oven door (not shown) and a monitor switch 7 for controlling the supply of power to the high-voltage transformer 9 on the basis of the states of the thermal and door switches 3, 5 are connected between said power supply part 1 and the high-voltage transformer 9.
- the thermal and door switches 3, 5 are connected in series between the power supply part 1 and the high-voltage transformer 9.
- the power control device further comprises an overcurrent protection relay 21 disposed in series between the thermal and door switches 3, 5, an overcurrent protection resistance unit 23 connected in parallel with the overcurrent protection relay 21, and a rectifying part 8 for rectifying the current from the power supply part 1.
- the rectifying part 8 has at least one voltage-controlled resistor 13, a bridge diode 11 connected to said voltage-controlled resistor 13, a capacitor 17 connected in parallel with the bridge diode 11, and the coil 15 of the overcurrent protection relay 21.
- the monitor switch 7 has a bypass connecting node 31 and a branch connecting node 33.
- the bypass connecting node 31 is a point on a bypass line 30 disposed between the relay coil 15 and the high-voltage transformer 9.
- the branch connecting node 3 is a point on the line connected to the high-voltage transformer 9 for supplying power to the relay coil 15 and the high-voltage transformer 9.
- the thermal and door switches 3, 5 are closed.
- the moving contact of the monitor switch 7 contacts the branch connecting node 33. Because the current supplied from the power supply part 1 passes through the overcurrent protection resistance unit 23, the initial current is reduced and at the same time, the current branched to said rectifying part 8 is rectified so that stable current is supplied to the relay coil 15. This causes the overcurrent protection relay 21 to close shortly after current begins to flow through the primary winding of the high-voltage transformer 9.
- the high-voltage transformer is protected from an initial overcurrent condition and the overcurrent protection relay is controlled by induction energy generated from the relay coil by use of a stable current.
- the inrush relay is controlled by a stable current, and thus, the reliability is improved.
Abstract
Description
- The present invention relates to a microwave oven including a high-voltage transformer and overcurrent protection means for protecting the high-voltage transformer from an initial overcurrent condition, the overcurrent protection means comprising a resistor in series between a power in terminal and a primary winding of the high-voltage transformer and a relay in parallel with the resistor.
- Figure 2 is a circuit diagram of a known power control circuit of a microwave oven. As illustrated, the microwave oven has a
power supply part 101, a high-voltage transformer 109 for stepping up the normal voltage from thepower supply part 101 to a high level and amagnetron 110 for generating microwaves which is powered from the output of high-voltage transformer 101. - In the power supply control circuit, a
thermal switch 103 responsive to the temperature in the cooking chamber (not shown), adoor switch 105 responsive to opening and closing of the oven door (not shown) and amonitor switch 107 for controlling supply of power to said high-voltage transformer 109 on the basis of the states of the thermal anddoor switches power supply part 101 and the high-voltage transformer 109. Thethermal switch 103 is disposed between thepower supply part 101 and themonitor switch 107, and thedoor switch 105 is disposed between thepower supply part 101 and the high-voltage transformer 109. - An
overcurrent protection relay 121 connected in series between thedoor switch 105 and the high-voltage transformer 109. An overcurrentprotection resistance unit 123 is connected in parallel with theovercurrent protection relay 121. Thecoil 115 of therelay 121 is connected in parallel with themonitor switch 107. - The
monitor switch 107 has abypass connecting node 131 and abranch connecting node 133. Thebypass connecting node 131 is a point on abypass line 130 disposed between therelay coil 115 and the high-voltage transformer 109, for supplying power from saidpower supply part 101 to thebypass line 130. Thebranch connecting node 133 is a point on the line connected to the high-voltage transformer 109 for supplying power to therelay coil 115 and the high-voltage transformer 109. - With this configuration, during normal operation, the thermal and
door switches monitor switch 107 contacts thebranch connecting node 133 and thepower supply part 101 is connected in series with the overcurrentprotection resistance unit 123 and thehigh voltage transformer 109. Therefore, the initial current supplied from saidpower supply part 101 is reduced by the overcurrentprotection resistance unit 123. In addition, therelay coil 115 is energised and theovercurrent protection relay 121 is closed. - As described above, in the known power control device for a microwave oven, an overcurrent protection relay is operated when AC power is applied. However, the AC power changes regularly and periodically. Therefore, the known microwave oven has a shortcoming in that the operation of the overcurrent protection relay becomes unstable.
- A microwave oven according to the present invention is characterised by rectifying means for rectifying current input to the oven for energising the coil of the relay.
- Preferably, an oven according to the present invention includes smoothing means for smoothing the output of the rectifying circuit. More preferably, the rectifying means comprises a bridge rectifier and the smoothing means comprises a capacitor in parallel with said coil.
- Preferably, resistor means is included for reducing the voltage of the current to be rectified by the rectifying means.
- An embodiment of the present invention will now be described, by way of example, with reference to Figure 1 of the accompanying drawings, in which:-
- Figure 1 is a circuit diagram of a power control device for a microwave oven according to the present invention; and
- Figure 2 is a circuit diagram of a known power control device for a microwave oven.
-
- Referring to Figure 1, a microwave oven has a
power supply part 1, amagnetron 10 for generating microwaves and a high-voltage transformer 9 for stepping up mains voltage to a high level. - In the power supply control circuit, a
thermal switch 3 responsive to the temperature in the cooking chamber (not shown) and adoor switch 5 responsive to opening and closing of the oven door (not shown) and amonitor switch 7 for controlling the supply of power to the high-voltage transformer 9 on the basis of the states of the thermal anddoor switches power supply part 1 and the high-voltage transformer 9. The thermal anddoor switches power supply part 1 and the high-voltage transformer 9. The power control device further comprises anovercurrent protection relay 21 disposed in series between the thermal anddoor switches protection resistance unit 23 connected in parallel with theovercurrent protection relay 21, and a rectifyingpart 8 for rectifying the current from thepower supply part 1. - The rectifying
part 8 has at least one voltage-controlledresistor 13, abridge diode 11 connected to said voltage-controlledresistor 13, acapacitor 17 connected in parallel with thebridge diode 11, and thecoil 15 of theovercurrent protection relay 21. - The
monitor switch 7 has abypass connecting node 31 and abranch connecting node 33. Thebypass connecting node 31 is a point on abypass line 30 disposed between therelay coil 15 and the high-voltage transformer 9. Thebranch connecting node 3 is a point on the line connected to the high-voltage transformer 9 for supplying power to therelay coil 15 and the high-voltage transformer 9. - With this configuration, during normal operation, the thermal and
door switches monitor switch 7 contacts thebranch connecting node 33. Because the current supplied from thepower supply part 1 passes through the overcurrentprotection resistance unit 23, the initial current is reduced and at the same time, the current branched to said rectifyingpart 8 is rectified so that stable current is supplied to therelay coil 15. This causes theovercurrent protection relay 21 to close shortly after current begins to flow through the primary winding of the high-voltage transformer 9. - Accordingly, the high-voltage transformer is protected from an initial overcurrent condition and the overcurrent protection relay is controlled by induction energy generated from the relay coil by use of a stable current.
- As described above, the inrush relay is controlled by a stable current, and thus, the reliability is improved.
Claims (11)
- A microwave oven including a high-voltage transformer (9) and overcurrent protection means (8, 21, 23) for protecting the high-voltage transformer from an initial overcurrent condition, the overcurrent protection means comprising a resistor (23) in series between a power in terminal and a primary winding of the high-voltage transformer (9) and a relay (21) in parallel with the resistor (23), characterised by rectifying means (11) for rectifying current input to the oven for energising the coil (15) of the relay (21).
- An oven according to claim 1, including smoothing means (17) for smoothing the output of the rectifying circuit (11).
- An oven according to claim 2, wherein the rectifying means (11) comprises a bridge rectifier (11) and the smoothing means (17) comprises a capacitor (17) in parallel with said coil.
- An oven according to claim 1, 2 or 3, including resistor means (13) for reducing the voltage of the current to be rectified by the rectifying means (8).
- A power control device for a microwave oven having a power supply part, a magnetron for generating high-frequency energy and a high-voltage transformer for stepping up normal voltage to high level, comprising: an inrush switch disposed between said power support part and said high-voltage transformer;an inrush resistance unit coupled in parallel to said inrush switch;a rectifying part for rectifying the current supplied from said power supply part; and an induction coil for driving said inrush switch by generating induction power by use of the rectified current by said rectifying part.
- A power control device for a microwave oven according to claim 5, further comprising:a bypass line connected to said rectifying part and said high-voltage transformer while being disposed between said rectifying part and said high-voltage transformer; anda monitor switch capable of being connected to a branch connecting node for connecting said power supplied current to said rectifying part and said high-voltage transformer at the same time, or to a bypass connecting node for connecting said power supplied current to said bypass line.
- A power control device for a microwave oven according to claim 6, wherein said monitor switch is capable of switching said power supplied current to said branch connecting node from said bypass connecting node when said high-voltage transformer starts to operate.
- A power control device for a microwave oven according to claim 6, wherein said rectifying part includes at least one voltage-controlled resistor.
- A power control device for a microwave oven according to claim 6, further comprising a condenser connected in parallel with said induction coil.
- A power control device for a microwave oven according to one of the claims 5 to 9, wherein said inrush switch is a relay.
- A power control method for a microwave oven having a power supply part, a magnetron for generating high-frequency energy, a high-voltage transformer for stepping up normal voltage to high level, an inrush switch disposed between said power support part and said high-voltage transformer, and an inrush resistance unit connected in parallel with said inrush switch, comprising the steps of;rectifying current supplied from said power supply part at the same time while supplying said supplied current to said high-voltage transformer; generating induction power by use of current rectified by said rectifying part; andturning on said inrush switch by said induction power.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
KR1019980033738A KR100271362B1 (en) | 1998-08-20 | 1998-08-20 | Power control appratus and method of microwave oven |
KR3373898 | 1998-08-20 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0981265A1 true EP0981265A1 (en) | 2000-02-23 |
EP0981265B1 EP0981265B1 (en) | 2004-06-30 |
Family
ID=19547701
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP99302489A Expired - Lifetime EP0981265B1 (en) | 1998-08-20 | 1999-03-30 | Microwave oven providing a security to the high-voltage-transformer |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0981265B1 (en) |
KR (1) | KR100271362B1 (en) |
DE (1) | DE69918380T2 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150146459A1 (en) * | 2012-10-31 | 2015-05-28 | Zte Corporation | High-voltage protection circuit, high-voltage protection method and power supply |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR20010081569A (en) * | 2000-02-16 | 2001-08-29 | 윤종용 | Power control apparatus for microwave oven |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1239789A (en) * | 1968-10-31 | 1971-07-21 | Dysona Ind Ltd | Improvements relating to microwave ovens |
FR2066097A5 (en) * | 1970-10-12 | 1971-08-06 | Matsushita Electric Ind Co Ltd | |
US4556773A (en) * | 1981-03-20 | 1985-12-03 | Matsushita Electric Industrial Co., Ltd. | High frequency heating appliance having protection against rush currents |
FR2765040A1 (en) * | 1997-06-19 | 1998-12-24 | Daewoo Electronics Co Ltd | Protection against starting overcurrents in microwave ovens |
-
1998
- 1998-08-20 KR KR1019980033738A patent/KR100271362B1/en not_active IP Right Cessation
-
1999
- 1999-03-30 DE DE69918380T patent/DE69918380T2/en not_active Expired - Lifetime
- 1999-03-30 EP EP99302489A patent/EP0981265B1/en not_active Expired - Lifetime
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB1239789A (en) * | 1968-10-31 | 1971-07-21 | Dysona Ind Ltd | Improvements relating to microwave ovens |
FR2066097A5 (en) * | 1970-10-12 | 1971-08-06 | Matsushita Electric Ind Co Ltd | |
US4556773A (en) * | 1981-03-20 | 1985-12-03 | Matsushita Electric Industrial Co., Ltd. | High frequency heating appliance having protection against rush currents |
FR2765040A1 (en) * | 1997-06-19 | 1998-12-24 | Daewoo Electronics Co Ltd | Protection against starting overcurrents in microwave ovens |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20150146459A1 (en) * | 2012-10-31 | 2015-05-28 | Zte Corporation | High-voltage protection circuit, high-voltage protection method and power supply |
US9343951B2 (en) * | 2012-10-31 | 2016-05-17 | Zte Corporation | High-voltage protection circuit, high-voltage protection method and power supply |
Also Published As
Publication number | Publication date |
---|---|
EP0981265B1 (en) | 2004-06-30 |
DE69918380D1 (en) | 2004-08-05 |
DE69918380T2 (en) | 2005-08-11 |
KR20000014346A (en) | 2000-03-06 |
KR100271362B1 (en) | 2000-11-01 |
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