Driving circuit of turntable motor in microwave oven

Abstract: The present invention relates in general to a driving circuit of a turntable motor in microwave oven, and more particularly to a driving circuit for driving a turntable motor which is operated at a low voltage. A driving circuit of a turntable motor in a microwave oven for receiving a cooking command to thereby cook the food, the circuit includes: voltage changing means (140) for transforming a commonly used AC power supply into a low level voltage; control means (180) for generating a control signal to switching means (150) according to a key signal generated from key input means (170); and switching means for selectively supplying a low level voltage generated from the voltage changing means according to the control signal generated from the control means.

Description: The present invention relates in general to a driving circuit of a turntable motor in microwave oven, and more particularly to a driving circuit for driving a turntable motor which is operated at a low voltage. Generally, microwave ovens utilize microwaves when cooking foods. In other words, when the microwaves are applied to food molecules in the food, frictional heat is generated therefrom. As a result, the food is heated by the frictional heat. The microwaves are generated by a magnetron which performs an oscillating operation at a fundamental frequency. Figures 7 and 8 show such a microwave oven performing a cooking operation by heating the food with the microwaves generated by the magnetron as shown in this drawings, where the microwave oven includes a magnetron 20, a high voltage transformer 10 (hereinafter referred to as HVT) connected to the magnetron 20 for applying a high voltage to the magnetron 20, a lamp for lighting an inside of a cooking chamber 40, a turntable motor 50 for rotating the food (not shown) so that the food can be evenly cooked during the operation of the magnetron 20, a fan motor 80 for cooling the magnetron 20 and circulating air in the cooking chamber 40 during the operation of the magnetron 20, a relay 120 and a relay 130 being turned on/off to control an alternating current (referred to hereinafter as AC) power supply to a lamp (not shown), a turntable motor 50 and a fan motor 80 and the like. Unexplained reference number 110 is a switch for stopping the operation of the magnetron 20 when a door (not shown) is open. However, there is a problem in the conventional microwave oven according to the prior art thus constructed, in that the turntable motor driving circuit is designed only for receiving a commonly used AC power supply, thereby enforcing an unnecessary large size turntable motor, so that production costs are rising and power consumption is increased as well. EP-A-0,244,845 discloses a combined transformer and fan motor having a continuously energised primary winding producing a continuous output voltage from a transformer secondary winding, and a selectively enabled motor shaft rotational output which is selectively actuated by powering a further primary winding. This combined transformer and motor therefore requires two primary windings and a secondary winding in order to provide a low voltage power output. US-A-4,109,306 is an example prior art document disclosing a power supply for providing two different DC voltages from a transformer having center-tapped secondary winding. Accordingly, the present invention is provided to solve aforementioned problem and it is an object of the present invention to provide a small and low-cost driving circuit for a turntable motor in a microwave oven. According to the present invention there is provided a driving circuit suitable for a turntable motor in a microwave oven, comprising: voltage changing means transforming a commonly used AC power supply into a low level voltage; wherein the voltage changing means comprises: a stator coil of a fan motor; and a tap mounted to the stator coil to provide the low level voltage, suitable for driving the turntable motor. Preferably, the circuit further comprises: control means for generating a control signal that is supplied to a switching means according to a key signal generated from a key input means; and switching means for selectively supplying the low level voltage generated from the voltage changing means to the turntable motor by selectively supplying the common AC power to the stator coil of the fan motor according to the control signal. Preferably, the control means generates a control signal for stopping the turntable motor when the user pushes a cooking end button equipped at the key input means, or when a predetermined cooking time elapses, so that a predetermined low voltage generated from the voltage changing means may not be supplied to the turntable motor. Suitably, the low voltage generated from the voltage changing means is about 21 volts. According to a second aspect of the present invention there is provided a microwave oven including the driving circuit defined herein, and a turntable motor driven by the driving circuit. By way of example, specific embodiments of the present invention will now be described with reference to the accompanying drawings in which:- Figure 1 is a block diagram for illustrating a driving circuit of a turntable motor in a microwave oven according to the present invention; Figure 2 is a circuit diagram for illustrating an embodiment of the present invention; Figure 3 is a circuit diagram between a fan motor and a turntable motor; Figure 4 is a sectional view for illustrating a partially broken fan motor; Figure 5 is a sectional view for illustrating a partially broken fan motor and a turntable motor connected at both ends thereof to a fan motor; Figure 6 is a circuit diagram for illustrating another driving circuit of a turntable motor; Figure 7 is a sectional view of a microwave oven according to the prior art; and Figure 8 is a circuit diagram for illustrating a motor driving circuit according to the prior art. A driving circuit of a turntable motor in the microwave oven according to the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 is a block diagram for illustrating a driving circuit of a turntable motor in the microwave oven. As shown in Figure 1, the block diagram consists of voltage transforming means 140 for transforming a commonly used AC power supply input from outside to a predetermined low level voltage. Control means 180 which receives a key signal from key input means 170 and generates a control signal to switching means 150. The switching means 150 for selectively supplying a predetermined low level voltage to turntable motor driving means 160 according to a control signal generated from the control means 180. Next, operation effect of a driving circuit of a turntable motor in the microwave oven according to the present invention thus constructed will be described. When an electric power is applied from an electric power supply (not shown), and a user then pushes a cooking start button equipped at the key input means 170, and a cooking start command is output from the key input means 170 to the control means 180 where the control means serves to generate a control signal to the switching means 150. According to the control signal, the switching means 150 serves to execute switching operations so as to supply a predetermined low level voltage generated from the voltage transforming means 140 to the turntable motor driving means 160. Therefore, the turntable motor is rotated according to the turntable motor driving means 160 to which a predetermined low voltage is applied from the voltage transforming means 140. Next, when the user pushes a cooking end button equipped at the key input means 170 or when a predetermined cooking time elapses, the control means 180 then generates a control signal to the switching means 150 so that a predetermined low level voltage generated from the voltage transforming means 140 may not be supplied to the turntable motor driving means 160. Therefore, the predetermined low level voltage is not supplied to the turntable motor driving means 160, and the turntable 60 is not rotated any more. Figure 2 through Figure 5 are circuit diagrams for illustrating an embodiment of the present invention. The embodiment of the present invention will now be described in detail with reference to the accompanying drawings. Referring to the Figure 2, the commonly used AC power supply Vin is applied from outside to a fan motor 141 according to the control signal generated from the control means 180. Successively, a predetermined low level voltage is supplied to the turntable motor 161 through a low voltage output terminal 144, and thereby the turntable motor 161 is rotated. Meanwhile, as is known in Figure 3, as a tap or tapping 146 is connected to a stator coil 145, an output voltage generated from a tap terminal 146 is transformed to a predetermined low level voltage VL, and it is supplied to the turntable motor 161. Furthermore, as is known in Figure 5, the commonly used AC power supply (not shown) is applied to the stator coil 145 through an input terminal 142, 143 from outside, and a predetermined low level voltage which is transformed by the low voltage output terminal 144 is applied to the turntable motor through the low voltage output terminal 144. Next, operational effect of a driving circuit of turntable motor in a microwave oven according to the present invention thus constructed will now be described in detail. When the user pushes a cooking start button equipped at the key input means 170 and a cooking start command is output from the key input means 170 to the control means 180, the control means generates a control signal to thereby turn on a relay RY. Meanwhile, as the tap 146 is connected to the stator coil 145, an output voltage generated from the tap terminal 146, that is a low level voltage VL, is applied to the turntable motor 161, and the turntable motor 161 is driven to rotate. Next, when the user pushes a cooking end button equipped at the key input means 170 or when a predetermined cooking time elapses, the control means 180 then generates a control signal to the switching means 150 so that a predetermined low level voltage generated from the voltage transforming means 140 may not be supplied to the turntable motor 161 and the fan motor 141. For illustration, Figure 6 is a circuit diagram for illustrating another driving circuit of a turntable motor in a microwave oven. As apparent from the above, there is an advantage in a driving circuit of a turntable motor in the microwave oven according to the embodiment of the present invention, in that a turntable motor is driven to be rotated at a low level voltage which is transformed by voltage transforming means, and in that production costs can be cut down, and also in that consumed AC power can be decreased.

Claims: A driving circuit suitable for a turntable motor (161) in a microwave oven, comprising: voltage changing means transforming a commonly used AC power supply into a low level voltage; wherein the voltage changing means comprises: a stator coil (145) of a fan motor; and a tap (146) mounted to the stator coil (145) to provide the low level voltage, suitable for driving the turntable motor. The circuit as defined in claim 1, wherein the low voltage generated from the voltage changing means is about 21 volts. The circuit as defined in claim 1 or claim 2 wherein the circuit further comprises: control means (180) for generating a control signal that is supplied to a switching means (150) according to a key signal generated from a key input means (170); and switching means (150) for selectively supplying the low level voltage generated from the voltage changing means to the turntable motor by selectively supplying the common AC power to the stator coil of the fan motor according to the control signal. The circuit as defined in claim 3, wherein the control means generates a control signal for stopping the turntable motor (161) when the user pushes a cooking end button equipped at the key input means (170), or when a predetermined cooking time elapses, so that a predetermined low voltage generated from the voltage changing means (145, 146) may not be supplied to the turntable motor. A microwave oven, comprising the driving circuit of any of claims 1 to 4, and a turntable motor driven by the driving circuit.

Inventors: JEON NAM-SIK, KIM YOON-GON, JEON, NAM-SIK, KIM, YOON-GON
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1996
Main classification: H05B6
IPC codes: H05B6