KR200244098Y1 - High Voltage Protection Circuit of Microwave - Google Patents

Abstract

The present invention relates to a high voltage protection circuit of a microwave oven. In the related art, when an abnormality occurs in a high voltage diode such as a high voltage diode by using a high pressure fuse, the high pressure fuse is cut off to prevent damage to the high voltage transformer or other components. Since the price of the high pressure fuse is expensive, there is a problem of raising the cost of the product, and a problem in that the A / S cost is also increased because the defective parts and the high pressure fuse must be replaced together when repairing the product.

Therefore, the present invention is a high-voltage transformer (T1) for inducing the power applied to the first stage to the second stage; A positive temperature coefficient element (PTC) connected to the lower portion of the secondary stage of the high voltage transformer (T1) to block the supply of the abnormal voltage to the latter apparatus by increasing an internal resistance of which the secondary current increases over the high voltage circuit; Consists of a high voltage capacitor (C) and a high voltage diode (D) to boost the voltage output from the secondary side of the high voltage transformer (T1) to a high pressure to deliver to the magnetron, to reduce the cost by using low-cost PTC, product repair It is a very useful design that can reduce the A / S cost because only the parts that are broken during operation need to be replaced.

Description

High Voltage Protection Circuit of Microwave

The present invention relates to a high-voltage protection circuit of a microwave oven, and more particularly, by using a relatively inexpensive positive temperature coefficient (POSITIVE TEMPERATURE COEFFICIENT: hereinafter referred to as "PTC") instead of a high-pressure fuse. It is to provide high voltage protection circuit of microwave oven to reduce A / S cost by only replacing abnormal parts in case of high voltage failure.

In general, a microwave oven is an electronic device that cooks food using high frequency oscillated from a magnetron, and includes a thawing function, a warming function, and a cooking function by a multi-stage output of the magnetron.

In addition to the magnetron, there is a grill cooking function using a heater and a combination function using a heater and a magnetron at the same time. There is also an oven function for circulating hot air inside a cooking chamber with a convection heater and a convection fan installed at the rear of the cooking chamber.

In such a microwave oven, the cooking method is a sensor type automatic cooking control method that detects humidity generated from a food product by heating using a humidity sensor and automatically controls cooking time, and cooking according to cooking names and servings. There is a program type automatic cooking control method that finds a cooking time set by experiment in advance and controls heating during the cooking time by manually inputting the amount.

In order to cook in a microwave oven as described above, the food is put into the cooking chamber with the power connected, the door is closed, the output level is selected, the cooking function is selected, and the start key is pressed to start cooking.

On the other hand, the conventional microwave oven uses a high voltage transformer, a high voltage capacitor, a magnetron, a high voltage diode, etc. to generate a high frequency, the accompanying drawings of Figure 1 is a conventional high-voltage circuit circuit applied to the general microwave oven as described above It is also.

As shown in the figure, a high voltage transformer T1 for inducing the power applied in the first stage to the second stage, and a high voltage capacitor for boosting the voltage to a high pressure by receiving a second output of the high voltage transformer T1 through a fuse. (C) and high voltage diode (D).

In the conventional high voltage unit circuit configured as described above, when power is applied to the first stage of the high voltage transformer T1, voltage is induced in the second stage (approximately 2, OOOV), which is a square wave by the high voltage capacitor (C) and the high voltage diode (D). It becomes the high pressure of about 4, OOOV and it is transmitted to the magnetron of the rear stage.

Here, when the high voltage diode is shorted due to an abnormality, the secondary side of the high voltage transformer T1 and the closed circuit are configured to increase the current. At this time, the secondary current that normally flows is less than 0.3A, but if the closed circuit is configured as described above, the secondary current increases to 1A or more, and in this case, the secondary coil of the high-voltage transformer is overheated and eventually the high-voltage transformer is combusted. .

Therefore, in order to protect the high voltage transformer, a high pressure fuse is usually used, and the high pressure fuse is disconnected when the high voltage transformer is abnormally overheated, thereby preventing damage to the circuit from the high pressure. If the fuse is disconnected, the high voltage diode causing the above fault and the disconnected high voltage fuse must be replaced at the same time.

Therefore, in this case, it is necessary to replace not only the abnormal parts but also the disconnected high pressure fuse, which has a disadvantage in that the cost of repairing a fault is high. Also, since the high pressure fuse is a very expensive part, there is a disadvantage in that the cost increases.

Therefore, the object of the present invention is to solve the conventional problems, and to reduce the cost by using a relatively low-cost positive temperature coefficient (POSITIVE TEMPERATURE COEFFICIENT: hereinafter referred to as "PTC") element instead of the high-pressure fuse (FUSE) It is to provide the high voltage protection circuit of the microwave oven to reduce the A / S cost by replacing only the abnormal parts when the high voltage failure occurs.

An object of the present invention as described above, the high-pressure transformer to induce the power applied to the first stage to the second stage; A positive temperature coefficient element connected to a lower portion of the high-voltage transformer to increase the internal resistance when the secondary current increases beyond the high-voltage circuit of the high voltage transformer to block supply of the abnormal voltage to the rear-end device; It is achieved by having a high voltage capacitor and a high voltage diode to boost the voltage output from the secondary side of the high voltage transformer to a high pressure to deliver to the magnetron.

1 is a circuit diagram of a high voltage part of a conventional microwave oven.

3 is a block diagram of the high voltage protection circuit of the microwave oven according to the present invention.

* Explanation of symbols for main parts of the drawings

T1: high pressure transformer PTC: positive temperature coefficient element

C: high voltage capacitor D: high voltage diode

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as a preferred embodiment to effectively achieve the object of the present invention.

3 is a block diagram of the high voltage protection circuit of the microwave oven according to the present invention.

As shown therein, a high-voltage transformer (T1) for inducing the power applied to the first stage to the second stage; A positive temperature coefficient element (PTC) connected to a lower portion of the secondary stage of the high voltage transformer (T1) to block the supply of the abnormal voltage to the latter apparatus when the secondary current increases due to the abnormality of the secondary circuit; It consists of a high-voltage capacitor (C) and a high-voltage diode (D) for boosting the voltage output from the secondary side of the high-voltage transformer (T1) to a high pressure to deliver to the magnetron.

In the embodiment of the present invention configured as described above, first, in a normal operation, the positive temperature coefficient element PTC has a minimum internal resistance value.

Therefore, the voltage output from the secondary side of the high voltage transformer (T1) is transmitted to the rear end as it is, the high voltage capacitor (C) and the high voltage diode (D) installed at the rear end of the high voltage transformer (T1) as the conventional input voltage It is made into a square wave and repulsed by high pressure and delivered to the magnetron of the rear stage.

On the other hand, if an abnormality occurs in the high-voltage circuit such as a short isochronous of the high-voltage diode (D), the secondary current increases as noted, if the secondary current increases as described above, the inside of the positive temperature coefficient element (PTC) The resistance increases rapidly to cut off the passing current.

Therefore, when the high voltage part is abnormal, since the high pressure output from the secondary side of the high voltage transformer T1 is not transmitted to the rear end, the high voltage part is prevented from being damaged by the abnormal voltage.

Further, in the state in which the high pressure is cut off by the above-described process, when repairing a malfunction, only a component having an abnormality needs to be replaced, thereby reducing the repair cost.

In the case of using a high pressure fuse in the related art, since the high pressure fuse is connected to the live wire, insulation is performed so as to withstand the high pressure. However, a separate insulation structure is required for this purpose, but in the embodiment of the present invention, a positive voltage blocking positive Since the temperature counting element is connected to the secondary side of the transformer, there is no need for a separate insulating structure, so there is an advantage in that the manufacturing is easy.

As described above, when the high voltage part is abnormal, the present invention does not transmit the high voltage output from the secondary side of the high voltage transformer (T1) to the rear end due to an increase in the internal resistance of the PTC. There is an effect that can be prevented.

In addition, there is an advantage in that the repair cost can be reduced because only the parts in which an error occurs during the repair, and the cost can be reduced by using a low-cost PTC instead of an expensive high-pressure fuse.

In addition, when the PTC is placed on the secondary side of the high voltage transformer, there is no need for an insulation structure for insulating a high voltage fuse like the conventional one, thereby making it easy to manufacture.

Claims (1)

A high pressure transformer (T1) for inducing the power applied to the first stage to the second stage; A positive temperature coefficient element (PTC) connected to the lower portion of the secondary stage of the high voltage transformer (T1) to block the supply of the abnormal voltage to the subsequent apparatus when the secondary current increases beyond the high voltage circuit; And a high voltage capacitor (C) and a high voltage diode (D) for boosting the voltage output from the secondary side of the high voltage transformer (T1) to a high voltage and transmitting it to the magnetron.