CN108365745A - Switching Power Supply and cooking equipment - Google Patents

Abstract

The invention discloses a switching power supply, which comprises a first rectifying part and a second rectifying part. The first rectifying part includes a first electrolytic capacitor, and the first rectifying part is used for rectifying the output voltage when the first electrolytic capacitor is enabled. The second rectifying part includes a second electrolytic capacitor, and the second rectifying part is used for rectifying the output voltage when the first electrolytic capacitor fails. The invention also discloses a cooking device. The switching power supply and the cooking equipment according to the embodiment of the present invention provide a second electrolytic capacitor to work when the first electrolytic capacitor fails, thereby forming a backup of the first electrolytic capacitor and effectively prolonging the life of the switching power supply.

Description

Switching power supplies and cooking equipment

technical field

The invention relates to household appliances, in particular to a switching power supply and cooking equipment.

Background technique

Switching power supplies usually include electrolytic capacitors. However, electrolytic capacitors are volatile and have a short lifespan when working at high temperatures, resulting in easy damage to switching power supplies and short service life. Users often cannot effectively judge whether the electrolytic capacitor has reached its service life.

Contents of the invention

Embodiments of the present invention provide a switching power supply and a cooking device.

The switching power supply of the embodiment of the present invention includes:

a first rectification part, the first rectification part including a first electrolytic capacitor, the first rectification part is used to rectify the output voltage when the first electrolytic capacitor is enabled; and

A second rectifying part, the second rectifying part includes a second electrolytic capacitor, and the second rectifying part is used to rectify the output voltage when the first electrolytic capacitor fails.

In some embodiments, the switching power supply further includes a gating element, and the gating element is used for gating the first rectifying part or the second rectifying part to enable the first electrolytic capacitor or the The second electrolytic capacitor.

In some embodiments, the gating element includes a relay, the relay includes a first contact and a second contact, the first electrolytic capacitor is connected to the first contact, and the second electrolytic capacitor connected to the second electrolytic capacitor.

In some embodiments, when the first electrolytic capacitor is effective, the relay is connected to the second contact when it is not powered on, and is connected to the first contact after it is powered on.

In certain embodiments, the relay remains in communication with the second contact upon failure of the first electrolytic capacitor.

In some embodiments, the second electrolytic capacitor is charged at the instant of power-on.

In some embodiments, the first rectifier further includes a first resistor, a second resistor, and a first switch element, and the second resistor is used to divide the voltage to enable the first switch element to enable the The first rectification unit.

In some embodiments, the first switching element includes a diode and a triode, the base of the triode is connected to the anode of the diode, and the cathode of the diode is connected to the first end of the second resistor, so The emitter of the triode is connected to the second end of the second resistor, and the collector of the triode is connected to the gate element.

In some embodiments, the second rectifier includes a third resistor, a fourth resistor, and a second switch element, and the fourth resistor is used to divide the voltage to enable the second switch element to enable the first 2. rectification unit.

In some embodiments, the second switching element includes a triac.

In some implementations, when the ripple voltage of the output voltage is greater than a predetermined value, the second switching element is turned on to enable the second rectification unit, and when the ripple voltage of the output voltage is less than the predetermined value When the predetermined value is exceeded, the first switching element is turned on to enable the first rectifying part.

A cooking device according to an embodiment of the present invention includes the above-mentioned switching power supply.

In some embodiments, the cooking device includes a microwave oven.

The switching power supply and the cooking equipment according to the embodiment of the present invention provide a second electrolytic capacitor to work when the first electrolytic capacitor fails, thereby forming a backup of the first electrolytic capacitor and effectively prolonging the life of the switching power supply.

Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

FIG. 1 is a schematic structural block diagram of a switching power supply according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram of a switching power supply according to an embodiment of the present invention.

FIG. 3 is a graph showing the relationship between life, capacity, and loss angle of an electrolytic capacitor according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of the variation of the ripple voltage with the service time of the electrolytic capacitor according to the embodiment of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary, are only for explaining the embodiments of the present invention, and should not be construed as limiting the embodiments of the present invention.

Referring to FIG. 1 and FIG. 2 , a switching power supply 100 according to an embodiment of the present invention includes a first rectifying part 10 and a second rectifying part 20 . The first rectification unit 10 includes a first electrolytic capacitor 11 , and the second rectification unit 20 includes a second electrolytic capacitor 21 . The first rectifying unit 10 is used for rectifying the output voltage when the first electrolytic capacitor 11 is enabled. The second rectifying unit 20 is used to rectify the output voltage through the second electrolytic capacitor 21 when the first electrolytic capacitor 11 fails.

The switching power supply 100 of the embodiment of the present invention can be applied to the cooking device of the embodiment of the present invention, and the cooking device can be a microwave oven or an electromagnetic oven. In addition, the switching power supply 100 can also be applied to other household appliances, which is not specifically limited.

Specifically, the switching power supply 100 is applied in household appliances for converting input AC power into DC power required by a user end. Generally, an electrolytic capacitor is included in the switching power supply 100 for rectifying and filtering the output voltage. The life of the electrolytic capacitor often determines the life of the entire switching power supply, and the life of the electrolytic capacitor is related to the ambient temperature of its long-term work. Generally, the higher the temperature, the shorter the life of the electrolytic capacitor. For the miniaturization design of switching power supplies and electronic equipment, the working environment temperature of electrolytic capacitors is usually high, and capacitors with large capacity cannot be used. After a period of use, the capacity of electrolytic capacitors will decrease. In addition, the electrolyte inside the electrolytic capacitor has a certain volatility, so the electrolytic capacitor will also lose capacity when it is stored at room temperature or in a state of non-use. When the electrolytic capacitor reaches the service life, the switching power supply will not work. If you need to continue to use the switching power supply, the relevant staff must manually replace the electrolytic capacitor.

Specifically, the formula for calculating the lifetime of an electrolytic capacitor is as follows:

Among them, L is the service life of the electrolytic capacitor when the ambient temperature is T, and _L0 is the rated life of the electrolytic capacitor at the maximum temperature.

As the use time of electrolytic capacitors increases, the capacity of electrolytic capacitors decreases, the internal resistance increases, and the ripple voltage during operation increases.

Please refer to Figure 3, in an example, according to the relationship between the life of the electrolytic container and the capacity, and the loss angle, when the ambient temperature is 100 degrees Celsius, after 10,000 hours of use, the capacity is reduced by 25%, and the loss angle is 1.5, which is determined by the loss angle calculation formula,

Initially, tanθ=0.07, C=4400μF, R=0.04Ω. After 10000 hours of use, tanθ=0.12, C=4400μF, R=0.45Ω.

The formula for calculating the ripple voltage is as follows:

Among them, Δi _L is the ripple current, V _o is the output voltage, V _i is the input voltage, ESR is the equivalent series resistance of the capacitor C, and f _z is the switching frequency. In general, the ESR of a capacitor is in the tens to tens of milliohms. According to the calculation formula, for the part in the brackets, the ESR has a greater influence on the ripple voltage. Generally, when the capacitance is greater than 330μF, the internal resistance is basically equal to the ESR. It can be seen that as the use time increases, the internal resistance increases and the ripple voltage increases.

In the embodiment of the present invention, the first rectifying unit 10 is the loop where the first electrolytic capacitor 11 is located. When the first electrolytic capacitor 11 is enabled, the first rectifying unit 10 is used to rectify the output voltage. The first electrolytic capacitor 11 is enabled, that is, the first electrolytic capacitor 11 has not yet reached its service life and can be used normally. It can be understood that when the first electrolytic capacitor 11 can be used normally, the second electrolytic capacitor 21 is normally stored in the switching power supply 100 as a spare electrolytic capacitor. In some examples, in order to prolong the storage life of the spare electrolytic capacitor, the Charge it regularly. When the first electrolytic capacitor 11 fails, that is, when the service life is reached, the second electrolytic capacitor 21 becomes effective, and the circuit where it is located is the second rectifying unit 20 for rectifying the output voltage.

It can be understood that, compared with the switching power supply including only one electrolytic capacitor, under the same use environment, the design of the dual electrolytic capacitors in the embodiment of the present invention effectively prolongs the service life of the switching power supply 100 . In one example, the switching power supply of the control group only includes an electrolytic capacitor, and the capacitance value of the electrolytic capacitor is 10 μF. In the switching power supply 100 according to the embodiment of the present invention, the capacitance value of the first electrolytic capacitor 11 is 10 μF, and the The capacitance value is 10μF, and the working environment temperature is 80 degrees Celsius. The electrolytic electrolytic capacitor life of the control group is 2.54 years. Correspondingly, in the switching power supply 100 of the embodiment of the present invention, the life of the first electrolytic capacitor 11 is 2.54 years. During the 2.54 years when the first electrolytic capacitor 11 is enabled, the first The capacitance of the second electrolytic capacitor 21 evaporates and decays by 53%. Under the same conditions, the second electrolytic capacitor 21 can continue to work for 2.02 years. Under the same working environment, the service life of the switching power supply 100 is 4.56 years, which is 2.02 years longer than that of the switching power supply of the control group.

In another example, the switching power supply of the control group only includes an electrolytic capacitor, and the capacitance value of the electrolytic capacitor is 10 μF. In the switching power supply 100 according to the embodiment of the present invention, the capacitance value of the first electrolytic capacitor 11 is 10 μF, and the capacitance value of the second electrolytic capacitor 21 is 10 μF. The capacitor value is 10μF, and the working environment temperature is 100 degrees Celsius. The life of the electrolytic electrolytic capacitor in the control group is 0.56 years. Correspondingly, in the switching power supply 100 according to the embodiment of the present invention, the life of the first electrolytic capacitor 11 is 0.56 years. During the 0.56 years when the first electrolytic capacitor 11 is enabled, the first The capacitance of the second electrolytic capacitor 21 evaporates and decays by 32%. Under the same conditions, the second electrolytic capacitor 21 can continue to work for 0.45 years. Under the same working environment, the service life of the switching power supply 100 is 1.01 years, which is 0.45 years longer than that of the switching power supply of the control group.

In addition, it is understandable that due to the high internal temperature of the switching power supply, in order to properly prolong the service life of the electrolytic capacitor, appropriate heat dissipation methods must be adopted, such as adding heat dissipation elements, such as heat sinks or fans, which inevitably makes the volume of the switching power supply Increase, in the embodiment of the present invention, the second electrolytic capacitor 21 is used as a backup, even in a high temperature environment, it can effectively prolong the life of the switching power supply 100 to a certain extent, so the heat dissipation element can be omitted, which is conducive to the miniaturization of the switching power supply Design and be able to save costs.

To sum up, the switching power supply 100 and the cooking equipment in the embodiment of the present invention, by setting the second electrolytic capacitor 21, work when the first electrolytic capacitor 11 fails, thereby forming a backup of the first electrolytic capacitor 11, effectively extending the switching power supply 100. lifespan. At the same time, it is beneficial to the miniaturization design of the switching power supply 100 and can save costs.

In some embodiments, the switching power supply 100 further includes a gating element 30 for gating the first rectifying part 10 or the second rectifying part 20 so as to enable the first rectifying part 10 when the first rectifying part 10 is gating. The electrolytic capacitor 11 enables the second electrolytic capacitor 21 when the second rectifying unit 20 is selected.

Preferably, in such an embodiment, the gating element 30 may be a relay. The relay is a two-node relay, including a first contact a and a second contact b. Wherein, the first electrolytic capacitor 11 is connected to the first contact a, and the second electrolytic capacitor b is connected to the second electrolytic capacitor 21 .

Specifically, the relay can usually be used as a switch for selecting a circuit, and the two contacts are respectively connected to the electrolytic capacitors in the two circuits. When a certain circuit is selected, the electrolytic capacitor in the circuit is enabled. When not powered on, the node of the relay is connected to the second contact b. After being powered on, the node of the relay is connected to the first contact a, the first rectifying part 10 is turned on, and the first electrolytic capacitor 11 works.

It can be understood that the above situation is when the first electrolytic capacitor 11 is effective, that is, when the service life has not been reached, and when the first electrolytic capacitor 11 fails, the relay remains in contact with the second contact after it is not powered on or powered on. b is connected.

That is, when the first electrolytic capacitor 11 is active, the contacts of the relay are connected to the first contact a, and when the first electrolytic capacitor 11 reaches the service life, the contacts of the relay are connected to the second contact b.

The contact gating of the relay is determined according to the life of the first electrolytic capacitor 11. When it is judged that the first electrolytic capacitor 11 has not reached the service life, the first rectifier 10 is selected, the first electrolytic capacitor 11 works, and the first electrolytic capacitor 11 when the service life is reached, the second rectifying part 20 is selected, and the second electrolytic capacitor 21 works.

In some examples, the judgment of the lifetime of the first electrolytic capacitor 11 may be determined according to detected parameters related to the electrolytic capacitor, such as capacitance value. In some other examples, the life of the first electrolytic capacitor 11 can also be determined according to the electrical parameters of the first rectifying unit 10 where it is located, such as the voltage division relationship between the first rectifying unit 10 and the second rectifying unit 20 .

In some embodiments, the first rectifying unit 10 further includes a first resistor 12 , a second resistor 13 and a first switch element 14 . The first resistor 12 and the second resistor 13 are connected in series, the first switch element 14 is connected to the second resistor 13 , and the first rectifier 10 is turned on according to the divided voltage of the second resistor 13 .

Preferably, in such an embodiment, the first switching element 14 includes a diode 141 and a transistor 142, the base B of the transistor 142 is connected to the anode of the diode, the cathode of the diode is connected to the first end of the second resistor 12, and the transistor 142 The emitter E of the transistor 142 is connected to the second end of the second resistor 12 , and the collector C of the triode 142 is connected to the gate element 30 .

Specifically, the diode and the triode have a turn-on voltage, so they can be used as switching elements in the circuit. In this embodiment, when the divided voltage of the second resistor 12 exceeds the turn-on voltage of the diode 141 and the base-emitter of the triode 142 , the contact of the relay will be switched from the second contact b to the first contact a, so that the first rectifier 10 and the first electrolytic capacitor 11 work. The turn-on voltage of the diode 141 is slightly higher than the turn-on voltage of the base-emitter of the transistor 142, which can effectively prevent the false turn-on of the transistor 142.

Further, in such an embodiment, the second rectifying unit 20 includes a third resistor 22, a fourth resistor 23 and a second switch element 24, and the fourth resistor 23 is used to divide the voltage to enable the second switch element 24 to enable The second rectifying part 20 .

Specifically, whether the conduction of the first switch element 14 or the second switch element 24 is determined according to the respective divided voltages of the second resistor 13 and the fourth resistor 23, when the first electrolytic capacitor 11 has not reached the service life, the second resistor The voltage division of 13 can make the first rectifier 10 conduct, and when the first electrolytic capacitor 11 reaches the service life, the voltage division of the fourth resistor 23 can make the second rectifier 20 conduct, and the second electrolytic capacitor 21 works .

Preferably, the second switching element 24 includes a bidirectional thyristor. The bidirectional thyristor takeover includes two antiparallel unidirectional thyristors and two resistors. Thyristors have better sensitivity and withstand voltage, and are usually used as switching elements in high-power electronic circuits such as rectification, inverter and voltage regulation. The two resistors and the two thyristors form a loop. When the first electrolytic capacitor 11 reaches the service life, the divided voltage of the fourth resistor 23 makes the bidirectional thyristor conduct, so that the contact of the relay remains at the second contact a, and the second rectifying part 20 is turned on, and the second electrolytic capacitor 21 works.

Please refer to FIG. 4, specifically, as the service life of the first electrolytic capacitor 11 increases, its service life becomes shorter, the capacity decreases, the loss tangent increases, and the ripple voltage in the output voltage increases accordingly. When the ripple When the ripple voltage increases to a predetermined value, for example, in some examples, when the ripple voltage increases to 43v, the divided voltage of the resistance of the fourth resistor 23 will make the second switching element 24 conduct, at this time, the second The voltage divided by the resistor 13 is not enough to turn on the first switch element 14 , that is, the triode 142 remains in a cut-off state. The contact of the relay is always kept at the second contact b, and the second electrolytic capacitor 21 works. Understandably, when the ripple voltage increases to 43v, it can be considered that the first electrolytic capacitor 11 has reached the service life.

That is to say, in this embodiment, for the detection of the life of the first electrolytic capacitor 11, or the detection of the ripple voltage, there is no need to use other means or components, and only the circuit is divided according to the natural attenuation of the first electrolytic capacitor 11. The voltage changes, the different rectification parts are turned on, and the automatic switching of the electrolytic capacitor is realized, without manual switching by the staff, and the operation is simple.

It should be noted that FIG. 4 is only a reference waveform diagram shown by an oscilloscope, and it is not necessary to set an oscilloscope or other controllers to monitor the ripple voltage in actual circuit design.

Further, if the electrolytic capacitor is left unused for a long time, its service life will also be shortened. In this embodiment, when the second electrolytic capacitor 21 is used as a backup electrolytic capacitor, the contact of the relay is connected to the second contact b when the power is not turned on. , at the initial moment of power-on, the contact of the relay will not be switched to the first contact a immediately, and the second electrolytic capacitor 21 will be charged during the time before switching to the first contact a. In this way, each time the switching power supply 100 is charged as a backup electrolytic capacitor at the moment of power-on, it is turned off during operation, which is beneficial to the long-term storage of the second electrolytic capacitor 21 .

In some embodiments, the circuit design of the embodiments of the present invention can also be applied to technical fields other than switching power supplies that require the application of electrolytic capacitors, such as automotive industry, security industry, medical electronics, medium and large electronic equipment, etc., backup capacitors and The design of automatic switching can effectively prolong the life of the circuit where the electrolytic capacitor is located.

In describing the embodiments of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front ", "Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inside", "Outside", "Clockwise", "Counterclockwise", etc. The orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiment of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, use a specific configuration and operation, and therefore should not be construed as limiting the embodiments of the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of said features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the description of the embodiments of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a It is a detachable connection, or an integral connection; it can be mechanically connected, it can be electrically connected, or it can communicate with each other; it can be directly connected or indirectly connected through an intermediary, and it can be internal communication between two components or two components interaction relationship. Those of ordinary skill in the art can understand the specific meanings of the above terms in the embodiments of the present invention according to specific situations.

In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, and may also include the first and second features. The second features are not in direct contact but through another feature between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

The above disclosure provides many different embodiments or examples for implementing different structures of embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, the components and arrangements of specific examples are described above. Of course, they are only examples and are not intended to limit the invention. Furthermore, embodiments of the present invention may repeat reference numerals and/or reference letters in different instances, such repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. . In addition, embodiments of the present invention provide examples of various specific processes and materials, but one of ordinary skill in the art may recognize the use of other processes and/or the use of other materials.

In the description of this specification, reference to the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific examples" or "some examples" etc. Specific features, structures, materials, or features described in an embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

Any process or method descriptions in flowcharts or otherwise described herein may be understood to represent modules, segments or portions of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and the scope of preferred embodiments of the invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including substantially concurrently or in reverse order depending on the functions involved, which shall It is understood by those skilled in the art to which the embodiments of the present invention pertain.

The logic and/or steps represented in the flowcharts or otherwise described herein, for example, can be considered as a sequenced listing of executable instructions for implementing logical functions, can be embodied in any computer-readable medium, For use with instruction execution systems, devices, or devices (such as computer-based systems, systems including processing modules, or other systems that can fetch instructions from instruction execution systems, devices, or devices and execute instructions), or in conjunction with these instruction execution systems, devices or equipment used. For the purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use in or in conjunction with an instruction execution system, device or device. More specific examples (non-exhaustive list) of computer-readable media include the following: electrical connection with one or more wires (electronic device), portable computer disk case (magnetic device), random access memory (RAM), Read Only Memory (ROM), Erasable and Editable Read Only Memory (EPROM or Flash Memory), Fiber Optic Devices, and Portable Compact Disc Read Only Memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program can be printed, since the program can be read, for example, by optically scanning the paper or other medium, followed by editing, interpretation or other suitable processing if necessary. The program is processed electronically and stored in computer memory.

It should be understood that each part of the embodiments of the present invention may be implemented by hardware, software, firmware or a combination thereof. In the embodiments described above, various steps or methods may be implemented by software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or combination of the following techniques known in the art: Discrete logic circuits, ASICs with suitable combinational logic gates, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), etc.

Those of ordinary skill in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. During execution, one or a combination of the steps of the method embodiments is included.

In addition, each functional unit in each embodiment of the present invention may be integrated into one processing module, each unit may exist separately physically, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software function modules. If the integrated modules are realized in the form of software function modules and sold or used as independent products, they can also be stored in a computer-readable storage medium.

The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, and the like.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (13)

1. a kind of Switching Power Supply, which is characterized in that including：

First rectification part, first rectification part include the first electrolytic capacitor, and first rectification part is used for described first Rectification is carried out to output voltage when electrolytic capacitor is enabled；With

Second rectification part, second rectification part include the second electrolytic capacitor, and second rectification part is used for described first Rectification is carried out to the output voltage when electrolytic capacitor fails.

2. Switching Power Supply as described in claim 1, which is characterized in that the Switching Power Supply further includes gating element, the choosing Logical element is for gating first rectification part or second rectification part to enable first electrolytic capacitor or described the Two electrolytic capacitors.

3. Switching Power Supply as claimed in claim 2, which is characterized in that the gating element includes relay, the relay Including the first contact and the second contact, first electrolytic capacitor and first contact portion, second electrolytic capacitor Device is connect with second electrolytic capacitor.

4. Switching Power Supply as claimed in claim 3, which is characterized in that when first electrolytic capacitor is effective, it is described after Electric appliance is connected to when not powering on second contact, is connected to after the power is turned on first contact.

5. Switching Power Supply as claimed in claim 3, which is characterized in that when first electrolytic capacitor fails, it is described after Electric appliance holding is connected to second contact.

6. Switching Power Supply as claimed in claim 4, which is characterized in that second electrolytic capacitor is powering on instantaneous charging.

7. Switching Power Supply as claimed in claim 2, which is characterized in that first rectification part further includes first resistor, second Resistance and first switching element, the second resistance make to lead to the first switching element to enable first rectification for dividing Portion.

8. Switching Power Supply as claimed in claim 7, which is characterized in that the first switching element includes diode and three poles The anode of pipe, the base stage of the triode and the diode is connect, and the of the cathode of the diode and the second resistance One end connects, and the emitter of the triode is connect with the second end of the second resistance, the collector of the triode and choosing Logical element connection.

9. Switching Power Supply as claimed in claim 7, which is characterized in that second rectification part includes 3rd resistor, the 4th electricity Resistance and second switch element, the 4th resistance make to lead to the second switch element to enable second rectification for dividing Portion.

10. Switching Power Supply as claimed in claim 9, which is characterized in that the second switch element includes bidirectional thyristor.

11. switch element as claimed in claim 9, which is characterized in that make a reservation for when the ripple voltage of the output voltage is more than When value, the second switch element conductive is to enable second rectification part, when the ripple voltage of the output voltage is less than institute When stating predetermined value, the first switching element conducting is to enable first rectification part.

12. a kind of cooking equipment, which is characterized in that including such as claim 1-11 any one of them Switching Power Supply.

13. cooking equipment as claimed in claim 12, which is characterized in that the cooking equipment includes micro-wave oven.