CN103219897A - Switching power supply and refrigerator with same - Google Patents

Abstract

The invention discloses a switching power supply, comprising: a rectifying circuit for converting input alternating current into direct current; a filter circuit comprising: a first inductance, a second inductance, a first capacitor and a second capacitor, one end of the first inductance and the rectifier The first output end of the circuit is connected, one end of the second inductor is connected to the second output end of the rectifier circuit, one end of the first capacitor is connected to one end of the first inductor, the other end is connected to one end of the second inductor, and the second capacitor One end is connected to the other end of the first inductance, and the other end is connected to the other end of the second inductance; the first end of the switch module is connected to the other end of the first inductance; the switch control for controlling the on and off of the switch module Circuit; the first input end of the transformer is connected to the third end of the switch module, and the second input end is connected to the other end of the second inductance. The switching power supply of the invention can reduce the cost while meeting the requirements of EMI and EMC testing. The invention also proposes a refrigerator.

Description

Switching power supply and refrigerator with same

technical field

The invention relates to the technical field of power supplies, in particular to a switching power supply and a refrigerator with the switching power supply.

Background technique

In general, it can be observed from the oscilloscope that the output voltage of the rectifier circuit is not pure DC, and is very different from DC, and the waveform contains large pulsating components, which are called ripples. In order to obtain a relatively ideal DC voltage, it is necessary to use a filter circuit composed of reactive elements with energy storage functions such as capacitors and inductors to filter out the pulsating components in the output voltage of the rectifier circuit to obtain a DC voltage. Commonly used filter circuits are passive filter and active filter two categories. The main forms of passive filtering are capacitive filtering, inductive filtering, and complex filtering, among which complex filtering can include inverted L-type, LC filtering, LCπ-type filtering, and RCπ-type filtering. The main form of active filtering is active RC filtering, also known as electronic filter. The size of the pulsation component in the direct current is expressed by the pulsation coefficient, the larger the pulsation coefficient, the worse the filtering effect of the filter. Ripple coefficient (S) = the fundamental maximum value of the AC component of the output voltage / the DC component of the output voltage. For example, the pulsation coefficient of the output voltage of half-wave rectification is S=1.57, and the pulsation coefficient of the output voltage of full-wave rectification and bridge rectification is S≈0.67. For the full-wave and bridge rectifier circuits after using the C-type filter circuit, the pulsation coefficient S=1/(4(RLC/T-1), where S is the pulsation coefficient, R is the resistance value, L is the inductance, and C is Capacitance, T is period.

In addition, as shown in Figure 1, the current commonly used 12W switching power supply circuit includes: X structure capacitor 101, common mode inductor 102, rectifier filter circuit 103, switch module 104, PWM control and drive circuit 105, transformer 106, output filter 107. Sampling feedback control circuit 108 and sampling circuit 109, wherein sampling circuit 109 includes resistor R01 and resistor R02, R0L is a load, mains 220V/50Hz is input switching power supply, and the output of switching power supply supplies power to load R0L. After the voltage is rectified, it is generally filtered directly with a capacitor. When a capacitor is used for filtering, a large capacitance is required to meet the demand. However, a large-capacity capacitor has a large short-circuit current at the moment of power-on. This current has a great impact on the rectifier diode and transformer The impact is very large, and the existing 12W switching power supply meets the requirements of EMI (Electro-Magnetic Interference, electromagnetic interference) and EMC (Electro-Magnetic Compatibility, electromagnetic compatibility) tests, the common-mode inductance used and the large filter used Electrolytic capacitors are more expensive. In order to reduce the impact of large capacitors on rectifier diodes and transformers at the moment of household appliances, the general practice is to add a power NTC (Negative Temperature Coefficient, negative temperature coefficient) thermistor in front of the rectifier circuit to maintain balance. The resistance at normal temperature is very large, and the resistance value decreases rapidly as the temperature rises after power-on, which can play the role of soft start. The disadvantage of this circuit is: after power-off, within the thermal time constant, the NTC thermistor has no Returns to zero power resistance value, so not suitable for frequent starts. In addition, when the LC/LT filter is used for filtering, the circuit will often resonate with other components in the circuit at a certain frequency due to the mismatch of the filter end impedance, thus affecting the normal operation of the circuit.

Contents of the invention

The object of the present invention is to solve one of the above-mentioned technical problems at least to a certain extent.

Therefore, an object of the present invention is to provide a switching power supply, which can reduce costs while meeting the requirements of EMI and EMC testing.

Another object of the present invention is to propose a refrigerator.

In order to achieve the above object, an embodiment of the present invention proposes a switching power supply, the switching power supply includes: a rectifier circuit for converting input AC power into DC power; a filter circuit, the filter circuit includes: a first inductor and a second inductor, One end of the first inductor is connected to the first output end of the rectifier circuit, one end of the second inductor is connected to the second output end of the rectifier circuit; the first capacitor, one end of the first capacitor is connected to the first output end of the rectifier circuit. One end of the first inductance is connected, and the other end of the first capacitor is connected to one end of the second inductance; for the second capacitor, one end of the second capacitor is connected to the other end of the first inductance, so The other end of the second capacitor is connected to the other end of the second inductance; a switch module, the first end of the switch module is connected to the other end of the first inductance; used to control the on and off of the switch module An open switch control circuit, the first end of the switch control circuit is connected to the second end of the switch module, the second end of the switch control circuit is connected to the other end of the second inductor; the transformer, the The first input end of the transformer is connected to the third end of the switch module, the second input end of the transformer is connected to the other end of the second inductor, and the first output end of the transformer is the first output.

According to the switching power supply of the embodiment of the present invention, the input voltage is filtered by a filter circuit composed of two inductors and two capacitors, which can meet the output requirements of the switching power supply and the requirements for EMI detection, and does not require a common mode inductor. The structure is simpler and the cost is reduced.

Further, in one embodiment of the present invention, the above-mentioned switching power supply further includes: an X-structure capacitor for filtering the input AC power, the first input terminal and the second double-input terminal of the X-structure capacitor are respectively connected to the two AC power The input terminals are connected, the first output terminal of the X-structure capacitor is connected with the first input terminal of the rectification circuit, and the second output terminal of the X-structure capacitor is connected with the second input terminal of the rectification circuit; output filtering circuit, one end of the output filtering circuit is connected to the second output end of the transformer, and the second end of the output circuit is connected to the first output end of the transformer; a sampling circuit, the first end of the sampling circuit Connected to the third terminal of the output filter circuit, the second terminal of the sampling circuit is connected to the first output terminal of the transformer; a feedback control circuit, the first terminal of the feedback control circuit is connected to the switch control circuit The third terminal of the feedback control circuit is connected to the first output terminal of the transformer, and the third terminal of the feedback control circuit is connected to the third terminal of the sampling circuit.

Furthermore, in one embodiment of the present invention, the sampling circuit includes: a first resistor, one end of the first resistor is connected to the third end of the output filter circuit, and the other end of the first resistor is connected to The third end of the feedback control circuit is connected; a second resistor, one end of the second resistor is connected to the other end of the first resistor, and the other end of the second resistor is connected to the first output end of the transformer connected; wherein, there is a first node between the first resistor and the second resistor, and the first node is connected to the third terminal of the feedback control circuit.

In some embodiments of the present invention, the first capacitance and the second capacitance can be obtained by calculation according to the output power of the switching power supply and the ripple current input by the filter circuit.

In addition, the first inductance can be calculated according to the cutoff frequency of the filter circuit.

In a specific embodiment of the present invention, the switch module may be a triode, the emitter of the triode is connected to the other end of the first inductor, and the base of the triode is connected to the first end of the switch control circuit. terminals, and the collector of the triode is connected to the first input terminal of the transformer.

To achieve the above object, another embodiment of the present invention provides a refrigerator, which includes the switching power supply provided by the above embodiment.

According to the refrigerator of the embodiment of the present invention, by using the switching power supply described above, the cost can be reduced while meeting the requirements of the main control board of the refrigerator.

Additional aspects and advantages of the invention will be set forth in part 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 easy to understand from the following description of the embodiments in conjunction with the accompanying drawings, wherein:

Fig. 1 is the schematic block diagram of the structure of the switching power supply of prior art;

2 is a schematic block diagram of a structure of a switching power supply according to an embodiment of the present invention;

3 is a schematic block diagram of the structure of a switching power supply according to an embodiment of the present invention; and

Fig. 4 is a schematic block diagram of a refrigerator according to an 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 designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, components and arrangements of specific examples are described below. Of course, they are only examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or letters in different instances. This repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and/or arrangements discussed. In addition, various specific process and material examples are provided herein, but one of ordinary skill in the art will recognize the applicability of other processes and/or the use of other materials. Additionally, configurations described below in which a first feature is "on" a second feature may include embodiments where the first and second features are formed in direct contact, and may include additional features formed between the first and second features. For example, such that the first and second features may not be in direct contact.

In the description 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 mechanical connection or an electrical connection, or it can be two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

These and other aspects of embodiments of the invention will become apparent with reference to the following description and drawings. In these descriptions and drawings, some specific implementations in the embodiments of the present invention are specifically disclosed to represent some ways of implementing the principles of the embodiments of the present invention, but it should be understood that the scope of the embodiments of the present invention is not limited by this limit. On the contrary, the embodiments of the present invention include all changes, modifications and equivalents coming within the spirit and scope of the appended claims.

The switching power supply proposed according to the embodiment of the present invention and the refrigerator with the switching power supply will be described below with reference to the accompanying drawings.

As shown in FIG. 2 , the switching power supply of the embodiment of the present invention includes: a rectifying circuit 201 , a filtering circuit 202 , a switching module 203 , a switching control circuit 204 and a transformer 205 . Wherein, the rectifier circuit 201 converts the input alternating current into direct current. The filter circuit 202 filters the output voltage of the rectification circuit 201 .

Further, the filter circuit 202 includes: a first inductor 206 , a second inductor 207 , a first capacitor 208 and a second capacitor 209 . Wherein, one end of the first inductance 206 is connected with the first output end 53 of the rectification circuit 201, and one end of the second inductance 207 is connected with the second output end 54 of the rectification circuit 201; One end is connected, the other end of the first capacitor 208 is connected with one end of the second inductor 207; one end of the second capacitor 209 is connected with the other end of the first inductor 206, and the other end of the second capacitor 209 is connected with the other end of the second inductor 207 connected.

As shown in FIG. 2 , the first terminal 1 of the switch module 203 is connected to the other terminal of the first inductor 206 . The switch control circuit 204 is used to control the on and off of the switch module 203, the first terminal 21 of the switch control circuit 204 is connected to the second terminal 2 of the switch module 203, the second terminal 22 of the switch control circuit 204 is connected to the second inductor The other end of 207 is connected. The first input terminal 31 of the transformer 205 is connected to the third terminal 3 of the switch module 203, the second input terminal 32 of the transformer 205 is connected to the other end of the second inductor 207, and the first output terminal 33 of the transformer 205 is the first terminal of the switching power supply. an output terminal.

Further, in an embodiment of the present invention, as shown in FIG. 3 , the switching power supply further includes: an X-structure capacitor 301 , an output filter circuit 302 , a sampling circuit 303 and a feedback control circuit 304 . Wherein, the X-structure capacitor 301 filters the input AC power, the first input terminal 41 and the second input terminal 42 of the X-structure capacitor 301 are respectively connected to the two input terminals of the AC power, and the first output terminal 43 of the X-structure capacitor 301 is connected to the rectifier The first input terminal 51 of the circuit 201 is connected, and the second output terminal 44 of the X-structure capacitor 301 is connected to the second input terminal 52 of the rectification circuit 201 . The first terminal 61 of the output filter circuit 302 is connected to the second output terminal 34 of the transformer 205 , and the second terminal 62 of the output filter circuit 302 is connected to the first output terminal 33 of the transformer 205 . The first terminal 71 of the sampling circuit 303 is connected to the third terminal 63 of the output filter circuit 302 , and the second terminal 72 of the sampling circuit 303 is connected to the first output terminal 33 of the transformer 205 . The first terminal 81 of the feedback control circuit 304 is connected with the third terminal 23 of the switch control circuit 204, the second terminal 82 of the feedback control circuit 304 is connected with the first output terminal 33 of the transformer 205, and the third terminal 83 of the feedback control circuit 304 It is connected with the third terminal 73 of the sampling circuit 303 .

Furthermore, as shown in FIG. 3 , the sampling circuit 303 may include: a first resistor R1 and a second resistor R2. Wherein, one end of the first resistor R1 is connected to the third end 63 of the output filter circuit 302 , and the other end of the first resistor R1 is connected to the third end 83 of the feedback control circuit 304 . One end of the second resistor R2 is connected to the other end of the first resistor R1 , and the other end of the second resistor R2 is connected to the first output end 33 of the transformer 205 . Wherein, there is a first node 9 between the first resistor R1 and the second resistor R2 , and the first node 9 is connected to the third terminal 83 of the feedback control circuit 304 . The resistor _RL is the load, and the output of the switching power supply supplies power to the resistor _RL .

In an embodiment of the present invention, as shown in FIG. 3 , the switch module 203 may be a triode, or a device capable of realizing switching functions such as a MOS transistor or a thyristor. Wherein, the emitter of the triode is connected to the other end of the first inductor, the base of the triode is connected to the first end of the switch control circuit, and the collector of the triode is connected to the first input end of the transformer.

As shown in Figure 3, the input is 220v/50Hz AC, which is filtered by the X-structure capacitor 301, and then rectified by the rectifier circuit 201 to become a pulsating DC, and then the filter circuit 202 converts the pulsating DC into a smoother DC, and The switch control circuit 204 controls the turn-on and cut-off of the triode to generate alternating current. The alternating current is transformed by the transformer 205 to obtain the required voltage value, and then the output filter circuit 302 obtains a direct-current voltage to supply power to the load _RL . In order to make the output voltage Stable, the sampling circuit 303 is used to amplify the error by optical coupling through the feedback control circuit 304, and feed back to the switch control circuit 204. The switch control circuit 203 controls the turn-on and turn-off time (i.e., the duty cycle) of the triode through PWM, so that The output voltage of the switching power supply remains stable.

Generally, a filter capacitor can be added to the "source" or "load" end of the LC filter to change the impedance of the input end of the filter, that is, to form a π-type filter circuit, and the noise from the "source" or "load" is first After passing through the low-impedance filter capacitor circuit, it enters the LC type filter circuit. The filter circuit 202 of the switching power supply in the embodiment of the present invention consists of a first inductor 206, a first capacitor 208, and a second capacitor 209 to form a π-type filter circuit, which can simultaneously suppress noise and harmonic signals from the power supply and the circuit side, while increasing The second inductance 207 is added, and the EMI interference can be reduced through the second inductance 207, so as to meet the requirement of electromagnetic interference detection of the switching power supply. Wherein, the first inductance 206 can be calculated according to the cut-off frequency of the filter circuit 202, and the first capacitor 208 and the second capacitor 209 can be calculated according to the parameters of the designed switching power supply, such as the output power and the input ripple current of the filter circuit 202, Wherein, the calculation of the first inductance 206 , the first capacitance 208 and the second capacitance 209 is the prior art, and will not be repeated here. Then, only need to select the appropriate parameters of the second inductor 207 and the Y capacitor of the transformer 205, the EMI interference of the circuit can be suppressed to meet the requirements of the switching power supply. In addition, the filter circuit 202 uses two capacitors and two inductors to make its input and output low impedance. The insertion loss characteristics of the filter circuit 202 are due to the C-type and LC-type, where the insertion loss refers to the transmission system. The loss of load power due to the insertion of components or devices, insertion loss can be expressed as the power received on the load before the component or device is inserted and the power received on the same load after insertion (in decibels) ratio. In the embodiment of the present invention, the parameters of the filter circuit 202 can be selected according to the specific circuit, so as to realize the output requirement of the switching power supply and the requirement of suppressing EMI.

In summary, according to the switching power supply of the embodiment of the present invention, the input voltage is filtered by a filter circuit composed of two inductors and two capacitors, which can meet the output requirements of the switching power supply and the requirements for EMI detection, and does not require common-mode inductors, reducing costs.

A refrigerator according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 4 , the refrigerator 401 of the embodiment of the present invention includes the switching power supply 402 of the above embodiment.

According to the refrigerator of the embodiment of the present invention, by using the switching power supply described above, the cost can be reduced while meeting the requirements of the main control board of the refrigerator.

Each functional unit in each embodiment of the present invention may be integrated into one processing module, or each unit may physically exist separately, 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.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is 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 specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (7)

1. a Switching Power Supply is characterized in that, comprising:

The alternating current of input is converted into galvanic rectification circuit;

Filter circuit, described filter circuit comprises:

First inductance and second inductance, an end of described first inductance links to each other with first output of described rectification circuit, and an end of described second inductance links to each other with second output of described rectification circuit;

First electric capacity, an end of described first electric capacity links to each other with an end of described first inductance, and the other end of described first electric capacity links to each other with an end of described second inductance;

Second electric capacity, an end of described second electric capacity links to each other with the other end of described first inductance, and the other end of described second electric capacity links to each other with the other end of described second inductance;

Switch module, first end of described switch module links to each other with the other end of described first inductance;

The ON-OFF control circuit that is used for the conducting and the disconnection of control switch module, first end of described ON-OFF control circuit links to each other with second end of described switch module, and second end of described ON-OFF control circuit links to each other with the other end of described second inductance;

Transformer, the first input end of described transformer links to each other with the 3rd end of described switch module, and second input of described transformer links to each other with the other end of described second inductance, and first output of described transformer is first output of described Switching Power Supply.

2. Switching Power Supply as claimed in claim 1 is characterized in that, also comprises:

The input AC electricity is carried out the X structure capacitive of filtering, the first input end of described X structure capacitive links to each other with two inputs of alternating current respectively with second input, first output of described X structure capacitive links to each other with the first input end of described rectification circuit, and second output of described X structure capacitive links to each other with second input of described rectification circuit;

Output filter circuit, first end of described output filter circuit links to each other with second output of described transformer, and second end of described output filter circuit links to each other with first output of described transformer;

Sample circuit, first end of described sample circuit links to each other with the 3rd end of described output filter circuit, and second end of described sample circuit links to each other with first output of described transformer;

Feedback control circuit, first end of described feedback control circuit links to each other with the 3rd end of described ON-OFF control circuit, second end of described feedback control circuit links to each other with first output of described transformer, and the 3rd end of described feedback control circuit links to each other with the 3rd end of described sample circuit.

3. Switching Power Supply as claimed in claim 2 is characterized in that, described sample circuit comprises:

First resistance, an end of described first resistance links to each other with the 3rd end of described output filter circuit, and the other end of described first resistance links to each other with the 3rd end of described feedback control circuit;

Second resistance, an end of described second resistance links to each other with the other end of described first resistance, and the other end of described second resistance links to each other with first output of described transformer;

Wherein, have first node between described first resistance and described second resistance, described first node links to each other with the 3rd end of described feedback control circuit.

4. Switching Power Supply as claimed in claim 1 is characterized in that, described first electric capacity and described second electric capacity calculate acquisition according to the power output of described Switching Power Supply and the ripple current of described filter circuit input.

5. Switching Power Supply as claimed in claim 1 is characterized in that, described first inductance calculates acquisition according to the cut-off frequency of described filter circuit.

6. Switching Power Supply as claimed in claim 1, it is characterized in that, described switch module is a triode, the emitter of described triode links to each other with the other end of described first inductance, the base stage of described triode links to each other with first end of described ON-OFF control circuit, and the collector electrode of described triode links to each other with the first input end of described transformer.

7. a refrigerator is characterized in that, comprises each described Switching Power Supply of claim 1～6.

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