阅读说明：本技术 一种用于电源适配器的直流emi滤波器结构 (Direct current EMI filter structure for power adapter ) 是由 包智杰 于 2019-11-11 设计创作，主要内容包括：本发明公开了一种用于电源适配器的直流EMI滤波器结构,包括整流模块、滤波模块和变压模块,所述整流模块、所述滤波模块和所述变压模块依次电性连接,所述滤波模块包括第一电容和扼流圈,所述第一电容与所述整流模块并联,且与所述扼流圈的第一端和第二端并联,所述扼流圈的第三端和第四端与所述变压模块并联,达到在直流侧进行滤波,占用空间小,实现减少滤波器的体积,同时减少功率损耗的目的。(The invention discloses a direct current EMI filter structure for a power adapter, which comprises a rectifying module, a filtering module and a voltage transformation module, wherein the rectifying module, the filtering module and the voltage transformation module are sequentially and electrically connected, the filtering module comprises a first capacitor and a choke coil, the first capacitor is connected with the rectifying module in parallel and is connected with a first end and a second end of the choke coil in parallel, and a third end and a fourth end of the choke coil are connected with the voltage transformation module in parallel, so that the purposes of filtering on a direct current side, occupying small space, reducing the size of a filter and reducing power loss are achieved.)

1. A DC EMI filter structure for a power adapter,

including rectifier module, filtering module and vary voltage module, rectifier module the filtering module with vary voltage module is electric connection in proper order, filtering module includes first electric capacity and choke, first electric capacity with rectifier module is parallelly connected, and with the first end and the second end of choke are parallelly connected, the third end and the fourth end of choke with vary voltage module is parallelly connected.

2. The dc EMI filter structure for a power adapter as recited in claim 1, wherein said rectifying module comprises a first diode, a second diode, a third diode, and a fourth diode, an anode of said first diode being connected to an anode of a power source and a cathode of said second diode, a cathode of said first diode being connected to a cathode of said third diode and a first end of a first capacitor, an anode of said fourth diode being connected to an anode of said second diode and a second end of said first capacitor, and a cathode of said fourth diode being connected to an anode of said third diode and a cathode of a power source.

3. The DC EMI filter structure for power adapter as set forth in claim 1, wherein said transforming module further comprises a transformer, a third capacitor, a first resistor, a fifth diode, a field effect transistor, a sixth diode, a fourth capacitor, a second resistor and a fifth capacitor, said transformer is provided with a primary winding and a secondary winding, a first end of said primary winding is connected to a third end of said choke coil, a first end of said third capacitor and a first end of said first resistor, a cathode of said fifth diode is connected to a second end of said third capacitor and a second end of said first resistor, a second end of said primary winding is connected to an anode of said fifth diode and a drain of said field effect transistor, a first end of said secondary winding is connected to an anode of said sixth diode, a cathode of said sixth diode is connected to a first end of said fourth capacitor and a first end of said second resistor, the second end of the secondary winding is connected with the second end of the fourth capacitor, the second end of the second resistor and the first end of the fifth capacitor, and the source electrode of the field effect transistor is connected with the second end of the fifth capacitor and the fourth end of the choke coil.

4. The direct current EMI filter structure for a power adapter as recited in claim 3, wherein the filter module further comprises a first inductor and a second capacitor, a first terminal of the first inductor being connected to the third terminal of the choke, a second terminal of the first inductor being connected to a first terminal of the second capacitor and a first terminal of the third capacitor, a second terminal of the second capacitor being connected to the fourth terminal of the choke and the source of the field effect transistor.

5. The direct current EMI filter structure for a power adapter as recited in claim 3, wherein the filter module further comprises a first inductor and a second capacitor, a first terminal of the first inductor being connected to a first terminal of the first capacitor, a second terminal of the first inductor being connected to a first terminal of the choke, a first terminal of the second capacitor being connected to a third terminal of the choke, and a second terminal of the second capacitor being connected to a fourth terminal of the choke and the source of the field effect transistor.

6. The direct current EMI filter structure for a power adapter as recited in claim 3 wherein said filter module further comprises a first inductor, a first terminal of said first inductor being connected to a third terminal of said choke, a second terminal of said first inductor being connected to a first terminal of said third capacitor.

7. The direct current EMI filter structure for a power adapter as recited in claim 3, wherein the filter module further comprises a first inductor and a second capacitor, a first terminal of the first inductor being connected to the third terminal of the choke coil and a first terminal of the second capacitor, a second terminal of the first inductor being connected to a first terminal of a third capacitor, and a second terminal of the second capacitor being connected to the fourth terminal of the choke coil and the source of the field effect transistor.

Technical Field

The invention relates to the technical field of filters, in particular to a direct-current EMI filter structure for a power adapter.

Background

The demand for high power density power adapters in the market is rapidly increasing, which requires smaller volume designs. The permissible releasable power loss is correspondingly smaller for smaller volumes. This requires us to design smaller devices to achieve higher efficiency.

The filter inside the power adapter is often too bulky, and therefore, a filter that reduces power loss and size is urgently needed.

Disclosure of Invention

The invention aims to provide a direct current EMI filter structure for a power adapter, and aims to solve the problem that a filter for reducing power loss and size is urgently needed.

In order to achieve the above object, the present invention provides a dc EMI filter structure for a power adapter, including a rectifying module, a filtering module and a transforming module, where the rectifying module, the filtering module and the transforming module are sequentially electrically connected, the filtering module includes a first capacitor and a choke coil, the first capacitor is connected in parallel with the rectifying module and connected in parallel with a first end and a second end of the choke coil, and a third end and a fourth end of the choke coil are connected in parallel with the transforming module.

The rectifying module comprises a first diode, a second diode, a third diode and a fourth diode, wherein the anode of the first diode is connected with the anode of a power supply and the cathode of the second diode, the cathode of the first diode is connected with the cathode of the third diode and the first end of a first capacitor, the anode of the fourth diode is connected with the anode of the second diode and the second end of the first capacitor, and the cathode of the fourth diode is connected with the anode of the third diode and the cathode of the power supply.

The transformer module further comprises a transformer, a third capacitor, a first resistor, a fifth diode, a field effect transistor, a sixth diode, a fourth capacitor, a second resistor and a fifth capacitor, wherein a primary winding and a secondary winding are arranged on the transformer, a first end of the primary winding is connected with a third end of the choke coil, a first end of the third capacitor and a first end of the first resistor, a cathode of the fifth diode is connected with a second end of the third capacitor and a second end of the first resistor, a second end of the primary winding is connected with an anode of the fifth diode and a drain electrode of the field effect transistor, a first end of the secondary winding is connected with an anode of the sixth diode, a cathode of the sixth diode is connected with a first end of the fourth capacitor and a first end of the second resistor, and a second end of the secondary winding is connected with a second end of the fourth capacitor, The second end of the second resistor is connected with the first end of the fifth capacitor, and the source electrode of the field effect transistor is connected with the second end of the fifth capacitor and the fourth end of the choke coil.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the third end of the choke coil, the second end of the first inductor is connected with the first end of the second capacitor and the first end of the third capacitor, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the first end of the first capacitor, the second end of the first inductor is connected with the first end of the choke coil, the first end of the second capacitor is connected with the third end of the choke coil, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

The filter module further comprises a first inductor, wherein a first end of the first inductor is connected with a third end of the choke coil, and a second end of the first inductor is connected with a first end of the third capacitor.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the third end of the choke coil and the first end of the second capacitor, the second end of the first inductor is connected with the first end of the third capacitor, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

According to the direct current EMI filter structure for the power adapter, the rectification module, the filtering module and the transformation module are electrically connected in sequence, the first capacitor is connected with the rectification module in parallel and connected with the first end and the second end of the choke coil in parallel, the third end and the fourth end of the choke coil are connected with the transformation module in parallel, the first capacitor and the choke coil are placed on the direct current side, the size of the direct current bus filter is far smaller than that of an alternating current line filter, the size of the adapter is reduced, and meanwhile power loss is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a circuit schematic of a first embodiment of the present invention;

FIG. 2 is a circuit schematic of a second embodiment of the present invention;

FIG. 3 is a circuit schematic of a third embodiment of the present invention;

FIG. 4 is a circuit schematic of a fourth embodiment of the present invention;

FIG. 5 is a comparison graph of the inductor current waveform of the choke;

FIG. 6 is a graph comparing filter size for the same noise attenuation;

in the figure: the transformer comprises a 10-rectifying module, a 20-filtering module, a 30-transforming module, a D1-first diode, a D2-second diode, a D3-third diode, a D4-fourth diode, a C1-first capacitor, a CM-choke coil, a C2-second capacitor, an L1-first inductor, a C3-third capacitor, a R1-first resistor, a D5-fifth diode, a T1-transformer, a Q1-field effect transistor, a D6-sixth diode, a C4-fourth capacitor, a C5-fifth capacitor and a R2-second resistor.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

Fig. 1 is a schematic circuit diagram of a dc EMI filter structure for a power adapter according to a first embodiment of the present invention. The direct-current EMI filter structure for the power adapter comprises a rectifying module, a filtering module and a transformation module, wherein the rectifying module, the filtering module and the transformation module are electrically connected in sequence, the filtering module comprises a first capacitor and a choke coil, the first capacitor is connected with the rectifying module in parallel and connected with a first end and a second end of the choke coil in parallel, and a third end and a fourth end of the choke coil are connected with the transformation module in parallel.

The rectifying module comprises a first diode, a second diode, a third diode and a fourth diode, wherein the anode of the first diode is connected with the anode of a power supply and the cathode of the second diode, the cathode of the first diode is connected with the cathode of the third diode and the first end of a first capacitor, the anode of the fourth diode is connected with the anode of the second diode and the second end of the first capacitor, and the cathode of the fourth diode is connected with the anode of the third diode and the cathode of the power supply.

The voltage transformation module further comprises a transformer, a third capacitor, a first resistor, a fifth diode, a field effect transistor, a sixth diode, a fourth capacitor, a second resistor and a fifth capacitor, wherein a primary winding and a secondary winding are arranged on the transformer, the first end of the primary winding is connected with the third end of the choke coil, the first end of the third capacitor and the first end of the first resistor, the cathode of the fifth diode is connected with the second end of the third capacitor and the second end of the first resistor, the second end of the primary winding is connected with the anode of the fifth diode and the drain electrode of the field effect transistor, the first end of the secondary winding is connected with the anode of the sixth diode, the cathode of the sixth diode is connected with the first end of the fourth capacitor and the first end of the second resistor, and the second end of the secondary winding is connected with the second end of the fourth capacitor, The second end of the second resistor is connected with the first end of the fifth capacitor, and the source electrode of the field effect transistor is connected with the second end of the fifth capacitor and the fourth end of the choke coil.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the third end of the choke coil, the second end of the first inductor is connected with the first end of the second capacitor and the first end of the third capacitor, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

In this embodiment, the rectifying module is configured to rectify a circuit on an ac side, and the first diode, the second diode, the third diode, and the fourth diode form a rectifying bridge according to a principle of unidirectional conduction of diodes, so as to convert ac power into dc power. The third capacitor and the first resistor are connected in parallel at two ends of the primary winding, a direct current signal or a low-frequency signal is difficult to pass, an alternating current signal or a high-frequency signal is easy to pass, the filtering effect is achieved, meanwhile, the fifth diode is connected in series, the fifth diode allows current to pass in a single direction and is blocked in the reverse direction, the third capacitor is used for absorbing energy and restraining voltage spikes, the first resistor is used for consuming energy and weakening the oscillation process, and the fifth diode is used for preventing the energy absorbed by the third capacitor from reversely charging parasitic inductance to generate resonance, so that the oscillation of voltage can be effectively restrained. The transformer is a device for changing alternating voltage by utilizing the principle of electromagnetic induction, and realizes voltage conversion according to circuit requirements. The fourth capacitor and the second resistor are connected in parallel and are connected in series with the sixth diode, the fourth capacitor is used for absorbing energy and restraining voltage spikes, the second resistor is used for consuming energy and weakening an oscillation process, and the sixth diode is used for preventing the parasitic inductor from being charged reversely by the energy absorbed by the fourth capacitor to generate resonance, so that voltage oscillation can be effectively restrained, and a filtering effect is achieved. The field effect transistor is a unipolar transistor which is also conductive by the participation of majority carriers, belongs to a voltage control type semiconductor device, can be used for amplifying current, and has the advantages of high input resistance, low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown phenomenon and wide safe working area. The fifth capacitor plays a role in resisting interference and delaying time. Conventional power adapters have differences in order to reduce common mode noiseTwo common mode chokes of the inductor are respectively positioned on the alternating current side, namely in front of the rectifying module, and are used for low-frequency and high-frequency common mode noise attenuation, and since the alternating current input current usually has a very high peak value due to the operation of a diode bridge, a large-size magnetic core is required to be used for avoiding saturation; meanwhile, in order to reduce differential mode noise, a capacitor is applied between the line and the neutral line in the conventional power adapter, the capacitor is a film capacitor, and leakage inductance of the choke coil is applied as common mode inductance. Most of the volume of the conventional power adapter is occupied by large-sized capacitors and chokes, for example, one of the capacitors has an area of 108mm²The volume of the material is 1296mm³(ii) a The area of the other capacitor is 60mm²Volume 660mm³(ii) a The area of the choke coil is 293mm²3550mm in volume³(ii) a Total area of 461mm²The total volume is 5506mm³。

The first capacitor, the choke coil, the first inductor and the second capacitor of the dc EMI filter structure for a power adapter are placed on the dc side, that is, after the rectifier module, since the value of the choke coil is much smaller than that of the capacitor of a conventional power adapter, the current ripple on the ac side mainly flows through the first capacitor, and since the switching current ripple mainly flows through the second capacitor due to the presence of the first inductor, the current flowing through the choke coil is almost a constant dc component with a small peak value, which means that it does not saturate the core, and fig. 5 is a comparison graph of the choke coil inductance current waveform. Therefore, a core with a much smaller size than the ac line filter can be used, and the second capacitor is a ceramic capacitor, which has the same capacitance value and much smaller volume than the film capacitor in the conventional power adapter, and fig. 6 is a comparison graph of the size of the filter under the same noise attenuation condition, in which the size of the dc bus filter is much smaller than the ac line filter, the occupied area is reduced by 75%, and the volume is reduced by 91%. Meanwhile, the effective value of the current on the alternating current side is generally far greater than that on the direct current side, so that the same filter inductor can reduce a lot of power loss on the direct current side, the heat dissipation of the adapter and the temperature rise of a machine shell are facilitated, a small filter needs a small magnetic core material and a small copper wire, the cost is correspondingly reduced, and meanwhile, the filtering is not influenced.

Fig. 2 is a schematic circuit diagram of a dc EMI filter structure for a power adapter according to a second embodiment of the present invention. The direct-current EMI filter structure for the power adapter comprises a rectifying module, a filtering module and a transformation module, wherein the rectifying module, the filtering module and the transformation module are electrically connected in sequence, the filtering module comprises a first capacitor and a choke coil, the first capacitor is connected with the rectifying module in parallel and connected with a first end and a second end of the choke coil in parallel, and a third end and a fourth end of the choke coil are connected with the transformation module in parallel.

The rectifying module and the transforming module have the same structural functions as those of the first embodiment, and are not described herein again.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the first end of the first capacitor, the second end of the first inductor is connected with the first end of the choke coil, the first end of the second capacitor is connected with the third end of the choke coil, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

In this embodiment, the first capacitor, the first inductor, the choke coil and the second capacitor are placed on the dc side, that is, after the rectifier module, the current ripple on the ac side mainly flows through the first capacitor, and the switching current ripple mainly flows through the second capacitor due to the presence of the first inductor, so that the current flowing through the choke coil is almost a constant dc component, and the peak value is small, which means that it does not saturate the magnetic core, and a magnetic core with a much smaller size compared with an ac line filter can be used, and furthermore, the second capacitor is a ceramic capacitor, and has the same capacitance value and a much smaller volume than the thin film capacitor in the conventional power adapter, and the effective value of the current on the ac side is generally much larger than that on the dc side, so that the same filter inductor reduces much power loss on the dc side, the adapter is favorable for heat dissipation of the adapter and temperature rise of the shell, the filter is small, small magnetic core materials and small copper wires are needed, the cost is correspondingly reduced, and meanwhile, the filtering is not influenced.

Fig. 3 is a schematic circuit diagram of a dc EMI filter structure for a power adapter according to a third embodiment of the present invention. The direct-current EMI filter structure for the power adapter comprises a rectifying module, a filtering module and a transformation module, wherein the rectifying module, the filtering module and the transformation module are electrically connected in sequence, the filtering module comprises a first capacitor and a choke coil, the first capacitor is connected with the rectifying module in parallel and connected with a first end and a second end of the choke coil in parallel, and a third end and a fourth end of the choke coil are connected with the transformation module in parallel.

The rectifying module and the transforming module have the same structural functions as those of the first embodiment, and are not described herein again.

The filter module further comprises a first inductor, wherein a first end of the first inductor is connected with a third end of the choke coil, and a second end of the first inductor is connected with a first end of the third capacitor.

In this embodiment, the first capacitor, the first inductor and the choke coil are placed on the dc side, that is, after the rectifier module, the current ripple on the ac side mainly flows through the first capacitor, and because of the existence of the first inductor, the current flowing through the choke coil is almost a constant dc component, and the peak value is small, which means that it does not saturate the magnetic core, and a magnetic core with a much smaller size compared to an ac line filter can be used, and meanwhile, the effective value of the current on the ac side is generally much larger than the effective value on the dc side, so that with the same filter inductor, much power loss is reduced on the dc side, which is beneficial to the heat dissipation of the adapter and the temperature rise of the chassis, and the small filter requires a small magnetic core material and a small copper wire, and the cost is correspondingly reduced, and has no influence on the filtering.

Fig. 4 is a schematic circuit diagram of a dc EMI filter structure for a power adapter according to a fourth embodiment of the present invention. The direct-current EMI filter structure for the power adapter comprises a rectifying module, a filtering module and a transformation module, wherein the rectifying module, the filtering module and the transformation module are electrically connected in sequence, the filtering module comprises a first capacitor and a choke coil, the first capacitor is connected with the rectifying module in parallel and connected with a first end and a second end of the choke coil in parallel, and a third end and a fourth end of the choke coil are connected with the transformation module in parallel.

The rectifying module and the transforming module have the same structural functions as those of the first embodiment, and are not described herein again.

The filter module further comprises a first inductor and a second capacitor, wherein the first end of the first inductor is connected with the third end of the choke coil and the first end of the second capacitor, the second end of the first inductor is connected with the first end of the third capacitor, and the second end of the second capacitor is connected with the fourth end of the choke coil and the source electrode of the field effect transistor.

In this embodiment, the first capacitor, the first inductor, the choke coil and the second capacitor are placed on the dc side, that is, after the rectifier module, the current ripple on the ac side mainly flows through the first capacitor, and the switching current ripple mainly flows through the second capacitor due to the presence of the first inductor, so that the current flowing through the choke coil is almost a constant dc component with a small peak value, which means that it does not saturate the magnetic core, and a magnetic core with a much smaller size compared to an ac line filter can be used, and further, the second capacitor is a ceramic capacitor, and has the same capacitance value compared to a thin film capacitor in a conventional power adapter, the volume is much smaller than that of the thin film capacitor, and the effective value of the current on the ac side is generally much larger than that on the dc side, so that the same filter inductor, will reduce a lot of power losses at the direct current side, be favorable to adapter heat dissipation and casing temperature rise, little wave filter needs little magnetic core material and little copper line, and the cost also reduces correspondingly, also does not have the influence to the filtering simultaneously.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

According to the direct current EMI filter structure for the power adapter, the rectification module, the filtering module and the transformation module are electrically connected in sequence, the first capacitor is connected with the rectification module in parallel and connected with the first end and the second end of the choke coil in parallel, the third end and the fourth end of the choke coil are connected with the transformation module in parallel, the first capacitor and the choke coil are placed on the direct current side, the size of the direct current bus filter is far smaller than that of an alternating current line filter, the size of the adapter is reduced, and meanwhile power loss is reduced.