CN201430528Y

CN201430528Y - Power supply filter circuit

Info

Publication number: CN201430528Y
Application number: CN2009200693620U
Authority: CN
Inventors: 钱理强; 刘士豪
Original assignee: Inventec Pudong Technology Corp; Inventec Corp
Current assignee: Inventec Pudong Technology Corp; Inventec Corp
Priority date: 2009-03-25
Filing date: 2009-03-25
Publication date: 2010-03-24
Anticipated expiration: 2019-03-25

Abstract

The utility model discloses a power supply filter circuit which comprises a first capacitor, a first common mode inductor, a second capacitor, a second common mode inductor, a third capacitor and a fourth capacitor. The power supply filter circuit filters off the conducted interference of the switching power supply through two stages of common mode inductors. Accordingly, the electromagnetic interference can be effectively prevented and treated, and the stability degree of the power supply is improved.

Description

Electric source filter circuit

Technical field

The utility model relates to a kind of filter circuit, and particularly relevant for a kind of filter circuit that can suppress the electromagnetic interference of Switching Power Supply.

Background technology

Electronic product now all with meet miniaturization, high-performance, high accuracy, high reliability, and high degree of reaction etc. be target, make the distribution density of circuit element too high, the volume of circuit dwindles greatly, it is more exquisite that yet circuit becomes, then having more element squeezes in the middle of very little space, increased the chance of disturbing, wherein with electromagnetic interference (Electromagnetic interference, EMI) and noise make us most feeling the puzzlement.The inhibition object of EMI mainly is divided into radiativity (Radiated) and conductibility (Conducted) electromagnetic interference.Radiativity EMI is directly via the open space transmission, need be via any transmission medium.And conductibility EMI, it transmits noise via power lead, can disturb each other via power line so be connected the EMI that electric device produced of same electric power system.

Switching Power Supply generally all adopts pulse-width modulation, and (pulse width modulation, PWM) technology are characterized in frequency height, efficient height, power density height.Yet, because its switching device is operated in the high frequency on off operating mode, the fast transient process of high frequency itself is exactly an electromagnetic disturbance (electromagnetic disturbance, EMD) source, the electromagnetic interference signal that it produces has very wide frequency range, and certain amplitude is arranged again.If this power supply is directly used in digital device, then the electromagnetic interference signal of equipment generation can become stronger and complicated.

Fig. 1 illustrates the filter circuit that known technology is used for suppressing EMI.Filter circuit 100 is combined by differential mode filter circuit 110 and common mode filtering circuit 120.In theory, filter circuit 100 should suppress common-mode noise and differential mode noise simultaneously.But be to use the server product of this filter circuit, can't be in the limit value of standard code the EMI control of Electric potentials of Switching Power Supply.

For a long time, the EMI problem of Switching Power Supply is electronic equipment and system's big blind spot in design always, and this is that the factor that involves because of electromagnetic interference is various, and the required wider relation of professional knowledge when handling.Because the high competition of scientific and technological industry, the life cycle of new product is shorter and shorter, makes us have to seek the quick settling mode of electromagnetic interference problem, shortens the research and development time of product, in the hope of seizing the first market opportunities.

The utility model content

The utility model provides a kind of electric source filter circuit, suppresses the electromagnetic interference of Switching Power Supply whereby, and output improves stability of power supply through filtered AC power.

The utility model proposes a kind of electric source filter circuit, it has one first power input, a second source input, one first power output end, reaches a second source output.Described electric source filter circuit comprises: one first electric capacity, and its first end couples described first power input, and its second end couples described second source input; One first common mode inductance, it has one first coil, reaches one second coil, and first end of described first coil couples described first power input, and first end of described second coil couples described second source input; One second electric capacity, its first end couples second end of described first coil, and its second end couples second end of described second coil; One second common mode inductance, it has a tertiary coil, reaches one the 4th coil, first end of described tertiary coil couples first end of described second electric capacity, second end of described tertiary coil couples described first power output end, first end of described the 4th coil couples second end of described second electric capacity, and second end of described the 4th coil couples described second source output; One the 3rd electric capacity, its first end couples described first power output end, and its second end couples an earthing potential; And one the 4th electric capacity, its first end couples described second source output, and its second end couples described earthing potential.Wherein, described first power input and described second source input receive an AC power, and are exported through filtered AC power by described first power output end and described second source output.

The utility model common mode inductance with two-stage on electric source filter circuit comes filtering, suppresses the electromagnetic interference of Switching Power Supply effectively.Thus, prevent and treat electromagnetic interference effectively, improve stability of power supply.

Description of drawings

For above-mentioned purpose of the present utility model, feature and advantage can be become apparent, below in conjunction with accompanying drawing embodiment of the present utility model is elaborated, wherein:

Fig. 1 illustrates the electric source filter circuit of known technology.

Fig. 2 illustrates the electric source filter circuit of the utility model one embodiment.

Fig. 3 illustrates with the conduction transmission test of traditional filter circuit 100 figure as a result.

Fig. 4 illustrates with the conduction transmission test of the electric source filter circuit 200 of Fig. 2 figure as a result.

The main element symbol description:

100: filter circuit

200: electric source filter circuit

ACIN1, ACIN2: power input

ACOUT1, ACOUT2: power output end

CX1, CX2, CY1, CY2: electric capacity

GND: earthing potential

LY1, LY2: common mode inductance

T1: first end of first coil

T2: second end of first coil

T3: first end of second coil

T4: second end of second coil

T5: first end of tertiary coil

T6: second end of tertiary coil

T7: first end of the 4th coil

T8: second end of the 4th coil

Embodiment

(Electromagnetic interference mainly is because the transsexual element of Switching Power Supply inscribe produces when making the high speed current switching EMI) to the conductibility electromagnetic interference.Disturb other common operate as normal of using the device on the same electric power network for the high frequency instantaneous current signal that suppresses to switch in the Switching Power Supply enters electric power network (power net) via power line, in Switching Power Supply, must add a filter circuit.

When the harmonic wave current potential of Switching Power Supply at frequency range 0.15～30MHz and when showing on the power line, be referred to as " conducted interference ".The conducted interference of Switching Power Supply comprises common-mode noise and differential mode noise, and Switching Power Supply is no exception.Common mode disturbances (common mode interference) is because the potential difference between current and the earth produces, and is characterized in that two noise voltages on the line are in the same way idiostatic; Differential mode interference then is because the potential difference between the current produces, and is characterized in that two noise voltages on the line are idiostatic reverse.Usually, the interference that Switching Power Supply produced is based on common mode disturbances.

Fig. 2 illustrates the electric source filter circuit of the utility model one embodiment.Please refer to Fig. 2.Consider interference that Switching Power Supply produces based on common mode disturbances, present embodiment removes the differential mode filtering part in the known circuits when the design filter circuit, increase one-level common mode filtering inductance again.

Electric source filter circuit 200 has power input ACIN1, power input ACIN2, power output end ACOUT1, reaches power output end ACOUT2.Electric source filter circuit 200 comprises capacitor C X1, CX2, CY1 and CY2 and common mode inductance LY1 and LY2.

Capacitor C X1 first end couples power input ACIN1.Second end of capacitor C X1 couples power input ACIN2.Common mode inductance (common mode choke) or be called common mode choke LY1 and have first coil, and second coil, wherein first coil and second coil have identical inductance value, identical impedance and symmetric geometry.The first end T1 of first coil couples power input ACIN1.The first end T3 of second coil couples power input ACIN2.

First end of capacitor C X2 couples the second end T2 of first coil.Second end of capacitor C X2 couples the second end T4 of second coil.

Common mode inductance LY2 has tertiary coil, and the 4th coil, and wherein tertiary coil and the 4th coil have identical inductance value, identical impedance and symmetric geometry.First end of the first end T5 coupling capacitance CX2 of tertiary coil.The second end T6 of tertiary coil couples power output end ACOUT1.Second end of the first end T7 coupling capacitance CX2 of the 4th coil.The second end T8 of the 4th coil couples power output end ACOUT2.

First end of capacitor C Y1 couples power output end ACOUT1.Second end of capacitor C Y1 couples earthing potential GND.First end of capacitor C Y2 couples power output end ACOUT2.Second end of capacitor C Y2 couples earthing potential GND.Wherein, power input ACIN1, ACIN2 receive AC power, and are exported through filtered AC power by power output end ACOUT1, ACOUT2.

The operation principle of electric source filter circuit 200 is the source impedance mismatch of the impedance of electric source filter circuit 200 and input.Severe more when mismatch, then the decay of Shi Xianing is unreasonable thinks, the insertion loss characteristic that obtains is just good more.That is to say that if the source impedance (noise source internal resistance) of input is low-impedance, then the input impedance of the electric source filter circuit 200 of butt joint is high impedance with it.What deserves to be mentioned is that the electric source filter circuit 200 of present embodiment has preferable fade performance for the EMI signal of Switching Power Supply.

For the effect of the electric source filter circuit 200 that highlights present embodiment, will conduct the transmission test result and represent with graphic.Fig. 3 and Fig. 4 illustrate the conduction transmission test done with the electric source filter circuit 200 of traditional filter circuit 100, present embodiment figure as a result respectively.The longitudinal axis in Fig. 3 and Fig. 4 is represented noise current potential (dB μ V), and transverse axis is represented frequency (MHz), and frequency range is 0.15～30MHz.The limit value that two conduction transmission tests are also respectively arranged in Fig. 3 and Fig. 4, the peak that from top to bottom is as the criterion respectively (Quasi-peak, QP) limit value and average (Average, AV) limit value.Learn that from the test result of Fig. 4 and Fig. 3 electric source filter circuit 200, and has also fallen much at the peak value of frequency 28MHz compared with electric source filter circuit 100 about 6dB that descended in the QP of frequency 400kHz value.It can be said that bright electric source filter circuit 200 has played considerable filter action.

Those skilled in the art should understand, and can do a little adjustment at the physical circuit of the foregoing description.In actual use, because the composition of the common mode that equipment produced is different, can suitably increase or reduce the numerical value of filter element.Must guarantee that ground connection is good when electric source filter circuit 200 is installed, and power input and power output end to isolate well, just can play the effect of preferable filtering.

The utility model suppresses the electromagnetic interference of Switching Power Supply effectively because electric source filter circuit uses the common mode inductance of two-stage to come filtering.Thus, can prevent and treat electromagnetic interference effectively, and improve stability of power supply.

Though the utility model discloses as above with preferred embodiment; right its is not in order to limit the utility model; any those skilled in the art; in not breaking away from spirit and scope of the present utility model; when doing a little modification and perfect, therefore protection range of the present utility model is worked as with being as the criterion that claims were defined.

Claims

1. electric source filter circuit, it has one first power input, a second source input, one first power output end, an and second source output, it is characterized in that described electric source filter circuit comprises:

One first electric capacity, its first end couples described first power input, and its second end couples described second source input;

One first common mode inductance, it has one first coil, reaches one second coil, and first end of described first coil couples described first power input, and first end of described second coil couples described second source input;

One second electric capacity, its first end couples second end of described first coil, and its second end couples second end of described second coil;

One second common mode inductance, it has a tertiary coil, reaches one the 4th coil, first end of described tertiary coil couples first end of described second electric capacity, second end of described tertiary coil couples described first power output end, first end of described the 4th coil couples second end of described second electric capacity, and second end of described the 4th coil couples described second source output;

One the 3rd electric capacity, its first end couples described first power output end, and its second end couples an earthing potential; And

One the 4th electric capacity, its first end couples described second source output, and its second end couples described earthing potential.