CN204905867U - Filter of high frequency electric sword power - Google Patents

Abstract

The utility model provides a filter of high frequency electric sword power, connects on alternating current power supply, and this alternating current power supply is equipped with live wire, zero line and ground wire, its characterized in that: the filter including the X electric capacity that is used for eliminating the differential mode interference, be used for eliminating two Y electric capacity of common mode interference and be used for the common mode inductance of the inside and external interference of isolation equipment, X electric capacity connects between live wire and the zero line, common mode inductance connects between live wire and the zero line, two Y capacitance connection are in after the common mode inductance and respectively and connect between live wire and the ground wire and between zero line and the ground wire. The utility model discloses the conducted disturbance of restriction radio frequency field response that can be fine in high frequency operation equipment to medical electrical equipment's electromagnetic compatibility requirement is reached, all kinds of high frequency operation equipment can be be arranged in.

Description

The filter of electric knife power supply

Technical field

The utility model relates to a kind of filter circuit, particularly relates to a kind of filter of electric knife power supply, belongs to medical electronics technique with the apparatus field.

Background technology

As everyone knows, medical electrical equipment not only self can launch electromagnetic energy, affects the work of other equipment, and can be subject to the electromagnetic interference of other equipment, therefore all medical electrical equipments all must meet the requirement of Electro Magnetic Compatibility, and the power supply of equipment then will meet the requirement of conduction interference.Electric knife is typical medical electrical equipment, so the requirement in order to meet conduction interference, will increase filter circuit at power supply place, effectively to limit the harassing and wrecking to power supply.

Utility model content

The purpose of this utility model is, overcome the deficiency of existing thermoelectric (al) type high frequency ammeter, a kind of filter of electric knife power supply is provided, solve the conduction interference requirement of high frequency surgical equipment Electro Magnetic Compatibility, to ensure equipment energy safety, stable operation, and ensure not have an impact to neighbouring equipment, reach the effect effectively limited the harassing and wrecking of power supply.

For achieving the above object, the technical solution adopted in the utility model is:

A filter for electric knife power supply, is connected in AC power, and this AC power is provided with live wire, zero line and ground wire; It is characterized in that: described filter comprises X electric capacity for eliminating differential mode interference, for eliminating two Y capacitance of common mode disturbances and the common mode inductance for the inside and outside interference of xegregating unit; Described X electric capacity is attempted by between described live wire and zero line, and described common mode inductance is attempted by between described live wire and zero line, is attempted by respectively between live wire and ground wire and between zero line and ground wire after described two Y capacitance are connected to described common mode inductance.

Further, described X electric capacity is 0.22uf, AC275V.

Further, described Y capacitance is 2200pF, AC275V.

Further, described common mode inductance is 16.64mH.

Compared with prior art, the utility model select inductance filter and X electric capacity combine with Y capacitance together with filtering interfering, well limit radiofrequency field induction conduction interference, reach the EMC Requirements of medical electrical equipment.

Accompanying drawing explanation

Fig. 1 is circuit theory diagrams of the present utility model.

Embodiment

Below in conjunction with accompanying drawing, the utility model is described in further detail.

First Fig. 1 structural schematic block diagram of the present utility model is consulted.The filter of diagram electric knife power supply is connected in AC power, and the input line of this AC power is three: live wire (L)/zero line (N)/ground wire (G).Described filter comprises X electric capacity C1, two Y capacitance C3 and C4 and common mode inductance L1.

Described X electric capacity C1 is for eliminating differential mode interference, and be attempted by between described live wire and zero line, its specification can get 0.22uf, AC275V.

Described common mode inductance L1 is used for the inside and outside interference of xegregating unit, and be attempted by between described live wire and zero line, its inductance value can be 16.64mH.

Described two Y capacitance C3 and C4 are for eliminating common mode disturbances, and after being connected to described common mode inductance L1, wherein, Y capacitance C3 is attempted by between live wire and ground wire, and Y capacitance C4 is attempted by between zero line and ground wire.The specification of described two Y capacitance C3 and C4 is 2200pF, AC275V.

The link position of two Y capacitance C3 and C4 is more crucial, relevant safety standard must be met, in case cause electronic equipment leak electricity or casing charged, jeopardize personal safety and life, so they all belong to safe electric capacity, require that capacitance can not (being generally nF level) bigger than normal, and withstand voltage must be higher.It is specifically intended that Y capacitance C3 and C4 is safe electric capacity, the certification of safety detection mechanism must be obtained.The withstand voltage of Y capacitance C3 and C4 generally all indicates mark of safety certification and AC250V or AC275V printed words, but its real DC break down voltage is up to more than 5000V.Therefore, Y capacitance C3 and C4 arbitrarily can not use the withstand voltage AC250V of nominal, or the conventional capacitive of DC400V and so on substitutes.

The electric capacity be connected in parallel between live wire and zero line is X electric capacity C1.The position that this electric capacity connects is also more crucial, and will meet safety standard equally, therefore, X electric capacity C1 equally also belongs to one of safe electric capacity, must obtain the certification of safety detection mechanism.The withstand voltage of X electric capacity C1 generally all indicates mark of safety certification and AC250V or AC275V printed words, but its real DC break down voltage is up to more than 2000V, does not arbitrarily use the conventional capacitive of withstand voltage AC250V or DC400V of nominal and so on to substitute when use.The capacitance of X electric capacity C1 is generally uF level, allows larger than Y capacitance C3 and C4.

The mylar class electric capacity that X electric capacity C1 generally selects ripple current larger, this electric capacity volume is general all very large, but it allows the electric current of moment discharge and recharge also very large, and its internal resistance is corresponding less.The index of conventional capacitive ripple current is all very low, and dynamic internal resistance is higher.Replace X electric capacity C1 with conventional capacitive, except withstand voltage condition can not meet, general ripple current index is also difficult to meet the demands.

In fact, only depending on X electric capacity C1 and two Y capacitance C3, C4, to filter out conducted interference signal be completely unlikely, because the non-constant width of the frequency spectrum of interference signal, substantially covers tens KHz to hundreds of MHz, the frequency range of even thousands of MHz.Usually, need very jumbo filter capacitor to the filtering of low side interference signal, but be subject to the restriction of safety condition, the capacity of Y capacitance C3, C4 and X electric capacity C1 all can not with large; To the filtering of high-end interference signal, the filtering performance extreme difference again of large bulk capacitance, particularly the high frequency performance of mylar film capacitor is general all poor, because it is produced with winding process, and mylar medium high frequency response characteristic falls far short compared with pottery or mica, and general mylar medium all has adsorption effect, and it can reduce the operating frequency of capacitor, mylar film capacitor operating frequency range, approximately all at about 1MHz, will significantly increase more than its impedance of 1MHz.

Therefore, the conducted interference produced to suppress medical electronic apparatus, except selecting Y capacitance C3, C4 and X electric capacity C1, also will select the inductance filter of multiple type, combine filtering interfering together simultaneously.Inductance filter belongs to low pass filter more, but inductance filter also has a lot of specification type, such as, have: differential mode, common mode, and high frequency, low frequency etc.Often kind of inductance is all mainly interference signal filtering for certain a bit of frequency and works, little to the filtration result of the interference signal of other frequency.Usually, the inductance that inductance value is very large, its coil turn is more, and so the distributed capacitance of inductance is also very large.High-frequency interferencing signal will be bypassed by distributed capacitance.And the magnetic core that permeability is very high, its operating frequency is then lower.At present, the operating frequency great majority of a large amount of inductance filter magnetic core used are all at below 75MHz.For the occasion that operating frequency requirements is higher, must select high-frequency ring magnetic core, high-frequency ring magnetic core permeability is general not high, but leakage inductance is little especially.

It should be noted that: due to the particularity of electric knife, it is larger that the inductance value of common mode inductance L1 need be got, and general power-supply filter cannot be effective.Moreover due to electric knife be Medical Devices, so the height (general representative value is 0.5mA ~ 5mA) compared the requirement of leakage current, in order to safety, leakage current will be reduced as much as possible, and the capacity adjusting Y capacitance C3 and C4 can adjust leakage current.

Do specific as follows in detail below in conjunction with embodiment to the utility model:

Embodiment

Choosing of X electric capacity is that situation according to current/voltage ripple is determined, computing formula (1) is as follows:

$C_X=\frac{K_1{I}_{i\left(\max \right)}}{2{\mathrm{\πfK}}_2{U}_{i\left(\min \right)}}\mathrm{...}\left(1\right)$

In formula: Cx is the capacitance of X electric capacity C1;

K1 is the high-frequency current ripple coefficient on common mode inductance L1, usually gets 0.3;

K2 is high frequency voltage ripple coefficient on common mode inductance L1, between 3 ~ 9%, gets 6%.

The input power Pi=500W of general electric knife, input net voltage U i=160V ~ 250V, fi=50HZ, input net electric current $Ii=\frac{Pi}{Ui}=2A~3.125A,$ Input peak current $Iip\left(max\right)=\sqrt{2}Ii\left(max\right)\≈4.42A,$ Switching Power Supply frequency f=100KHZ.

Above data are substituted in formula (1) and obtain:

$C_X=\frac{0.3\×3.125}{2\mathrm{\π}\×100000\×0.06\×160}\≈0.22uF$

So X electric capacity C1 specification gets AC275V, 0.22uf.

The effect of Y capacitance C3 and C4 is exactly that common-mode noise is flow to the earth, but noise current can not be too large, requires it is be less than 0.5mA, and usually, be operated in semi-tropical machine, require that earth leakage current can not more than 0.7mA in medical electronic apparatus safety standard; Be operated in temperate zone machine, require that earth leakage current can not more than 0.35mA, leakage current can be adjusted by the capacity adjusting Y capacitance C3 and C4, Y capacitance C3 and C4 generally can not more than 4700pF, so in order to safety, reduction leakage current as far as possible, the capacity of Y capacitance C3 and C4 can be determined by following formula (2):

$I_L=\frac{U}{\frac{1}{2{\mathrm{\πfC}}_Y}}\mathrm{...}\left(2\right)$

In formula:

I _lfor leakage current;

U is network source;

F is the frequency of network source;

C _yfor the capacitance of Y capacitance C3 and C4.

Be AC220V, f by data U be 50HZ, Y capacitance is that 2200pF substitutes in formula (2):

$I_L=\frac{220\&times;\sqrt{2}}{\frac{1}{2\mathrm{\&pi;}\&times;50\&times;2200\&times;{10}^{-12}}}=0.215mA<0.35mA$

So the specification of Y capacitance C3 and C4 gets AC275V, 2200pF thinks suitable.

Common mode inductance L1 selects the toroidal core of MnZn material, owing to considering the limitation of installation site, the magnetic core selected is 25mm × 15mm × 13mm, can enclose around 40 according to this size 0.9mm enamelled wire is maximum, the permeability of this kind of magnetic core is 8000, can calculate the inductance value of common mode inductance L1 according to formula (3).

$L=0.4{\mathrm{\&pi;\&mu;N}}^2\frac{F}{l}\&times;{10}^{-5}\mathrm{...}\left(3\right)$

In formula: L is the inductance value (mH) of common mode inductance L1;

μ is the permeability of magnet ring;

N is coil turn;

F is the sectional area of magnet ring; $F=\frac{D-d}{2}\&times;h\left({\mathrm{cm}}^2\right)$

D is the external diameter of magnet ring;

D is the internal diameter of magnet ring;

H is the height of magnet ring;

L is the average length of magnet ring. $l=\mathrm{\&pi;}\&times;\frac{D+d}{2}\left(cm\right)$

Data are substituted in formula (3):

$L=0.4\mathrm{\&pi;}\&times;8000\&times;{40}^2\&times;\frac{\frac{2.5-1.5}{2}\&times;1.3}{\mathrm{\&pi;}\&times;\frac{2.5+1.5}{2}}\&times;{10}^{-5}=16.64mH$

Because permeability has the deviation (what select is representative value) of 20% herein, so have lower deviation in the measurement of reality, can adjust in concrete use, inductance value can be improved ripple greatly.

Claims (4)

1. a filter for electric knife power supply, is connected in AC power, and this AC power is provided with live wire, zero line and ground wire; It is characterized in that: described filter comprises X electric capacity for eliminating differential mode interference, for eliminating two Y capacitance of common mode disturbances and the common mode inductance for the inside and outside interference of xegregating unit; Described X electric capacity is attempted by between described live wire and zero line, and described common mode inductance is attempted by between described live wire and zero line, is attempted by respectively between live wire and ground wire and between zero line and ground wire after described two Y capacitance are connected to described common mode inductance.

2. the filter of electric knife power supply according to claim 1, is characterized in that: described X electric capacity is 0.22uf, AC275V.

3. the filter of electric knife power supply according to claim 1, is characterized in that: described Y capacitance is 2200pF, AC275V.

4. the filter of electric knife power supply according to claim 1, is characterized in that: described common mode inductance is 16.64mH.