CN102843019B - A kind of filter circuit - Google Patents

Abstract

The invention discloses a kind of filter circuit, comprising the first electric capacity, the first switch, being withstand voltagely less than the second electric capacity of the first electric capacity and the voltage detecting and controling circuit for detecting DC input voitage; The two ends of the first electric capacity are respectively plus end and the negative terminal of filter circuit, second electric capacity and the first switch are in series, this series arm and the first electric capacity are in parallel, the voltage detecting input positive pole of voltage detecting and controling circuit is connected with the plus end of filter circuit, voltage detecting inputs the control end that negative pole is connected with the negative terminal of filter circuit, the first output is connected to the first switch, voltage detecting and controling circuit is provided with the first preset value, and when detecting that DC input voitage is less than the first preset value, control the first switch conduction; When detecting that DC input voitage is more than the first preset value, controlling the first switch and disconnecting.The present invention can provide suitable filter capacity for the input voltage of different range, and realize cost low, take up room little.

Description

A kind of filter circuit

Technical field

The present invention relates to rectifier filter circuit, the rectifier filter circuit of particularly Width funtion input.

Background technology

Electronic circuit all needs DC power supply to provide energy.Although useful chemical battery is as DC power supply in some cases, be in most cases that the AC power utilizing electrical network to provide obtains DC power supply through conversion.

AC-DC circuit is a lot, and industry and folk power supply generally adopt Alternating Current Power Supply, shown in Fig. 1 is in time by the civilian alternating current of China that sinusoidal rule changes, be called alternating sinusoidal voltage, change the cycle that the once required time is called alternating voltage, represent with T, the said 220V of industry, refer to effective value, its peak value is times effective value, is:

$220V\×\sqrt{2}=311.1V$ Formula (1)

The size and Orientation of direct voltage (or electric current) does not change in time.As voltage represented by curve, be then the straight line parallel with horizontal time axis, but we are generally constant direction, but the size of voltage (or electric current) change to some extent in time also referred to as direct voltage (or electric current).

In fact, industrial and civilianly all often need to become exchange into direct current, or even the direct current of isolation, along with national standard is to the further requirement of the power factor of electrical appliance, at present, to various electric equipment all power factor requirements of more than consumed power 75W, namely require that the operating current waveform fundamental sum voltage waveform of circuit is identical.The existing circuit of power factor correction that adopts addresses this problem at present, and circuit of power factor correction, referred to as pfc circuit, is the abbreviation of PowerFactorCorrection.

Note: 75W, data from CNS GB17625.1-1998, is called " Harmonic Current Limits (the every phase input current≤16A of equipment) that low-voltage electrical and electronic equipment send ".

And input power being less than to the various electric equipment of 75W, the rectification of its inside, filter circuit still adopt common rectification circuit to add the topology of filter circuit.

Fig. 2 shows halfwave rectifier filter circuit, U _aCfor the sinusoidal voltage of input, diode D is rectifying tube, electric capacity C _lfor the main body of filter circuit, resistance R _lfor " load " of load circuit or equivalence, U _lfor the direct voltage exported.When inputting for alternating current, because Fig. 2 circuit is only at U _aCpositive half cycle work, so all in low-power circuit, in the rectification circuit as the Switching Power Supply of below 5W.In Fig. 2 circuit, diode D reversal connection, can be operated in U _aCnegative half period.

Shown in Fig. 3 is exactly full-wave rectifier filter circuit, generally cannot be directly used in commercial power rectification, generally through the centre cap winding of transformer B1 secondary, will obtain two groups of voltage U that voltage is identical, phase place is contrary ₁and U ₂, just can use.Voltage U ₁and U ₂output dc voltage after diode Da and Db rectification, electric capacity C _lfor the main body of filter circuit, resistance R _lfor " load " of load circuit or equivalence, U _lfor the direct voltage exported.

What Fig. 4-1, Fig. 4-2, Fig. 4-3 illustrated is bridge rectifier, is full bridge rectifier again, and these three kinds of techniques of painting are all conventional, and their annexation is consistent, and Fig. 4-2 is the simple and easy technique of painting.If electric capacity C _ldo not access, identical shown in its output waveform with Fig. 5-1, be Rectified alternating current; Electric capacity C _lafter access, its output waveform, in Fig. 5-2 shown in solid line, is comparatively level and smooth Rectified alternating current.After circuit stable state, rectifier diode Da and rectifier diode Dc only conducting in t1 to the t2 time in Fig. 5-2 in Fig. 4-1 to Fig. 4-3; And rectifier diode Db and rectifier diode Dd only conducting in t3 to the t4 time in Fig. 5-2, to electric capacity C during diode current flow _lcharging, At All Other Times by electric capacity C _lto load R _lelectric discharge, if think, direct voltage is level and smooth, electric capacity C _lwill be very large, and electric capacity C _lstrengthen, the ON time of t1 to t2 and t3 to t4 can be caused very short, charging current is very big, and circuit, also only at this time loss input current, causes grid voltage waveform distortion.The principle of this part also can with reference to " stabilized power supply " first edition in 1984 of People's Telecon Publishing House's publication, standard book number is: 15045 total 2790-are without 6260, the 35th page of Figure 24 3 of this book also fully illustrates this principle, 34th page the 3rd section illustrates: " for capacitor filtering full-wave rectification situation; according to Figure 24 3, reader can analyze voluntarily.This analysis is also applicable to bridge rectifier.”

In a lot of industry, as power industry, need the wide Switching Power Supply reaching 85VAC to 460VAC of a kind of input voltage, general input power is all less than 75W, common BOOSTPFC circuit is used to need the output filter capacitor of electrochemical capacitor series connection as pfc circuit of use two withstand voltage 400V, add other circuit part of PFC, cost is very high.And owing to have employed two-step scheme, device populations increases, its dependability declines.

For the product such as wide pressure input switch power supply of 85VAC to 460VAC, the selection of its filter capacitor is a problem making that designer is puzzled, DC voltage range after above-mentioned voltage commutation is: 120V to 650V, for the direct voltage of 650V, need to select the capacitances in series of two withstand voltage 400V to obtain, as the electric capacity C in Fig. 2 to Fig. 4 series _l, need series connection to obtain, Fig. 6 shows circuit, by electrochemical capacitor C _l1and C _l2be composed in series, can respectively at electrochemical capacitor C during actual use _l1and C _l2grading resistor in parallel connection.Fig. 7 shows the block diagram that input voltage is the wide pressure input switch power supply of 85VAC to 460VAC, U _aCfor input voltage, be the wide pressure input of 85VAC to 460VAC, 100 is rectification circuit, halfwave rectifier and bridge rectifier can, electric capacity C _lfor filter capacitor, 101 is the DC/DC converter of power stage, and it exports as direct current output.

At input U _aCfor under 85VAC, when in direct current output no-load situation, U _lfor the direct voltage of 120V, need the filter capacitor of larger capacity, and this electric capacity is once establish, it is at input U _aCunder rising to high-pressure situations, just seeming, capacity is excessive, causes unnecessary waste.

If the conversion efficiency that the DC output end power output of Switching Power Supply is main power stage 101 in Po, Fig. 7 is η, so high-pressure side U _lequivalent consumed power be Pg, so have:

$\mathrm{Pg}=\frac{\mathrm{Po}}{\mathrm{\η}}$ Formula (2)

The alternating voltage of Switching Power Supply is U _aC, so, the D.C. resistance R of the at this moment equivalence of Switching Power Supply power stage 101 _dfor:

$R_D=\frac{{\left(\sqrt{2}{U}_{\mathrm{AC}}\right)}^2}{\frac{\mathrm{Po}}{\mathrm{\η}}}=\frac{2\mathrm{\η}{U_{\mathrm{AC}}}^2}{\mathrm{Po}}$ Formula (3)

It is generally acknowledged, this resistance R _dwith high-voltage filtering capacitor C _lproduct, i.e. timeconstantτ, be greater than 3 times of the Rectified alternating current cycle after rectification and more than, for the alternating current of 50Hz, after rectification, the frequency of Rectified alternating current is 100Hz, and its cycle is 10mS, so timeconstantτ is greater than 30mS, certainly, more greatly, after AC rectification, the ripple of Rectified alternating current is less.

Note: timeconstantτ, be greater than 3 times of the Rectified alternating current cycle after rectification and more than, this part content please refer to " Basic Analog Electronics " second edition the 647th page to 650 pages of Tong Shibai chief editor, this book ISBN 7-04-000868-8/TN53.The requirement of " 3 times " is 0.2 to derive according to the ripple factor S of the 650th page (11-11), now U in Fig. 7 _lripple voltage is the lower limit that can bear of proximity switch power supply, to ask ripple voltage little, and so electric capacity C _lcapacity required is larger.

Wushu (3) substitutes into time constant formula, i.e. filter capacitor C _lminimum value be:

$C=\frac{\mathrm{\τ}}{R_D}=\frac{\mathrm{\τ}}{\frac{2\mathrm{\η}{U_{\mathrm{AC}}}^2}{\mathrm{Po}}}=\frac{\mathrm{\τPo}}{2\mathrm{\η}{U_{\mathrm{AC}}}^2}$ Formula (4)

If calculate with the consumed power Pg of high-pressure side, namely formula (2) substitutes into formula (4), and above formula (4) can be reduced to:

$C=\frac{\mathrm{\τ}}{2}\×\frac{\mathrm{Pg}}{{U_{\mathrm{AC}}}^2}$ Formula (5)

So, be the Switching Power Supply of the wide pressure input of 85VAC to 460VAC for input voltage, as shown in Figure 7, if make the product exporting 40W, 12V, if the efficiency of main power stage 101 is 85%, above-mentioned timeconstantτ gets 30mS, uses formula (5) to calculate at different input voltage U _aCunder, the filter capacitor C needed for reality _las following table one:

Table one

As can be seen from upper table one, this 40W power supply normally works in order to ensure under 85VAC, filter capacitor needs value 100uF, due to high pressure 650V under high pressure will be born, generally select 100uF/400V electric capacity 4, two series connection, more in parallel, as shown in Figure 8, can respectively at electrochemical capacitor C during actual use _l1and C _l2and C _l3and C _l4grading resistor in parallel connection, finally obtain the electric capacity of 100uF, cost is higher, and the electrochemical capacitor of the low ESR of 100uF/400V that the Japanese NCC also widely used according to industrial quarters accreditation produces, be about 4.4 yuan one, total cost is not less than 17.6 yuan.And the volume of 4 high-voltage electrolytic capacitors can not be ignored when designing, and its space taken is larger.

Note: to 2011, the electrochemical capacitor that 700V is withstand voltage is developed, the YDK-700V electrochemical capacitor that YAMAHA-TDK develops comes out, this means the 537V direct current after 380VAC rectification out, again the electrochemical capacitor of 2 400V need not go series connection as Fig. 6.The electrochemical capacitor volume of 100uF/700V is generally 35 × 80-100mm or 50 × 80-96mm, but price is at about 139 yuans, cannot be applied to (input power is less than 75W) in small-power switching power-supply as herein described.

Therefore, input power is less than to the various electric equipment of 75W, the rectification of its inside, filter circuit still adopt common rectification circuit to add the topology of filter circuit, and under wide pressure input range, it is high that existing filter circuit exists cost, and take up room large deficiency.

Summary of the invention

In view of this, the object of the invention is to solve under wide pressure input range, it is high to there is cost in existing filter circuit, take up room large problem, a kind of filter circuit is provided, suitable filter capacity can be provided for the input voltage of different voltage range, and realize cost relatively reduce, take up room less.

The object of the invention is to be realized by following technical measures:

A kind of filter circuit, comprise the first electric capacity, the two ends of this first electric capacity are respectively plus end and the negative terminal of filter circuit, DC input voitage is from plus end and negative terminal input filter circuit, and described filter circuit also comprising the first switch, being withstand voltagely less than the second electric capacity of described first electric capacity and the voltage detecting and controling circuit for detecting described DC input voitage, described second electric capacity and the first switch are in series, this series arm and described first electric capacity are in parallel, described voltage detecting and controling circuit has voltage detecting input positive pole, voltage detecting input negative pole and the first output, the voltage detecting input positive pole of voltage detecting and controling circuit is connected with the plus end of filter circuit, voltage detecting input negative pole is connected with the negative terminal of filter circuit, first output is connected to the control end of the first switch, described voltage detecting and controling circuit is provided with the first preset value, and when detecting that DC input voitage is less than the first preset value, control the first switch conduction, when detecting that DC input voitage is more than the first preset value, controlling the first switch and disconnecting.Being called for short the program is below primitive technology scheme of the present invention.

As the further improvement of technique scheme, described filter circuit also comprises second switch and withstand voltage the 3rd electric capacity being less than described second electric capacity; Described second switch and the 3rd electric capacity are in series, the series arm of second switch and the 3rd electric capacity be in parallel with described first electric capacity, described voltage detecting and controling circuit also has the second output, second output of voltage detecting and controling circuit is connected to the control end of second switch, described voltage detecting and controling circuit is also provided with the second preset value being less than described first preset value, and when detecting that DC input voitage is less than the second preset value, control second switch conducting; When detecting that DC input voitage is more than the second preset value, controlling second switch and disconnecting.Being called for short the program is below improvement opportunity scheme of the present invention.

Wherein, in above-mentioned two schemes, the working method of voltage detecting and controling circuit has two kinds, first kind of way is the voltage peak that described voltage detecting and controling circuit detects described DC input voitage, and the second way is the average voltage that described voltage detecting and controling circuit detects described DC input voitage.

In above-mentioned two schemes, the supply power mode of voltage detecting and controling circuit has two kinds, to be described voltage detecting and controling circuit obtain power supply by the DC input voitage of input filter circuit to a kind of mode, and another kind of mode is that described voltage detecting and controling circuit is obtained by the accessory power supply of the rear class Switching Power Supply be connected with filter circuit and powers.

Preferably, the first switch in each scheme above-mentioned and second switch are metal-oxide-semiconductor.

Preferably, the first switch in each scheme above-mentioned and second switch are relay.

Operation principle of the present invention and using method illustrate:

For primitive technology scheme, according to above-mentioned annexation, obviously, it is little that first electric capacity chooses capacity, but the withstand voltage electrochemical capacitor being greater than direct voltage maximum, and the second electric capacity to choose capacity large, but withstand voltage lower electrochemical capacitor, withstand voltagely generally be selected in direct voltage median, if the first preset value gets direct voltage median, so have, when direct voltage is less than the first preset value (direct voltage median), first output output signal, control the first switch conduction, at this moment, second electric capacity is access in filter circuit of the present invention, the filtering total capacity of filter circuit is the capacity sum of the first electric capacity and the second electric capacity, when input voltage is less than direct voltage median, obtain larger filter capacitance, and when direct voltage is more than the first preset value, first output exports opposite signal, control the first switch to disconnect, at this moment the second electric capacity does not have place in circuit, filter action is still born by withstand voltage the first higher electric capacity, at this moment because direct voltage is high, do not need larger filter capacity, whole switching power circuit still can comparatively good berth.

And above-mentioned improvement opportunity scheme, can be operated within the scope of wider input direct voltage, its detailed operation principle is similar with above-mentioned, repeats no more here, as input direct voltage is divided into three sections from low to high, two separations are wherein respectively the second preset value, the first preset value.

When direct voltage is less than the second preset value, all conductings of the first switch and second switch, the first electric capacity, the second electric capacity, the whole place in circuit of the 3rd electric capacity, filter circuit of the present invention obtains maximum filter capacity;

And when direct voltage is more than the second preset value, be still in when being less than the first preset value, and the first switch conduction, second switch disconnects, the first electric capacity, the second electric capacity place in circuit, and withstand voltage the 3rd minimum electric capacity is disconnected; Filter action is still born by withstand voltage the first the highest electric capacity, withstand voltage the second higher electric capacity, at this moment because direct voltage is higher, does not need larger filter capacity, and whole switching power circuit still can comparatively good berth.

And when direct voltage is more than the first preset value, the first switch, second switch disconnect, withstand voltage the second lower electric capacity, withstand voltage the 3rd minimum electric capacity are disconnected; Filter action is still born by withstand voltage the first higher electric capacity, and at this moment because direct voltage is very high, when needing very little filter capacity, whole switching power circuit still can comparatively good berth.

Because the electrochemical capacitor price of high pressure low volume electrochemical capacitor and low-voltage high-capacity is all lower, and volume also reduces.Choose suitable voltage detecting and controling circuit, and the metal-oxide-semiconductor of low speed, cost can be reduced by more than 30%, this can provide Data Comparison in an embodiment.

Compared with prior art, the present invention has following beneficial effect:

The first, can provide suitable filter capacity for the input voltage of different voltage range, be applicable to the wide pressure input occasion or the photovoltaic DC input that are applied to interchange, cost reduces;

The second, volume reduces, and has saved the area of circuit board, reduce further cost;

3rd, filter circuit of the present invention is still two-terminal network, directly can substitute former filter capacitor.

Accompanying drawing explanation

Fig. 1 is in time by the alternating voltage waveform figure that sinusoidal rule changes;

Fig. 2 is halfwave rectifier filter circuit;

Fig. 3 is full-wave rectifier filter circuit;

Fig. 4-1 is bridge rectifier filter circuit;

Fig. 4-2 is the simple and easy technique of painting of bridge rectifier filter circuit;

Fig. 4-3 is the another kind of technique of painting of bridge rectifier filter circuit;

Fig. 5-1 is bridge rectifier, does not connect the Rectified alternating current oscillogram that filter capacitor exports;

Fig. 5-2 is the output voltage waveform of bridge-type (or all-wave) rectification circuit when connecting filter capacitor;

Fig. 6 is the schematic diagram that capacitances in series substitutes former electric capacity;

The wide pressure input switch power supply block diagram of Fig. 7 to be input voltage be 85VAC to 460VAC;

Fig. 8 is filter capacitor C in Fig. 7 Switching Power Supply _lthe actual resolution circuitry figure used;

Fig. 9 is the theory diagram drawn according to technical solution of the present invention, is also the first embodiment theory diagram;

Figure 10 is the first embodiment schematic diagram;

Figure 11 is the second embodiment schematic diagram;

Figure 12 is the 3rd embodiment schematic diagram;

Figure 13 replaces low-voltage voltage stabilizing didoe schematic diagram for using Diode series;

Figure 14 is the theory diagram drawn according to technical scheme after improvement, is also the 4th embodiment theory diagram;

Figure 15 is the 4th embodiment schematic diagram;

Figure 16 is the 5th embodiment schematic diagram;

Figure 17 is the 6th embodiment schematic diagram.

Embodiment

First embodiment

Fig. 9 shows the theory diagram of the first embodiment, is the theory diagram drawn according to primitive technology scheme of the present invention.

In Figure 10 200 partially illustrates the concrete schematic diagram of first embodiment of the invention; Its annexation, completely with the relation in technical scheme, comprises plus end 104 and negative terminal 105, comprises voltage detecting and controling circuit 102, one first electric capacity C1, one second electric capacity C2, one first the withstand voltage of switch 103, second electric capacity C2 is less than the withstand voltage of the first electric capacity C1; Voltage detecting and controling circuit 102 comprises three ports, and voltage detecting input is positive 106, negative 107, first output 108 of voltage detecting input; Plus end 104 connects the voltage detecting input positive 106 of voltage detecting and controling circuit 102, plus end 104 also connects one end (being electrochemical capacitor positive pole) of the first electric capacity C1 here simultaneously, and one end of the second electric capacity C2 (electrochemical capacitor positive pole); Negative terminal 105 connects the voltage detecting input negative 107 of voltage detecting and controling circuit 102, negative terminal 105 also connects the other end (electrochemical capacitor negative pole) of the first electric capacity C1 simultaneously, and first one end of switch 103, the other end of the first switch 103 connects the other end (electrochemical capacitor negative pole) of the second electric capacity C2; Voltage detecting input positive 106 is returned voltage detecting and controling circuit 102 simultaneously and is powered.

Voltage detecting and controling circuit 102 in the present embodiment, is the first working method, for detecting the peak value of the direct voltage between plus end and negative terminal.Voltage detecting and controling circuit 102 comprises: resistance R1, resistance R2, resistance R3, electric capacity C4, diode D1, NPN type triode T1, the annexation of voltage detecting and controling circuit 102 is: one end of the anode contact resistance R3 of diode D1, tie point coating-forming voltage detects input positive 106, one end of the negative electrode contact resistance R1 of diode D1, connect one end of electric capacity C4 simultaneously, one end of the other end contact resistance R2 of resistance R1, its tie point connects the base stage of NPN type triode T1 simultaneously; The other end of the emitter contact resistance R2 of NPN type triode T1, connects the other end of electric capacity C4 simultaneously, and tie point coating-forming voltage detects input negative 107; The other end of the collector electrode contact resistance R3 of NPN type triode T1, tie point forms the first output 108;

First switch 103 in the present embodiment, main body is the metal-oxide-semiconductor T2 of a N raceway groove, with a voltage stabilizing didoe D2, the grid of metal-oxide-semiconductor T2 directly connects the first output 108 of voltage detecting and controling circuit 102, connect the negative electrode of voltage stabilizing didoe D2 simultaneously, the source electrode of metal-oxide-semiconductor T2 connects the anode of voltage stabilizing didoe D2, form one end of the first switch 103, and connect negative terminal 105, the drain electrode of metal-oxide-semiconductor T2 is exactly the other end of previously described first switch 103, connects the other end (electrochemical capacitor negative pole) of the second electric capacity C2.

Its operation principle is, diode D1 and electric capacity C4 forms peak rectifier circuit, this be due to resistance R3 and resistance R1 value very large, the cause that current sinking is minimum, the terminal voltage of electric capacity C4 is the peak value of Rectified alternating current between plus end 104 to negative terminal 105, can pulsating direct current electrical schematic in reference diagram 5-2.When direct voltage is less than the first preset value, the terminal voltage of electric capacity C4 is after resistance R1 and resistance R2 dividing potential drop, be not enough to cause NPN type triode T1 conducting, NPN type triode T1 is in cut-off state, its current collection very high level, the voltage of plus end 104 is added to the grid of metal-oxide-semiconductor T2 through resistance R3, owing to there is voltage stabilizing didoe D2, this high pressure by voltage stabilizing didoe D2 voltage stabilizing, can guarantee that metal-oxide-semiconductor T2 can not damage.The grid level of metal-oxide-semiconductor T2 is owing to there being enough operating voltages, and the complete conducting of metal-oxide-semiconductor T2, because metal-oxide-semiconductor is when conducting, is equivalent to a resistance, is commonly referred to as R _{dS (ON)}, this resistance is very little, equals electric capacity C2 and electric capacity C1 in parallel, gives rectification circuit 100 filtering together.

When direct voltage is more than the first preset value, the terminal voltage of electric capacity C4 is after resistance R1 and resistance R2 dividing potential drop, be enough to cause NPN type triode T1 conducting, because metal-oxide-semiconductor is voltage control device, the general value of resistance R3 is more than mega-ohms, NPN type triode T1 is in saturation conduction state, between its collector electrode to negative terminal 105, voltage is low level, its voltage is generally less than 0.7V, be added to the grid of metal-oxide-semiconductor T2 to source electrode, metal-oxide-semiconductor T2 not conducting completely, be in open-circuit condition, work in metal-oxide-semiconductor T2 inside only parasitic diode (BodyDiode), this parasitic diode externally can only bleed off the electric energy of electric capacity C2, and external circuit cannot be charged to electric capacity C2 by parasitic diode, namely when direct voltage is more than the first preset value, electric capacity C2 is inoperative in circuit, do not bear higher magnitude of voltage more withstand voltage than self.

So the first preset value is generally set to the nominal withstand voltage of electric capacity C2.

Below, with one group of real data, the beneficial effect that the present invention brings is described, in Figure 10 circuit, resistance R1 is two 2.7M Ω resistant series gained, total resistance is 5.4M Ω, resistance R2 is 6.8K Ω, resistance R3 is 10M Ω, electric capacity C4 is the CBB electric capacity of 103/630V, diode D1 is 1N4007, NPN type triode T1 is S9014, the metal-oxide-semiconductor T2 of N raceway groove is STF5NK90Z, voltage stabilizing didoe D2 is 0.5W12V voltage-stabiliser tube, to be 22uF/400V electric capacity to connect gained by Fig. 6 electric capacity C1, capacity after series connection is 11uF, brand is all the homologous series electric capacity of Japanese NCC, electric capacity C2 is the 100uF/400V electrochemical capacitor of same brand.

After circuit welds, surveying the first preset value is about 411V, and regulating resistance R1 or R2 can regulate the value of the first preset value, due within ± 3% precision, does not just adjust.Actual measurement is under different voltage, and the filter capacity that circuit of the present invention provides is for shown in table two:

Table two

Can see from upper table, the present invention in extremely wide voltage range, all than the C calculated _lcapacity minimum value wants large, can meet user demand completely.

Cost in background technology is 17.6 yuan, then looks at the total cost of circuit of the present invention, see table three:

Table three

As can be seen from Table III, cost drops to 9.30 yuan from 17.6 yuan, and cost of the present invention is 52.8% of the cost in background technology, have dropped 47% more than.

Obviously, the volume of the 100uF/400V in the volume ratio background technology of electrochemical capacitor 22uF/400V is little, and uses the 100uF/400V electric capacity that a volume is larger less, and the element of increase is not owing to having fin, and overall institute takes up space very little.

Figure 10 circuit, for detecting the peak value of the direct voltage between plus end 104 and negative terminal 105, resistance R1 is two 2.7M Ω resistant series gained, if electric capacity C4 is connected on the centre of two resistance, the other end still connects negative terminal 105, save diode D1, namely replace diode D1 with a resistance, so circuit just becomes the second working method: the mean value detecting the direct voltage between plus end and negative terminal simultaneously.This is the circuit shown in the second embodiment just.

Second embodiment

Figure 11 shows the schematic diagram of the second embodiment, in Figure 11 200 partially illustrates the concrete schematic diagram of second embodiment of the invention, its annexation observes the relation in technical scheme completely, comprise plus end 104 and negative terminal 105, comprise voltage detecting and controling circuit 102, one first electric capacity C1, one second electric capacity C2, one first the withstand voltage of switch 103, second electric capacity C2 is less than the withstand voltage of the first electric capacity C1; Voltage detecting and controling circuit 102 comprises three ports, and voltage detecting input is positive 106, negative 107, first output 108 of voltage detecting input; Plus end 104 connects the voltage detecting input positive 106 of voltage detecting and controling circuit 102, and plus end 104 also connects one end (electrochemical capacitor positive pole) of the first electric capacity C1 simultaneously, and one end of the second electric capacity C2 (electrochemical capacitor positive pole); Negative terminal 105 connects the voltage detecting input negative 107 of voltage detecting and controling circuit 102, negative terminal 105 also connects the other end (electrochemical capacitor negative pole) of the first electric capacity C1 simultaneously, and first one end of switch 103, the other end of the first switch 103 connects the other end (electrochemical capacitor negative pole) of the second electric capacity C2; Voltage detecting input positive 106 is returned voltage detecting and controling circuit 102 simultaneously and is powered.

Voltage detecting and controling circuit 102 in the present embodiment, is the second working method, for detecting the mean value of the direct voltage between plus end and negative terminal.Voltage detecting and controling circuit 102 comprises: resistance R1, resistance R2, resistance R3, resistance R4, electric capacity C4, NPN type triode T1, the annexation of voltage detecting and controling circuit 102 is: one end of resistance R4 one end contact resistance R3, tie point coating-forming voltage detects input positive 106, one end of resistance R4 other end contact resistance R1, connect one end of electric capacity C4 simultaneously, one end of the other end contact resistance R2 of resistance R1, its tie point connects the base stage of NPN type triode T1 simultaneously; The other end of the emitter contact resistance R2 of NPN type triode T1, connects the other end of electric capacity C4 simultaneously, and tie point coating-forming voltage detects input negative 107; The other end of the collector electrode contact resistance R3 of NPN type triode T1, tie point forms the first output 108;

In the present embodiment, execution mode is with the first embodiment for first switch 103;

Its operation principle is, resistance R4 and electric capacity C4 forms low-pass filter circuit, when its time constant is much larger than cycle of Rectified alternating current, tie point at resistance R4 and electric capacity C4 is greatly absorbed by the Alternating Component of pulsation, the Alternating Component that the electric current being added to NPN type triode T1 by resistance R1 so is not pulsed substantially.

Except detecting the mean value of the direct voltage between plus end 104 and negative terminal 105, other operation principle is completely with the first embodiment, unlike, first preset value is the mean value of direct voltage between plus end and negative terminal due to correspondence, so the first preset value is generally set to below the nominal withstand voltage of electric capacity C2, the nominal withstand voltage being preferably electric capacity C2 deducts the half of the Alternating Component peak-to-peak value of pulsation, Alternating Component peak-to-peak value as pulsation is 40V, the nominal withstand voltage that so the first preset value is generally set to electric capacity C2 deducts 20V, be only safe, if the nominal withstand voltage of electric capacity C2 is 400V, so the first preset value should at (400V-20V)=below 380V.

Below, with one group of real data, the beneficial effect that the present invention brings is described, in Figure 11 circuit, resistance R1 is 1.8M Ω, resistance R2 is 5.1K Ω, resistance R3 is 10M Ω, resistance R4 is 2M Ω, electric capacity C4 is the CBB electric capacity of 103/630V, NPN type triode T1 is 2N5551, the metal-oxide-semiconductor T2 of N raceway groove is STF5NK90Z, voltage stabilizing didoe D2 is 0.5W10V voltage-stabiliser tube, to be 22uF/400V electric capacity to connect gained by Fig. 6 electric capacity C1, capacity after series connection is 11uF, brand is all the homologous series electric capacity of Japanese NCC, and electric capacity C2 is the 100uF/400V electrochemical capacitor of same brand.

After circuit welds, surveying the first preset value is about 385V, and regulating resistance R1 or R2 or R4 can regulate the value of the first preset value, due within ± 3% precision, does not just adjust.Actual measurement is under different voltage, and the filter capacity that circuit of the present invention provides is for shown in table four:

Table four

Can see from upper table, the present invention in extremely wide voltage range, all than the C calculated _lcapacity minimum value wants large, can meet user demand completely.

Cost in background technology is 17.6 yuan, and owing to saving diode D1, increase a resistance R4, cost declines 0.05 yuan, and be 9.25 yuan, be more or less the same with the first embodiment, the cost of table three still has reference significance.

Therefore the second embodiment still can realize goal of the invention.

In the circuit of Figure 10 and Figure 11, because voltage detecting is mainly by electric resistance partial pressure, use NPN type triode T1 base stage again to the pressure drop of emitter as detection reference voltage, and transistor base is larger to the pressure drop temperature influence of emitter, therefore the temperature characterisitic of foregoing circuit is bad, and first preset value be a confusion region that there is positive and negative a few volt, and this problem that will solve of circuit shown in the 3rd embodiment just.

3rd embodiment

Figure 12 shows the schematic diagram of the 3rd embodiment, in Figure 12 200 partially illustrates the concrete schematic diagram of third embodiment of the invention, its annexation observes the relation in technical scheme completely, comprise plus end 104 and negative terminal 105, comprise voltage detecting and controling circuit 102, one first electric capacity C1, one second electric capacity C2, one first the withstand voltage of switch 103, second electric capacity C2 is less than the withstand voltage of the first electric capacity C1; Voltage detecting and controling circuit 102 comprises three ports, and voltage detecting input is positive 106, negative 107, first output 108 of voltage detecting input; Plus end 104 connects the voltage detecting input positive 106 of voltage detecting and controling circuit 102, and plus end 104 also connects one end (electrochemical capacitor positive pole) of the first electric capacity C1 simultaneously, and one end of the second electric capacity C2 (electrochemical capacitor positive pole); Negative terminal 105 connects the voltage detecting input negative 107 of voltage detecting and controling circuit 102, negative terminal 105 also connects the other end (electrochemical capacitor negative pole) of the first electric capacity C1 simultaneously, and first one end of switch 103, the other end of the first switch 103 connects the other end (electrochemical capacitor negative pole) of the second electric capacity C2; Voltage detecting input positive 106 is returned voltage detecting and controling circuit 102 simultaneously and is powered.

Voltage detecting and controling circuit 102 in the present embodiment, is still the second working method, for detecting the mean value of the direct voltage between plus end and negative terminal.

Voltage detecting and controling circuit 102 comprises: resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, electric capacity C4, voltage stabilizing didoe D3, NPN type triode T1, the annexation of voltage detecting and controling circuit 102 is: one end of resistance R4 one end contact resistance R3, one end of contact resistance R5 simultaneously, tie point coating-forming voltage detects input positive 106, one end of resistance R4 other end contact resistance R1, connect one end of electric capacity C4 simultaneously, one end of the other end contact resistance R2 of resistance R1, its tie point connects the base stage of NPN type triode T1 simultaneously; The emitter of NPN type triode T1 connects the negative electrode of voltage stabilizing didoe D3, the other end of contact resistance R5 while of tie point; The other end of the anode contact resistance R2 of voltage stabilizing didoe D3, connects the other end of electric capacity C4 simultaneously, and tie point coating-forming voltage detects input negative 107; The other end of the collector electrode contact resistance R3 of NPN type triode T1, tie point forms the first output 108;

In the present embodiment, execution mode is with the first embodiment for first switch 103; The voltage stabilizing value of voltage stabilizing didoe D3 adds that NPN type triode T1 saturation voltage drop requires to be less than grid, the source electrode cut-in voltage VGS of metal-oxide-semiconductor T2.

The operation principle first illustratively increasing circuit part newly and the beneficial effect brought, contrast the second embodiment, the present embodiment has newly increased resistance R5 and voltage stabilizing didoe D3, because circuit working is under extremely wide input voltage, in order to reduce the power consumption that resistance R5 brings, the electric current flowing through R5 generally can control at below 200uA, however, voltage stabilizing didoe D3 still obtains certain voltage stabilizing value, can be much less than nominal value, just because of the existence of voltage stabilizing didoe D3, the voltage of NPN type triode T1 base stage and ohmic connection points is elevated, namely virtual " reference voltage " of voltage detecting and controling circuit 102 becomes NPN type triode T1 base stage adds voltage stabilizing didoe D3 actual voltage stabilizing value to emitter voltage drop.Because reference voltage is significantly promoted, the change that NPN type triode T1 base stage produces because of temperature to emitter voltage drop is compared with reference voltage, and shared ratio is less, improves the temperature stability of circuit.

In order to obtain better performance, resistance R5 can replace with the constant-current source of small area analysis, this part circuit of constant-current source is known technology, can application reference number be the circuit of 104 parts and Figure 10 in Fig. 9 in " a kind of AC-DC circuit " of 201210056555.9.

Voltage stabilizing value due to voltage stabilizing didoe D3 adds that NPN type triode T1 saturation voltage drop requires to be less than grid, the source electrode cut-in voltage V of metal-oxide-semiconductor T2 _gS, and grid, the source electrode cut-in voltage V of current metal-oxide-semiconductor T2 _gSoften be low to moderate 3V, triode T1 saturation voltage drop only has about 0.07V under this small area analysis (maximum collector current is 650V/10M Ω=65uA), at this moment require that the voltage stabilizing value of voltage stabilizing didoe D3 is at below 2.93V, this 3.3V of being less than voltage-stabiliser tube is more difficult to be looked for, generally can adopt the replacement scheme shown in Figure 13, obtain with after 2 to 5 1N4148 Diode series, under 100uA to 200uA small area analysis, the pressure drop of a 1N4148 diode is 0.46V to 0.50V, and 2 to 5 1N4148 Diode series can obtain the voltage stabilizing value of 0.92V to 2.5V.

When DC voltage average value is less than the first preset value, the terminal voltage of electric capacity C4 is after resistance R1 and resistance R2 dividing potential drop, be not enough to cause NPN type triode T1 conducting, NPN type triode T1 is in cut-off state, its current collection very high level, and the voltage of plus end 104 is added to the grid of metal-oxide-semiconductor T2 through resistance R3, the complete conducting of metal-oxide-semiconductor T2, electric capacity C2 place in circuit, electric capacity C2 and electric capacity C1 is in parallel, gives rectification circuit 100 filtering together.

When DC voltage average value is more than the first preset value, the terminal voltage of electric capacity C4 is after resistance R1 and resistance R2 dividing potential drop, when the actual voltage stabilizing value reaching voltage stabilizing didoe D3 adds NPN type triode T1 saturation voltage drop, NPN type triode T1 conducting, NPN type triode T1 is in saturation conduction state, between its collector electrode to negative terminal 105, voltage is that the actual voltage stabilizing value of voltage stabilizing didoe D3 adds NPN type triode T1 saturation voltage drop, is less than the cut-in voltage V of grid to source electrode of metal-oxide-semiconductor T2 _gS, metal-oxide-semiconductor T2 not conducting completely, is in open-circuit condition, and electric capacity C2 is inoperative in circuit, does not bear higher magnitude of voltage more withstand voltage than self, only has electric capacity C1 to strobe.

Below, with one group of real data, the beneficial effect that the present invention brings is described, in Figure 12 circuit, resistance R1 is 3.9M Ω, resistance R2 is 56K Ω, resistance R3 is 10M Ω, resistance R4, resistance R5 is 3.9M Ω, electric capacity C4 is the CBB electric capacity of 682/630V, NPN type triode T1 is 2N3904, the metal-oxide-semiconductor T2 of N raceway groove is 2SK3532, voltage stabilizing didoe D2 is 0.5W10V voltage-stabiliser tube, voltage stabilizing didoe D3 is that 5 1N4148 series connection obtain, to be 22uF/400V electric capacity to connect gained by Fig. 6 electric capacity C1, capacity after series connection is 11uF, brand is all the homologous series electric capacity of Japanese NCC, electric capacity C2 is the 100uF/400V electrochemical capacitor of same brand.

After circuit welds, surveying the first preset value is about 404V, and regulating resistance R1 or R2 or R4 can regulate the value of the first preset value, due within ± 3% precision, does not just adjust.Actual measurement is under different voltage, and the filter capacity that circuit of the present invention provides is identical with upper table four:

Cost in background technology is 17.6 yuan, and owing to increasing some elements, cost is 9.70 yuan, is more or less the same, and the cost of table three still has reference significance.

Therefore the 3rd embodiment still can realize goal of the invention.

In the circuit of Figure 12, resistance R4 is changed to a diode, and circuit will become the first working method: the peak value detecting the direct voltage between plus end and negative terminal, equally can realize finding object.

First embodiment to the 3rd embodiment is all employing switch control rule, is all based on metal-oxide-semiconductor in embodiment, in fact, is changed to bidirectional triode thyristor and equally can realizes goal of the invention.

4th embodiment

Figure 14 shows the theory diagram of the 4th embodiment, is the theory diagram drawn according to improved technique scheme of the present invention;

Figure 15 shows the schematic diagram of the 4th embodiment, in Figure 15 200 partially illustrates the concrete schematic diagram of fourth embodiment of the invention, its annexation observes the relation in technical scheme completely, comprise plus end 104 and negative terminal 105, comprise voltage detecting and controling circuit 102, one first electric capacity C1, one second electric capacity C2, one the 3rd electric capacity C3, one first switch 103, second switch 109; The withstand voltage of second electric capacity C2 and C3 is less than the withstand voltage of the first electric capacity C1; Voltage detecting and controling circuit 102 comprises four ports, and voltage detecting input is positive 106, negative 107, first output 108, second output 110 of voltage detecting input; Plus end 104 connects the voltage detecting input positive 106 of voltage detecting and controling circuit 102, and plus end 104 also connects one end (electrochemical capacitor positive pole) of one end (electrochemical capacitor positive pole) of the first electric capacity C1 and one end (electrochemical capacitor positive pole) of the second electric capacity C2 and the 3rd electric capacity C3 simultaneously; Negative terminal 105 connects the voltage detecting input negative 107 of voltage detecting and controling circuit 102, and negative terminal 105 also connects the other end (electrochemical capacitor negative pole) of the first electric capacity C1 simultaneously, and one end of the first switch 103 and one end of second switch 109; The other end of the first switch 103 connects the other end (electrochemical capacitor negative pole) of the second electric capacity C2; The other end of second switch 109 connects the other end (electrochemical capacitor negative pole) of the 3rd electric capacity C3; Voltage detecting input positive 106 is returned voltage detecting and controling circuit 102 simultaneously and is powered.

Voltage detecting and controling circuit 102 in the present embodiment, is the second working method, for detecting the mean value of the direct voltage between plus end and negative terminal.

Voltage detecting and controling circuit 102 comprises: resistance R1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, resistance R8, electric capacity C4, voltage stabilizing didoe D3, NPN type triode T1, NPN type triode T3, the annexation of voltage detecting and controling circuit 102 is: one end of resistance R4 one end contact resistance R3, contact resistance R5 simultaneously, one end of resistance R8, tie point coating-forming voltage detects input positive 106, one end of resistance R4 other end contact resistance R1, connect one end of electric capacity C4 and one end of resistance R6 simultaneously, one end of the other end contact resistance R2 of resistance R1, its tie point connects the base stage of NPN type triode T1 simultaneously, the emitter of NPN type triode T1 connects the negative electrode of voltage stabilizing didoe D3, and tie point is the other end of contact resistance R5 and the emitter of NPN type triode T3 simultaneously, the other end of the anode contact resistance R2 of voltage stabilizing didoe D3, connects the other end of electric capacity C4 simultaneously, and tie point coating-forming voltage detects input negative 107, the other end of the collector electrode contact resistance R3 of NPN type triode T1, tie point forms the first output 108, one end of the other end contact resistance R7 of resistance R6, its tie point connects the base stage of NPN type triode T3 simultaneously, the other end of resistance R7 is connected to the anode of voltage stabilizing didoe D3, the other end of the collector electrode contact resistance R8 of NPN type triode T3, tie point forms the second output 110.

First switch 103, with the first embodiment, no longer describes in detail here; Second switch 109 in the present embodiment, main body is the metal-oxide-semiconductor T4 of a N raceway groove, with a voltage stabilizing didoe D4, the grid of metal-oxide-semiconductor T4 directly connects the second output 110 of voltage detecting and controling circuit 102, connect the negative electrode of voltage stabilizing didoe D4 simultaneously, the source electrode of metal-oxide-semiconductor T4 connects the anode of voltage stabilizing didoe D4, form one end of second switch 109, and connect negative terminal 105, the drain electrode of metal-oxide-semiconductor T4 is exactly the other end of previously described second switch 109, connects the other end (electrochemical capacitor negative pole) of the 3rd electric capacity C3.

In second switch 109, the voltage stabilizing value of voltage stabilizing didoe D3 adds that NPN type triode T1 saturation voltage drop requires to be less than grid, the source electrode cut-in voltage V of metal-oxide-semiconductor T2 and T3 _gS.

According to technical scheme, the second preset value is lower than the magnitude of voltage of the first preset value.The operation principle of the first switch 103, second switch 109 implements operation principle relevant in embodiment with first.

When direct voltage is less than the second preset value, the first switch 103 and second switch 109 all conductings, the first electric capacity C1, the second electric capacity C2, the whole place in circuit of the 3rd electric capacity C3, filter circuit of the present invention obtains maximum filter capacity.

And when direct voltage is more than the second preset value, when being less than the first preset value, the first switch 103 conducting, second switch 109 disconnects, the first electric capacity C1, the second electric capacity C2 place in circuit, and withstand voltage the 3rd minimum electric capacity C3 is disconnected; Filter action is still born by withstand voltage the first the highest electric capacity C1, withstand voltage the second higher electric capacity C2 parallel connection, at this moment because direct voltage is higher, does not need maximum filter capacity, and whole switching power circuit still can comparatively good berth.

And when direct voltage is more than the first preset value, the first switch 103, second switch 109 disconnect, and withstand voltage the second lower electric capacity C2, withstand voltage the 3rd minimum electric capacity C3 are all disconnected; Filter action is still born by withstand voltage the first higher electric capacity C1, at this moment because direct voltage is very high, only needs very little filter capacity, and whole switching power circuit still can comparatively good berth.

Below, with one group of real data, the beneficial effect that the present invention brings is described, in Figure 15 circuit, resistance R1, resistance R5, resistance R6 is 3.9M Ω, resistance R2 is 56K Ω, resistance R7 is 100K Ω, resistance R3, resistance R8 is 10M Ω, resistance R4 is 2M Ω, electric capacity C4 is the CBB electric capacity of 223/630V, NPN type triode T1, T3 is 2N3904, the metal-oxide-semiconductor T2 of N raceway groove, T4 is 2SK3532, voltage stabilizing didoe D2, D4 is 0.5W10V voltage-stabiliser tube, voltage stabilizing didoe D3 is that 5 1N4148 series connection obtain, to be 22uF/400V electric capacity to connect gained by Fig. 6 electric capacity C1, capacity after series connection is 11uF, brand is all the homologous series electric capacity of Japanese NCC, electric capacity C2 is also the 22uF/400V electrochemical capacitor of same brand, electric capacity C3 is that 68uF/250V is with brand electrochemical capacitor.

After circuit welds, surveying the first preset value is about 399V, and the second preset value is about 224V, and regulating resistance R1 or R2, R6 or R7 can regulate the value of the first preset value, the second preset value respectively.I.e. terminal voltage U _lwhen being less than 224V, filter capacity is 68uF+22uF+11uF=101uF; Terminal voltage U _lwhen more than 224V, when being less than 399V, filter capacity is 22uF+11uF=101uF; Terminal voltage U _lwhen more than 399V, filter capacity is 11uF; Survey under different voltage, the filter capacity that circuit of the present invention provides and following table five:

Table five

Can see from upper table, the present invention in extremely wide voltage range, all than the C calculated _lcapacity minimum value wants large, can meet user demand completely.

Cost in background technology is 17.6 yuan, owing to increasing some elements, then looks at the total cost of circuit of the present invention, see table six:

Table six

As can be seen from Table V, cost drops to 10.12 yuan from 17.6 yuan, and cost of the present invention is 57.5% of the cost in background technology, have dropped 42.5%.

Therefore the 4th embodiment still can realize goal of the invention.

In the circuit of Figure 15, resistance R4 is changed to a diode, and circuit will become the first working method: the peak value detecting the direct voltage between plus end and negative terminal, equally can realize goal of the invention.

In fact, when the present invention is used in Switching Power Supply, the accessory power supply that Switching Power Supply can be utilized to power to main control chip is completely powered to relay, simultaneously, can detect voltage with this adjustable accurate shunt regulator of TL431, be the circuit shown in the 5th embodiment, the 6th embodiment with regard to this.

5th embodiment

200 schematic diagrams partially illustrating the 5th embodiment in Figure 16, with the first embodiment unlike, one end (111 in figure) of R3 is originally and is connected plus end 104, now change into and be connected on accessory power supply that Switching Power Supply powers to main control chip, accessory power supply magnitude of voltage UA is generally between 7V to 28V, as widely popular quasi-resonance scheme NCP1336, its accessory power supply is 15V to 28V, different depending on different main control chips.

NPN type triode T1 is replaced by IC1, and IC1 is this adjustable accurate shunt regulator of TL431, is also a kind of integrated circuit, and it has three pins: anode A, negative electrode K, reference edge R.Replace emitter, collector electrode, the base stage of NPN type triode T1 respectively.

Other annexation with the first embodiment, is said completely here no longer in detail.The ratio of regulating resistance R1 and R2, makes when the first preset value, and the voltage of the reference edge R of integrated circuit (IC) 1 is the reference voltage of nominal, is generally about 2.50V, notes: the TL431 also having the model of about 1.25V.

As input voltage U _aCwhen the direct voltage produced is less than the first preset value, the voltage of the reference edge R of integrated circuit (IC) 1 is less than the reference voltage 2.50V of nominal, and at this moment the negative electrode K of integrated circuit (IC) 1 only consumes the electric current of below 0.4mA, and resistance R3 can choose like this:

$R3\≤\frac{U_A-U_{D2}}{0.4\mathrm{mA}}$ Formula (6)

Wherein, U _afor accessory power supply magnitude of voltage, U _d2for the voltage stabilizing value of voltage stabilizing didoe D2,0.4mA is the minimum working current of TL431, and the TL431 minimum working current of different manufacturers is slightly different, can adjust this value of 0.4mA and again substitute into formula (6).

At this moment because integrated circuit (IC) 1 consumes the electric current of below 0.4mA, voltage stabilizing didoe D2 is in the state by voltage stabilizing substantially, if resistance R3 gets a little bit smaller, voltage stabilizing didoe D2 is in the state of voltage stabilizing, so at this moment the grid of metal-oxide-semiconductor T2 to source electrode because voltage is high, metal-oxide-semiconductor T2 conducting, electric capacity C2 place in circuit.

As input voltage U _aCthrough rectification produce direct voltage more than the first preset value time, the voltage of the reference edge R of integrated circuit (IC) 1 is greater than the reference voltage 2.50V of nominal, at this moment the negative electrode K of integrated circuit (IC) 1 consumes very large electric current, this electric current is until negative electrode K drops to 2.50V just settles out, and this is the inherent characteristic of TL431.So at this moment, the grid of metal-oxide-semiconductor T2 is to source voltage due to ability 2.50V, and lower than cut-in voltage, metal-oxide-semiconductor T2 not conducting, electric capacity C2 does not participate in filtering.

If the grid of metal-oxide-semiconductor T2 is to the cut-in voltage of source electrode cut-in voltage lower than 2.5V, the reference voltage of the nominal of the reference edge of integrated circuit (IC) 1 chooses model corresponding to 1.25V.

Equally, if the resistance R3 constant current tube of several milliamperes, constant-current circuit replace, the operating power consumption of circuit reduces further.

Circuit in this example is improved slightly, substitutes metal-oxide-semiconductor T2 with relay, Here it is the circuit shown in the 6th embodiment.

6th embodiment

200 schematic diagrams partially illustrating the 6th embodiment in Figure 17, with the 5th embodiment unlike, the normally-closed contact of relay R LY instead of drain electrode and the source electrode of former metal-oxide-semiconductor, resistance R9 and PNP type triode T5 in parallel connection on resistance R3, the emitter of PNP type triode T5 connects 111 ends, base stage connects the negative electrode K of integrated circuit (IC) 1 by resistance R9, current collection very first output 108 of PNP type triode T5, connect the coil windings of relay R LY, the input of the other end connection rectification circuit 100 of coil windings is born, i.e. negative terminal 105, also be the ground wire of accessory power supply.

As input voltage U _aCwhen the direct voltage produced is less than the first preset value, the voltage of the reference edge R of integrated circuit (IC) 1 is less than the reference voltage 2.50V of nominal, at this moment the negative electrode K of integrated circuit (IC) 1 only consumes the electric current of below 0.4mA, resistance R3 obtains less, guarantee PNP type triode T5 not conducting, at this moment relay R LY not adhesive, its normally-closed contact is in connected state, electric capacity C2 place in circuit;

As input voltage U _aCwhen the direct voltage produced is more than the first preset value, the voltage of the reference edge R of integrated circuit (IC) 1 is greater than the reference voltage 2.50V of nominal, at this moment the negative electrode K of integrated circuit (IC) 1 consumes very large electric current, and this electric current is until negative electrode K drops to 2.50V just settles out.So at this moment, very large in the pressure drop of resistance R3 generation, first choose suitable R9, guarantee that the output current of PNP type triode T5 is enough to drive relay R LY action, after relay R LY adhesive, at this moment the normally-closed contact of relay R LY is in off-state, and electric capacity C2 does not participate in filtering.

Thus realize object of the present invention.Generally, a coil windings meeting upper diode in parallel of relay R LY is for absorbing the high pressure of relay R LY generation when discharging; Also can seal in NTC thermistor in its normally-closed contact, prevent the surge impact electric current produced when being incorporated to circuit or being disconnected from the circuit at electric capacity.

Below be only the preferred embodiment of the present invention, it should be noted that, above-mentioned preferred implementation should not be considered as limitation of the present invention, for those skilled in the art, adding different control strategies and voltage detecting strategy in the basic topology of circuit of the present invention, as the low-voltage by accessory power supply, voltage is detected with operational amplifier, various similar circuit can be obtained further, adapt to other operational environment, without departing from the spirit and scope of the present invention, some improvements and modifications can also be made, these improvements and modifications also should be considered as protection scope of the present invention, here no longer repeat by embodiment, protection scope of the present invention should be as the criterion with claim limited range.

Claims (17)

1. a filter circuit, comprise the first electric capacity (C1), the two ends of this first electric capacity (C1) are respectively plus end and the negative terminal of filter circuit, DC input voitage is from the plus end of filter circuit, negative terminal access, and described filter circuit also comprising the first switch (K1), being withstand voltagely less than second electric capacity (C2) of described first electric capacity (C1) and the voltage detecting and controling circuit (102) for detecting described DC input voitage, described second electric capacity (C2) and the first switch (K1) are in series, this series arm and described first electric capacity (C1) are in parallel, described voltage detecting and controling circuit (102) has voltage detecting input positive pole, voltage detecting input negative pole and the first output, the voltage detecting input positive pole of voltage detecting and controling circuit (102) is connected with the plus end of filter circuit, voltage detecting input negative pole is connected with the negative terminal of filter circuit, first output is connected to the control end of the first switch (K1), described voltage detecting and controling circuit (102) is provided with the first preset value, and when detecting that DC input voitage is less than the first preset value, control the first switch (K1) conducting, when detecting that DC input voitage is more than the first preset value, controlling the first switch (K1) and disconnecting,

It is characterized in that: described voltage detecting and controling circuit (102) comprising: the first resistance (R1), second resistance (R2), 3rd resistance (R3), 4th electric capacity (C4), first diode (D1), first NPN type triode (T1), one end of the 3rd resistance (R3) described in the anode that the annexation of described voltage detecting and controling circuit (102) is: described the first diode (D1) connects, the tie point of the first diode (D1) and the 3rd resistance (R3) forms described voltage detecting input positive pole, one end of first resistance (R1) described in negative electrode connection of described the first diode (D1), connect one end of the 4th described electric capacity (C4) simultaneously, one end of second resistance (R2) described in other end connection of described the first resistance (R1), its tie point connects the base stage of described the first NPN type triode (T1) simultaneously, the other end of second resistance (R2) described in emitter connection of described the first NPN type triode (T1), connect the other end of the 4th described electric capacity (C4), the emitter of the first NPN type triode (T1) and the tie point of the 4th electric capacity (C4) form described voltage detecting input negative pole simultaneously, the other end of the 3rd resistance (R3) described in collector electrode connection of described the first NPN type triode (T1), the tie point of the first NPN type triode (T1) and the 3rd resistance (R3) forms the first described output.

2. filter circuit according to claim 1, is characterized in that: described voltage detecting and controling circuit (102) detects voltage peak or the average voltage of described DC input voitage.

3. filter circuit according to claim 1, it is characterized in that: described voltage detecting and controling circuit (102) obtains power supply by the DC input voitage of input filter circuit, or obtained by the accessory power supply of the rear class Switching Power Supply be connected with filter circuit and power.

4. filter circuit according to claim 1, is characterized in that: described first switch (K1) is metal-oxide-semiconductor (T2).

5. filter circuit according to claim 1, is characterized in that: described first switch (K1) is relay (PLY).

6. a filter circuit, comprise the first electric capacity (C1), the two ends of this first electric capacity (C1) are respectively plus end and the negative terminal of filter circuit, DC input voitage is from the plus end of filter circuit, negative terminal access, and described filter circuit also comprising the first switch (K1), being withstand voltagely less than second electric capacity (C2) of described first electric capacity (C1) and the voltage detecting and controling circuit (102) for detecting described DC input voitage, described second electric capacity (C2) and the first switch (K1) are in series, this series arm and described first electric capacity (C1) are in parallel, described voltage detecting and controling circuit (102) has voltage detecting input positive pole, voltage detecting input negative pole and the first output, the voltage detecting input positive pole of voltage detecting and controling circuit (102) is connected with the plus end of filter circuit, voltage detecting input negative pole is connected with the negative terminal of filter circuit, first output is connected to the control end of the first switch (K1), described voltage detecting and controling circuit (102) is provided with the first preset value, and when detecting that DC input voitage is less than the first preset value, control the first switch (K1) conducting, when detecting that DC input voitage is more than the first preset value, controlling the first switch (K1) and disconnecting,

It is characterized in that: described voltage detecting and controling circuit (102) comprising: the first resistance (R1), second resistance (R2), 3rd resistance (R3), 4th resistance (R4), 4th electric capacity (C4), first NPN type triode (T1), the annexation of described voltage detecting and controling circuit 102 is the one end of the 3rd resistance (R3) described in the 4th described resistance (R4) one end connects, the tie point of the 4th resistance (R4) and the 3rd resistance (R3) forms described voltage detecting input positive pole, one end of the first resistance (R1) described in the 4th described resistance (R4) other end connects, connect one end of the 4th described electric capacity (C4) simultaneously, one end of second resistance (R2) described in other end connection of described the first resistance (R1), its tie point connects the base stage of described the first NPN type triode (T1) simultaneously, the other end of second resistance (R2) described in emitter connection of described the first NPN type triode (T1), connect the other end of the 4th described electric capacity (C4), the tie point of the second resistance (R2) and the 4th electric capacity (C4) forms described voltage detecting input negative pole simultaneously, the other end of the 3rd resistance (R3) described in collector electrode connection of described the first NPN type triode (T1), the tie point of the first NPN type triode (T1) and the 3rd resistance (R3) forms the first described output.

7. filter circuit according to claim 6, is characterized in that: described voltage detecting and controling circuit (102) also comprises the 5th resistance (R5) and the first voltage stabilizing didoe (D3); Described 5th resistance (R5) is connected between the voltage detecting input positive pole of voltage detecting and controling circuit (102) and the emitter of the first NPN type triode (T1), the emitter of described first NPN type triode (T1) is connected with the second resistance (R2) by the first voltage stabilizing didoe (D3), and wherein the emitter of the first NPN type triode (T1) is connected with the negative electrode of the first voltage stabilizing didoe (D3).

8. filter circuit according to claim 6, is characterized in that: described voltage detecting and controling circuit (102) detects voltage peak or the average voltage of described DC input voitage.

9. the filter circuit according to claim 6 or 7, it is characterized in that: described voltage detecting and controling circuit (102) obtains power supply by the DC input voitage of input filter circuit, or obtained by the accessory power supply of the rear class Switching Power Supply be connected with filter circuit and power.

10. the filter circuit according to claim 6 or 7, is characterized in that: described first switch (K1) is metal-oxide-semiconductor (T2).

11. filter circuits according to claim 6 or 7, is characterized in that: described first switch (K1) is relay (PLY).

12. 1 kinds of filter circuits, comprise the first electric capacity (C1), the two ends of this first electric capacity (C1) are respectively plus end and the negative terminal of filter circuit, DC input voitage is from the plus end of filter circuit, negative terminal access, and described filter circuit also comprising the first switch (K1), being withstand voltagely less than second electric capacity (C2) of described first electric capacity (C1) and the voltage detecting and controling circuit (102) for detecting described DC input voitage, described second electric capacity (C2) and the first switch (K1) are in series, this series arm and described first electric capacity (C1) are in parallel, described voltage detecting and controling circuit (102) has voltage detecting input positive pole, voltage detecting input negative pole and the first output, the voltage detecting input positive pole of voltage detecting and controling circuit (102) is connected with the plus end of filter circuit, voltage detecting input negative pole is connected with the negative terminal of filter circuit, first output is connected to the control end of the first switch (K1), described voltage detecting and controling circuit (102) is provided with the first preset value, and when detecting that DC input voitage is less than the first preset value, control the first switch (K1) conducting, when detecting that DC input voitage is more than the first preset value, controlling the first switch (K1) and disconnecting,

It is characterized in that: described filter circuit also comprises second switch (K2) and withstand voltage the 3rd electric capacity (C3) being less than described second electric capacity (C2), described second switch (K2) and the 3rd electric capacity (C3) are in series, series arm and described first electric capacity (C1) of second switch (K2) and the 3rd electric capacity (C3) are in parallel, described voltage detecting and controling circuit (102) also has the second output, second output of voltage detecting and controling circuit (102) is connected to the control end of second switch (K2), described voltage detecting and controling circuit (102) is also provided with the second preset value being less than described first preset value, and when detecting that DC input voitage is less than the second preset value, control second switch (K2) conducting, when detecting that DC input voitage is more than the second preset value, controlling second switch (K2) and disconnecting.

13. filter circuits according to claim 12, it is characterized in that: described voltage detecting and controling circuit (102) comprising: the first resistance (R1), second resistance (R2), 3rd resistance (R3), 4th resistance (R4), 5th resistance (R5), 6th resistance (R6), 7th resistance (R7), 8th resistance (R8), 4th electric capacity (C4), first voltage stabilizing didoe (D3), first NPN type triode (T1), second NPN type triode (T3), the annexation of described voltage detecting and controling circuit (102) is the one end of the 3rd resistance (R3) described in the 4th described resistance (R4) one end connects, connect the 5th described resistance (R5) simultaneously, one end of the 8th described resistance (R8), the tie point of the 4th resistance (R4) and the 3rd resistance (R3) forms described voltage detecting input positive pole, one end of the first resistance (R1) described in the 4th described resistance (R4) other end connects, connect one end of the 4th described electric capacity (C4) and one end of the 6th described resistance (R6) simultaneously, one end of second resistance (R2) described in other end connection of described the first resistance (R1), its tie point connects the base stage of described the first NPN type triode (T1) simultaneously, the negative electrode of first voltage stabilizing didoe (D3) described in emitter connection of described the first NPN type triode (T1), tie point connects the other end of the 5th described resistance (R5) and the emitter of described the second NPN type triode (T3) simultaneously, the other end of second resistance (R2) described in anode connection of described the first voltage stabilizing didoe (D3), connect the other end of the 4th described electric capacity (C4), the tie point of the first voltage stabilizing didoe (D3) and the second resistance (R2) forms described voltage detecting input negative pole simultaneously, the other end of the 3rd resistance (R3) described in collector electrode connection of described the first NPN type triode (T1), the tie point of the first NPN type triode (T1) and the 3rd resistance (R3) forms the first described output, one end of the 7th resistance (R7) described in other end connection of the 6th described resistance (R6), its tie point connects the base stage of described the second NPN type triode (T3) simultaneously, the other end of the 7th described resistance (R7) is connected to the anode of described the first voltage stabilizing didoe (D3), the other end of the 8th resistance (R8) described in collector electrode connection of described the second NPN type triode (T3), the tie point of the second NPN type triode (T3) and the 8th resistance (R8) forms the second described output.

14. filter circuits according to claim 12, is characterized in that: described voltage detecting and controling circuit (102) detects voltage peak or the average voltage of described DC input voitage.

15. filter circuits according to claim 12 or 13, it is characterized in that: described voltage detecting and controling circuit (102) obtains power supply by the DC input voitage of input filter circuit, or obtained by the accessory power supply of the rear class Switching Power Supply be connected with filter circuit and power.

16. filter circuits according to claim 12 or 13, is characterized in that: described first switch (K1) and second switch (K2) are metal-oxide-semiconductor (T2).

17. filter circuits according to claim 12 or 13, is characterized in that: described first switch (K1) and second switch (K2) are relay (PLY).