CN1881769A - Switch power supply capable of filtering industrial frequency noise in floating system - Google Patents
Switch power supply capable of filtering industrial frequency noise in floating system Download PDFInfo
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- CN1881769A CN1881769A CN 200510101935 CN200510101935A CN1881769A CN 1881769 A CN1881769 A CN 1881769A CN 200510101935 CN200510101935 CN 200510101935 CN 200510101935 A CN200510101935 A CN 200510101935A CN 1881769 A CN1881769 A CN 1881769A
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- industrial frequency
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Abstract
The invention relates to a switch power supply which can filter the industrial frequency noise of floating system, wherein based on traditional switch power supply, the invention eliminate the Y capacitor, to realize pure coil induction couple between the first coil and the secondary coil of transformer, to eliminate the transmission path of industrial frequency noise at the alternative current end to the secondary end; each rectify diode of rectify bridge is parallel connected to one capacitor, to reduce the aberration of alternative signal generated at the start and end of diode. With said invention, the industrial frequency noise of floating system can be filtered, to confirm the electromagnetic test of switch power meets the EMC standard.
Description
Technical field
The present invention relates to the Switching Power Supply in the electronic product, more particularly, relate to a kind of Switching Power Supply capable of filtering industrial frequency noise in floating system.
Background technology
At present, the supply unit that interchange can be converted to direct current has two kinds, i.e. linear power supply and Switching Power Supply.These two kinds of power supplys all can be introduced the common mode industrial frequency noise in floating neutral system.Wherein, electric capacity is less between the Transformer Winding of linear power supply, and isolation is good, therefore can reduce noise greatly, relative Switching Power Supply, and its noise is less.On the other hand, characteristics such as Switching Power Supply is portable and smart because of having, input voltage range is big, efficient height are so be widely used in the electronic system.For Switching Power Supply, because its transformer is less, design is complexity comparatively, and therefore relative linear power supply, filtering common mode industrial frequency noise are just relatively more difficult.So in Switching Power Supply design, how the industrial frequency noise of introducing in the filtering floating neutral system becomes an important problem.
For most of home-use electronic equipments (as television set, stereo set, telephone set, modulator-demodulator, set-top box etc.), floating ground (Floating) design has generally all been adopted in its power supply.That is to say: electronic equipment and its power supply circuits all do not have really to insert the earth, therefore, the common-mode noise that its power supply circuits can't filtering be introduced from AC-input voltage can will have very high common-mode noise to be incorporated in the direct voltage from the conversion of AC-to DC signal.Like this, the power frequency common-mode noise has just entered into electronic equipment fully, influences the normal use of equipment the most at last.
For example shown in Figure 1, in the IP phone voice system, at first need ac input signal is sent in the unearthed Switching Power Supply 101, because Switching Power Supply is unearthed, just have the industrial frequency noise of 50HZ in the direct voltage of output this moment, behind VoIP system 102, industrial frequency noise is introduced in the interface of telephone system 103,, will in microphone 1032, hear tangible industrial frequency noise at last because but most of phones 1031 do not add the circuit of high pass filter of filtering industrial frequency noise.
The operation principle of common Switching Power Supply meter as shown in Figure 2.Capacitor C among the figure is usually said Y electric capacity, AC signal can by this Y electric capacity from elementary be coupled to secondary.The Switching Power Supply that Fig. 2 has been shown among Fig. 3 is introduced the principle of common-mode noise, and C11 wherein and C12 are the junction capacitance in the rectification diode; C13 be primary and secondary between Y electric capacity; C14 is the equivalent capacity of output stage to the earth.Because of rectifying tube adopts same material device, so the value of C11 and C12 equates; Simultaneously, because of N phase line in the electrical network links to each other with the earth, so V1 point voltage relative to the earth is input voltage half, i.e. V1=Vin/2; Again since the capacitive reactance of C14 much larger than the capacitive reactance of C13, so V2 almost just equals V1.After the output of this Switching Power Supply connects load,, will make common-mode noise convert differential mode noise to, hear AC noise in phone, just can influence speech quality so will show to people's ear this moment because impedance does not match; In modulator-demodulator, then show as message transmission rate and descend, influence data transmission quality etc.
In the prior art, the industrial frequency noise of introducing for the Switching Power Supply floating neutral system does not have the method for complete filtering, and can only reduce, reduce noise by the following method.One of method be reduce first group and secondary between Y electric capacity, be delivered to secondary energy to lower elementary power-frequency voltage, but still can not reach desirable effect.Two of method changes elementary full-wave rectification into halfwave rectifier, as shown in Figure 4, though this method can reduce noise, full-wave rectification is revised as halfwave rectifier after, can cause the power work decrease in efficiency, and cause input voltage range constriction etc.As seen, these two kinds of methods all can only play improving effect, fully the industrial frequency noise that Switching Power Supply is introduced in the filtering floating neutral system.
Summary of the invention
At the above-mentioned defective of prior art, the present invention will solve the floating neutral system industrial frequency noise that only can reduce or reduce Switching Power Supply in the prior art, and problem that can't filtering floating neutral system industrial frequency noise.
For solving the problems of the technologies described above, technical scheme of the present invention is: a kind of Switching Power Supply capable of filtering industrial frequency noise in floating system is provided, comprises rectifier bridge, the transformer that is connected with the dc output end of described rectifier bridge and be serially connected with diverter switch in the described primary winding; Wherein, between the elementary winding of described transformer and the secondary winding be simple coil-induced coupling; Be parallel with electric capacity on each rectifying device in the described rectifier bridge.
Among the present invention, be preferably between the elementary winding of described transformer and the secondary winding and be provided with the screen that is used to intercept noise transfer.
Among the present invention, described rectifier bridge can be a full-wave rectification bridge, also can be the halfwave rectifier bridge.
By such scheme as can be known, the present invention is by the Y electric capacity in the deletion conventional switch power supply, and on rectifier diode and connect the mode of electric capacity, come the floating neutral system industrial frequency noise of filtering Switching Power Supply, this scheme can be with the effective filtering of floating neutral system industrial frequency noise of Switching Power Supply, thereby can eliminate the harmful effect of this noise like in electric equipment, to promote speech quality, data transmission quality etc.
Description of drawings
The invention will be further described below in conjunction with drawings and Examples, in the accompanying drawing:
Fig. 1 is the industrial frequency noise source schematic diagram in the existing voip phone system;
Fig. 2 is that the industrial frequency noise of the Switching Power Supply of existing way of full-wave rectification is introduced schematic diagram;
Fig. 3 is the conversion schematic diagram of Fig. 2;
Fig. 4 is the schematic diagram that available technology adopting halfwave rectifier mode reduces industrial frequency noise;
Fig. 5 is the schematic diagram of the Switching Power Supply in of the present invention.
Embodiment
As shown in Figure 5, in the Switching Power Supply capable of filtering industrial frequency noise in floating system of the present invention, comprise rectifier bridge, the transformer that is connected with the dc output end of rectifier bridge and be serially connected with diverter switch in the primary winding, be simple coil-induced coupling between the elementary winding of transformer and the secondary winding, be parallel with electric capacity on each rectifying device in the rectifier bridge.Rectifier bridge wherein can be full-wave rectification bridge or halfwave rectifier bridge, the best rectifier diode of rectification part.
As seen, the present invention has deleted Y electric capacity wherein on the basis of existing Switching Power Supply, with the primary that reduces Switching Power Supply and secondary between degree of coupling, improve the AC signal quality; Simultaneously, for fear of the distortion of signal, electric capacity all in parallel, i.e. C1 to C4 among Fig. 5 on each rectification part (being diode in the present embodiment) of rectification circuit.
Behind the Y electric capacity that removes between Switching Power Supply elementary and secondary, it between the elementary winding of transformer and the secondary winding simple coil-induced coupling, no longer include the coupling that Y electric capacity is brought, so it is secondary that the industrial frequency noise of interchange end does not have approach to pass to, so just do not have the industrial frequency noise of 50Hz between its output voltage and the ground again, thereby can not be created in the IP telephony system counter productives such as speed that can influence the call voice quality, in modulator-demodulator, then can influence transfer of data again.
On the other hand since on each rectifier diode of rectification circuit electric capacity in parallel, so can reduce that diode is opened and when ending and the distortion of the AC signal that produces.If there is not this electric capacity, the noise between output voltage and the ground will have severe distortion, thereby can produce differential mode noise at two inter-stages of output voltage.
In order to better meet the requirement of Switching Power Supply, in the present invention, preferably also take following measure to EMC (electromagnetic compatibility) index:
1, reduce primary and secondary between coupling, for example, be used for intercepting secondary noise and pass to elementary by between the primary and secondary winding of transformer, increasing screen.
2, the switching frequency of Switching Power Supply can not be too high, and switch conduction and time of ending are slowed down as far as possible, to reduce di/dt (variable quantity of electric current in the unit interval), can reduce signal to noise ratio like this.
3, as far as possible the loop area that radio circuit is shared is designed into minimum, so just can reduce harmful effect that alternating magnetic field causes owing to the alternating current generation by reducing loop area.
Claims (4)
1, a kind of Switching Power Supply capable of filtering industrial frequency noise in floating system comprises rectifier bridge, the transformer that is connected with the dc output end of described rectifier bridge and is serially connected with diverter switch in the described primary winding; It is characterized in that,
It between the elementary winding of described transformer and the secondary winding simple coil-induced coupling;
Be parallel with electric capacity on each rectifying device in the described rectifier bridge.
2, Switching Power Supply capable of filtering industrial frequency noise in floating system according to claim 1 is characterized in that, is provided with the screen that is used to intercept noise transfer between the elementary winding of described transformer and secondary winding.
3, Switching Power Supply capable of filtering industrial frequency noise in floating system according to claim 1 and 2 is characterized in that, described rectifier bridge is a full-wave rectification bridge.
4, Switching Power Supply capable of filtering industrial frequency noise in floating system according to claim 1 and 2 is characterized in that, described rectifier bridge is the halfwave rectifier bridge.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510101935 CN1881769A (en) | 2005-11-28 | 2005-11-28 | Switch power supply capable of filtering industrial frequency noise in floating system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200510101935 CN1881769A (en) | 2005-11-28 | 2005-11-28 | Switch power supply capable of filtering industrial frequency noise in floating system |
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| Publication Number | Publication Date |
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| CN1881769A true CN1881769A (en) | 2006-12-20 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200510101935 Pending CN1881769A (en) | 2005-11-28 | 2005-11-28 | Switch power supply capable of filtering industrial frequency noise in floating system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009005560A3 (en) * | 2007-06-28 | 2009-04-16 | Apple Inc | Systems and methods for impedance stabilization |
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2005
- 2005-11-28 CN CN 200510101935 patent/CN1881769A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2009005560A3 (en) * | 2007-06-28 | 2009-04-16 | Apple Inc | Systems and methods for impedance stabilization |
| CN101689813A (en) * | 2007-06-28 | 2010-03-31 | 苹果公司 | systems and methods for impedance stabilization |
| US8456450B2 (en) | 2007-06-28 | 2013-06-04 | Apple Inc. | Systems and methods for impedance stabilization |
| CN101689813B (en) * | 2007-06-28 | 2013-11-13 | 苹果公司 | Systems and methods for impedance stabilization |
| CN103532403A (en) * | 2007-06-28 | 2014-01-22 | 苹果公司 | Systems and methods for impedance stabilization |
| CN103532403B (en) * | 2007-06-28 | 2016-04-13 | 苹果公司 | For the system and method for impedance stabilization |
| US9325253B2 (en) | 2007-06-28 | 2016-04-26 | Apple Inc. | Systems and methods for impedance stabilization |
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