CN101651411A - Frequency jittering system and frequency jittering method - Google Patents
Frequency jittering system and frequency jittering method Download PDFInfo
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Abstract
The invention discloses a frequency jittering system and a frequency jittering method. The frequency jittering system comprises an oscillator, a weighting operation module and a digital-to-analog converter, wherein the oscillator is used for outputting and generating a plurality of digital sequences; each digital sequence comprises a periodic sequence and a pseudorandom sequence; the weighting operation module is connected with the oscillator and used for carrying out weighting operation on a plurality of digital sequences; the digital-to-analog converter is connected with the weighting operation module and the oscillator and used for converting an output signal of the weighting operation module into an analog signal, and the analog signal is used for controlling the frequency of the oscillator. The frequency jittering system and the frequency jittering method generate frequency jittering in a mixing frequency jittering way and can provide a flexible and optimal frequency jittering wayfor the system.
Description
Technical field
The invention belongs to the integrated circuit (IC) design technical field, relate to a kind of frequency jitter system, relate in particular to a kind of frequency jitter system that can be used for Switching Power Supply; In addition, the invention still further relates to the frequency jitter method of said frequencies dithering system.
Background technology
Supply convertor is a requisite assembly in the electronic system.As everyone knows, power conversion rises and comprises linear transformations device and two kinds of main types of switching power converters.Most power consumption equipment all comprises internal electric source transducer or external power adapter, for example employed in the product such as TV and computer is the internal electric source transducer, what be widely used in fields such as mobile phone, DSL modulator-demodulator, printer, notebook computer and game machine is external power adapter, and these power supply changeover devices or adapter all are to adopt switch power converter so that the usefulness of power supply to be provided.Compare with the linear transformations device, switching power converters has characteristics such as volume is little, in light weight, efficient height.Yet, electromagnetic interference (the Electro-Magnetic Interference that Switching Power Supply self produces, EMI) signal takies very wide frequency band and stronger amplitude, by the conduction and the mode of radiation surrounding devices is produced electromagnetic interference if control improper meeting, pollute electromagnetic environment, become a very strong electromagnetic interference source.How to suppress or improve the electromagnetic interference of Switching Power Supply, make it to meet the requirement of relevant electromagnetic compatibility standard, become Switching Power Supply designer's a important topic.
See also Fig. 1, Fig. 1 has shown anti exciting converter (flybackconverter) system that is widely used in Switching Power Supply, and being used for exchanging (AC) changes direct current (DC).This system comprises: front end electromagnetic interface filter, full-bridge rectification, power controller, transformer, primary side MOS switch and current sense resistor, secondary commutation filtering, and isolated feedback compensating network.
Front end electromagnetic interface filter among Fig. 1 mainly is that the Conducted EMI of inhibition system produces interference by electrical network to other power consumption equipment, and this electromagnetic interface filter is wanted consumption rate bigger system cost, especially large-power occasions usually.In the small-power occasion, the system cost of switching power converters is the factor of producer of system overriding concern, if therefore adopt the less electromagnetic interface filter of build or take down it, system cost is descended significantly.
Frequency jitter (Frequency Jittering) or spread spectrum (Frequency Shuffling) technology have been widely used in the Conducted EMI performance that Switching Power Supply is improved system now.Patent and document about this respect are existing a lot, such as United States Patent (USP) 6,556,463,7,362,191, and Chinese patent 200680004174.9, or the like, enumerate no longer one by one at this.
Fig. 2 has shown the employing Controlled in Current Mode and Based and the power controller band frequency jittering function that can be applied in Fig. 1; main modular comprises: PWM comparator, slope-compensation, lead-edge-blanking, oscillator, frequency jitter; rest-set flip-flop; soft start; over-temperature protection (OTP); overcurrent protection (OCP), logical operation, and driving stage.The clock signal that oscillator produces offers rest-set flip-flop S end, the R end of logic output control rest-set flip-flop.Frequency jitter acts on system oscillator, produces frequency disturbance, thereby improves the Conducted EMI of system.
The thought of frequency jitter is exactly that frequency spectrum expands to dispersity with system from discrete state, and promptly the system works frequency is not to immobilize, but cycle or aperiodic, ground changed.Suppose that system's fundamental frequency amplitude of variation is Δ f, then secondary first-harmonic amplitude of variation is 2 Δ f ..., the N subharmonic is N Δ f, and visible harmonic number is high more, and frequency dispersion is just big more.Like this, the system frequency harmonic energy is dispersed, thereby certain peak value harmonic energy is descended, and is distributed to other frequency and gets on, and has guaranteed enough magnitude margins like this on whole frequency band, thereby has satisfied the EMI requirement.Now, a lot of power control chips are all integrated frequency jitter, and high efficient and reliable has also been saved system cost in addition significantly so on the one hand.
So far, in field of switch power, the implementation method of frequency jitter or spread spectrum roughly can be divided into two classes: a class is cline frequency shake or continuous frequency spectrum expansion.The oscillator frequency that the signal source of the outside variation of utilization is removed perturbed system, it is continuous that the signal of disturbing source changes.The shortcoming of this mode is that the signal spectrum excursion of disturbing source is limited, so overall frequency shake effect is not fine.Another kind of is to utilize oscillator to produce the stationary digital sequence, and then produces through digital to analog converter DAC (digital to analog converter) and to tremble frequently that signal comes the FEEDBACK CONTROL oscillator, trembles function frequently thereby finish, as shown in Figure 3.
Tremble mode frequently, implement simply, thereby be widely applied in the power controller now for above-mentioned second kind.
In the realization of trembling the frequency mode of above-mentioned employing stationary digital sequence, mainly be divided into two classes again: a class is that the stationary digital sequence is a pseudo random sequence, and pseudo random sequence comprises the M sequence, the Gold sequence, and Walsh sequence etc., its specific implementation is as shown in Figure 4.
The frequency system of trembling among Fig. 4 comprises oscillator, pseudo-random sequence generator, digital to analog converter.Wherein, pseudo-random sequence generator is N the linear negative feedback of register band, chooses the M position in its output and offers M position analog to digital converter as output.
Mode has individual shortcoming as trembling frequently to adopt the system described in Fig. 4: because its too whitening of pseudorandom series frequency spectrum, so can cause system's less stable.In view of this, a lot of switch power supply systems adopt the second class stationary digital periodic sequence, can adopt counter to tremble mode frequently in realization, as shown in Figure 5.
Counter is output as periodic signal, and generally extensive use is cycle triangular wave counting, its effect such as Fig. 6.
Fig. 5 and stationary digital periodic sequence shown in Figure 6 are trembled frequently, and mode has two defectives: (1) frequently is to repeat in the cycle owing to trembling, so the spread spectrum effect can descend comparatively speaking.(2) trembling frequently, the selective value of repetition period might produce conflict with system bandwidth.If it is very low to tremble frequently the repetition period, then might drops in the system bandwidth fully, thereby cause system not quite stable, even produce audible noise (audio noise).
Fig. 3 trembles frequently to stationary digital sequence shown in Figure 6, and mode also has two defectives: the first, and frequency spectrum shake effect is dumb.If because the shake mode is fixed, the spread spectrum effect of generation is also fixed, so when carrying out the EMI test, if certain Frequency point energy height, cause the EMI allowance very little, the then this mode of trembling frequently can't be regulated, can make so under many circumstances the EMI of system test can not get by.The second, the stationary digital sequence is trembled the frequency mode and also had a defective: frequency spectrum shake effect can not be regulated along with the size adaptation ground of system's power output., the frequency jitter amplitude need be increased at full load such as system, like this can be easily by the EMI of system test.When underloading, the frequency jitter amplitude need be reduced, stability improves in the time of can making system's underloading like this.Because system EMI test all is fully loaded basically, and system is less demanding to EMI on the one hand during underloading, stability all descends when making one side system underloading, and system is in discontinuous operation pattern (burst mode) when especially unloaded, and frequency jitter meeting at this moment worsens the stability of system.
In sum, it is all not fully up to expectations that all tremble the frequency mode so far, addresses the above problem so press for a kind of new system and method.
Summary of the invention
Technical problem to be solved by this invention is: a kind of frequency jitter system is provided, trembles the stable operation that mode frequently guarantees system by mixing.
In addition, the present invention also provides the frequency jitter method of said frequencies dithering system.
For solving the problems of the technologies described above, the present invention adopts following technical scheme:
A kind of frequency jitter system is used for the frequency jitter of control switching system; This frequency jitter system comprises:
Oscillator produces several digital sequences in order to output; In the described Serial No., comprise periodic sequence and pseudo random sequence;
The ranking operation module is connected with described oscillator, in order to described several digital sequences are done ranking operation;
Digital to analog converter is connected with described ranking operation module, oscillator, and in order to the output signal of described ranking operation module is converted to analog signal, this analog signal is used for controlling the frequency of described oscillator.
As a preferred embodiment of the present invention, described system also comprises the analog module that connects described digital to analog converter and oscillator; The input signal of this analog module is the continuous signal of the output and the output of direct or indirect representation switch power-supply system power of described digital to analog converter; Utilize described continuous signal to control the output of digital to analog converter, so that system increases in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
As a preferred embodiment of the present invention, described analog module is an analog multiplier.The signal of described direct or indirect representation switch power-supply system power output is the VDD of system feedback voltage VFB or power controller.
As a preferred embodiment of the present invention, described ranking operation module is done the simple digital addition to described several digital sequences.
A kind of frequency jitter method of said frequencies dithering system is characterized in that, this frequency jitter method comprises the steps:
A, the output of described oscillator produce several digital sequences; In the described Serial No., comprise periodic sequence and pseudo random sequence;
B, described ranking operation module are done ranking operation to described several digital sequences;
C, described digital to analog converter are converted to analog signal to the output signal of described ranking operation module, and this analog signal is used for controlling the frequency of described oscillator.
As a preferred embodiment of the present invention, described system also comprises the analog module that connects described digital to analog converter and oscillator; The input signal of this analog module is the continuous signal of the output and the output of direct or indirect representation switch power-supply system power of described digital to analog converter; Utilize described continuous signal to control the output of digital to analog converter, so that system increases in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
As a preferred embodiment of the present invention, described analog module is an analog multiplier; The signal of described direct or indirect representation switch power-supply system power output is the VDD of system feedback voltage VFB or power controller.
As a preferred embodiment of the present invention, described ranking operation module is done the simple digital addition to described several digital sequences; Each Serial No. is a periodic sequence, or is pseudo random sequence.
Beneficial effect of the present invention is: the frequency jitter system and method that the present invention proposes produces frequency jitter by the mixing mode frequently of trembling, for system provides flexibly, the mode frequently of trembling of the best.
The first, the present invention trembles mode frequently flexibly for system provides, and this is mainly realized by the weight coefficient of change Serial No. and the frequency of Serial No..Traditional mode frequently of trembling be fix and also be single, it trembles yupin effect also is single; So system might exist some Frequency point EMI allowance not enough when carrying out the EMI test.
The present invention trembles mode frequently by mixing, make the no longer unification of generation of Serial No., thereby in different sequences, can change the frequency and the weight coefficient of some sequence, thereby make spectrum energy homogenizing in whole frequency range of system, tremble the too little situation of the too high EMI allowance of some Frequency point energy that occurs in the frequency thereby the fixed sequence program mode no longer occurs.
The second, the present invention can provide the best mode frequently of trembling to system.As everyone knows, EMI tests mainly at full load, and EMI allowance with respect to fully loaded is bigger during underloading, so if the fully loaded EMI of system is by testing, underloading is generally also passed through easily.Traditional mode frequently of trembling adopts trembles frequently that amplitude is constant, and system owing to tremble and frequently can increase system's instability, especially is in discontinuous operation pattern (burst mode) during near zero load in system when underloading like this.So the best frequency mode of trembling is to tremble the frequency amplitude can regulate automatically with the system power size, at full load, trembling frequently, amplitude increases, easy like this system is tested by EMI, when underloading, reduce to tremble amplitude frequently, the stability of system when underloading is increased, as shown in Figure 9.In the present invention, by in system feedback voltage VFB or the VDD drawing-in system, thereby realize above-mentioned purpose, because the VDD of system feedback voltage VFB or power controller has represented the size of system power output directly or indirectly.
Description of drawings
Fig. 1 is the anti exciting converter system that is widely used in Switching Power Supply.
Employing Controlled in Current Mode and Based and power controller band frequency jittering function of Fig. 2 for being applied in Fig. 1.
Fig. 3 is an existing frequency jitter system.
Fig. 4 is an existing frequency jitter system.
Fig. 5 is an existing frequency jitter system.
Fig. 6 is output as periodic signal for counter.
A kind of frequency jitter system that Fig. 7 proposes for the present invention.
A kind of frequency jitter system that Fig. 8 proposes for the present invention.
A kind of frequency jitter system that Fig. 9 proposes for the present invention.
A kind of frequency jitter system that Figure 10 proposes for the present invention.
Figure 11 is the flow chart of frequency jitter method of the present invention.
Figure 12 trembles mode and traditional effect comparison schematic diagram of mode frequently of trembling frequently for the present invention.
Figure 13 trembles mode and traditional effect comparison schematic diagram of mode frequently of trembling frequently for the present invention.
Embodiment
Describe the preferred embodiments of the present invention in detail below in conjunction with accompanying drawing.
Embodiment one
See also Fig. 7, the present invention has disclosed a kind of frequency jitter system, and its thought is to mix to tremble frequently.This frequency jitter system is used for the frequency jitter of control switching system, and it comprises oscillator, ranking operation module, digital to analog converter.
Oscillator produces several digital sequences in order to output; In the described Serial No., comprise periodic sequence and pseudo random sequence.
The ranking operation module is connected with described oscillator, in order to described several digital sequences are done ranking operation.
Digital to analog converter is connected with described ranking operation module, oscillator, and in order to the output signal of described ranking operation module is converted to analog signal, this analog signal is used for controlling the frequency of described oscillator.
As a kind of implementation of the present invention, described ranking operation module can be done the simple digital addition to described several digital sequences.Perhaps, by weight coefficient is set; See also Fig. 8, a1-an is a weight coefficient.
More than introduced frequency jitter of the present invention system, the present invention has disclosed the frequency jitter method of said frequencies dithering system simultaneously.
See also Figure 11, this frequency jitter method comprises the steps:
A, the output of described oscillator produce several digital sequences; In the described Serial No., comprise periodic sequence and pseudo random sequence.
B, described ranking operation module are done ranking operation to described several digital sequences; As a kind of implementation of the present invention, described ranking operation module is done the simple digital addition to described several digital sequences.
C, described digital to analog converter are converted to analog signal to the output signal of described ranking operation module, and this analog signal is used for controlling the frequency of described oscillator.
Embodiment two
The difference of present embodiment and embodiment one is that in the present embodiment, described system also comprises the analog module that connects described digital to analog converter and oscillator; The input signal of this analog module is the continuous signal of the output and the output of direct or indirect representation switch power-supply system power of described digital to analog converter; Utilize described continuous signal to control the output of digital to analog converter, so that system increases in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
Fig. 9 is a kind of new frequency jitter system that proposes according to the present invention.Its thought is to mix to tremble continuously frequently and sequence is trembled frequency.With respect to the described frequency jitter of Fig. 7 system, this frequency jitter system has increased an analog module.
This analog module input signal is the output of certain continuous signal (direct or indirect representation switch power-supply system power output level) and digital to analog converter, and the output of this analog module is used for control generator.Utilize continuous signal (VDD of system feedback voltage VFB or power controller) to control the output of digital to analog converter, thereby system is increased in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
Among Fig. 9, oscillator output produces N Serial No., each sequence can be a periodic sequence, it also can be pseudo random sequence, ranking operation is done in N sequence output, and digital to analog converter is delivered in its output, and the analog module is delivered in the output of digital to analog converter, the analog module is gone back receiving system feedback voltage V FB or VDD simultaneously, and the output of analog module directly comes the control generator frequency.
Can see that by Fig. 9 the mixing that proposes of the present invention trembles the implication of mode frequently: the input signal of digital to analog converter is the hybrid digital sequence among the present invention, its generation computes weighted by N Serial No. and produces, and these Serial No.s can be cycle Serial No. or pseudo random sequence.Oscillator frequency of the present invention in addition can be modulated by system feedback voltage VFB or VDD, and VFB or VDD are the continuous analog signal.So being again the hybrid modulation of Serial No. and analog signal from the another one angle, the present invention realizes trembling frequently.
Specific embodiments of the invention can have a lot of mutation, such as shown in Figure 7, system can only adopt pure hybrid digital sequence to tremble frequently, do not modulate and there is the continuous analog signal, because in some cases, may there be stability problem in system's underloading, so for system simplification, can save the analog module.
In sum, the frequency jitter system and method that the present invention proposes produces frequency jitter by the mixing mode frequently of trembling, for system provides flexibly, the mode frequently of trembling of the best.
Advantage of the present invention mainly contains 2 points:
The first, for providing, system trembles mode frequently flexibly, and this is mainly realized by the weight coefficient of change Serial No. and the frequency of Serial No..Traditional mode frequently of trembling be fix and also be single, it trembles yupin effect also is single.So system might exist some Frequency point EMI allowance not enough when carrying out the EMI test, is illustrated in fig. 12 shown below.
Tremble mode frequently by mixing, make the no longer unification of generation of Serial No., thereby in different sequences, can change the frequency and the weight coefficient of some sequence, thereby make spectrum energy homogenizing in whole frequency range of system, tremble the too little situation of the too high EMI allowance of some Frequency point energy that occurs in the frequency thereby the fixed sequence program mode no longer occurs.
Another advantage of the present invention is: can provide the best mode frequently of trembling to system.As everyone knows, EMI tests mainly at full load, and EMI allowance with respect to fully loaded is bigger during underloading, so if the fully loaded EMI of system is by testing, underloading is generally also passed through easily.Traditional mode frequently of trembling adopts trembles frequently that amplitude is constant, and system owing to tremble and frequently can increase system's instability, especially is in discontinuous operation pattern (burst mode) during near zero load in system when underloading like this.So the best frequency mode of trembling is to tremble the frequency amplitude can regulate automatically with the system power size, at full load, trembling frequently, amplitude increases, easy like this system is tested by EMI, when underloading, reduce to tremble amplitude frequently, the stability of system when underloading is increased, as shown in figure 13.In the present invention, by in system feedback voltage VFB or the VDD drawing-in system, thereby realize above-mentioned purpose, because the VDD of system feedback voltage VFB or power controller has represented the size of system power output directly or indirectly.
Embodiment three
See also Figure 10, the difference of present embodiment and embodiment two is that in the present embodiment, described analog module can be analog multiplier.
Here description of the invention and application is illustrative, is not to want with scope restriction of the present invention in the above-described embodiments.Here the distortion of disclosed embodiment and change are possible, and the various parts of the replacement of embodiment and equivalence are known for those those of ordinary skill in the art.Those skilled in the art are noted that under the situation that does not break away from spirit of the present invention or substantive characteristics, and the present invention can be with other form, structure, layout, ratio, and realize with other assembly, material and parts.Under the situation that does not break away from the scope of the invention and spirit, can carry out other distortion and change here to disclosed embodiment.
Claims (9)
1, a kind of frequency jitter system is characterized in that, is used for the frequency jitter of control switching system; This frequency jitter system comprises:
Oscillator produces several digital sequences in order to output; In the described Serial No., comprise periodic sequence and pseudo random sequence;
The ranking operation module is connected with described oscillator, in order to described several digital sequences are done ranking operation;
Digital to analog converter is connected with described ranking operation module, oscillator, and in order to the output signal of described ranking operation module is converted to analog signal, this analog signal is used for controlling the frequency of described oscillator.
2, frequency jitter according to claim 1 system is characterized in that:
Described system also comprises the analog module that connects described digital to analog converter and oscillator;
The input signal of this analog module is the continuous signal of the output and the output of direct or indirect representation switch power-supply system power of described digital to analog converter;
Utilize described continuous signal to control the output of digital to analog converter, so that system increases in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
3, frequency jitter according to claim 2 system is characterized in that:
Described analog module is an analog multiplier.
4, frequency jitter according to claim 2 system is characterized in that:
The signal of described direct or indirect representation switch power-supply system power output is the VDD of system feedback voltage VFB or power controller.
5, according to the described frequency jitter of one of claim 1 to 4 system, it is characterized in that:
Described ranking operation module is done the simple digital addition to described several digital sequences.
6, the frequency jitter method of the described frequency jitter of one of a kind of claim 1 to 5 system is characterized in that, this frequency jitter method comprises the steps:
A, the output of described oscillator produce several digital sequences; In the described Serial No., comprise periodic sequence and pseudo random sequence;
B, described ranking operation module are done ranking operation to described several digital sequences;
C, described digital to analog converter are converted to analog signal to the output signal of described ranking operation module, and this analog signal is used for controlling the frequency of described oscillator.
7, frequency jitter method according to claim 6 is characterized in that:
Described system also comprises the analog module that connects described digital to analog converter and oscillator;
The input signal of this analog module is the continuous signal of the output and the output of direct or indirect representation switch power-supply system power of described digital to analog converter;
Utilize described continuous signal to control the output of digital to analog converter, so that system increases in full load frequency jitter amplitude, the frequency jitter amplitude reduces when underloading.
8, frequency jitter method according to claim 7 is characterized in that:
Described analog module is an analog multiplier;
The signal of described direct or indirect representation switch power-supply system power output is the VDD of system feedback voltage VFB or power controller.
9, frequency jitter method according to claim 6 is characterized in that:
Described ranking operation module is done the simple digital addition to described several digital sequences;
Each Serial No. is a periodic sequence, or is pseudo random sequence.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102025265A (en) * | 2010-11-16 | 2011-04-20 | 灿芯半导体(上海)有限公司 | Frequency jittering circuit |
| CN104601015A (en) * | 2014-01-14 | 2015-05-06 | 深圳市稳先微电子有限公司 | Flyback AC-DC converter |
| CN105119481A (en) * | 2015-09-11 | 2015-12-02 | 厦门科华恒盛股份有限公司 | SVPWM control method for energy storage current transformer |
| CN110518803A (en) * | 2019-07-25 | 2019-11-29 | 杭州洲钜电子科技有限公司 | A kind of Switching Power Supply frequency control circuit and control method |
-
2009
- 2009-09-15 CN CN200910195698A patent/CN101651411A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102025265A (en) * | 2010-11-16 | 2011-04-20 | 灿芯半导体(上海)有限公司 | Frequency jittering circuit |
| CN102025265B (en) * | 2010-11-16 | 2013-08-21 | 灿芯半导体(上海)有限公司 | Frequency jittering circuit |
| CN104601015A (en) * | 2014-01-14 | 2015-05-06 | 深圳市稳先微电子有限公司 | Flyback AC-DC converter |
| CN105119481A (en) * | 2015-09-11 | 2015-12-02 | 厦门科华恒盛股份有限公司 | SVPWM control method for energy storage current transformer |
| CN110518803A (en) * | 2019-07-25 | 2019-11-29 | 杭州洲钜电子科技有限公司 | A kind of Switching Power Supply frequency control circuit and control method |
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Owner name: YANG YUANYUAN Free format text: FORMER OWNER: SHANGHAI DAOXIANG MICROELECTRONICS CO., LTD. Effective date: 20100308 |
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Inventor after: Yang Yuanyuan Inventor before: Ye Jun Inventor before: Lin Guanqiu Inventor before: Hu Weiming |
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Free format text: CORRECT: INVENTOR; FROM: YE JUN LIN GUANQIU HU WEIMING TO: YANG YUANYUAN Free format text: CORRECT: ADDRESS; FROM: 200433 ROOM 402, FUDAN SCIENCE AND TECHNOLOGY PARK, NO.11, GUOTAI ROAD, YANGPU DISTRICT, SHANGHAI CITY TO: 474450 NO.595, SHIZI ROAD, CHENGGUAN TOWN, XICHUAN COUNTY, HENAN PROVINCE |
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Effective date of registration: 20100308 Address after: 474450 No. 595 lion Road, Chengguan Town, Xichuan County, Henan Province Applicant after: Yang Yuanyuan Address before: 200433, room 402, Fudan Science Park, No. 11 Guotai Road, Shanghai, Yangpu District Applicant before: Shanghai Daoxiang Microelectronics Co., Ltd. |
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Application publication date: 20100217 |