CN101741250A - Pulse width modulation control circuit reducing electromagnetic interference by frequency modulation of commercial power and method thereof - Google Patents

Abstract

The invention relates to a pulse width modulation control circuit reducing electromagnetic interference by frequency modulation of commercial power and a method thereof. The pulse width modulation control circuit comprises a signal conversion unit and a pulse width modulation controller, wherein the signal conversion unit samples and filters the commercial power signal to output the low-frequency frequency modulation signal, the pulse width modulation controller generates the synchronous pulse width modulation signal by the modulation according to the first frequency modulation signal and then outputs the frequency conversion switching signal according to the first frequency modulation signal, the switching current signal and the feedback signal; and thus, because the low-frequency commercial power signal is used as the frequency modulation signal to output the pulse width modulation signal determining the switching frequency of the switching signal, so the electromagnetic interference spectrum of a switching type power supply converter is widened, the energy of the electromagnetic interference is effectively dispersed, and the advantages of relatively simplifying the circuit and saving cost are achieved.

Description

Reduce the pulse width modulating control circuit and the method thereof of electromagnetic interference with civil power frequency modulation

Technical field

The pulse width modulating control circuit of a kind of exchangeable type power supply circuit of the present invention refers to a kind of pulse width modulating control circuit and method thereof that reduces electromagnetic interference with civil power frequency modulation especially.

Background technology

So-called exchange type power transducer is to utilize the Switching power technology to convert a unregulated supply to power supply that a Gong electrical appliance of regulating uses, to have reduced the volume of exchange type power transducer.Though the Switching power technology has been reduced the volume of exchange type power transducer, the active switch because of the exchange type power transducer switches the electromagnetic interference that keying produces also, and has influenced power supply and peripheral equipment thereof.

Therefore need to dispose the device that reduces electromagnetic interference, for example Electromagnetic interference filter, tranformer protection etc. in the exchange type power transducer.Yet the device of this type of anti-electromagnetic interference will cause suitable power loss, increase the cost and the volume of exchange type power transducer relatively.Therefore, in standard of energy unusual strict today, must abandon the device of existing anti-electromagnetic interference, actively seeking simultaneously can be in the inner scheme that realizes of IC.

In recent development, many general new technologies appear, and frequency of utilization modulation or frequency hopping reduce electromagnetic interference, announce the 6th, 229 just as United States Patent (USP), and No. 366 and the 6th, 249, No. 876 patents all adopt frequency modulating technology to reduce electromagnetic interference; Be not difficult thus to find that the method for the PWM controller of the active switch of exchange type power transducer being set about reducing electromagnetic interference is the only way which must be passed.

At present the frequency jitter technique principle used of each source appliance manufacturer is understood that, its principle is to suppress electromagnetic interference energy on the single frequency by strengthening the Switching power frequency spectrums of operation.

See also shown in Figure 11ly, disclose a kind of exchange type power transducer, include a PWM controller 50, initiatively switch Q1, a transformer TR1 and a feedback unit 511 based on existing frequency modulating technology; Wherein this PWM controller 50 includes a frequency setting end RT, a feedback end FB, one initiatively an output switching terminal SW and a current sense end SENSE, and wherein the active output switching terminal SW of this PWM controller 50 produces a switching signal V _SW, and be connected with the control end of this active switch Q1, open and close in order to control this active switch Q1, and then switch the electric current of this transformer TR1 primary side.The frequency setting end R of this pulse-width modulation circuit 50 _TWith a resistor R _TConnect, switch frequency to determine one of this PWM controller 50.And the current sense end SENSE of this pulse-width regulating device 50 connects an inspection flow resistor R who is serially connected with on the transformer TR1 primary side electric power loop _S, switch electric current I with one of this transformer of sensing TR1 _S, promptly as switch current this inspection flow resistor R that flows through _SThe time, can be in inspection flow resistor R _SForm a cross-pressure voltage signal V _S, so this PWM controller 50 can obtain the voltage signal V of this reaction switch current _S, moreover this feedback end FB of this PWM controller 50 further sees through the output that this feedback circuit 511 is connected to the secondary side circuit of this transformer TR1, with the output voltage of obtaining the exchange type power transducer as feedback signal V _FBThus, this PWM controller 50 can be according to this voltage signal V _SAnd this feedback signal V _FB, adjust switching signal V _SWWork period, to regulate the output signal V of exchange type power transducer _O, and then determined to be sent to the power of exchange type power converter output end from power input.Moreover, this switching signal V _SWCarry out frequency modulating according to PWM controller 50 internal circuits, expand the electromagnetic interference spectrum energy of exchange type power transducer 50, in order to reduce electromagnetic interference.

Hence one can see that, and this exchange type power transducer utilizes these PWM controller 50 internal circuits to realize frequency modulating or frequency hopping really, reaches the electromagnetic interference purpose that reduces the exchange type power transducer; Below sincerely further specify two circuit that PWM controller 50 realizes the frequency modulating technology.

At first seeing also shown in Figure 12 A, is the PWM controller 50 of a tool frequency modulating function, and it comprises one first oscillator 51, a coding circuit 52, one second oscillator 53 and a pulse-width regulating device 54; Wherein this first oscillator 51 produces a pulse-width modulation signal PLS1, and further is of coupled connections with these coding circuit 52 inputs, makes this coding circuit 52 produce a data signal groups d1...dn; Wherein, n is a positive integer.Again, this second oscillator coupling 53 is connected to output and this resistor R of this coding circuit _T,, and then produce the pulse-width modulation signal P of a frequency modulating according to this data signal groups d1...dn modulation variable capacitor in addition _LS2Again, this pulse-width regulating device 54 is coupled to the output of this second oscillator 53, obtains pulse-width modulation signal P _LS2Produce the switching signal V of a frequency modulating _SW, so can be by this pulse-width modulation signal P _LS2The switching frequency of this exchange type power transducer of modulation; And expanded the electromagnetic interference spectrum energy of exchange type power transducer, reduced electromagnetic interference.

See also Figure 12 B again, for another has the PWM controller 50a of frequency modulating function, it comprises one first oscillator 51, one second oscillator 53 and a pulse-width regulating device 54; Wherein this first oscillator 51 produces one-period triangle wave voltage signal V _TRI, this second oscillator then is coupled to the output of this first oscillator 51, in order to according to this triangular signal V _TRIProduce the pulse-width modulation signal P of a frequency modulating _LS2Again, this triangular signal V _TRIThese second oscillator, 53 an inner charging and discharging currents source or condenser voltage potential values of modulation.And this pulse-width regulating device 54 is coupled to the output of second oscillator 53, to obtain this pulse-width modulation signal P _LS2Produce the switching signal V of a frequency modulating _SW, expanded the electromagnetic interference spectrum energy of exchange type power transducer equally, reach and reduced the electromagnetic interference purpose.

Because this PWM controller all is made as integrated circuit at present, and become an IC element, therefore two kinds of existing frequency modulating technology of above-mentioned announcement all are to go out artificial FM signal at the IC internal production, with the switching frequency of control internal oscillator circuit modulation switching signal; Therefore also FM signal is generally periodic signal, and frequency mostly is about 300Hz, make control initiatively the switching frequency spectrum of switch count and be very limited, reduce the effect of electromagnetic interference and have a greatly reduced quality.Illustrate it, the work fundamental frequency of supposing Switching power is 65kHz, and the modulation frequency signal cycle is T _M, then the switching frequency of this modulation switching signal is counted and is amounted to approximately:

$N=\frac{T_M/2}{T_{\mathrm{SW}}}=\frac{T_M/2}{1/65k}\≈33k{T}_M---\left(1\right)$

Therefore, if exchange type power transducer electromagnetic interference energy is E _S, then unifrequency point electromagnetic interference energy is about:

This shows the electromagnetic interference of single-frequency point and the modulation envelope relation of being inversely proportional to, modulation envelope period T _MBig more, effect is good more.To go out the frequency of artificial FM signal higher but be subject to the IC internal production, so the cycle of FM signal can only accomplish to be inserted in above-mentioned (1) formula as can be known about about 3.3ms, the effective operating frequency of Switching power reality of work is counted about 110 at most.

Summary of the invention

Main purpose of the present invention provides a kind of pulse width modulating control circuit and method thereof with civil power frequency modulation reduction electromagnetic interference, to disperse the electromagnetic interference energy more effectively, reaches comparatively desirable anti-electromagnetic interference effect.

Desiring to reach the employed major technique means of above-mentioned purpose makes this pulse width modulating control circuit include:

One signal conversion unit comprises a mains supply input, exports a low frequency direct current signal city's signal of telecommunication is given sampling filter, as the first frequency modulating signal; And

One PWM controller is connected to the output of this signal conversion unit, goes out synchronous pulse-width modulation signal with foundation first frequency modulating signal modulation, cooperates one to switch current signal and a feedback signal is exported a frequency conversion switching signal again.

Pulse-width modulation control mode of the present invention again includes:

Directly obtain city's signal of telecommunication;

Produce a first frequency modulating signal, this city's signal of telecommunication is carried out sampling filter, to produce the first frequency modulating signal;

Produce a second frequency modulating signal, according to first frequency modulating signal modulation go out fixed amplitude and with the second frequency modulating signal of first frequency modulating signal same frequency;

Produce a pulse-width modulation signal, adjust a pulse-width modulation signal according to this second frequency modulating signal;

Producing one and switch signal, is fundamental frequency with this pulse-width modulation signal, cooperates the feedback signal of switch current signal and output, adjusts the frequency of pulse-width modulation signal and exports this switching signal.

Because the exchange type power transducer is in order to be converted to mains supply DC power supply output, therefore Direct Sampling of the present invention and modulate city's signal of telecommunication of low frequency, promptly constitute frequency conversion city signal frequently through simple signal processing, for PWM controller in addition the charging and discharging currents source or a condenser voltage potential value of its oscillator of modulation, and export the pulse-width modulation signal of the switching frequency of a decision switching signal; Since the frequency of pulse-width modulation signal with the frequency conversion city of low frequency frequently signal in addition modulation come out, so the switching frequency of modulation switching signal is counted at least about there being 330; Be with, the present invention directly adopts low frequency civil power modulating signal to go out the pulse-width modulation signal, not only strengthened the electromagnetic interference frequency spectrum of exchange type power transducer, disperse the electromagnetic interference energy to reach comparatively desirable anti-electromagnetic interference effect and imitate ground, compare artificial modulating signal circuit, the advantage that simplifies circuit and cost is relatively more arranged.

Description of drawings

Fig. 1 is the calcspar that the present invention is applied to a preferred embodiment of an exchangeable type power supply circuit.

Fig. 2 is the calcspar of pulse-width modulation circuit of the present invention.

Fig. 3 is another calcspar of pulse-width modulation circuit of the present invention.

Fig. 4 is the detailed circuit diagram of frequency modulating circuit first preferred embodiment of the present invention.

Fig. 5 is the frequency time-sequence curve chart of Fig. 4.

Fig. 6 is the detailed circuit diagram of frequency modulating circuit second preferred embodiment of the present invention.

Fig. 7 is the frequency time-sequence curve chart of Fig. 6.

Fig. 8 is the detailed circuit diagram of frequency modulating circuit second preferred embodiment of the present invention.

Fig. 9 is the detailed circuit diagram of frequency modulating circuit the 3rd preferred embodiment of the present invention.

Figure 10 is the detailed circuit diagram of frequency modulating circuit the 4th preferred embodiment of the present invention.

Figure 11 is the circuit diagram of an existing exchangeable type power supply circuit.

Figure 12 A is the circuit block diagram of PWM controller among Figure 11.

Figure 12 B is another circuit block diagram of PWM controller among Figure 11.

Embodiment

See also shown in Figure 1ly, for first preferred embodiment of frequency modulation type pulse width modulating control circuit 10 of the present invention is applied in the exchangeable type power supply circuit of an isolated form, wherein the exchangeable type power supply circuit of this isolated form includes:

One transformer TR1 includes primary side and secondary side;

One active switch Q1, serial connection is to this transformer TR1 primary side electric power loop;

One pulse-width modulation circuit 10 includes a signal conversion unit 20 and a PWM controller 30, wherein please cooperate consult shown in Figure 2:

This signal conversion unit 20 is connected to mains supply input V _AC, this city's signal of telecommunication is given sampling filter, export a low frequency first frequency modulating signal V _FMIn present embodiment, include a sampling unit 21, one filtering capacitors 22, a voltage divider 23 and a HF filtering capacitor 24.This sampling unit 21 and 22 pairs of these cities of this filtering capacitor signal of telecommunication V _ACCarry out sampling filter, to produce city signal V frequently _INThis city is signal V frequently _INVoltage through after this voltage divider 23 carries out the ratio step-down, through this HF filtering capacitor 24 its high frequency is given filtering simultaneously after, produce this low frequency first frequency modulating signal V _FMIn addition, this city frequency signal V _INAlso can be used as the input power supply of this transformer TR1 primary side.In addition, as shown in Figure 3, signal conversion unit 20 another preferred embodiments and Fig. 2 are roughly the same, only do not comprise filtering capacitor, so this HF filtering capacitor 24 sees through this voltage divider 23 and is connected to this sampling unit 21, so that being given the step-down post-sampling, direct current string ripple signal becomes forward signal, and filtering high-frequency signal wherein, and then a frequency modulating signal V of output low frequency _FMCan be all-wave or half-wave sampling unit as for sampling unit; If be illustrated the all-wave sampling unit output voltage V of present embodiment with the all-wave sampling unit _RCEAnd the frequency modulating signal V of last output _FMCan be expressed from the next:

V _REC=A|sin (100 π t) | (v) (all-wave sampling)-----------(3)

$V_{\mathrm{REC}}=\frac{1}{2}\left[A\right|\sin \left(100\mathrm{\πt}\right)|+A\sin \left(100\mathrm{\πt}\right)]\left(v\right)$ (half-wave sampling)-----(4)

$V_{\mathrm{FM}}=\frac{R_{232}}{R_{232}+R_{232}}A\left|\sin \left(100\mathrm{\πt}\right)\right|\left(v\right)$ (all-wave sampling)-----(5)

$V_{\mathrm{FM}}=\frac{R_{232}}{2(R_{232}+R_{232})}\left[A\right|\sin \left(100\mathrm{\πt}\right)|+A\sin \left(100\mathrm{\πt}\right)]\left(v\right)$ (half-wave sampling)-----(6)

Wherein, 127≤A≤380.R232 is the resistance of resistor 232, and R233 is the resistance of resistor 233.

This PWM controller 30 sees through the secondary side that this feedback unit 511 is connected to this transformer TR1, and this PWM controller 30 includes a frequency modulating circuit 40 and a pulse-width modulation unit 50 in present embodiment, wherein:

This frequency modulating circuit 40 includes:

One input interface circuit 41 includes a frequency modulating end FM, and this frequency modulating end FM is connected with these signal conversion unit 20 outputs, to obtain low frequency first frequency modulating signal V _FM, and according to this first frequency modulating signal V _FMExport the second frequency modulating signal V of a same frequency _FM1And

One oscillator 42 is connected to the output of this input interface circuit 41, to obtain second frequency modulating signal V _FM1, this oscillator 42 is according to this second frequency modulating signal V _FM1The charging and discharging currents source of modulation oscillator 42, or this oscillator 42 of modulation connect the voltage potential value of a ground capacitor, and then export a pulse-width modulation signal P _LS

This pulse-width modulation unit 50 then includes initiatively output switching terminal SW of an input, a feedback end FB, a current sense end SENSE and, and wherein this input is connected to the output of this oscillator 42, to obtain pulse-width modulation signal P _LS, this feedback end FB sees through a feedback unit 511 and is connected to this transformer TR1 secondary side power supply again, with the VD that obtains exchangeable type power supply circuit as feedback signal V _FBThis current sense end SENSE then is connected to a resistor R that is serially connected with transformer TR1 primary side electric power loop _S, switch electric current I with one of this transformer of sensing TR1 _S, this pulse-width modulation unit 50 is according to pulse-width modulation signal P _LS, feedback signal V _FBAnd switch current I _S, initiatively signal V is switched in output switching terminal SW output one certainly _SW, the active switch Q1 that supplies to be connected with this active output switching terminal SW is according to switching signal V _SWSwitch and open and close.

As shown in the above description, because civil power signal frequency about 50 or 60Hz belong to low frequency signal, add that the formula power circuit of changing originally just is used for mains supply is converted to DC power supply output; Be with, frequency modulation type pulse-width modulation circuit Direct Sampling of the present invention is also modulated city's signal of telecommunication of low frequency, promptly constitute frequency conversion city signal frequently through simple signal processing, provide and give PWM controller, make this PWM controller utilize this civil power signal frequency modulation to export the initiatively switching signal frequency of switch to, strengthened the electromagnetic interference frequency spectrum of exchange type power transducer, disperse the electromagnetic interference energy to reach comparatively desirable anti-electromagnetic interference effect and imitate ground, so the switching frequency of modulation switching signal is counted at least about there being 330, and needn't in pulse-width regulating device, increase artificial modulating signal circuit, the integrated circuit design simplifies circuit relatively, and cost also can effectively reduce.

See also shown in Figure 4ly, be first preferred embodiment of said frequencies modulation circuit 10, wherein this input interface circuit is an automatic gain controller 411.This automatic gain controller 411 is according to the first frequency modulating signal V that is changeed unit output by signal _FM, produce fixed amplitude and Frequency Synchronization in first frequency modulating signal V _FMThis second frequency modulating signal V _FM1Wherein, this automatic gain controller 411 can be selected according to concrete application, for example, and can be according to following first and second frequency modulating signal V _FM, V _FM1Functional relation selected suitable automatic gain controller:

V _FM1＝f(V _FM)(v)------------------(7)

Wherein, f (V _FM) same frequency domain V _FM, amplitude is definite value V _PP

42 on oscillator as for the frequency modulating circuit in the present embodiment includes charging current source 421, a discharge current source 422, a charge switch 423, a discharge switch 424, a capacitor 425, first and second comparator 426,427 and a flip-flop 428.

This charging includes a constant current source 421a and a dependent current source 421b with current source 421, in order to produce a charging current I _CHDischarge then comprises a constant current source 422a and a dependent current source 422b with current source 422, in order to produce a discharging current I _REWherein, two interdependent current source 421b, 422b are coupled to the output of this input interface circuit 41, in order to according to this second modulating signal V _FM1Produce charging current I _CHWith discharging current I _RETherefore, this charging current I _CHWith this discharging current I _REAccording to this second frequency modulating signal V _FM1Set.

This capacitor 425 sees through charge switch 423 and discharge switch 424 respectively and is connected to charging and discharging current source 421,422 again, and with the reverse input end of first comparator 426, and the positive input of second comparator 427 be of coupled connections, and the positive input of first comparator 426 is connected to reference voltage V _H, second comparator 428 then is connected to reference voltage V _LAt last, the output of this first and second comparator 426,427 is connected to the corresponding input R/S of this flip-flop 428 respectively, and the forward output Q of flip-flop 428 is connected to discharge switch 424, and its reversed-phase output Q then is connected to this charge switch 423.

Because charge switch 426 and discharge switch 427 are controlled opening and closing time by the output signal of flip-flop 428, therefore when charge switch 423 is opened short circuit according to the reverse output signal of flip-flop 428, can be charged by 421 pairs of capacitors 425 of charging current source, this moment, this forward output signal can be controlled discharge switch 424 shutdowns; Otherwise when charge switch 423 during according to the reverse output signal shutdown of flip-flop, and this forward output signal can be controlled discharge switch and holds 424 and open short circuit, makes 425 pairs of discharge power supplies of capacitor begin discharge; Thus, capacitor 425 produces a voltage triangular wave V by discharging and recharging _TRIGive first and second comparator 426,427, so flip-flop 428 produces output signal according to this voltage triangular wave VTRI, again because last reference voltage V _HBe higher than this time reference voltage V _L, the forward output Q of this flip-flop 428 produces pulse-width modulation signal P _LS, inverse output terminal Q then exports the pulse-width modulation signal P opposite with forward output Q _LSB, the pulse-width modulation signal P of forward output end Q wherein again _LSIn order to decision subordinate pulse-width modulation unit 50 output switching signal V _SWSwitching frequency.

As shown in the above description, because the current source that is used for capacitor 425 charging and discharge according to this second frequency modulating signal V _FM1And decide, therefore, pulse-width modulation signal P _LSFrequency can be by according to second frequency modulating signal V _FM1Modulation.For example, the frequency of pulse-width modulation signal PLS and second frequency modulating signal V _FM1Relation:

f _sw＝kV _FM1(kHz)------------------(8)

Wherein, f _SWBe the frequency of pulse-width modulation signal PLS, k is the predetermined constant coefficient.Please cooperate and consult Fig. 5, be the timely overture line chart of the switching frequency of this frequency modulating circuit 10, the time unit interval T among this figure is the cycle time of frequency modulating signal, and switching frequency is at f _MWith f _NBetween change f _TBe median frequency.

See also shown in Figure 6, be 40 second preferred embodiments of frequency modulating circuit, itself and Fig. 4 first preferred embodiment are roughly the same, and only this input interface circuit 41 further includes a resistor 412 that is connected with the output output of automatic gain controller 411, and one and a reference voltage V _REF1The voltage divider 413 that connects, wherein this resistor 412 is connected to the series connection node of this voltage divider 413 again.Thus, the second frequency modulating signal V of these automatic gain controller 411 outputs _FM1A reference voltage V by resistor 412 and voltage divider 413 promptly can superpose _REF1, and produce a reference voltage V _HFor example, this reference voltage V _HWith this second frequency modulating signal V _FM1There is following relational expression:

$V_H=(\frac{V_{\mathrm{REF}1}}{R_{721}}+\frac{V_{\mathrm{FM}1}}{R_{723}})\·\left(R_{721}\right|\left|R_{722}\right|\left|R_{723}\right)---\left(9\right)$

Be with, this second frequency modulating signal V _FM1Modulation V _H

Oscillator as for the oscillator 42 of present embodiment and first preferred embodiment is roughly the same, does not only comprise two interdependent current sources, and wherein the positive input of first comparator 426 promptly is connected directly to reference voltage V by above-mentioned input interface circuit 41 outputs _H

Because this reference voltage V _HAccording to second frequency modulating signal V _FM1And deciding, so this pulse-width modulation signal P _LSFrequency can be by basis signal VFM1 modulation.

Please cooperate and consult shown in Figure 7ly, be the timely overture line chart of switching frequency of frequency modulating circuit 40 second preferred embodiments of the present invention, the time unit interval T among this figure is frequency modulating signal V _FMCycle time, and switching frequency changes between fM and fN, fT is a median frequency.

See also shown in Figure 8ly, be the 3rd preferred embodiment of frequency modulating circuit 40 of the present invention, itself and second preferred embodiment are roughly the same, only the reference voltage V of these input interface circuit 41 outputs _LBe connected directly to this second comparator, 427 reverse input ends.Again, this reference voltage V _LWith this second frequency modulating signal V _FM1There is following relation:

$V_L=(\frac{V_{\mathrm{REF}1}}{R_{821}}+\frac{V_{\mathrm{FM}1}}{R_{823}})\·\left(R_{821}\right|\left|R_{822}\right|\left|R_{823}\right)---\left(10\right)$

Therefore, this second frequency modulating signal V _FM1Really modulation reference voltage V _L, and can produce pulse-width modulation signal P with second frequency modulating signal Frequency Synchronization _LS

See also shown in Figure 9, the 4th preferred embodiment for frequency modulating circuit 40 of the present invention, itself and second preferred embodiment are roughly the same, only this input interface circuit 41 further includes a n position analog-digital converter 414, it is connected in the output of this automatic gain controller 411, further with second frequency modulating signal V _FM1Convert a corresponding data signal groups D1 to Dn to; Wherein, n is a positive integer, makes this oscillator 42 be coupled to this input interface circuit 41, and produces a frequency modulating pulse-width modulation signal P according to this data signal groups D1...Dn _LSAnd P _LSB, this pulse-width modulation signal P _LSBBe this pulse-width modulation signal P _LSThe antiphase signal.

And the oscillator 42 of present embodiment uses variable capacitor 425a, and be connected with the analog-digital converter 414 of this input interface circuit 41, make variable capacitor 425a accept the control of this data signal groups D1...Dn, promptly according to the capacitance of this variable capacitor of this data signal groups D1...Dn modulation 425a.Because this variable capacitor 425a is according to its capacitance of this data signal groups D1...Dn modulation, therefore, this pulse-width modulation signal P _LSFrequency promptly equally can be according to this second frequency modulating signal V _FM1Modulation.

See also shown in Figure 10ly again, be the 5th preferred embodiment of frequency modulating circuit 40 of the present invention.In the present embodiment, this input interface circuit 411 is an automatic gain controller 411, and this oscillator 42 then is a voltage controlled oscillator 42a, and wherein this voltage controlled oscillator 42a is according to this second frequency modulating signal V _FM1, produce Frequency Synchronization in V _FM1This pulse-width modulation signal P _LS, so pulse-width modulation signal P _LSFrequency equally can be by according to this second modulating signal V _FM1Modulation.

The present invention adopts the initiatively switching frequency of switch exchange type power transducer of the direct modulation of city's signal of telecommunication of low frequency, and it is more even to make that the electromagnetic interference energy disperses at frequency spectrum, and the electromagnetic interference energy on the fixed frequency is lower.Therefore, better based on the effect of exchange type power transducer reduction electromagnetic interference of the present invention.

Though the present invention discloses as above with preferred embodiment, yet it should not limit the present invention, any technical staff who is familiar with this field, without departing from the spirit and scope of the present invention, when doing a little change and replacement.Therefore protection scope of the present invention is as the criterion when looking the claim scope person of defining.

Claims (15)

1. one kind is reduced the pulse width modulating control circuit of electromagnetic interference with civil power frequency modulation, it is characterized in that described circuit includes:

One signal conversion unit comprises a mains supply input, exports a low frequency direct current signal city's signal of telecommunication is given sampling filter, as the first frequency modulating signal; And

One PWM controller is connected to the output of described signal conversion unit, goes out synchronous pulse-width modulation signal with foundation first frequency modulating signal modulation, cooperates one to switch current signal and a feedback signal is exported a frequency conversion switching signal again.

2. pulse width modulating control circuit according to claim 1 is characterized in that described signal conversion unit includes:

One sampling unit is connected with described mains supply input, is direct current string ripple signal with the civil power signal sampling;

One filtering capacitor is connected to described sampling unit, being direct current signal with the signal filtering of direct current string ripple; And

One HF filtering capacitor sees through a voltage divider and is connected to described filtering capacitor, direct current signal being given after the step-down wherein high-frequency signal of filtering, and then the first frequency modulating signal of output low frequency.

3. pulse width modulating control circuit according to claim 1 is characterized in that described signal conversion unit includes:

One sampling unit is connected with described mains supply input, is direct current string ripple signal with the civil power signal sampling; And

One HF filtering capacitor sees through a voltage divider and is connected to described sampling unit, becomes forward signal so that direct current string ripple signal is given the step-down post-sampling, and filtering high-frequency signal wherein, and then the first frequency modulating signal of output low frequency.

4. as pulse width modulating control circuit as described in claim 2 or 3, it is characterized in that described sampling unit is all-wave or half-wave sampling unit.

5. as pulse width modulating control circuit as described in the claim 4, it is characterized in that described PWM controller includes a frequency modulating circuit and a pulse-width modulation unit, wherein said frequency modulating circuit includes:

One input interface circuit includes a frequency modulating end, and described frequency modulating end is connected with described signal conversion unit output, to export the second frequency modulating signal of a same frequency according to described first frequency modulating signal; And

One oscillator is connected to the output of described input interface circuit, to export described pulse-width modulation signal according to described second frequency modulating signal;

Described pulse-width modulation unit then includes:

One input is connected to the output of described oscillator, to obtain the pulse-width modulation signal;

One feedback end is obtained described feedback signal for being connected with a feedback unit;

One current sense end is obtained switch current; And

One active output switching terminal supplies to be connected with an active switch, and according to described pulse-width modulation signal, described feedback signal and described switch current, output one switching signal is described active switch extremely.

6. as pulse width modulating control circuit as described in the claim 5, it is characterized in that, described input interface circuit includes an automatic gain controller, its input is connected to the output of described signal conversion unit, and Frequency Synchronization is in a second frequency modulating signal of first frequency modulating signal to produce fixed amplitude.

7. pulse width modulating control circuit as claimed in claim 6 is characterized in that, described oscillator includes:

One capacitor;

One charging current source sees through a charge switch and is connected with described capacitor, and described charging current of condenser is provided;

One discharge current source sees through a discharge switch and is connected with described capacitor, and described capacitor discharge current is provided;

One first comparator, its reverse input end is connected to described capacitor, and another positive input then connects reference voltage on;

One second comparator, its positive input is connected to described capacitor, and another reverse input end then connects reference voltage; And

One flip-flop, its two input is connected to the output of first and second comparator respectively, wherein the forward output then is connected to discharge switch, and inverse output terminal then is connected to charge switch, and described again forward output is exported described pulse-width modulation signal and given described pulse-width modulation unit.

8. pulse width modulating control circuit as claimed in claim 6, it is characterized in that, described oscillator includes a variable capacitor, described variable capacitor is connected to the output of described automatic gain controller, with according to described second frequency modulating signal, produce Frequency Synchronization in the pulse-width modulation signal of second frequency modulating signal.

9. pulse width modulating control circuit as claimed in claim 7 is characterized in that, described charging includes respectively with current source with current source and discharge:

One constant current source; And

One dependent current source, in parallel with described constant current source, and be connected with the output of described automatic gain controller, to produce a charging current and a discharging current according to described second frequency modulating signal.

10. pulse width modulating control circuit as claimed in claim 7, it is characterized in that, described input interface circuit further is connected with a resistor and a voltage divider, the output of wherein said automatic gain controller sees through described resistor and is connected to described voltage divider, and voltage divider is connected with a reference voltage, so the reference voltage after the second frequency modulating signal of the output interface circuit output stack dividing potential drop, as the last reference voltage of the positive input of first comparator of described oscillator.

11. pulse width modulating control circuit as claimed in claim 7, it is characterized in that, described input interface circuit further is connected with a resistor and a voltage divider, the output of wherein said automatic gain controller sees through described resistor and is connected to described voltage divider, and voltage divider is connected with a reference voltage, so the reference voltage after the second frequency modulating signal of the output interface circuit output stack dividing potential drop, as the following reference voltage of the positive input of second comparator of described oscillator.

12. pulse width modulating control circuit as claimed in claim 7, it is characterized in that, described input interface circuit further includes an analog-digital converter, described analog-digital converter is connected to the output of described automatic gain controller, the second frequency modulating signal is converted to a corresponding data signal groups, the capacitor of described oscillator is a variable capacitor again, described variable capacitor is connected to described analog-digital converter, and according to its capacitance of described data signal groups.

13. pulse width modulating control circuit as claimed in claim 12 is characterized in that, described analog-digital converter is a n position analog-digital converter, and wherein said n is a positive integer.

14. the frequency approach with civil power modulation switching signal, described method includes:

Directly obtain city's signal of telecommunication;

Produce a first frequency modulating signal, the described city signal of telecommunication is carried out sampling filter, to produce the first frequency modulating signal;

Produce a second frequency modulating signal, according to first frequency modulating signal modulation go out fixed amplitude and with the second frequency modulating signal of first frequency modulating signal same frequency;

Produce a pulse-width modulation signal, adjust a pulse-width modulation signal according to described second frequency modulating signal;

Producing one and switch signal, is fundamental frequency with described pulse-width modulation signal, cooperates the feedback signal of switch current signal and output, adjusts the frequency of pulse-width modulation signal and exports described switching signal.

15. the frequency approach with civil power modulation switching signal as claimed in claim 14 is characterized in that, the pass of the frequency of described pulse-width modulation signal and described second frequency modulating signal is f _Sw=kV _FM1(kHz).

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