Current sampling circuit, current over-zero detection circuit, totem non-bridge PFC circuits and itsControl methodTechnical field
The present invention relates to pfc circuit more particularly to the current samples of totem non-bridge PFC circuits.
Background technique
The input stage of AC-DC power inverter is usually rectifier bridge, usually connects Boost circuit after rectifier bridge, due to rectificationBridge has 2 diode drops, limits further increasing for converter efficiency itself.With power grade increase andThe raising that transducer effciency requires, rectifier bridge loss are a very big problems.One solution is to replace diode rectifier bridgeChange metal-oxide-semiconductor rectifier bridge into, but cost obviously increases；Another solution is to remove rectifier bridge, is switched from the PFC of bridge rectifierTo non-bridge PFC.Totem non-bridge PFC is the best PFC topology of current performance, and power component is less, compact to design, half-bridge knotStructure facilitates to be controlled using quasi- ZVS or ZVS, can high frequency, and there is lower EMI, the disadvantage is that control is complicated, current sample is tiredIt is difficult.
Fig. 1 show a kind of existing totem non-bridge PFC circuits sampled using current transformer, including inductanceLboost, switching tube Q1, switching tube Q2, diode Da, diode Db, switching tube Q1 and switching tube Q2 are composed in series switch bridgeArm, diode Da and diode Db are composed in series rectifying bridge arm, and one end of input power Vin is couple to out by inductance LboostThe other end at the midpoint, input power Vin of closing bridge arm is directly coupled to the midpoint of the second rectifying bridge arm, switchs bridge arm, rectifier bridgeArm, filter capacitor and output loading are in parallel, and two input terminals of the first current sampling circuit 11a seal in the upper bridge of switch bridge armArm detects the switching current when input of AC negative half-cycle, and two input terminals of the second current sampling circuit 11b seal in switch bridge armLower bridge arm detection AC positive half period input when switching current.
First current sampling circuit 11a and the second current sampling circuit 11b uses custom circuit, and structure is identical, is packetInclude a Current Transmit 1/CT2, a degausser, a sampling resistor Rs1/Rs2 and a diode D1/D2, current transformerIncluding a primary side winding P1/P2 and a vice-side winding S1/S2, the both ends of primary side winding P1/P2 are two of current sampling circuitInput terminal, one end after vice-side winding S1/S2 is in parallel with degausser connect the anode of diode D1/D2, the other end is grounded, and goesMagnetic circuit is composed in parallel by degaussing inductance Lm and demagnetizing resistance Rs1/Rs2, is used to give Current Transmit 1/CT2 degaussing, two polesThe cathode of pipe D1/D2 connects the output end of sample circuit and one end of sampling resistor Rs1/Rs2, sampling resistor Rs1/Rs2 simultaneouslyThe other end ground connection.
Circuit shown in Fig. 1 can occur pair due to switching tube Q1 and switching tube Q2 in the positive half period and negative half-cycle of AC inputIt adjusts, there is also positive and negative variations for the electric current in switching tube, this causes this conventional transformer current sample circuit in totem PFCThere is apparent defect in circuit.
Fig. 2 show the driver' s timing of Fig. 1 institute totem-pole non-bridge PFC circuits, and Fig. 3 A~Fig. 3 B is showing AC input justCurrent direction in half period in the single switch period in totem non-bridge PFC.Fig. 3 A is that switching tube Q1 is turned off, switching tube Q2 is ledThe case where when logical, forward current flows through mutual inductor CT2, detects inductance peak point current by 11b；Mutual inductor CT1's encourages in 11aMagnetoelectricity stream passes through diode D1, resistance Rs1 degaussing, generates unwanted voltage signal on resistance Rs1, this voltage signal mayFalse triggering is caused to act.The case where when Fig. 3 B is switching tube Q2 shutdown, switching tube Q1 conducting, switching tube Q1 is continuous as continued flow tubeStream, for exciting current by resistance Rc2 degaussing, it is usually sampling resistor that demagnetizing resistance, which is usually Ω grades of k, value, in mutual inductor CT2Tens times, by negative current in mutual inductor CT1, since diode D1 reversely ends, this negative current is on resistance Rc1Very big negative voltage (can usually reach several hundred V) is generated, if this voltage damages diode D1 reverse breakdown, justBiggish exciting current can be formed on the magnetizing inductance of mutual inductor CT1, this exciting current will pass through diode D1 and electricityRs1 degaussing is hindered, there are problems that degaussing, mutual inductor CT1 is not that saturation is exactly saturation in several periods, sampling loss in a cycleAlso it will increase, while can also generate false triggering signal.The course of work description of AC input negative half-cycle is similar with positive half period.AlwaysFor the existing transformer current sampling plan of totem non-bridge PFC shown in FIG. 1 there are mutual inductor pair side rectifying tube stressFalse triggering voltage signal is led to the problem of in excessive, mutual inductor saturation and current sampling resistor, thus is controlled from current sampleIt is required to avoid the alternative scheme of the above problem for upper.
Summary of the invention
Have in view of that, the technical problem to be solved in the present invention is to provide a kind of current sampling circuit, be applied to totem withoutBridge PFC circuit is able to solve the big problem of current transformer secondary voltage stress, further, moreover it is possible to solve mutual inductor saturationAnd it leads to the problem of and generates false triggering voltage signal on the voltage signal current sampling resistor of false triggering；Meanwhile the present invention is alsoCurrent over-zero detection circuit, totem non-bridge PFC circuits and its control method for applying the sample circuit are provided.
In order to solve the above technical problems, present invention is conceived are as follows: be applied to totem non-bridge PFC circuits existingThe current transformer pair side of current sampling circuit seal in switch control link, normal sample is carried out when flowing through forward current,And a low-resistance or low pressure path are provided when flowing through negative current, to solve that current transformer secondary voltage stress is big to askTopic；Meanwhile the presence of low resistance path or low pressure path keeps the reversed excitation of mutual inductor small, reversed exciting current also has a degaussingPath keeps reversed exciting current accumulation few, to mutual inductor will not be made to be saturated, will not generate the voltage signal of false triggering.
Current sampling circuit technical solution provided by the invention is as follows:
A kind of current sampling circuit, comprising: current transformer, degausser, sampling resistor, the first sampling input terminal, theTwo sampling input terminals and sampled output, current transformer include primary side winding and vice-side winding, and one end of primary side winding isFirst sampling input terminal, the other end are the second sampling input terminal, and vice-side winding is in parallel with degausser, and one end after parallel connection is simultaneouslyThe other end after being electrically connected with one end of sampled output and sampling resistor, being in parallel is electric with the other end of sampling resistor and ground simultaneouslyConnection；
It is characterized by also including sampling switch, there is bi-directional conductive when sampling switch is connected, when shutdown has from sunExtreme son arrives the unilateral conduction of cathode terminal；The anode terminal of sampling switch is connected to the ground, cathode terminal and vice-side winding withThe other end after degausser is in parallel is connected；Sampling switch is controlled by the gating signal of its control terminal input, in primary side windingThe shutdown of control sampling switch, the control sampling switch conducting when primary side winding flows through negative current when flowing through forward current, for thisNegative current provides a flow path.
A kind of specific embodiment as sampling switch, it is characterised in that: sampling switch is N-MOS pipe, N-MOS pipeSource electrode be the anode terminal of sampling switch, drain electrode be cathode terminal, the grid of sampling switch is the control terminal of sampling switchSon.
As an improvement of the above technical solution, it is characterised in that: further include clamp circuit, clamp circuit and sampling resistor are simultaneouslyConnection, for the negative voltage on clamper sampling resistor.
Specific embodiment as clamp circuit, it is characterised in that:
Clamp circuit includes a diode, the other end of the anode connection sampling resistor of diode, cathode connection samplingOne end of resistance；
Or clamp circuit includes a metal-oxide-semiconductor, the other end of the source electrode connection sampling resistor of metal-oxide-semiconductor, drain electrode connection are adoptedOne end of sample resistance.
In order to realize that the sampling resistor of two-way current sampling circuit can merge, it is characterised in that: further include two polesPipe, one end after the anode connection vice-side winding of diode is in parallel with degausser, the cathode of diode connect sampled output.
Current over-zero detection circuit provided by the invention, it is characterised in that: including two-way any one of the above current detectingCircuit and voltage comparator, output end, the negative input of the positive input connection current detection circuit of voltage comparatorFor inputting reference level, output end for exporting current over-zero detection signal；
The gating signal of current transformer Same Name of Ends, the input of sampling switch control terminal in each road current detection circuit is matchedIt sets as follows:
One end and current transformer vice-side winding and sampling switch yin that current transformer primary side winding forward current flows intoThe connected one end of extreme son Same Name of Ends each other；
When current transformer primary side passes through forward current, gating signal is height, driving sampling switch conducting；
When current transformer primary side passes through negative current, gating signal is low, driving sampling switch shutdown.
Preferably, reference level is zero level or the level slightly larger than zero level.
Totem non-bridge PFC circuits provided by the invention, it is characterised in that: including two-way any one of the above current detectingCircuit；Two sampling input terminals of first via current sampling circuit seal in the upper bridge arm of switch bridge arm, detect AC input negative half periodSwitching current when phase inputs；Two sampling input terminals of the second road current sampling circuit seal in the lower bridge arm of switch bridge arm, inspectionSurvey the switching current when input of AC positive half period.
The present invention also provides the control methods of above-mentioned totem non-bridge PFC circuits, it is characterised in that:
AC input positive half period, the lower bridge arm switching tube for switching bridge arm is main switch, upper bridge arm switching tube is that afterflow is openedGuan Guan, the gate control signal of the sampling switch of first via current sampling circuit are height, driving first via current sampling circuitSampling switch conducting provides a flow path in parallel to the current transformer of first via current sampling circuit；Second road electricityFlowing the gate control signal of the sampling switch of sample circuit is low, the sampling switch shutdown of the second road current sampling circuit of control,Sample main switch forward direction peak point current；
AC input negative half-cycle, the upper bridge arm switching tube for switching bridge arm is main switch, lower bridge arm switching tube is that afterflow is openedGuan Guan, the gate control signal of the sampling switch of the second road current sampling circuit are height, the second road current sampling circuit of drivingSampling switch conducting provides a flow path in parallel to the current transformer of the second road current sampling circuit；First via electricityFlowing the gate control signal of the sampling switch of sample circuit is low, the sampling switch shutdown of control first via current sampling circuit,Sample main switch forward direction peak point current.
Term is explained:
The anode terminal of sampling switch: the port that DC current is flowed inward into from sampling switch；
The cathode terminal of sampling switch: the port that DC current is flowed outwardly from sampling switch；
The control terminal of sampling switch: input control signal, the port of control sampling switch conducting and shutdown；
Two sampling input terminals of first via current sampling circuit seal in the upper bridge arm of switch bridge arm: referring to disconnecting Fig. 1The drain node of middle switching tube Q1, both ends are separately connected two sampling input terminals of first via current sampling circuit；
Two sampling input terminals of the second road current sampling circuit seal in the lower bridge arm of switch bridge arm: referring to disconnecting Fig. 1The drain node of middle switching tube Q2, both ends are separately connected two sampling input terminals of the second road current sampling circuit；
Electrically connect: the meaning of representative further includes being indirectly connected with that (i.e. two electrically connect and may be used also between object in addition to being directly connected toTo connect other components), and including passing through the modes such as inductively.
Compared with prior art, current sampling circuit provided by the invention solves the existing of totem non-bridge PFC circuitsThat there are mutual inductor pair side rectifying tube stress is excessive for transformer current sampling plan, produces on mutual inductor saturation and current sampling resistorThe problem of raw false triggering voltage signal, and circuit realizes and controls scheme all very simply.
Detailed description of the invention
Fig. 1 is a kind of existing totem non-bridge PFC circuits sampled using current transformer；
The driver' s timing of Fig. 2 Fig. 1 institute totem-pole non-bridge PFC circuits；
Electric current of Fig. 3-A for Fig. 1 institute totem-pole non-bridge PFC circuits when AC input positive half period Q1 is closed, Q2 is openedPath；
Electric current of Fig. 3-B for Fig. 1 institute totem-pole non-bridge PFC circuits when AC input positive half period Q2 is closed, Q1 is openedPath；
Fig. 4-A is current sampling circuit structural schematic diagram of the invention；
The structural schematic diagram of Fig. 4-B sampling switch；
Course of work when Fig. 5-A is current sampling circuit detection forward current shown in Fig. 4 when Q1 is connected；
Fig. 5-B is that Q1 is switched to the current sampling circuit mutual inductor shown in rear Fig. 5-A from conducting and removes magnetic-path schematic diagram；
Fig. 5-C is that course of work when current sampling circuit primary side winding shown in Fig. 4 passes through negative current when Q1 is connected is shownIt is intended to；
It is gone after current sampling circuit primary side winding shown in Fig. 4 is reduced to zero by negative current when Fig. 5-D is Q1 shutdownMagnetic-path schematic diagram；
Fig. 6 is the schematic diagram of first embodiment of the invention current sampling circuit；
Course of work when Fig. 7-A is current sampling circuit detection forward current shown in Fig. 6 when Q1 is connected；
Fig. 7-B is that Q1 is switched to the current sampling circuit mutual inductor shown in rear Fig. 7-A from conducting and removes magnetic-path schematic diagram；
Fig. 7-C is that course of work when current sampling circuit primary side winding shown in Fig. 6 passes through negative current when Q1 is connected is shownIt is intended to；
It is gone after current sampling circuit primary side winding shown in Fig. 6 is reduced to zero by negative current when Fig. 7-D is Q1 shutdownMagnetic-path schematic diagram；
Fig. 8 is the schematic diagram using the totem non-bridge PFC circuits of current sampling circuit shown in 6；
Fig. 9 is according to the controlling of sampling timing of Fig. 8 institute totem-pole non-bridge PFC circuits；
Figure 10 is the schematic diagram of second embodiment of the invention current sampling circuit；
Course of work when Figure 11-A is current sampling circuit detection forward current shown in Figure 10 when Q1 is connected；
Figure 11-B is that Q1 is switched to the current sampling circuit mutual inductor shown in rear Figure 10 from conducting magnetic-path is gone to illustrate；
Figure 11-C is course of work when current sampling circuit primary side winding shown in Figure 10 passes through negative current when Q1 is connectedSignal；
After current sampling circuit primary side winding shown in Figure 10 is reduced to zero by negative current when Figure 11-D is Q1 shutdownRemove magnetic-path schematic diagram；
Figure 12 is the schematic diagram using the totem non-bridge PFC circuits of Figure 10 current sampling circuit；
Figure 13 is applied to principle when totem non-bridge PFC circuits for the current sampling circuit of third embodiment of the inventionFigure；
Course of work when Figure 14-A is 3rd embodiment current sampling circuit detection forward current when Q1 is connected；
Figure 14-B is that Q1 is switched to the current sampling circuit mutual inductor shown in rear Figure 14-A from conducting magnetic-path is gone to illustrate；
Figure 14-C is worked when 3rd embodiment current sampling circuit primary side winding passes through negative current when Q1 is connectedJourney signal；
After 3rd embodiment current sampling circuit primary side winding is reduced to zero by negative current when Figure 14-D is Q1 shutdownRemove magnetic-path schematic diagram；
Figure 15 is that the current sampling circuit of third embodiment of the invention is applied to the totem non-bridge PFC electricity of synchronous commutation typeSchematic diagram when road；
Figure 16 for Figure 15 institute totem-pole non-bridge PFC circuits controlling of sampling timing；
Figure 17 is mutual inductor Same Name of Ends configuration mode when current sampling circuit of the present invention is used as zero passage detection；
Figure 18 is the totem non-bridge PFC circuits using current over-zero detection circuit of the present invention；
Figure 19 is the totem non-bridge PFC circuits controlling of sampling timing of Figure 18；
Figure 20 includes a kind of totem non-bridge PFC circuits of current sampling circuit of the present invention and current over-zero detection circuitBlock diagram.
Specific embodiment
Conceived based on present invention, current sampling circuit structural schematic diagram of the invention is as shown in Fig. 4-A, with Fig. 1In the difference of current sampling circuit 11a/11b be to further include sampling switch S1, the structure of sampling switch such as Fig. 4-B instituteShow there is anode terminal, cathode terminal and control terminal, wherein the anode terminal of the sampling switch S1 is connected to the ground, cathodeThe other end after terminal is in parallel with degausser with vice-side winding is connected, control terminal is for inputting gate control signal.
It is described as follows referring to the course of work of Fig. 5-A~Fig. 5-D to first embodiment:
When 1 primary side of the first Current Transmit flows through forward current, positive voltage letter is generated on the first sampling resistor Rs1Number, when the forward current that 1 primary side of the first Current Transmit passes through is reduced to zero, the first sampling switch S1 is by excitation electricityStream passes through the first degausser degaussing；
When 1 primary side of the first Current Transmit flows through negative current, the first sampling switch S1 conducting, the first sampling resistorRs1 is in parallel with the secondary side of the first Current Transmit 1 by the first sampling switch S1, generates on the first sampling resistor Rs1 lesserBackward voltage, lesser backward voltage are added on 1 vice-side winding of the first Current Transmit, to generate lesser reversed excitationElectric current, when the negative current that 1 primary side of the first Current Transmit flows through is reduced to 0, exciting current passes through the first sampling resistorRs1 and the first sampling switch S1 degaussing generate lesser positive voltage signal on the first sampling resistor Rs1, will not cause false triggeringMovement.
To describe the technical solutions in the embodiments of the present invention more clearly, below in conjunction with attached drawing to the embodiment of the present inventionIn technology carry out clear and complete description.Obviously, described embodiment is only a part of the embodiments of the present invention, withoutIt is whole embodiments.Those of ordinary skill in the art are obtained every other without making creative workEmbodiment belongs to protection scope of the present invention.
First embodiment
The first sampling switch S1 is N-MOS pipe in first embodiment of the invention, and referring to Fig. 6, the drain electrode of N-MOS pipe S1 is connectedThe other end after vice-side winding is in parallel with degausser, the source electrode ground connection of N-MOS pipe S1.
Fig. 7-A~Fig. 7-D is the course of work timing diagram of Fig. 6, has bi directional conductibility when the present embodiment N-MOS pipe S1 is connectedProperty, because therefore the presence of its body diode has unilateral conduction when shutdown, specific work process is identical as Fig. 4, herein notIt repeats.
It is different from Fig. 1 for the schematic diagram of the totem non-bridge PFC circuits of current sampling circuit shown in use 6 referring to Fig. 8Place is to replace current sampling circuit 11a/11b for circuit structure shown in fig. 6.
Fig. 9 is according to the controlling of sampling timing of Fig. 8 institute totem-pole non-bridge PFC circuits:
AC input positive half period, the lower bridge arm switching tube Q2 for switching bridge arm is main switch, upper bridge arm switching tube Q1 is continuousFlow switching tube, the gate control signal Cs1_select of the sampling switch S1 of first via current sampling circuit 11a is height, driving theThe sampling switch conducting of current sampling circuit 11a all the way provides one to the current transformer of first via current sampling circuit 11aLow-resistance or low pressure path in parallel, to avoid the voltage on first via current sampling circuit 11a current transformer vice-side windingSpike and mutual inductor saturation；The gate control signal Cs2_select of the sampling switch S2 of second road current sampling circuit 11b isLow, the sampling switch S2 shutdown of the second road current sampling circuit 11b of control samples main switch Q2 forward direction peak point current, and energyEnough make the current transformer of the second road current sampling circuit 11b after main switch Q2 shutdown by degausser quick demagnetization；
AC input negative half-cycle, the upper bridge arm switching tube Q1 for switching bridge arm is main switch, lower bridge arm switching tube Q2 is continuousFlow switching tube, the gate control signal Cs2_select of the sampling switch S2 of the second road current sampling circuit 11b is height, driving theThe sampling switch of two road current sampling circuit 11b is connected, and provides one to the current transformer of the second road current sampling circuit 11bLow-resistance or low pressure path in parallel, to avoid the voltage on the second road current sampling circuit 11b current transformer vice-side windingSpike and mutual inductor saturation；The gate control signal Cs1_select of the sampling switch S1 of first via current sampling circuit 11a isLow, the sampling switch S1 shutdown of control first via current sampling circuit 11a samples main switch Q1 forward direction peak point current, and energyEnough make the mutual inductor of first via current sampling circuit 11a after main switch Q1 shutdown by degausser quick demagnetization.
Second embodiment
On the basis of first embodiment, we come the present embodiment to the first sampling resistor Rs1 the first clamp circuit in parallelNegative voltage on the first sampling resistor of clamper Rs1.
The diode or N-MOS of the preferred low conduction voltage drop of the first clamp circuit in second embodiment are managed.Referring to Fig.1 0, whenWhen first clamp circuit is preferably the first diode of low conduction voltage drop when D1, the plus earth of first diode D1, and it is lowThe preferred Schottky diode of conduction voltage drop diode.
1-A~Figure 11-D is to the course of work of Figure 10 referring to Fig.1, with Fig. 4 the difference is that:
When the first mutual inductor primary side flows through negative current, the first sampling switch S1 conducting, the first mutual inductor secondary currentFlow through after the first sampling switch S1 again through the first clamp circuit (herein for clamp diode D1) return to the first mutual inductor pair side aroundThe other end of group；The negative voltage generated on sampling resistor Rs is not more than the conduction voltage drop of the first clamp circuit, in addition the first mutual inductanceNegative voltage on device vice-side winding is the sum of the conducting voltage of the first sampling switch and clamp diode D1, is generated lesser reversedExciting current.
When the preferred N-MOS pipe of the first clamp circuit, the source electrode that the N-MOS pipe is the first clamp switch S3, S3 is grounded,The drain electrode of S3 connects sampling output, and the gate pole of S3 is connected with the gate pole of S1, S3 and the same driver' s timing of S1.
Referring to Fig.1 2, it is different from Fig. 1 for using the schematic diagram of the totem non-bridge PFC circuits of Figure 10 current sampling circuitPlace is to replace current sampling circuit 11a/11b for circuit structure shown in Fig. 10.
The controlling of sampling timing of Figure 12 institute totem-pole non-bridge PFC circuits is identical as Fig. 9, has been described in detail above, hereinIt does not repeat.It should be noted that control signal is synchronous with corresponding sampling switch if clamp circuit is N-MOS pipe.
3rd embodiment
The current sampling circuit schematic diagram of 3rd embodiment is compared with second embodiment the difference is that there are also a diodesD3, one end after the anode connection vice-side winding of diode is in parallel with degausser, the cathode of diode connect sampled output.Figure 13, the current sampling circuit of third embodiment of the invention are applied to schematic diagram when totem non-bridge PFC circuits, not with Fig. 1It is to replace current sampling circuit 11a/11b for circuit structure shown in the present embodiment, the electricity of 3rd embodiment with placeThe reason of stream sample circuit increases a diode compared with the first, second embodiment is, due to third diode D3 and the four or twoThe reversed cut-off of pole pipe D4 acts on, wherein it is sampling resistor Rs that the first sampling resistor Rs1 and the second sampling resistor Rs2 is combinable,Sampled signal Cs1 and Cs2 are merged into sampled signal Cs.
4-A~Figure 14-D is identical as second embodiment to the worked of third embodiment of the invention referring to Fig.1, herein notIt repeats.The controlling of sampling timing of Figure 13 institute totem-pole non-bridge PFC circuits is identical as Fig. 9, has been described in detail, has not gone to live in the household of one's in-laws on getting married above hereinIt states.
It should be noted that the current sampling circuit of above three embodiments is equally applicable to the totem of synchronous commutation typeDiode Da and diode Db in rectifying bridge arm is replaced with metal-oxide-semiconductor by non-bridge PFC circuits.With reference to Figure 15, for thisApplication of the current sampling circuit of invention 3rd embodiment in the totem non-bridge PFC circuits of synchronous commutation type.
In the specific implementation, referring to Fig.1 6, for the controlling of sampling timing of Figure 15 institute totem-pole non-bridge PFC circuits, AC inputPositive half period, gating signal Cs1_select are high driving the first sampling switch S1 conducting, provide one to the first mutual inductor CT1Low resistance path in parallel；Gating signal Cs2_select is low, the second sampling switch S2 shutdown, sampling Q2 forward direction peak point current；Negative half-cycle, gating signal Cs2_select are high driving the second sampling switch S2 conducting, provide one to the second mutual inductor CT2Low resistance path in parallel, gating signal Cs1_select are low, the first sampling switch S1 shutdown, sampling Q1 forward direction peak point current.
For current sampling circuit provided by the invention, current over-zero detection can be used to implement.Realize the electricity of the functionStream zero cross detection circuit includes two-way current sampling circuit and a voltage comparator, the positive input connection of voltage comparatorOutput end, the negative input of current detection circuit are believed for inputting reference level, output end for exporting current over-zero detectionNumber；And after needing to be reconfigured the Same Name of Ends of mutual inductor and gating signal.Configuration mode is as follows:
One end and current transformer vice-side winding and sampling switch that current transformer primary side winding forward current flows intoThe connected one end of cathode terminal Same Name of Ends each other；
When current transformer primary side passes through forward current, gating signal is height, and driving sampling switch conducting is mutual to electric currentSensor provides a low-resistance in parallel or low pressure flow path, to avoid first via current sampling circuit current transformer pair sideDue to voltage spikes and mutual inductor saturation on winding；
When current transformer primary side passes through negative current, gating signal is low, driving sampling switch shutdown, freewheel currentVoltage drop is formed on sampling resistor, and current transformer can be made quick by degausser after secondary current is reduced to zeroDegaussing.
Figure 17 is mutual inductor Same Name of Ends configuration mode when current sampling circuit of the present invention is used as zero passage detection；Figure 18 is to answerWith the totem non-bridge PFC circuits of current over-zero detection circuit of the present invention；The totem non-bridge PFC circuits that Figure 19 is Figure 18 sampleControl sequential.
In the specific implementation, referring to Fig.1 9, AC input positive half period, gating signal Cs4_select is high the 4th sampling of drivingSwitch S4 conducting provides a low resistance path in parallel to the 4th mutual inductor CT4；Gating signal Cs3_select is low, thirdSampling switch S3 shutdown, samples freewheel current；Negative half-cycle, gating signal Cs3_select are high driving third sampling switchS3 conducting provides a low resistance path in parallel to third mutual inductor CT3, and gating signal Cs4_select is low, the 4th samplingSwitch S4 shutdown, samples freewheel current.The freewheel current sampled formed on no-voltage sampling resistor voltage drop and with referenceLevel compares to export current over-zero detection signal, the ZCD when the voltage signal on zero voltage resistance is less than some reference valueSignal is height.
Current detection circuit and current over-zero detection circuit of the invention can also be applied to totem non-bridge PFC electricity simultaneouslyRoad, with reference to the circuit block diagram of Figure 20, current sampling circuit therein can choose any one current detection circuit, zero current inspectionSlowdown monitoring circuit also can choose any one current detection circuit, take peak point current with zero passage detection signal to be controlled.
The above is only the preferred embodiment of the present invention, it is noted that above-mentioned preferred embodiment is not construed as pairLimitation of the invention, for those skilled in the art, without departing from the spirit and scope of the present invention, alsoSeveral improvements and modifications can be made, these modifications and embellishments should also be considered as the scope of protection of the present invention, here no longer with implementationExample repeats, and protection scope of the present invention should be defined by the scope defined by the claims..In addition, what is be related in patent is all" electrically connecting ", " connecing " and " connection " relationship not singly refers to that component directly connects, and referring to can lead to according to specific implementation situationIt crosses addition or reduces couple auxiliary, Lai Zucheng more preferably coupling structure is clearly only with the place of " electrically connecting " in the present inventionEmphasize this meaning, but the place that use " connecing " and " connection " is not precluded also has such meaning.