Control circuit in a kind of circuit of power factor correction
Technical field
The present invention relates to power factor correction technology field, the control circuit particularly in a kind of circuit of power factor correction.
Background technology
At two-stage circuit or single-level power factor correction (PFC, PowerFactorCorrection) in circuit, the method that control circuit adopts usually is: at the main switch turn-on instant of pfc circuit, constant-current source charges to an electric capacity, the voltage of electric capacity is started from scratch increase, when increasing to equal with the feedback signal of PFC output, the main switch controlling pfc circuit turns off.And during stable state, in the one-period of the input voltage of pfc circuit, the amplitude of the feedback signal of PFC output is relatively constant, therefore, in the one-period of the input voltage of pfc circuit, the ON time of main switch is also constant, makes the peak value of main switch electric current follow the change of input voltage like this.
The input current of pfc circuit can be made like this to follow the change of input voltage, make input current Iin(ac input end in whole circuit) identical with input voltage vin phase place.As shown in Figure 1, this figure is input current Iin(ac input end in prior art) schematic diagram identical with input voltage vin phase place.
But in order to reduce, the high frequency of electrical network is polluted, at input or the output parallel filtering electric capacity of rectifier bridge, or at the input of rectifier bridge and the equal parallel filtering electric capacity of output.Input current Iin(ac input end in whole circuit will be caused like this) with input voltage vin, there is phase difference.This is because, the input current Iin(ac input end of whole circuit) be the input current sum of the electric current on filter capacitor and pfc circuit, and the phase place of electric current on filter capacitor is ahead of input voltage 90 degree, namely due to the existence of filter capacitor, the phase place of input current Iin is made to be ahead of the phase place of input voltage vin, like this due to the phase place of input current Iin and the phase place of input voltage vin inconsistent, cause that the power factor of power supply reduces, harmonic content increase.
In sum, how making the phase place of input current Iin and input voltage vin be consistent, will be those skilled in the art's technical issues that need to address.
Summary of the invention
The technical problem to be solved in the present invention is to provide the control circuit in a kind of circuit of power factor correction, and the phase place of input current Iin and input voltage vin can be made to be consistent.
The embodiment of the present invention provides the control circuit in a kind of circuit of power factor correction, comprising: output feedack module, waveform generation module, control signal generation module and drive control module;
Described output feedack module, for the output electric parameter of the described circuit of power factor correction PFC that samples, compares the output electric parameter of sampling with preset value, according to comparative result output feedback signal Vf;
Described waveform generation module, the secondary signal I2 that the electric current for generation of the filter capacitor to the input and/or output that are connected in parallel on rectifier bridge is relevant;
Described control signal generation module, for the feedback signal Vf that exports according to described output feedack module and and secondary signal I2 export control signal;
Described drive control module, drives described main switch for the control signal exported according to described control signal generation module, and controls the ON time of described main switch.
Preferably, described control signal generation module comprises: charhing unit and comparator;
Described charhing unit comprises current source and electric capacity;
Described current source and described secondary signal I2 are that described electric capacity charges;
Voltage on described electric capacity is input to an input of described comparator;
Described feedback signal Vf is input to another input of described comparator;
The output of described comparator exports described control signal to described drive control module.
Preferably, described secondary signal I2 is current signal.
Preferably, described control signal generation module comprises: charhing unit and comparator;
Described charhing unit comprises current source and electric capacity;
Described current source is that described electric capacity charges;
Voltage on described electric capacity is input to an input of described comparator;
Another input of described comparator is input to after the secondary signal I2 that described waveform generation module exports and described output feedack module output signal Vf superposes;
The output of described comparator exports described control signal to described drive control module.
Preferably, described secondary signal I2 is voltage signal.
Preferably, described waveform generation module comprises: the first electric capacity and the first resistance;
The output of described rectifier bridge is connected in parallel on after described first electric capacity and the first resistant series;
The signal that described resistance produces is as described secondary signal I2.
Preferably, described waveform generation module comprises: the first electric capacity, the first resistance and the second resistance;
The output of described rectifier bridge is connected in parallel on after described first electric capacity and the first resistant series;
One end of described second resistance connects the common port of described first electric capacity and the first resistance;
The signal that the other end of described second resistance exports is described secondary signal I2.
Preferably, also filtration module is comprised;
The secondary signal I2 that described waveform generation module exports exports after described filtration module filtering.
Preferably, the capacitance of described filter capacitor and the capacitance positive correlation with the electric capacity in described waveform generation module.
Preferably, the capacitance of described filter capacitor and the capacitance positive correlation with the electric capacity in described waveform generation module.
Compared with prior art, the present invention has the following advantages:
Utilize Waveform generating circuit to produce a secondary signal I2 relevant to filter capacitor electric current, and produced the control signal controlling main switch state by secondary signal I2 and feedback signal Vf.According to the secondary signal I2 relevant to filter capacitor electric current, the ON time controlling main switch makes the input current Ip of pfc circuit and total filtered circuit Ic sum, namely the input current Iin of AC is identical with the phase place of input voltage vin, thus the phase difference eliminated because filter capacitor causes, cause the phase place of Iin and Vin not identical.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is input current Iin(ac input end in prior art) schematic diagram identical with input voltage vin phase place;
Fig. 2 is control circuit embodiment one schematic diagram in circuit of power factor correction provided by the invention;
Fig. 3 is control circuit embodiment two schematic diagram in circuit of power factor correction provided by the invention;
Fig. 4 a is charhing unit cut-away view provided by the invention;
Fig. 4 b is mains voltage oscillogram provided by the invention;
Fig. 4 c is the schematic diagram that charhing unit provided by the invention and I2 charge jointly;
Fig. 4 d is main electrical current oscillogram provided by the invention;
Fig. 5 is the waveform generation module schematic diagram that the embodiment of the present invention provides;
Fig. 6 is control circuit embodiment three schematic diagram in circuit of power factor correction provided by the invention;
Fig. 7 is control circuit embodiment four schematic diagram in circuit of power factor correction provided by the invention.
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.
For enabling above-mentioned purpose of the present invention, feature and advantage become apparent more, are described in detail the specific embodiment of the present invention below in conjunction with accompanying drawing.
Embodiment one:
See Fig. 2, this figure is control circuit embodiment one schematic diagram in circuit of power factor correction provided by the invention.
Control circuit in the circuit of power factor correction that the embodiment of the present invention provides, comprising: waveform generation module 200, output feedack module 300, drive control module 400 and control signal generation module 500;
Described output feedack module 300, for the output electric parameter of the described circuit of power factor correction PFC100 that samples, compares the output electric parameter of sampling with preset value, according to comparative result output feedback signal Vf;
It should be noted that, the electric parameter that described circuit of power factor correction PFC100 exports can be voltage signal, also can be current signal.
It should be noted that, the pfc circuit 100 in the present embodiment, for Boost circuit, as shown in Figure 2, comprises inductance L, diode D and main switch S1 and the first resistance R1.
Be understandable that, pfc circuit 100 can also be other forms of DC-DC circuit.In addition, pfc circuit 100 can be that constant voltage exports, and rear class connects DC-DC constant current output circuit; Or pfc circuit can also be the single-stage PFC circuit of constant current output.
Described waveform generation module 200, the secondary signal I2 that the electric current for generation of the filter capacitor to the input and/or output that are connected in parallel on rectifier bridge is relevant;
It should be noted that, I2 is relevant to the electric current of described filter capacitor, refer to the directly proportional signal of electric current of I2 and filter capacitor, or I2 has similar waveform to the electric current of filter capacitor.Be understandable that, here similar comprises identical, but in the circuit of reality, due to the existence of electric component, being difficult to two identical situations of waveform, is all generally waveform similarity roughly.
It should be noted that, described filter capacitor may be connected in parallel on the output of rectifier bridge, also may the output of rectifier bridge and input all in parallel.
Described control signal generation module 500, for the feedback signal Vf that exports according to described output feedack module 300 and and secondary signal I2 export control signal;
Described drive control module 400, drives described main switch for the control signal exported according to described control signal generation module 500, and controls the ON time of described main switch.
Wherein, the ON time of described main switch, refers to that main switch is in the time of conducting state.As, the time interval from the turn-on instant of main switch to the shutoff moment.
As being the control circuit that the embodiment of the present invention provides in the empty frame of the latter half in Fig. 2.
Control circuit in the circuit of power factor correction that the present embodiment provides, utilize Waveform generating circuit to produce a secondary signal I2 relevant to filter capacitor electric current, and produced the control signal controlling main switch state by secondary signal I2 and feedback signal Vf.According to the secondary signal I2 relevant to filter capacitor electric current, the ON time controlling main switch makes the input current Ip of pfc circuit and total filtered circuit Ic sum, namely the input current Iin of AC is identical with the phase place of input voltage vin, thus the phase difference eliminated because filter capacitor causes, cause the phase place of Iin and Vin not identical.
Embodiment two:
The control signal generation module that the embodiment of the present invention provides mainly is introduced below in conjunction with accompanying drawing.
See Fig. 3, this figure is control circuit embodiment two schematic diagram in circuit of power factor correction provided by the invention.
The described control signal generation module that the present embodiment provides comprises: charhing unit 501 and comparator O1;
Described charhing unit 501 comprises current source Id and electric capacity Ct; Specifically can see Fig. 4 c.
Described current source Id and described secondary signal I2 is that described electric capacity Ct charges;
Voltage on described electric capacity Ct is input to an input of described comparator O1;
Described feedback signal Vf is input to another input of described comparator O1;
The output of described comparator O1 exports described control signal to described drive control module 400.
Drive control module 400 is by controlling the ON time of main switch S1, and control the current peak of main switch S1, thus make the input current Ip of pfc circuit and total filtered circuit Ic sum, namely the input current Iin of AC is identical with the phase place of input voltage vin.
It should be noted that, in the embodiment two of Fig. 3, the secondary signal I2 charged for the electric capacity Ct in described charhing unit 501 needs to be current signal, and namely in this embodiment, the secondary signal requiring waveform generation module 200 to export is current signal.
Below in conjunction with Fig. 4 a-Fig. 4 d, namely corresponding in Fig. 3 several current waveform figures, the operation principle of the embodiment two of analysis chart 3 correspondence:
The charhing unit cut-away view that Fig. 4 a provides for the present embodiment, namely comprises electric capacity Ct and current source Id; Current source Id is electric capacity Ct and charging, and the voltage on electric capacity Ct is input to an input of comparator O1;
The operation principle of charhing unit is described below in conjunction with Fig. 3 and Fig. 4 c.
When waveform generation module 200 does not act on charhing unit 501, namely in corresponding diagram 4a, I2 does not charge to Ct.
When the switching tube S1 of PFC main circuit 100 is from turning off the moment being switched to conducting state, in described charhing unit, the voltage on electric capacity Ct is zero; After this, in switching tube S1 ON time, this electric capacity Ct due to current source Id be its charging, therefore, the voltage V1 on electric capacity Ct rises with constant slope, as shown in Figure 4 b, until increase to the moment equal with feedback signal Vf, comparator O1 exports control signal, and is turned off by the switching tube S1 of driver control circuit control PFC main circuit, therefore, the voltage on electric capacity Ct is the ON time Ton of PFC main circuit switch pipe S1 from the time that zero increases to Vf;
When waveform generation module 200 acts on charhing unit, it is current signal that waveform generation module 200 outputs signal I2, this signal I2 together with the current source Id in charhing unit for electric capacity Ct charges, as illustrated in fig. 4 c; Voltage V1 on electric capacity Ct increases from zero, but unlike, its slope is no longer constant-slope, but change with certain rule, the trend of this change is identical with the waveform of signal I2, make V1 contrary with I2 from the variation tendency of the time Ton of zero to Vf, also be, the change of Ton in the one-period of input voltage contains the impact of signal I2, and I2 is the signal relevant to filter capacitor electric current, therefore, the phase place of the envelope Ip ' of the current peak of switching tube is changed, eliminates the impact of filter capacitor.
As can be seen from Fig. 4 d, the cycle of described secondary signal I2 is identical with the cycle of input voltage Vdc; Described secondary signal I2 is reduced to negative amplitude from positive amplitude in one-period.
See Fig. 5, this figure is the waveform generation module schematic diagram that the embodiment of the present invention provides.
Described waveform generation module comprises: the first electric capacity Cb, the first resistance Rb and the second resistance R1;
Described first electric capacity Cb and the first resistance Rb is connected in parallel on the output of described rectifier bridge after connecting;
One end of described second resistance R1 connects the common port of described first electric capacity Cb and the first resistance Rb;
The signal that the other end of described second resistance R1 exports is described secondary signal I2.
It should be noted that, described electric capacity Cb also can be the filter capacitor C2 itself after rectifier bridge, and namely C2 is connected in parallel on the output of rectifier bridge after connecting with resistance Rb, and its points of common connection connects described resistance R1, and the current signal on R1 is as described secondary signal I2.
It should be noted that, the capacitance of described electric capacity Cb, relevant to the capacitance of filter capacitor C1 and C2, also, the capacitance of C1 with C2 and become positively related relation with the capacitance of Cb.The capacitance size of Cb depends on the capacitance size of C1 and C2, when the capacitance summation of filter capacitor in circuit increases, can, by increasing the capacitance of electric capacity Cb, make input current Iin identical with the phase place of input voltage vin.
It should be noted that, described Waveform generating circuit can be realized by digital circuit, produces one and the directly proportional waveform of filter capacitor current waveform.
The concrete principle of control circuit provided by the invention is described in detail below in conjunction with above accompanying drawing.
In the above-described embodiments, I2 and filter capacitor current in proportion, in the half period of input voltage, I2 is identical with the cycle of input voltage Vdc, phase 90 °, so establish:
Vdc=V*sinωt(1)
Wherein, V is the peak value of input voltage Vdc.
Due to secondary signal I2 and filter capacitor current in proportion, and the voltage on filter capacitor is Vdc, and therefore, filter capacitor electric current and input voltage Vdc phase 90 °, therefore, suppose
I2=k2*cosωt
Wherein, k2 is the peak value of secondary signal I2.
Circuit structure according to Fig. 4 c can calculate Ton, specific as follows:
(Id+I2)*Ton=Ct*Cf
(Id+k2*cosωt)*Ton=Ct*Vf
Therefore, according to above formula switching tube current peak Ip ' as shown in figure 4d, compared with input voltage Vdc=V*sin ω t, can find out, the phase place of switching tube current peak Ip ' lags behind the phase place of input voltage Vdc, and namely in Fig. 4 (d), B point lags behind A point.
It should be noted that, in control signal generation module in the control circuit that Fig. 3 embodiment provides, waveform generation module acts in charging module, present invention also offers an embodiment, wherein waveform generation module acts in output voltage feedback module, describes its operation principle in detail below in conjunction with physical circuit figure.
Embodiment three:
See Fig. 6, this figure is control circuit embodiment three schematic diagram in circuit of power factor correction provided by the invention.
Described control signal generation module comprises charhing unit 501 and comparator O1;
Described charhing unit 501 for: be capacitor charging by current source, and the voltage on electric capacity be input to an input of described comparator O1;
The feedback signal Vf that described output feedack module 300 exports is input to another input of comparator O1;
Described waveform generation module 200, acts in output feedack module 300; Namely another input outputting to comparator O1 after I2 superposes with feedback signal Vf is outputed signal.
It should be noted that, output signal I2 superposes what refer to feedback signal Vf be exactly two signal plus.
It should be noted that, in the embodiment three of Fig. 6, it is voltage signal that described output feedack module 300 outputs signal Vf, and therefore, in the present embodiment, the secondary signal I2 requiring waveform generation module 200 to export is voltage signal.
Described comparator O1 exports described control signal to described drive control module 400.
Drive control module 400 is by controlling the ON time of main switch S1, and control the current peak of main switch S1, thus make the input current Ip of pfc circuit and total filtered circuit Ic sum, namely the input current Iin of AC is identical with the phase place of input voltage vin.
The operation principle of this embodiment is similar to principle embodiment illustrated in fig. 3, output feedback signal Vf compensates (or superposition) secondary signal I2, and compare with the voltage V1 that charhing unit 501 exports, the ON time Ton of main switch S1 is changed along with the secondary signal I2 change compensated, and secondary signal I2 is relevant to the electric current of filter capacitor, therefore, cancellation filter capacitor electric current in the electric current of main switch S1, make the input current Ip of PFC main circuit and total filter capacitor electric current I c sum (i.e. total input current Iin), with input voltage vin same-phase, and eliminate the phase difference problem that filter capacitor C1 and/or C2 cause.
Due in the embodiment shown in Fig. 6, waveform generation module 200 acts in output feedack module 300, and output signal I2 need superpose with feedback signal Vf, and require that secondary signal I2 is voltage signal, therefore, the specific embodiment of waveform generation module 200 as shown in Figure 7.With the specific embodiment of the waveform generation module 200 shown in Fig. 5 unlike, in the embodiment shown in Fig. 7, waveform generation module 200 only includes the first electric capacity Cb and the first resistance Rb that are connected in series,
Described first electric capacity Cb and the first resistance Rb is connected in parallel on the output of described rectifier bridge after connecting;
The signal that described resistance produces is as described secondary signal I2.
Current source Id in comparator O1 in the application, drive control module 400 and charhing unit 501 can be integrated circuit, as integrated chip.Electric capacity Ct in waveform generation module 200, output feedack module 300 and charhing unit 501 can be then the peripheral circuit of integrated circuit (or chip), as the analog circuit that discrete component is formed.
The above is only preferred embodiment of the present invention, not does any pro forma restriction to the present invention.Although the present invention discloses as above with preferred embodiment, but and be not used to limit the present invention.Any those of ordinary skill in the art, do not departing under technical solution of the present invention ambit, the Method and Technology content of above-mentioned announcement all can be utilized to make many possible variations and modification to technical solution of the present invention, or be revised as the Equivalent embodiments of equivalent variations.Therefore, every content not departing from technical solution of the present invention, according to technical spirit of the present invention to any simple modification made for any of the above embodiments, equivalent variations and modification, all still belongs in the scope of technical solution of the present invention protection.