Background technology
In existing common power factor correction (PFC, Power Factor Correction) scheme, mainly contain PPFC (Passive Power Factor Correction) and Active Power Factor Correction dual mode.The PPFC (Passive Power Factor Correction) mode is made of reactor and electric capacity, and its raising degree is limited, cost is high and device volume is big.The Active Power Factor Correction mode is exactly the so-called active PFC circuit that added inductance and switching device formation before electric capacity behind the rectifier bridge, but sort circuit frequency height, the loss of switching device is very big, can produce serious electromagnetic interference problem, and cost is higher.
Disclose the method for a kind of continuous-current plant and regulation voltage in No. 200510100254.1, the Chinese patent application, wherein continuous-current plant comprises AC power Vin, the rectification circuit that the alternating current that AC power is exported carries out rectification, be connected the filter capacitor E1 of rectification circuit dc output end, be connected the reactor between AC power and the rectification circuit ac input end, the AC power short circuit forced short circuit current that reactor is switched on, detect the zero passage detection link of ac power frequency and AC supply voltage zero crossing, the gate driving link, the Vdc that detects rectification circuit dc output end magnitude of voltage detects link, the Vdc in parallel with filter capacitor E1 detects the potential-divider network of link, and connection zero passage detection link, gate driving link and Vdc detect the control chip of link; Also disclose a kind of method that adopts the half switching regulator raising power factor of low frequency in this patent application, just in a half-wave, made the several pulses of power switch pipe switch the early stage of rectifier bridge conducting, reduced the purpose of disturbing and reducing switching loss and reach.Yet, the composition of disclosed continuous-current plant and function imperfection also in the above-mentioned patent application, though wherein the half switching regulator power factor correction mode of Cai Yonging solves electromagnetic interference and the big problem of switching loss that the power switch high frequency produces in the common Active Power Factor Correction mode, but still exist not enough, be only to make the leading portion of current impulse that the sinusoidal electric current that rises is arranged in the existing half switching regulator Active Power Factor Correction mode, though current waveform makes moderate progress but is not ideal enough like this, power factor is not high enough, and harmonic emissions can't reach authentication requesting under many circumstances.
Summary of the invention
The purpose of this invention is to provide a kind of continuous-current plant, have more perfect power factor emendation function.
Above-mentioned purpose is realized by following technical scheme:
A kind of continuous-current plant comprises AC power Vin, the rectification circuit that the alternating current that AC power is exported carries out rectification, be connected the filter capacitor E1 of rectification circuit dc output end, be connected the reactor between AC power and the rectification circuit ac input end, the AC power short circuit forced short circuit current that reactor is switched on, detect the zero passage detection link of ac power frequency and AC supply voltage zero crossing, the gate driving link, the Vdc that detects rectification circuit dc output end magnitude of voltage detects link, the Vdc in parallel with filter capacitor E1 detects the potential-divider network of link, and connection zero passage detection link, gate driving link and Vdc detect the control chip of link; It is characterized in that, comprise that also the alternating current that obtains the alternating current effective value detects link, is connected with control chip.
Another purpose of the present invention is at the deficiency of existing low frequency half switching regulator power factor correction scheme, and a kind of method that improves above-mentioned continuous-current plant power factor is provided, and can further improve current waveform, improves power factor.
Above-mentioned another purpose is realized by following technical scheme:
A kind of method that improves above-mentioned supply unit power factor is characterized in that, comprises the steps:
(1) limits value of PWM duty ratio is set in the program of control chip; (2) obtain the output frequency of AC power by the zero passage detection link, and this supply frequency value is stored in the control chip as known quantity;
(3) by the zero passage detection link AC-input voltage is carried out zero passage detection, in the early stage of rectification circuit conducting, control chip makes reactor force the short circuit AC power by gate driving link conducting power device; In the later stage of rectifier bridge conducting, control chip passes through gate driving link conducting power device once more, makes reactor force the short circuit AC power once more.
A further object of the present invention is when improving power factor, to provide a kind of method of regulating above-mentioned continuous-current plant output voltage.
An above-mentioned purpose is again realized by following technical scheme:
One voltage setting value is set in the control chip program, this value constitutes voltage close loop control with the output dc voltage signal that feeds back to chip, when being lower than set point, output voltage make current lead-through early stage and later stage power tube ON time increase or increase the number of conducting pulse by the algorithm in the program, program obtains in detection under the prerequisite of alternating current effective value checking in scale factor corresponding to detected current effective value by look-up table then, the conducting pulsewidth time in this scale factor and the voltage close loop control multiply each other and the final ON time of output.
Compared with the prior art, the continuous-current plant that provides among the present invention comprises that also alternating current detects link, be used to obtain the effective value of alternating current, thereby can provide an important parameter for power factor improves process and regulates the output voltage process, make this continuous-current plant have more perfect power factor emendation function.Compare with existing half switching regulator Active Power Factor Correction mode, the method that improves power factor among the present invention not only makes reactor force the short circuit AC power to improve current waveform in the rectifier bridge current lead-through in earlier stage, but also make reactor force the short circuit AC power in the later stage of rectifier bridge current lead-through, thereby the sinusoidal Du Genggao of the input current waveform that makes AC power, more higher harmonics emission amplitude is littler for power factor.The present invention also provides a kind of method of regulating above-mentioned continuous-current plant output voltage when improving power factor, make that output voltage can real-time regulated.
Embodiment
Figure 1 shows that a kind of continuous-current plant that is applicable to compressor of air conditioner, this continuous-current plant comprises AC power Vin, the rectification circuit that the alternating current that AC power is exported carries out rectification, be connected the filter capacitor E1 of rectification circuit dc output end, be connected the reactor L between AC power Vin and the rectification circuit ac input end, with the AC power short circuit, force the short circuit current that reactor is switched on, detect the zero passage detection link of ac power frequency and AC supply voltage zero crossing, alternating current detects link, the gate driving link, the Vdc that detects rectification circuit dc output end magnitude of voltage detects link, the potential-divider network that above-mentioned Vdc detects link and filter capacitor E1 parallel connection be connected the zero passage detection link, gate driving link and Vdc detect the control chip of link.
In the present embodiment, short circuit current comprises a device for power switching Z1 and two diode D5, D6, the common cathode of diode D5, D6 connects the collector electrode of device for power switching Z1, device for power switching Z1 is an insulated gate bipolar transistor IGBT, and device for power switching Z1 also can be other power-type device certainly.
In the present embodiment, rectification circuit is a bridge rectifier, the common anode of bridge rectifier connects the emitter of device for power switching Z1, between the anode, Vdc detects the potential-divider network of link and the two ends that power driving circuit is connected in parallel on output filter capacitor E1 to the common cathode that filter capacitor E1 is connected on bridge rectifier together.Reactor L, diode D5, D6, filter capacitor E1 and device for power switching Z1 have constituted the boost type translation circuit.
For the situation of avoiding causing circuit devcie to damage owing to the pulse duration of compensation is wide takes place; this continuous-current plant also comprises the over-current detection link; can be by the abnormal current signal of the real-time detection power switching device of over-current detection link collector electrode; when the abnormal current signal occurring; by the shutoff operation of control chip execution, to reach the purpose of protection device for power switching to device for power switching Z1.
Fig. 2 is a kind of specific implementation of gate driving link and over-current detection link in this continuous-current plant.Wherein, gate driver circuit is by resistance 13; resistance 15; resistance 16; resistance 17; resistance 18; triode T1; triode T2 and triode T3 constitute; triode T3 base stage is connected with control chip by resistance 13; the collector electrode of triode T3 connects the base stage of triode T1 and the base stage of triode T2; the emitter of the emitter of triode T1 and triode T2 connects the grid of device for power switching Z1 by resistance 17; resistance 15 is connected on the collector electrode of triode T1; resistance 16 is connected on the collector electrode of triode T3; resistance 18 is connected in parallel between the grid and source electrode of device for power switching Z1, plays protection device for power switching Z1.(low level is effective) triode T3 turn-offs when the signal PT that gives resistance R 13 is low level, the collector electrode of T3 also is T1, the base stage of T2 is a high level, because triode T1 is a NPN type and T2 is a positive-negative-positive, so T1 manages conducting, T2 manages shutoff, and power supply is given device for power switching Z1 gate charges and conducting by R15, T1, R17; Triode T3 conducting when signal PT is high level, the base stage of triode T1 and T2 is a low level, and this moment, T1 turn-offed, and the T2 conducting is gone into ground to device for power switching Z1 gate charge bleed off, and device for power switching Z1 turn-offs.Please continue to consult Fig. 2; over-current detection circuit is by resistance 19; resistance 20; capacitor C 11; triode T4 and resistance 14 constitute; adopt resistor R 19 to sample; the signal of its output compares with the basic source PN junction voltage of triode behind the RC circuit; triode T4 conducting output significant level is given control chip when sampled signal reaches PN junction voltage; because triode PN junction voltage is the negative temperature coefficient parameter; thereby the reduction of PN junction voltage reduces the restriction current value of power device electric current accordingly when ambient temperature is too high, thereby can protect power device accordingly when high temperature.
Figure 3 shows that the another kind of execution mode of gate driving and over-current detection link in the continuous-current plant; in the gate driving part; wherein; gate driver circuit is by resistance 13; resistance 15; resistance 16; resistance 17; resistance 18; triode T1; triode T2 and photoelectric isolating device OPTO1 constitute; photoelectric isolating device OPTO1 base stage is connected with control chip by resistance 13; the emitter of photoelectric isolating device OPTO1 connects the base stage of triode T1 and the base stage of triode T2; the emitter of the emitter of triode T1 and triode T2 connects the grid of device for power switching Z1 by resistance 17; resistance 15 is connected on the collector electrode of triode T1; resistance 16 is connected on the emitter of photoelectric isolating device OPTO1; resistance 18 is connected in parallel between the grid and source electrode of device for power switching Z1, plays protection device for power switching Z1.Please continue to consult Fig. 3, over-current detection circuit is by resistance 19, resistance 20, capacitor C 11, photoelectric isolating device OPTO2 and resistance 14, adopt resistor R 19 to sample, the signal of its output compares with the PN junction voltage of photoelectric isolating device OPTO2 behind the RC circuit, and photoelectric isolating device OPTO2 conducting output significant level is given control chip when sampled signal reaches PN junction voltage.
Control chip can be digital signal processor (DSP), also can be single-chip microcomputer.Control chip detects the frequency of alternating current input power supplying and the zero crossing of AC-input voltage by the zero passage detection link, detect the magnitude of voltage that link detects dc output end by Vdc, detect link by alternating current and detect the effective value that exchanges the survey electric current, whether the collector electrode by over-current detection link detection power switching device exists unusual over-current signal, and according to above detection information, by gate driving link output pulse signal, by the motor driven link to the power driving circuit output pwm signal, this power driving circuit is by means of the break-make control to group of switching elements, with the dc voltage conversion of this continuous-current plant output is pulse width modulation (Pulse WidthModulation) voltage, drives the cooler compressor motor and carries out work.
Power factor correcting method provided by the invention comprises the steps:
The limits value of at first setting the duty ratio of PWM in the program of control chip lost efficacy because of overcurrent to prevent reactor and power device.
Detect the zero crossing of AC supply voltage then by the zero passage detection link, after obtaining the moment of a plurality of zero crossings, calculate the difference of adjacent two zero crossings between the moment by control chip, judge the output frequency (for example: 50Hz or 60Hz) of AC power with this, and this supply frequency value is stored in the control chip as known quantity, as after pulse controlled basis.
By the zero passage detection link AC-input voltage is carried out zero passage detection afterwards, after detecting alternating voltage zero-crossing point, after control chip postpones certain hour, by gate driving link output pulse signal, triggering is to the conducting operation of device for power switching Z1, make AC power carry out the short circuit operation, force to give reactor L charging by reactor L.After postponing 1ms, switch-off power switching device Z1, thus and improve current waveform in earlier stage in the conducting of electric current by reactor L afterflow.When reducing this fast, current peak electric current later certainly exists the very high low-frequency harmonics of amplitude, in order to address this problem, increase the conducting angle of electric current, behind time-delay 7ms (apart from the zero passage detection point),, carry out reactor short circuit operation just at conducting later stage of electric current conducting power device once more.Thereby reach the purpose of improving the electric current falling waveform.So moving in circles, increasing exchanges at the front and back of current peak short-circuit reactance device with this and import the conducting angle of source current,, suppressing the purpose of supply harmonic to reach the power factor that increases power supply.
In the present embodiment, the time of above-mentioned time of delay (as 1ms, and 7ms) and pulse duration need be adjusted according to the effective value (detecting link by alternating current gets) and the parameters such as output voltage values of voltage setting value and feedback of supply frequency (being got by the over-current detection signal), alternating current.Alternating current is big more, and the reactor duration of short circuit that needs is long more.For example supply frequency is 50Hz, and according to the difference of alternating current, can select between 0.7ms~2.5ms time of delay electric current rising stage, and the delay time of electric current decrement phase can be selected between 7ms~9ms.ON time also can be adjusted accordingly.
In order when improving power factor, to have the function of voltage-regulation concurrently, a voltage setting value is set in the control chip program, this value constitutes voltage close loop control with the output dc voltage signal that feeds back to chip.When being lower than set point, output voltage make current lead-through early stage and later stage power tube ON time increase or increase the number of conducting pulse by the algorithm in the program, program obtains in detection under the prerequisite of alternating current effective value checking in scale factor corresponding to detected current effective value by look-up table then, the conducting pulsewidth time in this scale factor and the voltage close loop control multiply each other and the final ON time of output.
Figure 4 shows that the oscillogram that improves the method for power factor among the present invention.Wherein because the perceptual hysteresis characteristic of air-conditioning load current, in the rising stage of alternating current number of pulses few (in order to reduce switching loss) but the width of pulse is big.Width in the decrement phase pulse of alternating current is little of to suppress high order harmonic component as far as possible.The total inductance amount of reactor is chosen between 10mH~20mH is advisable.In order to reduce noise, the reactor that can choose a plurality of small electric sensibility reciprocals is connected and is replaced one than the big inductance quantity reactor.For example, can select the reactor series connection of two 8mH small inductor amounts, perhaps select the reactor series connection of three 5.5mH small inductor amounts, substitute the reactor of the big inductance quantity of a 16mH.Preferably select the identical reactor of inductance value, the number of reactor is advisable with two or three.
The continuous-current plant that the foregoing description provides, the method that improves its power factor and regulate its output voltage all are for fully openly the present invention, can not be considered to the restriction to claim of the present invention.If those skilled in the art has made change unsubstantiality, conspicuous or improvement according to the present invention, all should belong to the scope of claim protection of the present invention.