CN105700602A - A constant current and constant voltage control method and circuit for primary side feedback - Google Patents

Abstract

The invention provides a constant current and constant voltage control method and circuit for primary side feedback. The circuit comprises a demagnetizing time converter which is used for detecting demagnetizing time and converting the demagnetizing time into demagnetizing time voltage signals; a frequency adjuster used for generating constant voltage clock frequency control signals; an oscillator which generates sawtooth signals under the control of the constant voltage clock frequency control signals, and generates constant current clock start signals by comparing the values of the sawtooth signals and the values of the demagnetizing time voltage signals or generates constant voltage clock start signals by comparing the values of the sawtooth signals and the values of preset constant voltage and constant current dividing voltage. A novel method is used for generating the CC/CV start clock signals and one start clock generator can be shared, so that the problem of time sequence competition possibly caused by two paths of signals is effectively solved; an oblique wave generating circuit is removed so that the cost is reduced; the generation of high frequency signals is not needed, so that the risk of a parasitic effect is prevented.

Description

A kind of constant current constant voltage control method for primary side feedback and circuit

Technical field

The invention belongs to electronic circuit technology field, relate to a kind of constant current constant voltage control method and system, particularly relate to a kind of constant current constant voltage control method for primary side feedback and circuit。

Background technology

In the circuit implementations of existing primary side feedback control chip, owing to constant current or constant pressure control system are relatively complicated, constant-current circuit is that the circuit adopting two-way different processes respectively with the usual way of constant voltage circuit。

Shown in Figure 1, primary side feedback constant-current constant-voltage controller 100 includes: degaussing time (Tdis) detector 101, is used for detecting the degaussing time, produces the signal of judgement CC/CV (constant current/constant voltage)；Agitator 102, is used for producing clock start signal；Line compensation generator 103, is used for producing line compensation dosage；CV controls module 104, is used for producing CV and controls open frequency control signal；FB sampling holder 105, is used for FB signal of sampling, and sampling produces signal 203；Operational amplifier 106, for amplifying reference voltage V REF and the difference of signal 203, the voltage signal 204 that output and voltage signal 203 are inversely proportional to, voltage signal 204 is also inversely proportional to system output voltage 210；Line current comparator 107, is used for judging that line current reaches on-off switching tube 117 during peak value；Trigger 108, is used for controlling switching tube 117 conducting and turns off；Driver 109, drives switching tube 117 for digital logic signal is changed into driving signal；Forward position effect module 110, for producing voltage signal 215 after being processed by peak value sampling signal 209；PWM/PFM controller 111, is used for switching CC/CV and opens clock selecting；Sampling resistor 112, for sampled peak sampled signal 209；Resitstance voltage divider 113 and 114, for producing the feedback signal 211 of outfan, i.e. voltage division signal 211；Resistor 115, capacitor 116, and diode 122, for providing the supply voltage 123 of chip 100；Transformer Winding 121, for the energy of main coil is delivered to secondary, by primary side winding 124, secondary windings 119, auxiliary winding 120 forms；Electric current 212 is the electric current flowing through system load 122, and voltage 210 is the voltage of system load 122。

Fig. 2 shows the degaussing time detector 101 in circuit shown in Fig. 1, and agitator 102, CV controls module 104 and the specific implementation of PWM/PFM controller 111 and mutual relation。

Primary side feedback shown in Fig. 1 controls (abbreviation primary-side-control) principle: main coil charges to electric capacity 116 by resistance 115, and after reaching the cut-in voltage of control chip 110, control chip 110 is started working。When switching tube 117 turns on, input energy is stored in main coil 124；When switching tube 117 closes, transformator 121 can discharge energy, namely by secondary coil 119, energy is discharged into outfan (i.e. load LOAD and output capacitance), and assist winding 120 that output voltage 210 is mapped to voltage division signal 211, namely relevant with output voltage 210 information can be passed through to assist winding 120 to extract, as shown in formula (1)。

$\mathrm{VFB}=\mathrm{Vout}\×\frac{\mathrm{Na}}{\mathrm{Ns}}\×\frac{R2}{R1+R2}---\left(1\right)$

Wherein, change into resistor 113,114 voltage division signal 211 after feedback signal by 121 output voltages 210 of Transformer Winding, represent with VFB。Output voltage 210 represents with Vout,For auxiliary winding and secondary transformer turn ratio, the resistance of R2 and R1 respectively resistor 114 and 113。By formula (1) it can be seen that VFB and Vout is linear, it is possible to carry out constant output voltage Vout by the way of constant VFB voltage, reach the purpose of constant voltage with this。

Inverse-excitation type (flyback) structure of primary-side-control is generally adopted DCM pattern (discontinuous mode), and its CC (constant current) work can be expressed as:

$\mathrm{Iout}=\frac{1}{2}\×\mathrm{Isk}\×\frac{\mathrm{Tmeg}}{T}---\left(2\right)$

Wherein, Iout represents current signal 212, for flowing through the electric current of load 122。What CC to realize be just to maintain in whole process, and Iout is constant。Isk represents the peak current value flowing through load LOAD in a switch periods, has relationship below:

$\mathrm{Duty}\_\mathrm{off}=\frac{\mathrm{Tmeg}}{T}---\left(3\right)$

$\mathrm{Ipk}=\mathrm{Isk}\×\frac{\mathrm{Ns}}{\mathrm{Np}}---\left(4\right)$

Vcs=Ipk × Rcs (5)

Wherein, Tmeg representation switch pipe 117 closes the discharge time of secondary of having no progeny, a switch periods of T representation switch pipe 117, and Rcs represents the resistance of sampling resistor 112,Representing secondary and primary transformers turn ratio, Ipk represents the peak current value flowing through resistance 112 in a switch periods；By formula (2) and (3) it can be seen that keep that Isk and Duty_off is constant that Iout just can be kept constant thus realizing constant current。

When CC works, owing to sampled signal 203 is far below reference voltage (VREF) 207, therefore the output signal 204 of operational amplifier 106 can be clamped at a fixing higher limit Vthh。When switching tube 117 conducting, the electric current on main coil produces peak value sampling signal 209 on resistance 112；Peak value sampling signal 209 compares with the output signal 204 of operational amplifier 106 at comparator 107 place after forward position effect module 110, signal 209 upset of comparator 107 output is height, and then by trigger 108 and driver 109 output drive signal 214 on-off switching tube 117, the peak point current of actual Ipk just can be controlled。If the peak point current that can keep each Ipk is constant,For primary and secondary transformer turn ratio, it is fixed value for system, by formula (4) it can be seen that Isk just can be constant。

Additionally, realize the Duty_off that CC work also needs to keep constant。As it is shown on figure 3, include Tmag in a cycle T to represent the degaussing time, Ton represents switching tube ON time, and Tdis represents the remaining time removing outside degaussing time and switching tube ON time in cycle T, referring to formula (6)。

T=Tmag+Ton+Tdis (6)

If set in each cycle T:

Tmag=Ton+Tdis (7)

Then,It is constant, has reached the purpose of constant Duty_off, thus realizing CC function。

As shown in Figure 1, for CV (constant voltage) process, when output voltage 210 is lower than preset value time, voltage division signal 211 be 210 feedback signal also can be relatively low, and then amplify through the error of FB sampling holder 105 signal 203 that obtains of sampling with signal (VREF) 207, signal 204 uprises, now signal 204 controls module 104 by CV and can obtain a higher pulse signal of frequency 212, by output energy theorem (6) it can be seen that output voltage 210 can return to normal value。When output voltage 210 is higher than preset value time, in like manner as the same。System output voltage has relationship below:

$\mathrm{Vout}=\frac{1}{2}\×\mathrm{fsw}\×\mathrm{Lp}\×{\mathrm{Ipk}}^2/\mathrm{Iout}---\left(8\right)$

Wherein, fsw represents the turn-on frequency of switching tube, and Lp represents the inductance value of main coil 124。

Visible in conjunction with Fig. 2, the turn-on instant signal 206 of CC is relatively determined by signal 310 and VREF voltage ratio；The turn-on instant signal 212 of CV is compared by a sawtooth waveforms 311 and a fixed voltage signal 204, therefore, the turn-on instant of main switch 117 is determined through PWM/PFM controller 111 logical judgment by 206 and 212, because CC and CV two cover system produces each independent pulse, so there is certain sequential competition risk。Producing additionally, sawtooth waveforms typically requires with the recurrent pulses of a hundreds of K even several million frequencies, this high-frequency impulse is also easy to cause internal a series of ghost effect。

In sum, in the circuit implementations of existing primary side feedback control chip, owing to constant current or constant pressure control system are relatively complicated, constant-current circuit is that the circuit adopting two-way different processes respectively with the usual way of constant voltage circuit, not only circuit is complicated but also cost is bigger, easily cause ghost effect, ghost effect is fatal often to the interference of exquisite system, and processing constant current constant voltage turning point place due to complex time, designing improper being easy to and the situation that misoperation even exports energy concussion occurs。Therefore, how effectively realizing constant current constant voltage control by fairly simple mode, being naturally transitioned into pressure constant state from constant current state is current urgent problem。

Summary of the invention

The shortcoming of prior art in view of the above, it is an object of the invention to provide a kind of constant current constant voltage control method for primary side feedback and circuit, mode two kinds independent is adopted to realize respectively for solving constant current and Isobarically Control in existing primary side feedback control technology, there is sequential competition risk and ghost effect, cause realizing circuit complexity, high in cost of production problem。For achieving the above object and other relevant purposes, the present invention provides a kind of constant-current and constant-voltage control circuit for primary side feedback, the described constant-current and constant-voltage control circuit for primary side feedback includes: degaussing time converter, for detecting the degaussing time, and is changed into degaussing time voltage signal the degaussing time；Frequency adjuster, is used for producing constant voltage clock frequency control signal；Agitator, it is respectively connected with described degaussing time converter and frequency adjuster, sawtooth signal is produced under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal produces constant current clock start signal, or the size comparing described sawtooth signal and default constant pressure and flow demarcation voltage produces constant voltage clock start signal。

Alternatively, described agitator includes: voltage-controlled current source, is connected with described frequency adjuster, exports the first charging current under the control of described constant voltage clock frequency control signal；Sawtooth waveforms generation module, is connected with described voltage-controlled current source, including the first charging capacitor, the first charge switch and the first discharge switch；Described first charging capacitor produces sawtooth signal under the charging of described first charging current；Three input comparators, it is respectively connected with described sawtooth waveforms generation module and degaussing time converter, numerical value the greater or smaller and described sawtooth signal in described degaussing time voltage signal and described default demarcation voltage are compared, output constant current clock start signal or constant voltage clock start signal；The conducting of the first charge switch and the first discharge switch described in described constant current clock start signal or constant voltage clock start signal feedback control turns off, and adjusts the rate of rise of described sawtooth signal or/and amplitude。

Alternatively, described degaussing time converter includes: degaussing time detecting module, detects the degaussing time, exports degaussing time signal；Current source, exports the second charging current；Second charge switch, is respectively connected with described degaussing time detecting module and current source, controls described second charging current the second charging capacitor is charged under the control of described degaussing time signal；Second charging capacitor, closes pipe with described second charging and is connected, export described degaussing time voltage signal。

Alternatively, described frequency adjuster is a comparator or the comparator of at least two parallel connection。

The present invention also provides for a kind of constant current constant voltage control method for primary side feedback, and the described constant current constant voltage control method for primary side feedback includes: the detection degaussing time, and the degaussing time changes into degaussing time voltage signal；Generate constant voltage clock frequency control signal；Sawtooth signal is generated under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal generates constant current clock start signal, or the size comparing described sawtooth signal and default constant pressure and flow demarcation voltage generates constant voltage clock start signal。

Alternatively, the described one generating sawtooth signal under the control of described constant voltage clock frequency control signal realizes process and includes: utilize voltage-controlled current source to export the first charging current under the control of described constant voltage clock frequency control signal；The first charging capacitor is utilized to produce sawtooth signal under the charging of described first charging current；Or utilize the first charge switch of the first charging capacitor described in described constant current clock start signal or constant voltage clock start signal feedback control and the on or off of the first discharge switch, adjust the rate of rise of described sawtooth signal or/and amplitude。

Alternatively, the described detection degaussing time, and the one that the degaussing time changes into degaussing time voltage signal realizes process and includes: utilize the degaussing time detecting module detection degaussing time, export degaussing time signal；Current source is utilized to export the second charging current；Utilize the second charge switch to control described second charging current under the control of described degaussing time signal the second charging capacitor is charged；Described second charging capacitor is utilized to export described degaussing time voltage signal。

Alternatively, the one of described generation constant voltage clock frequency control signal realizes process and includes: the size utilizing comparator to compare coherent signal and reference signal, generates described constant voltage clock frequency control signal；Or utilize the more described coherent signal of comparator of at least two parallel connection and the size of at least two reference signal, generate described constant voltage clock frequency control signal。

As it has been described above, the constant current constant voltage control method for primary side feedback of the present invention and circuit, have the advantages that

Present invention employs a kind of method of novelty and produce CC/CV unlatching clock signal, it is possible to share same unlatching clock generator, effectively prevent the issuable sequential competition problem of two paths of signals；And eliminate ramp generating circuit, provide cost savings；Need not the generation of high-frequency signal, it is to avoid the risk of ghost effect。

Accompanying drawing explanation

Fig. 1 is the electrical block diagram of existing primary side feedback constant-current constant-voltage controller。

Fig. 2 is the partial internal structure schematic diagram of circuit shown in Fig. 1。

Fig. 3 is the work schedule schematic diagram of part signal in circuit shown in Fig. 1 and 2。

Fig. 4 is a kind of application scenarios schematic diagram of the constant-current and constant-voltage control circuit for primary side feedback described in the embodiment of the present invention。

Fig. 5 is a kind of structural representation of the constant-current and constant-voltage control circuit for primary side feedback described in the embodiment of the present invention。

Fig. 6 is the another kind of structural representation of the constant-current and constant-voltage control circuit for primary side feedback described in the embodiment of the present invention。

Fig. 7 is the work schedule schematic diagram of the part signal of the constant-current and constant-voltage control circuit for primary side feedback described in the embodiment of the present invention。

Fig. 8 is a kind of schematic flow sheet of the constant current constant voltage control method for primary side feedback described in the embodiment of the present invention。

The one that Fig. 9 is the step S801 described in the embodiment of the present invention implements schematic flow sheet。

The one that Figure 10 is the partial content of the step S803 described in the embodiment of the present invention implements schematic flow sheet。

Element numbers explanation

400 constant-current and constant-voltage control circuits being used for primary side feedback

415 degaussing time converters

601 degaussing time detecting modules

602 current sources

603 second charge switch

604 second charging capacitors

416 agitators

610 voltage-controlled current sources

611 sawtooth waveforms generation modules

612 3 input comparators

418 frequency adjusters

S801～S803 step

S901～S904 step

S101～S103 step

Detailed description of the invention

Below by way of specific instantiation, embodiments of the present invention being described, those skilled in the art the content disclosed by this specification can understand other advantages and effect of the present invention easily。The present invention can also be carried out by additionally different detailed description of the invention or apply, and the every details in this specification based on different viewpoints and application, can also carry out various modification or change under the spirit without departing from the present invention。

Refer to accompanying drawing。It should be noted that, the diagram provided in the present embodiment only illustrates the basic conception of the present invention in a schematic way, then assembly that in graphic, only display is relevant with the present invention but not component count when implementing according to reality, shape and size drafting, during its actual enforcement, the kenel of each assembly, quantity and ratio can be a kind of random change, and its assembly layout kenel is likely to increasingly complex。

Existing primary side feedback constant-current and constant-voltage control circuit not only structure shown in Fig. 1 is complicated, and cost is big, easily cause ghost effect, especially when processing constant current constant voltage turning point place due to complex time, design improper being easy to and the situation that misoperation even exports energy concussion occurs, therefore, how effectively realizing constant current constant voltage control by fairly simple mode, namely be naturally transitioned into pressure constant state from constant current state be problem to be solved by this invention。

Below in conjunction with embodiment and accompanying drawing, the present invention is described in detail。

The present embodiment provides a kind of constant-current and constant-voltage control circuit for primary side feedback, its application scenarios is as shown in Figure 4, the described constant-current and constant-voltage control circuit 400 for primary side feedback includes: degaussing time converter (Tdis detection) 415, frequency adjuster (PFM) 418, agitator (OSC) 416。

Shown degaussing time converter 415 is used for detecting the degaussing time, and the degaussing time changes into degaussing time voltage signal。Further, as it is shown in figure 5, described degaussing time converter 415 includes: degaussing time detecting module 601, current source 602, the second charge switch 603, the second charging capacitor 604。Described degaussing time detecting module 601 detects the degaussing time, exports degaussing time signal 202。Described current source 602 exports the second charging current。Described second charge switch 603 is respectively connected with described degaussing time detecting module 601 and current source 602, controls described second charging current one second charging capacitor is charged under the control of described degaussing time signal。Described second charging capacitor 604 closes pipe 603 with described second charging and is connected, and exports described degaussing time voltage signal。

Described frequency adjuster 418 is used for producing constant voltage clock frequency control signal。Further, as it is shown in figure 5, described frequency adjuster 418 can be a comparator。Or as shown in Figure 6, described frequency adjuster 418 can be the comparator that at least two is in parallel。

Described agitator 416 is respectively connected with described degaussing time converter 415 and frequency adjuster 416, sawtooth signal is produced under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal produces constant current clock start signal, or relatively described sawtooth signal and presets the size generation constant voltage clock start signal of constant pressure and flow demarcation voltage。Further, as it is shown in figure 5, described agitator 416 includes: voltage-controlled current source 610, sawtooth waveforms generation module 611, three input comparators 612。Described voltage-controlled current source 610 is connected with described frequency adjuster 418, exports the first charging current 509 under the control of described constant voltage clock frequency control signal。Described sawtooth waveforms generation module 611 is connected with described voltage-controlled current source 610, including the first charging capacitor, the first charge switch and the first discharge switch；Described first charging capacitor produces sawtooth signal 510 under the charging of described first charging current。Described three input comparators 612 are respectively connected with described sawtooth waveforms generation module 611 and degaussing time converter 415, numerical value the greater or smaller and described sawtooth signal in described degaussing time voltage signal and described default demarcation voltage are compared, output constant current clock start signal or constant voltage clock start signal 508。The conducting of the first charge switch and the first discharge switch described in described constant current clock start signal or constant voltage clock start signal 508 feedback control turns off, and adjusts the rate of rise of described sawtooth signal or/and amplitude。

The work process for the constant-current and constant-voltage control circuit of primary side feedback described in the present embodiment is:

Described frequency adjuster 418 produces constant voltage clock frequency control signal (i.e. PFM control signal) 507 after voltage signal 506 and reference voltage V REF1 compare process。

Constant voltage clock frequency control signal 507 controls voltage-controlled current source 610 and produces electric current 509。When switching 614 Guan Bi, electric current 509 charges to electric capacity 615, or electric current 509 charges to electric capacity 618 when switching 617 Guan Bi；And when switching 616 Guan Bi, electric capacity 615 discharges over the ground；When switching 619 Guan Bi, electric capacity 618 discharges over the ground。Switch 614 and switch 617 broadly fall into above-mentioned first charge switch；Electric capacity 615 and electric capacity 618 broadly fall into above-mentioned first charging capacitor；Switch 616 and switch 619 broadly fall into above-mentioned first discharge switch。Described switch 614,616,617,619 all can select metal-oxide-semiconductor, it is possible to is NMOS tube or PMOS。Switch shown in the present embodiment Fig. 4 can select metal-oxide-semiconductor, it is possible to is NMOS tube or PMOS。Protection scope of the present invention is not limited to a kind of implementation of the sawtooth waveforms generation module 611 shown in Fig. 5, and the sawtooth waveforms generation module of every principle structure utilizing charging capacitor and charge and discharge switch all includes in protection scope of the present invention。

Described degaussing time detecting module 601 produces to represent the signal (i.e. degaussing time signal) 202 of Tmag time after the feedback signal 502 in Fig. 4 is processed。When described degaussing time signal 202 controls switch 603 Guan Bi, current source 602 gives electric capacity 604 (i.e. the second charging capacitor) charging。Electric capacity 604 delivers a voltage on amplifier 606 after each turn-on cycle of switch 603 terminates, and is then transferred to again through amplifier 606 on the input of described three input comparators 612。What the voltage signal 503 on electric capacity 604 represented is exactly degaussing temporal information (i.e. Tmag information)。

$\mathrm{Vmag}=\frac{\mathrm{Imag}\×\mathrm{Tmag}}{C3}---\left(9\right)$

Wherein, Vmag represents the degaussing time Tmag corresponding voltage signal 503 changed into, i.e. degaussing time voltage signal 503；C3 represents the capacitance of capacitor 604；Imag represents the current value (i.e. the second charging current) that current source 602 produces。

The computing formula of the system output voltage 210 shown in Fig. 4 is:

$\mathrm{Vout}=\mathrm{Ls}\×\frac{\mathrm{Isk}}{\mathrm{Tmag}}---\left(10\right)$

Wherein, Ls is the inductance value of the inductance 406 of secondary windings, and Isk is the peak value of secondary current 514, and Vout is output voltage 210, Tmag is the degaussing time。When CC work, the value of the voltage Vout that the value of voltage Vout is corresponding when working than CV is little, and Isk is bigger than when working at CV when CC works simultaneously。From Output Voltage Formula (10), when CV works, system output voltage 210 both is greater than the value when CC works, if the magnitude of voltage of signal 503 time Vmag_cc is CC work, time Vmag_cv is CV work, the magnitude of voltage of signal 503, is had by formula (10)

Vmag_cc>Vmag_cv(11)

Make simultaneously need to set a voltage separation Vrefth (namely presetting constant pressure and flow demarcation voltage),

Vmag_cc>Vrefth>Vmag_cv(12)

Shown in Fig. 7, within the T1 time period, the system shown in Fig. 4 is operated in CC state, owing to voltage signal 506 is much smaller than reference voltage VREF1, therefore signal 507 is a clamp value Vclamp, now voltage-controlled current source 610 be subject to signal 507 control output electric current be fixed as maximum Imax。Again by formula (12) it can be seen that voltage signal 503 is more than Vrefth, comparator 612 comparison signal 503 and sawtooth signal 510 when CC works, produce signal 508。MOS switch 614 and 619 Guan Bi when 508 is high time, current source 610 charges to capacitor 615, and capacitor 618 discharges over the ground；Otherwise switching 618 and 617 Guan Bis when signal 508 is low time, current source 610 charges to capacitor 618, and capacitor 615 discharges over the ground, produces sawtooth signal 510。Assume capacitance respectively C1 and the C2 of electric capacity 615 and 618, then have:

$\mathrm{Tcc}=(C1+C2)\×\frac{\mathrm{Vmag}\_\mathrm{cc}}{I\max }---\left(13\right)$

$\mathrm{Duty}\_\mathrm{off}=\frac{\mathrm{Tmag}}{\mathrm{Tcc}}---\left(14\right)$

By formula (9), (13), and (14) can know by inference:

$\mathrm{Duty}\_\mathrm{off}=\frac{C3}{(C1+C2)}\×\frac{I\max }{\mathrm{Imag}}---\left(15\right)$

Due to the ratio of C3 and C1 Yu C2 sum, and the ratio of Imax and Imag is all readily implemented as a fixed value, therefore can be fairly simple realize CC function。

Within T2 and the T3 time period, system shown in Fig. 4 is operated in CV state, signal 506 is close to even above reference voltage VREF1, and the output signal 507 no longer clamper of frequency adjuster 418 is at Vclamp, and the electric current 509 that voltage-controlled current source 610 produces also begins to depart from Imax and becomes less。Simultaneously by formula (12) it can be seen that comparator 612 select be sawtooth signal and Vrefth compares, the frequency of output switching activity signal 508 is now completely relevant with the electric current 509 of voltage-controlled current source 610 generation。

Within the T2 time period, system output voltage shown in Fig. 4 210 adjusts voltage setting value higher than CV, and (this setting value is the output voltage adjusted value of whole CV default, such as this constant-voltage system needs output 5V, so this 5V is exactly setting value), then signal 506 is relatively high, relatively low magnitude of voltage 507 is obtained by frequency adjuster (also known as PFM controller) 418, and then obtain voltage-controlled current source 610 and export less electric current 509, the rate of rise producing sawtooth signal 510 is also just relatively low, thus, the CV start signal 508 that agitator 416 output frequency is relatively low。Relatively low magnitude of voltage 506 also results in the comparator 421 shown in Fig. 4 in less peak current value Ipk place upset, and the current peak of this meaning main coil is less。By formula (8) it can be seen that less switching tube turn-on frequency fsw and Ipk means less system output voltage Vout, until system output voltage Vout returns to CV and adjusts voltage setting value, it is achieved in CV function。

Otherwise, within the T3 time period, when system output voltage shown in Fig. 4 adjusts voltage setting value lower than CV, signal 506 is relatively high, obtaining the high magnitude of voltage of comparison 507 by frequency adjuster 418, and then obtain voltage-controlled current source 610 and export bigger electric current 509, the rate of rise producing sawtooth signal 510 is also just relatively high, thus, the higher CV start signal 508 of frequency of agitator 416 output。Higher magnitude of voltage 507 also results in the comparator 421 shown in Fig. 4 and overturns at bigger Ipk place, and the Ipk of this meaning main coil is bigger。By formula (8) it can be seen that higher switching tube turn-on frequency fsw and Ipk means higher Vout, until system output voltage Vout returns to CV and adjusts voltage setting value。

When CV adjusts, it is also possible to keep Ipk constant, namely at T2, in the T3 time period, system shown in Fig. 4 is operated in CV state, signal 506 is close to even above VREF1, and the output signal 507 no longer clamper of frequency adjuster 418 is at Vclamp, and the electric current 509 that voltage-controlled current source 610 produces also begins to depart from Imax and becomes less。Simultaneously by formula (12) it can be seen that comparator 612 select be sawtooth signal and Vrefth compares, the frequency of output switching activity signal 508 is now completely relevant with the electric current 509 of voltage-controlled current source 610 generation。Specifically, within the T2 time period, system output voltage 210 shown in Fig. 4 adjusts voltage setting value higher than CV, then signal 506 is relatively low, obtains relatively low magnitude of voltage 507 by frequency adjuster (also known as PFM controller) 418, and then obtains voltage-controlled current source 610 and export less electric current 509, the rate of rise producing sawtooth signal 510 is also just relatively low, thus, the CV start signal 508 that agitator 416 output frequency is relatively low, now Ipk is constant。By formula (8) it can be seen that less fsw means less Vout, until system output voltage Vout returns to CV and adjusts voltage setting value, it is achieved in CV function。

Otherwise, within the T3 time period, when system output voltage shown in Fig. 4 adjusts voltage setting value lower than CV, signal 506 is relatively higher, obtains the high magnitude of voltage of comparison 507 by frequency adjuster 418, and then obtains voltage-controlled current source 610 and export bigger electric current 509, the rate of rise producing sawtooth signal 510 is also just relatively high, thus, the CV start signal 508 of the higher fsw of frequency of agitator 416 output, now Ipk is constant。By formula (8) it can be seen that higher fsw means higher Vout, until system output voltage Vout returns to CV and adjusts voltage setting value。

In sum, no matter it is in CC duty or CV duty, agitator 416 is all only export a unique road to control the signal 508 of switching tube 426 conducting shown in Fig. 4, it is not necessary to judge and process CC start signal or the CV start signal of complexity, it is to avoid sequential competition risk；And high frequency OSC (abbreviation of oscillator, agitator) sawtooth waveforms need not be produced, it is to avoid potential ghost effect。

The present embodiment also provides for a kind of constant current constant voltage control method for primary side feedback, the method can realize by the constant-current and constant-voltage control circuit for primary side feedback described in the present embodiment, but the structure realizing the constant-current and constant-voltage control circuit for primary side feedback that device includes but not limited to that the present embodiment enumerates of the method。

As shown in Figure 8, the described constant current constant voltage control method for primary side feedback includes:

S801, detects the degaussing time, and the degaussing time changes into degaussing time voltage signal。

Further, as it is shown in figure 9, the described detection degaussing time, and the one that the degaussing time changes into degaussing time voltage signal realizes process and includes:

S901, utilizes the degaussing time detecting module detection degaussing time, exports degaussing time signal；

S902, utilizes current source to export the second charging current；

S903, utilizes the second charge switch to control described second charging current under the control of described degaussing time signal and one second charging capacitor is charged；

S904, utilizes described second charging capacitor to export described degaussing time voltage signal。

A kind of specific implementation of step S801 can be shown in Figure 5 circuit; but the protection domain of this step S801 is not limited to the circuit shown in Fig. 5 that the present embodiment is enumerated, the step S801 that the operation principle described in every Fig. 5 and Fig. 9 of utilization realizes includes in protection scope of the present invention。

S802, generates a constant voltage clock frequency control signal。

Further, as it can be seen in figures 5 and 6, the one of described generation constant voltage clock frequency control signal realizes process and includes: utilize comparator to compare the size of coherent signal 506 and reference signal, generate described constant voltage clock frequency control signal；Or the size of the more described coherent signal 506 of comparator utilizing at least two in parallel and at least two reference signal, generate described constant voltage clock frequency control signal。

S803, sawtooth signal is generated under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal generates constant current clock start signal, or the size comparing described sawtooth signal and default constant pressure and flow demarcation voltage generates constant voltage clock start signal。

Further, as shown in Figure 10, the described one generating sawtooth signal under the control of described constant voltage clock frequency control signal realizes process and includes:

S101, utilizes voltage-controlled current source to export the first charging current under the control of described constant voltage clock frequency control signal；

S102, utilizes the first charging capacitor to produce sawtooth signal under the charging of described first charging current；Or

S103, utilizes the first charge switch of the first charging capacitor described in described constant current clock start signal or constant voltage clock start signal feedback control and the on or off of the first discharge switch, adjusts the rate of rise of described sawtooth signal or/and amplitude。

A kind of specific implementation of step S803 can be shown in Figure 5 circuit; but the protection domain of this step S803 is not limited to the circuit shown in Fig. 5 that the present embodiment is enumerated, the step S803 that the operation principle described in every Fig. 5 and Figure 10 of utilization realizes includes in protection scope of the present invention。

Present invention employs a kind of method of novelty and produce CC/CV unlatching clock signal, it is possible to share same unlatching clock generator, effectively prevent the issuable sequential competition problem of two paths of signals；And eliminate the sawtooth wave generating circuit 104 (it includes HF signal generator 303 and sawtooth generator 305) in Fig. 1, provide cost savings；Need not the generation of high-frequency signal, it is to avoid the risk of ghost effect。

In sum, the present invention effectively overcomes various shortcoming of the prior art and has high industrial utilization。

Above-described embodiment is illustrative principles of the invention and effect thereof only, not for the restriction present invention。Above-described embodiment all under the spirit and category of the present invention, can be modified or change by any those skilled in the art。Therefore, art has usually intellectual such as modifying without departing from all equivalences completed under disclosed spirit and technological thought or change, must be contained by the claim of the present invention。

Claims (8)

1. the constant-current and constant-voltage control circuit for primary side feedback, it is characterised in that the described constant-current and constant-voltage control circuit for primary side feedback includes:

Degaussing time converter, is used for detecting the degaussing time, and the degaussing time changes into degaussing time voltage signal；

Frequency adjuster, is used for producing constant voltage clock frequency control signal；

Agitator, it is respectively connected with described degaussing time converter and frequency adjuster, sawtooth signal is produced under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal produces constant current clock start signal, or the size comparing described sawtooth signal and default constant pressure and flow demarcation voltage produces constant voltage clock start signal。

2. the constant-current and constant-voltage control circuit for primary side feedback according to claim 1, it is characterised in that described agitator includes:

Voltage-controlled current source, is connected with described frequency adjuster, exports the first charging current under the control of described constant voltage clock frequency control signal；

Sawtooth waveforms generation module, is connected with described voltage-controlled current source, including the first charging capacitor, the first charge switch and the first discharge switch；Described first charging capacitor produces sawtooth signal under the charging of described first charging current；

Three input comparators, it is respectively connected with described sawtooth waveforms generation module and degaussing time converter, numerical value the greater or smaller and described sawtooth signal in described degaussing time voltage signal and described default demarcation voltage are compared, output constant current clock start signal or constant voltage clock start signal；The conducting of the first charge switch and the first discharge switch described in described constant current clock start signal or constant voltage clock start signal feedback control turns off, and adjusts the rate of rise of described sawtooth signal or/and amplitude。

3. the constant-current and constant-voltage control circuit for primary side feedback according to claim 1, it is characterised in that described degaussing time converter includes:

Degaussing time detecting module, detects the degaussing time, exports degaussing time signal；

Current source, exports the second charging current；

Second charge switch, is respectively connected with described degaussing time detecting module and current source, controls described second charging current the second charging capacitor is charged under the control of described degaussing time signal；

Second charging capacitor, closes pipe with described second charging and is connected, export described degaussing time voltage signal。

4. the constant-current and constant-voltage control circuit for primary side feedback according to claim 1, it is characterised in that: described frequency adjuster is a comparator or the comparator of at least two parallel connection。

5. the constant current constant voltage control method for primary side feedback, it is characterised in that the described constant current constant voltage control method for primary side feedback includes:

The detection degaussing time, and the degaussing time is changed into degaussing time voltage signal；

Generate constant voltage clock frequency control signal；

Sawtooth signal is generated under the control of described constant voltage clock frequency control signal, and the size comparing described sawtooth signal and described degaussing time voltage signal generates constant current clock start signal, or the size comparing described sawtooth signal and default constant pressure and flow demarcation voltage generates constant voltage clock start signal。

6. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that the described one generating sawtooth signal under the control of described constant voltage clock frequency control signal realizes process and includes:

Voltage-controlled current source is utilized to export the first charging current under the control of described constant voltage clock frequency control signal；

The first charging capacitor is utilized to produce sawtooth signal under the charging of described first charging current；Or

Utilize the first charge switch of the first charging capacitor described in described constant current clock start signal or constant voltage clock start signal feedback control and the on or off of the first discharge switch, adjust the rate of rise of described sawtooth signal or/and amplitude。

7. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that described detection degaussing time, and the one that the degaussing time changes into degaussing time voltage signal realizes process and includes:

Utilize the degaussing time detecting module detection degaussing time, export degaussing time signal；

Current source is utilized to export the second charging current；

Utilize the second charge switch to control described second charging current under the control of described degaussing time signal the second charging capacitor is charged；

Described second charging capacitor is utilized to export described degaussing time voltage signal。

8. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that the one of described generation constant voltage clock frequency control signal realizes process and includes:

Utilize comparator to compare the size of coherent signal and reference signal, generate described constant voltage clock frequency control signal；Or

Utilize the more described coherent signal of comparator and the size of at least two reference signal of at least two parallel connection, generate described constant voltage clock frequency control signal。