CN105700602B - A constant current and constant voltage control method and circuit for primary side feedback - Google Patents
A constant current and constant voltage control method and circuit for primary side feedback Download PDFInfo
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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
Technical field
The invention belongs to electronic circuit technology field, it is related to a kind of constant current constant voltage control method and system, more particularly to
A kind of constant current constant voltage control method and circuit for primary side feedback.
Background technology
In the circuit implementations of existing primary side feedback control chip, because constant current or constant pressure control system are relative
More complicated, constant-current circuit and the usual way of constant voltage circuit are processed respectively using two-way different circuit.
Shown in Figure 1, primary side feedback constant-current constant-voltage controller 100 includes：Degaussing time (Tdis) detector 101, uses
In the detection degaussing time, the signal of judgement CC/CV (constant current/constant voltage) is produced；Oscillator 102, for producing clock open signal；
Line compensation generator 103, for producing line compensation rate；CV control modules 104, for producing CV to control open frequency control letter
Number；FB sampling holders 105, for FB signals of sampling, sampling produces signal 203；Operational amplifier 106, for amplifying benchmark
The difference of voltage VREF and signal 203, the voltage signal 204 that output is inversely proportional with voltage signal 203, voltage signal 204 also and
System output voltage 210 is inversely proportional；Line current comparator 107, for on-off switching tube 117 when judging that line current reaches peak value；
Trigger 108, turns on for controlling switch pipe 117 and turns off；Driver 109, for digital logic signal to be changed into driving letter
Number driving switch pipe 117；Lead-edge-blanking module 110, for peak value sampling signal 209 to be processed after produce voltage signal
215；PWM/PFM controllers 111, clock selecting is opened for switching CC/CV；Sampling resistor 112, for sampled peak sampling
Signal 209；Resitstance voltage divider 113 and 114, the feedback signal 211 for producing output end, i.e. voltage division signal 211；Resistor
115, capacitor 116, and load 122, the supply voltage 123 for providing chip 100；Transformer Winding 121, for main line
To secondary, by primary side winding 124, secondary windings 119, assists winding 120 is constituted the energy transmission of circle；Electric current 222 is to flow through to be
The electric current of system load 122, voltage 210 is the voltage of system load 122.
Fig. 2 shows the degaussing time detector 101 in circuit shown in Fig. 1, oscillator 102, CV control modules 104, and
The specific implementation and correlation of PWM/PFM controllers 111.
Shown in Fig. 1 primary side feedback control (abbreviation primary-side-control) principle be：Main coil gives electric capacity 116 by resistance 115
Charge, control primary side feedback constant-current constant-voltage controller 100 to open after reaching the cut-in voltage of primary side feedback constant-current constant-voltage controller 100
Beginning work.When switching tube 117 is turned on, input energy is stored in main coil 124；When switching tube 117 is closed, transformer
121 can discharge energy, i.e., energy is discharged into output end (loading LOAD and output capacitance) by secondary coil 119, and
Information and output voltage 210 is mapped to voltage division signal 211 by assists winding 120 that is, relevant with output voltage 210 can be with
Extracted by assists winding 120, as shown in formula (1).
Wherein, 113,114 points of the resistor after output voltage 210 is changed into feedback signal by Transformer Winding 121
Pressure signal 211, is represented with VFB.Output voltage 210 represents with Vout,It is assists winding and secondary transformer turn ratio, R2
With the resistance that R1 is respectively resistor 114 and 113.By formula (1) as can be seen that VFB and Vout is linear, can pass through
The method of constant VFB voltages carrys out constant output voltage Vout, and the purpose of constant pressure is reached with this.
Inverse-excitation type (flyback) structure of primary-side-control typically uses DCM patterns (discontinuous mode), its CC
(constant current) work can be expressed as：
Wherein, Iout represents current signal 222, to flow through the electric current of load 122.What CC to be realized is just to maintain entirely mistake
Iout is constant in journey.Isk represents the peak current value that load LOAD is flowed through in a switch periods, there is relationship below：
Vcs=Ipk × Rcs (5)
Wherein, secondary discharge time after Tmeg representation switch pipe 117 is turned off, a switch week of T representation switch pipe 117
Phase, Rcs represents the resistance of sampling resistor 112,Secondary and primary transformers turn ratio is represented, Ipk represents a switch periods
Inside flow through the peak current value of resistance 112；From formula (2) and (3), holding Isk and Duty_off is constant just to be kept
Iout is constant so as to realize constant current.
When CC works, because sampled signal 203 is far below reference voltage (VREF) 207, therefore operational amplifier
106 output signal 204 can be clamped at a fixed higher limit Vthh.When switching tube 117 is turned on, on main coil
Electric current produces peak value sampling signal 209 on resistance 112；Peak value sampling signal 209 after lead-edge-blanking module 110 by comparing
Compare with the output signal 204 of operational amplifier 106 at device 107, the upset of signal 219 of the output of comparator 107 is height, Jin Ertong
Trigger 108 and the on-off switching tube 117 of 109 output drive signal of driver 214 are crossed, the peak point current of actual Ipk can be just controlled.
If the peak point current of each Ipk can be kept constant,It is primary and secondary transformer turn ratio, is fixed value for system,
From formula (4), Isk just can be constant.
Additionally, realizing that CC work also needs to keep constant Duty_off.As shown in figure 3, including Tmag in a cycle T
The degaussing time is represented, Ton represents switching tube ON time, and Tdis is represented when removed in cycle T that degaussing time and switching tube are turned on
Between outer remaining time, referring to formula (6).
T=Tmag+Ton+Tdis (6)
If set in each cycle T：
Tmag=Ton+Tdis (7)
Then,As constant, has reached the purpose of constant Duty_off, so as to realize CC functions.
As shown in figure 1, for CV (constant pressure) process, when output voltage 210 is lower than preset value, voltage division signal 211
It is that 210 feedback signal also can be relatively low, and then the signal 203 and signal (VREF) for obtaining of being sampled by FB sampling holders 105
207 error is amplified, and signal 204 is uprised, and now signal 204 can obtain a frequency arteries and veins higher by CV control modules 104
Signal 205 is rushed, from output energy theorem (6), output voltage 210 can return to normal value.When output voltage 210 is than pre-
It is similarly as the same if be worth high.System output voltage has relationship below：
Wherein, fsw represents the turn-on frequency of switching tube, and Lp represents the inductance value of main coil 124.
Visible with reference to Fig. 2, the turn-on instant signal 206 of CC is relatively determined by signal 310 and VREF voltage ratios；During the conducting of CV
Signal 212 is carved to be compared by a sawtooth waveforms 311 and a fixed voltage signal 204, therefore, the turn-on instant of main switch 117
Determined by the logic judgment of PWM/PFM controllers 111 by 206 and 212, because CC and CV two systems produce each independent arteries and veins
Punching, so in the presence of certain sequential competition risk.Additionally, sawtooth waveforms was generally needed with hundreds of the K even week of several million frequencies
Phase property pulses generation, 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, due to constant current or constant pressure control
Mode processed is relatively complicated, and constant-current circuit and the usual way of constant voltage circuit are processed respectively using two-way different circuit,
Not only circuit is complicated but also cost is bigger, easily causes ghost effect, and interference of the ghost effect to exquisite system is often fatal
, and due to complex time at treatment constant current constant voltage turning point, design is improper to be easy to misoperation occur or even exports energy
Measure the situation of concussion.Therefore, how constant current constant voltage control is effectively realized with fairly simple mode, is transitioned into naturally from constant current state
Pressure constant state is current urgent problem.
The content 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 for primary side feedback
Constant pressure control method and circuit, it is independent using two kinds for solving constant current and Isobarically Control in existing primary side feedback control technology
Mode realizes there is sequential competitive risk and ghost effect respectively, causes the problems such as realizing circuit complexity, high cost.To realize
Above-mentioned purpose and other related purposes, the present invention provide a kind of constant-current and constant-voltage control circuit for primary side feedback, described to be used for
The constant-current and constant-voltage control circuit of primary side feedback includes：Degaussing time converter, for detecting the degaussing time, and the degaussing time is turned
Chemical conversion degaussing time voltage signal；Frequency adjuster, for producing constant pressure clock frequency control signal；Oscillator, goes with described
Magnetic time converter and frequency adjuster are respectively connected with, and sawtooth waveforms is produced under the control of the constant pressure clock frequency control signal
Signal, and relatively the size of the sawtooth signal and the degaussing time voltage signal produces constant current clock open signal, or
The size for comparing the sawtooth signal and default constant pressure and flow demarcation voltage produces constant pressure clock open signal.
Alternatively, the oscillator includes：Voltage-controlled current source, is connected with the frequency adjuster, in the constant pressure clock
The first charging current is exported under the control of frequency control signal；Sawtooth waveforms generation module, is connected with the voltage-controlled current source, including
First charging capacitor, the first charge switch and the first discharge switch；First charging capacitor is in first charging current
Charge lower generation sawtooth signal；Three input comparators, with the sawtooth waveforms generation module and degaussing time converter difference phase
Even, numerical value the greater or smaller in the degaussing time voltage signal and the default demarcation voltage are believed with the sawtooth waveforms
Number it is compared, output constant current clock open signal or constant pressure clock open signal；The constant current clock open signal or constant pressure
The conducting shut-off of the first charge switch and the first discharge switch described in clock open signal feedback control, adjusts the sawtooth waveforms letter
Number the rate of rise or/and amplitude.
Alternatively, the 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, with the degaussing time detecting module and current source
It is respectively connected with, controls second charging current to charge the second charging capacitor under the control of the degaussing time signal；The
Two charging capacitors, are connected with second charge switch, export the degaussing time voltage signal.
Alternatively, the frequency adjuster is the comparator of a comparator or at least two parallel connections.
The present invention also provides a kind of constant current constant voltage control method for primary side feedback, the constant current for primary side feedback
Constant pressure control method includes：The detection degaussing time, and the degaussing time is changed into degaussing time voltage signal；Generation constant pressure clock
Frequency control signal；Sawtooth signal, and relatively more described sawtooth are generated under the control of the constant pressure clock frequency control signal
The size generation constant current clock open signal of ripple signal and the degaussing time voltage signal, or relatively the sawtooth signal and
The size generation constant pressure clock open signal of default constant pressure and flow demarcation voltage.
Alternatively, a kind of realization that sawtooth signal is generated under the control of the constant pressure clock frequency control signal
Process includes：Using voltage-controlled current source the first charging current is exported under the control of the constant pressure clock frequency control signal；Profit
With the first charging capacitor sawtooth signal is produced under the charging of first charging current；Opened using the constant current clock and believed
Number or the first charge switch of the first charging capacitor and leading for the first discharge switch described in constant pressure clock open signal feedback control
Logical or shut-off, adjusts the rate of rise or/and amplitude of the sawtooth signal.
Alternatively, the detection degaussing time, and the degaussing time is changed into a kind of realization of degaussing time voltage signal
Process includes：The degaussing time is detected using degaussing time detecting module, degaussing time signal is exported；Second is exported using current source
Charging current；Second charging current is controlled under the control of the degaussing time signal to second using the second charge switch
Charging capacitor charges；The degaussing time voltage signal is exported using second charging capacitor.
Alternatively, a kind of implementation process of the generation constant pressure clock frequency control signal includes：Compared using comparator
Coherent signal and the size of reference signal, generate the constant pressure clock frequency control signal；Or using the ratio of at least two parallel connections
Compared with the device coherent signal and the size of at least two reference signals, the constant pressure clock frequency control signal is generated.
As described above, the constant current constant voltage control method and circuit for primary side feedback of the present invention, has with following
Beneficial effect：
CC/CV is produced to open clock signal present invention employs a kind of novel method, when can share same unlatching
Clock generator, effectively prevent the issuable sequential competition problem of two paths of signals；And ramp generating circuit is eliminated, is saved
Cost；The generation of high-frequency signal is not needed, it is to avoid the risk of ghost effect.
Brief description of the drawings
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 that a kind of application scenarios of the constant-current and constant-voltage control circuit for primary side feedback described in the embodiment of the present invention show
It is intended to.
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 another 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 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
Time diagram.
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.
Fig. 9 is that one kind of the step S801 described in the embodiment of the present invention implements schematic flow sheet.
Figure 10 is that one kind of the partial content of the step S803 described in the embodiment of the present invention implements schematic flow sheet.
Component label instructions
400 constant-current and constant-voltage control circuits for 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 oscillators
610 voltage-controlled current sources
611 sawtooth waveforms generation modules
612 3 input comparators
418 frequency adjusters
S801~S803 steps
S901~S904 steps
S101~S103 steps
Specific embodiment
Embodiments of the present invention are illustrated below by way of specific instantiation, those skilled in the art can be by this specification
Disclosed content understands other advantages of the invention and effect easily.The present invention can also be by specific realities different in addition
The mode of applying is embodied or practiced, the various details in this specification can also based on different viewpoints with application, without departing from
Various modifications or alterations are carried out under spirit of the invention.
Refer to accompanying drawing.It should be noted that the diagram provided in the present embodiment only illustrates the present invention in a schematic way
Basic conception, component count, shape when only display is with relevant component in the present invention rather than according to actual implementation in schema then
Shape and size are drawn, and it is actual when the implementing kenel of each component, quantity and ratio can be a kind of random change, and its component cloth
Office's kenel is likely to increasingly complex.
Existing primary side feedback constant-current and constant-voltage control circuit shown in Fig. 1 not only complex structure, and cost is big, easily causes
Ghost effect, due to complex time especially when processing at constant current constant voltage turning point, design is improper to be easy to occur misoperation very
To the situation of output energy concussion, therefore, how constant current constant voltage control is effectively realized with fairly simple mode, from constant current state certainly
It is problem to be solved by this invention to be so transitioned into pressure constant state.
With reference to 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, and its application scenarios is as shown in figure 4, institute
The constant-current and constant-voltage control circuit 400 stated for primary side feedback includes：Degaussing time converter (Tdis detections) 415, frequency adjustment
Device (PFM) 418, oscillator (OSC) 416.
Shown degaussing time converter 415 is used to detect the degaussing time, and the degaussing time is changed into degaussing time voltage
Signal.Further, as shown in figure 5, the degaussing time converter 415 includes：Degaussing time detecting module 601, current source
602, the second charge switch 603, the second charging capacitor 604.The degaussing time detecting module 601 detects degaussing time, output
Degaussing time signal 202.The current source 602 exports the second charging current.When second charge switch 603 is with the degaussing
Between detection module 601 and current source 602 be respectively connected with, control described second to charge electricity under the control of the degaussing time signal
Stream charges to one second charging capacitor.Second charging capacitor 604 is connected with second charge switch 603, and output is described
Degaussing time voltage signal.
The frequency adjuster 418 is used to produce constant pressure clock frequency control signal.Further, as shown in figure 5, the frequency
Rate adjuster 418 can be a comparator.Or as shown in fig. 6, the frequency adjuster 418 can be at least two parallel connections
Comparator.
The oscillator 416 is respectively connected with the degaussing time converter 415 and frequency adjuster 416, in the perseverance
Sawtooth signal, and the relatively sawtooth signal and degaussing time electricity are produced under the control for pressing clock frequency control signal
The size of signal is pressed to produce constant current clock open signal, or relatively more described sawtooth signal and a default constant pressure and flow demarcation voltage
Size produce constant pressure clock open signal.Further, as shown in figure 5, the oscillator 416 includes：Voltage-controlled current source 610,
Sawtooth waveforms generation module 611, three input comparators 612.The voltage-controlled current source 610 is connected with the frequency adjuster 418,
The first charging current 509 is exported under the control of the constant pressure clock frequency control signal.The sawtooth waveforms generation module 611 and institute
Voltage-controlled current source 610 is stated to be connected, including the first charging capacitor, the first charge switch and the first discharge switch；Described first charges
Electric capacity produces sawtooth signal 510 under the charging of first charging current.Three input comparator 612 and the sawtooth
Ripple generation module 611 and degaussing time converter 415 are respectively connected with, by the degaussing time voltage signal and the default boundary
Numerical value the greater or smaller are compared with the sawtooth signal in voltage, when output constant current clock open signal or constant pressure
Clock open signal 508.First charging described in the constant current clock open signal or the feedback control of constant pressure clock open signal 508 is opened
Close and the conducting of the first discharge switch is turned off, adjust the rate of rise or/and amplitude of the sawtooth signal.
The course of work of the constant-current and constant-voltage control circuit for primary side feedback described in the present embodiment is：
The frequency adjuster 418 is compared when producing constant pressure after processing to voltage signal 506 and reference voltage V REF1
Clock frequency control signal (i.e. PFM control signals) 507.
The control voltage-controlled current source 610 of constant pressure clock frequency control signal 507 produces electric current 509.The electricity when switching 614 and closing
Stream 509 charges to electric capacity 615, or electric current 509 charges to electric capacity 618 when switching 617 and closing；And when 616 closure is switched,
Electric capacity 615 discharges over the ground；When 619 closure is switched, electric capacity 618 discharges over the ground.Switch 614 and switch 617 belong to above-mentioned the
One charge switch；Electric capacity 615 and electric capacity 618 belong to above-mentioned first charging capacitor；Switch 616 and switch 619 belong to above-mentioned
First discharge switch.The switch 614,616,617,619 can select metal-oxide-semiconductor, can be NMOS tube or PMOS.This
Switch shown in embodiment Fig. 4 can select metal-oxide-semiconductor, can be NMOS tube or PMOS.Protection scope of the present invention is not
It is limited to a kind of implementation of the sawtooth waveforms generation module 611 shown in Fig. 5, what every utilization charging capacitor and charge and discharge were switched
The sawtooth waveforms generation module of principle construction is included in protection scope of the present invention.
The degaussing time detecting module 601 produces the letter for representing the Tmag times after processing the feedback signal 502 in Fig. 4
Number (i.e. degaussing time signal) 202.When 202 controlling switch of degaussing time signal 603 is closed, current source 602 gives electric capacity 604
(i.e. the second charging capacitor) charges.Electric capacity 604 delivers a voltage to amplifier after each turn-on cycle of switch 603 terminates
On 606, then it is transferred on the input of three input comparator 612 by amplifier 606 again.Voltage on electric capacity 604
What signal 503 was represented is exactly degaussing temporal information (i.e. Tmag information).
Wherein, Vmag represents the corresponding voltage signal 503 that degaussing time Tmag is 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 is produced.
The computing formula of the system output voltage 210 shown in Fig. 4 is：
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.The value of corresponding voltage Vout will when the value of voltage Vout works than CV when CC works
It is small, while Isk is big when CV works in work when ratios of CC.From Output Voltage Formula (10), when CV works,
System output voltage 210 is both greater than the value when CC works, if Vmag_cc is the magnitude of voltage of signal 503 when CC works,
Vmag_cv is the magnitude of voltage of signal 503 when CV works, and is had by formula (10)
Vmag_cc ＞ Vmag_cv (11)
One voltage separation Vrefth of setting (presetting constant pressure and flow demarcation voltage) is needed to cause simultaneously,
Vmag_cc ＞ Vrefth ＞ Vmag_cv (12)
With reference to shown in Fig. 7, within the T1 time periods, the system shown in Fig. 4 is operated in CC states, because voltage signal 506 is remote
Less than reference voltage VREF1, therefore signal 507 is a clamp value Vclamp, and now voltage-controlled current source 610 is subject to signal 507
Controlled output electric current is fixed as maximum Imax.Again from formula (12), voltage signal 503 is more than Vrefth when CC works, than
Compared with the comparison signal 503 of device 612 and sawtooth signal 510, signal 508 is produced.The MOS switch 614 and 619 when 508 is high
Closure, current source 610 charges to capacitor 615, and capacitor 618 discharges over the ground；Otherwise switched when signal 508 is low
618 and 617 closures, current source 610 charges to capacitor 618, and capacitor 615 discharges over the ground, produces sawtooth signal 510.It is false
If the capacitance of electric capacity 615 and 618 is respectively C1 and C2, then have：
By formula (9), (13), and (14) can deduce：
Because C3 and C1 and the ratio of C2 sums, and the ratio of Imax and Imag are all readily implemented as a fixation
Value, therefore CC functions can be realized with fairly simple.
Within T2 the and T3 time periods, the system shown in Fig. 4 is operated in CV states, and signal 506 is close to even above with reference to electricity
Pressure VREF1, the no longer clamper of output signal 507 of frequency adjuster 418 is in Vclamp, the electric current 509 of the generation of voltage-controlled current source 610
Also beginning to disengaging Imax becomes smaller.Simultaneously from formula (12), the selection of comparator 612 is sawtooth signal and Vrefth ratios
Compared with the frequency of output switching activity signal 508 is now completely relevant with the electric current 509 that voltage-controlled current source 610 is produced.
Within the T2 time periods, (setting value is higher than CV adjustment voltage setting value for system output voltage 210 shown in Fig. 4
It is the output voltage adjusted value of whole CV defaults, such as this constant-voltage system needs to export 5V, then this 5V is exactly to set
Definite value), then signal 506 compares high, is obtained than relatively low magnitude of voltage 507 by frequency adjuster (also known as PFM controllers) 418,
And then obtain voltage-controlled current source 610 and export less electric current 509, produce the rate of rise of sawtooth signal 510 also just than relatively low,
Thus, the relatively low CV open signals 508 of the output frequency of oscillator 416.Relatively low magnitude of voltage 506 also results in the ratio shown in Fig. 4
Overturn at smaller peak current value Ipk compared with device 421, the current peak of this meaning main coil is smaller.From formula (8), more
Low switching tube turn-on frequency fsw and Ipk means lower system output voltage Vout, until system output voltage Vout is returned
Voltage setting value is adjusted to CV, CV functions are achieved in.
Conversely, within the T3 time periods, when the system output voltage shown in Fig. 4 adjusts voltage setting value less than CV, signal 506
Compare high, obtain comparing magnitude of voltage 507 high by frequency adjuster 418, and then obtain voltage-controlled current source 610 exporting larger
Electric current 509, produces the rate of rise of sawtooth signal 510 also just relatively higher, thus, the frequency of the output of oscillator 416 is higher
CV open signals 508.The comparator 421 that magnitude of voltage 507 higher also results in shown in Fig. 4 overturns at bigger Ipk, this meaning
The Ipk of main coil is bigger.From formula (8), switching tube turn-on frequency fsw and Ipk higher means Vout higher, until
System output voltage Vout returns to CV adjustment voltage setting values.
When CV is adjusted, it is also possible to keep Ipk constant, i.e., in T2, in the T3 time periods, the system work shown in Fig. 4
Make in CV states, signal 506 exists close to even above VREF1, the no longer clamper of output signal 507 of frequency adjuster 418
Vclamp, the electric current 509 that voltage-controlled current source 610 is produced also begins to disengaging Imax becomes smaller.Simultaneously from formula (12), compare
The selection of device 612 is that sawtooth signal and Vrefth compare, and the frequency of output switching activity signal 508 is now completely and voltage-controlled current source
610 electric currents 509 for producing are relevant.Specifically, within the T2 time periods, the system output voltage 210 shown in Fig. 4 adjusts electricity higher than CV
Setting value is pressed, then signal 506 is obtained than relatively low magnitude of voltage than relatively low by frequency adjuster (also known as PFM controllers) 418
507, and then obtain voltage-controlled current source 610 and export less electric current 509, produce the rate of rise of sawtooth signal 510 also just than
It is relatively low, thus, the relatively low CV open signals 508 of the output frequency of oscillator 416, now Ipk is constant.It is lower from formula (8)
Fsw means lower Vout, until system output voltage Vout returns to CV adjustment voltage setting values, is achieved in CV functions.
Conversely, within the T3 time periods, when the system output voltage shown in Fig. 4 adjusts voltage setting value less than CV, signal 506
Compare high, obtain comparing magnitude of voltage 507 high by frequency adjuster 418, and then obtain voltage-controlled current source 610 exporting larger
Electric current 509, produces the rate of rise of sawtooth signal 510 also just relatively higher, thus, the frequency fsw higher of the output of oscillator 416
CV open signals 508, now Ipk is constant.From formula (8), fsw higher means Vout higher, until system is defeated
Go out voltage Vout and return to CV adjustment voltage setting values.
In sum, either in CC working conditions or CV working conditions, oscillator 416 is all only to export uniquely all the way
The signal 508 of the conducting of switching tube 426 shown in control figure 4, it is not necessary to which the CC open signals or CV for judging and processing complexity are opened
Open signal, it is to avoid sequential competition risk；And do not need high frequency OSC (abbreviation of oscillator, oscillator) to produce sawtooth
Ripple, it is to avoid potential ghost effect.
The present embodiment also provides a kind of constant current constant voltage control method for primary side feedback, and the method can be by the present embodiment
The described constant-current and constant-voltage control circuit for primary side feedback realizes, but the method realizes device including but not limited to this implementation
The structure of the constant-current and constant-voltage control circuit for primary side feedback that example is enumerated.
As shown in figure 8, the constant current constant voltage control method for primary side feedback includes：
S801, detects the degaussing time, and the degaussing time is changed into degaussing time voltage signal.
Further, as shown in figure 9, described detect the degaussing time, and the degaussing time is changed into degaussing time voltage signal
A kind of implementation process include：
S901, the degaussing time is detected using degaussing time detecting module, exports degaussing time signal；
S902, the second charging current is exported using current source；
S903, second charging current pair is controlled using the second charge switch under the control of the degaussing time signal
One second charging capacitor charges；
S904, the degaussing time voltage signal is exported using second charging capacitor.
A kind of specific implementation of step S801 can be found in the circuit shown in Fig. 5, but this step S801 protection domain
The circuit shown in Fig. 5 that the present embodiment is enumerated is not limited to, the step of the operation principle described in every utilization Fig. 5 and Fig. 9 is realized
S801 is included in protection scope of the present invention.
S802, generates a constant pressure clock frequency control signal.
Further, as it can be seen in figures 5 and 6, a kind of implementation process of the generation constant pressure clock frequency control signal includes：Profit
Compare the size of coherent signal 506 and reference signal with comparator, generate the constant pressure clock frequency control signal；Or using extremely
The size of the comparator reference signal of coherent signal 506 and at least two of few two parallel connections, when generating the constant pressure
Clock frequency control signal.
S803, generates sawtooth signal, and relatively more described sawtooth under the control of the constant pressure clock frequency control signal
The size generation constant current clock open signal of ripple signal and the degaussing time voltage signal, or relatively the sawtooth signal and
The size generation constant pressure clock open signal of default constant pressure and flow demarcation voltage.
Further, as shown in Figure 10, it is described that sawtooth waveforms letter is generated under the control of the constant pressure clock frequency control signal
Number a kind of implementation process include：
S101, the first charging electricity is exported using voltage-controlled current source under the control of the constant pressure clock frequency control signal
Stream；
S102, sawtooth signal is produced using the first charging capacitor under the charging of first charging current；
S103, charges electric using described in the constant current clock open signal or constant pressure clock open signal feedback control first
The first charge switch and the on or off of the first discharge switch for holding, adjust the sawtooth signal the rate of rise or/and
Amplitude.
A kind of specific implementation of step S803 can be found in the circuit shown in Fig. 5, but this step S803 protection domain
The circuit shown in Fig. 5 that the present embodiment is enumerated is not limited to, the step of the operation principle described in every utilization Fig. 5 and Figure 10 is realized
S803 is included in protection scope of the present invention.
CC/CV is produced to open clock signal present invention employs a kind of novel method, when can share same unlatching
Clock generator, effectively prevent the issuable sequential competition problem of two paths of signals；And eliminate the generation of the sawtooth waveforms in Fig. 1
Circuit 104 (it includes HF signal generator 303 and sawtooth generator 305), saves cost；High-frequency signal is not needed
Produce, 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.
The above-described embodiments merely illustrate the principles and effects of the present invention, not for the limitation present invention.It is any ripe
The personage for knowing this technology all can carry out modifications and changes under without prejudice to spirit and scope of the invention to above-described embodiment.Cause
This, those of ordinary skill in the art is complete with institute under technological thought without departing from disclosed spirit such as
Into all equivalent modifications or change, should be covered by claim of the invention.
Claims (8)
1. a kind of constant-current and constant-voltage control circuit for primary side feedback, it is characterised in that the constant current for primary side feedback is permanent
Voltage-controlled circuit processed includes：
Degaussing time converter, for detecting the degaussing time, and changes into degaussing time voltage signal by the degaussing time；
Frequency adjuster, for producing constant pressure clock frequency control signal；
Oscillator, is respectively connected with the degaussing time converter and frequency adjuster, in constant pressure clock frequency control letter
Number control under produce sawtooth signal, and relatively the size of the sawtooth signal and the degaussing time voltage signal is produced
Constant current clock open signal, or relatively the size of the sawtooth signal and default constant pressure and flow demarcation voltage produces constant pressure clock
Open signal.
2. the constant-current and constant-voltage control circuit for primary side feedback according to claim 1, it is characterised in that the oscillator
Including：
Voltage-controlled current source, is connected with the frequency adjuster, and is exported under the control of the constant pressure clock frequency control signal
One charging current；
Sawtooth waveforms generation module, is connected with the voltage-controlled current source, including the first charging capacitor, the first charge switch and first are put
Electric switch；First charging capacitor produces sawtooth signal under the charging of first charging current；
Three input comparators, are respectively connected with the sawtooth waveforms generation module and degaussing time converter, by the degaussing time
Numerical value the greater or smaller are compared with the sawtooth signal in voltage signal and the default constant pressure and flow demarcation voltage
Compared with, output constant current clock open signal or constant pressure clock open signal；The constant current clock open signal or constant pressure clock are opened
The conducting shut-off of the first charge switch and the first discharge switch described in signal feedback control, adjusts the rising of the sawtooth signal
Slope 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 during the degaussing
Between converter include：
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 the degaussing time detecting module and current source, in the degaussing time signal
Control lower control second charging current charges to the second charging capacitor；
Second charging capacitor, is connected with second charge switch, exports the 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：The frequency is adjusted
Whole device is the comparator of a comparator or at least two parallel connections.
5. a kind of constant current constant voltage control method for primary side feedback, it is characterised in that the constant current for primary side feedback is permanent
Pressure control method includes：
The detection degaussing time, and the degaussing time is changed into degaussing time voltage signal；
Generation constant pressure clock frequency control signal；
Sawtooth signal, and relatively more described sawtooth signal and institute are generated under the control of the constant pressure clock frequency control signal
State the size generation constant current clock open signal of degaussing time voltage signal, or the relatively sawtooth signal and default constant pressure and constant
Flow the size generation constant pressure clock open signal of demarcation voltage.
6. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that described described
A kind of implementation process that sawtooth signal is generated under the control of constant pressure clock frequency control signal includes：
Using voltage-controlled current source the first charging current is exported under the control of the constant pressure clock frequency control signal；
Using the first charging capacitor sawtooth signal is produced under the charging of first charging current；
Using the constant current clock open signal or the first charging capacitor described in constant pressure clock open signal feedback control first
The on or off of charge switch and the first discharge switch, adjusts the rate of rise or/and amplitude of the sawtooth signal.
7. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that the detection is gone
The magnetic time, and a kind of implementation process that the degaussing time changes into degaussing time voltage signal is included：
The degaussing time is detected using degaussing time detecting module, degaussing time signal is exported；
The second charging current is exported using current source；
Second charging current is controlled to be charged to second under the control of the degaussing time signal using the second charge switch
Electric capacity charges；
The degaussing time voltage signal is exported using second charging capacitor.
8. the constant current constant voltage control method for primary side feedback according to claim 5, it is characterised in that the generation is permanent
Pressing a kind of implementation process of clock frequency control signal includes：
Compare the size of coherent signal and reference signal using comparator, generate the constant pressure clock frequency control signal；Or
Using the comparator of at least two parallel connections coherent signal and the size of at least two reference signals, generation is described
Constant pressure clock frequency control signal.
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| US8089783B2 (en) * | 2008-05-30 | 2012-01-03 | Active-Semi, Inc. | Constant current and voltage controller in a three-pin package with dual-use switch pin |
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| CN203466720U (en) * | 2013-09-02 | 2014-03-05 | 南京埃科孚电子科技有限公司 | Circuit reducing opening time in current control type switching regulating system |
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| CN102624237B (en) * | 2011-02-01 | 2015-09-16 | 昂宝电子（上海）有限公司 | For the system and method that the dynamic threshold of flyback power supply converter regulates |
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|---|---|---|---|---|
| US8089783B2 (en) * | 2008-05-30 | 2012-01-03 | Active-Semi, Inc. | Constant current and voltage controller in a three-pin package with dual-use switch pin |
| US8199537B2 (en) * | 2009-02-19 | 2012-06-12 | Iwatt Inc. | Detecting light load conditions and improving light load efficiency in a switching power converter |
| CN102651613A (en) * | 2011-02-28 | 2012-08-29 | 昂宝电子（上海）有限公司 | System and method used for constant-voltage mode and constant-current mode in flyback supply convertor |
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