CN106992684A - Flyback power supply system and its control method - Google Patents
Flyback power supply system and its control method Download PDFInfo
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- CN106992684A CN106992684A CN201710279652.7A CN201710279652A CN106992684A CN 106992684 A CN106992684 A CN 106992684A CN 201710279652 A CN201710279652 A CN 201710279652A CN 106992684 A CN106992684 A CN 106992684A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- Dc-Dc Converters (AREA)
Abstract
The invention provides a kind of flyback power supply system and its control method.The flyback power supply system, including transformer, the power switch that is connected with the primary side winding of transformer and be changed into cut-off state from conducting state for controlling power switch or be changed into the system control module of conducting state from cut-off state, wherein：System control module controls power switch to be changed into cut-off state from conducting state based on the current sample voltage being connected on the current sampling resistor between power switch and ground, and feedback voltage and feedback current control power switch based on the assists winding from transformer are changed into conducting state from cut-off state, feedback voltage characterizes the system output voltage of flyback power supply system, and feedback current characterizes the system input voltage of flyback power supply system.
Description
Technical field
The present invention relates to circuit field, more particularly to a kind of flyback power supply system and its control method.
Background technology
Typically, flyback power supply system isolates primary side input and secondary output by transformer, and passes through such as optocoupler
Etc isolation element the sample information of output voltage is fed back into control chip positioned at primary side side, to cause control chip
Output voltage can be adjusted according to the sample information of output voltage.But, the isolation element of such as optocoupler etc is no
The cost of flyback power supply system can only be increased, and can turn into inverse-excitation type electricity because the service life of itself is very limited
One of restraining factors of service life of source system.
In consideration of it, proposing a kind of flyback power supply system based on primary side feedback, the flyback power supply system is without logical
Cross any isolation element and the sample information of output voltage fed back into control chip positioned at primary side side, and be based on directly on from
Output voltage is adjusted for primary side side sampling obtained voltage/current information.
The content of the invention
One or more problems in view of the above, the invention provides a kind of flyback power supply system and its controlling party
Method, can be according to the feedback of the current sample voltage of the primary side side from transformer and the assists winding from transformer electricity
Press with feedback current to control the state of power switch to switch, so that control system output current.
Flyback power supply system according to embodiments of the present invention, including transformer, be connected with the primary side winding of transformer
Power switch and it is changed into cut-off state from conducting state for controlling power switch or is changed into conducting state from cut-off state
System control module, wherein：System control module is based on being connected on the current sampling resistor between power switch and ground
Current sample voltage control power switch is changed into cut-off state from conducting state, and based on the assists winding from transformer
Feedback voltage and feedback current control power switch to be changed into conducting state from cut-off state, and feedback voltage characterizes flyback power supply system
The system output voltage of system, feedback current characterizes the system input voltage of flyback power supply system.
In certain embodiments, system control module determines the vice-side winding ON time of transformer based on feedback voltage,
And the vice-side winding ON time control based on the magnitude relationship between feedback current and first threshold electric current and transformer
Power switch is changed into conducting state from cut-off state, to cause the vice-side winding ON time of transformer and the switch of power switch
Ratio between cycle for the first value and is more than first threshold when feedback current is less than first threshold electric current in feedback current
It is second value during electric current.
In certain embodiments, when current sample voltage is more than first threshold voltage, system control module control power
Switch is changed into cut-off state from conducting state.
In certain embodiments, system control module includes secondary ON time detection circuit, the detection of secondary ON time
Whether circuit is in based on the vice-side winding that the magnitude relationship generation between feedback voltage and second threshold voltage characterizes transformer
The conducting state indication signal of conducting state.
In certain embodiments, system control module includes line voltage-line current change-over circuit and first comparator, line electricity
Feedback current is converted to line current by pressure-line current change-over circuit according to predetermined transformational relation, and first comparator is based on
Magnitude relationship between line current and Second Threshold electric current generates the first comparative result indication signal, Second Threshold electric current and first
Threshold current is proportional.
In certain embodiments, system control module includes variableratio control module, and variableratio control module includes
First to the 3rd current mirror, capacitor and the second comparator, wherein：First current mirror is in the first comparative result indication signal
Control under, capacitor is charged；Second current mirror fills under the control of conducting state indication signal to capacitor
Electricity；3rd current mirror discharges capacitor under the control of conducting state indication signal, and the second comparator is based on capacitor
On voltage and the 3rd threshold voltage between magnitude relationship generate the second comparative result indication signal, for controlling power switch
It is changed into conducting state from cut-off state.
In certain embodiments, system control module also includes the 3rd comparator and rest-set flip-flop, and the 3rd comparator is based on
Magnitude relationship between current sample voltage and first threshold voltage generates the 3rd comparative result indication signal, and rest-set flip-flop is based on
Second comparative result indication signal and the 3rd comparative result indication signal are generated for controlling power switch to be changed into from conducting state
Cut-off state or the pulse frequency modulated signal for being changed into conducting state from cut-off state.
In certain embodiments, feedback voltage is in the assists winding of transformer when power switch is in the conduction state
Voltage carry out partial pressure and obtain.
Control method for flyback power supply system according to embodiments of the present invention, flyback power supply system includes transformation
Device and the power switch being connected with the primary side winding of transformer, the control method include：Based on being connected to power switch and ground
Between current sampling resistor on current sample voltage control power switch to be changed into cut-off state from conducting state, and based on coming
Power switch is controlled to be changed into conducting state from cut-off state from the feedback voltage and feedback current of the assists winding of transformer, its
In, feedback voltage characterizes the system output voltage of flyback power supply system, the system that feedback current characterizes flyback power supply system
Input voltage.
In certain embodiments, the vice-side winding ON time of transformer is determined based on feedback voltage, and based on feedback
The vice-side winding ON time of magnitude relationship and transformer between electric current and first threshold electric current controls power switch from cutting
Only state is changed into conducting state, to cause the ratio between the vice-side winding ON time of transformer and the switch periods of power switch
Value is the first value and is second when feedback current is more than first threshold electric current when feedback current is less than first threshold electric current
Value.
Brief description of the drawings
From below in conjunction with the accompanying drawings to the present invention embodiment description in the present invention may be better understood, its
In：
Fig. 1 shows the circuit diagram of traditional flyback power supply system based on primary side feedback；
Fig. 2 shows the circuit diagram of flyback power supply system according to embodiments of the present invention；
Fig. 3 shows the exemplary circuit figure of the secondary ON time detection module in Fig. 2；
Fig. 4 shows the exemplary circuit figure of the variableratio control module in Fig. 2；
Fig. 5 shows that secondary ON time detection module in fig. 2 and variableratio control module are implemented as respectively
During exemplary circuit shown in Fig. 3 and Fig. 4, output characterizes voltage VFB, conducting state indication signal State_Tons, on electric capacity C
Voltage Vramp, state control signal CC_ctrl and PFM signal timing diagram；
Fig. 6 shows the system output current of the flyback power supply system shown in Fig. 2 with showing that system input voltage changes
It is intended to.
Embodiment
The feature and exemplary embodiment of various aspects of the invention is described more fully below.In following detailed description
In, it is proposed that many details, to provide complete understanding of the present invention.But, to those skilled in the art
It will be apparent that the present invention can be implemented in the case of some details in not needing these details.Below to implementing
The description of example is used for the purpose of by showing that the example of the present invention is better understood to provide to the present invention.The present invention is never limited
In any concrete configuration set forth below and algorithm, but cover under the premise of without departing from the spirit of the present invention element,
Any modification, replacement and the improvement of part and algorithm.In the the accompanying drawings and the following description, known structure and skill is not shown
Art, to avoid causing the present invention unnecessary obscure.
Fig. 1 shows the circuit diagram of traditional flyback power supply system based on primary side feedback.In the inverse-excitation type shown in Fig. 1
In the case that power-supply system works in discontinuous conduct mode (DCM)：When power switch Q1 is in the conduction state, transformer T1 storages
Energy is deposited, the electricity on the primary side current of transformer Ics linear rises of transformer T1 primary side winding, current sampling resistor Rs is flowed through
Flow sampled voltage Vcs linear rises；When the current sample voltage Vcs on current sampling resistor Rs reaches threshold voltage vt h, work(
Rate switch Q1 is changed into cut-off state from conducting state；When power switch Q1 is in cut-off state, transformer T1 releases energy, stream
Cross the transformer secondary side current Isec linear declines of transformer T1 vice-side winding.
According to primary-side-control principle, the system output current of the flyback power supply system shown in Fig. 1 flows through load Ro's
Electric current Iout can be expressed as：
Wherein, N is transformer T1 primary side winding and the turn ratio of vice-side winding, Ip be flow through transformer T1 primary side around
The transformer primary side peak point current (that is, primary side current of transformer Ics peak value) of group, when Tons is transformer T1 secondary conducting
Between, Ts is power switch Q switch periods.
It can be seen from equation 1 and equation 2, as long as ensure transformer T1 secondary ON time Tons and power switch Q
Switch periods Ts ratio and flow through transformer T1 primary side winding transformer primary side peak point current Ip be fixed value, so that it may
So that the system output current of the flyback power supply system shown in Fig. 1 keeps constant.In this case, no matter shown in Fig. 1
Whether the system input voltage of flyback power supply system is constant, and its system output current all keeps constant.
In some power network less developed countries or area, for example, India, AC-input voltage rather unstable, if Fig. 1
Shown flyback power supply system remains in that system output current is constant when AC-input voltage is too high, then can be due to system
Overheat and damage.
In view of the above problems, it is proposed that a kind of novel flyback power supply system, can be according to the primary side from transformer
The output of the current sample voltage of side and the secondary side from transformer characterizes both voltage to control the state of power switch to cut
Change, so that control system output current.
Fig. 2 shows the circuit diagram of flyback power supply system according to embodiments of the present invention.As shown in Fig. 2 according to this hair
The flyback power supply system of bright embodiment includes transformer T1, the rectification filtering module 202 positioned at transformer T1 primary side side, is
System control module 204, power switch Q1 and current sampling resistor Rs and the feedback partial pressure positioned at transformer T1 secondary side
Resistance R1 and R2, wherein：The first terminal and Second terminal of rectification filtering module 202 be used for respectively with the positive pole of AC power and
Negative pole is connected, and the third terminal of rectification filtering module 202 is connected with transformer T1 primary side winding inductance L the first terminal, whole
Flow the forth terminal ground connection of filtration module 202；The BD terminals of system control module 204 are connected with power switch Q1 base stage, are
System control module 204 CS terminals be connected with current sampling resistor Rs the first terminal, the FB terminals of system control module 204 and
Feed back the connecting node connection between divider resistance R1 and R2；Power switch Q1 colelctor electrode and transformer T1 primary side winding electricity
Feel L Second terminal connection, power switch Q1 emitter stage is connected with current sampling resistor Rs the first terminal；Current sample electricity
Hinder Rs Second terminal ground connection；Feedback divider resistance R1 and R2 are connected in series in the Same Name of Ends and ground of transformer T1 assists winding
Between.
In the flyback power supply system shown in Fig. 2, rectification filtering module 202 passes through to AC-input voltage VACCarry out whole
Stream and filtering generation line voltage Vbulk；When power switch Q1 is in the conduction state, the voltage in transformer T1 assists winding
Vaux is negative pressure and size is proportional to line voltage Vbulk, specific as follows：
Wherein, Naux is the number of turn of transformer T1 assists winding, and Np is the number of turn of transformer T1 primary side winding.
When power switch Q1 is in the conduction state, the voltage Vaux in transformer T1 assists winding can characterize line electricity
Press Vbulk (that is, system input voltage), therefore the feedback current I of the assists winding from transformer T1FBLine electricity can also be characterized
Press Vbulk.When power switch Q1 is in cut-off state, the voltage Vaux in transformer T1 assists winding exports electricity with system
Pressure, i.e. the voltage Vout on load Ro is proportional, therefore the feedback voltage V of the assists winding from transformer T1FBIt can characterize
System output voltage Vout.
In the flyback power supply system shown in Fig. 2, system control module 204 can be according on current sampling resistor Rs
Current sample voltage Vcs and assists winding from transformer T1 feedback voltage VFBWith feedback current IFBTo control power
Switch Q1 is changed into cut-off state from conducting state or is changed into conducting state from cut-off state, so that control system output current,
Flow through load Ro electric current Iout.
Specifically, when power switch Q1 is in the conduction state, transformer T1 storage energy flows through transformer T1 primary side
Current sample voltage Vcs linear rises on the primary side current of transformer Ics linear rises of winding, current sampling resistor Rs；When
When current sample voltage Vcs on current sampling resistor Rs reaches threshold voltage vt h, the control power of system control module 204 is opened
Close Q1 and be changed into cut-off state from conducting state.When power switch Q1 is in cut-off state, system control module 204 can basis
The feedback voltage V of assists winding from transformer T1FBTo judge when transformer T1 vice-side winding starts to demagnetize and what
When terminate demagnetization (that is, the secondary ON time Tons for detecting transformer T1), and according to transformer T1 secondary ON time
Tons and assists winding from transformer T1 feedback current IFBWith the size between overvoltage protection threshold electric current Iovp_1
Relation controls power switch Q1 to be changed into conducting state from cut-off state, with cause transformer T1 secondary ON time Tons with
The feedback current I of ratio (Tons/Ts) between power switch Q1 switch periods Ts in the assists winding from transformer T1FB
For K1 and in the feedback current I from transformer T1 during less than overvoltage protection threshold electric current Iovp_1FBMore than overvoltage protection threshold
It is K2 when being worth electric current Iovp_1.
In certain embodiments, system control module 204 may further include line voltage-line current change-over circuit 204-
2nd, secondary ON time detection circuit 204-4, variable ratio duty control circuit 204-6, rest-set flip-flop, switch driving circuit 204-8,
And comparator cmp1 and cmp2, wherein：
Line voltage-line current change-over circuit 204-2 can be when power switch Q1 be in the conduction state line voltage Vbulk
Sample and be converted into line current Iline, line current Iline is then output to comparator cmp1.For example, line voltage-line
Current converter circuit 204-2 can be converted into line current Iline according to below equation and with reference to equation 3 by line voltage Ibulk：
Wherein, A represents conversion coefficient and is constant.
Line current Iline can be compared by comparator cmp1 with overvoltage protection threshold electric current Iovp_2, and will be compared
Result indicative signal Line_high is output to variable ratio duty control circuit 204-6.Here, protected when line current Iline is less than overvoltage
When protecting threshold current Iovp_2, the comparative result indication signal Line_high of comparator cmp1 outputs is low level；Work as line current
When Iline is more than overvoltage protection threshold electric current Iovp_2, the comparative result indication signal Line_high of comparator cmp1 outputs is
High level.Here, Iovp_1=Iovp_2 × A.
Secondary ON time detection circuit 204-4 can be according to the feedback voltage V of the assists winding from transformer T1FBCome
Judge when transformer T1 vice-side winding starts to demagnetize and when terminate demagnetization, that is, when detecting transformer T1 secondary conducting
Between Tons, and transformer T1 secondary ON time Tons is supplied to variable ratio duty control circuit 204-6.
Fig. 3 shows the exemplary circuit figure of the secondary ON time detection module in Fig. 2.As shown in figure 3, comparator cmp4
By the feedback voltage V for comparing the assists winding from transformer T1FBWhether it is higher than for example, 0.1V judges transformer T1 pair
The demagnetization of side winding starts and terminated.When the feedback voltage V of the assists winding from transformer T1FBDuring higher than 0.1V, indicate to become
Depressor T1 vice-side winding starts demagnetization, i.e. the vice-side winding of transformer T1 is in the conduction state；When from the auxiliary of transformer T1
Help the feedback voltage V of windingFBDuring less than 0.1V, indicating transformer T1 vice-side winding terminates demagnetization, i.e. transformer T1 secondary
Winding is in cut-off state.
The output signal of secondary ON time detection module shown in Fig. 3 is whether the vice-side winding for characterizing transformer T1 is located
In the conducting state indication signal State_Tons of conducting state；When transformer T1 vice-side winding is in the conduction state, lead
Logical condition indicative signal State_Tons is high level；When transformer T1 vice-side winding is in cut-off state, conducting state
Indication signal State_Tons is low level.
Variable ratio duty control circuit 204-6 can utilize change when comparative result indication signal Line_high is low level
Depressor T1 secondary ON time Tons determines power switch Q1 switch periods based on Tons/Ts=K1, and is based on being determined
Power switch Q1 switch periods control power switch Q1 be changed into conducting state from cut-off state so that system output electricity
StreamWhen comparative result indication signal Line_high is high level, led using transformer T1 secondary
Logical time Tons determines power switch Q1 switch periods based on Tons/Ts=K2, and based on identified power switch Q1's
Switch periods control power switch Q1 is changed into conducting state from cut-off state, so that system output current
Fig. 4 shows the exemplary circuit figure of the variableratio control module in Fig. 2.As shown in figure 4, when secondary ON time
When the conducting state indication signal State_Tons of detection module output is high level, current mirror I2 discharges electric capacity C, electric capacity C
On voltage Vramp linear declines；The conducting state indication signal State_Tons exported when secondary ON time detection module
During for low level, current mirror I1 or Ii+I0 is charged to electric capacity C, and the voltage Vramp on electric capacity C is linearly raised；When on electric capacity C
Voltage Vramp be higher than threshold voltage VR when, comparator cmp3 output state control signal CC-ctrl be high level；Work as electricity
When holding the voltage Vramp on C less than VR, the state control signal CC-ctrl of comparator cmp3 outputs is low level.
Comparator cmp2 can be compared the current sample voltage Vcs on current sampling resistor Rs and threshold voltage vt h
Compared with, and comparative result indication signal OCP is output to rest-set flip-flop.Here, when the current sample electricity on current sampling resistor Rs
When pressing Vcs more than threshold voltage vt h, the comparative result indication signal OCP of comparator cmp2 outputs is high level；Work as current sample
When current sample voltage Vcs on resistance Rs is less than threshold voltage vt h, the comparative result indication signal of comparator cmp2 outputs
OCP is low level.
Rest-set flip-flop can be based on the comparative result indication signal OCP from comparator cmp2 and from variableratio control
Module 204-6 state control signal CC_ctrl, generates pulse frequency modulated (PFM) signal.
Switch drive module 204-8 can be generated for power switch Q1's based on the PFM signals from rest-set flip-flop
Drive signal.
Fig. 5 shows that secondary ON time detection module in fig. 2 and variableratio control module are implemented as respectively
During exemplary circuit shown in Fig. 3 and Fig. 4, the feedback voltage V of the assists winding from transformer T1FB, conducting state indication signal
Voltage Vramp, the timing diagram of state control signal CC_ctrl and PFM signal on State_Tons, electric capacity C.
By be analyzed above it is recognised that when line current Iline be less than overvoltage protection threshold electric current Iovp_2 when, comparator
The comparative result indication signal Line_high of cmp1 outputs is low level, power switch Q1 switch periodsTransformer T1 transformer primary side peak point currentSystem output currentWhen line current Iline is more than overvoltage protection threshold electric current Iovp_2, comparator
The comparative result indication signal Line_high of cmp1 outputs is high level, power switch Q1 switch periodsTransformer T1 transformer primary side peak point currentSystem output current
Fig. 6 shows the system output current of the flyback power supply system shown in Fig. 2 with showing that system input voltage changes
It is intended to.As shown in fig. 6, when line voltage Vbulk is less than threshold voltage vt h_bulk, system output current is CC1, works as line voltage
When Vbulk voltages are more than threshold voltage vt h_bulk, system output current is CC2.As can be seen that too high in system input voltage
When, system output current is proportional to diminish, and this is conducive to being avoided system overheat.
Need clearly, the invention is not limited in particular configuration that is described above and being shown in figure and processing.Also,
For brevity, the detailed description to known method technology is omitted here.In the above-described embodiments, have been described and illustrated some
Specific step is used as example.But, procedure of the invention is not limited to described and illustrated specific steps, this area
Technical staff can understand the present invention spirit after, make various changes, modification and add.
The present invention can be realized in other specific forms, without departing from its spirit and essential characteristics.For example, particular implementation
Algorithm described in example can be changed, and system architecture is without departing from the essence spirit of the present invention.Therefore, it is current
Embodiment be all counted as being exemplary rather than in all respects it is limited, the scope of the present invention by appended claims rather than
Foregoing description is defined, also, fall into the range of the implication and equivalent of claim whole change all to be included in
Among the scope of the present invention.
Claims (10)
1. a kind of flyback power supply system, including transformer, the power switch that is connected with the primary side winding of the transformer and
It is changed into cut-off state from conducting state for controlling the power switch or is changed into the system control of conducting state from cut-off state
Molding block, wherein：
The system control module is based on the current sample on the current sampling resistor being connected between the power switch and ground
Voltage controls the power switch to be changed into cut-off state from conducting state, and based on the assists winding from the transformer
Feedback voltage and feedback current control the power switch to be changed into conducting state from cut-off state, and the feedback voltage characterizes described
The system output voltage of flyback power supply system, the feedback current characterizes the system input electricity of the flyback power supply system
Pressure.
2. flyback power supply system as claimed in claim 1, wherein, it is true that the system control module is based on the feedback voltage
The vice-side winding ON time of the fixed transformer, and closed based on the size between the feedback current and first threshold electric current
The vice-side winding ON time of system and the transformer controls the power switch to be changed into conducting state from cut-off state, with
So that the ratio between the vice-side winding ON time of the transformer and the switch periods of the power switch is in the feedback
Electric current be less than the first threshold electric current when be the first value and the feedback current be more than the first threshold electric current when be
Second value.
3. flyback power supply system as claimed in claim 1, wherein, when the current sample voltage is more than first threshold voltage
When, the system control module controls the power switch to be changed into cut-off state from conducting state.
4. flyback power supply system as claimed in claim 2, wherein, the system control module is examined including secondary ON time
Slowdown monitoring circuit, the secondary ON time detection circuit is based on the magnitude relationship life between the feedback voltage and second threshold voltage
Into the vice-side winding for characterizing transformer conducting state indication signal whether in the conduction state.
5. the flyback power supply system as described in claim 2 or 4, wherein, the system control module includes line voltage-line electricity
Change-over circuit and first comparator are flowed, the line voltage-line current change-over circuit will be described according to predetermined transformational relation
Feedback current is converted to line current, and the first comparator is based on the magnitude relationship between the line current and Second Threshold electric current
The first comparative result indication signal is generated, the Second Threshold electric current is proportional to the first threshold voltage.
6. flyback power supply system as claimed in claim 5, wherein, the system control module includes variableratio and controls mould
Block, the variableratio control module includes the first to the 3rd current mirror, capacitor and the second comparator, wherein
First current mirror charges under the control of the first comparative result indication signal to the capacitor,
Second current mirror charges under the control of the conducting state indication signal to the capacitor,
3rd current mirror discharges the capacitor under the control of the conducting state indication signal,
Second comparator is based on the magnitude relationship generation second between the voltage on the capacitor and the 3rd threshold voltage
Comparative result indication signal, conducting state is changed into for controlling the power switch from cut-off state.
7. flyback power supply system as claimed in claim 6, wherein, the system control module also include the 3rd comparator and
Rest-set flip-flop, the 3rd comparator is given birth to based on the magnitude relationship between the current sample voltage and the first threshold voltage
Into the 3rd comparative result indication signal, the rest-set flip-flop is compared based on the second comparative result indication signal and the described 3rd
Result indicative signal is generated for controlling the power switch to be changed into cut-off state from conducting state or be changed into from cut-off state
The pulse frequency modulated signal of conducting state.
8. flyback power supply system as claimed in claim 1, wherein, the feedback voltage is to be in lead in the power switch
What partial pressure was obtained is carried out to the voltage in the assists winding of the transformer during logical state.
9. a kind of control method for flyback power supply system, the flyback power supply system includes transformer and become with described
The power switch of the primary side winding connection of depressor, the control method includes：
The power is controlled based on the current sample voltage on the current sampling resistor being connected between the power switch and ground
Switch is changed into cut-off state, and the feedback voltage based on the assists winding from the transformer and feedback electricity from conducting state
Power switch described in flow control is changed into conducting state from cut-off state, and the feedback voltage characterizes the flyback power supply system
System output voltage, the feedback current characterizes the system input voltage of the flyback power supply system.
10. control method as claimed in claim 9, wherein, based on the feedback voltage determine the secondary of the transformer around
Group ON time, and based on the magnitude relationship between the feedback current and first threshold electric current and the transformer
Vice-side winding ON time controls the power switch to be changed into conducting state from cut-off state, to cause the secondary of the transformer
Ratio between the switch periods of winding ON time and the power switch is less than the first threshold in the feedback current
Be during electric current the first value and the feedback current be more than the first threshold electric current when be second value.
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| CN201710279652.7A CN106992684B (en) | 2017-04-25 | 2017-04-25 | Flyback power supply system and its control method |
| TW106117737A TWI636647B (en) | 2017-04-25 | 2017-05-26 | Flyback power system and control method thereof |
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| CN201710279652.7A CN106992684B (en) | 2017-04-25 | 2017-04-25 | Flyback power supply system and its control method |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109406860A (en) * | 2018-12-24 | 2019-03-01 | 厦门能瑞康电子有限公司 | A kind of voltage sampling circuit |
| CN111262437A (en) * | 2018-12-03 | 2020-06-09 | 新日本无线株式会社 | Switching power supply device |
| WO2021127957A1 (en) * | 2019-12-24 | 2021-07-01 | 深圳大学 | Flyback converter constant-current control circuit |
| CN114624499A (en) * | 2022-03-15 | 2022-06-14 | 无锡市晶源微电子有限公司 | Output voltage sampling circuit of switching power supply |
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| CN114624499A (en) * | 2022-03-15 | 2022-06-14 | 无锡市晶源微电子有限公司 | Output voltage sampling circuit of switching power supply |
| CN114624499B (en) * | 2022-03-15 | 2023-09-19 | 无锡市晶源微电子股份有限公司 | Output voltage sampling circuit of switching power supply |
| CN115800767A (en) * | 2023-01-31 | 2023-03-14 | 深圳市芯茂微电子有限公司 | Control method of switching power supply and switching power supply |
Also Published As
| Publication number | Publication date |
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| TW201840108A (en) | 2018-11-01 |
| CN106992684B (en) | 2019-06-21 |
| TWI636647B (en) | 2018-09-21 |
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