CN104601015A - Flyback AC-DC converter - Google Patents
Flyback AC-DC converter Download PDFInfo
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- CN104601015A CN104601015A CN201410015595.8A CN201410015595A CN104601015A CN 104601015 A CN104601015 A CN 104601015A CN 201410015595 A CN201410015595 A CN 201410015595A CN 104601015 A CN104601015 A CN 104601015A
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/2173—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a biphase or polyphase circuit arrangement
-
- 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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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
- Rectifiers (AREA)
Abstract
The invention discloses a flyback AC-DC converter. The flyback AC-DC converter is characterized in that a line voltage detecting and compensating module is added to an AC-DC control chip to indirectly detect line voltage and generate a compensation dosage which changes as the liner voltage changes; the compensation dosage is overlapped to a feedback signal, and the overlapped compensation dosage increases as the line voltage increases; the feedback signal subjected to line voltage compensation is controlled and adjusted to perform linear down conversion, thus the load point at the beginning of down conversion and the inclination rate of a down conversion curve can be nearly kept consistent in a wide input line voltage range (85-264V), and as a result, the optimal electromagnetic interference performance can be obtained while increasing the conversion efficiency.
Description
Technical field
The present invention relates to switch power technology field, particularly relate to a kind of inverse-excitation type AC-DC converter.
Background technology
AC-DC(AC-DC) transducer is widely used in nearly all electronic equipment.Existing AC-DC converter applies traditional AC-DC control chip, and traditional AC-DC control chip is all the break-make being controlled external power switching tube by totem driver output.In order to improve conversion efficiency, the function of linear frequency reducing is all added in a new generation AC-DC control chip, namely along with output load reduction to a certain extent (such as semi-load), frequency can decline from the 65KHz of full load, and linear with power output, power output is less, and frequency is fallen lower, thus significantly reduce switching loss, improve conversion efficiency.In order to not make frequency drop to (i.e. 20Hz ~ 20KHz) in audiorange, the lower-frequency limit of linear frequency reducing is generally at more than 20KHz.
The control signal of linear frequency reducing is generally the feedback (FeedBack of AC-DC control chip at present, FB) pin, because the voltage of feedback pin directly reflects the size of load, when load by heavy duty gradually excessively to underloading time, the voltage of feedback pin also can by height step-down gradually, feedback signal is compared by internal pulses width modulated (PWM) comparator and primary current detection signal, and when making the former limit conducting of each cycle, former limit peak current diminishes, thus reduces the transmission of energy; Therefore concerning control AC-DC control chip, feedback pin can directly as load detecting pin, is used for control linear frequency reducing.
Refer to Fig. 1, it is the schematic diagram of a traditional inverse-excitation type AC-DC converter.Wherein, AC-DC control chip 104 comprises a feedback signal input terminal FB, former limit peak current sense terminal CS, an energization pins VCC, pin GND and the output OUT in a ground.Output OUT exports the control signal VG of suitable duty ratio according to the voltage swing of feedback signal, with driving switch pipe Q100.The one termination primary current detecting resistance R100 of switching tube Q100, the former limit N of another termination transformer 106
psame Name of Ends, the former limit N of transformer 106
panother termination rectification after line voltage.The secondary N of transformer 106
sload incoming end 108 is connected with electric capacity C300 by rectifier diode D200.Transformer 106 also comprises an auxiliary winding N
a, it is that AC-DC control chip 104 is powered by another rectifier diode D100 and electric capacity C200.The load incoming end 108 of this inverse-excitation type AC-DC converter produces by divider resistance R300, R400 and light lotus root device VL100, operational amplifier U100 and resistance R200 the feedback signal input terminal FB feeding back signal to AC-DC control chip 104.The output OUT of AC-DC control chip 104 is used for driving switch pipe Q100.
When the systems are operating normally, by secondary N
sdivider resistance R300, R400 and light lotus root device VL100, operational amplifier U100 and resistance R200 composition feedback unit can according to the size of load on this inverse-excitation type AC-DC converter load incoming end 108, produce feedback signal, this feedback signal is by pwm comparator 202 and former limit N
ppeak current detection signal compares, for controlling former limit N of each cycle
pthe size of peak current; When on this inverse-excitation type AC-DC converter load incoming end 108, load is larger, the voltage of feedback signal is higher, and each cycle peak current detection signal is also higher, i.e. former limit N
ppeak current is higher; When on this inverse-excitation type AC-DC converter load incoming end 108 during load reduction, the voltage of feedback signal also reduces, former limit N of each cycle
ppeak current also declines thereupon, and system ensures the balance of Energy Transfer by such feedback, and then maintains the stable of output voltage on this inverse-excitation type AC-DC converter load incoming end 108.In order in, underloading time reduce the switching loss of system, improve conversion efficiency, AC-DC control chip 104 goes modulating frequency according to the size of the voltage of feedback signal.
When load reduction on load incoming end 108 to a certain extent time (as semi-load), the voltage drop of feedback signal is to the threshold value V of setting
th1, now operating frequency declines by normal 65KHz; When load on load incoming end 108 is reduced to a lower degree further (as fully loaded 10%), the voltage drop of feedback signal is to the threshold value V set
th2, now operating frequency drops to minimum 22KHz; This back loading reduces further until unloaded, and operating frequency maintains 22KHz always, and AC-DC control chip can enter skip cycle mode (Burst Mode).
Under identical feedback signal, although line voltage is different, AC-DC control chip 104 can send cut-off signals after detecting identical former limit peak current, but there is intrinsic turn off delay time t due to system
d, after making AC-DC control chip 104 send cut-off signals, former limit N
pstill conducting t can be continued
dtime, during this period of time former limit peak electricity fail to be convened for lack of a quorum continue with (V
in/ L
p) slope rise, V
infor the line voltage after rectification, L
pfor the former limit sensibility reciprocal of transformer, at identical time t
din, line voltage is higher, and former limit true peak electric current is higher, to secondary N
sthe energy of transmission is larger, and namely under identical feedback signal, line voltage is higher, and load is larger.If system works is in continuous mode (CCM) in addition, then under identical former limit peak current, line voltage is higher, former limit N
poN time is shorter, secondary N
sdischarge time is longer, and the energy of transmission is more, and also can cause under identical feedback signal, line voltage is higher, and load is larger; This can bring a serious problem, when namely on-Line Voltage is lower, supposes FB=V
th1, corresponding is semi-load, and so under this line voltage, when load reduction is to semi-load, system will start to reduce operating frequency; And on-Line Voltage very high time, FB=V
th1corresponding load can far away higher than semi-load, even reach fully loaded, when so on-Line Voltage is higher, system will start to reduce operating frequency at full load, this can have a strong impact on Conducted Electromagnetic Interference (the Electro Magnetic Interference of system, EMI), make its performance become very poor, cannot meet the demands.
Therefore, prior art existing defects, needs to improve.
Summary of the invention
Technical problem to be solved by this invention is: provide a kind of inverse-excitation type AC-DC converter, modulating frequency is gone according to the size of the voltage of feedback signal to solve AC-DC control chip in prior art, the Conducted Electromagnetic Interference of system can be had a strong impact on, make the problem of its degradation.
Technical scheme of the present invention is as follows: the invention provides a kind of inverse-excitation type AC-DC converter, comprising: alternating current input, rectification unit, transformer, the first to the second diode, AC-DC control chip, feedback module, the first transistor and load incoming end, described AC-DC control chip has power pins, control output pin, detection signal input pin, feedback pin and earth connection pin, described rectification unit and described alternating current input are electrically connected, described transformer respectively with described rectification unit, one end of first diode, one end of second diode, the first transistor, and load incoming end is electrically connected, the other end and the described load incoming end of described second diode are electrically connected, and the other end of described power pins and the first diode is electrically connected, described control output pin, detection signal input pin is electrically connected with the first transistor respectively, and described feedback pin and feedback module are electrically connected, and described feedback module is also electrically connected with described load incoming end, described rectification unit, transformer, the earth connection pin of AC-DC control chip, feedback module, and the first transistor is all electrically connected with ground wire,
Described AC-DC control chip comprises: under-voltage protective module, built-in power module, reference voltage module, driver output module, Logic control module, oscillator, overcurrent protection, overvoltage protection, PWM comparator, lead-edge-blanking module and line detecting voltage and compensating module, described under-voltage protective module and built-in power module are all electrically connected with power pins, described built-in power module is also electrically connected with described reference voltage module, described reference voltage module is also electrically connected with overcurrent protection and overvoltage protection respectively, described lead-edge-blanking respectively with detection signal input pin, overcurrent protection, and PWM comparator is electrically connected, described PWM comparator, overvoltage protection, and line detecting voltage and compensating module are all electrically connected with feedback pin, described line detecting voltage and compensating module also respectively with described oscillator, control output pin, built-in power module, the other end of the second diode and detection signal input pin are electrically connected, described Logic control module respectively with oscillator, overvoltage protection, PWM comparator, overcurrent protection, and driver output module is electrically connected, described driver output module is also electrically connected with described control output pin.
Described inverse-excitation type AC-DC converter also comprises: the first resistance and the first to the 3rd electric capacity; Described first resistance one end is electrically connected with the first transistor, detection signal input pin respectively, and the other end and ground wire are electrically connected; Described first electric capacity one end and rectification unit are electrically connected, and the other end and ground wire are electrically connected; Described second electric capacity one end and power pins are electrically connected, and the other end and ground wire are electrically connected; Described 3rd electric capacity and load incoming end are connected in parallel.
Described transformer comprises: former limit, secondary and auxiliary winding, and described secondary is used for powering load, and described auxiliary winding is used for powering to AC-DC control chip.
Described feedback module comprises optocoupler, the first operational amplifier and the second to the 4th resistance; The other end, the load incoming end of described second resistance one end and the second diode are electrically connected, and the other end and optocoupler are electrically connected; The other end, the load incoming end of described 3rd resistance one end and the second diode are electrically connected, and one end of the other end and the 4th resistance is electrically connected, and the other end and the load incoming end of described 4th resistance are electrically connected; Described first operational amplifier is electrically connected with one end of the 4th resistance, the other end of the 4th resistance and optocoupler respectively; Described optocoupler is also electrically connected with feedback pin, ground wire respectively.
Described the first transistor has first grid, the first drain electrode and the first source electrode, described first grid and described control output pin are electrically connected, described first source electrode and transformer are electrically connected, and described first drain electrode is electrically connected with one end of the first resistance and detection signal input pin respectively.
Described line detecting voltage and compensating module comprise: sampled signal generation module, first switch, second switch, second operational amplifier, 3rd operational amplifier, transistor seconds, third transistor, 5th resistance and the 6th resistance, described second operational amplifier has the first positive input pin, first negative input pin and the first output pin, described 3rd operational amplifier has the second positive input pin, second negative input pin and the second output pin, described transistor seconds has second grid, second drain electrode and the second source electrode, described third transistor has the 3rd grid, 3rd drain electrode and the 3rd source electrode, described sampled signal module respectively with control output pin, first switch, and second switch be electrically connected, described first switch also respectively with described detection signal input pin, one end of 4th electric capacity, first negative input pin be electrically connected, described second switch also respectively with detection signal input pin, one end of 5th electric capacity, second positive input pin is electrically connected, one end of described first positive input pin and the 5th resistance, second drain electrode is electrically connected, the other end of described 5th resistance and the second negative input pin, second output pin is electrically connected, described first output pin and second, 3rd grid is electrically connected, described second source electrode, 3rd source electrode is all electrically connected with built-in power module, described 3rd drain electrode and oscillator, one end of 6th resistance is electrically connected, and the other end and the feedback pin of described 6th resistance are electrically connected, the other end of described 4th electric capacity, the other end of the 5th electric capacity is all electrically connected with ground wire.
Adopt such scheme, inverse-excitation type AC-DC converter of the present invention, by detecting the line voltage of linear frequency reducing, be superimposed on FB signal to produce a compensation rate changed with line change in voltage, make in wide input voltage range (85-264V), the slope that system starts the POL and frequency reducing curve (F-Po) entering frequency reducing all keeps identical, thus while raising conversion efficiency, obtains best electromagnetic interference performance.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of traditional inverse-excitation type AC-DC converter.
Fig. 2 is the schematic diagram of inverse-excitation type AC-DC converter of the present invention.
Fig. 3 is the circuit diagram of neutral voltage of the present invention detecting and compensating module and annexation thereof.
Fig. 4 is the oscillogram of sampled signal S1, S2 and peak current detection signal CS in the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.
Refer to Fig. 2, the invention provides a kind of inverse-excitation type AC-DC converter, in order to improve the performance of linear frequency reducing, it is made not change with line voltage (obtaining after rectification unit rectification) change, to obtain best systematic function, the present invention controls to add line detecting voltage and compensating module 61 in 60, core at AC-DC, this line detecting voltage and compensating module 61 pass through detection lines voltage indirectly, produce a compensation rate changed with line change in voltage, this compensation rate is superimposed in feedback signal, line voltage is larger, then the compensation rate that gets on of this superposition is also larger, feedback signal like this after line voltage compensation, go the linear frequency reducing of control and regulation again, thus the POL of beginning frequency reducing and frequency reducing slope of a curve within the scope of wide input line voltage (85-264V) are all almost consistent, thus while raising conversion efficiency, obtain best electromagnetic interference performance.
This inverse-excitation type AC-DC converter comprises: alternating current input 52, rectification unit 54, transformer 56, the first to the second diode D1, D2, AC-DC control chip 60, feedback module 58, the first transistor Q1 and load incoming end 59, described AC-DC control chip 60 has power pins V
cc, control output pin OUT, detection signal input pin CS, feedback pin FB and earth connection pin, described rectification unit 54 is electrically connected with described alternating current input 52, described transformer 56 is electrically connected with one end of one end of described rectification unit 54, first diode D1, the second diode D2, the first transistor Q1 and load incoming end 59 respectively, the other end and the described load incoming end 59 of described second diode D2 are electrically connected, described power pins V
ccbe electrically connected with the other end of the first diode D1, described control output pin OUT, detection signal input pin CS are electrically connected with the first transistor Q1 respectively, described feedback pin FB and feedback module 58 are electrically connected, described feedback module 58 is also electrically connected with the other end of described load incoming end 59, second diode D2, and the earth connection pin of described rectification unit 54, transformer 56, AC-DC control chip 60, feedback module 58 and the first transistor Q1 are all electrically connected with ground wire.
Described AC-DC control chip 60 comprises: under-voltage protective module 61, built-in power module 62, reference voltage module 63, driver output module 64, Logic control module 65, oscillator 66, overcurrent protection 67, overvoltage protection 68, PWM comparator 69, lead-edge-blanking module 71 and line detecting voltage and compensating module 72, described under-voltage protective module 61 and built-in power module 62 all with power pins V
ccbe electrically connected, described built-in power module 62 is also electrically connected with described reference voltage module 63, described reference voltage module 63 is also electrically connected with overcurrent protection 67 and overvoltage protection 68 respectively, described lead-edge-blanking module 71 respectively with detection signal input pin CS, overcurrent protection 67, and PWM comparator 69 is electrically connected, described PWM comparator 69, overvoltage protection 68, and line detecting voltage and compensating module 72 are all electrically connected with feedback pin FB, described line detecting voltage and compensating module 72 also respectively with described oscillator 66, control output pin OUT, built-in power module 62, and detection signal input pin CS is electrically connected, described Logic control module 65 respectively with oscillator 66, overvoltage protection 68, PWM comparator 69, overcurrent protection 67, and driver output module 64 is electrically connected, described driver output module 64 is also electrically connected with described control output pin OUT.
Described inverse-excitation type AC-DC converter also comprises: the first resistance R1 and first is to the 3rd electric capacity C1, C2, C3; Described first resistance R1 one end is electrically connected with the first transistor Q1, detection signal input pin CS respectively, and the other end and ground wire are electrically connected; Described first electric capacity C1 one end and rectification unit 54 are electrically connected, and the other end and ground wire are electrically connected; Described second electric capacity C2 one end and power pins V
ccbe electrically connected, the other end and ground wire are electrically connected; Described 3rd electric capacity C3 and load incoming end 59 are connected in parallel.
Described transformer 56 comprises: former limit N
p, secondary N
sand auxiliary winding N
a, described secondary N
sfor powering load, described auxiliary winding N
apower for giving AC-DC control chip 60.
Described feedback module 58 comprises optocoupler VL, the first operational amplifier U and second to the 4th resistance R2, R3, R4; The other end of described second resistance R2 one end and the second diode D2, load incoming end 59 is electrically connected, and the other end and optocoupler VL are electrically connected; Described 3rd resistance R3 one end and the second diode D2, load incoming end 59 are electrically connected, and one end of the other end and the 4th resistance R4 is electrically connected, and the other end and the load incoming end 59 of described 4th resistance R4 are electrically connected; Described first operational amplifier U is electrically connected with one end of the 4th resistance R4, the other end of the 4th resistance R4 and optocoupler VL respectively; Described optocoupler VL is also electrically connected with feedback pin FB, ground wire respectively.
Described the first transistor Q1 has first grid g1, the first drain electrode d1 and the first source electrode s1, described first grid g1 and described control output pin OUT is electrically connected, described first source electrode s1 and transformer 56 are electrically connected, and described first drain electrode d1 is electrically connected with one end of the first resistance R1 and detection signal input pin CS respectively.
Refer to Fig. 3 and Fig. 4, described line detecting voltage and compensating module 72 comprise: sampled signal generation module 82, first K switch 1, second switch K2, second operational amplifier EA1, 3rd operational amplifier EA2, transistor seconds Q2, third transistor Q3, 5th resistance R5 and the 6th resistance R6, described second operational amplifier EA1 have the first positive input pin+, first negative input pin-and the first output pin, described 3rd operational amplifier EA2 have the second positive input pin+, second negative input pin-and the second output pin, described transistor seconds Q2 has second grid g2, second drain electrode d2 and the second source electrode s2, described third transistor Q3 have the 3rd grid g3, 3rd drain electrode d3 and the 3rd source electrode s3, described sampled signal module 82 respectively with control output pin OUT, first K switch 1, and second switch K2 is electrically connected, described first K switch 1 also respectively with described detection signal input pin CS, one end of 4th electric capacity C4, first negative input pin-electric connection, described second switch K2 also respectively with detection signal input pin CS, one end of 5th electric capacity C5, second positive input pin+electric connection, described first positive input pin+with one end of the 5th resistance R5, second drain electrode d2 is electrically connected, the other end of described 5th resistance R5 and the second negative input pin-, second output pin is electrically connected, described first output pin and second, 3rd grid g2, g3 is electrically connected, described second source electrode s2, 3rd source electrode s3 is all electrically connected with built-in power module 62, described 3rd drain electrode d3 and oscillator 66, one end of 6th resistance R6 is electrically connected, and the other end and the feedback pin FB of described 6th resistance R6 are electrically connected, the other end of described 4th electric capacity C4, the other end of the 5th electric capacity C5 is all electrically connected with ground wire.The sampled signal S1 that described sampled signal generation module 82 exports and S2 is respectively used to control first K switch 1 and second switch K2.The 3rd drain electrode d3 of described third transistor Q3 as the output of line detecting voltage and compensating module 72, for controlling oscillator 66, to realize linear frequency reducing.
Described sampled signal generation module 82 is for controlling the delayed t of control signal on output pin OUT
lEBproduce the sampled signal S1 of narrower in width after time, and time of delay fixing after sampled signal S1 sends sends sampled signal S2 after Δ t, t
lEBtime is used for the former limit N of filtering
pthe spike burr of firm start-up time peak current detection signal (CS), the voltage of peak current detection signal during in order to guarantee to sample former limit conducting, the former limit N that sampled signal S1 and S2 must set at AC-DC control chip 60
psend in the shortest ON time.Such two sampled signals only poor CS2-CS1=[(V
in/ L
p) * Δ t]/R
cs, wherein V
infor the line voltage after rectification, L
pfor the former limit sensibility reciprocal of transformer, R
csfor the resistance of current sense first resistance R1.The electric current then flowing through the 5th resistance R5 equals the electric current flowing through transistor seconds Q2, its current value I0=(CS2-CS1)/R1, then I1=K*I0=K* (CS2-CS1)/R1, then FB1=FB+K*I0=FB+K* (CS2-CS1) * R2/R1=FB+ [K* (V
in/ L
p) * Δ t*R2]/(R1*R
cs).In the description of background technology, we know, under identical load, and line voltage V
inhigher, the voltage of feedback signal is less, and superposition item [K* (V here
in/ L
p) * Δ t*R2]/(R1*R
cs) with line voltage V
inincrease and increase, therefore by appropriate design to K and R1, R2, we can keep FB1 not with line voltage V under identical load
inchange and change, then starting point and the slope of control linear frequency reducing is come with compensated signal (FB1), to realize in wide input voltage range (85-264V), the slope that system starts the POL and frequency reducing curve (F-Po) entering frequency reducing all keeps identical, thus while raising conversion efficiency, obtain best electromagnetic interference performance.
In sum, the invention provides a kind of inverse-excitation type AC-DC converter, by detecting the line voltage of linear frequency reducing, be superimposed on FB signal to produce a compensation rate changed with line change in voltage, make in wide input voltage range (85-264V), the slope that system starts the POL and frequency reducing curve (F-Po) entering frequency reducing all keeps identical, thus while raising conversion efficiency, obtains best electromagnetic interference performance.
These are only preferred embodiment of the present invention, be not limited to the present invention, all any amendments done within the spirit and principles in the present invention, equivalent replacement and improvement etc., all should be included within protection scope of the present invention.
Claims (6)
1. an inverse-excitation type AC-DC converter, is characterized in that, comprising: alternating current input, rectification unit, transformer, the first to the second diode, AC-DC control chip, feedback module, the first transistor and load incoming end, described AC-DC control chip has power pins, control output pin, detection signal input pin, feedback pin and earth connection pin, described rectification unit and described alternating current input are electrically connected, described transformer respectively with described rectification unit, one end of first diode, one end of second diode, the first transistor, and load incoming end is electrically connected, the other end and the described load incoming end of described second diode are electrically connected, and the other end of described power pins and the first diode is electrically connected, described control output pin, detection signal input pin is electrically connected with the first transistor respectively, and described feedback pin and feedback module are electrically connected, and described feedback module is also electrically connected with described load incoming end, described rectification unit, transformer, the earth connection pin of AC-DC control chip, feedback module, and the first transistor is all electrically connected with ground wire,
Described AC-DC control chip comprises: under-voltage protective module, built-in power module, reference voltage module, driver output module, Logic control module, oscillator, overcurrent protection, overvoltage protection, PWM comparator, lead-edge-blanking module and line detecting voltage and compensating module, described under-voltage protective module and built-in power module are all electrically connected with power pins, described built-in power module is also electrically connected with described reference voltage module, described reference voltage module is also electrically connected with overcurrent protection and overvoltage protection respectively, described lead-edge-blanking respectively with detection signal input pin, overcurrent protection, and PWM comparator is electrically connected, described PWM comparator, overvoltage protection, and line detecting voltage and compensating module are all electrically connected with feedback pin, described line detecting voltage and compensating module also respectively with described oscillator, control output pin, built-in power module, the other end of the second diode and detection signal input pin are electrically connected, described Logic control module respectively with oscillator, overvoltage protection, PWM comparator, overcurrent protection, and driver output module is electrically connected, described driver output module is also electrically connected with described control output pin.
2. inverse-excitation type AC-DC converter according to claim 1, is characterized in that, also comprise: the first resistance and the first to the 3rd electric capacity; Described first resistance one end is electrically connected with the first transistor, detection signal input pin respectively, and the other end and ground wire are electrically connected; Described first electric capacity one end and rectification unit are electrically connected, and the other end and ground wire are electrically connected; Described second electric capacity one end and power pins are electrically connected, and the other end and ground wire are electrically connected; Described 3rd electric capacity and load incoming end are connected in parallel.
3. inverse-excitation type AC-DC converter according to claim 1, is characterized in that, described transformer comprises: former limit, secondary and auxiliary winding, and described secondary is used for powering load, and described auxiliary winding is used for powering to AC-DC control chip.
4. inverse-excitation type AC-DC converter according to claim 1, is characterized in that, described feedback module comprises optocoupler, the first operational amplifier and the second to the 4th resistance; The other end, the load incoming end of described second resistance one end and the second diode are electrically connected, and the other end and optocoupler are electrically connected; The other end, the load incoming end of described 3rd resistance one end and the second diode are electrically connected, and one end of the other end and the 4th resistance is electrically connected, and the other end and the load incoming end of described 4th resistance are electrically connected; Described first operational amplifier is electrically connected with one end of the 4th resistance, the other end of the 4th resistance and optocoupler respectively; Described optocoupler is also electrically connected with feedback pin, ground wire respectively.
5. inverse-excitation type AC-DC converter according to claim 2, it is characterized in that, described the first transistor has first grid, the first drain electrode and the first source electrode, described first grid and described control output pin are electrically connected, described first source electrode and transformer are electrically connected, and described first drain electrode is electrically connected with one end of the first resistance and detection signal input pin respectively.
6. inverse-excitation type AC-DC converter according to claim 1, is characterized in that, described line detecting voltage and compensating module comprise: sampled signal generation module, first switch, second switch, second operational amplifier, 3rd operational amplifier, transistor seconds, third transistor, 5th resistance and the 6th resistance, described second operational amplifier has the first positive input pin, first negative input pin and the first output pin, described 3rd operational amplifier has the second positive input pin, second negative input pin and the second output pin, described transistor seconds has second grid, second drain electrode and the second source electrode, described third transistor has the 3rd grid, 3rd drain electrode and the 3rd source electrode, described sampled signal module respectively with control output pin, first switch, and second switch be electrically connected, described first switch also respectively with described detection signal input pin, one end of 4th electric capacity, first negative input pin be electrically connected, described second switch also respectively with detection signal input pin, one end of 5th electric capacity, second positive input pin is electrically connected, one end of described first positive input pin and the 5th resistance, second drain electrode is electrically connected, the other end of described 5th resistance and the second negative input pin, second output pin is electrically connected, described first output pin and second, 3rd grid is electrically connected, described second source electrode, 3rd source electrode is all electrically connected with built-in power module, described 3rd drain electrode and oscillator, one end of 6th resistance is electrically connected, and the other end and the feedback pin of described 6th resistance are electrically connected, the other end of described 4th electric capacity, the other end of the 5th electric capacity is all electrically connected with ground wire.
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| CN112803773A (en) * | 2021-01-28 | 2021-05-14 | 深圳市稳先微电子有限公司 | Control method of PSR flyback switching power supply, secondary side controller device and switching power supply |
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