CN110098750B - Current delay compensation structure for primary side control - Google Patents
Current delay compensation structure for primary side control Download PDFInfo
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- CN110098750B CN110098750B CN201910062202.1A CN201910062202A CN110098750B CN 110098750 B CN110098750 B CN 110098750B CN 201910062202 A CN201910062202 A CN 201910062202A CN 110098750 B CN110098750 B CN 110098750B
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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
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Abstract
The invention discloses a current delay compensation structure for primary side control, which comprises: a primary side sampling resistor; a primary side control switch; a first comparison module; the second comparison module is used for comparing the actual voltage at two ends of the primary side sampling resistor with a second voltage threshold; the third comparison module is used for comparing the actual voltage at two ends of the primary side sampling resistor with the first voltage threshold; a negation module; and the control module is respectively connected with the first comparison module, the second comparison module, the third comparison module and the negation module and is used for adjusting the preset voltage according to the comparison output result of the second comparison module and the third comparison module. According to the invention, when the primary side control switch is turned off, the actual voltage at two ends of the primary side sampling resistor is always between the first voltage threshold and the second voltage threshold through a time delay compensation mode, so that the actual current peak value of the primary side is kept in a preset range, and the constant current control precision of the rectifier is improved.
Description
Technical Field
The invention belongs to the field of integrated circuits, and particularly relates to a current delay compensation structure for primary side control.
Background
The primary side controlled rectifier has been developed for many years, but the constant current control precision of the primary side controlled rectifier is not ideal all the time. According to the working principle of a primary side control rectifier: io is 0.5 (Np/Ns) Ipk Ton/Tsw, wherein Io is output current, Np is the number of turns of the primary side of the transformer, Ns is the number of turns of the secondary side of the transformer, Ipk is peak current flowing through the primary side of the transformer, Ton is the conduction time of the secondary side rectifier tube, and Tsw is the time of one switching period. As can be seen from the above equation, the peak current flowing through the primary side of the transformer has a direct effect on the constant output current, and thus the constant output current is controlled by controlling the accuracy of the peak current flowing through the primary side of the transformer.
At present, the common method is to detect the peak current of the primary side by detecting the voltage of an external detection resistor. However, because there is a transmission delay in the IC module, the turn-off signal output by the IC module also needs a conversion time when it changes from the high level to the low level, and the MOSFET power switch tube also needs a certain turn-off time when it is turned off, so the total turn-off delay is the sum of the above three delays. This means that after the voltage of the external detection resistor reaches the current limit value, the MOSFET is not turned off immediately, but turned off after a delay, the current in the primary inductor continues to rise, which is larger than the theoretical value. The average value of the output current is related to the current of the primary side, so that the output current also has difference. In order to reduce the error caused by internal delay, a method of performing feedforward compensation on the input voltage can be adopted, most commonly, a resistor with a large resistance value is directly introduced from the input voltage and connected to the current detection resistor, however, the method is high in cost through peripheral compensation, the compensation amount is determined according to the input voltage and an external divider resistor, and under the condition of certain input voltage, the compensation effect is not obtained, and under the condition of other input voltages, the compensation limit is exceeded.
Therefore, a method for improving the accuracy of the constant current control of the rectifier is particularly needed.
Disclosure of Invention
The invention aims to provide a current delay compensation structure for primary side control, which improves the constant current control precision of a rectifier.
In order to achieve the above object, the present invention provides a current delay compensation structure for primary side control, the delay compensation structure comprising:
a primary side sampling resistor;
the primary side control switch is respectively connected with the primary side sampling resistor and the primary side inductor;
the first comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a preset voltage;
the second comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a second voltage threshold value;
the third comparison module is connected with the primary side sampling resistor and is used for comparing the actual voltage at two ends of the primary side sampling resistor with a first voltage threshold value;
the negation taking module is respectively connected with the first comparison module and the primary side control switch;
and the control module is respectively connected with the first comparison module, the second comparison module, the third comparison module and the negation module and is used for adjusting the preset voltage according to the comparison output result of the second comparison module and the third comparison module.
Preferably, when the second voltage threshold is greater than or equal to the actual voltage at the two ends of the primary sampling resistor, the second comparing module outputs a high level, and the control module increases the preset voltage;
when the first voltage threshold is less than or equal to the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a high level, and the control module reduces the preset voltage;
when the second voltage threshold is smaller than the actual voltage at the two ends of the primary sampling resistor, the second comparison module outputs a low level, when the first voltage threshold is larger than the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a low level, and the control module maintains the preset voltage.
Preferably, the control module gradually increases or decreases the preset voltage according to a preset step length.
Preferably, the primary side control switch is a MOSFET power tube.
Preferably, the drain of the primary side control switch is connected to the primary side inductor, the source of the primary side control switch is connected to one end of the primary side sampling resistor, and the other end of the primary side sampling resistor is grounded.
Preferably, a positive input end of the first comparing module is connected to one end of the primary side sampling resistor connected to the gate of the primary side control switch, a negative input end of the first comparing module is connected to an output end of the control module, an output end of the first comparing module is connected to an input end of the negating module, and an output end of the negating module is connected to the control module and the gate of the primary side control switch respectively;
the negative input end of the second comparison module is connected with one end of the primary sampling resistor connected with the grid of the primary control switch, the voltage of the positive input end of the second comparison module is a second voltage threshold, and the output end of the second comparison module is connected with the control module;
the positive input end of the third comparison module is connected with one end of the primary sampling resistor connected with the grid of the primary control switch, the voltage of the negative input end of the third comparison module is a first voltage threshold, and the output end of the third comparison module is connected with the control module.
Preferably, the output of the output end of the control module is a preset voltage, and the preset voltage is an expected voltage at two ends of the primary side sampling resistor when the primary side control switch is turned off.
Preferably, the first voltage threshold is higher than the second voltage threshold.
Preferably, the control module is a bidirectional adder.
Preferably, the first comparison module, the second comparison module and the third comparison module are comparators.
The invention has the beneficial effects that: according to the invention, a primary side sampling resistor, a primary side control switch and a primary side inductor are connected in series, the detection of the actual current peak value of the primary side is realized by acquiring the actual voltage at two ends of the primary side sampling resistor, a second comparison module and a third comparison module respectively compare the actual voltage at two ends of the primary side sampling resistor with the corresponding voltage threshold value, a control module adjusts the preset voltage according to the comparison output result of the second comparison module and the third comparison module, and the actual voltage at two ends of the primary side sampling resistor is ensured to be always between the first voltage threshold value and the second voltage threshold value in a time delay compensation mode, so that the actual current peak value of the primary side is kept in the preset range, and the precision of the constant current control of the rectifier.
The system of the present invention has other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings. Wherein like reference numerals generally refer to like parts throughout the exemplary embodiments of the invention.
Fig. 1 shows a schematic connection diagram of a current delay compensation arrangement for primary control according to the invention.
Fig. 2 shows a schematic diagram of the delay induced current peak difference of a current delay compensation structure for primary side control according to the present invention.
Fig. 3a shows a schematic diagram of a current delay compensation structure for primary control according to the present invention, in which the first voltage threshold is greater than the actual voltage across the sampling resistor on the primary side.
Fig. 3b shows a schematic diagram of a current delay compensation structure for primary control according to the present invention after the first voltage threshold is larger than the actual voltage adjustment across the sampling resistor of the primary side.
Fig. 3c shows a schematic diagram of a current delay compensation structure for primary control according to the present invention, in which the second voltage threshold is greater than the actual voltage across the primary sampling resistor.
Fig. 3d shows a schematic diagram of a current delay compensation structure for primary side control according to the present invention after the second voltage threshold is larger than the actual voltage adjustment across the sampling resistor of the primary side.
Description of reference numerals:
l1, primary side inductance; m0, a primary side control switch; rs, a primary side sampling resistor; COMP3, a third comparison module; COMP2, a second comparison module; COMP1, a first comparison module; u1, a control module; u2 and an inverting module; td, delay time; VC, a preset voltage; v1, first voltage threshold; v1, second voltage threshold.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
The current delay compensation structure for the primary side control comprises the following components:
a primary side sampling resistor;
the primary side control switch is respectively connected with the primary side sampling resistor and the primary side inductor;
the first comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a preset voltage;
the second comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a second voltage threshold;
the third comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with the first voltage threshold;
the negation taking module is respectively connected with the first comparison module and the primary side control switch;
and the control module is respectively connected with the first comparison module, the second comparison module, the third comparison module and the negation module and is used for adjusting the preset voltage according to the comparison output result of the second comparison module and the third comparison module.
Specifically, due to the time delay of the primary side control switch, the internal time delay of the IC module and other reasons, the sampling current acquired when the primary side control switch is turned off is not the actual current peak value of the primary side, so that the time delay compensation method is adopted, the primary side sampling resistor, the primary side control switch and the primary side inductor are connected in series, the detection of the actual current peak value of the primary side is realized by acquiring the actual voltage at two ends of the primary side sampling resistor, the second comparison module compares the actual voltage at two ends of the primary side sampling resistor with the second voltage threshold, the third comparison module compares the actual voltage at two ends of the primary side sampling resistor with the first voltage threshold, and the control module adjusts the preset voltage according to the comparison output result of the second comparison module and the third comparison module, thereby ensuring that the preset voltage is consistently between the first voltage threshold and the second.
According to the current delay compensation structure for primary side control in the exemplary embodiment, the actual voltage at two ends of the primary side sampling resistor is compared with the corresponding voltage threshold value, the preset voltage is adjusted according to the comparison output result, and the actual voltage at two ends of the primary side sampling resistor is ensured to be always between the first voltage threshold value and the second voltage threshold value through the delay compensation mode, so that the actual current peak value of the primary side is kept in the preset range, and the precision of the constant current control of the rectifier is improved.
As a preferred scheme, when the second voltage threshold is greater than or equal to the actual voltage at the two ends of the primary sampling resistor, the second comparison module outputs a high level, and the control module increases the preset voltage;
when the first voltage threshold is smaller than or equal to the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a high level, and the control module reduces the preset voltage;
when the second voltage threshold is smaller than the actual voltage at the two ends of the primary sampling resistor, the second comparison module outputs a low level, and when the first voltage threshold is larger than the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a low level, and the control module keeps a preset voltage.
Specifically, when the second voltage threshold is greater than or equal to the actual voltage at the two ends of the primary sampling resistor, the second comparison module outputs a high level, and the control module increases the preset voltage according to a high level signal output by the second comparison module; when the first voltage threshold is smaller than or equal to the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a high level, and the control module reduces the preset voltage according to a high level signal output by the third comparison module; when the second voltage threshold is smaller than the actual voltage at the two ends of the primary side sampling resistor, the second comparison module outputs a low level, when the first voltage threshold is larger than the actual voltage at the two ends of the primary side sampling resistor, the third comparison module outputs a low level, the control module keeps a preset voltage according to the low levels output by the second comparison module and the third comparison module, and the actual voltage at the two ends of the primary side sampling resistor is always between the first voltage threshold and the second voltage threshold, so that the actual current peak value of the primary side is kept in a stable preset range.
Preferably, the control module gradually increases or decreases the preset voltage according to a preset step length.
Specifically, the preset voltage is gradually increased or decreased according to the preset step length, if the step length of the addition and subtraction of the preset voltage is large, and the return difference between the first voltage threshold and the second voltage threshold is small, the output signal of the second comparison module and the output signal of the third comparison module may alternately have high and low levels, so that the level of the preset voltage cannot reach a stable value, and although the final current average value (precision) is not influenced within the set range, the step length of the addition and subtraction of the preset voltage influences the precision. Therefore, the preset voltage is gradually increased or decreased according to the preset step length, and the control precision is further improved.
Preferably, the primary side control switch is a MOSFET power tube.
According to the preferable scheme, the drain electrode of the primary side control switch is connected with the primary side inductor, the source electrode of the primary side control switch is connected with one end of the primary side sampling resistor, and the other end of the primary side sampling resistor is grounded.
Specifically, a primary side sampling resistor, a primary side control switch and a primary side inductor are connected in series, one end of the primary side sampling resistor is grounded, and the detection of the primary side current is realized through the voltage at the two ends of the primary side sampling resistor.
As a preferred scheme, the positive input end of the first comparison module is connected with one end of the primary side sampling resistor connected with the grid electrode of the primary side control switch, the negative input end of the first comparison module is connected with the output end of the control module, the output end of the first comparison module is connected with the input end of the negation module, and the output end of the negation module is respectively connected with the control module and the grid electrode of the primary side control switch;
the negative input end of the second comparison module is connected with one end of the primary side sampling resistor connected with the grid electrode of the primary side control switch, the voltage of the positive input end of the second comparison module is a second voltage threshold value, and the output end of the second comparison module is connected with the control module;
the positive input end of the third comparison module is connected with one end of the primary sampling resistor connected with the grid of the primary control switch, the voltage of the negative input end of the third comparison module is a first voltage threshold, and the output end of the third comparison module is connected with the control module.
Specifically, when the power supply is firstly carried out, the first comparison module compares the actual voltage at two ends of the primary sampling resistor with the preset voltage, the voltage at two ends of the primary sampling resistor is zero, the voltage at two ends of the primary sampling resistor is smaller than the preset voltage, the first comparison module outputs a low-level signal, the low-level signal is changed into a high-level signal after passing through the negation module, the high-level signal enters the control module, meanwhile, the high-level signal enters the grid electrode of the primary control switch, the primary control switch is closed, the series circuit of the primary sampling resistor is conducted, the first comparison module compares the actual voltage at two ends of the primary sampling resistor with the preset voltage, the voltage at two ends of the primary sampling resistor is larger than the preset voltage, the first comparison module outputs a high-level signal, the high-level signal is changed into a low-level signal after passing through the negation module, and the, meanwhile, the low level signal enters a grid electrode of the primary side control switch, the primary side control switch is turned off, the second comparison module compares the actual voltage at two ends of the primary side sampling resistor with a second voltage threshold value, the third comparison module compares the actual voltage at two ends of the primary side sampling resistor with the first voltage threshold value, when the second voltage threshold value is larger than or equal to the actual voltage at two ends of the primary side sampling resistor, the second comparison module outputs a high level signal, the control module increases the preset voltage, and when the first voltage threshold value is smaller than or equal to the actual voltage at two ends of the primary side sampling resistor, the third comparison module outputs a high level signal, and the control module decreases the preset voltage; when the second voltage threshold is smaller than the actual voltage at two ends of the primary side sampling resistor, the second comparison module outputs a low level, and when the first voltage threshold is larger than the actual voltage at two ends of the primary side sampling resistor, the third comparison module outputs a low level, the control module keeps a preset voltage, and the primary side controls a turn-off period result of the switch.
As a preferred scheme, the output of the output end of the control module is a preset voltage, and the preset voltage is an expected voltage at two ends of the primary side sampling resistor when the primary side control switch is turned off.
Specifically, the voltage output by the output end of the control module is a preset voltage, and the preset voltage is a voltage value expected to be reached by two ends of the primary side sampling resistor when the primary side control switch is turned off.
Preferably, the first voltage threshold is higher than the second voltage threshold.
Preferably, the control module is a bidirectional adder.
Preferably, the first comparison module, the second comparison module and the third comparison module are comparators.
Example one
Fig. 1 shows a schematic connection diagram of a current delay compensation arrangement for primary control according to the invention. Fig. 2 shows a schematic diagram of the delay induced current peak difference of a current delay compensation structure for primary side control according to the present invention.
Referring to fig. 1 and 2, the current delay compensation structure for primary side control includes:
a primary side sampling resistor Rs;
the primary side control switch M0 and the primary side control switch M0 are respectively connected with the primary side sampling resistor Rs and the primary side inductor L1;
the first comparison module COMP1 is connected with the primary side sampling resistor Rs, and is used for comparing the actual voltage at two ends of the primary side sampling resistor Rs with a preset voltage VC;
the first comparison module COMP2 is connected with the primary side sampling resistor Rs and used for comparing the actual voltage of the primary side sampling resistor Rs with a second voltage threshold value V2;
the third comparing module COMP3, the third comparing module COMP3 is connected to the primary side sampling resistor Rs, and is configured to compare an actual voltage at two ends of the primary side sampling resistor Rs with the first voltage threshold V1;
the inverting module U2 is connected with the inverting module U2 and the first comparison module COMP1 and the primary side control switch M0 respectively;
the control module U1 and the control module U1 are respectively connected to the first comparison module COMP1, the second comparison module COMP2, the third comparison module COMP3 and the negation module U2, and are configured to adjust the preset voltage VC according to comparison output results of the second comparison module COMP2 and the third comparison module COMP 3.
When the second voltage threshold V2 is greater than or equal to the actual voltage at the two ends of the primary sampling resistor Rs, the second comparison module COMP2 outputs a high level, and the control module U1 increases the preset voltage VC;
when the first voltage threshold V1 is less than or equal to the actual voltage of the primary sampling resistor Rs, the third comparison module COMP3 outputs a high level, and the control module U1 decreases the preset voltage VC;
when the second voltage threshold V2 is smaller than the actual voltage at the two ends of the primary sampling resistor Rs, the second comparison module COMP2 outputs a low level, and when the first voltage threshold V1 is larger than the actual voltage at the two ends of the primary sampling resistor Rs, the third comparison module COMP3 outputs a low level, and the control module U1 maintains the preset voltage VC.
The control module U1 gradually increases or decreases the preset voltage VC according to a preset step.
The primary side control switch M0 is a MOSFET power tube.
The drain of the primary side control switch M0 is connected to the primary side inductor L1, the source of the primary side control switch M0 is connected to one end of the primary side sampling resistor Rs, and the other end of the primary side sampling resistor Rs is grounded.
The positive electrode input end of the first comparison module COMP1 is connected with one end, connected with the primary side sampling resistor Rs and the grid electrode of the primary side control switch M0, of the first comparison module COMP1, the negative electrode input end of the first comparison module COMP1 is connected with the output end of the control module U1, the output end of the first comparison module COMP1 is connected with the input end of the negation module U2, and the output end of the negation module U2 is connected with the grid electrodes of the control module U1 and the primary side control switch M0 respectively;
a negative electrode input end of the second comparison module COMP2 is connected with one end, connected with the primary side sampling resistor Rs and the gate of the primary side control switch M0, of the second comparison module COMP2, the voltage of the positive electrode input end of the second comparison module COMP2 is a second voltage threshold value V2, and the output end of the second comparison module COMP2 is connected with the control module U1;
the positive electrode input end of the third comparison module COMP3 is connected to one end of the primary side sampling resistor Rs connected to the gate of the primary side control switch M0, the voltage at the negative electrode input end of the third comparison module COMP3 is a first voltage threshold V1, and the output end of the third comparison module COMP3 is connected to the control module U1.
The output of the output end of the control module U1 is a preset voltage VC, which is an expected voltage across the primary side sampling resistor Rs when the primary side control switch M0 is turned off.
Wherein the first voltage threshold V1 is higher than the second voltage threshold V2.
The control module U1 is a bidirectional adder.
The first comparison module COMP1, the second comparison module COMP2, and the third comparison module COMP3 are comparators.
Fig. 3a shows a schematic diagram of a current delay compensation structure for primary control according to the present invention, in which the first voltage threshold is greater than the actual voltage across the sampling resistor on the primary side. Fig. 3b shows a schematic diagram of a current delay compensation structure for primary control according to the present invention after the first voltage threshold is larger than the actual voltage adjustment across the sampling resistor of the primary side. Fig. 3c shows a schematic diagram of a current delay compensation structure for primary control according to the present invention, in which the second voltage threshold is greater than the actual voltage across the primary sampling resistor. Fig. 3d shows a schematic diagram of a current delay compensation structure for primary side control according to the present invention after the second voltage threshold is larger than the actual voltage adjustment across the sampling resistor of the primary side.
As shown in fig. 3a, when the first voltage threshold V1 is greater than the actual voltage across the primary sampling resistor Rs, the preset voltage VC is decreased such that the actual voltage across the primary sampling resistor Rs is between the first voltage threshold V1 and the second voltage threshold V2, as shown in fig. 3b, and when the second voltage threshold V2 is greater than the actual voltage across the primary sampling resistor Rs, as shown in fig. 3c, the preset voltage VC is increased such that the actual voltage across the primary sampling resistor Rs is between the first voltage threshold V1 and the second voltage threshold V2, as shown in fig. 3 d.
The working process of the current delay compensation structure for primary side control is as follows: when the power-on is carried out for the first time, the first comparison module COMP1 compares the actual voltage at two ends of the primary sampling resistor Rs with the preset voltage VC, the voltage at two ends of the primary sampling resistor Rs is zero, the voltage at two ends of the primary sampling resistor Rs is smaller than the preset voltage VC, the first comparison module COMP1 outputs a low-level signal, the low-level signal is changed into a high-level signal after passing through the negation module U2, the high-level signal enters the control module U1, meanwhile, the high-level signal enters the grid electrode of the primary control switch M0, so that the primary control switch M0 is closed, the series circuit of the primary sampling resistor Rs is conducted, the first comparison module COMP1 compares the actual voltage at two ends of the primary sampling resistor Rs with the preset voltage VC, the voltage at two ends of the primary sampling resistor Rs is larger than the preset voltage VC, the first comparison module COMP1 outputs a high-level signal, the high-level signal is changed into a low-, the low-level signal enters a control module U1, meanwhile, the low-level signal enters a grid electrode of a primary side control switch M0, the primary side control switch M0 is turned off, a second comparison module COMP2 compares actual voltages at two ends of a primary side sampling resistor Rs with a second voltage threshold value V2, a third comparison module COMP3 compares the actual voltages at two ends of the primary side sampling resistor Rs with a first voltage threshold value V1, when the second voltage threshold value V2 is larger than or equal to the actual voltages at two ends of the primary side sampling resistor Rs, the second comparison module COMP2 outputs a high-level signal, a control module U1 increases a preset voltage VC, and when the first voltage threshold value V1 is smaller than or equal to the actual voltages at two ends of the primary side sampling resistor Rs, the third comparison module COMP3 outputs a high level, and the control module U1 decreases the preset voltage VC; when the second voltage threshold V2 is smaller than the actual voltage at the two ends of the primary side sampling resistor Rs, the second comparison module COMP2 outputs a low level, and when the first voltage threshold V1 is larger than the actual voltage at the two ends of the primary side sampling resistor Rs, the third comparison module COMP3 outputs a low level, the control module U1 keeps the preset voltage VC, and the primary side control switch M0 controls a turn-off period result.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the illustrated embodiments.
Claims (9)
1. A current delay compensation structure for primary side control, said delay compensation structure comprising:
a primary side sampling resistor;
the primary side control switch is respectively connected with the primary side sampling resistor and the primary side inductor;
the first comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a preset voltage;
the second comparison module is connected with the primary side sampling resistor and used for comparing the actual voltage at two ends of the primary side sampling resistor with a second voltage threshold value;
the third comparison module is connected with the primary side sampling resistor and is used for comparing the actual voltage at two ends of the primary side sampling resistor with a first voltage threshold value;
the negation taking module is respectively connected with the first comparison module and the primary side control switch;
the control module is respectively connected with the first comparison module, the second comparison module, the third comparison module and the negation module and is used for adjusting the preset voltage according to the comparison output result of the second comparison module and the third comparison module;
when the second voltage threshold is greater than or equal to the actual voltage at the two ends of the primary side sampling resistor, the second comparison module outputs a high level, and the control module increases the preset voltage;
when the first voltage threshold is less than or equal to the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a high level, and the control module reduces the preset voltage;
when the second voltage threshold is smaller than the actual voltage at the two ends of the primary sampling resistor, the second comparison module outputs a low level, when the first voltage threshold is larger than the actual voltage at the two ends of the primary sampling resistor, the third comparison module outputs a low level, and the control module maintains the preset voltage.
2. The current delay compensation structure for a primary side control of claim 1, wherein the control module gradually increases or decreases the preset voltage by a preset step size.
3. The current delay compensation structure for a primary control of claim 1, wherein said primary control switch is a MOSFET power tube.
4. The current delay compensation structure for a primary side control according to claim 3, wherein a drain of the primary side control switch is connected to the primary side inductor, a source of the primary side control switch is connected to one end of the primary side sampling resistor, and another end of the primary side sampling resistor is grounded.
5. The current delay compensation structure for the primary side control according to claim 1, wherein a positive input terminal of the first comparing module is connected to one end of the primary side sampling resistor connected to the gate of the primary side control switch, a negative input terminal of the first comparing module is connected to an output terminal of the control module, an output terminal of the first comparing module is connected to an input terminal of the negating module, and output terminals of the negating module are connected to the control module and the gate of the primary side control switch, respectively;
the negative input end of the second comparison module is connected with one end of the primary sampling resistor connected with the grid of the primary control switch, the voltage of the positive input end of the second comparison module is a second voltage threshold, and the output end of the second comparison module is connected with the control module;
the positive input end of the third comparison module is connected with one end of the primary sampling resistor connected with the grid of the primary control switch, the voltage of the negative input end of the third comparison module is a first voltage threshold, and the output end of the third comparison module is connected with the control module.
6. The current delay compensation structure for a primary side control according to claim 1, wherein the output of the output terminal of the control module is a preset voltage, and the preset voltage is an expected voltage across the primary side sampling resistor when the primary side control switch is turned off.
7. The current delay compensation structure for a primary control of claim 1, wherein said first voltage threshold is higher than said second voltage threshold.
8. The current delay compensation structure for a primary control of claim 1, wherein said control module is a bidirectional adder.
9. The current delay compensation structure for a primary side control of claim 1, wherein the first comparing module, the second comparing module and the third comparing module are comparators.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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