CN112448370A - Primary side control circuit and control method and isolated power supply conversion circuit - Google Patents
Primary side control circuit and control method and isolated power supply conversion circuit Download PDFInfo
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- CN112448370A CN112448370A CN201910830593.7A CN201910830593A CN112448370A CN 112448370 A CN112448370 A CN 112448370A CN 201910830593 A CN201910830593 A CN 201910830593A CN 112448370 A CN112448370 A CN 112448370A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
- H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
- H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
- G01R19/17—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values giving an indication of the number of times this occurs, i.e. multi-channel analysers
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses a primary side control circuit and a control method for an isolated power conversion circuit and the isolated power conversion circuit. The control circuit comprises a decision circuit and a drive circuit. The decision circuit is used for receiving the detection voltage representing the bus voltage and outputting a control command according to the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; and counting the number of time intervals with the detection voltage larger than a set voltage threshold value in at least two continuously set time intervals, and when the count reaches the set threshold value, sending a control command for controlling the primary circuit to be in an open circuit state to a decision circuit so as to realize overvoltage protection. The driving circuit is used for controlling the conduction state of the primary side circuit according to the control command of the decision circuit. The primary side control circuit and the control method for the isolated power conversion circuit and the isolated power conversion circuit can reduce the standby power consumption of a system and improve the detection precision.
Description
Technical Field
The invention belongs to the technical field of electronic circuits, and particularly relates to a primary side control circuit and a control method for an isolated power conversion circuit and the isolated power conversion circuit.
Background
Along with the increasing importance of various countries in the world on energy problems, the energy consumption problem of electronic power supply products is more and more prominent, and how to improve the efficiency of the power supply products becomes a problem to be solved urgently. Compared with a linear voltage-stabilized power supply, the switching power supply has the characteristics of high efficiency, small volume, light weight and wide application, and is a mainstream product of the voltage-stabilized power supply.
In the world, about 4/5 countries use 220V ac voltage, but some countries, such as the united states and japan, use 110V ac voltage. The stability of the network voltage is also different, and the instantaneous peak value of the network voltage of some countries can even reach more than 300V, which puts high requirements on the reliability of the switching power supply. Accordingly, a bus voltage overvoltage protection function needs to be added to the switching power supply product. However, the traditional bus voltage overvoltage protection function has two problems: firstly, the bus voltage overvoltage protection function is added, meanwhile, the standby power consumption is also increased, and the material cost is correspondingly increased; secondly, the precision of the detection voltage is not high.
The conventional method for judging the overvoltage of the bus voltage Vbus is shown in fig. 1, and the bus voltage Vbus value is obtained by adding sampling divider resistors R3 and R4, and then whether the bus voltage is overvoltage or not is judged after time delay and jitter removal. Because the R3 and R4 path resistance voltage division circuits are added, the standby power consumption and the material cost of the system are also increased.
Because the OVP protection needs to be prevented from being judged by mistake in the lightning surge test, the traditional time delay and jitter removal time is generally set to be more than 50ms, so that the traditional detection mode has a defect that the detection voltage has larger deviation when the load size is changed. As shown in fig. 2, during heavy loading, the steamed bun wave Va1 is a waveform obtained by full-wave rectification of alternating current, and Vbus1 is a waveform obtained by filtering Va 1. During light load, the steamed bread wave Va2 is a waveform obtained after alternating current full-wave rectification, and the Vbus2 is a waveform obtained after Va2 filtering. The threshold voltage of the bus voltage Vbus1 is determined to be Vovp1 at heavy load, and the threshold voltage of the bus voltage Vbus2 is determined to be Vovp2 at light load. The prior art is to perform overvoltage detection by directly delaying and eliminating jitter for 128ms, that is, the minimum value of the whole bus voltage is larger than Vovp, and if Vovp is 400V, the bus voltage Vbus at overvoltage is 400V + Vripple, and the bus voltage at overvoltage is related to Vripple. Since the ripple Vripple1 of the bus voltage at heavy load is much larger than the ripple Vripple2 of the bus voltage at light load, this results in Vbus1 being much larger than Vbus 2.
It can be seen that the disadvantages of the prior art include: 1) a voltage dividing resistor for sampling the voltage of a single bus is needed, so that the standby power consumption and the material cost of the system are increased; 2) the bus voltage detection accuracy is not high, and the detection voltage has large deviation along with the change of the load size.
In view of the above, there is a need to design a switching power supply circuit to overcome the above-mentioned drawbacks of the conventional switching power supply circuit.
Disclosure of Invention
The invention provides a primary side control circuit and a control method for an isolated power conversion circuit and the isolated power conversion circuit, which can reduce the standby power consumption of a system and improve the detection precision.
In order to solve the technical problem, according to one aspect of the present invention, the following technical solutions are adopted:
a primary side control circuit for an isolated power conversion circuit, the primary side control circuit comprising an overvoltage protection module, the overvoltage protection module being configured to provide protection to the isolated power conversion circuit when a bus voltage of the isolated power conversion circuit is in overvoltage, the overvoltage protection module comprising:
the judgment circuit is used for receiving detection voltage representing bus voltage and outputting a control command according to the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and when the count reaches the set threshold value, sending a control command for controlling the primary side circuit to be in an open circuit state to a driving circuit by the judgment circuit so as to realize overvoltage protection;
the input end of the driving circuit is coupled with the judgment circuit, and the output end of the driving circuit is coupled with the primary side switch; the driving circuit is used for controlling the conduction state of the primary side circuit according to the control command of the decision circuit.
As an embodiment of the present invention, the decision circuit further includes a time control module, and the time control module is configured to control a time interval of the time interval.
As an embodiment of the present invention, the decision circuit includes:
the comparison circuit is used for comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold value, the comparison circuit outputs a first control signal to an interval control circuit;
an interval control circuit for controlling the time interval of each time interval; if at least one first control signal is received in a time interval, the interval control circuit outputs a second control signal to a counting circuit in a corresponding time interval;
the counting circuit is used for carrying out counting operation when a second control signal sent by the interval control circuit can be received in each time interval; if the count reaches a set threshold value in at least two continuously set time intervals, the counting circuit outputs a third control signal for controlling the primary circuit to be in an open circuit state to the driving circuit; otherwise, the counting circuit resets the counting and waits for counting again.
As an embodiment of the present invention, the decision circuit further includes a delay jitter elimination circuit, an input terminal of the delay jitter elimination circuit is coupled to an output terminal of the comparison circuit, an output terminal of the delay jitter elimination circuit is coupled to an input terminal of the interval control circuit, and the delay jitter elimination circuit is configured to perform a delay jitter elimination process for a duration of a set time on the first control signal when the comparison circuit detects that the detected voltage is greater than the set voltage threshold.
As an embodiment of the present invention, the detection voltage received by the decision circuit is a voltage corresponding to a set voltage-dividing resistor of the auxiliary winding.
As an embodiment of the present invention, the primary side control circuit further includes a voltage conversion circuit, an input terminal of the voltage conversion circuit is coupled to a connection point of the first voltage-dividing resistor and the second voltage-dividing resistor, and an output terminal of the voltage conversion circuit is coupled to the decision circuit; the voltage conversion circuit is used for receiving a set current, converting the received set current into the detection voltage in proportion to the set current, and inputting the detection voltage into the judgment circuit.
As an embodiment of the present invention, the time control module controls a time interval of the time interval to be greater than a period of the bus voltage.
As an embodiment of the present invention, the duration setting time of the delay jitter elimination circuit for delay jitter elimination is 50-300 us.
According to another aspect of the invention, the following technical scheme is adopted: an isolated power conversion circuit comprises a primary side circuit and a secondary side circuit, wherein the primary side circuit comprises a primary side winding, a primary side switch and the primary side control circuit.
As an embodiment of the present invention, the isolated power conversion circuit further includes an auxiliary winding, the auxiliary winding is coupled to a first end of a first voltage-dividing resistor, and a second end of the first voltage-dividing resistor is coupled to a second voltage-dividing resistor and the primary side control circuit, respectively.
According to another aspect of the invention, the following technical scheme is adopted: a control method for providing bus voltage overvoltage protection to an isolated power conversion circuit, the control method comprising:
step S1, the decision circuit outputs a control command according to the received detection voltage representing the bus voltage and the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and sending a control command for controlling the primary circuit to be in an open circuit state when the count reaches the set threshold value;
and step S2, the drive circuit controls the conduction state of the primary side circuit according to the control command.
As an embodiment of the present invention, the step S1 includes:
step S11, comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold, outputting a first control signal;
step S12, controlling the time interval of each time interval; judging whether at least one first control signal is received in each time interval; if at least one first control signal is received in a time interval, outputting a second control signal in the time interval;
step S13, counting operation is carried out when the second control signal can be received in each time interval; if the count reaches a set threshold value in at least two continuously set time intervals, outputting a third control signal for controlling the primary circuit to be in an open circuit state; otherwise, the counting is reset and the counting is waited again.
As an embodiment of the present invention, the step S11 further includes: and when the detected voltage is detected to be larger than a set voltage threshold value, carrying out time delay jitter elimination processing on the first control signal for a set time.
As an embodiment of the present invention, the control method further includes step S0: receiving a set current, and converting the received set current into the detection voltage proportional to the set current.
The invention has the beneficial effects that: the primary side control circuit and the control method for the isolated power conversion circuit and the isolated power conversion circuit can reduce the standby power consumption of a system and improve the overvoltage detection precision of the bus voltage. The invention does not need to additionally increase a sampling divider resistor, saves the material cost and reduces the standby power consumption of the system. The control circuit can improve the overvoltage detection precision of the bus voltage.
Drawings
Fig. 1 is a schematic circuit diagram of a conventional bus voltage overvoltage detection method.
Fig. 2 is a schematic diagram of detecting voltage deviation according to load variation in a conventional bus voltage detection method.
Fig. 3 is a schematic diagram of the components of the primary side control circuit according to an embodiment of the invention.
Fig. 4 is a circuit diagram of an isolated power conversion circuit according to an embodiment of the invention.
Fig. 5 is a schematic diagram of a decision circuit according to an embodiment of the invention.
Fig. 6 is a flowchart of a control method according to an embodiment of the invention.
FIG. 7 is a waveform timing diagram of some signals according to an embodiment of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.
The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. It is within the scope of the present disclosure and protection that the same or similar prior art means and some features of the embodiments may be interchanged.
"coupled" or "connected" in this specification includes both direct and indirect connections, such as through some active device, passive device, or electrically conductive medium; but also may include connections through other active or passive devices, such as through switches, follower circuits, etc., that are known to those skilled in the art for achieving the same or similar functional objectives.
The embodiment of the invention discloses a primary side control circuit for an isolated power supply conversion circuit, which comprises an overvoltage protection module, wherein the overvoltage protection module is used for providing a protection effect on the isolated power supply conversion circuit when the bus voltage of the isolated power supply conversion circuit is in overvoltage, and comprises a judgment circuit and a driving circuit. The judgment circuit is used for receiving detection voltage representing bus voltage and outputting a control command according to the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; and counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and when the count reaches the set threshold value, sending a control command for controlling the primary side circuit to be in an open circuit state to a driving circuit by the judgment circuit so as to realize overvoltage protection. The input end of the driving circuit is coupled with the judgment circuit, and the output end of the driving circuit is coupled with the primary side switch; the driving circuit is used for controlling the conduction state of the primary side circuit according to the control command of the decision circuit. The above-described counting operation is directed to the number of time intervals satisfying the determination condition. That is, when the detected voltage is greater than the set voltage threshold (i.e., the determination condition is satisfied) in a certain time interval, the time interval is counted once. If the detection voltage is larger than the set voltage threshold value for a plurality of times in the time interval, only one count is still performed.
In an embodiment of the present invention, in two time intervals which are set continuously, the two time intervals are a and B, respectively, and the number of the time intervals in which the detection voltage is greater than the set voltage threshold is counted. For example, when the detected voltage is greater than the set voltage threshold once in the time interval a and the detected voltage is greater than the set voltage threshold twice in the time interval B, the count is performed once in the time interval a and once in the time interval B, which is two times in total. If the set threshold value is two times, the counting reaches the set threshold value, so that the judgment circuit sends a control command for controlling the primary circuit to be in an open circuit state to a driving circuit, and overvoltage protection is realized.
The invention can effectively solve the problem of low input overvoltage detection accuracy caused by load change, and through the detection method of at least two continuously set time intervals, as long as the maximum value of the detected voltage is detected to be greater than the set voltage threshold value by the set number of time intervals, the input overvoltage is judged, the input overvoltage is effectively identified, and the misjudgment is avoided. The minimum value of the bus voltage is different from the minimum value of the bus voltage in the prior art, which needs to be larger than the voltage threshold value to be considered as overvoltage, and the influence of ripple waves on overvoltage detection is effectively solved.
FIG. 3 is a schematic diagram of the components of a primary side control circuit according to an embodiment of the present invention; referring to fig. 3, in an embodiment of the present invention, the primary side control circuit 1 includes: a decision circuit 13, a drive circuit 15 (may not include the voltage conversion circuit 11). In another embodiment of the present invention, the control circuit further includes a voltage conversion circuit 11, the voltage conversion circuit 11 is configured to receive the setting current I1, convert the current I1 into a detection voltage V1 proportional thereto, and input the detection voltage V1 to the decision circuit 13.
In an embodiment of the present invention, the decision circuit further includes a time control module, and the time control module is configured to control a time interval of the time interval. In an embodiment of the invention, the time control module controls a time interval of the time interval to be greater than a period of the bus voltage. When the set time interval is too small, even if the bus voltage is overvoltage, the detection voltage is not monitored to be larger than the set voltage threshold value in some time intervals, so that the identification accuracy of the bus voltage overvoltage is influenced. When the time interval of the set time interval is greater than the period of the bus voltage, once the bus voltage is overvoltage, the detection voltage greater than the set voltage threshold can be monitored in each time interval, and therefore the bus voltage overvoltage is effectively identified.
In an embodiment of the present invention, the detection voltage received in the decision circuit 13 is a voltage corresponding to a set voltage-dividing resistor of the auxiliary winding.
As shown in fig. 3, in an embodiment of the present invention, the primary control circuit further includes a voltage conversion circuit 11, an input terminal of the voltage conversion circuit 11 is coupled to a connection point of a first voltage-dividing resistor R1 and a second voltage-dividing resistor R2 of the auxiliary winding, and an output terminal of the voltage conversion circuit is coupled to the decision circuit 13; the voltage conversion circuit is used for receiving a set current, converting the received set current I1 into the detection voltage V1 in proportion to the set current I1, and inputting the detection voltage into the decision circuit.
FIG. 4 is a schematic circuit diagram of an isolated power conversion circuit according to an embodiment of the present invention; referring to fig. 4, in an embodiment of the present invention, the control circuit of the present invention is used in an isolated power converter circuit, and can control the operating state of the power device Q1 according to the current I1.
In an embodiment of the present invention, the decision circuit includes: comparison circuit, interval control circuit, count circuit. The comparison circuit is used for comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold value, the comparison circuit outputs a first control signal to the interval control circuit. The interval control circuit is used for controlling the time interval of each time interval; if at least one first control signal is received in a time interval, the interval control circuit outputs a second control signal to the counting circuit in a corresponding time interval. The counting circuit is used for carrying out counting operation when a second control signal sent by the interval control circuit can be received in each time interval; if the counting reaches a set threshold value in at least two continuously set time intervals, the counting circuit outputs a third control signal for controlling the primary circuit to be in an open circuit state to the driving circuit; otherwise, the counting circuit resets the counting and waits for counting again.
FIG. 5 is a schematic diagram of a decision circuit according to an embodiment of the present invention; referring to fig. 5, in an embodiment of the present invention, the decision circuit 13 includes a comparison circuit 131, a delay jitter elimination circuit 133, an interval control circuit 135, and a counting circuit 137, which are connected in sequence.
The comparison circuit 131 is used for comparing the detection voltage V1 with a set voltage threshold Vref; when the detection voltage V1 is greater than the setting voltage threshold Vref, the comparison circuit 131 outputs a setting signal to the delay jitter elimination circuit 133.
The input terminal of the delay jitter-eliminating circuit 133 is coupled to the output terminal of the comparison circuit 131, the output terminal of the delay jitter-eliminating circuit 133 is coupled to the input terminal of the interval control circuit 135, and the delay jitter-eliminating circuit 133 is configured to perform a delay jitter-eliminating process for a duration of a set time on the first control signal when the comparison circuit 131 detects that the detected voltage is greater than the set voltage threshold. In an embodiment of the invention, the duration setting time of the anti-jitter delay circuit for the anti-jitter delay process is 50-300 us. In an embodiment of the invention, the duration setting time of the anti-jitter delay circuit for the anti-jitter delay process is 100 us.
The interval control circuit 135 is used to control the time interval of each time interval; if at least one first control signal is received in each time interval, the interval control circuit 135 outputs a second control signal to the counting circuit 137. In an embodiment of the present invention, the interval control circuit 135 is configured to control each time interval to be 15ms to 20ms (or other time intervals, such as 15ms to 128 ms).
The counting circuit 137 is configured to perform a counting operation (e.g. count plus 1) when the second control signal sent by the interval control circuit 135 can be received in each time interval; if the count reaches a set threshold value in at least two time intervals that are set continuously (in an embodiment of the present invention, the count reaches 4 in 4 time intervals, or may reach other times), the counting circuit 137 outputs a third control signal for controlling the primary circuit to be in an open state to the driving circuit 15; otherwise, the counting circuit resets the count and waits for the count again (in an embodiment of the present invention, the count may be reset to 0). In an embodiment of the invention, if the count reaches the set threshold value in at least two time intervals set consecutively, the counting circuit 137 outputs a third control signal for controlling the power device Q1 to turn off to the driving circuit 15.
In an embodiment of the present invention, the counting circuit 137 can receive the second control signal during 4 consecutive time intervals, and the counting circuit 137 outputs a third control signal for controlling the power device Q1 to turn off to the driving circuit 15.
FIG. 7 is a timing diagram of waveforms of a portion of signals according to an embodiment of the present invention; referring to fig. 7, in an embodiment of the present invention, as long as the peak value of the Vbus voltage is greater than Vovp, a first pulse control signal Vc1 is generated in a corresponding time interval; and carrying out time delay jitter elimination processing for the first control signal for a set time. Vovp is a set threshold voltage, steamed bread wave Va is a waveform obtained after alternating current full-wave rectification, and Vbus is a waveform obtained after Va is filtered. In a time interval (T1, T2, T3, or T4), regardless of whether one or more first pulse control signals Vc1 are output, only one second pulse control signal Vc2 is generated, which second pulse control signal Vc2 increments the count circuit count by 1. When the second pulse control signal Vc2 is generated in 4 continuous time intervals, the counting circuit outputs a third pulse control signal Vctl, and the judgment of the overvoltage of the bus voltage Vbus is realized.
Because the peak value of the Vbus voltage is larger than Vovp and the time delay is 100us for eliminating the jitter every time, the judgment is performed once, so that the overvoltage point of the Vbus is basically the same as the Vovp regardless of the weight of the load (namely, regardless of the ripple magnitude of the Vbus), the judgment mode is not influenced by the ripple magnitude, and the detection precision of the bus voltage is greatly improved. Illustratively, bus voltage Vbus exceeds Vovp for 100us in a time interval, which represents a decision, and first pulse control signal Vc1 is output as long as the maximum value of the bus voltage is greater than Vovp, so that the overvoltage value of Vbus is equal to Vovp regardless of the magnitude of Vripple.
Referring to fig. 4, the present invention discloses an isolated power conversion circuit, which includes a primary side circuit and a secondary side circuit, wherein the primary side circuit includes a primary side winding, a primary side switch, and the primary side control circuit.
In an embodiment of the invention, the isolated power conversion circuit further includes an auxiliary winding, the auxiliary winding is coupled to a first end of a first voltage-dividing resistor, and a second end of the first voltage-dividing resistor is coupled to a second voltage-dividing resistor and the primary side control circuit, respectively. Illustratively, the current at the second end of the first voltage-dividing resistor is converted by the voltage conversion circuit to obtain the detection voltage. The turn ratio of the primary winding and the auxiliary winding can be determined, and the voltage of the bus voltage Vbus is correspondingly proportional to the detection voltage, so that the detection voltage can reflect the change condition of the bus voltage Vbus.
The invention also discloses a control method for providing bus voltage overvoltage protection for the isolated power conversion circuit, which comprises the following steps:
step S1, the decision circuit outputs a control command according to the received detection voltage representing the bus voltage and the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and sending a control command for controlling the primary circuit to be in an open circuit state when the count reaches the set threshold value;
and step S2, the drive circuit controls the conduction state of the primary side circuit according to the control command.
FIG. 6 is a flow chart of a control method according to an embodiment of the present invention; referring to fig. 6, in an embodiment of the present invention, the control method includes:
step S1, receiving a set current, converting the received set current into the detection voltage proportional to the set current;
step S2, the decision circuit outputs a control command according to the received detection voltage representing the bus voltage and the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and sending a control command for controlling the primary circuit to be in an open circuit state when the count reaches the set threshold value;
and step S3, the driving circuit controls the conduction state of the primary side circuit according to the control command.
In an embodiment of the present invention, the step S2 includes:
step S21, comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold, outputting a first control signal;
step S22, controlling the time interval of each time interval; judging whether at least one first control signal is received in each time interval; if at least one first control signal is received in a time interval, outputting a second control signal in the time interval;
step S23, counting operation is carried out when the second control signal can be received in each time interval; if the count reaches a set threshold value in at least two continuously set time intervals, outputting a third control signal for controlling the primary circuit to be in an open circuit state; otherwise, the counting is reset and the counting is waited again.
In an embodiment of the present invention, the step S21 further includes: and when the detected voltage is detected to be larger than a set voltage threshold value, carrying out time delay jitter elimination processing on the first control signal for a set time.
In an embodiment of the present invention, the step S2 includes:
comparing the detection voltage V1 with a set voltage threshold Vref; outputting a set first control signal in a state that the detection voltage V1 is greater than the set voltage threshold Vref (in another embodiment of the present invention, the set first control signal may be output when the detection voltage V1 is greater than the set voltage threshold Vref);
when the detection voltage is detected to be larger than a set voltage threshold value, carrying out time delay jitter elimination processing for the first control signal for a set time;
controlling the time interval of each time interval; if at least one first control signal is received in each time interval, outputting a second control signal;
counting operation is carried out when a second control signal can be received in each time interval; if the second control signal can be received in at least two time intervals which are set continuously, outputting a third control signal for controlling the primary circuit to be in an open circuit state (in an embodiment of the invention, outputting the third control signal for controlling the power device switch); otherwise, the counting circuit resets the counting and waits for counting again.
In summary, the primary side control circuit and the control method for the isolated power conversion circuit and the isolated power conversion circuit provided by the invention can reduce the standby power consumption of the system and improve the overvoltage detection precision of the bus voltage. The invention does not need to additionally increase a sampling divider resistor, saves the material cost and reduces the standby power consumption of the system. The control circuit can improve the overvoltage detection precision of the bus voltage.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.
Claims (14)
1. A primary side control circuit for an isolated power conversion circuit, the primary side control circuit comprising an overvoltage protection module, the overvoltage protection module being configured to protect the isolated power conversion circuit when a bus voltage of the isolated power conversion circuit is in overvoltage, the overvoltage protection module comprising:
the judgment circuit is used for receiving detection voltage representing bus voltage and outputting a control command according to the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and when the count reaches the set threshold value, sending a control command for controlling the primary side circuit to be in an open circuit state to a driving circuit by the judgment circuit so as to realize overvoltage protection;
the input end of the driving circuit is coupled with the judgment circuit, and the output end of the driving circuit is coupled with the primary side switch; the driving circuit is used for controlling the conduction state of the primary side circuit according to the control command of the decision circuit.
2. The primary control circuit of claim 1, wherein:
the decision circuit further comprises a time control module for controlling the time interval of the time interval.
3. The primary control circuit of claim 1, wherein:
the decision circuit includes:
the comparison circuit is used for comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold value, the comparison circuit outputs a first control signal to an interval control circuit;
an interval control circuit for controlling the time interval of each time interval; if at least one first control signal is received in a time interval, the interval control circuit outputs a second control signal to a counting circuit in a corresponding time interval;
the counting circuit is used for carrying out counting operation when a second control signal sent by the interval control circuit can be received in each time interval; if the count reaches a set threshold value in at least two continuously set time intervals, the counting circuit outputs a third control signal for controlling the primary circuit to be in an open circuit state to the driving circuit; otherwise, the counting circuit resets the counting and waits for counting again.
4. The primary control circuit of claim 3, wherein:
the decision circuit further comprises a delay jitter elimination circuit, wherein the input end of the delay jitter elimination circuit is coupled with the output end of the comparison circuit, the output end of the delay jitter elimination circuit is coupled with the input end of the interval control circuit, and the delay jitter elimination circuit is used for carrying out delay jitter elimination processing for lasting set time on the first control signal when the comparison circuit detects that the detection voltage is greater than the set voltage threshold value.
5. The primary control circuit of claim 1, wherein:
the detection voltage received in the decision circuit is a voltage corresponding to a set voltage dividing resistor of the auxiliary winding.
6. The primary control circuit of claim 1, wherein:
the primary side control circuit further comprises a voltage conversion circuit, the input end of the voltage conversion circuit is coupled with the connection point of the first voltage-dividing resistor and the second voltage-dividing resistor, and the output end of the voltage conversion circuit is coupled with the judgment circuit; the voltage conversion circuit is used for receiving a set current, converting the received set current into the detection voltage in proportion to the set current, and inputting the detection voltage into the judgment circuit.
7. The control circuit of claim 2, wherein:
and the time control module controls the time interval of the time interval to be greater than the period of the bus voltage.
8. The primary control circuit of claim 4, wherein:
the continuous set time of the time delay jitter elimination circuit for time delay jitter elimination processing is 50-300 us.
9. An isolated power conversion circuit comprising a primary circuit and a secondary circuit, the primary circuit comprising a primary winding, a primary switch, and the primary control circuit of any of claims 1-8.
10. The isolated power converter circuit of claim 9, further comprising an auxiliary winding, wherein the auxiliary winding is coupled to a first terminal of a first voltage-dividing resistor, and a second terminal of the first voltage-dividing resistor is coupled to a second voltage-dividing resistor and the primary control circuit, respectively.
11. A control method for providing bus voltage overvoltage protection for an isolated power conversion circuit, the control method comprising:
step S1, the decision circuit outputs a control command according to the received detection voltage representing the bus voltage and the detection voltage; the control command is used for controlling the conduction state of the primary side circuit; counting the number of time intervals when the detection voltage is greater than a set voltage threshold value in at least two continuously set time intervals, and sending a control command for controlling the primary circuit to be in an open circuit state when the count reaches the set threshold value;
and step S2, the drive circuit controls the conduction state of the primary side circuit according to the control command.
12. The control method according to claim 11, characterized in that:
the step S1 includes:
step S11, comparing the detection voltage with a set voltage threshold; when the detection voltage is larger than a set voltage threshold, outputting a first control signal;
step S12, controlling the time interval of each time interval; judging whether at least one first control signal is received in each time interval; if at least one first control signal is received in a time interval, outputting a second control signal in the time interval;
step S13, counting operation is carried out when the second control signal can be received in each time interval; if the count reaches a set threshold value in at least two continuously set time intervals, outputting a third control signal for controlling the primary circuit to be in an open circuit state; otherwise, the counting is reset and the counting is waited again.
13. The control method according to claim 12, characterized in that:
the step S11 further includes: and when the detected voltage is detected to be larger than a set voltage threshold value, carrying out time delay jitter elimination processing on the first control signal for a set time.
14. The control method according to claim 11, characterized in that:
the control method further includes step S0: receiving a set current, and converting the received set current into the detection voltage proportional to the set current.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910830593.7A CN112448370A (en) | 2019-09-04 | 2019-09-04 | Primary side control circuit and control method and isolated power supply conversion circuit |
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| CN201910830593.7A CN112448370A (en) | 2019-09-04 | 2019-09-04 | Primary side control circuit and control method and isolated power supply conversion circuit |
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