CN113687177A - Transformer bias magnetic detection circuit in bridge type isolated switch power supply - Google Patents
Transformer bias magnetic detection circuit in bridge type isolated switch power supply Download PDFInfo
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- CN113687177A CN113687177A CN202111238076.4A CN202111238076A CN113687177A CN 113687177 A CN113687177 A CN 113687177A CN 202111238076 A CN202111238076 A CN 202111238076A CN 113687177 A CN113687177 A CN 113687177A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- Condensed Matter Physics & Semiconductors (AREA)
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- Inverter Devices (AREA)
Abstract
The invention provides a transformer magnetic biasing detection circuit in a bridge isolation type switch power supply, which comprises a first bidirectional switch unit and a first resistance sampling unit, wherein a serial branch formed by connecting the first bidirectional switch unit and the first resistance sampling unit in series is connected to two ends of a secondary winding of a first current transformer, the first bidirectional switch unit can be conducted in two directions, a second bidirectional switch unit and a second resistance sampling unit are connected in series, a serial branch formed by connecting the second bidirectional switch unit and the second resistance sampling unit in series is connected to two ends of a secondary winding of a second current transformer, the second bidirectional switch unit can be conducted in two directions, a signal processing circuit receives a first sampling signal output by the first resistance sampling unit and a second sampling signal output by the second resistance sampling unit, the first sampling signal and the second sampling signal are opposite, and the first sampling signal and the second sampling signal are superposed to accurately detect a transformer current signal, and the circuit structure is simple.
Description
Technical Field
The invention relates to the field of power supplies, in particular to a transformer bias detection circuit in a bridge isolation type switching power supply.
Background
The bridge type isolated switching power supply is one of the most commonly used circuit topologies in the current DC/DC converter, and is the preferred topology in medium and high power application occasions, such as vehicle-mounted OBC, photovoltaic, energy storage and other application occasions. A common bridge-isolated switching power supply includes a full-bridge circuit topology and a half-full-bridge circuit topology, as shown in fig. 1, which is a schematic diagram of a typical full-bridge circuit topology structure, and includes a transformer T, a primary side circuit includes a full-bridge switching unit composed of a switching tube S1 to a switching tube S4, a switching tube S1 and a switching tube S2 form a first bridge arm, a switching tube S3 and a switching tube S4 form a second bridge arm, a switching tube S1 and a switching tube S3 are upper tubes, a switching tube S2 and a switching tube S4 are lower tubes, and a full-bridge switching unit receives an input voltage Uin, and further includes a secondary side rectifier circuit 210 connected to a secondary side winding of the transformer T and outputting an output voltage Uout. As shown in fig. 2, a typical half-bridge circuit topology is different from a full-bridge circuit in that a primary side of the half-bridge circuit topology includes a switching leg formed by a switching tube S1 and a switching tube S2, and a capacitor leg formed by a first capacitor C1 and a second capacitor C2, and the switching leg and the capacitor leg form a half-bridge switching unit.
As shown in fig. 1 and 2, each of the bridge-isolated switching power supplies includes a high-frequency transformer T, because: the on-state voltage drops of all switching tubes in the bridge isolation type switching power supply are different, the positive and negative half cycles of driving pulses of the switching tubes output by the control circuit are asymmetrical, and the like, so that the positive and negative waveform amplitudes of the voltage applied to the primary side of the transformer are unequal, the magnetic bias phenomenon of the transformer is caused, and the bridge isolation type switching power supply is generally used in the transformer. When the magnetic bias is serious, the magnetic core of the transformer can be saturated in a single direction, so that the primary winding is over-current instantly and the power device is damaged. Therefore, in various bridge-type isolated switching power supplies, no matter which control mode is adopted, corresponding transformer magnetic biasing suppression measures must be adopted to ensure that the transformer is always in a symmetrical balanced operation state.
The existing commonly used transformer magnetic biasing suppression measure is to connect a blocking capacitor in series in a transformer loop, and because the blocking capacitor needs a large current flowing through a power stage, the blocking capacitor is generally large in size, and the larger the power current is, the larger the size of the required blocking capacitor is, and the higher the cost is, which is contrary to the miniaturization development trend of a power converter. In addition, some circuits cannot be provided with blocking capacitors, that is, the blocking capacitors cannot be applied to all bridge-type isolated switching power supplies. The magnetic biasing quantity of the transformer can be detected through the transformer magnetic biasing detection circuit, and then the magnetic biasing quantity is controlled to be minimum through the magnetic biasing control circuit.
Therefore, designing a transformer bias detection circuit in a bridge-isolated switching power supply to accurately detect the bias amount of the transformer is a key point of research in the industry.
Disclosure of Invention
The invention provides a transformer bias detection circuit in a bridge isolation type switching power supply, which comprises: the first current transformer comprises a primary winding and a secondary winding, and the primary winding is connected in series with a first switching tube in a bridge switching unit of the bridge isolation type switching power supply; the second current transformer comprises a primary winding and a secondary winding, the primary winding is connected with a second switching tube in a bridge switching unit of the bridge isolation type switching power supply in series, and the phase difference of driving signals of the first switching tube and the second switching tube is 180 degrees when the bridge isolation type switching power supply works; the first bidirectional switch unit and the first resistance sampling unit are connected in series, a series branch formed by the first bidirectional switch unit and the first resistance sampling unit is connected to two ends of a secondary winding of the first current transformer, and the first bidirectional switch unit can be conducted in two directions and is conducted during the conduction period of the first switch tube; the second bidirectional switch unit and the second resistance sampling unit are connected in series, a series branch formed by the second bidirectional switch unit and the second resistance sampling unit is connected to two ends of a secondary winding of the second current transformer, and the second bidirectional switch unit can be conducted in two directions and is conducted during the conduction period of the second switch tube; and the first input end of the signal processing circuit is connected with the first resistance sampling unit so as to receive a first sampling signal representing the current flowing through the first switch tube, the second input end of the signal processing circuit is connected with the second resistance sampling unit so as to receive a second sampling signal representing the current flowing through the second switch tube, wherein the first sampling signal and the second sampling signal are opposite, and the signal processing circuit outputs a transformer current representation signal after the first sampling signal and the second sampling signal are superposed.
Furthermore, the first switching tube and the second switching tube are upper and lower tubes on the same bridge arm, upper tubes on two bridge arms or lower tubes on two bridge arms of the bridge type switching unit.
Furthermore, the current transformer further comprises a first reset and protection circuit and a second reset and protection circuit, wherein the first reset and protection circuit is connected between two ends of a secondary winding of the first current transformer and two ends of a series branch formed by the first bidirectional switch unit and the first resistance sampling unit, and the second reset and protection circuit is connected between two ends of a secondary winding of the second current transformer and two ends of a series branch formed by the second bidirectional switch unit and the second resistance sampling unit.
Furthermore, a primary winding of the first current transformer is connected with a first switch tube, wherein a connection point of the primary winding of the first current transformer and the first switch tube is a first connection point, a primary winding of the second current transformer is connected with a second switch tube, wherein a connection point of the primary winding of the second current transformer and the second switch tube is a second connection point, a first end of the first resistance sampling unit is connected with a homonymous end, opposite to the first connection point, of a secondary winding of the first current transformer, a second end of the first resistance sampling unit is connected with a heteronymous end, opposite to the first connection point, of the secondary winding of the first current transformer through the first bidirectional switch unit, a second end of the first resistance sampling unit is grounded, and a first sampling signal is output from the first end of the first resistance sampling unit; the first end of the second resistance sampling unit is connected with a synonym end of a secondary winding of the second current transformer relative to a second connection point, the second end of the second resistance sampling unit is connected with a homonym end of the secondary winding of the second current transformer relative to the second connection point through the second bidirectional switch unit, the second end of the second resistance sampling unit is grounded, and a second sampling signal is output from the first end of the second resistance sampling unit.
Furthermore, a primary winding of the first current transformer is connected with a first switch tube, wherein a connection point of the primary winding of the first current transformer and the first switch tube is a first connection point, a primary winding of the second current transformer is connected with a second switch tube, wherein a connection point of the primary winding of the second current transformer and the second switch tube is a second connection point, a first end of a first resistance sampling unit is connected with a homonymous end, relative to the first connection point, of a secondary winding of the first current transformer through a first bidirectional switch unit, a second end of the first resistance sampling unit is connected with a synonym end, relative to the first connection point, of the secondary winding of the first current transformer, a second end of the first resistance sampling unit is grounded, and a first sampling signal is output from the first end of the first resistance sampling unit; the first end of the second resistance sampling unit is connected with a synonym end of a secondary winding of the second current transformer relative to a second connection point through the second bidirectional switch unit, the second end of the second resistance sampling unit is connected with a homonym end of the secondary winding of the second current transformer relative to the second connection point, the second end of the second resistance sampling unit is grounded, and a second sampling signal is output from the first end of the second resistance sampling unit.
Furthermore, the first bidirectional switch unit and the second bidirectional switch unit are formed by two metal oxide semiconductor field effect transistors of common source.
Furthermore, both ends of the metal oxide semiconductor field effect transistor are connected with a resistor in parallel.
Furthermore, the first resistance sampling unit comprises a first resistance, and the second resistance sampling unit comprises a second resistance.
Furthermore, the bidirectional switch control unit is further included for outputting a first control signal to the control terminal of the first bidirectional switch unit and outputting a second control signal to the control terminal of the second bidirectional switch unit, so as to control the first bidirectional switch unit to be conducted during the conduction period of the first switch tube and the second bidirectional switch unit to be conducted during the conduction period of the second switch tube.
Furthermore, the switch control unit further includes a switch control unit, a first output end of which outputs a control signal DS11 to a control end of the first switch tube, and a second output end of which outputs a control signal DS22 to a control end of the second switch tube, so as to control the first switch tube and the second switch tube to be turned on with a phase difference of 180 degrees when the bridge isolation type switch power supply works, and the switch control unit further includes a first inverter and a second inverter, an input end of the first inverter is connected to a second output end of the switch control unit to receive the control signal DS22, the control signal DS22 is inverted to obtain a first control signal to a control end of the first bidirectional switch unit, an input end of the second inverter is connected to a first output end of the switch control unit to receive the control signal DS11, and the control signal DS11 is inverted to obtain a second control signal to a control end of the second bidirectional switch unit.
Furthermore, the duty cycle of the first bidirectional switching unit is smaller than that of the first switching tube, and the duty cycle of the second bidirectional switching unit is smaller than that of the second switching tube.
Furthermore, the duty ratio of the first bidirectional switch unit is the same as that of the first switch tube, and the duty ratio of the second bidirectional switch unit is the same as that of the second switch tube.
Drawings
Fig. 1 is a schematic diagram of a typical full-bridge circuit topology.
Fig. 2 is a schematic diagram of a typical half-bridge circuit topology.
Fig. 3 is a block diagram illustrating a transformer bias detection circuit in a bridge-isolated switching power supply according to an embodiment of the invention.
Fig. 4 is a schematic circuit diagram of a transformer bias detection circuit in a bridge-isolated switching power supply according to an embodiment of the invention.
Fig. 5 is a signal waveform diagram of the circuit shown in fig. 4.
Fig. 6 is a schematic circuit diagram of a transformer bias detection circuit in a bridge-isolated switching power supply according to another embodiment of the invention.
Fig. 7 is a block diagram of a transformer bias detection circuit in a bridge-isolated switching power supply according to another embodiment of the invention.
Fig. 8 is a block diagram of a transformer bias detection circuit in a bridge-isolated switching power supply according to another embodiment of the invention.
Fig. 9 is a circuit diagram of the signal processing circuit shown in fig. 3 according to an embodiment of the invention.
Fig. 10 is a circuit diagram of the switch control unit shown in fig. 8 according to an embodiment of the invention.
Detailed Description
The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In an embodiment of the present invention, in order to provide a transformer bias detection circuit in a bridge-isolated switching power supply, specifically, refer to a block diagram of the transformer bias detection circuit in the bridge-isolated switching power supply according to an embodiment of the present invention shown in fig. 3, the transformer bias detection circuit in the bridge-isolated switching power supply according to the present invention is used for detecting a dc bias amount of a high-frequency transformer in the bridge-isolated switching power supply, specifically, refer to fig. 3, the transformer bias detection circuit in the bridge-isolated switching power supply according to an embodiment of the present invention includes:
the first current transformer CT1 comprises a primary winding 11 and a secondary winding 12, wherein the primary winding 11 is connected in series with a first switching tube S11 in a bridge switching unit of a bridge isolation type switching power supply;
the second current transformer CT2 comprises a primary winding 21 and a secondary winding 22, the primary winding 21 is connected in series with a second switching tube S22 in a bridge switching unit of the bridge isolation type switching power supply, wherein the phase difference between driving signals of the first switching tube S11 and the second switching tube S22 is 180 degrees when the bridge isolation type switching power supply works;
the first bidirectional switch unit 111 and the first resistance sampling unit 112 are connected in series, a series branch formed by the first bidirectional switch unit 111 and the first resistance sampling unit 112 is connected to two ends of the secondary winding 12 of the first current transformer CT1, and the first bidirectional switch unit 111 can be conducted in both directions and is conducted during the conduction period of the first switch tube S11;
the second bidirectional switch unit 121 and the second resistance sampling unit 122, the second bidirectional switch unit 121 and the second resistance sampling unit 122 are connected in series, and a series branch formed by the second bidirectional switch unit 121 and the second resistance sampling unit 122 is connected to two ends of the secondary winding 22 of the second current transformer CT2, the second bidirectional switch unit 121 can be conducted in both directions and is conducted during the conduction period of the second switch tube S22;
a signal processing circuit 130, a first input terminal of which is connected to the first resistance sampling unit 112 to receive a first sampling signal Vs1 representing the current flowing through the first switch tube S11, a second input terminal of which is connected to the second resistance sampling unit 122 to receive a second sampling signal Vs2 representing the current flowing through the second switch tube S22, wherein the first sampling signal Vs1 is inverse to the second sampling signal Vs2, and the signal processing circuit 130 outputs a transformer current representation signal Vt after the first sampling signal Vs1 and the second sampling signal Vs2 are overlapped.
Thus, since the phases of the driving signals of the first switch tube S11 and the second switch tube S22 are 180 degrees different when the bridge-isolated switching power supply operates, and the first bidirectional switch unit 111 is controlled to be turned on during the on period of the first switch tube S11, and the second bidirectional switch unit 121 is controlled to be turned on during the on period of the second switch tube S22, the first resistance sampling unit 112 can output the first sampling signal Vs1 representing the current flowing through the first switch tube S11 only during the period when the first switch tube S11 flows the power current, and the second resistance sampling unit 122 can output the second sampling signal Vs2 representing the current flowing through the second switch tube S22 only during the period when the second switch tube S22 flows the power current, and the connection relationship between the first input terminal of the signal processing circuit 130 and the first resistance sampling unit 112 and the connection relationship between the second input terminal and the second resistance sampling unit 122 are designed such that the first sampling signal Vs1 and the second sampling signal Vs2 are inverted, therefore, the transformer current characterization signal Vt output by the signal processing circuit 130 accurately reproduces the transformer current signal, so that the transformer magnetic bias detection circuit designed by the invention can accurately detect the transformer current signal, and has a simple circuit structure.
The "first sampled signal Vs1 and the second sampled signal Vs 2" described herein are inverted: when the first sampled signal Vs1 is in the positive half cycle, the second sampled signal Vs2 is in the negative half cycle, or when the first sampled signal Vs1 is in the negative half cycle, the second sampled signal Vs2 is in the positive half cycle.
Referring to the typical full-bridge circuit topology shown in fig. 1, the first switch tube S11 may be a switch tube S1, and the corresponding second switch tube S22 is a switch tube S3 or a switch tube S2; the first switch tube S11 can be a switch tube S3, and the corresponding second switch tube S22 can be a switch tube S1 or a switch tube S4. That is, the first switch tube S11 and the second switch tube S22 are upper and lower tubes on the same bridge arm, upper tubes on two bridge arms, or lower tubes on two bridge arms of the bridge-type switch unit, as long as the phases of the driving signals of the bridge-type isolated switch power supply are different by 180 degrees when the bridge-type isolated switch power supply operates. Similarly, for the typical half-bridge circuit topology shown in fig. 2, the first switch tube S11 and the second switch tube S22 are upper and lower tubes on the same arm.
Referring to fig. 3, the transformer bias detection circuit in the bridge-type isolated switching power supply further includes a first reset and protection circuit 114 and a second reset and protection circuit 124, the first reset and protection circuit 114 is connected between two ends of the secondary winding 12 of the first current transformer CT1 and two ends of a serial branch formed by the first bidirectional switch unit 111 and the first resistance sampling unit 112, and the second reset and protection circuit 124 is connected between two ends of the secondary winding 22 of the second current transformer CT2 and two ends of a serial branch formed by the second bidirectional switch unit 121 and the second resistance sampling unit 122. The first reset and protection circuit 114 is configured to protect the first bidirectional switch unit 111 and the first resistance sampling unit 112 and perform magnetic reset on the first current transformer CT1, and the second reset and protection circuit 124 is configured to protect the second bidirectional switch unit 121 and the second resistance sampling unit 122 and perform magnetic reset on the second current transformer CT 2. Specifically, referring to the circuit diagram of the transformer bias detection circuit in the bridge-isolated switching power supply according to the embodiment of the present invention shown in fig. 4, as shown in fig. 4, the first reset and protection circuit 114 includes a third resistor R3 and a third bi-directional transient voltage suppressor D3, the third resistor R3 and the third bi-directional transient voltage suppressor D3 are connected in parallel to two ends of the secondary winding 12 of the first current transformer CT1, the same second reset and protection circuit 124 includes a fourth resistor R4 and a fourth bi-directional transient voltage suppressor D4, and the fourth resistor R4 and the fourth bi-directional transient voltage suppressor D4 are connected in parallel to two ends of the secondary winding 22 of the second current transformer CT 2. The present invention is not limited to the specific structure of the first reset and protection circuit 114 and the second reset and protection circuit 124, and any circuit that can implement the magnetic reset and protection functions can be implemented.
Specifically, referring to fig. 4, in an embodiment of the present invention, the primary winding 11 of the first current transformer CT1 is connected to the first switch tube S11, wherein, the connection point of the primary winding 11 of the first current transformer CT1 and the first switch tube S11 is a first connection point, the primary winding 21 of the second current transformer CT2 is connected with the second switch tube S22, wherein, the connection point of the primary winding 21 of the second current transformer CT2 and the second switch tube S22 is a second connection point, the first end of the first resistance sampling unit 112 is connected with the same name end of the secondary winding 12 of the first current transformer CT1 relative to the first connection point, the second end of the first resistance sampling unit 112 is connected with the different name end of the secondary winding 12 of the first current transformer CT1 relative to the first connection point through the first bidirectional switch unit 111, the second end of the first resistance sampling unit 112 is grounded, and the first sampling signal Vs1 is output from the first end of the first resistance sampling unit 112; a first end of the second resistance sampling unit 122 is connected to a synonym end of the secondary winding 22 of the second current transformer CT2, which is opposite to the second connection point, a second end of the second resistance sampling unit 122 is connected to a synonym end of the secondary winding 22 of the second current transformer CT2, which is opposite to the second connection point, through the second bidirectional switch unit 121, a second end of the second resistance sampling unit 122 is grounded, and the second sampling signal Vs2 is output from the first end of the second resistance sampling unit 122. In this way, when the bridge-type isolated switching power supply operates, the first bidirectional switch unit 111 is controlled to be turned on during the on period of the first switch tube S11, and when the first sampling signal Vs1 sampled by the first resistance sampling unit 112 is positive, the second bidirectional switch unit 121 is controlled to be turned on during the on period of the second switch tube S22, and the second sampling signal Vs2 sampled by the second resistance sampling unit 122 is negative; or when the first sampling signal Vs1 sampled by the first resistance sampling unit 112 is negative, the second sampling signal Vs2 sampled by the second resistance sampling unit 122 is positive, that is, the first sampling signal Vs1 is opposite to the second sampling signal Vs2, and since the phase difference between the driving signals of the first switching tube S11 and the second switching tube S22 is 180 degrees when the bridge-isolated switching power supply operates, and the current flowing through the first switching tube S11 and the second switching tube S22 is identical to the current of the high-frequency isolation transformer in the bridge-isolated switching power supply, the first sampling signal Vs1 and the second sampling signal Vs2 are superimposed to accurately reproduce the transformer current signal. Specifically, referring to the signal waveform diagram of the circuit shown in fig. 4 shown in fig. 5, as shown in fig. 5, the phases of the driving signals of the first switch tube S11 and the second switch tube S22 are different by 180 degrees, the first switch tube S11 is turned on in synchronization with the first bidirectional switch unit 111, the second switch tube S22 is turned on in synchronization with the second bidirectional switch unit 121, if the first sampling signal Vs1 is positive during the turn-on period of the first bidirectional switch unit 111, the second sampling signal Vs2 is negative during the turn-on period of the second bidirectional switch unit 121, the first sampling signal Vs1 and the second sampling signal Vs2 are superimposed to accurately reproduce the transformer current signal. It is needless to say that the first sampling signal Vs1 is negative during the turn-on period of the first bidirectional switch unit 111, and the second sampling signal Vs2 is positive during the turn-on period of the second bidirectional line switch unit 121, as long as the connection relationship is such that the first sampling signal Vs1 and the second sampling signal Vs2 are inverted. In fig. 5, the control signal DS11 is a control signal of the first switch tube S11, the control signal DS22 is a control signal of the second switch tube S22, the first control signal D111 is a control signal of the first bidirectional switch unit 111, and the second control signal D112 is a control signal of the second bidirectional switch unit 121.
Referring to fig. 6, a schematic circuit diagram of a transformer bias detection circuit in a bridge-isolated switching power supply according to another embodiment of the present invention is shown, as shown in fig. 6, a primary winding 11 of a first current transformer CT1 is connected to a first switching tube S11, a connection point between the primary winding 11 of the first current transformer CT1 and the first switching tube S11 is a first connection point, a primary winding 21 of a second current transformer CT2 is connected to a second switching tube S22, a connection point between the primary winding 21 of the second current transformer CT2 and the second switching tube S22 is a second connection point, a first end of a first resistance sampling unit 112 is connected to a same-name end of a secondary winding 12 of the first current transformer CT1 relative to the first connection point through a first bidirectional switching unit 111, a second end of the first resistance sampling unit 112 is connected to a different-name end of the secondary winding 12 of the first current transformer CT1 relative to the first connection point, the second end of the first resistance sampling unit 112 is grounded, and the first sampling signal is output from the first end of the first resistance sampling unit 112; the first end of the second resistance sampling unit 122 is connected to the synonym end of the secondary winding 22 of the second current transformer CT2 corresponding to the second connection point through the second bidirectional switch unit 121, the second end of the second resistance sampling unit 122 is connected to the synonym end of the secondary winding 22 of the second current transformer CT2 corresponding to the second connection point, the second end of the second resistance sampling unit 122 is grounded, and the second sampling signal is output from the first end of the second resistance sampling unit 122, so that the signal waveform of the circuit is still shown in fig. 5, and the transformer current signal is accurately reproduced after the first sampling signal Vs1 and the second sampling signal Vs2 are superimposed. That is, in the present application, the connection relationship between the primary winding 11 and the secondary winding 12 of the first current transformer CT1, the connection relationship between the primary winding 21 and the secondary winding 22 of the second current transformer CT2, the connection relationship between the first bidirectional switch unit 111 and the first resistance sampling unit 112 and the secondary winding 12 of the first current transformer CT1, and the connection relationship between the second bidirectional switch unit 121 and the second resistance sampling unit 122 and the secondary winding 22 of the second current transformer CT2 are not specifically limited, as long as the obtained first sampling signal Vs1 and the obtained second sampling signal Vs2 are in a reverse direction.
As shown in fig. 4 and 6, the first and second bidirectional switching units 111 and 121 are formed of two Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) of common source. Specifically, the first bidirectional switch unit 111 includes a MOSFET SS11 and a MOSFET SS12, a MOSFET SS11 and a MOSFET SS12 are connected in common source, and gates of a MOSFET SS11 and a MOSFET SS12 are connected together to receive a switch control signal D111 that controls the MOSFET SS11 and the MOSFET SS12 to be turned on or off. The second bidirectional switch unit 121 includes a MOSFET SS21 and a MOSFET SS22, a MOSFET SS21 and a MOSFET SS22 are connected in common source, and gates of a MOSFET SS21 and a MOSFET SS22 are connected together to receive a switch control signal D112 that controls the MOSFET SS21 and the MOSFET SS22 to be turned on or off. Of course, the first bidirectional switch unit 111 and the second bidirectional switch unit 121 may also be connected by other electronic devices to form a device that can be controlled by the switch control signal and can be conducted bidirectionally, and the specific structure of the present invention is not limited. And since the first and second bidirectional switch units 111 and 121 are bidirectional switch units, the currents flowing in the secondary winding 12 of the first current transformer CT1 and the secondary winding 22 of the second current transformer CT2 can flow through the first and second bidirectional switch units 111 and 121, so that the first sampling signal Vs1 is formed at the first resistance sampling unit 112 and the second sampling signal Vs2 is formed at the second resistance sampling unit 122.
Further, a resistor, such as R11 and R12, is connected across both MOSFET SS11 and MOSFET SS12, and a resistor, such as R21 and R22, is connected across both MOSFET SS21 and MOSFET SS 22. To facilitate conduction of the MOSFETs SS11, SS12, SS21 and SS 22.
As shown in fig. 4 and 6, the first resistance sampling unit 112 includes a first resistor R1, and the second resistance sampling unit 122 includes a second resistor R2. However, the present invention is not limited to the specific result of the first resistance sampling unit 112 and the second resistance sampling unit 122, and may be a series-parallel connection of a plurality of resistances.
Further, referring to fig. 7, which is a block diagram illustrating a transformer bias detection circuit in a bridge-type isolated switching power supply according to another embodiment of the present invention, compared to fig. 3, the transformer bias detection circuit further includes a bidirectional switch control unit 140 that outputs a first control signal D111 to a control terminal of the first bidirectional switch unit 111 and outputs a second control signal D112 to a control terminal of the second bidirectional switch unit 112, so as to control the first bidirectional switch unit 111 to be turned on during a turn-on period of the first switch tube S11, and the second bidirectional switch unit 121 to be turned on during a turn-on period of the second switch tube S22. Specifically, the first bidirectional switch unit 111 may be turned on synchronously with the first switch tube S11, i.e. the duty cycle is the same; the second bidirectional switch unit 121 may be turned on synchronously with the second switch tube S22, i.e. its duty cycle is the same. Or, the duty ratio of the first bidirectional switch unit 111 is smaller than that of the first switch tube S11, and the duty ratio of the second bidirectional switch unit 121 is smaller than that of the second switch tube S22.
Further, referring to the block diagram of the transformer bias detection circuit in the bridge isolation type switching power supply of another embodiment of the present invention shown in fig. 8, compared with fig. 3, it further includes a switch control unit 150, a first output end of which outputs a control signal DS11 to a control end of the first switch tube S11, a second output end of which outputs a control signal DS22 to a control end of the second switch tube S22, so as to control the first switch tube S11 and the second switch tube S22 to be conducted with a phase difference of 180 degrees when the bridge isolation type switching power supply works, and includes a first inverter 161 and a second inverter 162, an input end of the first inverter 161 is connected to a second output end of the switch control unit 150 to receive the control signal DS22, the control signal DS22 is inverted to obtain a first control signal D111 to a control end of the first bidirectional switch unit 111, an input end of the second inverter 162 is connected to a first output end of the switch control unit 150, to receive the control signal DS11, the control signal DS11 is inverted to obtain the second control signal D112 to the control end of the second bidirectional switch unit 121, and specifically, referring to the waveform diagram of fig. 5, the first switch tube S11 and the second switch tube S22 are turned on at a phase difference of 180 degrees, the first switch tube S11 and the first bidirectional switch unit 111 are turned on synchronously, and the second switch tube S22 and the second bidirectional switch unit 121 are turned on synchronously.
Referring to the circuit diagram of the signal processing circuit shown in fig. 3 according to the embodiment of the invention shown in fig. 9, the circuit diagram includes a resistor R71 and a resistor R72, first ends of the resistor R71 and the resistor R72 respectively receive the first sampled signal Vs1 and the second sampled signal Vs2, second ends of the resistor R71 and the resistor R72 are connected to the positive input terminal of the operational amplifier through a resistor R73, the positive input terminal of the operational amplifier is further grounded through a series branch of a capacitor C71 and a capacitor C72, and a series branch of the resistor R76 and a capacitor C72 is grounded, a common node of the resistor R76 and the capacitor C72 is connected to the reference voltage Vref, the negative input terminal of the operational amplifier is grounded through a resistor R74, a resistor R75 and a capacitor C74 are connected between the negative input terminal and the output terminal of the operational amplifier, an output terminal of the operational amplifier is connected to a first end of the resistor R77, a second end of the resistor R77 is grounded through a capacitor C73, a second end of the resistor R77 is further connected to the anode of the diode D71 and the cathode 72, the cathode of the diode D71 is connected to a voltage source terminal, such as a 3.3V voltage source, the anode of the diode D72 is grounded, and the second terminal of the resistor R77 forms an output terminal of the signal processing circuit to output the transformer current characterization signal Vt. In the circuit of the signal processing circuit shown in fig. 9, the resistor R71, the resistor R72, the operational amplifier and peripheral circuits thereof constitute a voltage superimposing and differential amplifier, and the capacitor C73, the diode D71, and the diode D72 constitute a filter and clamp circuit. The signal processing circuit shown in fig. 9 is only an embodiment, and the specific structure of the signal processing circuit is not limited in the present invention, as long as it can superpose the first sampled signal Vs1 and the second sampled signal Vs2 to obtain the stable transformer current characterization signal Vt.
Referring to fig. 10, fig. 10 is a circuit schematic diagram of the switch control unit shown in fig. 8 according to an embodiment of the present invention, an input terminal of the switch control unit 150 is connected to an output terminal of the signal processing circuit 130, receives the transformer current characterization signal Vt output by the signal processing circuit 130, and the switch control unit 150 includes a first comparator 101, a PI 102, a second comparator 103, and a PWM generator 104. The first comparator 101 receives the transformer current characterization signal Vt and the reference voltage Vref, the output terminal is connected to the PI 102, the PI 102 outputs the duty deviation signal Δ D, the second comparator 103 receives the duty deviation signal Δ D and the initial duty signal D0, the output terminal is connected to the PWM generator 104 and outputs the control signal DS11 and the control signal DS22, the switch control unit shown in fig. 10 is only an embodiment, and the specific structure of the switch control unit is not limited in the present invention as long as it can output the control signal DS11 and the control signal DS22 to the first switch tube S11 and the second switch tube S22 according to the transformer current characterization signal Vt to control the bias amount of the high-frequency transformer in the bridge isolation type switch power supply to be as small as possible.
Thus, the transformer bias detection circuit in the bridge-type isolated switching power supply shown in fig. 3 can accurately detect the current signal of the high-frequency transformer in the bridge-type isolated switching power supply, and the switch control unit 150 shown in fig. 10 outputs the control signal of the switching tube in the bridge-type switching unit in the bridge-type isolated switching power supply according to the transformer current characterization signal Vt, so as to control the bias amount of the high-frequency transformer in the bridge-type isolated switching power supply to be as small as possible, thereby improving the reliability of the bridge-type isolated switching power supply. And the size of the bridge type isolation switch power supply is reduced because a blocking capacitor with larger size is saved.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (12)
1. A transformer bias detection circuit in a bridge isolation type switching power supply is characterized by comprising:
the first current transformer comprises a primary winding and a secondary winding, and the primary winding is connected in series with a first switching tube in a bridge switching unit of the bridge isolation type switching power supply;
the second current transformer comprises a primary winding and a secondary winding, the primary winding is connected with a second switching tube in a bridge switching unit of the bridge isolation type switching power supply in series, and the phase difference of driving signals of the first switching tube and the second switching tube is 180 degrees when the bridge isolation type switching power supply works;
the first bidirectional switch unit and the first resistance sampling unit are connected in series, a series branch formed by the first bidirectional switch unit and the first resistance sampling unit is connected to two ends of a secondary winding of the first current transformer, and the first bidirectional switch unit can be conducted in two directions and is conducted during the conduction period of the first switch tube;
the second bidirectional switch unit and the second resistance sampling unit are connected in series, a series branch formed by the second bidirectional switch unit and the second resistance sampling unit is connected to two ends of a secondary winding of the second current transformer, and the second bidirectional switch unit can be conducted in two directions and is conducted during the conduction period of the second switch tube;
and the first input end of the signal processing circuit is connected with the first resistance sampling unit so as to receive a first sampling signal representing the current flowing through the first switch tube, the second input end of the signal processing circuit is connected with the second resistance sampling unit so as to receive a second sampling signal representing the current flowing through the second switch tube, wherein the first sampling signal and the second sampling signal are opposite, and the signal processing circuit outputs a transformer current representation signal after the first sampling signal and the second sampling signal are superposed.
2. The transformer bias detection circuit in the bridge-type isolated switching power supply according to claim 1, wherein the first switching tube and the second switching tube are upper and lower tubes on a same bridge arm, upper tubes on two bridge arms, or lower tubes on two bridge arms of the bridge-type switching unit.
3. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, further comprising a first reset and protection circuit and a second reset and protection circuit, wherein the first reset and protection circuit is connected between two ends of the secondary winding of the first current transformer and two ends of a serial branch formed by the first bidirectional switching unit and the first resistance sampling unit, and the second reset and protection circuit is connected between two ends of the secondary winding of the second current transformer and two ends of a serial branch formed by the second bidirectional switching unit and the second resistance sampling unit.
4. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 2, it is characterized in that a primary winding of a first current transformer is connected with a first switch tube, wherein the connection point of the primary winding of the first current transformer and the first switch tube is a first connection point, a primary winding of a second current transformer is connected with a second switch tube, wherein the connection point of the primary winding of the second current transformer and the second switching tube is a second connection point, the first end of the first resistance sampling unit is connected with the homonymous end of the secondary winding of the first current transformer relative to the first connection point, the second end of the first resistance sampling unit is connected with the heteronymous end of the secondary winding of the first current transformer relative to the first connection point through the first bidirectional switching unit, the second end of the first resistance sampling unit is grounded, and a first sampling signal is output from the first end of the first resistance sampling unit; the first end of the second resistance sampling unit is connected with a synonym end of a secondary winding of the second current transformer relative to a second connection point, the second end of the second resistance sampling unit is connected with a homonym end of the secondary winding of the second current transformer relative to the second connection point through the second bidirectional switch unit, the second end of the second resistance sampling unit is grounded, and a second sampling signal is output from the first end of the second resistance sampling unit.
5. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 2, it is characterized in that a primary winding of a first current transformer is connected with a first switch tube, wherein the connection point of the primary winding of the first current transformer and the first switch tube is a first connection point, a primary winding of a second current transformer is connected with a second switch tube, wherein the connection point of the primary winding of the second current transformer and the second switching tube is a second connection point, the first end of the first resistance sampling unit is connected with the homonymous end of the secondary winding of the first current transformer relative to the first connection point through the first bidirectional switching unit, the second end of the first resistance sampling unit is connected with the heteronymous end of the secondary winding of the first current transformer relative to the first connection point, the second end of the first resistance sampling unit is grounded, and a first sampling signal is output from the first end of the first resistance sampling unit; the first end of the second resistance sampling unit is connected with a synonym end of a secondary winding of the second current transformer relative to a second connection point through the second bidirectional switch unit, the second end of the second resistance sampling unit is connected with a homonym end of the secondary winding of the second current transformer relative to the second connection point, the second end of the second resistance sampling unit is grounded, and a second sampling signal is output from the first end of the second resistance sampling unit.
6. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, wherein the first bidirectional switch unit and the second bidirectional switch unit are formed by two common-source metal oxide semiconductor field effect transistors.
7. The transformer bias detection circuit in a bridge isolated switching power supply of claim 6, wherein a resistor is connected in parallel to both ends of the MOSFET.
8. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, wherein the first resistance sampling unit includes a first resistor, and the second resistance sampling unit includes a second resistor.
9. The transformer bias detection circuit in the bridge-type isolated switching power supply according to claim 1, further comprising a bidirectional switch control unit outputting a first control signal to a control terminal of the first bidirectional switch unit and outputting a second control signal to a control terminal of the second bidirectional switch unit, so as to control the first bidirectional switch unit to be turned on during a turn-on period of the first switch tube and the second bidirectional switch unit to be turned on during a turn-on period of the second switch tube.
10. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, it is characterized in that the switch control unit also comprises a first output end of the switch control unit which outputs a control signal DS11 to a control end of the first switch tube, the second output end outputs a control signal DS22 to the control end of the second switch tube to control the first switch tube and the second switch tube to conduct with a phase difference of 180 degrees when the bridge-type isolated switch power supply works, and comprises a first inverter and a second inverter, wherein the input end of the first inverter is connected with the second output end of the switch control unit, to receive the control signal DS22, to invert the control signal DS22 to obtain a first control signal to the control terminal of the first bidirectional switch unit, the input terminal of the second inverter is connected to the first output terminal of the switch control unit, the second switch unit is coupled to receive the control signal DS11, and inverts the control signal DS11 to obtain a second control signal to the control terminal of the second bidirectional switch unit.
11. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, wherein a duty cycle of the first bidirectional switching unit is smaller than a duty cycle of the first switching tube, and a duty cycle of the second bidirectional switching unit is smaller than a duty cycle of the second switching tube.
12. The transformer bias detection circuit in the bridge type isolated switching power supply according to claim 1, wherein the duty cycle of the first bidirectional switching unit is the same as that of the first switching tube, and the duty cycle of the second bidirectional switching unit is the same as that of the second switching tube.
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| CN202111238076.4A CN113687177A (en) | 2021-10-25 | 2021-10-25 | Transformer bias magnetic detection circuit in bridge type isolated switch power supply |
| CN202220596565.0U CN217034126U (en) | 2021-10-25 | 2022-03-18 | Transformer bias magnetic detection circuit in bridge type isolated switch power supply |
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| CN202111238076.4A CN113687177A (en) | 2021-10-25 | 2021-10-25 | Transformer bias magnetic detection circuit in bridge type isolated switch power supply |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101520474A (en) * | 2009-03-24 | 2009-09-02 | 东华大学 | Magnetic biasing on-line detection method for transformer based on single Hall current sensor |
| CN202649445U (en) * | 2012-05-17 | 2013-01-02 | 东华大学 | On-line detection device for magnetic bias of core of full bridge converter transformer |
| CN110365216A (en) * | 2019-07-31 | 2019-10-22 | 上海军陶电源设备有限公司 | Current sampling circuit and full-bridge switching power supply circuit |
| CN112701937A (en) * | 2020-12-16 | 2021-04-23 | 河南海格经纬信息技术有限公司 | Method for inhibiting DC magnetic bias of DC converter transformer |
| CN113067457A (en) * | 2021-06-03 | 2021-07-02 | 杭州富特科技股份有限公司 | Current sampling circuit based on bridge circuit |
-
2021
- 2021-10-25 CN CN202111238076.4A patent/CN113687177A/en active Pending
-
2022
- 2022-03-18 CN CN202220596565.0U patent/CN217034126U/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101520474A (en) * | 2009-03-24 | 2009-09-02 | 东华大学 | Magnetic biasing on-line detection method for transformer based on single Hall current sensor |
| CN202649445U (en) * | 2012-05-17 | 2013-01-02 | 东华大学 | On-line detection device for magnetic bias of core of full bridge converter transformer |
| CN110365216A (en) * | 2019-07-31 | 2019-10-22 | 上海军陶电源设备有限公司 | Current sampling circuit and full-bridge switching power supply circuit |
| CN112701937A (en) * | 2020-12-16 | 2021-04-23 | 河南海格经纬信息技术有限公司 | Method for inhibiting DC magnetic bias of DC converter transformer |
| CN113067457A (en) * | 2021-06-03 | 2021-07-02 | 杭州富特科技股份有限公司 | Current sampling circuit based on bridge circuit |
Non-Patent Citations (1)
| Title |
|---|
| 赵娟,等: "电力变压器直流偏磁检测方法研究", 《传感技术学报》 * |
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