CN217362912U - Magnetic saturation control system of low-power transformer - Google Patents
Magnetic saturation control system of low-power transformer Download PDFInfo
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- CN217362912U CN217362912U CN202221225759.6U CN202221225759U CN217362912U CN 217362912 U CN217362912 U CN 217362912U CN 202221225759 U CN202221225759 U CN 202221225759U CN 217362912 U CN217362912 U CN 217362912U
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- 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 utility model discloses a magnetic saturation control system of a low-power transformer, which relates to the technical field of magnetic saturation control of transformers and comprises an input rectifying and filtering unit, an input filtering unit, an output voltage detection unit and an input detection control unit, wherein the input rectifying and filtering unit detects input voltage waveform as the reference of frequency detection, the output condition of a primary coil T1B of the transformer and the output condition of a sampling coil T1A of the transformer are obtained through the output voltage detection unit and the input detection control unit, and the excitation power supply passing through the primary coil T1B of the transformer is further controlled according to the conditions, the control mode is flexible and changeable, so as to avoid the transformer being in a magnetic saturation state, and the problems that the leakage current specification exceeds the standard and the safety voltage exceeds the standard in the traditional mode are solved through the input rectifying and filtering unit, the input filtering unit and the circuit arrangement of the transformer, the signal power exceeds the standard, and the transmission balance specification exceeds the standard, so that the efficiency of the control system is greatly improved.
Description
Technical Field
The utility model relates to a transformer magnetic saturation control technical field specifically is a miniwatt power transformer magnetic saturation control system.
Background
The core of the transformer is a magnetic material, but the magnetic flux through the cell segments is limited. When the magnetic flux density increases to a certain value, the magnetic flux passing through the core does not increase or increases very slowly. At this time we say that the core is saturated, that is, the transformer is saturated. The saturation of the transformer causes the transformer to lose the energy storage capacity, and the transformer directly becomes a path state in a circuit. During operation of the transformer, the magnetic field is generated by the current, and the magnetic field strength increases with increasing current and voltage, but the increase is not infinite. When the magnetic field inside the transformer reaches a certain level, the increase of the current does not lead to the increase of the magnetic field strength. At this time, the transformer is considered to be in "magnetic saturation", and the current intensity at which the transformer is in magnetic saturation is regarded as the saturation current of the transformer. Generally, the operating current of the inductor exceeds the saturation current, or the magnetic permeability of the magnet (such as a transformer core) is too low and insufficient (the magnetic flux density is too large), which easily causes magnetic saturation. Magnetic saturation is also only one manifestation of transformer mass failure.
Simply stated, if a current is applied to the core coil, the magnetic field generated will also increase as the current increases. When the current reaches a certain level, the magnetic field generated does not continue to increase. At this time, the core and the coil enter a saturation region, and the core is in a saturation state. The current passing through the primary side of the transformer is saturated by the iron core, and the primary energy cannot be transferred to the secondary energy from the energy transfer perspective; similarly, in the case of a coil, the self-inductance is greatly reduced or even eliminated in the saturation state, and the direct current resistance of the coil is remained. Of course, the current passing through may increase, causing the connected equipment components to be damaged by the overcurrent. Several undesirable phenomena of transformer saturation are as follows:
1-the primary side of the transformer is heated and even exploded.
The 2-transformer is not operating.
3 the transformer burns MOSFET and even circuit board due to open circuit.
4-the actual power of the customer product cannot reach the design power due to transformer saturation.
When the iron core of the transformer works at full load, the magnetic flux per unit area of the transformer can not be increased any more, so the turns per volt of the primary coil are higher than the turns per volt of the primary voltage, but the secondary voltage of the transformer can not be increased along with the proportion of the primary stage, namely the secondary voltage can be balanced. If the primary voltage is further increased, the primary coil only generates heat, and the efficiency is not improved
The conventional circuit is adopted in the existing power supply design scheme, and the conventional analog IC has the advantages that the circuit is simple, and the working mode of the conventional analog IC is generally fixed to one of CCM (continuous working mode), BCM (critical working mode) and DCM (discontinuous working mode).
The CCM mode is suitable for high-power occasions, and has the advantages of small peak value of the inductive current and small volume of the magnetic element. The defects are that MOS loss is large, efficiency is not high, and a control mode is complex.
The BCM mode is suitable for being used in medium and small power occasions, and has the advantages of unfixed switching frequency, good EMC and simpler control mode. The disadvantage is that the inductor current peaks are large.
The DCM is suitable for being used in medium and small power occasions, and has the advantages that the waveform of the input current naturally follows the waveform of the input voltage, and the control mode is simple. The disadvantage is that the inductor current peaks are large.
In summary, the conventional analog IC single-mode circuit has different disadvantages, and cannot meet the requirements of high power density and small size. In order to synthesize the advantage of various mode, reduce the shortcoming of various mode, solve traditional mode and have that leakage current test specification exceeds standard, and ann's rule voltage exceeds standard, and signal power exceeds standard, and the transmission balance specification exceeds standard to and the transformer condition that magnetic saturation appears is proposed the utility model discloses the transformer is provided with the magnetic saturation's.
SUMMERY OF THE UTILITY MODEL
The utility model discloses an it is not enough to overcome above-mentioned condition, aims at providing the technical scheme that can solve above-mentioned problem.
In order to achieve the above object, the utility model provides a following technical scheme: a magnetic saturation control system for low-power transformer comprises
The input rectifying and filtering unit consists of a rectifying bridge stack BD1, a starting resistor R1 and a starting resistor R2 and is used for rectifying input alternating current into direct current and shaping sawtooth wave current at the rear end into a current waveform close to sinusoidal envelope;
the input filtering unit is used for smoothing filtering after rectification;
an output voltage detection unit composed of a resistor R9, a resistor R10, a resistor R13, a resistor R5, a resistor R6, a chip capacitor C6 and a chip capacitor C4 and used for detecting the output voltage of a sampling coil T1A of the transformer and the output voltage of a primary coil T1B of the transformer and providing feedback information;
the input detection control unit mainly comprises a singlechip U1, a chip diode D2, a capacitor C7, a resistor R7, a resistor R8 and a field-effect tube Q1, is used for detecting the input voltage waveform as a reference for frequency detection, finishing feedback acquisition and judgment of an output voltage signal, calculating according to the information, outputting different PWM (pulse width modulation) frequencies at an output end OUT of the singlechip U1 and controlling the light and heavy loads and the working mode of the input voltage;
the positive output end of the rectifier bridge stack BD1 is connected to an input end VCC with an internal ADC function on the single chip microcomputer U1 through a resistor string formed by a starting resistor R1 and a starting resistor R2; the input end of the input filtering unit is connected to the positive output end of the rectifier bridge stack BD 1; the input end of a primary coil T1B of the transformer is connected with the positive output end of a rectifier bridge stack BD1 through a common-mode inductor LF1, and a secondary coil T1C of the transformer is used for providing level for a post-stage circuit; the positive pole of the chip diode D2 is connected with the output end of a sampling coil T1A of the transformer through a resistor R7, the negative pole of the chip diode D2 is connected with a feedback end FB with an internal ADC function on the singlechip U1, the input end VCC of the singlechip U1 is grounded through a capacitor C7, and the grid of the field effect transistor Q1 is connected with the output end OUT with an internal PWM function on the singlechip U1 through a resistor R8; the resistor R9 and the resistor R10 are connected in series and then connected to two ends of a sampling coil T1A of the transformer, a voltage dividing point of the resistor R9 and the resistor R10 is connected with a feedback end FB of the single-chip microcomputer U1, a voltage dividing point of the resistor R9 and the resistor R10 is further connected with an input end of a sampling coil T1A of the transformer through a chip capacitor C4, one end of the resistor R5 and the resistor R6 which are connected in parallel is connected with a drain electrode of the field-effect transistor Q1, the other end of the resistor R9 is grounded, one end of the resistor R13 is connected with a feedback end CS with an internal ADC function on the single-chip microcomputer U1, the other end of the resistor R1 is connected with a drain electrode of the field-effect transistor Q1, one end of the chip capacitor C6 is connected with the feedback end CS of the single-chip microcomputer U1, and the other end of the chip capacitor is grounded.
As a further technical solution of the utility model: the input filtering unit consists of a filtering capacitor C1, a filtering capacitor C2, a resistor R3, a resistor R4, an absorption capacitor C3, an absorption capacitor C3A and a damping diode D1; the resistor R3, the resistor R4, the absorption capacitor C3 and the absorption capacitor C3A form a primary absorption loop.
As a further technical solution of the utility model: the secondary coil T1C of the transformer provides stable level for the post-stage circuit through an output filter unit, the output filter unit is composed of a diode D3, a diode D4, an electrolytic capacitor C9, a capacitor C11, a resistor R16 and a resistor R17; the diode D3 and the diode D4 are connected in parallel for rectification, and the resistor R16, the resistor R17 and the capacitor C11 form a secondary absorption loop.
Compared with the prior art, the beneficial effects of the utility model are as follows: the input voltage waveform is detected by the input rectifying and filtering unit to be used as the reference of frequency detection, the output condition of a primary coil T1B of the transformer and the output condition of a sampling coil T1A of the transformer are obtained by the output voltage detection unit and the input detection control unit, and the excitation power supply passing through the primary coil T1B of the transformer is controlled according to the conditions, the control mode is flexible and changeable, so that the transformer is prevented from being in a magnetic saturation state, and the problems that the leakage current test specification is over-standard, the safety voltage is over-standard, the signal power is over-standard and the transmission balance specification is over-standard in the traditional mode are solved through the circuit arrangement of the input rectifying and filtering unit, the input filtering unit and the transformer, and the efficiency of the control system is greatly improved.
Drawings
Fig. 1 is a schematic circuit diagram according to the present invention;
fig. 2 is a schematic block diagram of program modules loaded in a single chip microcomputer according to the present invention;
fig. 3 is a control flow chart according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Referring to FIGS. 1-3, a magnetic saturation control system for a transformer of a low power supply includes
The input rectifying and filtering unit consists of a rectifying bridge stack BD1, a starting resistor R1 and a starting resistor R2 and is used for rectifying input alternating current into direct current and simultaneously shaping sawtooth wave current at the rear end into a current waveform close to sinusoidal envelope;
the input filtering unit is used for smoothing filtering after rectification;
an output voltage detection unit consisting of a resistor R9, a resistor R10, a resistor R13, a resistor R5, a resistor R6, a patch capacitor C6 and a patch capacitor C4 and used for detecting the output voltage of a sampling coil T1A of the transformer and the output voltage of a primary coil T1B of the transformer and providing feedback information;
the input detection control unit mainly comprises a singlechip U1, a chip diode D2, a capacitor C7, a resistor R7, a resistor R8 and a field-effect tube Q1, is used for detecting the input voltage waveform as a reference for frequency detection, finishing feedback acquisition and judgment of an output voltage signal, calculating according to the information, outputting different PWM (pulse width modulation) frequencies at an output end OUT of the singlechip U1 and controlling the light and heavy loads and the working mode of the input voltage;
the positive output end of the rectifier bridge stack BD1 is connected to an input end VCC with an internal ADC function on the single chip microcomputer U1 through a resistor string formed by a starting resistor R1 and a starting resistor R2; the input end of the input filtering unit is connected to the positive output end of the rectifier bridge stack BD 1; the input end of a primary coil T1B of the transformer is connected with the positive output end of a rectifier bridge stack BD1 through a common-mode inductor LF1, and a secondary coil T1C of the transformer is used for providing level for a post-stage circuit; the positive pole of the chip diode D2 is connected with the output end of a sampling coil T1A of the transformer through a resistor R7, the negative pole of the chip diode D2 is connected with a feedback end FB with an internal ADC function on the singlechip U1, the input end VCC of the singlechip U1 is grounded through a capacitor C7, and the grid of the field effect transistor Q1 is connected with the output end OUT with an internal PWM function on the singlechip U1 through a resistor R8; the resistor R9 and the resistor R10 are connected in series and then connected to two ends of a sampling coil T1A of the transformer, a voltage dividing point of the resistor R9 and the resistor R10 is connected with a feedback end FB of the single chip microcomputer U1, a voltage dividing point of the resistor R9 and the resistor R10 is further connected with an input end of a sampling coil T1A of the transformer through a patch capacitor C4, one end of the resistor R5 and the resistor R6 after being connected in parallel is connected with a drain electrode of the field-effect tube Q1, the other end of the resistor R9 is grounded, one end of the resistor R13 is connected with a feedback end CS with an internal ADC function on the single chip microcomputer U1, the other end of the resistor R13 is connected with a drain electrode of the field-effect tube Q1, one end of the patch capacitor C6 is connected with the feedback end CS of the single chip microcomputer U1, and the other end of the patch capacitor C is grounded.
The input voltage waveform is detected by the input rectifying and filtering unit to be used as the reference of frequency detection, the output condition of a primary coil T1B of the transformer and the output condition of a sampling coil T1A of the transformer are obtained by the output voltage detection unit and the input detection control unit, and the excitation power supply passing through the primary coil T1B of the transformer is controlled according to the conditions, the control mode is flexible and changeable, so that the transformer is prevented from being in a magnetic saturation state, and the problems that the leakage current test specification is over-standard, the safety voltage is over-standard, the signal power is over-standard and the transmission balance specification is over-standard in the traditional mode are solved through the circuit arrangement of the input rectifying and filtering unit, the input filtering unit and the transformer, and the efficiency of the control system is greatly improved.
The working mode for controlling light and heavy loads and input voltage comprises the following steps:
step one, loading a voltage discrimination program module 101 with a voltage of more than 4.9V at an FB end, a voltage discrimination program module 102 with 2.5V-4.9V at the FB end, a voltage discrimination program module 103 with a voltage of less than 2.5V and not less than 1.5V at the FB end, a voltage discrimination program module 104 with a voltage of less than 1.5V at the FB end, a voltage discrimination program module 105 with a voltage of less than 0.7V at a CS end, a fixed frequency mode PWM output program module 106, a reduced frequency mode PWM output program module 108, an intermittent mode PWM output program module 109, an overcurrent protection program module 110, an overload protection program module 111 and a peak current control program module 107 in a program memory 11 of a singlechip U1, wherein the instructions of the program modules are suitable for being loaded and executed by a main control processor 12 of the singlechip U1;
the fixed frequency mode PWM output program module 106, the reduced frequency mode PWM output program module 108, and the intermittent mode PWM output program module 109 all set the on-time of the fet Q1, and the duty ratio of the fixed frequency mode conduction effector Q1 > the duty ratio of the reduced frequency mode conduction effector Q1 > the duty ratio of the intermittent mode conduction effector Q1;
the voltage discrimination program module 103 sets "decrease frequency" at the FB terminal at 2.5V or less and not less than 1.5V: when the voltage value of the FB end is lower than 2.5V, the duty ratio of the PWM conduction effect tube Q1 is synchronously reduced along with the reduction of the load;
electrifying two alternating current input ends of the rectifier bridge stack BD1, and detecting an input voltage waveform by the single chip microcomputer U1 through a VCC pin to be used as a reference for frequency detection;
step three, after the primary coil T1B of the transformer enters the working stage, detecting the output frequency, the output voltage of the sampling coil T1A of the detection transformer and the output voltage of the primary coil T1B of the detection transformer;
step four, when the voltage of the FB end is greater than 4.9V, starting an overload protection program module 111 to enable the system to work in an overload protection mode, and then turning to step nine;
step five, when the voltage of the FB end is not more than 4.9V and not less than 2.5V, starting a fixed frequency mode PWM output program module 106 and a peak current control program module 107 to enable the system to work in a fixed frequency mode, and then turning to the step nine;
step six, when the voltage of the FB end is less than 2.5V and not less than 1.5V, starting a frequency reduction mode PWM output program module 108 to enable the system to work in a frequency reduction mode, meanwhile, the system enters valley bottom conduction, the output frequency is synchronously reduced along with the reduction of the load, the system efficiency is improved, the output noise is reduced, and then the step nine is carried out;
step seven, when the voltage of the FB end is less than 1.5V, starting an intermittent mode PWM output program module 109 to enable the system to work in an intermittent mode, reducing power and output noise, and then turning to the step nine;
step eight, when the voltage of the CS pin is less than 0.7V, starting an over-current protection program module 110 to enable the system to work in an over-current protection mode, and then turning to the step nine;
step nine, continuously operating, and turning to step three; if the operation is stopped, turning to the step ten;
and step ten, finishing.
The input voltage waveform is detected to be used as a reference for frequency detection, then the output condition of the primary coil T1B of the transformer and the output condition of the sampling coil T1A of the transformer are detected, obtained and judged, and meanwhile, calculation is carried out according to the information, so that the excitation power supply passing through the primary coil T1B of the transformer is controlled, and the transformer is prevented from being in a magnetic saturation state.
The output condition of the primary coil T1B of the transformer is an output voltage signal, and the output condition of the sampling coil T1A of the transformer comprises the output voltage signal, and the output condition of the sampling coil T1A of the transformer also comprises an output frequency signal through the circuit arrangement of the chip diode D2 and the resistor R7, so that the input end VCC of the singlechip U1 can obtain better frequency feedback, and the PWM output is more accurate.
The traditional analog integrated circuit is replaced by a programmable intelligent master control single-chip microcomputer, multi-mode PWM is intelligently output, and overload protection and overcurrent protection are realized, so that the control mode of controlling the excitation power supply passing through the primary coil T1B of the transformer is more intelligent and diversified. The control mode comprises an overload protection mode, an overcurrent protection mode, a fixed frequency conduction mode, a frequency reduction conduction mode and an intermittent conduction mode, wherein the frequency reduction conduction mode and the intermittent conduction mode correspondingly reduce the output frequency along with the reduction of the load, and the condition that the transformer avoids magnetic saturation under various conditions can be better met.
The voltage discrimination program module 103 sets "decrease frequency" at the FB terminal at 2.5V or less and not less than 1.5V: when the voltage value of the feedback terminal FB is lower than 2.5V, the duty ratio of the PWM conduction effect transistor Q1 is reduced by 10% every time the voltage value is decreased by 0.1V.
The input filtering unit consists of a filtering capacitor C1, a filtering capacitor C2, a resistor R3, a resistor R4, an absorption capacitor C3, an absorption capacitor C3A and a damping diode D1; the resistor R3, the resistor R4, the absorption capacitor C3 and the absorption capacitor C3A form a primary absorption loop.
The secondary coil T1C of the transformer provides stable level for the post-stage circuit through an output filter unit, the output filter unit is composed of a diode D3, a diode D4, an electrolytic capacitor C9, a capacitor C11, a resistor R16 and a resistor R17; the diode D3 and the diode D4 are connected in parallel for rectification, and the resistor R16, the resistor R17 and the capacitor C11 form a secondary absorption loop.
It is obvious to a person skilled in the art that the invention is not restricted to details of the above-described exemplary embodiments, but that it can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (3)
1. A magnetic saturation control system of a low-power transformer is characterized by comprising
The input rectifying and filtering unit consists of a rectifying bridge stack BD1, a starting resistor R1 and a starting resistor R2 and is used for rectifying input alternating current into direct current and shaping sawtooth wave current at the rear end into a current waveform close to sinusoidal envelope;
the input filtering unit is used for smoothing filtering after rectification;
an output voltage detection unit consisting of a resistor R9, a resistor R10, a resistor R13, a resistor R5, a resistor R6, a patch capacitor C6 and a patch capacitor C4 and used for detecting the output voltage of a sampling coil T1A of the transformer and the output voltage of a primary coil T1B of the transformer and providing feedback information;
the input detection control unit mainly comprises a singlechip U1, a chip diode D2, a capacitor C7, a resistor R7, a resistor R8 and a field-effect tube Q1, is used for detecting the input voltage waveform as a reference for frequency detection, finishing feedback acquisition and judgment of an output voltage signal, calculating according to the information, outputting different PWM (pulse width modulation) frequencies at an output end OUT of the singlechip U1 and controlling the light and heavy loads and the working mode of the input voltage;
the positive output end of the rectifier bridge stack BD1 is connected to an input end VCC with an internal ADC function on the single chip microcomputer U1 through a resistor string formed by a starting resistor R1 and a starting resistor R2; the input end of the input filtering unit is connected to the positive output end of the rectifier bridge stack BD 1; the input end of a primary coil T1B of the transformer is connected with the positive output end of a rectifier bridge stack BD1 through a common-mode inductor LF1, and a secondary coil T1C of the transformer is used for providing level for a post-stage circuit; the positive pole of the chip diode D2 is connected with the output end of a sampling coil T1A of the transformer through a resistor R7, the negative pole of the chip diode D2 is connected with a feedback end FB with an internal ADC function on the singlechip U1, the input end VCC of the singlechip U1 is grounded through a capacitor C7, and the grid of the field effect transistor Q1 is connected with the output end OUT with an internal PWM function on the singlechip U1 through a resistor R8; the resistor R9 and the resistor R10 are connected in series and then connected to two ends of a sampling coil T1A of the transformer, a voltage dividing point of the resistor R9 and the resistor R10 is connected with a feedback end FB of the single chip microcomputer U1, a voltage dividing point of the resistor R9 and the resistor R10 is further connected with an input end of a sampling coil T1A of the transformer through a patch capacitor C4, one end of the resistor R5 and the resistor R6 after being connected in parallel is connected with a drain electrode of the field-effect tube Q1, the other end of the resistor R9 is grounded, one end of the resistor R13 is connected with a feedback end CS with an internal ADC function on the single chip microcomputer U1, the other end of the resistor R13 is connected with a drain electrode of the field-effect tube Q1, one end of the patch capacitor C6 is connected with the feedback end CS of the single chip microcomputer U1, and the other end of the patch capacitor C is grounded.
2. The magnetic saturation control system of a small power supply transformer according to claim 1, wherein the input filter unit is composed of a filter capacitor C1, a filter capacitor C2, a resistor R3, a resistor R4, an absorption capacitor C3, an absorption capacitor C3A, and a damping diode D1;
the resistor R3, the resistor R4, the absorption capacitor C3 and the absorption capacitor C3A form a primary absorption loop.
3. The magnetic saturation control system of a small power supply transformer according to claim 1, wherein the secondary winding T1C of the transformer provides a stable level for the following circuit through an output filter unit, the output filter unit is composed of a diode D3, a diode D4, an electrolytic capacitor C9, a capacitor C11, a resistor R16 and a resistor R17;
the diode D3 and the diode D4 are connected in parallel for rectification, and the resistor R16, the resistor R17 and the capacitor C11 form a secondary absorption loop.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202221225759.6U CN217362912U (en) | 2022-05-19 | 2022-05-19 | Magnetic saturation control system of low-power transformer |
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| CN202221225759.6U CN217362912U (en) | 2022-05-19 | 2022-05-19 | Magnetic saturation control system of low-power transformer |
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