CN111224533A - Automatic current sharing circuit and method for negative temperature diode - Google Patents
Automatic current sharing circuit and method for negative temperature diode Download PDFInfo
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- CN111224533A CN111224533A CN201911226948.8A CN201911226948A CN111224533A CN 111224533 A CN111224533 A CN 111224533A CN 201911226948 A CN201911226948 A CN 201911226948A CN 111224533 A CN111224533 A CN 111224533A
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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
-
- 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
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
- H02M7/068—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode mounted on a transformer
Abstract
The invention discloses an autonomous current sharing circuit and method for negative temperature diodes, which are applied to the field of high-power converters. The direct output of a group of windings of the power conversion transformer is realized, and the output rectifier diodes can be directly connected in parallel for use. A very good current sharing effect is achieved. The current sharing of the diodes can be achieved, only one group of windings is needed in the secondary side of the power transformer, the winding process of the transformer is greatly simplified, and the wiring of a PCB is simplified.
Description
Technical Field
The invention relates to the field of high-power converters, in particular to an autonomous current sharing circuit and a current sharing method for a negative temperature diode.
Background
In a high-power converter, a commercially-available ultrafast recovery diode with negative temperature coefficient characteristics cannot be used in parallel, and the current sharing characteristics are poor. For example, in a switching power supply, a rectifying diode at an output end is usually a rectifying diode with a negative temperature coefficient, and when the switching power supply works in parallel, the temperature of the diode with larger current is increased, so that the conduction voltage drop is reduced, the working current is higher, the diode enters a positive feedback state, and finally thermal breakdown is caused, so that the diode cannot be directly used in parallel.
Therefore, to realize parallel output, only a power transformer with multiple windings with a set of bridges can be used, and the parallel output is performed after rectification. However, even in this case, the current equalizing effect is still not good due to the discreteness of the additional impedance of the transformer, which may seriously degrade the current stress of the diode and reduce the reliability of the diode. Meanwhile, the winding process of the transformer is complex, and the PCB wiring of the transformer is also complex.
Disclosure of Invention
In order to solve the above problems, the present invention provides an autonomous current sharing circuit for a negative temperature diode and a current sharing method thereof, so that an output rectifier diode can be directly connected in parallel to use the negative temperature diode, and a good current sharing effect is achieved.
In order to achieve the purpose, the technical scheme of the invention is as follows: an automatic current equalizing circuit of negative temperature diode, comprising: two or more than two diodes which are used in parallel, and a group of common mode inductors are arranged between the diodes which are used in parallel, so that reverse hedging current is formed between each diode, and when the hedging current has different magnitude, equivalent common mode current can be formed, so that the independent current sharing of the diodes is realized by utilizing common mode impedance.
Preferably, the common mode inductor is wound on the same magnetic core, and the coil diameters and the coil numbers of the two windings are the same, but the winding directions are opposite. And the parallel diodes can be two, one end of each diode is connected, the other end of each diode is connected to two terminals at one end of the common mode inductor respectively, and the two terminals at the other end of each common mode inductor are in short circuit, so that the parallel diodes and the inductors connected with the diodes form a parallel diode group with a current sharing measure.
Meanwhile, it is preferable that the parallel diode groups may be applied to a bridge rectifier circuit, the number of the common mode inductors is two, the short-circuited terminals of the common mode inductors are respectively connected to two ends of the secondary side of the transformer, and the parallel diode groups on two arms connected to each input end of the rectifier bridge share one common mode inductor.
Furthermore, the parallel diode groups are applied to a bridge rectifier circuit, the number of the common-mode inductors is two, the short-circuit terminals of the common-mode inductors are respectively connected with two ends of a rectifier load, and the parallel diode groups on two arms connected with each output end of the rectifier bridge share one common-mode inductor.
In addition, the scheme can be further expanded, namely: the parallel connection uses more than three diodes, each two paths of diode current are equalized through a common mode inductor, and then all the paths are mutually coupled to realize the consistency of all the currents.
Preferably, the magnetic core may be a ferrite magnetic ring to improve efficiency.
The invention also provides an autonomous current sharing method of the parallel negative temperature diode, which comprises the following steps: when at least 2 negative temperature diodes are used in parallel, a group of common mode inductors are added between the secondary of the transformer and the diodes, reverse hedging current is formed between each diode, and when the hedging current has different magnitudes, equivalent common mode current is formed, so that the independent current sharing of the diodes is realized by utilizing common mode impedance.
Further the method can be further expanded: when more than three diodes are used in parallel, the current of each two channels of the diodes is equalized by a common-mode inductor, and then the channels are coupled with each other to realize the consistency of the current.
In addition, when multiple paths are connected in parallel, the circuit connection is complex, and in order to simplify the application design of the complex schematic diagram, the invention further provides the following scheme: the common mode inductor is arranged and connected by adopting an intensive design structure which saves the use space and reduces the product volume.
The invention has the beneficial effects that by means of the technical scheme, the direct group of winding output of the power conversion transformer is realized, and the output rectifier diodes can be directly connected in parallel for use. The effect of good current equalizing effect is realized. The current sharing of the diodes can be achieved, only one group of windings is needed in the secondary side of the power transformer, the winding process of the transformer is greatly simplified, and the wiring of a PCB is simplified.
Drawings
FIG. 1 is a schematic circuit diagram of the present invention;
FIG. 2 is a typical current-voltage characteristic of the diode;
FIGS. 3a and 3b are two parallel diode test circuits with current sharing measure added and two parallel diode test circuits without current sharing measure in a conventional state, respectively;
FIG. 4 is a diode current waveform for the two circuits of FIG. 3;
FIG. 5 is a schematic diagram of the circuit of the present invention using three parallel tubes;
fig. 6 is a running line diagram of the coupling inductor during four-way parallel current sharing according to the present invention.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.
The main idea of the implementation scheme of the invention is to add a group of common-mode inductors between the secondary of the transformer and the diodes to form reverse hedging current between each diode, when the hedging current has different magnitude, equivalent common-mode current can be formed, and at the moment, the autonomous current sharing of the diodes is realized by utilizing common-mode impedance. In the present invention, the negative temperature diode refers to a diode having a characteristic that conduction voltage drop decreases with increase of junction temperature.
As shown in fig. 1, when a reverse current flows into the same-name end of a single common mode ring, the magnetic flux of the corresponding magnetic circuit is offset to zero, and no impedance is presented to the outside. In the same reason, when the current flows into the different name end in the same direction, the impedance is not displayed.
When the currents I1 and I2 in fig. 1 are the same in magnitude and direction, the internal magnetic field of the common mode inductor in the drawing is offset, which is equivalent to a wire, and when the impedances of the loops where the currents I1 and I2 are located are unequal, the two currents tend to deviate, so that the magnetic field at the midpoint of the common mode inductor cannot be offset, and the generated induced voltage just resists the external voltage causing the current deviation.
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Since the resistance in fig. 1 can be analogized to the equivalent resistance of the diode, and the actual typical current-voltage characteristic curve of the negative temperature coefficient diode is shown in fig. 2, it can be seen from fig. 2 that the turn-on threshold voltage and the internal resistance of the conventional diode both decrease with the increase of the temperature in the normal use temperature range. According to the data of the figure, the conduction threshold voltage is 0.75V and the internal resistance is 37.5m omega when the junction temperature is 125 ℃. The junction temperature is 25 ℃, the conduction threshold is 0.9V, and the internal resistance is 45m omega. Considering that the possibility that the actual temperature difference of the diode exceeds 100 ℃ is extremely low, the current sharing measure can correct the diode under the parameter deviation, and the stability of mass production of products can be ensured.
For the above parameters, when the conduction current is 20A, the calculation shows that the voltage difference of the diodes is 0.3V, so the current sharing measure only needs to compensate the voltage difference, and meanwhile, because the connection of the same-name terminals is reversed, only half of the voltage, namely 0.15V, is actually needed for each winding to induce. In addition, because the passive autonomous current sharing is adopted, the current error cannot be thoroughly eliminated, but the passive autonomous current sharing circuit has the advantages of being stable and reliable in circuit and low in energy consumption, the current deviation can be guaranteed to be 10% in practical engineering application, so that the deviation current is about 2A, and the required equivalent impedance is 75m omega when the deviation current is considered together with the winding voltage of 0.15V.
For practical engineering applications, the coupling inductor core is made of ferrite beads, and in this embodiment, the ferrite beads are selected as small-sized high-permeability type H10/6/5, and the inductance factor is 5100nH/N ^2, so that the inductance of a single turn is 5.1 uH. And considering that the switching frequency of the high-frequency switching power supply is at least 20kHz, the single-turn impedance of the high-frequency switching power supply is expressed as Z-2 pi fL. When the default frequency f is 20k and L is 5.1u, the obtained inductive impedance is about 640m Ω. It is obvious that the impedance is improved to meet the minimum impedance of 75m omega which is required by the practical, and the reliability of mass production can be met, so that a magnetic core with smaller volume is not further used, and the requirement of the practical insulation process can not be met due to the small size.
As shown in fig. 3a and fig. 3b, the two parallel diode circuits with the current equalizing circuit and without the current equalizing circuit in the conventional state are different in the difference between the two parallel diode circuits with the above difference parameters. Fig. 3 is a typical bridge rectifier circuit employing two parallel diodes per arm.
Referring to fig. 3a, it is a self-current-sharing circuit of negative temperature diode with current-sharing measure of the present invention, the current-sharing measure is to add a set of common mode inductors, that is, the bridge rectifier circuit adds a common mode inductor at two input ends, respectively, the common mode inductors are wound on the same magnetic core, and the coil diameters and the coil numbers of the two windings are the same, but the winding directions are opposite, one end of the parallel diodes is connected, and the other end is connected to two terminals at one end of the common mode inductor, respectively, the two terminals at the other end of each common mode inductor are short-circuited, so that the parallel diodes and the inductors connected therewith constitute a parallel diode set with current-sharing measure.
In fig. 3, by means of the current equalizing measure, I1 and I2 currents can be made to be substantially the same, while I3 and I4 are in an unprocessed state, and due to the discreteness of diode parameters, it can be found that the current difference between the two currents reaches about 3 times, and the measured specific diode current waveform can be seen in fig. 4.
In addition, the circuit can be further expanded, 3 or more than 3 diodes can be connected in parallel, the principle is that the current of the diodes is equalized in every two paths, and then the paths are mutually coupled to realize the consistency of the current. The specific circuit is shown in detail in fig. 5, which is a schematic circuit diagram of the present invention when three parallel tubes are used.
Similarly, according to the circuit principle when the three tubes are connected in parallel, the parallel current sharing of more diodes can be realized by the analogy. The iteration rule of the parallel connection of the multiple pipes is as follows: the 1 st homonymous terminal on the input side of the common mode inductor is connected to the 2 nd homonymous terminal on the output side of the common mode inductor, the 2 nd homonymous terminal on the input side of the common mode inductor is connected to the 3 rd homonymous terminal on the output side of the common mode inductor, and so on, the n-1 st homonymous terminal on the input side of the common mode inductor is connected to the nth homonymous terminal on the output side of the common mode inductor, and finally the nth homonymous terminal on the input side of the common mode inductor is connected back to the 1 st homonymous terminal on the output side of the common mode inductor, so that the n homonymous terminals which are not connected on the input side of the common mode ring can be connected together to be used as a total current input end, and the n homonymous terminals which are not connected on the output side of the common mode ring are respectively connected to be used as current. And the current equalizing circuit can also be applied to a full-wave rectifying circuit adopting a center tap type.
In addition, because the circuit connection is complex when multiple paths are connected in parallel, in order to simplify the application design of the complex schematic diagram, the embodiment of the present invention adopts the scheme shown in fig. 6 to implement intensive design. Fig. 6 is a wiring diagram of the coupling inductor when four parallel current sharing are adopted in the invention, and as shown in the figure, the wiring using the structure shown in fig. 6 can effectively save the use space and reduce the product volume. In this embodiment, in specific use, as shown in fig. 6, pins No. 1, 3, 5, and 7 may be commonly connected to one lead terminal of the secondary winding of the transformer, and pins No. 2, 4, 6, and 8 may be respectively connected to the middle nodes of the 4-transistor parallel diode group, so that the passive self current equalizing effect of the diodes may be achieved when the circuit operates.
Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention.
Claims (10)
1. An automatic current equalizing circuit of negative temperature diode, comprising: two or more than two diodes which are used in parallel, and a group of common mode inductors are arranged between the diodes which are used in parallel, so that reverse hedging current is formed between each diode, and when the hedging current has different magnitude, equivalent common mode current can be formed, so that the independent current sharing of the diodes is realized by utilizing common mode impedance.
2. The isothermal diode autonomous current sharing circuit according to claim 1, wherein the common mode inductor is wound on the same core, and the coil diameter and the number of turns of the two windings are the same, but the winding directions are opposite.
3. The self-current-sharing circuit of claim 2, wherein the number of the diodes connected in parallel is two, one end of the diodes is connected to the other end of the diodes, the other end of the diodes is connected to two terminals of one end of the common-mode inductor, and two terminals of the other end of each common-mode inductor are short-circuited, so that the diodes connected in parallel and the inductors connected to the diodes form a parallel diode group with current sharing measures.
4. The self-current-sharing circuit of claim 3, wherein: the parallel diode groups are applied to a bridge rectifier circuit, the number of the common-mode inductors is two, short-circuit terminals of the common-mode inductors are respectively connected with two ends of a secondary side of the transformer, and the parallel diode groups on two arms connected with each input end of the rectifier bridge share one common-mode inductor.
5. The self-current-sharing circuit of claim 3, wherein: the parallel diode groups are applied to a bridge rectifier circuit, the number of the common-mode inductors is two, short-circuit terminals of the common-mode inductors are respectively connected with two ends of a rectifier load, and the parallel diode groups on two arms connected with each output end of the rectifier bridge share one common-mode inductor.
6. The self-current-sharing circuit of claim 2, wherein the number of the diodes connected in parallel is more than three, the current of the diodes is shared by a common-mode inductor in each two paths, and then the two paths are coupled to each other to realize the consistency of the current.
7. The isothermal diode autonomous current sharing circuit according to any of claims 2-6, wherein a ferrite bead is used as the magnetic core.
8. An autonomous current sharing method of negative temperature diodes for parallel connection is characterized in that: when at least 2 negative temperature diodes are used in parallel, a group of common mode inductors are added between the secondary of the transformer and the diodes, reverse hedging current is formed between each diode, and when the hedging current has different magnitudes, equivalent common mode current is formed, so that the independent current sharing of the diodes is realized by utilizing common mode impedance.
9. The method for autonomous current sharing of the parallel negative temperature diodes according to claim 8, wherein: when more than three diodes are used in parallel, the current of each two channels of the diodes is equalized by a common-mode inductor, and then the channels are coupled with each other to realize the consistency of the current.
10. The method for autonomous current sharing of the parallel negative temperature diodes according to claim 9, wherein: the common mode inductor is arranged and connected by adopting an intensive design structure which saves the use space and reduces the product volume.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911226948.8A CN111224533A (en) | 2019-12-04 | 2019-12-04 | Automatic current sharing circuit and method for negative temperature diode |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911226948.8A CN111224533A (en) | 2019-12-04 | 2019-12-04 | Automatic current sharing circuit and method for negative temperature diode |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3018380A (en) * | 1958-10-31 | 1962-01-23 | Westinghouse Electric Corp | Current balancing apparatus |
| JPS57132730A (en) * | 1981-02-05 | 1982-08-17 | Tokyo Shibaura Electric Co | Current balancing method |
| CN101145477A (en) * | 2007-08-14 | 2008-03-19 | 华中科技大学 | Parallel circuit breaker |
| CN102497086A (en) * | 2011-11-30 | 2012-06-13 | 华为技术有限公司 | Parallel current-equalizing circuit |
| US20160079888A1 (en) * | 2014-09-17 | 2016-03-17 | Regal Beloit America, Inc. | System and method for controlling a motor |
| CN107453740A (en) * | 2017-09-30 | 2017-12-08 | 华北电力大学 | A kind of circuit for improving the distribution of power semiconductor parallel-current |
-
2019
- 2019-12-04 CN CN201911226948.8A patent/CN111224533A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3018380A (en) * | 1958-10-31 | 1962-01-23 | Westinghouse Electric Corp | Current balancing apparatus |
| JPS57132730A (en) * | 1981-02-05 | 1982-08-17 | Tokyo Shibaura Electric Co | Current balancing method |
| CN101145477A (en) * | 2007-08-14 | 2008-03-19 | 华中科技大学 | Parallel circuit breaker |
| CN102497086A (en) * | 2011-11-30 | 2012-06-13 | 华为技术有限公司 | Parallel current-equalizing circuit |
| US20160079888A1 (en) * | 2014-09-17 | 2016-03-17 | Regal Beloit America, Inc. | System and method for controlling a motor |
| CN107453740A (en) * | 2017-09-30 | 2017-12-08 | 华北电力大学 | A kind of circuit for improving the distribution of power semiconductor parallel-current |
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