CN214256140U

CN214256140U - Active clamping flyback bidirectional DC/DC circuit

Info

Publication number: CN214256140U
Application number: CN202120449699.5U
Authority: CN
Inventors: 孙照明
Original assignee: Mingzhilan Jiangsu Electronic Technology Co ltd
Current assignee: Mingzhilan Jiangsu Electronic Technology Co ltd
Priority date: 2021-03-02
Filing date: 2021-03-02
Publication date: 2021-09-21
Anticipated expiration: 2031-03-02

Abstract

The utility model relates to the technical field of converters, a flyback bidirectional DC/DC circuit with active clamping is disclosed, which comprises a transformer T1, an input end Vi and an output end Vo, wherein an input circuit is connected between the input end Vi and the primary side of a transformer T1, and an output circuit is connected between the secondary side of the transformer T1 and the output end Vo; the input circuit comprises an input capacitor Ci, a controllable switch tube S1 and a first active clamping circuit, wherein the input capacitor Ci, the controllable switch tube S1 and the first active clamping circuit are sequentially connected with an input end Vi in series; the output circuit comprises an output capacitor Co, a controllable switch tube S2 and a second active clamping circuit which are sequentially connected with the output end Vo in series, and the first active clamping circuit and the second active clamping circuit both comprise a capacitor and a controllable switch tube which are sequentially connected in series. Compared with the prior art, the utility model discloses on current solution's basis, change passive active clamp circuit's diode into controllable switch pipe, can solve the transformer leakage inductance problem, optimize output side current waveform, realize output side switch pipe ZCS and reduce the electric current virtual value, can raise the efficiency.

Description

Active clamping flyback bidirectional DC/DC circuit

Technical Field

The utility model relates to a power electronic converter technical field, concretely relates to active clamp's flyback bidirectional DC circuit for the efficient two-way flow of miniwatt energy in the realization.

Background

The traditional ideal flyback circuit (the transformer is perfectly coupled without leakage inductance) is an ideal isolated bidirectional DC/DC topology, both sides can work in a wide working voltage range, and both sides can freely step up and down; this is explained in detail in US 6788555. But due to the existence of leakage inductance (perfect coupling of an actual transformer is impossible), the problems of efficiency reduction, peak of a switching device and the like can be caused, and because of the existence of the core problem, the isolated bidirectional DC/DC topology has not been realized in wide industry application.

The bidirectional DC/DC topology (part of which is shown in the table) commonly used in the industry is generally suitable for isolated bidirectional DC/DC with medium and high power, and is generally characterized in that the number of used power semiconductors is large, the number of power electromagnetic elements is large, and the core problem caused by the fact that the cost is high is not suitable for isolated bidirectional DC/DC occasions with medium and low power; and another problem commonly existing in the topologies is that the working voltage range depends on the transformer transformation ratio and peripheral parameters, the working voltage range is narrow, and the solution of CN200680017589 is to use a two-stage topology, which further increases the cost and reduces the competitiveness.

In the traditional flyback topology, absorption circuits are added to circuits on two sides of a transformer, referring to fig. 1, the absorption circuits on two sides of the transformer in fig. 1 all use RCD absorption circuits, as can be seen from fig. 1, circuits on a primary side (a left side, a circuit connected with pins 1 and 2 of T1) and circuits on a secondary side (a right side, a circuit connected with pins 3 and 4 of T1) are symmetrical, and only the connection of the same-name ends of the transformer is reversed, assuming that control energy flows from left to right, a main switch tube S1 is excited first, energy stored in the transformer after S1 is turned off pushes a body diode of S2 through, and at the moment, ZVS conduction of S2 can be realized by conducting S2 along with the current; when the energy of the transformer is completely output, the current of the S2 is reduced to zero, and at this time, if the S2 is continuously kept on, the transformer is excited in a reverse direction for a little, and then the S2 is closed, the energy stored by the transformer can enable the body diode of the main switch tube S1 to be connected, and then the S1 is conducted along the same potential, so that the ZVS conduction of the main switch tube S1 is realized. This can reduce the turn-on loss of S1, increasing the efficiency of the converter to some extent. However, the most fundamental problem in the above conventional solutions is the efficiency loss due to the leakage inductance of the transformer and the EMI problem due to the waveform deterioration. Moreover, the existing converter basically works in a fixed frequency state (Vds 1 or Vds2 has a period of oscillation, and the duty ratio is low).

SUMMERY OF THE UTILITY MODEL

Utility model purpose: to the problem that exists among the prior art, the utility model provides a two-way DC circuit of flyback of active clamp, on current solution 'S basis, change passive absorption circuit' S diode into controllable switch pipe (S3 and S4) to increase a large amount of control optimization, can solve the transformer leakage inductance problem, optimize output side current waveform, realize output side switch pipe ZCS and reduce the electric current virtual value, can raise the efficiency.

The technical scheme is as follows: the utility model provides a flyback bidirectional DC/DC circuit with active clamping, which comprises a transformer T1, an input end Vi and an output end Vo, wherein an input circuit is connected between the input end Vi and a primary side of a transformer T1, and an output circuit is connected between a secondary side of the transformer T1 and the output end Vo; the input circuit comprises an input capacitor Ci, a controllable switch tube S1 and a first active clamping circuit which are sequentially connected with an input end Vi in series, wherein the first active clamping circuit is connected with a primary winding of the transformer T1 in parallel and is connected with the input end Vi; the output circuit comprises an output capacitor Co, a controllable switch tube S2 and a second active clamping circuit which are sequentially connected with an output end Vo in series, the second active clamping circuit is connected with a secondary winding of the transformer T1 in parallel, the first active clamping circuit and the second active clamping circuit both comprise a capacitor and a controllable switch tube which are sequentially connected in series, the controllable switch tube of the first active clamping circuit is a controllable switch tube S3, and the controllable switch tube S4 of the second active clamping circuit is connected with a power supply.

Furthermore, the pins of the primary winding of the transformer T1 are pins 1 and 2, the secondary winding thereof is pins 3 and 4, and the pins 2 and 3 are terminals of the same name.

Further, the first active clamp circuit includes a capacitor C1 and a controllable switch tube S3, the capacitor C1 is connected in series with the controllable switch tube S3, the capacitor C1 is disposed near the input Vi or the capacitor C1 is connected in series between the controllable switch tube S1 and the controllable switch tube S3.

Further, the second active clamp circuit includes a capacitor C2 and a controllable switch tube S4, the capacitor C2 is connected in series with the controllable switch tube S4, the capacitor C2 is disposed close to the input Vo, or the capacitor C2 is connected in series between the controllable switch tube S2 and the controllable switch tube S4.

Further, the controllable switch tube S1, the controllable switch tube S2, the controllable switch tube S3, and the controllable switch tube S4 each include a driver, a body diode, and an output node capacitor, and the body diode and the output node capacitor are connected in parallel.

Further, when energy flows from the primary side of the transformer T1 to the secondary side of the transformer T1, the driving DRV1 of the controllable switch tube S1 and the driving DRV3 of the controllable switch tube S3 are complementary drives, the driving DRV2 of the controllable switch tube S2 realizes synchronous rectification, and the driving DRV4 of the controllable switch tube S4 is always at a low level;

when energy flows from the secondary side of the transformer T1 to the primary side of the transformer T1, the drive DRV2 of the controllable switch tube S2 and the drive DRV4 of the controllable switch tube S4 are complementary drives, the drive DRV1 of the controllable switch tube S1 realizes synchronous rectification, and the drive DRV3 of the controllable switch tube S3 is always at a low level.

Further, the controllable switch tubes S1, S2, S3, S4 are IGBTs, MOSFETs, SiC MOSFETs or GaN MOS.

Has the advantages that:

1. the utility model discloses can solve the transformer leakage inductance problem, reduce and do not have the peak even, raise the efficiency, optimize the EMI performance.

2. The utility model discloses optimized output side current waveform, changed the waveform of output side into similar sinusoidal half-wave from the triangle wave, realized output side switch tube Zero Current Switch (ZCS) and reduce the electric current virtual value, can raise the efficiency.

3. In the existing scheme, the converter basically works in the state of deciding frequently, controllable switch tube S1 and active clamp circuit between one or controllable switch tube S2 and active clamp circuit two (Vds 1 or Vds2 have a period of time to vibrate, the duty cycle utilization ratio is low), and the utility model discloses the circuit mainly works in the frequency conversion state, and operating frequency is along with input voltage, output power change, and Vds1 or Vds2 can not have the time of vibration, and the duty cycle utilization ratio is high, and efficiency further improves.

4. The utility model discloses possess better engineering practicality, can obtain higher efficiency and littleer power density. The method is particularly suitable for the occasions of medium and small power isolation bidirectional DC/DC.

Drawings

Fig. 1 is a schematic diagram of a conventional flyback topology circuit in the prior art;

fig. 2 is a schematic circuit diagram of embodiment 1 of the present invention;

fig. 3 is a schematic circuit diagram of embodiment 2 of the present invention;

fig. 4 is a schematic circuit diagram of embodiment 3 of the present invention;

fig. 5 is a schematic circuit diagram of embodiment 4 of the present invention;

fig. 6 is a steady-state waveform diagram of each key point when the energy flows from the primary side of the transformer to the secondary side of the transformer in embodiment 1 of the present invention.

Detailed Description

The present invention will be further described with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

For the technical solution in the background art, referring to fig. 1, the absorption circuits on both sides of the transformer use RCD absorption circuits, and energy stored by the leakage inductance on the primary side of the transformer is transferred to the capacitor C1 and absorbed by the R1, so that the RCD absorption circuits function to cause the low efficiency of the conventional flyback topology.

Example 1:

the utility model discloses a flyback bidirectional DC/DC circuit with active clamping, which comprises a transformer T1, an input end Vi and an output end Vo, wherein an input circuit is connected between the input end Vi and the primary side of a transformer T1, and an output circuit is connected between the secondary side of the transformer T1 and the output end Vo; the input circuit comprises an input capacitor Ci, a controllable switch tube S1 and a first active clamping circuit which are sequentially connected with an input end Vi in series, wherein the first active clamping circuit is connected with a primary winding of a transformer T1 in parallel and is connected with the input end Vi; the output circuit comprises an output capacitor Co, a controllable switch tube S2 and a second active clamping circuit which are sequentially connected with the output end Vo in series, the second active clamping circuit is connected with a secondary winding of the transformer T1 in parallel, and the first active clamping circuit and the second active clamping circuit both comprise a capacitor and a controllable switch tube which are sequentially connected in series.

The utility model discloses on current solution technical scheme basis, the diode among the passive absorption circuit changes controllable switch pipe into.

The transformation ratio of the transformer T1 is n, the pins of the primary winding are 1 pin and 2 pins, the pins of the secondary winding are 3 pins and 4 pins, and the 2 pins and the 3 pins are homonymous terminals.

The first active clamp circuit comprises a capacitor C1 and a controllable switch tube S3, a capacitor C1 is connected with the controllable switch tube S3 in series, the capacitor C1 is arranged close to an input end Vi, the second active clamp circuit comprises a capacitor C2 and a controllable switch tube S4, the capacitor C2 is connected with the controllable switch tube S4 in series, and a capacitor C2 is arranged close to an input end Vo, see the attached figure 2.

The controllable switch tube S1, the controllable switch tube S2, the controllable switch tube S3, and the controllable switch tube S4 all include a driver, a body diode, and an output node capacitor, and the body diode and the output node capacitor are connected in parallel. The controllable switching tubes S1, S2, S3 and S4 are IGBTs, MOSFETs, SiC MOSFETs or GaN MOS.

When energy flows from the primary side of the transformer T1 to the secondary side of the transformer T1, the driving DRV1 of the controllable switch tube S1 and the driving DRV3 of the controllable switch tube S3 are driven complementarily, the driving DRV2 of the controllable switch tube S2 realizes synchronous rectification, and the driving DRV4 of the controllable switch tube S4 is always at a low level.

The operation of the transformer T1 from the primary side of the transformer T1 to the secondary side of the transformer T1 is described in detail with reference to fig. 6:

in fig. 6, "Vc 1-Vds 1" Is a voltage waveform on both sides of a controllable switching tube S3, Vds1 Is a voltage waveform on both sides of a controllable switching tube S1, DRV3 Is a drive of a controllable switching tube S3, DRV1 Is a drive of a controllable switching tube S1, Ip Is a primary side current of a transformer T1 (pin 1 in pin 2 out positive), Is a secondary side current of the transformer T1 (pin 4 in pin 3 out positive), and Imag Is a primary side excitation current equivalent to the transformer T1, and Is equal to "Ip + Is/n" (n Is a transformation ratio of the transformer T1).

1) t0-t 1: when the last cycle is over, before DRV3 of the controllable switch S3 changes from high to low, transformer T1 has a negative current (I2, flowing from pin 2 and flowing from pin 1), where the negative current flows as: pin 2 of transformer T1 → pin 1 of transformer T1 → capacitor C1 → controllable switching tube → pin 2 of transformer T1. After time t0, the controllable switch S3 is turned off, and the negative current flow direction changes to: pin 2 of transformer T1 → pin 1 of transformer T1 → input capacitor Ci → controllable switch tube S1 → pin 2 of transformer T1, which will draw away the charge on the output node capacitor of controllable switch tube S1 until the voltage of controllable switch tube S1 decreases to turn on the body diode of controllable switch tube S1, and then drive DRV1 of controllable switch tube S1 changes from low to high (time T1 in fig. 6), so that controllable switch tube S1 turns on, and ZVS turns on.

2) t1-t 2: after the controllable switch tube S1 is turned on, the primary current of the transformer T1 increases linearly from the above negative value (the current flows: input capacitor Ci → 1 pin of transformer T1 → 2 pin of transformer T1 → controllable switch tube S1 → input capacitor Ci), until the peak current I1 is reached, and then the controllable switch tube S1 is turned off (time T2 in fig. 6). Under the condition that other conditions (such as input voltage, transformation ratio of T1 and the like) are not changed, the time for which the controllable switch tube S1 is conducted determines the peak current of the transformer T1, and the larger the current is, the larger the output power is.

3) t2-t 3: after the controllable switch tube S1 Is turned off at time T2, the primary current of the transformer T1 quickly charges the output node capacitor of the controllable switch tube S1 to a high enough value, which causes the body diode of the controllable switch tube S3 to be turned on (DRV 3 Is driven to be turned on from low to high at time T3 to control the controllable switch tube S3 to be turned on, and the controllable switch tube S3 realizes ZVS conduction), and energy starts to be output to the secondary side (after T3, Is positive and slowly increases).

4) t3-t 4: at time T3, after the controllable switch tube S3 is turned on, the capacitor C1, the primary side leakage inductance of the transformer T1, the transformer T1, and the output capacitor Co (which is equivalent to a voltage source) resonate to output energy to the secondary side, and until a resonant period is over, the output current becomes zero.

5) t4-t 5: after the secondary current Is decreased to zero at time T4, the controllable switch transistor S3 remains turned on until the primary current Ip of the transformer T1 becomes a negative current I2, and then the controllable switch transistor S3 Is turned off (time T5).

6) t5-t 6: this process is the same as t0-t 1.

Since the circuit is symmetrical on both sides of the transformer T1, the operation of transferring energy from the secondary side to the primary side is similar to that described above and will not be described in detail.

As can be seen from the detailed description of the above working process, the control method of the controllable switching tube S3 is as follows: the body diode of the controllable switch tube S3 is turned on when it is turned on (the voltage on the output capacitor of the controllable switch tube S3 is substantially zero), and then Ip reaches a negative current I2 (I2 is a minimum negative current that can ensure that the controllable switch tube S1 can be turned on at ZVS after the controllable switch tube S3 is turned off, and a margin of about 10% flows out during actual design). The control method of the controllable switching tube S1 comprises the following steps: the body diode of the controllable switch tube S1 is turned on when turned on (the voltage on the output capacitor of the controllable switch tube S1 is substantially zero), and is turned off when the Ip reaches the peak current I1 (I1 determines the output power, and I1 has a closed-loop control determination during actual operation).

Under the condition that energy is transmitted from the primary side to the secondary side, the controllable switching tube S2 only needs to realize synchronous rectification control.

Example 2:

the present embodiment is different from embodiment 1 in that: the capacitor C1 is connected in series between the controllable switch tube S1 and the controllable switch tube S3, and the capacitor C2 is connected in series between the controllable switch tube S2 and the controllable switch tube S4, as shown in fig. 3.

The other operations in this embodiment are the same as those in embodiment 1, and the control methods of the controllable switch tubes S1, S2, S3, and S4 are also the same as those in embodiment 1, and are not repeated.

Example 3:

the present embodiment is different from embodiment 1 in that: the capacitor C1 is disposed close to the input Vi, and the capacitor C2 is connected in series between the controllable switch S2 and the controllable switch S4, see fig. 3.

Example 4:

the present embodiment is different from embodiment 1 in that: the capacitor C1 is connected in series between the controllable switch tube S1 and the controllable switch tube S3, and the capacitor C2 is disposed near the input Vo, as shown in fig. 3.

The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and to implement the present invention, which cannot limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered by the protection scope of the present invention.

Claims

1. An active clamping flyback bidirectional DC/DC circuit comprises a transformer T1, an input end Vi and an output end Vo, wherein an input circuit is connected between the input end Vi and a primary side of a transformer T1, and an output circuit is connected between a secondary side of the transformer T1 and the output end Vo; the input circuit comprises an input capacitor Ci, a controllable switch tube S1 and a first active clamping circuit which are sequentially connected with an input end Vi in series, wherein the first active clamping circuit is connected with a primary winding of the transformer T1 in parallel and is connected with the input end Vi; the output circuit comprises an output capacitor Co, a controllable switch tube S2 and a second active clamp circuit which are sequentially connected with an output end Vo in series, and the second active clamp circuit is connected with a secondary winding of the transformer T1 in parallel.

2. The active-clamp flyback bidirectional DC/DC circuit of claim 1, wherein the primary winding pins of the transformer T1 are pins 1 and 2, the secondary winding pins thereof are pins 3 and 4, and the pins 2 and 3 are terminals of the same name.

3. The active-clamp flyback bidirectional DC/DC circuit of claim 1, wherein the active-clamp flyback bidirectional DC/DC circuit further comprises a capacitor C1 and a controllable switch tube S3, the capacitor C1 is connected in series with the controllable switch tube S3, the capacitor C1 is disposed close to the input Vi or the capacitor C1 is connected in series between the controllable switch tube S1 and the controllable switch tube S3.

4. The active-clamp flyback bidirectional DC/DC circuit of claim 1, wherein the active-clamp circuit two comprises a capacitor C2 and a controllable switch tube S4, the capacitor C2 is connected in series with the controllable switch tube S4, the capacitor C2 is disposed close to the input Vo or the capacitor C2 is connected in series between the controllable switch tube S2 and the controllable switch tube S4.

5. The active-clamp flyback bidirectional DC/DC circuit of claim 1, wherein the controllable switch tube S1, S2, S3, S4 each comprise a driver, a body diode, and an output node capacitor, the body diode being connected in parallel with the output node capacitor.

6. The actively-clamped flyback bidirectional DC/DC circuit of claim 5,

when energy flows from the primary side of the transformer T1 to the secondary side of the transformer T1, the driving DRV1 of the controllable switch tube S1 and the driving DRV3 of the controllable switch tube S3 are complementary drives, the driving DRV2 of the controllable switch tube S2 realizes synchronous rectification, and the driving DRV4 of the controllable switch tube S4 is always at a low level;

7. The active-clamp flyback bidirectional DC/DC circuit of any of claims 1 to 6, wherein the controllable switching tubes S1, S2, S3, S4 are IGBTs, MOSFETs, SiC MOSFETs or GaN MOS.