WO2019024601A1

WO2019024601A1 - Bidirectional dc-dc converter

Info

Publication number: WO2019024601A1
Application number: PCT/CN2018/090367
Authority: WO
Inventors: 尹向阳; 李永昌; 郭启利
Original assignee: 广州金升阳科技有限公司
Priority date: 2017-08-03
Filing date: 2018-06-08
Publication date: 2019-02-07
Also published as: CN107482921A

Abstract

Provided is a bidirectional converter, comprising a first side Vs, a second side Vo, a transformer B, power tubes Q1, Q2, Q3 and Q4, diodes D1 and D2, and capacitors C1 and C2, wherein the transformer B at least comprises a primary winding Np and a secondary winding Ns; after being connected to the diode D1 in parallel, the power tube Q1 is connected to the primary winding Np in series, and after being connected to the capacitor C1 in series, the power tube Q3 is connected to the primary winding Np in parallel; and after being connected to the diode D2 in parallel, the power tube Q2 is connected to the secondary winding Ns in series, and after being connected to the capacitor C2 in series, the power tube Q4 is connected to the secondary winding Ns in parallel. Leakage inductance energy may be recycled after the resonance oscillation of the leakage inductance and capacitance, and zero voltage turn-on of some power tubes is realised, reducing the switching loss. By means of the circuit, the defects that an existing bidirectional converter using an RCD absorption circuit would consume leakage inductance electric energy and has a low efficiency are overcome, and the circuit has the characteristics of a simple circuit and low power consumption.

Description

Bidirectional DC-DC converter

Technical field

The present invention relates to a DC-DC converter, and more particularly to a DC-DC converter with energy bidirectional flow.

current technology

The DC-DC converter is an essential component of modern high-frequency switching power supplies. As its name implies, it converts the direct current (DC) input voltage Vin into a more desirable or more efficient direct current (DC) output voltage Vo.

In general, a unidirectional DC-DC converter refers to a DC-DC converter that converts a DC voltage supplied at an input terminal into a DC voltage having a higher, lower or reverse voltage level.

Compared with a unidirectional DC-DC converter, a bidirectional DC-DC converter can realize bidirectional transmission of energy by forward or reverse operation of a bidirectional DC-DC converter, that is, allowing electric energy to flow from a defined input to an output. The end, and vice versa, is equivalent to two unidirectional DC converters. It is a typical "one-machine dual-purpose" device, in the energy recovery system of uninterruptible power supply, battery charge and discharge, electric vehicles, high-power equipment, A wide range of applications are available in applications such as backup power for high-power equipment.

The flyback converter has the characteristics of few devices and high reliability, and is widely used in medium and small power DC-DC converters with a power of 50W or less. The existing application number is 201410724447.3, and the invention is called "two-way non-destructive active equalization device". Application, hereinafter referred to as Background Document 1, shows a bidirectional converter composed of a flyback converter. For convenience, the present application presents FIG. 1 of Background Document 1 in this application, see FIG. 1 of the present application. It can be seen that the RCD absorbing circuit composed of the diode D1, the resistor R1 and the capacitor C2 is set on the single side, and the RCD absorbing circuit composed of the diode D4, the resistor R3 and the capacitor C4 is set on the whole side. The working principle of the RCD absorbing circuit is a well-known technology. Refer to the section "4.3 RCD absorbing flyback converter" on page 67 of the above-mentioned "Switching Power Supply Converter Topology and Design". The shortcomings of this document: RCD absorbing circuit Only when the power tube of the flyback converter is turned from saturation conduction to cutoff, in the background document 1, when the primary side is excited, the secondary side RCD absorption circuit participates in the whole process, and the energy consumed is relatively large. The "non-destructive" absorption described in Background Document 1 is achieved.

The application No. of 201610251403.2, entitled "A Bidirectional Converter", hereinafter referred to as Background Document 2, overcomes the deficiencies of Background Document 1. For convenience, the present application presents FIG. 4 corresponding to the technical solution of Background Document 2 In the present application, referring to FIG. 2 of the present application, the advantage of this document is that the secondary side RCD absorbing circuit does not participate in the operation when the primary side is excited, and the primary side RCD absorbing circuit does not participate in the operation when the secondary side is excited; The energy is very small, achieving "lossless" absorption; however, its insufficiency analysis: leakage inductance energy is absorbed by the way of consumption, and the secondary winding Ns induced voltage is equal to: (Ns / Np) Vs, that is, the ratio Multiplying the operating voltage on the first side, the operating voltage of the first side has a larger variation range. For balanced charging for lithium batteries, the operating range of Vs is 3.0V to 4.20V, and the variation is 40%. Is 10. Then, in the background document 2, in order to work normally, the voltage regulation value of the Zener diode W2 is greater than the maximum value of the induced voltage of the secondary winding Ns 4.2V*10=42V, so as to ensure good operation, when the second side Vo needs to work, Q2 In the PWM switching state, when the RCD absorption circuit composed of D4, C2, R2, W2, the absorption voltage is too high, the drain of Q2 will drop from the higher voltage to 0V at the same time, that is, dU/dt Larger, electromagnetic radiation will be larger, the lack of background literature 2: Q2 has a high withstand voltage, high-voltage MOS tube to achieve the same on-state internal resistance, its cost is greatly increased; EMI is poor; Especially when the input voltage working range is wide, the disadvantages are more obvious. The same problem exists with Q1.

The existing bidirectional converter using a flyback converter, that is, a flyback bidirectional converter, including background document 2, is still not ideal.

Summary of the invention

In view of this, the present invention solves the deficiencies of the prior art flyback bidirectional converter, and provides a bidirectional converter for achieving bidirectional conversion of energy more efficiently.

The object of the present invention is to realize a bidirectional converter including a first side, a second side, a transformer, a first power tube, a second power tube, a third power tube, and a fourth power tube, first The capacitor and the second capacitor comprise at least a primary winding and a secondary winding, and the connection relationship is:

The source of the first power tube is connected to the input of the first side; the drain of the first power tube is connected to the opposite end of the primary winding of the transformer and the source of the third power tube; and the drain of the third power tube is connected One end of a capacitor, the other end of the first capacitor is connected to the same name end of the primary winding of the transformer, and forms the input of the first side;

The source of the second power tube is connected to the input of the second side; the drain of the second power tube is connected to the same end of the secondary winding of the transformer and the source of the fourth power tube; and the drain of the fourth power tube is connected to the second One end of the capacitor, the other end of the second capacitor is connected to the opposite end of the secondary winding of the transformer, and forms the input positive of the second side.

The gate of the first power tube, the gate of the second power tube, the gate of the third power tube, and the gate of the fourth power tube are respectively connected with an external PWM signal to respectively control the turning on and off of the four power tubes .

Preferably, the method further includes a first diode, the anode of the first diode is connected to the source of the first power tube, and the cathode of the first diode is connected to the drain of the first power tube.

Preferably, the second diode is further included, the anode of the second diode is connected to the source of the second power tube, and the cathode of the second diode is connected to the drain of the second power tube.

Preferably, the method further includes a third diode and a fourth diode, the anode of the third diode is connected to the source of the third power tube, and the cathode of the third diode is connected to the drain of the third power tube The anode of the fourth diode is connected to the source of the fourth power tube, and the cathode of the fourth diode is connected to the drain of the fourth power tube.

When the second diode is forward-conducting, the second power tube is synchronously turned on after the dead time; when the first diode is conducting, the first power tube is synchronously turned on after the dead time. When the third diode is forward-conducting, the third power tube is synchronously turned on after the dead time; when the fourth diode is forward-conducting, the fourth power tube is synchronously guided after the dead time through.

Preferably, the first diode and the second diode are Schottky diodes.

When the first power tube on the first side is in the PWM operating state, that is, when the energy is transferred from the first side to the second side, the driving of the second power tube and the third power tube are synchronized; the gate of the fourth power tube is to The source is in a low state, and the fourth power tube is in an off state;

When the second power tube of the second side is in the PWM state, that is, when the energy is transferred from the second side to the first side, the driving of the first power tube and the fourth power tube are synchronized; the gate to source of the third power tube The pole is in a low state and the third power tube is in an off state.

The PWM drive signals of the first power tube and the second power tube are complementary.

Compared with the prior art, the beneficial effects of a bidirectional converter of the present invention are:

(1) The voltage resistance of the first power tube and the second power tube does not require the use of a high-voltage power tube;

(2) Part of the power tube can achieve ZVS, the turn-off loss is small, and EMI is better;

(3) The power is efficiently and efficiently implemented in an isolated bidirectional transformation;

(4) When the input voltage has a wide working range, the above three beneficial effects are still maintained;

(5) When the leakage inductance of the transformer is large, the above four beneficial effects can still be maintained.

DRAWINGS

1 is a two-way lossless active equalization device in the background art;

2 is a schematic diagram of a bidirectional converter in the background art;

3 is a circuit schematic diagram of a first embodiment of the present invention;

4 is a schematic diagram of a body diode inside a power tube;

Figure 5 is a circuit schematic diagram of a second embodiment of the present invention;

Figure 6 is a circuit schematic diagram of a third embodiment of the present invention;

Figure 7 is a circuit schematic diagram of a fourth embodiment of the present invention.

Detailed ways

First embodiment

3 is a first embodiment of the present invention, including a first side Vs, a second side Vo, a transformer B, a first power tube Q1, a second power tube Q2, a third power tube Q3, and a fourth The power tube Q4, the first capacitor C1, the second capacitor C2, and the transformer B include at least a primary winding Np and a secondary winding Ns, and the connection relationship is:

The input of the first power tube Q1 is connected to the input of the first side Vs, which is represented by a corresponding - sign;

The drain of the first power transistor Q1 is connected to the different terminal end of the primary winding Np of the transformer and the source of the third power transistor Q3; the drain of the third power transistor Q3 is connected to the primary side of the transformer via the first capacitor C1. The same name end of the winding Np, and form the input positive of the first side, which is represented by the corresponding + sign;

The input of the second power tube Q2 is connected to the input of the second side, which is represented by a corresponding - sign; the drain of the second power transistor Q2 is the same name as the secondary winding Ns of the transformer and the fourth power tube Q4 a source; a drain of the fourth power transistor Q4 is connected to a different end of the secondary winding Ns of the transformer via a second capacitor C2, and forms an input positive of the second side, which is represented by a corresponding + sign;

The gate of Q1, the gate of Q2, the gate of Q3, and the gate of Q4 are respectively connected to external PWM signals to control the turn-on and turn-off of four power transistors.

When the second power tube of the second side is in the PWM state, that is, when the energy is transferred from the second side to the first side, the driving of the first power tube and the fourth power tube are synchronized; the gate to source of the third power tube The pole is in a low state, and the third power tube is in an off state;

The power tube generally refers to the field effect transistor, that is, the MOS tube. Since the body generally has a parasitic diode, which is also called a body diode, the body diode is not embodied in the general power tube schematic diagram. To facilitate the description of the working principle, the power tube is provided internally. The structure diagram is shown in Fig. 4. Fig. 4 shows the correspondence between the field effect transistor with the body diode and the electrical symbol of the FET of the general simple drawing method.

working principle:

Taking the first side Vs as an example, let the transformer B have a turns ratio N=Np/Ns. When the power tube Q1 is in the PWM ON state, that is, during normal operation, after the power tube Q1 is saturated and turned on, the primary winding Np is excited. The flow direction of the current is: the first side Vs+ → the same name end of the primary winding Np → the different name end of the primary winding Np → the drain D of the first power tube Q1 → the source S of the first power tube Q1 → first The side Vs-, forming a loop, at this time, using the relationship of the same name, it can be known that the secondary winding Ns of the transformer B induces an induced voltage of negative and negative, which is called "secondary winding Ns induced voltage", during the excitation process, The body diode of Q2 is in reverse bias and the transformer stores energy.

Since the gate to the source of the fourth power transistor Q4 is in a low state, the fourth power transistor Q4 is in an off state. At this moment, the secondary winding Ns induces a voltage to charge the capacitor C2 through the body diode of the fourth power transistor Q4. Since the fourth power transistor Q4 is in the off state and there is no other path, this is the first cycle. In the subsequent cycle, since the capacitor C2 is charged and the charging current is no longer formed, in the subsequent cycle, When the power tube Q1 is again saturated and conducts and the primary winding Np of the transformer is excited, the secondary winding Ns induces a voltage in an idling state without energy loss.

When the power transistor Q1 is turned from off to off, the excitation current of the primary winding Np in the transformer B cannot be lost, and the primary excitation current charges the output capacitance of Q1 (the parasitic capacitance between the drain and the source of Q1), and The output capacitor of Q3 (the parasitic capacitance between the drain and the source of Q3) is discharged. When the voltage Vds_Q3 between the drain and the source of Q3 is 0, the body diode is turned on, and the third power is turned on during this period. Tube Q3, can realize the zero voltage conduction of Q3, ie ZVS; the transformer releases energy, the original flow direction is: the same name end of the primary winding Np flows to the different name end, that is, from top to bottom, transformer B operates as energy storage inductor The current will appear in the secondary winding Ns, the flow direction is still the same name end flow to the different name end, the secondary winding Ns of the transformer B appears from the bottom up current, then the body diode of Q2 is in the forward conduction state, the energy from The primary side is transferred to the secondary side, and the second side Vo is charged to complete the power conversion;

At this time, the primary side magnetizing inductance is clamped at -NVo by the secondary side. Since the transformer B has a leakage inductance, the leakage inductance resonates through the saturated conduction of Q3 and C1; and as the inductor discharges, the 1/2 cycle passes. After the Q3 is turned off, the inductor current cannot be abruptly changed. At this time, the Q1 output capacitor discharges and the Q3 output capacitor charges. When the voltage across the Q1 drain source is zero, the body diode is turned on. At this time, Q1 is turned on, and Q1 is realized. The voltage is turned on, and then the second cycle begins.

When the value of the capacitor value C1 is large, the voltage clamping effect of the Q1 drain to the source is good, almost no high frequency oscillation, and the zero voltage turn-on of Q1 and Q3 is realized, and the switching loss is reduced;

During the whole work process, Q4 does not work, and the third power tube Q3 and Q1 work alternately, that is, Q3 is turned on after Q1 is turned off, and Q1 is turned on after Q3 is turned off, and there is a dead time between the alternate work;

When the body diode of Q2 is conducting in the forward direction, the second power tube Q2 connected in parallel is turned on synchronously, so that the synchronous rectification function of the second power tube Q2 can be realized, and the conversion efficiency is further improved.

The above is the working principle of the first side Vs operation, and the energy is transferred from the first side Vs to the second side Vo. As can be seen from Figure 3, the two sides of the circuit have a high degree of symmetry, although the operating voltage on both sides may be different, such as the second side is connected to the entire battery pack, but the working principle is the same, the work of the second side Vo works. The principle that the energy is transferred from the second side Vo to the first side Vs, that is, when the second power tube Q2 of the second side Vo is in the PWM operating state, the gate to the source of the third power transistor Q3 is at a low level. State, the third power tube Q3 is in an off state, the fourth power tube Q4 is in a working state complementary to Q2, and the energy conversion transfer is also implemented, and the energy is transferred from the second side Vo to the first side Vs;

This achieves bidirectional transmission of energy and overcomes the deficiencies of the prior art.

The following is experimental data:

The power circuit is shown in Figure 3. It is applied between the super capacitor unit and the super capacitor group, and equalizes the voltage of one cell in the super capacitor group and the voltage of other cells in the group.

The Vs working voltage is 2.8V, which is the voltage of a super capacitor. The power transistors Q1 and Q3 are both SIR422, which is a 40V 40A MOS transistor. Its RDS(ON) is 6.6mΩ, the package is SO-8, and the capacitor C1 is 4.7. uF;

Vo working voltage is 28V, which is the voltage of a super capacitor group. It is obtained by connecting ten super capacitors in series. The power tubes Q2 and Q4 are both BSZ440N10NS3G, 100V/18A, and its RDS(ON) is 44mΩ. The package is PG-TSDSON. -8 MOS tube, capacitor C2 is 4.7uF;

The parameters of transformer B: the core is ER14.5 universal core; the primary winding Np is 3匝, which is 8 strands of 0.2mm enameled wire and wound; the secondary winding Ns is 12匝, which is 3 strands of 0.2mm enameled wire and wound; Design power is 14W;

There is no current-sense resistor that reduces the conversion efficiency. The technical solution for PWM control adopts the Chinese application number 201410459391.3, which is called "A Balanced Charging Circuit and Battery Pack", which limits the maximum duty cycle to control the operating current. And according to Figure 4 changed to a bidirectional converter.

The integrated circuits for the main control are all ISL6840, and the operating frequency is 270KHz. The conversion efficiency of the present invention is measured:

Conversion efficiency from the first side Vs to the second side Vo (ie, the input voltage is 2.8V, the output voltage is 28V, and the output power is 14W): 86.6%;

Conversion efficiency from the second side Vo to the first side Vs (ie, the input voltage is 28V, the output voltage is 2.8V, and the output power is 14W): 91.4%;

Compare the existing technology:

Referring to the circuit in Figure 2, modify the same sample, change the power circuit from Figure 3 to Figure 2, retain the same transformer and power transistors Q1, Q2, and the same capacitors C1, C2, remove Q3 and Q4 , replaced by D3 and D4,

The diode D3 on the first side is BAS16, the resistor R1 is 10Ω, the Zener diode W1 is a 10V/0.2W voltage regulator tube; the diode D4 on the second side is a diode M1FL20U-6063, the resistor R2 is 100Ω, and the Zener diode W2 It is a 39V/0.5W voltage regulator tube;

Under the same output power conditions, the efficiency is reduced to:

The conversion efficiency from the first side Vs to the second side Vo was 84.8%, which was 1.3% lower than that of the present invention.

The conversion efficiency from the second side Vo to the first side Vs was 90.0%; compared with the present invention, it was decreased by 1.4%.

It can be seen that the solution of the present invention realizes the recovery of the leakage inductance energy and realizes the ZVS of the power tube by participating in the resonance of the energy of the leakage inductance and the capacitance C1, thereby achieving better “non-destructive” absorption than the prior art; The realization of the purpose of the invention is achieved by implementing an isolated two-way transformation.

Second embodiment

Unlike the first embodiment, the first diode D1 is connected in parallel between the source and the drain of Q1, the anode of D1 is connected to the source of Q1, and the cathode of D1 is connected to the drain of Q1. D1 can be a Schottky diode. When D1 is forward-conducting, the D1 conduction loss is smaller than the body diode conduction loss of Q1, which can further improve the conversion efficiency.

Third embodiment

Different from the second embodiment, the second diode D2 is connected in parallel between the source and the drain of Q2, the anode of D2 is connected to the source of Q2, and the cathode of D2 is connected to the drain of Q2. D2 can be a Schottky diode. When D2 is forward-conducting, the D2 conduction loss is smaller than the body diode conduction loss of Q2, which can further improve the conversion efficiency.

Fourth embodiment

Different from the third embodiment, a third diode D3 is connected in parallel between the source and the drain of Q3, the anode of D3 is connected to the source of Q3, and the cathode of D3 is connected to the drain of Q3, at Q4. A fourth diode D4 is connected in parallel between the source and the drain, the anode of D4 is connected to the source of Q4, and the cathode of D34 is connected to the drain of Q4. D3 and D4 can be Schottky diodes. When D3 or D4 is forward-conducting, its conduction loss is smaller than the body diode conduction loss of the power tube connected in parallel, which can further improve the conversion efficiency.

The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiments are not to be construed as limiting the invention.

It will be apparent to those skilled in the art that modifications and refinements can be made without departing from the spirit and scope of the present invention, such as adding a current sense resistor or current transformer, replacing the power in the text with a bipolar transistor. The improvement and refinement of the transformer in the primary winding or the secondary winding of the transformer to increase the leakage inductance of the transformer should also be regarded as the protection scope of the present invention. Here, the scope of protection of the present invention should be omitted. The scope defined by the claims shall prevail.

Claims

A bidirectional DC-DC converter, comprising: a first side, a second side, a transformer, a first power tube, a second power tube, a third power tube, a fourth power tube, a first capacitor, a second capacitor; the transformer includes at least a primary winding and a secondary winding;

The source of the first power tube is connected to the input of the first side; the drain of the first power tube is connected to the opposite end of the primary winding and the source of the third power tube; and the drain of the third power tube is connected to the first capacitor One end of the first capacitor is connected to the same end of the primary winding of the transformer, and forms the input of the first side;

The source of the second power tube is connected to the input of the second side; the drain of the second power tube is connected to the same end of the secondary winding and the source of the fourth power tube; the drain of the fourth power tube is connected to the second capacitor One end, the other end of the second capacitor is connected to the opposite end of the secondary winding of the transformer, and forms the input of the second side;

The gate of the first power tube, the gate of the second power tube, the gate of the third power tube, and the gate of the fourth power tube are respectively connected to external PWM driving signals.
The bidirectional DC-DC converter according to claim 1, further comprising a first diode, an anode of the first diode being connected to a source of the first power transistor, and a cathode of the first diode Connected to the drain of the first power tube.
The bidirectional DC-DC converter according to claim 1 or 2, further comprising a second diode, the anode of the second diode being connected to the source of the second power transistor, and the second diode The cathode is connected to the drain of the second power tube.
The bidirectional DC-DC converter according to claim 3, further comprising a third diode and a fourth diode, wherein an anode of the third diode is connected to a source of the third power tube, The cathode of the three diode is connected to the drain of the third power tube; the anode of the fourth diode is connected to the source of the fourth power tube, and the cathode of the fourth diode is connected to the drain of the fourth power tube.
The bidirectional DC-DC converter according to claim 4, wherein when the second diode is forward-conducting, the second power tube is synchronously turned on after the dead time; the first two When the pole tube is in the forward direction, the first power tube is synchronously turned on after the dead time; when the third diode is in the forward direction, the third power tube is synchronously turned on after the dead time; When the fourth diode is forward-conducting, the fourth power tube is synchronously turned on after the dead time.
The bidirectional DC-DC converter according to claim 5, wherein the PWM driving signals of the first power tube and the second power tube are complementary, and the second power is transferred when the energy is transferred from the first side to the second side. The driving signals of the tube and the third power tube are synchronized, and the fourth power tube is in an off state;

When the energy is transferred from the second side to the first side, the driving signals of the first power tube and the fourth power tube are synchronized, and the third power tube is in an off state.
The bidirectional DC-DC converter according to claim 6, wherein the first capacitor and the second capacitor are both a rechargeable battery or a rechargeable battery pack.
The bidirectional DC-DC converter of claim 7 wherein the first diode and the second diode are Schottky diodes.