TWI578684B - Asymmetric half-bridge high step-down converter - Google Patents

Description

Asymmetric half-bridge high buck converter

The invention relates to an asymmetric half-bridge high buck converter, in particular to a function of high step-down ratio, high conversion efficiency and low voltage stress, and more practical utility characteristics in its overall implementation. Innovative designer of symmetrical half-bridge high buck converters.

According to the decreasing oil source, the awareness of energy conservation is high. The Energy Star label certification program jointly sponsored by The US Environmental Protection Agency and The USDepartment of Energy was established in 1992. The goal is to enable consumers to identify energy-efficient products through energy labels on electronic or electrical products, thereby reducing the greenhouse effect. Energy Star 4.0 puts the 80 PLUS specification in the standard, for the AC-DC switched power supply provided to the PC, whether the computer is in standby or hibernation, The source supply must have a minimum efficiency of 80% or more at the output load of 20%, 50%, and 100%. In addition, ENERGY STAR has partnered with Intel's CSCI Climate Savers Computing Initiative (CSCI) to accelerate the adoption of energy-efficient technologies and specifications. Because 80 PLUS meets the trend of energy saving and environmental protection, the newly launched power supply is almost always supporting the 80 PLUS specification as the main selling point, and it is recognized by the European and American consumer market with the characteristics of energy saving and power saving. In 2008, the 80 PLUS specification added stricter copper, silver, and gold medal certification. And on July 1, 2009, Energy Star 5.0 and 80 PLUS bronze medals have the same efficiency requirements. Therefore, choosing to use 80 PLUS and Energy Star approved power supplies will help save more energy and cost. Therefore, designing high-efficiency power converters to meet increasingly stringent power supply specifications is a constant trend.

For the general converter, please refer to the circuit diagram of the existing buck converter of the twenty-first figure. The buck converter (2) mainly consists of the switch S and the diode D. After the chopper obtains the pulse voltage, the output voltage V _{O is} taken through a second-order low-pass filter composed of the inductor L and the capacitor C , which satisfies V _O = DV _in , and the conduction ratio D is adjusted through the switch s ; however, When the buck converter (2) is applied to a high input voltage and low output voltage, the operational conduction duty ratio is extremely narrow, susceptible to noise interference, and it is difficult to perform closed loop voltage regulation control, and the switch S utilization rate is low. It affects the efficiency of the circuit. At the same time, the switch S is hardly switched and has no flexible switching performance. When switching at high frequency, the switching loss will cause the temperature of the switch S component to rise and reduce the life of the switch S component.

Referring to the circuit diagram of the existing bimorphic forward converter of the twenty-second figure, the bimorphic forward converter (3) is mainly added to the transformer to achieve electrical isolation, and the output voltage V _O = DV _in / n Although there is a limit of D <0.5, it has a bucking flexibility, and does not need to achieve a high step-down characteristic with a small conduction responsibility ratio, but uses a transformer 匝 ratio n > 1, so that the switch conduction duty ratio can be operated. Normally controllable range, in addition, the two main switches S ₁ and S _{2 of} the dual crystal forward converter (3) are clamped to the input voltage V _in by the diode, so it is suitable for large input voltage applications. However, the dual-crystal forward converter (3) is found to have a limit of the application range of the input voltage of the bimorphic forward converter (3) due to its limitation of D <0.5, and if to achieve a high step-down transformer, the turns ratio of the larger to n, causing the volume of the transformer increases, a parasitic capacitance is generated, the electric wire groups and the leakage inductance will increase the overall circuit surge increase, resulting in the need to withstand element The greater stress also reduces the efficiency of the twin-crystal forward converter (3). When applied to high input voltage and low output voltage, the rectifying diode and magnetic component on the secondary side of the transformer still have to withstand large current stress, which will lead to component loss rise. At the same time, the switch is hard switching and has no flexible switching performance. When the high frequency is switched, the switching loss causes the temperature of the switching element to rise, reducing the life of the switching element.

In addition, please refer to the circuit diagram of the existing bimorph forward high-voltage buck converter shown in the twenty-third figure. The dual-crystal forward high-voltage buck converter (4) needs to improve the transformer turns ratio n and needs To achieve high buck, the buck inductor is connected in series after rectifying diode D ₁ so that the transformer energy is transmitted to the output side when i _LB = i _L , so that the secondary conduction actual duty ratio is smaller than the switch conduction. Responsibility ratio D , and achieve high buck purpose; however, the twin-crystal forward high-voltage buck converter (4) found in use, due to its limit of D <0.5, the shrinkage of the twin-crystal forward high Buck converter (4) application range of input voltage, when applied to high input voltage and low output voltage, the secondary side diode and magnetic component of the transformer must withstand large current stress, resulting in component loss and thermal stress rise, and Since the voltage conversion ratio of the bi-directional forward high-voltage buck converter (4) is affected by the step-down inductance and is related to the frequency, the frequency must be regarded as a variable in small signal modeling, which not only increases the derivation of the small signal mode. Difficulty also makes the voltage control difficult to achieve, while Switch genus hard handover, no soft switching performance at high frequency switching, the switching loss of the switching element temperature rise will lead to reduced life of the switching element.

In addition, please refer to the circuit diagram of the existing asymmetric half-bridge converter of the twenty-fourth figure. The asymmetric half-bridge converter (5) uses the main switch and the auxiliary switch to perform complementary operations, so that two driving signals are generated. In this time interval, the parasitic capacitance of the switch and the leakage inductance of the transformer generate a resonant circuit. After the resonance crosses the voltage to zero, the switch switches to on to achieve zero voltage flexible switching; however, the asymmetry half-bridge converter (5) in use, to achieve a high step-down transformer, the turns ratio of the larger to n, causing the volume of the transformer increases, a parasitic capacitance is generated, the electric wire groups and the leakage inductance will The increase causes the surge of the overall circuit to rise, causing the component to withstand greater stress and also degrading the efficiency of the converter. The secondary side semiconductor component and the magnetic component are subjected to large current stress, resulting in an increase in component loss, and the secondary side diode and the magnetic component are subjected to a large current stress when the high voltage is reduced to output low voltage, high current, and high power application. As a result, component loss and thermal stress rise, and the switch drive signal must be complementary and need to have a dead band, which is complicated in the overall circuit design.

In view of this, the inventors have provided a kind of asymmetric half-bridge high-buck converter for better performance based on years of rich experience in design, development and actual production of related industries, and research and improvement on existing structures and defects. The purpose of practical value.

The main object of the present invention is to provide an asymmetric half-bridge high buck converter, which mainly has the functions of high step-down ratio, high conversion efficiency and low voltage stress, and has more practical utility characteristics in its overall implementation. .

The main purpose and effect of the asymmetric half-bridge high buck converter of the present invention are achieved by the following specific technical means:

The main purpose is that the converter is connected to the first end of the auxiliary switch S _{2 and} the first end of the capacitor C _B in parallel with the anode of the input power source V _in , and the first end of the main switch S ₁ is connected to the cathode of the input power source V _in The second end of the main switch S ₁ is connected in parallel with the second end of the auxiliary switch S _{2 and} the first end of the inductor L _r , and the second end of the capacitor C _B is connected to the second end of the inductor L _r the primary side of the transformer, the secondary side of the transformer is connected to the positive electrode of the positive rectifier diode D _1, the rectifying diode D ₁ is connected to the negative terminal of a first buck inductor L _B of the buck inductor L _b of the second end parallel with a flywheel diode D of the first end of the output inductor L _o and the negative electrode _2, a second end of the output inductor L _o connected in parallel with a first output of a first end of capacitor C _o and load R, The anode of the flywheel diode D ₂ , the second end of the output capacitor C _{o and} the second end of the load R are connected to the secondary side of the transformer.

(1)‧‧‧ converter

(11)‧‧‧Transformers

(2) ‧‧‧ buck converter

(3)‧‧‧Double-crystal forward converter

(4)‧‧‧Double-Phase Forward High-Buck Converter

(5) ‧‧‧Asymmetric Half-Bridge Converter

First picture: circuit diagram of the invention

Second picture: timing waveform diagram of the main components of the present invention

Third figure: equivalent circuit diagram of the first operation stage of the present invention

Fourth figure: equivalent circuit diagram of the second operation stage of the present invention

Figure 5: Equivalent circuit diagram of the third operation stage of the present invention

Figure 6: Equivalent circuit diagram of the fourth operation stage of the present invention

Figure 7: Equivalent circuit diagram of the fifth operation stage of the present invention

Figure 8: Equivalent circuit diagram of the sixth operation stage of the present invention

Ninth diagram: equivalent circuit diagram of the seventh operation stage of the present invention

Figure 11: Equivalent circuit diagram of the eighth operation stage of the present invention

Eleventh drawing: equivalent circuit diagram of the ninth operation stage of the present invention

Twelfth figure: equivalent circuit diagram of the tenth operation stage of the present invention

Figure 13: Analog waveform diagram of the main switch drive signal, input power supply and output voltage of the present invention

Figure 14: Actual waveform diagram of the main switch drive signal, input power supply and output voltage of the present invention

The fifteenth figure: the main switch driving signal and the cross-voltage analog waveform diagram of the invention

Figure 16: The main switch driving signal of the present invention and its cross-voltage implementation waveform

Figure 17: The auxiliary switch drive signal and its cross-over voltage analog waveform diagram of the present invention

Figure 18: Waveform diagram of the auxiliary switch drive signal and its cross-voltage implementation of the present invention

Figure 19: Analog waveform diagram of the step-down inductor current and output inductor current of the present invention

Figure 20: The waveform diagram of the step-down inductor current and output inductor current of the present invention

Figure 21: Existing buck converter circuit diagram

Figure 22: Existing dual crystal forward converter circuit diagram

Twenty-third picture: existing dual crystal forward high buck converter circuit diagram

Figure 24: Existing asymmetric half-bridge converter circuit diagram

For a more complete and clear disclosure of the technical content, the purpose of the invention and the effects thereof achieved by the present invention, it is explained in detail below, and please refer to the drawings and drawings:

First, referring to the first diagram of the circuit diagram of the present invention, the converter (1) of the present invention is mainly connected to the first end of the auxiliary switch S _{2 and} the first end of the capacitor C _B in parallel with the positive pole of the input power source V _in V _in the input power of the negative electrode is connected to a first terminal of the primary switch S _1, the second main terminal of the switch S ₁ is connected in parallel a first end and a second end of the inductor L _r auxiliary switch S _2, and the capacitance The second end of C _{B and} the second end of the inductor L _r are connected to the primary side of the transformer (11), and the positive pole of the rectifier diode (11) is connected to the positive pole of the rectifying diode D ₁ , the rectification diode D ₁ is connected to the negative terminal of a first buck inductor L _b and the second end of the buck inductor L _b connected in parallel with a first end of the flywheel diode D and the negative output inductor L _{o 2,} the The second end of the output inductor L _o is connected in parallel with the first end of the output capacitor C _{o and} the first end of the load R , and the anode of the flywheel diode D ₂ is connected to the negative side of the secondary side of the transformer (11) The second end of the capacitor C _{o and} the second end of the load R.

And the converter (1) during use, in accordance with the primary switch S _1, the auxiliary switch S _2, the primary switch S of the body ₁ of the diode D _{S 1,} the auxiliary switch S of the body ₂ of the diode D _{S 2} , the rectifying diode D ₁ , and the flywheel diode D _{2 are} turned on or off, and the converter (1) can be divided into ten linear stages in a switching period T _s , and each linear phase thereof The linear equivalent circuit and the main component waveforms are shown below. Please refer to the second diagram of the main component timing waveform diagram of the present invention as shown in the following figure:

The first stage [ t ₀ ~ t ₁ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :off]: Please refer to the third figure again. The equivalent circuit diagram of the first operation stage of the present invention is shown at this stage. when switch S ₁ is switched to off, the voltage across the main switch S ₁ is v _{ds 1} increases linearly, the voltage across the auxiliary switch S ₂ v _{ds 2} decreases linearly when the flywheel (11) of the secondary side of the transformer switching diode D ₂ is On the next stage.

Second stage [ t ₁ ~ t ₂ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the fourth diagram of the second operational stage of the present invention as shown in the equivalent circuit diagram, this stage is as the flywheel When the diode D _{2 is} switched to on, the diode current on the secondary side of the transformer (11) starts to commutate, the main switch S ₁ rises in resonance across the voltage v _{ds 1} , and the auxiliary switch S ₂ rises in resonance across the voltage v _{ds 2 .} When the auxiliary switch S _{2 is cooled} down to zero across the voltage v _{ds 2} , the body diode D _{S 2 of} the auxiliary switch S ₂ is switched to on to proceed to the next stage.

The third stage [ t ₂ ~ t ₃ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :on, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the fifth diagram for the third stage of operation of the present invention as shown in the equivalent circuit diagram. switch S ₂ cross voltage V _{DS 2} resonance drops to zero, the auxiliary switch S of the body ₂ of the diode D _{S 2} is switched on, the auxiliary switch S ₂ ready to be switched on to achieve the ZVS, when an auxiliary switch S ₂ is switched on Go to the next stage.

The fourth stage [ t ₃ ~ t ₄ ]: [main switch S ₁ :off, auxiliary switch S ₂ :on, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :on, rectifying diode D ₁ :off, flywheel diode D ₂ :on]: Please refer to the sixth circuit diagram of the fourth operation stage of the present invention as shown in the equivalent circuit diagram. switch S ₂ is switched on, the ZVS reached, when the auxiliary switch S ₂ of the current i ₂ becomes positive, the auxiliary switch S ₂ of the body diode D _{S 2} is switched off the next stage.

The fifth stage [ t ₄ ~ t ₅ ]: [main switch S ₁ :off, auxiliary switch S ₂ :on, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :off, flywheel diode D ₂ :on]: Please refer to the seventh diagram for the fifth operation stage of the present invention as shown in the equivalent circuit diagram. when the switch S of the body diode D _{2 S 2} switch is off, the auxiliary switch S ₂ of the current i ₂ flowing through the switch body, the next stage when the auxiliary switch S ₂ is switched off.

The sixth stage [ t ₅ ~ t ₆ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :off, flywheel diode D ₂ :on]: Please refer to the eighth circuit diagram of the sixth operation stage of the present invention as shown in the equivalent circuit diagram. switching the switch S ₂ is off, the voltage across the auxiliary switch S ₂ v _{ds 2} rises linearly, the voltage across the main switch S ₁ is decreased linearly v _{ds 1,} when the rectifier (11) of the secondary side of the transformer switching diode D ₁ Go to the next stage when it is on.

The seventh stage [ t ₆ ~ t ₇ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the ninth diagram of the seventh operation stage of the present invention as shown in the equivalent circuit diagram, at this stage when rectifying When the diode D _{1 is} switched to on, the diode current on the secondary side of the transformer (11) starts to commutate, the auxiliary switch S ₂ rises in resonance across the voltage v _{ds 2} , and the main switch S ₁ decreases in resonance across the voltage v _{ds 1 .} When the main switch S _{1 is cooled} down to zero across the voltage v _{ds 1} , the body diode D _{S 1 of the} main switch S ₁ is switched to on to enter the next stage.

The eighth stage [ t ₇ ~ t ₈ ]: [main switch S ₁ :off, auxiliary switch S ₂ :off, body diode D _{S 1} :on of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the eleventh figure. The equivalent circuit diagram of the eighth operation stage of the present invention is shown in this stage. switch S ₁ is the voltage across the v _{ds 1} resonance drops to zero, the main switch S of the body ₁ of the diode D _{S 1} is switched on, the main switch S ₁ can always switch is on, to achieve the ZVS, when the main switch S ₁ switches Go to the next stage when it is on.

Ninth stage [ t ₈ ~ t ₉ ]: [main switch S ₁ :on, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the eleventh figure for the ninth operation stage of the present invention as shown in the equivalent circuit diagram, this stage is When the main switch S _{1 is} switched to on, ZVS is reached. When the diode current reversal on the secondary side of the transformer (11) is completed and the flywheel diode D _{2 is} switched off, the next stage is entered.

The tenth stage [ t ₉ ~ t ₁₀ ]: [main switch S ₁ :on, auxiliary switch S ₂ :off, body diode D _{S 1} :off of main switch S ₁ , body diode of auxiliary switch S ₂ D _{S 2} :off, rectifying diode D ₁ :on, flywheel diode D ₂ :on]: Please refer to the twelfth figure. The equivalent circuit diagram of the tenth operation stage of the present invention is shown in this stage. When the flywheel diode D _{2 is} switched off, the energy is transmitted to the load R , and when the main switch S _{1 is} switched off, the first stage is returned.

According to the above circuit operation analysis, the above-mentioned high buck characteristic and the flexible switching performance of the main switch S ₁ and the auxiliary switch S ₂ are verified using the IsSpice simulation software and the actual result. The relevant parameters of the converter (1) are set as: input power V _in = 400V, output voltage V _o = 48V, output power P _o = 100~400W, switching frequency f _s = 100kHz, transformer turns ratio n =1, Transformer primary side magnetizing inductance L _m =302μH, step-down inductor L _b =4μH, output inductance L _o =207μH, capacitance C _B =33μF, inductance L _r =25μH, main switch S ₁ body capacitance C _{S 1} =1250μF, auxiliary Switch S ₂ body capacitance C _{S 2} =1250μF, output capacitance C _o =1000μF; below test the characteristics of the converter (1) with analog waveform and implementation results:

A. Electrical specification verification: Please refer to the thirteenth diagram for the main switch drive signal, input power supply and output voltage analog waveform diagram of the present invention and the fourteenth diagram of the main switch drive signal, input power supply and output voltage of the present invention. The implementation waveform diagram shows that when the conduction ratio D = 0.46, the output voltage V _o is 48V; but if the voltage conversion ratio of the conventional asymmetric half-bridge converter is V ₀ = D (1- D ) V _{i n} / n , when n =1, D =0.46, the output voltage V _o is 99.3V, which obviously cannot be reduced to the specified electrical specifications.

B. Main switch S ₁ and auxiliary switch S ₂ flexible cutting performance: Please refer to the fifteenth figure of the present invention, the main switch driving signal and its cross-voltage analog waveform diagram, and the sixteenth embodiment of the main switch driving signal of the present invention Cross-pressing waveform diagram, the seventeenth embodiment of the present invention, the auxiliary switch drive signal and its cross-voltage analog waveform diagram and the eighteenth embodiment of the present invention, the auxiliary switch drive signal and its cross-voltage implementation waveform diagram, at full load output power after when P _o = 400W, the main switch S cross voltage v of _{1 ds 1} drops to zero, the drive signal v _{gs 1} was switched on, to achieve ZVS performance; auxiliary switch S across the voltage v ₂ of _{ds 2} drops to a zero, The drive signal v _{gs 2} is switched to on to achieve the ZVS performance. It is also known that the voltage stress of the main switch S ₁ and the auxiliary switch S ₂ is V _in = 400V.

C. High-step-down performance verification: Please refer to the nineteenth figure for the buck inductor current and output inductor current analog waveform diagram and the twentieth figure. The buck inductor current and output inductor current implementation waveform of the present invention As shown in the figure, the addition of the buck inductor L _b enables the converter (1) to reach a high buck because when the main switch S _{1 is} switched to on, the secondary side diode current begins to commutate, and the buck inductor L _b When the current i _Lb starts to rise, it must wait until the step-down inductor current i _Lb = i _LO , the diode current is commutated, and the energy can be transmitted to the load R, that is, the actual conduction responsibility obtained by the secondary side is compared with the conduction of the main switch S ₁ . The responsibility ratio is small.

From the above, the implementation description of the present invention shows that the present invention has the following advantages in comparison with the prior art means:

1. High step-down ratio: The invention uses the step-down inductor method to achieve high voltage drop, does not need to operate the conduction duty ratio to be extremely narrow, and does not need to use a transformer with a larger turns ratio n, which can reduce the parasitic components of the transformer. , reduce the surge of the converter.

2. High conversion efficiency: Both the main switch and the auxiliary switch of the present invention can achieve ZVS flexible switching to reduce switching loss and improve conversion efficiency of the converter.

3. Low voltage stress: The main switch and the auxiliary switch of the present invention can share the input voltage, so that the switching element has low voltage stress, and is suitable for high voltage input applications.

However, the above-described embodiments or drawings are not intended to limit the structure or the use of the present invention, and any suitable variations or modifications of the invention will be apparent to those skilled in the art.

In summary, the embodiments of the present invention can achieve the expected use efficiency, and The specific structure disclosed has not only been seen in similar products, nor has it been disclosed before the application. Cheng has fully complied with the requirements and requirements of the Patent Law, and has filed an application for invention patents according to law. , it is really sensible.

(1)‧‧‧ converter

(11)‧‧‧Transformers

Claims (1)

An asymmetric half-bridge high step-down converter so that the converter is mainly parallel to the positive input of the auxiliary power supply V _in a first end of the switch S ₂ and the first terminal of the capacitor C _B, to the negative input of the power supply V _in connecting the first end of the main switch S _1, the second main terminal of the switch S ₁ is connected in parallel a first end and a second end of the inductor L _r of the auxiliary switch S _2, a second terminal of the capacitor C _B and _{R & lt} second end of the inductor L is connected to the primary side of the transformer, the secondary side of the transformer is connected to the positive electrode of the positive rectifier diode D _1, the rectifying diode D ₁ are connected to the negative buck inductor L a first terminal _b of the buck inductor L _b, second end in parallel with a flywheel diode and the negative output terminal of the first inductor L _o D ₂ of the second end of the output parallel inductance L _o is the output capacitance C The first end of the _{o and} the first end of the load R are connected to the negative pole of the flywheel diode D ₂ , the second end of the output capacitor C _{o and} the second end of the load R on the secondary side of the transformer.