200款Prius的升压转换器

Development of Hybrid Electric Drive System

Using a Boost Converter

Masaki Okamura

Eiji Sato

Shoichi Sasaki

TOYOTA MOTOR CORPORATION

1, Toyota-cho, Toyota, Aichi, 471-8572, Japan

Phone/ Fax : +81-565-72-9071/9147

Abstract

Toyota introduced a new generation of hybrid vehicle to the market in September of 2003. The new Prius, equipped with a new Toyota-developed inverter system, is capable of outputting more power than the conventional systems. One of the strong points of this new system is that a Boost Converter has been placed between the inverter and the battery. The Boost Converter is capable of raising the voltage from the battery, enabling the inverter to drive a high power output motor. The Toyota Hybrid System (THS), consists of a high power motor, generator, and a battery of relatively lower power. When the Boost Converter was adopted in the THS, it was possible to keep bulk and cost of the additional unit in the system to a minimum, by letting the Boost Converter function to the same power level as the battery. The control system of the Boost Converter consists simply of a PI controller. By using existing sensors and microprocessors, it was possible to develop a new system at no additional costs. The Boost Converter’s control system achieves high efficiency by optimizing its output voltage according to the relative state of the motor and the generator. Toyota was able to achieve a 50% improvement in the motor power output with the new Boost Converter, while keeping a similar complexity of the conventional system. As of now, Toyota plans to spread the development to other new hybrid vehicles.__

Keywords: Hybrid, Electric Drive, Converter, Inverter, Control System

Figure1: TOYOTA NEW PRIUS

1.Introduction

Toyota introduced the “Prius” in December 1997, the world’s first mass-produced hybrid vehicle, which is equipped with the Toyota Hybrid System (THS). The PRIUS has gained a reputation as a highly innovative vehicle, and its cumulative worldwide sales have exceeded 110,000 units. THS has continued to evolve, and Toyota has developed the concept of Hybrid Synergy Drive in 2003. Based on this concept, Toyota has developed a new-generation Toyota Hybrid System called THS I I. This system achieves a high level of compatibility between environmental performance and power thanks to an 1.5 times increase in the motor output, a boost of the power supply voltage, and significant advances in the control system. Toyota introduced the new PRI US in September 2003, equipped with THS I I. I n the following, we describe the Hybrid Electric Drive System using a Boost Converter, which is one of the new technologies of THSII.

2. Objective of THSII development

Automobiles in the future must increase both environmental and safety performances, while improving the all-important motor vehicle characteristic of being fun to drive. To achieve superior driving performance, which is the basis for driving enjoyment, the conventional approach has been to increase output and torque by increasing engine displacement or using supercharging. However, this approach decreases fuel efficiency, making it difficult to achieve compatibility of environmental performance and power. I n other words, fuel efficiency and power are in a trade-off relationship. By using the Toyota Hybrid System (THS) in the Prius, Toyota was able to find the solution to this problem. THS, which is a Series/Parallel Hybrid System, contains a power split device that splits power into two paths. In one path (Mechanical path), the power from the gasoline engine is directly transmitted to the vehicle's wheels. In the other path (Electrical path), the power from the engine is converted into electricity by a generator to drive an electric motor or to charge the battery. THS requires no external charging, unlike EVs (Electric Vehicles). I t is therefore usable with existing infrastructure. THS’s configuration, through the use of a motor having high low-speed torque and high output, manages idling stop, stopping of the gasoline engine while the vehicle is running, running of the vehicle using the electric motor, motor assist at any speed, and highly efficient energy regeneration, without using a clutch or transmission.

Mechanical path

Electrical path

Figure 2: System Configuration

The objective of THSII development was both to raise the motor output drastically, which contributes to vehicle characteristic of being fun to drive and to improve the fuel efficiency of the electric drive system.As a result of research, we developed the best method which raises the battery voltage, enabling the inverter to drive a high power output motor/generator.

Due to the variable-voltage system, THSII achieves compatibility of high levels of both environmental performance and power.

3. Objective of THSII development

Figure 3 shows the configuration of the Variable-voltage System. In the THS, the battery voltage directly drives a motor/generator. In the THSII, a Boost Converter has been placed between the inverter and the battery. The Boost Converter is capable of raising the voltage from the battery, enabling the inverter to drive a high power output motor/generator. The voltage of the motor and the generator has been increased from about 200V DC, which is the battery voltage, to a maximum of 500V DC. The 4 main characteristics of the system are described in the following.

Figure 3: Variable-voltage System

3.1 Design of high power output Motor/Generator by raising drive voltage

Motor power output is generally proportional to the drive voltage. Figure 4 shows a relation between drive voltage and torque, figure 5 shows a relation between drive voltage and power output. 500V DC drive voltage increases both torque and power output by about 2.5 times compared to 200V DC drive voltage, without increasing motor current. Because of small current, it is possible to keep the same bulk of the conventional motor/generator

rpm

rpm

power Figure 4: Relation between drive voltage and torque Figure 5:Relation between drive voltage and power output

3.2 Bulk of the additional unit in the new system kept to a minimum

The motor in the THS, consisting of a high power motor, generator, and a relatively lower power battery, is driven by both generator power and battery power. Figure 6 shows a typical energy flow. Both the generator power of 30kW and the battery power of 20kW supply the motor power of 50kW. Due to the low power of the battery, it is possible to keep the bulk of the Boost Converter to a minimum by letting it work to the same power level as the battery.

Figure 6: Typical energy flow in the THSII

3.3 High system efficiency achieved by optimizing output voltage

The new system optimizes its output voltage according to the relative state of the motor and generator. This optimization helps decrease switching losses in the inverter, and copper losses of inductor and boost converter by decreasing the ripple current.The method of this optimization is described later on.

3.4 Can be easily developed for other hybrid vehicles

The specifications of the new system can be easily designed because the Boost Converter output voltage is independent of the battery voltage. Thus a reasonable reduction of the number of battery modules does not influence the output drastically from a design stand point. The output voltage of the Boost Converter is designed according to the specifications of the motor/generator.(Figure 7)

Figure 7: Design of the voltages in the Variable-voltage System

In this way, the new system achieves high power output without increasing bulk, and is able to be widely developed for other hybrid vehicles, while keeping the same cost as the conventional systems.

4. Structure of Variable-voltage System

The Variable-voltage System consists of a motor, generator, and power control unit which supplies the electrical power. Each specification is described as follows.

4.1 Power Control Unit

By placing the newly developed Boost Converter circuit inside the power control unit, the voltage of the motor and the generator can be increased from 274V DC in the THS to a maximum of 500V DC in the THSII(Figure 8). As a result, electrical power can be supplied to the motor using a smaller current, thus contributing to an increase in efficiency. When the Boost Converter is adopted in the THS, consisting of a high power motor, generator, and a battery of relatively lower power, it is possible to minimize the bulk by allowing the Boost Converter to function at the same power level as the battery. Also, with the control circuits being integrated as well, the size of the power control unit has remained sensibly the same size.

Figure 8: Power Control Unit

4.2 Motor

THS I I uses an AC synchronous-type motor, which is a high-efficiency DC brushless motor with AC current. Neodymium permanent magnets, and a rotor made of stacked electromagnetic steel plates form a high-performance motor. Furthermore, by arranging the permanent magnets in an optimum V-shape, the drive torque is improved and the output is increased. This, combined with an increase in the power supply voltage, has increased power output by approximately 1.5 times from THS, i.e., 33 kW to 50kW, even with a motor of the same size. (Figure 9)

Figure 9: Evolution of the Motor

4.3 Generator

Like the motor, the generator is also an AC synchronous type. In order to supply sufficient power to the high-output motor, the generator is rotated at a higher speed than conventional to increase its output. Improvements to the rotor strength have increased the maximum output from 6,500 rpm in the THS, to 10,000 rpm in the THSI I. This increase in rpm has significantly increased the power supply output, improving the acceleration performance in the low/medium-speed range. As a result, an optimum combination of a high-output motor and an engine has been achieved.

5. Boost Converter

The Boost Converter that supports the V ariable-voltage System is described in the following section.

5.1 Boost Converter Circuit

Figure 10 shows the configuration of the Variable-voltage System, and Figure 11 shows the configuration of the Power Control Unit. The Boost Converter consists of a pair of I GBTs (I nsulated Gate Bipolar Transistor), an inductor, a main capacitor, and a filter capacitor. This system can charge and discharge continuously without changing the electrical path. IGBTs switch according to duty cycles calculated by software. They consequently raise the battery voltage to a higher level, and control the voltage of the main capacitor. The inductor and the filter capacitor are designed to decrease the ripple current caused by the IGBT switching; contributing to an increase in efficiency. The voltage of the main capacitor is called system voltage. The new system is able to maintain a high power output for the motor/generator independently of battery voltage, making it possible to keep the high performance.Figure 10: Variable-voltage System Circuit

Figure 11: Power Control Unit

To Generator

To Battery

To Motor Inductor

Main _Filter Capacitor IGBTs are under

the Capacitor.

5.2 Boost Converter Control System

The control system of the boost converter consists simply of a PI controller. By using existing sensors and microprocessors, it was possible to develop a new system at no additional costs. Figure 12 shows the system block diagram. First, the controller calculates a system voltage command, and then shifts to the feedforward and the feedback calculating blocks. At the feedforward block, switching duty is calculated as the following equation shows (1.1).

Duty = … (1.1)The role of the feedforward block is to generate the system voltage as close as possible to the system voltage command.

At the feedback block, the controller calculates the PI gain by using the difference between the system voltage command and system voltage feedback value, adds to the result of the feedforward block, then finally generates the last duty command. The role of the feedback block is to make up for the constant difference generated in the system voltage, as IGBTs cannot execute the ideal switching according to the duty command because of the switching dead-time.

Thanks to this PI controller, the system voltage is controlled in a stable way.

Figure 12: Boost Converter Control System Block Diagram

6. Optimizing the Variable-voltage System

Based on the Boost Converter introduced in the previous section, we optimized the Variable-voltage system for an increase in system efficiency. In this section, the optimization approach is described.

6.1 Optimization of the Motor/Generator Efficiency

The permanent-magnet type AC synchronous motor generates electromotive force due to revolutions of the magnet-mounted rotor. Because of the generation of electromotive force, the motor becomes uncontrollable when the motor terminal voltage exceeds the system voltage. By flux-weakening control that suppresses flux generated by the magnet, the terminal voltage is reduced, which enables motor operation in the high-speed range. However, flux-weakening control increases motor current, and as a result, motor efficiency decreases. Figure 13 shows a relation between system voltage, motor current and motor loss at a typical driving point. The lower the system voltage is, the higher motor current and motor loss are. It is shown that the optimization of motor efficiency is to set up the system voltage such that it doesn’t need flux-weakening control. In the THS, as the system voltage is common to the motor and the generator, it has to be set at the highest required voltage. But, as the system voltage has an upper limit, it Battery voltage System voltage command

Last Duty command

Vehicle condition

is necessary to use flux-weakening control after it reaches an upper limit.

6.2 Optimization of the Inverter Efficiency

I nverter losses are mainly switching-loss and on-loss of I GBTs. Switching loss increases due to an increase of motor current and system voltage, on-loss increases due to an increase of motor current.Figure 14 shows a relation between system voltage and inverter loss.

Inverter loss increases due to an increase of motor current during flux-weakening control as well as that of system voltage. It is shown that the optimization of inverter efficiency is to set up the minimum system voltage such that it doesn’t need flux-weakening control.

6.3 Optimization of the Boost Converter Efficiency

Boost converter losses are mainly switching-loss and on-loss of I GBTs, and copper loss of inductor.Figure 15 shows a relation between system voltage and converter loss. Converter loss, similarly to inverter loss, increases due to an increase of motor current during flux-weakening control as well as that of system voltage. But the converter has one more loss : copper loss of ripple current. I t increases proportionally to an increase of system voltage.(Figure 16) It is shown that the optimization of converter

efficiency is to set up the minimum system voltage such that it doesn’t need flux-weakening control.loss

Figure13:

Relation between system voltage and motor

loss

Figure14:Relation between system voltage and inverter Figure15:

Relation between system voltage and converter Figure16:Relation between system voltage and ripple

6.4 Optimization of the Variable-voltage System Efficiency

Based on the methods introduced in 6.1-6.3, it was possible to optimize the Variable-voltage system efficiency. Figure 17 shows the system voltage calculating block diagram. First, motor and generator voltage are calculated from respective torque command and revolution values according to vehicle condition such that it doesn’t need flux-weakening control. Selecting the highest voltage value then generates the system voltage command. With the Variable-voltage System, maximum efficiency can be achieved by selecting the proper voltage level for generator and motor, while minimizing losses, and ensuring motor/generator commands are carried out exactly.

Figure17: System Voltage Calculating Block Diagram

Figure 18 shows a relation between the system voltage and the system loss at a typical driving point. It shows comparison between three different voltages : 200V DC, 300V DC, and 500V DC. At the point [1],system loss of 200V drive is maximal due to flux-weakening control, while comparing 500V drive and 300V drive, system loss of 500V drive is worse than that of 350V drive because of the switching-loss.System voltage of about 300V drive is the most suitable. At the point [2], as 300V drive needs flux-weakening control, system voltage of about 500V drive is the most suitable.

Figure18: Relation between system voltage and system loss

[1][2]Torque

System

Loss

7. On-road Test Results

Typical real world results are described in the following paragraph.

7.1 Full Acceleration

Figure 19 shows the plot of the system voltage at the full acceleration test. When the motor is stopped, the system voltage is equal to the battery voltage. Following a rise of motor revolution, the system voltage is raised up to 500V DC and is controlled in a stable way.

7.2 Pulse Acceleration

As for the pulse acceleration test, torque commands of motor/generator are changed frequently. Figure 20shows the movement ranges of Motor/Generator. During accelerator ON position, as motor torque is high,generator torque and revolution are also high to maintain the high power output of the motor. Therefore,the required system voltage is high. On the other hand, during accelerator OFF position, as motor torque is nearly nil, generator torque and revolution are also lower. Therefore, the required system voltage is low.

Figure 20: Movement range of Motor/Generator during pulse acceleration

rpm Generation

rpm

Generator Characteristic Figure19: Full Acceleration test

10

2030405060V o l t a g e [V ]

Figure 21 shows the plot of the system voltage during the pulse acceleration test. It shows that the system voltage is raised during accelerator ON position, while it falls during accelerator OFF position.

Although the system voltage is changeable due to optimizing like this, the system voltage is controlled in a stable way

Figure21: Pulse Acceleration test

8. Conclusions

This paper describes the technology used in the high-voltage power supply system incorporated in THSII. The main characteristics are as follows :

(1) Design of high power output Motor/Generator by raising drive voltage

(2) Bulk of the additional Boost Converter in the new system kept to a minimum

(3) High system efficiency achieved by optimizing output voltage

(4) Can be easily developed for other hybrid vehicles

Toyota plans to widely develop the new system for other hybrid vehicles._

9. References

[1] K. Shingo, K. Kaoru, T. Katsu, Y. Hata. Development of Electric Motors for the TOYOTA Hybrid Vehicle “PRIUS” EVS-17, Dec. 2000

[2] Toyota motor corporation TOYOTA HYBRID SYSTEM THS II Press Release April 17, 2003

10. Authors

Masaki Okamura

Electric & Hybrid Vehicle Engineering Div.

Power Train Development Group

TOYOTA MOTOR CORPORATION

E-mail: okamura@masaki.tec.toyota.co.jp

Eiji Sato

Group Manager

Electric & Hybrid Vehicle Engineering Div.

Power Train Development Group

TOYOTA MOTOR CORPORATION

Shoichi Sasaki

Project General Manager

Electric & Hybrid Vehicle Engineering Div.

Power Train Development Group

TOYOTA MOTOR CORPORATION

DC降压转换器

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降压转换器的工作原理

降压转换器的工作原理 设计降压转换器并不是件轻松的工作。许多使用者都希望转换器是一个盒子，一端输入一个直流电压，另一端输出另一个直流电压。这个盒子可以有很多形式，可以是降阶来产生一个更低的电压，或是升压来产生一个更高的电压。还有很多特殊的选项，如升降压、反激和单端初级电感转换器(SEPIC)，这是一种能让输出电压大于、小于或等于输入电压的DC-DC转换器。如果一个系统采用交流电工作，第一个AC-DC模块应当产生系统所需的最高的直流电压。因此，使用最广的器件是降压转换器。 使用开关稳压器的降压转换器具有所有转换器当中最高的效率。高效率意味着转换过程中的能量损耗更少，而且能简化热管理。 图1显示了一种降压开关稳压器的基本原理，即同步降压转换器。“同步降压”指的是MOSFET用作低边开关。相对应的，标准降压稳压器要使用一个肖特基二极管做为低边开关。与标准降压稳压器相比，同步降压稳压器的主要好处是效率更高，因为MOSFET的电压降比二极管的电压降要低。低边和高边MOSFET的定时信息是由脉宽调制(PWM)控制器提供的。控制器的输入是来自输出端反馈回来的电压。这个闭环控制使降压转换器能够根据负载的变化调节输出。PWM模块的输出是一个用来升高或降低开关频率的数字信号。该信号驱动一对MOSFET。信号的占空比决定了输入直接连到输出的导通时间的百分比。因此，输出电压是输入电压和占空比的乘积。

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升压降压电源电路工作原理

b o o s t升压电路工作原理 boost升压电路是一种开关直流升压电路，它可以是输出电压比输入电压高。 基本电路图见图一： 假定那个开关（三极管或者mos管）已经断开了很长时间，所有的元件都处于理想状态，电容电压等于输入电压。 下面要分充电和放电两个部分来说明这个电路 充电过程 在充电过程中，开关闭合（三极管导通），等效电路如图二，开关（三极管）处用导线代替。这时，输入电压流过电感。二极管防止电容对地放电。由于输入是直流电，所以电感上的电流以一定的比率线性增加，这个比率跟电感大小有关。随着电感电流增加，电感里储存了一些能量。

放电过程 如图，这是当开关断开（三极管截止）时的等效电路。当开关断开（三极管截止）时，由于电感的电流保持特性，流经电感的电流不会马上变为0，而是缓慢的由充电完毕时的值变为0。而原来的电路已断开，于是电感只能通过新电路放电，即电感开始给电容充电，电容两端电压升高，此时电压已经高于输入电压了。升压完毕。 说起来升压过程就是一个电感的能量传递过程。充电时，电感吸收能量，放电时电感放出能量。 如果电容量足够大，那么在输出端就可以在放电过程中保持一个持续的电流。

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1

LTC3441 2 sn3441 3441fs V IN , V OUT Voltage........................................ –0.3V to 6V SW1, SW2 Voltage DC ...........................................................–0.3V to 6V Pulsed < 100ns ...................................... –0.3V to 7V SHDN/SS, MODE/SYNC Voltage................. –0.3V to 6V Operating Temperature Range (Note 2)..–40°C to 85°C Maximum Junction Temperature (Note 4)........... 125°C Storage Temperature Range................ –65°C to 125°C ORDER PART NUMBER (Note 1) ABSOLUTE AXI U RATI GS W W W U PACKAGE/ORDER I FOR ATIO U U W Consult LTC Marketing for parts specified with wider operating temperature ranges. LTC3441EDE T JMAX = 125°C θJA = 53°C/W 1-LAYER BOARD θJA = 43°C/W 4-LAYER BOARD θJC = 4.3°C/W EXPOSED PAD IS PGND (PIN 13)MUST BE SOLDERED TO PCB DE PART MARKING 3441 121110987 123456 FB V C V IN PV IN V OUT MODE/SYNC SHDN/SS GND PGND SW1SW2PGND TOP VIEW 13 DE12 PACKAGE 12-LEAD (4mm × 3mm) PLASTIC DFN The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = 25°C. V IN = V OUT = 3.6V,unless otherwise noted. ELECTRICAL CHARACTERISTICS PARAMETER CONDITIONS MIN TYP MAX UNITS Input Start-Up Voltage ● 2.3 2.4V Output Voltage Adjust Range ● 2.4 5.25V Feedback Voltage ● 1.19 1.22 1.25V Feedback Input Current V FB = 1.22V 150nA Quiescent Current—Burst Mode Operation V C = 0V, MODE/SYNC = 3V (Note 3) 2540μA Quiescent Current—SHDN V OUT = SHDN = 0V, Not Including Switch Leakage 0.11μA Quiescent Current—Active MODE/SYNC = 0V (Note 3)520900μA NMOS Switch Leakage Switches B and C 0.17μA PMOS Switch Leakage Switches A and D 0.110 μA NMOS Switch On Resistance Switches B and C 0.10?PMOS Switch On Resistance Switches A and D 0.11 ?Input Current Limit ● 2 3.2A Max Duty Cycle Boost (% Switch C On)●7088 %Buck (% Switch A In) ●100% Min Duty Cycle ●0 %Frequency Accuracy ●0.851 1.15MHz MODE/SYNC Threshold ● 0.4 1.4V MODE/SYNC Input Current V MODE/SYNC = 5.5V 0.011 μA Error Amp AV OL 90dB Error Amp Source Current 14μA Error Amp Sink Current 300μA SHDN/SS Threshold When IC is Enabled ●0.41 1.4V SHDN/SS Threshold When EA is at Max Boost Duty Cycle 2 2.4V SHDN/SS Input Current V SHDN = 5.5V 0.01 1 μA

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说起来升压过程就是一个电感的能量传递过程。充电时，电感吸收能量，放电时电感放出能量。 如果电容量足够大，那么在输出端就可以在放电过程中保持一个持续的电流。 如果这个通断的过程不断重复，就可以在电容两端得到高于输入电压的电压。 一些补充1 AA电压低,反激升压电路制约功率和效率的瓶颈在开关管,整流管,及其他损耗(含电感上). 1.电感不能用磁体太小的(无法存应有的能量),线径太细的(脉冲电流大,会有线损大). 2 整流管大都用肖特基,大家一样,无特色,在输出3.3V时,整流损耗约百分之十. 3 开关管,关键在这儿了,放大量要足够进饱和,导通压降一定要小,是成功的关键.总共才一伏,管子上耗多了就没电出来了,因些管压降应选最大电流时不超过0.2--0.3V,单只做不到就多只并联....... 4 最大电流有多大呢?我们简单点就算1A吧,其实是不止的.由于效率低会超过1.5A,这是平均值,半周供电时为3A,实际电流波形为0至6A.所以咱建议要用两只号称5A实际3A的管子并起来才能勉强对付. 5 现成的芯片都没有集成上述那么大电流的管子,所以咱建议用土电路就够对付洋电路了. 以上是书本上没有直说的知识,但与书本知识可对照印证. 开关管导通时，电源经由电感-开关管形成回路，电流在电感中转化为磁能贮存；开关管关断时，电感中的磁能转化为电能在电感端左负右正，此电压叠加在电源正端，经由二极管-

SY7208互换的升压型DC-DC转换器MXT7515

2.3V to 6V input voltage Rangel Efficiency up to 96% 26V Boost converter with 2.8A switch current 1.2Mhz fixed Switching Frequency Integrated soft-start Thermal Shutdown Under voltage Lockout SOT23-6 Package is a high frequency, high efficien cy DC to DC converter with an integrated 2.8A, 0.1Ω power switch capable of providing an output voltage up to 26V.The fixed 1.2MHz allows the use of small external inducti ons and capacitors and provides fast transien t response. It integrates Soft start, Comp. On ly need few components outside. Handheld Devices GPS Receiver Digital Still Camera Portable Applications DSL Modem PCMCIA Card TFT LCD Bias Supply Figure 1 Typical Application Circuit 5 1 2 3 6 IN EN GND SW FB NC 4 2.3V to 6V Cbv 16V １μＦMXT75151.2MHZ,26V Step-up DC/DC Converter Features GENERAL DESCRIPTION APPLICATIONS MXT7515The

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Development of Hybrid Electric Drive System Using a Boost Converter Masaki Okamura Eiji Sato Shoichi Sasaki TOYOTA MOTOR CORPORATION 1, Toyota-cho, Toyota, Aichi, 471-8572, Japan Phone/ Fax : +81-565-72-9071/9147 Abstract Toyota introduced a new generation of hybrid vehicle to the market in September of 2003. The new Prius, equipped with a new Toyota-developed inverter system, is capable of outputting more power than the conventional systems. One of the strong points of this new system is that a Boost Converter has been placed between the inverter and the battery. The Boost Converter is capable of raising the voltage from the battery, enabling the inverter to drive a high power output motor. The Toyota Hybrid System (THS), consists of a high power motor, generator, and a battery of relatively lower power. When the Boost Converter was adopted in the THS, it was possible to keep bulk and cost of the additional unit in the system to a minimum, by letting the Boost Converter function to the same power level as the battery. The control system of the Boost Converter consists simply of a PI controller. By using existing sensors and microprocessors, it was possible to develop a new system at no additional costs. The Boost Converter’s control system achieves high efficiency by optimizing its output voltage according to the relative state of the motor and the generator. Toyota was able to achieve a 50% improvement in the motor power output with the new Boost Converter, while keeping a similar complexity of the conventional system. As of now, Toyota plans to spread the development to other new hybrid vehicles.__ Keywords: Hybrid, Electric Drive, Converter, Inverter, Control System Figure1: TOYOTA NEW PRIUS

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工作原理 工作原理 将标准的升压和回扫DC-DC转换器结合起来，就构成了图1c所示的混合电路。这种组合结构将次级绕组的回扫电压叠加到输入电压和初级绕组的回扫电压之上(标准的回扫转换器仅利用了次级端产生的回扫电压)。与标准的升压转换器相比，这种结构通过限制LX端电压，利用低压MOSFET产生了较高的输出电压。 变压器提供了下列优点： 更高的输出电压 较小的工作占空比 MOSFET上承受的电压更低 当变压器工作在非连续模式下，且MOSFET的峰值电流恒定时，还具有以下优点： 更高的开关频率产生的输出纹波更小 更高的纹波频率 较小的磁性元件 MAX1605以及其它许多升压转换器都能够采用这种结构。最高输出电压受限于变压器的匝数比、变压器和二极管的额定电压、MOSFET的额定电压和漏极电容、以及二极管的反向恢复时间。 标准升压电路 标准升压电路 标准的升压转换器如图1a所示。当MOSFET闭合时，电感电流线性上升；而当MOSFET 关断时，LX端电压飞升至VOUT + VD，同时电感电流线性下降。直观地，如果电感花费1/n 的时间向输出传输能量，则输出电压(VOUT)是输入电压(VIN)的n倍，由此导出下列关系式： 其中D为占空比。通过图3能够找出理论上的分析证明。这个证明的关键之处在于稳态工作，即电流向下的变化量等于电流向上的变化量： 图3. 分析图1a电路的电感电流将有助于确定占空比 这样，最终的电感电流等于起始的电感电流：