H桥电机驱动原理与应用-中英文对照.doc

H桥电机驱动原理与应用
原著：吉姆布朗 1998年4月
整理上传：鲍勃乔丹 2002年9月
翻译：韦文潮 2007年12月

我们首先来看马达是如何转动的呢？举个例子：你手里拿着一节电池，用导线将马达和电池两端对接，马达就转动了；然后如果你把电池极性反过来会怎么样呢？没有错，马达也反着转了。

OK，这个是最基本的了。现在假设你想用一块指甲盖大小的微控制芯片(MCU)。你又如何控制马达的呢？首先，你手上有一个固态的状态开关——一个晶体管——来控制马达的开关。

提示：如果你用继电器连接这些电路的时候，要在继电器线圈两端并一个二极管。这是为了保护电路不被电感的反向电动势损坏。二极管的正极（箭头）要接地，负极要接在MCU连接继电器线圈的输出端上。

电路连接好后，你可以用一个逻辑输出的信号来控制马达了。高电平（逻辑1）让继电器导通，马达转动；低电平（逻辑0）让继电器断开，马达停止。

在电路相同的情况下，把马达的“极性”反过来接，我们可以控制马达的翻转和停止。

问题来了：如果我们要同时需要马达能够正转好反转，怎么办？难道每次都要把马达的连线反过来接？

我们先来看另一个概念：马达速度。当我们在其中一种状态下，频繁的切换开关状态的时候，马达的转速就不再是匀速，而是变化的了，相应的扭矩也会改变。通常反应出来的是马达速度的变化。

我们想要同时控制正反向的话，就需要更多的电路——没错，就是H桥电路。H桥电路的“H”的意思是它实际电路在电路图上是一个字幕H的样式。下图就是一个用继电器连接成的H桥电路。

处于“高”位置的继电器是控制电源流入的方向，称之为“源”电路；处于“低”位置的继电器是控制电源流入地的方向，称之为“漏”电路。

现在，你将左上电路（A）和右下电路（D）接通，马达就正转了（如下图）。此时各个端口的逻辑值为A-1、B-0、C-0、D-1.

将逻辑值反过来，电路的方向就调转了，马达反转（如下图）。此时逻辑值为A-0、B-1、C-1、D-0。

注意：千万不能将同一侧的两个电路同时接通，否则会在电源和地之间形成短路。比如A和C或者B和D同时为1.

半导体H桥：现在我们来讨论使用场效应管连接的H桥。

这是我们实际使用的H桥电路的真正形式。我们现在不需要在继电器两端接二极管了，不过还是要在控制管两端接。下图是电路图。

在图上我们看到晶体管代替了继电器。在高位的晶体管必须是PNP型三极管或者P沟道场效应管；低位的晶体管必须是NPN型三极管或者N沟道型场效应管。

如果你将两个高位电路或者两个低位电路同时接通，你的马达会自动制动。这是因为当没有电源供给时，马达在自由转动的情况下是处于发电状态，同位的电路接通，相当于将马达的两端“短接”，那么马达会因为短路而相当与接了一个无限大功率的电炉即一个很大的负载，所以马达就会产生“电”制动；当你把马达两端悬空后，它就恢复自由了。

为了以避免马达的反电动势的危害，我们仍然需要在晶体管两端接二极管，因为马达线圈在电路开闭瞬间产生的反向电动势通过会高过电源，这样对晶体管和电路会有很大的影响甚至烧毁零件。

半导体晶体管本身有导通电阻，在通过大电流时会明显发热，如果没有散热措施会很容易烧毁。这样就会限制电路功率的增加。

Mosfets（金属氧化物半导体场效应晶体管），这里简称MOS管，由于结构和原理的不同，导通电阻远比普通三极管低，允许流过更大的电流。而且MOS管都内置有反向二极管来保护管子本身。所以采用MOS管连接H桥不但效率可以提高，电路也可以简化。

使用MOS管搭建H桥，高位电路要用P沟道管；低位要用N沟道管。因为N沟道管比P沟道管便宜的多，所以有人用N沟道管在高位，加上削波电路来抑制反电动势。

应用H桥的关键是四个电路开闭状态的准确。一旦在电源和地之间出现通路，毫无疑问会立刻产生短路，让你的晶体管变成一枚小炸弹。下面我们介绍一些H桥的集成电路，这样我们可以更容易更安全的使用H桥。

常用H桥集成电路

L293内置两个H桥，每个桥提供1A的额定工作电流，和最大2A的峰值电流。它能驱动的马达一般是不超过35毫米照片胶卷筒大小。

L298内置两个H桥，每个桥提供1A的额定工作电流，和最大3A的峰值电流。它能驱动的马达不超过可乐罐大小。

LMD18200内置1个H桥，工作电流2~3A，峰值电流6A。它驱动可乐罐大小的马达。

当然还有很多H桥集成电路，这里就不一一介绍了。

好了！关于马达和H桥我们就说到这里了，祝你玩得愉快！

请访问DPRG H-Bridge Project，获取更多H桥DIY的详细资源。

L298集成电路应用实验
原著：吉姆布朗 1998年4月
整理上传：NCC 2002年8月
翻译：韦文潮 2007年12月

概要

本电路实验主要使用一片L298加上1000微法电容和12个二极管。目的是制作一个便携式的两路马达驱动电路，提供微处理器控制接口。该L298应用电路的设计者是克莱迪蒙。

电路板只需要单面覆铜板即可，在元件面可以印刷加上接口说明和元件引线说明。

电路板

电路图

PCB印刷图

说明：L298的1、2端控制马达A的开关、正反，enable A 控制脉宽；3、4端和enable B控制马达B。

该电路图版权遵照第二版或者以上的通用公共授权（GNU GPL），任何人可以将此电路应用与任何场合、任何用途，并不受限制的修改或者改进，这些修改或改进同样对所有人公开。
· Brief H-Bridge Theory of Operation
April 1998, Written by Jim Brown September 2002, page format revised, links updated by Bob Jordan
What's all this talk about H-Bridges? How do they work? Well let's see . . .
How do we make a motor turn? You take a battery; hook the positive side to one side of your DC motor. Then you connect the negative side of the battery to the other motor lead. The motor spins forward. If you swap the battery leads the motor spins in reverse.
Ok, that's basic. Now lets say you want a Micro Controller Unit (MCU) to control the motor, how would you do it? Well, for starters you get a device that would act like a solid state switch, a transistor, and hook it up the motor.
NOTE: If you connect up these relay circuits, remember to put a diode across the coil of the relay. This will keep the spike voltage (back EMF), coming out of the coil of the relay, from getting into the MCU and damaging it. The anode, which is the arrow side of the diode, should connect to ground. The bar, which is the Cathode side of the diode, should connect to the coil where the MCU connects to the relay.

If you connect this circuit to a small hobby motor you can control the motor with a processor (MCU, etc.) Applying a logical one, (+12 Volts in our example) to point A causes the motor to turn forward. Applying a logical zero, (ground) causes the motor to stop turning (to coast and stop).

Hook the motor up in this fashion and the circuit turns the motor in reverse when you apply a logical one (+12Volts) to point B. Apply a logical zero, which is usually a ground, causes the motor to stop spinning.
If you hook up these circuits you can only get the motor to stop or turn in one direction, forward for the first circuit or reverse for the second circuit
Motor Speed You can also pulse the motor control line, (A or B) on and off. This powers the motor in short burst and gets varying degrees of torque, which usually translates into variable motor speed.
But if you want to be able to control the motor in both forward and reverse with a processor, you will need more circuitry. You will need an H-Bridge. Notice the "H"-looking configuration in the next graphic. Relays configured in this fashion make an H-Bridge. The "high side drivers" are the relays that control the positive voltage to the motor. This is called sourcing current.
The "low side drivers" are the relays that control the negative voltage to sink current to the motor. "Sinking current" is the term for connecting the circuit to the negative side of the power supply, which is usually ground.

So, you turn on the upper left and lower right circuits, and power flows through the motor forward, i.e.: 1 to A, 0 to B, 0 to C, and 1 to D.

Then for reverse you turn on the upper right and lower left circuits and power flows through the motor in reverse, i.e.: 0 to A, 1 to B, 1 to C, and 0 to D.

CAUTION: You should be careful not to turn on both circuits on one side or the other, or you have a direct short which will destroy your circuit; Example: A and C or B and D both high (logical 1).
Semiconductor H-Bridges We can better control our motor by using transistors or Field Effect Transistors (FETs).
Most of what we have discussed about the relays H-Bridge is true of these circuits. You don't need diodes that were across the relay coils now. You should use diodes across your transistors though. See the following diagram showing how they are connected.
These solid state circuits provide power and ground connections to the motor, as did the relay circuits. The high side drivers need to be current "sources" which is what PNP transistors and P-channel FETs are good at. The low side drivers need to be current "sinks" which is what NPN transistors and N-channel FETs are good at.

If you turn on the two upper circuits, the motor resists turning, so you effectively have a breaking mechanism. The same is true if you turn on both of the lower circuits. This is because the motor is a generator and when it turns it generates a voltage. If the terminals of the motor are connected (shorted), then the voltage generated counteracts the motors freedom to turn. It is as if you are applying a similar but opposite voltage to the one generated by the motor being turned. Vis-ã-vis, it acts like a brake.
To be nice to your transistors, you should add diodes to catch the back voltage that is generated by the motor's coil when the power is switched on and off. This flyback voltage can be many times higher than the supply voltage! If you don't use diodes, you could burn out your transistors.

Transistors, being a semiconductor device, will have some resistance, which causes them to get hot when conducting much current. This is called not being able to sink or source very much power, i.e.: Not able to provide much current from ground or from plus voltage.
Mosfets are much more efficient, they can provide much more current and not get as hot. They usually have the flyback diodes built in so you don't need the diodes anymore. This helps guard against flyback voltage frying your MCU.
To use Mosfets in an H-Bridge, you need P-Channel Mosfets on top because they can "source" power, and N-Channel Mosfets on the bottom because then can "sink" power. N-Channel Mosfets are much cheaper than P-Channel Mosfets, but N-Channel Mosfets used to source power require about 7 volts more than the supply voltage, to turn on. As a result, some people manage to use N-Channel Mosfets, on top of the H-Bridge, by using cleaver circuits to overcome the breakdown voltage.
It is important that the four quadrants of the H-Bridgecircuits be turned on and off properly. When there is a path between the positive and ground side of the H-Bridge, other than through the motor, a condition exists called "shoot through". This is basically a direct short of the power supply and can cause semiconductors to become ballistic, in circuits with large currents flowing. There are H-bridge chips available that are much easier, and safer, to use than designing your own H-Bridge circuit.
H-Bridge Devices The L 293 has 2 H-Bridges, can provide about 1 amp to each and occasional peak loads to 2 amps. Motors typically controlled with this controller are near the size of a 35 mm film plastic canister.
The L298 has 2 h-bridges on board, can handle 1amp and peak current draws to about 3amps. You often see motors between the size a of 35 mm film plastic canister and a coke can, driven by this type H-Bridge. The LMD18200 has one h-bridge on board, can handle about 2 or 3 amps and can handle a peak of about 6 amps. This H-Bridge chip can usually handle an average motor about the size of a coke. There are several more commercially designed H-Bridge chips as well.
There! That's the basics about motors and H-Bridges! Hope it helps and be safe!
See also the DPRG HBridge Project for a do-it-yourself H-Bridge design with full schematic and PCB artwork.

L298 H-Bridge PCB Project
April 1998, by Jim Brown August 2002, page format revised, links update by NCC
Project Summary
The goal of this project is to create a carrier board for an L298 H-Bridge with 1000mf cap, 12 diodes, a terminal block for power and two motors, and a header for interfacing with a microcontroller. The board is based on a simple L298 H-Bridge design by Clay Timmons.
Note that the board can be made using just the bottom artwork. The top artwork is informational only and contains text explaining diode orientation and pinouts.

Photo of assembled v1.1 L298 H-Bridge Board

Color image of v1.0 PCB artwork
Schematic Diagram

You use in1 & in2 for direction and enablea for pwm for motor 1 You use in3 & in4 for direction and enableb for pwm for motor 2
The L298 H-Bridge PCB artwork is licensed under version 2 or later of the GNU GPL. This means everyone has the freedom to use this design for any purpose, to study it, to copy it, to distribute it, and to change or improve it, provided such changes are also made freely available to everyone.