To control the speed and rotation direction of the DC motor we need some type of motor driver, one of the most popular schematics is H-Bridge. For the low current and voltages, we can use some integral solutions like L293D and so on. But if we need more power and reliability we have to build some custom H-bridge using Mosfet transistors. This type of transistor requires careful and proper driving itself. One of the most popular integral solutions for driving MOSFETs is IR2110 from Infineon.
In this article, we will discuss how to use this IC to build a powerful DC motor driver.
IR2110 is a high voltage (up to 500V) chip which is suitable to drive various types of the MOSFET and IGBT. This device contains both low-side and high-side half-bridge drivers.
You can find pins description and other parameters in datasheet.
Here is a typical schematic
This is a half-bridge driver, which means that LOAD pin can be connected to LOAD SUPPLY or to AGND, depending on the state of the input pins ENABLE HI and ENABLE LO. These signals can be a static voltage of the logic levels (3.3 to 5 volts) or some pulse signals like PWM.
Controlling of the Q2 MOSFET is very simple and doesn’t require extra schematics.
With Q1 all things are a little bit more complicated since the SOURCE pin of this transistor is floating without a direct connection to the power supply negative line.
To be able to enable this transistor we need to create a “virtual” zero point and additional power is required.
This problem can be solved using bootstrap circuitry.
You can see diode D5 and two capacitors C1 and C2. When the low-side is active (Q2 is opened) both capacitors are charging through the diode from the IR2110 power supply (typically 12V). Then when the high-side becomes active these capacitors are using to charge Q1 gate and open this transistor.
The value of C1 depends on switching frequency and duty cycle. Typically this value is in the range 4.7 – 22 microfarads.
Of course, there is a formula that can be used to calculate a proper value. Please read this appnote if you want to know more about floating and bootstraps circuits.
But also you can select the proper capacitor value experimentally. Proper value is guaranteed that the capacitor can discharge quickly enough to close transistor and charge quickly enough to reach the required voltage value. Better to use tantalum capacitors but the electrolyte is also Ok but the additional ceramic bypass is required.
Diodes D1 and D2 provide a quick discharge circuit so both transistors can be closed immediately.
Diodes D7 and D9 protect MOSFETs from the large inductive loads and very necessary when driving motors.
Two resistors R5 and R6 are used to limit the charging current of the gates to protect transistors.
R2 and R1 is an additional protection circuit that prevents floating of the Gate pin and protects transistors from the enabling.
When both transistors enabling at the same time is a big problem called shoot through. This is equivalent to a short circuit that can destroy both MOSFETs and ruin your day.
To avoid shoot-through of the MOSFETs we need to ensure that ENABLE HI and ENABLE LO input pins are not activating at the same time.
One of the ways is to use a simple protection circuit which is placed near the IR2110 input pins.
74HC00N is a quad 2-input NAND gate that acts like a cross-locking circuit.
A by-product of this schematic is inverting of the signal so we need to invert the actual input signal before.
So when IN HI is low (for example) – output pins 6 and 8 are in the high state and pin 6 driving actually IR2110 ENABLE HI input.
At the same time pin, 8 activates T2 transistor which pulls down ENABLE LOW line which protects this line from the unauthorized activation.
Another part of the schematics with T1 works in the same way.
Full bridge driver.
To build a full H-bridge we need two identical halves of the half-bridge.
In this case ENABLE HI of the first IR2110 should be connected to the ENABLE LOW of the second IR2110 and vice versa.
The load is connecting between LOAD terminals of both halves.
Here is a full schematic of the driver which I use for big 110 volt motors.
This device contains all protection circuits described above and also provides galvanic isolation on inputs so we can safely connect the microcontroller as a PWM signal source.
This board requires two stabilized power supplies 5 and 12 volts. The actual bridge is powering from the separate 110-volt source.
Also, you can find a current measurement circuit based on the hall-effect sensor ACS712. This part is not mandatory and is simply used in my current project.
Diodes D11 and D12 are highly recommended for reliability. This diode provides a path for possible reverse currents (in case of long lines between drivers board and controller) in bad EMI conditions. Even small reverse current can damage optocouplers led.
The values of the R9 and R10 should be selected for your variant of 74HC00. It may be or 570 ohms or 3.8 kiloohms. To debug this part you need a scope, which can help you to control the form of the signal after 74HC00. But if you don’t have one – just replace resistors till the schematic became working.
UPD: I found that it's better to don't install C22 and C23 capacitors. So don't use them.
Completed boards with medium power transistors.
And another variant with big transistors on the radiator. This device is able to drive more than 2 kilowatts load.
As you can see powerful MOSFETs are placed on radiators, away from the driver boards.
This is permissible, but wire between boards and transistors should be as short as possible. Also, it’s a good idea to twist the SOURCE and GATE line as a differential pair, this allows us to minimize inductance.
Protection resistors on these lines should be placed as close as possible to the transistors.
You can see everything in the photos above.
Laboratory tests of this driver.
As a PWM signal source, I’m using Siglent signal generator in Pulse mode. The frequency is 15 kHz, the duty cycle is changing which is causes changes in motor rotation speed.
Thanks for reading!
Hope this material will be helpful.