Moazzam Hussain

PE LAB PROJECT H-Bridge using IR2104 PREPARED BY: MOAZZAM HUSSAIN USAMA ZAIN - EE-17B OBJECTIVE: The purpose of this project was to design an H Bridge which can be used to control the speed of DC motors. INTRODUCTION: H-BRIDGE: The basic principle of this H-Bridge is that alternate MOSFETs will be on at a time. For example, Q1 and Q4 can on or Q3 and Q2 can be on. The direction can be controlled using the combinations given. If Q1 and Q4 are on, then the motor starts spinning If Q2 and Q3 are on then the motor starts spinning in the opposite direction. However, Q1 and Q2 or Q3 and Q4 can not be on otherwise this will create a short circuit path directly to the ground which will destroy the bridge. The speed of the motor can be controlled by varying the pulse width, the time for which these transistors will be on. IR2104: This IC is an isolated half-bridge gate driver. It is used to control the gates of high and low Nchannel MOSFETs, its fast-switching time and low output impedance makes it very accurate and is most preferred in Bridges. Its typical connection is given below. CIRCUIT DIAGRAM: APPARATUS: • • • • • • IR2104 N-Channel MOSFET Resistor Diode Capacitor Function generator • Power supply PROCEDURE: First of all, design the circuit as per the requirement The circuit has been designed above and the driver IC was used to for switching the transistors. 2 switching ICs were used to control the full bridge. The input of the first IC was inverted and given to the input of the second IC so that only alternate transistors can stay on at a time. WORKING: Pulse width is given as input to the ICs at PIN2. The ICs get input which is inverted to each other. As the input of IC#1 is direct input from the function generator, and the input to IC#2 is the inverted input using a not gate. The IC shutdown pin PIN3 is set high as it is active low triggered. The inverted input is very necessary for the working function of H-Bridge. When high pulse is applied to the IC, the PIN 7 gets high and gives output pulse with peak at VCC+ VCC of MOSFETS. The PIN5 gets low as it functions as the opposite of PIN 7. Their opposite functionality is very important as this turns on only 1 MOSFET at a time. So, when high pulse is applied to 1 IC, however IC2 will get low pulse at the same instant. So, PIN 7 will be low at that instant hence MOSFET Q3 will be off and MOSFET Q4 will be on. hence an alternate path is created Q1 and Q4 are on. The pin Vs will provide constant voltage of VCC which drives the lower MOSFETS by giving them VCC. RESULTS: CLOCKWISE ROTATION: The input of function generator was given to IC2 and the input of IC1 was the invert of the function generator ANTICLOCKWISE ROTATION: The input of function generator was given to IC1 and the input of IC2 was the invert of the function generator Not Gate Input Not gate output Not gate Input/ Output in one frame IC1 Ho and Vo (Faulty one) IC2 HO Theoretical IC2 LO pin 5 Theoretical IC2 HO vs LO Theoretical DISCUSSION: First PWM is generated by function generated for testing from where we can change the duty cycle as well and feed this to a not gate IC 7404 which is then connected to Pin 2 of IC IR 2104. Apply at SDN pin3 of IC 2104 logic 1 (5V or 3.3V). In order to control speed change duty cycle of input signal Duty Cycle Speed For testing in order to reverse the direction of rotation feed the input from output of not gate to Pin2 of IC 2104. CONCLUSION: We successfully designed a full bridge that controls the speed of the motor by varying pulse width. Unfortunately, the direction of the motor could not be controlled due to some technical unknown reasons