Speed control using pwm pdf

Duty cycle refers the amount of time it is on. In such a state, an LED would not be operational. It would simply be off. This means the power is off. They turn the current fully on and fully off.

They just vary the amount of time that it is on instead. The additional heat generated by traditional transistor circuits is another consideration, as it may increase the amount of time that cooling fans have to stay on to reduce the temperature of said devices.

The tiny power source controls the large one with the help of power transistors. This concept is what enables highly sophisticated microcontrollers often called MCUs and other computers to control very large currents at a reasonable cost. You must log in to post a comment. A PID loop—verbosely known as proportional, integral, differential loop—is a popular algorithm in many closed loop systems. The speed of a DC motor is proportional to the voltage applied to the motor.

When using digital control, a pulse-width modulated PWM signal is used to generate an average voltage. Additionally it is possible to load a speed reference file and let the GUI control the speed DC Motors are widely used in industries for various purposes. It is a doubly fed system. Many situations demand change in the speed of the DC Motor. This makes it a necessity to employ a method to effectively control the speed of a separately excited DC motor.

Step Response Comparison 0. The controllers were implemented to run the motor as real time application under speed and load variation conditions and showed the superiority of Fuzzy-PID. Due to its excellent speed control dc motor speed control using pi controller: The Figure 4 shows the model of PI controller for DC motor.

BLDC motor has various application used in industries like in drilling, lathes, spinning, electric bikes etc. The speed control of the DC motors is very essential. This proposed system … This paper presents a DC motor speed controlling technique under varying load condition. One of the applications used here is to control the speed of the DC motor. These controllers improve the transient performance of the motor.

The output of controller is fed to the controlled voltage source. The inverter circuit is fed by this voltage source. The speed of DC Motor can be varied by varying the input reference voltage. The two voltages, reference and signal voltage are continuously compared and the difference of these voltages is fed to PID controller which is made are proposed for the speed control design of BLDC motor [4].

However, Conventional PID controller algorithm is simple, stable, easy adjustment and high reliability, Conventional speed Attached is the simulink model I have created for an assignment. For the assignment, we are tasked with using PWM and a control strategy e. A transistor can block voltage in the forward direction only asymmetric blocking. The feedback diode, as shown, is an essential element for chopper and voltage-fed converter applications.

Double or triple Darlington transistors are available in module form with matched parallel devices for higher power rating. Power transistors have an important property known as the second breakdown effect. This is in contrast to the avalanche breakdown effect of a junction, which is also known as first breakdown effect.

When the collector current is switched on by the base drive, it tends to crowd on the base-emitter junction periphery, thus constricting the collector current in a narrow area of the reverse-biased collector junction. This tends to create a hot spot and the junction fails by thermal runaway, which is known as second breakdown. The rise in junction temperature at the hot spot accentuates the current concentration owing to the negative temperature coefficient of the drop, and this regeneration effect causes collapse of the collector voltage, thus destroying the device.

Two stage Darlington transistor with bypass diode 2. If the gate voltage is positive and beyond a threshold value, an N-type conducting channel will be induced that will permit current flow by majority carrier electrons between the drain and the source. Although the gate impedance is extremely high at steady state, the effective gate-source capacitance will demand a pulse current during turn-on and turn-off. The device has asymmetric voltage- blocking capability, and has an integral body diode, as shown, which can carry full current in the reverse direction.

The diode is characterized by slow recovery and is often bypassed by an external fast-recovery diode in high-frequency applications. Many designers view IGBT as a device with MOS input characteristics and bipolar output characteristic that is a voltage-controlled bipolar device.

It combines the best attributes of both to achieve optimal device characteristics. The IGBT is suitable for many applications in power electronics, especially in Pulse Width Modulated PWM servo and three-phase drives requiring high dynamic range control and low noise. IGBT improves dynamic performance and efficiency and reduced the level of audible noise.

It is equally suitable in resonant-mode converter circuits. Optimized IGBT is available for both low conduction loss and low switching loss. It has a very low on-state voltage drop due to conductivity modulation and has superior on-state current density. So smaller chip size is possible and the cost can be reduced. Low driving power and a simple drive circuit due to the input MOS gate structure.

It can be easily controlled as compared to current controlled devices thyristor, BJT in high voltage and high current applications. Wide SOA. It has superior current conduction capability compared with the bipolar transistor.

It also has excellent forward and reverse blocking capabilities. The collector current tailing due to the minority carrier causes the turnoff speed to be slow. There is a possibility of latchup due to the internal PNPN thyristor structure. The IGBT is suitable for scaling up the blocking voltage capability.

In case of Power MOSFET, the on-resistance increases sharply with the breakdown voltage due to an increase in the resistively and thickness of the drift region required to support the high operating voltage. In contrast, for the IGBT, the drift region resistance is drastically reduced by the high concentration of injected minority carriers during on-state current conduction.

The forward drop from the drift region becomes dependent upon its thickness and independent of its original resistivity. Thus by varying the pulse-width, we can vary the average voltage across a DC motor and hence its speed.

Ymax The circuit of a simple speed controller for a mini DC motor, such as that used in tape recorders and toys, is shown in Fig2. The heat dissipation problem often results in large heat sinks and sometimes forced cooling. PWM amplifiers greatly reduce this problem because of their much higher power conversion efficiency. The PWM power amplifier is not without disadvantages. The desired signal is not translated to a voltage amplitude but rather the time duration or duty cycle of a pulse.

This is obviously not a linear operation. But with a few assumptions, which are usually valid in motor control, the PWM may be approximated as being linear i. The linear model of the PWM amplifier is based on the average voltage being equal to the integral of the voltage waveform. The duty cycle must be recalculated at each sampling time. Pulse width modulation technique PWM is a technique for speed control which can overcome the problem of poor starting performance of a motor.

PWM for motor speed control works in a very similar way. Instead of supplying a varying voltage to a motor, it is supplied with a fixed voltage value such as 12v which starts it spinning immediately. The wave forms in the below figure to explain the way in which this method of control operates. In each case the signal has maximum and minimum voltages of 12v and 0v. By varying the mark space ratio of the signal over the full range, it is possible to obtain any desired average output voltage from 0v to12v.

The motor will work perfectly well, provided that the frequency of the pulsed signal is set correctly, a suitable frequency being 30Hz. Pulse Width Modulation Waveforms 2.

Block Diagram of an Analogue PWM Generator The simplest way to generate a PWM signal is the intersective method, which requires only a saw tooth or a triangle wave form easily generated using a simple oscillator and a comparator.

When the value of the reference signal is more than the modulation wave form, the PWM signal is in the high state, otherwise it is in the low state. Digital Method: The digital method involves incrementing a counter, an comparing the counter value with a pre-loaded register value, or value set by an ADC. They normally use a counter that increments periodically and is reset at the end very period of the PWM. When the counter value is more than the reference value, the PWM output will change state from high to low.

Many of these are designed for use in switch mo power supplies. The can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide up to four timing circuits in one package.

Fig 3. In phase with output. The trigger and reset inputs pins 2 and 4 respectively on a are held high via pull-up resistors while the threshold input pin 6 is simply floating. Thus configured, pulling the trigger momentarily to ground acts as a 'set' and transitions the output pin pin 3 to Vcc high state. Pulling the reset input to ground acts as a 'reset' and transitions the output pin to ground low state. No timing capacitors are required in a bistable configuration. Pin 5 control voltage is connected to ground via a small-value capacitor usually 0.

Pin 7 discharge is left floating. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C. While using the timer IC in monostable mode, the main disadvantage is that the time span between any two triggering pulses must be greater than the RC time constant.

Conversely, ignoring closely spaced pulses is done by setting the RC time constant to be larger than the span between spurious triggers. Resistor R1 is connected between VCC and the discharge pin pin 7 and another resistor R2 is connected between the discharge pin pin 7 , and the trigger pin 2 and threshold pin 6 pins that share a common node.

Hence the capacitor is charged through R1 and R2, and discharged only through R2, since pin 7 has low impedance to ground during output low intervals of the cycle, therefore discharging the capacitor. The power capability of R1 must be greater than. Particularly with bipolar s, low values of must be avoided so that the output stays saturated near zero volts during discharge, as assumed by the above equation.

Otherwise the output low time will be greater than calculated above. To have an output high time shorter than the low time i. This bypasses R2 during the high part of the cycle so that the high interval depends only on R1 and C, with an adjustment based the voltage drop across the diode. The low time will be the same as above, 0. The equation reduces to the expected 0.