Design of a Driver IC- IR2110 for MOSFET in Half Bridge Drive A RESEARCH REPORT Submitted by
PALAK TRIVEDI (150290745006) In partial fulfilment for the award of the degree Of
IMASTERS OF ENGINEERING IN
POWER ELECTRONICS AND ELECTRICAL DRIVES
LALJIBHAI CHATURBHAI INSTITUTE OF TECHNOLOGY, BHANDU
GUJARAT TECHNOLOGICAL UNIVERSITY, AHMEDABAD JANUARY 2016
I
LALJIBHAI CHATURBHAI INSTITUTE OF TECHNOLOGY, BHANDU ELECTRICAL ENGINEERING DEPARTMENT JANUARY, 2016
CERTIFICATE
Date: This is to certify that the dissertation entitled “Design of a driver ICIR2110 for MOSFET in Half Bridge Drive” has been carried out by PALAK TRIVEDI, under my guidance in fulfilment of the degree of Masters of Engineering in Power Electronics and Electrical Drives (1st semester) of Gujarat Technological University, Ahmedabad, during the academic year 2015-16.
Guide:
Head of the Department
Prof. B.G. Panchal Electrical Engineering Department LCIT BHANDU
II
TABLE OF CONTENTS
Certificate......................................................................................................................II Table Of Contents.......................................................................................................III Abstract........................................................................................................................IV Chapter 1: Introduction...............................................................................................1-3 1.1 Overview........................................................................1 1.2 Problem Identification....................................................2 1.3 Objective........................................................................3 Chapter 2 : Literature Survey......................................................................................4-7 Chapter 3 : Driver IC – IR2110................................................................................8-15 3.1 Features..........................................................................8 3.2 Block diagram................................................................8 3.3 Lead Assignments..........................................................9 3.4 Pin Descriptions...........................................................10 3.5 Application in Half Bridge Drive................................12 3.6 Other Applications.......................................................15 Conclusion....................................................................................................................16 Future Scope.................................................................................................................16 References....................................................................................................................17
III
ABSTRACT
This Research project is based on the design of the MOSFET driver IC for high and low voltage side for Half bridge drive and various other applications. A Mosfet driver allows a low current digital output signal from a Microprocessor or microcontroller to drive the gate of a Mosfet. A 5 volt digital signal can switch a high voltage MOSFET using the driver. The driver has level shifting circuitry and sometimes a bootstrap circuit to allow the use of cheaper N type devices on the high side. A MOSFET has a gate capacitance that you need to charge so that the MOSFET can turn on and discharge it to switch off, the more current you can provide to the gate (sink/source) the faster you switching on/off the MOSFET. And hence a driver is used. The driver is used to provide the current and also drives the gates with an appropriate voltage level not high to avoid the risk of damaging the MOSFET but also high enough to produce a low drain source resistance when turned on.
IV
Introduction
CHAPTER-1
INTRODUCTION
1.1 Overview A gate
driver is
a power
amplifier that
accepts
a
low-power
input
from
a
controller IC and produces a high-current drive input for the gate of a high-power transistor such as an IGBT or power MOSFET. Gate drivers can be provided either onchip or as a discrete module. In essence, a gate driver consists of a level shifter in combination with an amplifier.
In contrast to bipolar transistors, MOSFETs do not require constant power input, as long as they are not being switched on or off. The isolated gate-electrode of the MOSFET forms a capacitor (gate capacitor), which must be charged or discharged each time the MOSFET is switched on or off. As a transistor requires a particular gate voltage in order to switch on, the gate capacitor must be charged to at least the required gate voltage for the transistor to be switched on. Similarly, to switch the transistor off, this charge must be dissipated, i.e. the gate capacitor must be discharged.
When a transistor is switched on or off, it does not immediately switch from a nonconducting to a conducting state; and may transiently support both a high voltage and conduct a high current. Consequently, when gate current is applied to a transistor to cause it to switch, a certain amount of heat is generated which can, in some cases, be enough to destroy the transistor. Therefore, it is necessary to keep the switching time as short as possible, so as to minimize switching loss.
Typical switching times are in the range of microseconds. The switching time of a transistor is inversely proportional to the amount of current used to charge the gate.
1
Introduction
Therefore,
switching
currents
are
often
required
in
the
range
of
several
hundred milliamperes, or even in the range of amperes.
For typical gate voltages of approximately 10-15V, several watts of power may be required to drive the switch. When large currents are switched at high frequencies, e.g. in DC-to-DC converters of large electric motors, multiple transistors are sometimes provided in parallel, so as to provide sufficiently high switching currents and switching power.
1.2 Problem Identification
The switching signal for a transistor is usually generated by a logic circuit or a microcontroller, which provides an output signal that typically is limited to a few milliamperes of current. Consequently, a transistor which is directly driven by such a signal would switch very slowly, with correspondingly high power loss.
During switching, the gate capacitor of the transistor may draw current so quickly that it causes a current overdraw in the logic circuit or microcontroller, causing overheating which leads to permanent damage or even complete destruction of the chip.
An output pin of a microcontroller is usually adequate to drive a small-signal logic level MOSFET. However, two issues occur when driving larger power MOSFETs: 1. Higher gate capacitance - Digital signals are meant to drive small loads (on the order of 10-100pF). This is much less than many MOSFETs, which can be in thousands of pF.
2. Higher gate voltage -
A 3.3V or 5V signal is often not enough. Usually 8-12V is
required to fully turn on the MOSFET. 2
Introduction
Finally, many MOSFET drivers are designed explicitly for the purpose of designing half bridge or H- bridge inverter for various applications. It's about maximizing the switching speed by dumping lots of current into the gate, so that the power MOSFET spends the least amount of time possible in the transition state, and therefore wastes less energy and doesn't get as hot.
1.3 Objective
A MOSFET driver IC translates TTL Or CMOS logical signals, to a higher voltage and higher current, with the goal of rapidly and completely switching the gate of a MOSFET.
The gate of a MOSFET is high impedance and requires essentially zero DC current. BUT, the gate has capacitance that must be charged up when it is switched on, and discharged when it is switched off.
If you drive the gate of a MOSFET with something that can not source much current (maybe a logic gate or micro-controller pin), it takes a while for the MOSFET gate capacitance to charge up. During this time when the gate is charging up, the MOSFET is partially on, operating in its linear region, and dissipating power. This will waste power and is inefficient, and in some cases could damage the MOSFET.
The solution in situations where its important to turn on a MOSFET quickly, is to use a gate driver that can source a lot of current to charge up the MOSFET gate quickly.
3
Literature Survey
CHAPTER-2
LITERATURE
In many situations, we need to use MOSFETs configured as high-side switches. Many a times we need to use MOSFETs configured as high-side and low-side switches, such as in bridge circuits. In half-bridge circuits, we have 1 high-side MOSFET and 1 low-side MOSFET. In full-bridge circuits we have 2 high-side MOSFETs and 2 low-side MOSFETs. In such situations, there is a need to use high-side drive circuitry alongside low-side drive circuitry. The most common way of driving MOSFETs in such cases is to use high-low side MOSFET drivers. Undoubtedly, the most popular such driver chip is the IR2110.
AN-978 Application Note:- According to an application note or the driver IC- IR2110 by International Rectifier, there are various design considerations for this driver IC to be taken care of.
International rectifiers IR2110 MOSFET driver can be used as high side and low side MOSFET driver. It have a floating circuit to handle to boostrap operation. IR2210 can with stand voltage upto 500v (offset voltage). Its output pins can provide peak current upto 2 ampere. It can also be used to as IGBT driver. IR2210 floating circuit can drive high side MOSFET upto 500 volt.
The gate drive requirements for a power MOSFET or IGBT utilized as a high-side switch (the drain is connected to the high voltage as shown in figure) driven in full enhancement (i.e. lowest voltage drop across its terminals) can be summarized as follows:
1. Gate voltage must be 10 V to 15 V higher than the source voltage. Being a high-side switch, such gate voltage would have to be higher than the rail voltage, which is frequently the highest voltage available in the system.
4
Literature Survey
2. The gate voltage must be controllable from the logic, which is normally referenced to ground. Thus, the control signals have to be level-shifted to the source of the highside power device, which, in most applications, swings between the two rails.
3. The power absorbed by the gate drive circuitry should not significantly affect the overall efficiency.
Figure 2.1 : MOSFET input voltage connections
For the primary gate-driver design considerations, an important attribute for the gate driver is its ability to provide sufficient drive current to quickly pass through the Miller Plateau Region of the power-MOSFET's switching transition. This interval occurs when the transistor is being driven on or off, and the voltage across its gate-to-drain parasitic capacitor (CGD) is being charged or discharged by the gate driver. Total gate charge (����� ) is how much must be supplied to the MOSFET gate to achieve full turn-on. It is usually specified in nanocoulombs (nC).
Looking at the datasheet for a MOSFET, the gate charge characteristic has a flat, horizontal portion (shown in figure below). That is the so-called Miller plateau. When the
5
Literature Survey
device switches, the gate voltage is actually clamped to the plateau voltage and stays there until sufficient charge has been added/ removed for the device to switch.
It is useful in estimating the driving requirements, because it evaluates the voltage of the plateau and the required charge to switch the device. Thus, you can calculate the actual gate drive resistor, for a given switching time.
The charge injected is given as a product of Gate current and switching time of MOSFET. ����� = ����� * ��� But,
����� =
��� −������� � ����
where ��� is the supply voltage of your driver (actually it should be its peak output
voltage, but often that is what we use for a quick estimate). Thus, you can select � ���� to obtain the required tsw, for a given device. ����� is the difference between the charges at the ends of the plateau.
Figure 2.2 : Gate charge characteristics 6
Literature Survey
Bo Wang, Naveen Tipirneni, Marco Riva [4]:- In this paper, the topology of the low-
power-loss high-speed drive circuit is introduced. The circuit reduces the overall power consumed in the driver and thus reduces the power loss. This is particularly important for high-frequency driver operation to take full advantage, in terms of efficiency. Many techniques have been proposed for driving semiconductor devices at high frequencies like resonant gate driving, which is most suitable for coping with the high-efficiency requirement of HFETs.
Yasser Nour, Shimaa F. Nagar, Mohammed Saad [5]:- MOSFET gate driving is similar to driving a very high impedance capacitive network. this is because of the fact that the gate is electrically isolated from the source by a silicon dioxide layer. So ideally no current flows into the gate when a DC voltage is applied. However a very small leakage current flows to maintain the gate voltage and also during the switching periods to change and discharge the device capacitances. In this paper, MOSFET switching behaviour is analysed so that an efficient gate driving circuit and effect of the total gate parasitic elements on the MOSFET switching time can be investigated.
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Driver IC
CHAPTER-3
Driver IC- IR2110
3.1 Features 1.
Floating channel designed for bootstrap operation
2.
Fully operational to +500V or +600V
3.
Tolerant to negative transient voltage
4.
dV/dt immune
5.
Gate drive supply range from 10 to 20V
6.
3.3V logic compatible
7.
Separate logic supply range from 3.3V to 20V
8.
Logic and power ground ±5V offset
9.
Cycle by cycle edge-triggered shutdown logic
10. Matched propagation delay for both channels 11. Outputs in phase with inputs.
3.2 Functional Block Diagram
Figure 3.1 : Block Diagram
8
Driver IC
3.3 Lead Assignments IR2110 comes in two packages – 14 pin through-hole PDIP package and the 16-pin surface mount SOIC package.
PDIP (plastic dual inline package) has a very small legs and gets near impossible to solder without specialized equipments like micro tipped soldering irons or hot airjet soldering.
SOIC (small outline ICs) are easy to solder and can also be fitted or mounted on a socket. User can use any of the above packages according to the requirement and cost effectiveness. Below figure shows two packaging types of IR2110.
Figure 3.2 : Package Diagrams of IR2110
The IR2110 are high voltage, high speed power MOSFET and IGBT drivers with independent high and low side referenced output channels. It has rugged monolithic construction. Monolithic refers to that whole electronic circuit is built on a single chip. The table below shows the lead descriptions of IR2110. The use of each pin is as mentioned. 9
Driver IC
Symbol
Description
V
Logic supply
HIN
Logic input for high side gate driver output (HO), in phase
SD
Logic input for shutdown
LIN
Logic input for low side gate driver output (LO), in phase
VSS
Logic ground
V
High side floating supply
HO
High side gate drive output
VS
High side floating supply return
LO
Low side gate drive output
V
COM
Low side supply
Low side return
3.4 Pin Descriptions 1. Pin 1 is output of low side MOSFET drive. The lower Mosfet of H bridge is to be connected to this pin and Pin 7 is the output of high side of the MOSFET, to which higher Mosfet of H bridge can be connected. 2. Pin 3 is the Vcc and is the low-side supply and should be between 10V and 20V. 3. Pin 9 is V . It is the logic supply to the IR2110. It can be between +3V to +20V (with reference to VSS). The actual voltage chosen depends on the voltage level of your input signals. It is as shown in graph below.
10
Driver IC
Figure 3.3 : Input Voltage Waveform It is common practice to use V
= +5V. When V
slightly higher than 3V. Thus when V
= +5V, the logic 1 input threshold is
= +5V, the IR2110 can be used to drive loads
when input “1” is higher than 3 point something volts. This means that it can be used for almost all circuits, since most circuits tend to have around 5V outputs.
When microcontrollers are used the output voltage will be higher than 4V, normally it is +5 volts. Using other PWM controller, ICs will probably be powered off at greater than 10V, meaning the outputs will be higher than 8V when high. So, the IR2110 can be easily used. If the V
is down to about 4V, desired result is not obtained.
4. Pin 13 is VSS and is for the logic supply ground. 5. Pin 2 is COM, “low side return” – basically, low side drive ground connection. It seems that they are independent and could perhaps isolate the drive outputs and drive signals. However, it would be wrong. While they are not internally connected, IR2110 is a non-isolated driver, meaning that VSS and COM should both be connected to ground.
11
Driver IC
6. Pin 10 and 12 gives HIN and LIN. They are the logic inputs. A high signal to HIN means that you want to drive the high-side MOSFET, meaning a high output is provided on HO. A low signal to HIN means that you want to turn off the high-side MOSFET, meaning a low output is provided on HO. 7. Pin 5 is VS . The output to HO – high or low – is not with respect to ground, but with respect to Vs. VS is the high side floating supply return. When high, the level on HO is
equal to the level on V , with respect to V . When low, the level on HO is equal to VS , with respect to VS , effectively zero.
8. A high signal to LIN means that you want to drive the low-side MOSFET, meaning a high output is provided on LO. A low signal to LIN means that you want to turn off the low-side MOSFET, meaning a low output is provided on LO. The output on LO is with respect to ground. When high, the level on LO is equal to the level of VCC, effectively ground. When low, the level on LO is equal to the level on VSS, effectively zero. 9. Pin 11 is SD, a shut down pin. When this pin is low, IR2110 is enabled – shutdown function is disabled. When this pin is high, the outputs are turned off, disabling the IR2110 drive.
3.5 Application In the Half Bridge Drive Figure below shows the common IR2110 configuration for driving MOSFETs in both high and low side configurations – a half bridge stage. The necessity and design of bootstrap circuitry is as explained below.
12
Driver IC
Figure 3.4 : Half Bridge Drive implementing IR2110
D1, C1 and C2 along with the IR2110 form the bootstrap circuitry. When LIN = 1, a signal for driving low side of MOSFET and Q2 is on, C1 and C2 get charged to the level of V , which is one diode drop below +V . When LIN = 0 and HIN = 1, a signal for driving high side of MOSFET, this charge on the C1 and C2 is used to add the extra voltage equal to V above the source level of Q1 to drive the Q1 in high-side configuration. A large enough capacitance must be chosen for C1 so that it can supply the charge required to keep Q1 on for all the time.
13
Driver IC
C1 must also not be too large that charging is too slow and the voltage level does not rise sufficiently to keep the MOSFET on. The higher the on time, the higher the required capacitance. Thus, the lower the frequency, the higher is the required capacitance for C1.
The higher the duty cycle, the higher is the required capacitance for C1. Yes, there are formulae available for calculating the capacitance. However, there are many parameters involved, some of which we may not know – for example, the capacitor leakage current. So, estimating the required capacitance, for low frequencies such as 50Hz, capacitance used is between 47µF and 68µF. For high frequencies like 30kHz to 50kHz, capacitance used is between 4.7µF and 22µF.
If an electrolytic capacitor is used, a ceramic capacitor should be connected in parallel with this capacitor. The ceramic capacitor is not required if the bootstrap capacitor is tantalum. A tantalum electrolytic capacitor, is a polarized capacitor whose anode electrode is made of tantalum on which a very thin insulating oxide layer is formed, which acts as the dielectric of the capacitor. The tantalum capacitor distinguishes itself from other conventional and electrolytic capacitors in having high capacitance per volume and lower weight.
D2 and D3 discharge the gate capacitances of the MOSFET quickly, bypassing the gate resistors, reducing the turn off time. R1 and R2 are the gate current-limiting resistors. +MOSV can be up to a maximum of 500V. +VCC should be from a clean supply. Filter capacitors and decoupling capacitors from +VCC to ground should be used for filtering.
Here R4 is the Gate to source resistors. They are really important on the design to prevent the burning or failing of MOSFET or damage of MOSFET driver IC. Gate to source resistors prevents accidental turn on of the MOSFET by external noise usually at startup when the gate is floating. The MOSFET may sometimes turn on with a floating gate because of the internal drain to gate "Miller" capacitance. A gate to source resistor acts as a pull-down to ensure a low level for the MOSFET.
14
Driver IC
3.6 Other Applications This driver IC- IR2110, apart from a half bridge drive, can be used in many other applications. Some of the important applications are as detailed below.
IR2110 can be used to drive MOSFETs of full bridge inverter configurations. The functionality is simple and same as that of half bridge. Here HIN-1 and LIN-1 are control signals for Front two MOSFETs in a full bridge and HIN-2 LIN-2 are for other two MOSFETs. Here HIN-1 is shorted to LIN-2 and HIN-2 is shorted to LIN-1, enabling the control of all 4 MOSFETs from 2 signal inputs, instead of four.
The IR2110 can be used as a single high-side driver. The circuit is simple enough and follows the same functionality as that of half bridge. One thing to remember is that, since there is no low-side switch, there must a load connected from OUT to ground. Otherwise the bootstrap capacitors cannot charge.
Similarly IR2110 can be used as a single Low-side driver too. Here the higher MOSFET pin will be kept open.
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CONCLUSION
This IR2110 demonstrates the design of high performance bootstrap gate drive circuits for high frequency, high power and high efficiency switching applications using MOSFETs and IGBTs. In most of the Switching applications, efficiency focuses on switching losses that are mainly dependent on switching speed. This driver IC improves the switching characteristics if high power drives.In some power conversion applications, input voltage level prohibits the use of direct gate drive circuits for driving high side of N-channel MOSFET or IGBT. Thus bootstrap circuitry is used which is main feature of IR2110. Hence this IC can be used as High Voltage gate driver Circuit.
FUTURE SCOPE
1. Can be used in different switching applications. 2. For low voltage applications this IC can be used to drive P-channel MOSFETs too. 3. Can be used with at the output of PWM controller for driving the switching devices of SMPS inverter.
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REFERENCES Papers [1] “Design and application guide of bootstrap circuit for high voltage Gate-driver ICs”, Application note AN-6076 by Fairchild semiconductors. [2] “High voltage Floating MOS gate driver IC”, Application note AN-978 by International Rectifiers. [3] “Datasheet on IR2110” by International Rectifier. [4] Bo Wang, Naveen Tipirneni, Marco Riva, Antonello Monti, Grigory Simin, and Enrico Santi "An Efficient High-Frequency Drive Circuit for Power FETs", IEEE 2009. [5] Yasser Nour, Shimaa F. Nagar, Mohammed Saad, “MOSFET Gate Drive Circuit Design Considerations for Integrated High Switching Frequency Converter”, Aswan Faculty of Engineering, South Valley University, 81542, Egypt, IEEE 2015.
Web Links [1] Article on “Bootstraping Function of IR2110”. (http://electronics.stackexchange.com/questions/58849/bootstrap-circuit-function)
[2]http://ele-tech.com/html/characteristic-and-application-of-the-driving-circuitir2110.html
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