The introduction of IGBT and Drive Circuit Design
Published time: 2018-06-26
The description of the IGBT
IGBT,full name in English, Insulated Gate Bipolar Transistor, is a composite fully-controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS (insulated gate field effect transistor) .It has the advantages of both the high input impedance of the MOSFET and the low turn-on voltage drop of the GTR.The GTR saturation voltage is low, current density is high, but the drive current is large. The MOSFET has low drive power and fast switching speed, but has a large turn-on voltage drop and low current density.
IGBTs combine the all advantages of the GTR and MOSFET,IGBTs has low drive power and reduced saturation pressure. It is very suitable for converter systems with DC voltages of 600V and the above of 600v, such as AC motors, frequency converters, switching power supplies, lighting circuits, and traction drives.
What is the IGBT module
The IGBT module is a modular semiconductor product formed by IGBT (insulated gate bipolar transistor chip) and FWD (diode chip) through a specific circuit bridge package; packaged The IGBT module,which has packaged can be directly applied to the inverter, UPS uninterruptible power supply equipment and other devices.
What is the working principle of IGBT.
The IGBT tube is a switch that is on-off switch. It consists of a BJT (bipolar transistor) and MOS (insulated gate field effect transistor). The IGBT is based on the voltage transformation of its gate source , by this it can complete the operation. When the gate source plus +12V (more than 6V, generally take 12V to 15V), the IGBT is turned on.The IGBT is turned off when no voltage is applied to the gate source or a negative voltage is applied.Negative pressure can be achieved to reliable shutdown.
The structure of the IGBT tube is as follows:
As shown in the figure, there are three terminals for the IGBT: G, D, S. After the voltage is applied across G and S, the internal electrons transfer (the characteristics of semiconductor materials, which is why the use of semiconductor materials for power electronic switches,) is that there is a one-to-one correspondence between positive ions and negative ions, and the semiconductor material is neutral, but after the voltage is applied, the electrons accumulate to one side due to the voltage, it will forme a conductive channel ,because the electrons can conduct electricity. Finally it becomes a conductor. If you remove the voltage across the GS, the conductive channel will disappear, and it will becomes electrically conductive and become an insulator.
If a positive driving voltage is applied between the gate and emitter of the IGBT, the MOSFET is turned on, so that the collector and base of the PNP transistor will become a low resistance state,fianlly making the transistor conductive.If the voltage between the gate and the emitter of the IGBT is 0V, the MOSFET is turned off and the supply of the base current of the PNP transistor is cut off, so that the transistor is turned off.
It can be seen that the safety and reliability of IGBT is mainly determined by the following factors:
-- Voltage between the gate and emitter of the IGBT;
-- IGBT collector and emitter voltage;
-- Current flowing through the IGBT collector-emitter;
-- The junction temperature of the IGBT.
If the voltage between the gate and emitter of the IGBT, the driving voltage is too low, the IGBT will not operate stably and normally. If the voltage is too high and exceeds the withstand voltage between the gate and emitter, the IGBT will be permanently damaged.Similarly,If the allowable voltage between the collector and emitter of the IGBT exceeds the withstand voltage between the collector and the emitter, the current between the IGBT collector and the emitter exceeds the maximum current allowed by the collector-emitter, and the junction temperature of the IGBT exceeds With the allowable junction temperature, IGBTs may be permanently damaged.
The description of IGBT driver circuit design.
The role of IGBT drive circuit
The function of the IGBT driver circuit is to drive the IGBT module, so that it can operate normally and protect the IGBT module at the same time. The role of the IGBT drive circuit is very important for the entire IGBT system. IGBT is the core device of the circuit, it can be turned on under high voltage and shut off under high current. In hard-switching bridge circuit,it plays a vital role that whether the power device IGBT can be used correctly and reliably .
To meet the requirements of driving the IGBT,the drive circuit is to amplify the PWM signal output by the control circuit.The design of the drive circuit is directly related to that use the IGBT safely and reliably IGBT driver circuit provides for IGBT devices that gate over voltage, short circuit protection, over current protection, over temperature protection, Vce overvoltage protection (active clamp), gate undervoltage protection, and didt protection (short circuit overcurrent protection Kind).
The details of IGBT driver circuit design
1. Jotrin Electronics think that when we design the IGBT drive circuit, we need to consider the performance parameters
1) The forward and reverse peak voltages that the IGBT withstands in the circuit can be derived from the following formula:
When designing the driver circuit, it is necessary to take into account the 2-2.5 times safety factor. The voltage of the optional IGBT is 1200V.
2) The peak current that the IGBT needs to withstand when it is turned on in the circuit can be derived from the following formula:
How to select the IGBT driver
Electronics Engineer,from Jotrin Electronics Limited think：
In the actual circuit,when we face the choice of the gate resistor,we needs to consider the switching speed requirement and the size of the loss. The gate resistance is not as small as possible. When the gate resistance is small, the voltage spike between CEs of the IGBT is too large. When the gate resistance is large, the switching loss increases. Therefore, when selecting the IGBT driver, the gate resistance should be appropriately reduced within the range of the peak voltage. Because the stray inductance in the circuit will cause voltage and current spikes and ringing in the switching state, the wiring should be as short as possible in the actual driving circuit, and the driving circuit and the absorption circuit should be arranged on the same PCB board. A bidirectional Zener is added between the GEs near the IGBT to clamp the resulting voltage spike coupled to the gate.
For high power IGBTs, the design and selection drive is based on the following parameter requirements: device off bias, gate charge, resistance to solid and power conditions. The positive bias VGE of the gate circuit negative bias voltage -VGE and gate resistance RG size, have different degrees of influence on the IGBT's on-state voltage drop, switching time, switching loss, withstand short circuit capability and dv/dt current and other parameters .The change in the positive gate voltage has a great influence on the turn-on characteristics of the IGBT, the load short-circuit capability, and the dVcE/dt current, while the negative gate bias has a greater effect on the turn-off characteristics. In the design of the gate circuit, attention should also be paid to the turn-on characteristics, load short-circuit capability, and false triggering caused by the dVcE/dt current.
The importance of IGBT test evaluation
Nowadays, IGBTs have become the mainstream of high-power components and dominate the market. Due to advances in science and technology, the demand for thin and light and high-performance power electronic devices has led to the development of IGBTs, especially in the fields of electrical equipment, optoelectronics, aerospace, railways, power conversion, etc., which will enable semiconductor development technicians to meet market demand. Next, the technology for the development of high-power components continues to break through.
In addition to the good function of the semiconductor device , its various parameters can meet the requirements of the circuit and it must be measured on a regular basis, otherwise the quality characteristics of the product are difficult to guarantee, especially for larger power components, due to wear, easy aging ,the efficiency is reduced, because the imbalance causes burnout, so it is more important to screen and check the parameters of new products and components in use.
It is absolutely not enough for medium and high power components to be functionally perfect, because they must withstand the maximum voltage and current specified in the specification. Under certain conditions, the maximum tolerance data is called the parameter of this component. If the operating conditions of a component exceed its parameter data, the component may burn out immediately or cause permanent damage.
When high-power components are used to test the conduction parameters, the current must be large enough to withstand the normal operating values. At the same time, the voltage must be high enough for the leakage current test of the shutdown parameters. The state of current and voltage, so that the extent of its aging can be apparent, when these two parameters pass, it means that the components are basically good, and then for further measurement of other parameters.
Jotrin Electronics limited has advanced testing equipment that can be fully qualified for testing tasks during high power such as IGBT to identify the advantages and disadvantages of them and provide customers with better products.