Isolated Gate Driver Circuit with TLP250 or IR2113 (IR2110) IC

Introduction

Unlike BJTs which are currentcontrolled, MOSFETs are voltagecontrolled elementsMOSFET transfer characteristic is proportional to the drain current to gate voltage ratio. Power MOSFETs in switching applications are used in cutoff and linear regions. In other words, the MOSFET is like a variable resistor with voltage, which varies its resistance from M to m. The MOSFET’s ohmic function makes it easy to parallel them. The IGBT structure is taken from the combination of BJT and MOSFET. IGBTs are also voltagecontrolled devices. IGBTs are suitable for highpower applications with switching frequencies less than 150 kHz. These devices are very suitable for AC drives. MOSFETs are suitable for highfrequency and lowpower applications [1]. Totem pole driver is one of the best MOSFET drivers, so that there is a NPN transistor on the source path and a PNP transistor on the sink path. One transistor is in common emitter configuration and other is in emitter follower configuration. These transistors are used in linear region for reducing the delay time [1]. In common driver ICs two N-type MOSFETs are used. Low output impedance of driver reduces the turn on time of MOSFETs. MOSFET drivers can also be used for IGBTs. Pulse transformer also can be used as isolated gate driver, but due to the possibility of saturation, it can’t be used in applications with low switching frequency.

Isolated Gate Driver with TLP250 or IR2113 (IR2110) IC is used for driving the MOSFETs or IGBTs of the half-bridge, full bridge and H-bridge circuits. 

IR2113 (IR2110) IC

The IR2110/IR2113 are high voltage, high speed power MOSFET and IGBT drivers with independent high and low side referenced output channels. Proprietary HVIC and latch immune CMOS technologies enable ruggedized monolithic construction. Logic inputs are compatible with standard CMOS or LSTTL output, down to 3.3V logic. The output drivers feature a high pulse current buffer stage designed for minimum driver cross-conduction. Propagation delays are matched to simplify use in high frequency applications. The floating channel can be used to drive an N-channel power MOSFET or IGBT in the high side configuration which operates up to 500 or 600 volts. [3]

Isolated Gate Driver

IR2113 IC

Isolated Gate driver with IR2113 / (IR2110) IC

To isolate the microcontroller supply from the power circuit, a high-speed opto-coupler called “6n137” will be used. According to the ON-Semiconductor datasheet, this IC has a speed of 10MBit / s and is therefore very suitable for high-frequency switching applications. According to the Truth Table in the datasheet, if pin 7 is NC or connected to ground, in input 1 output will be 0 and in input 0 output will be 1. In this case, the circuit should be designed to compensate this NOT operation. To do this, we connect the anode (pin number 2) to the microcontroller 3.3 V or 5 V and the cathode (pin number 3) to the microcontroller PWM output. This IC will isolate our microcontroller from the power circuit. 

The MOSFETs or IGBTs, which are voltage-controlled devices, have a capacitor in their gate. When this capacitor is charging, the MOSFETs or IGBTs are turned on, and are turned off by discharging this capacitor. This capacitor requires a specific current to be charged and discharged in a short time. The capacitor must be charged at the lowest possible time so that the MOSFET turns on without delay. To turn on the N-type MOSFETs, the voltage applied to the gate should be greater than the source voltage, and since the source in the low side MOSFETs is always connected to the ground, applying a voltage of about 10 to 20 volts to the gate is enough. For P-type MOSFETs, the same is done with a little change. The gate voltage in the P-type MOSFETs must be lower than the source voltage, and since the source voltage is always constant, applying a voltage lower than the source voltage to the gate is appropriate. IGBTs are just Ntype. High side IGBTs, because they are of type N, require a higher gate voltage than Emitter voltage to be turned on. When the IGBT in on state, the voltage of the emitter will be equal to the collector voltage; and since the collector is always connected to the highest voltage (bus voltage), the emitter will also have this voltage. In simple terms, it is necessary that the high side IGBTs gate, have a voltage greater than the bus voltage to turn on. This state is called Power Floating. In fact, for turning on the high side IGBTs, a voltage greater than the maximum available voltage is required. But how is that possible? Assuming a bus voltage of 500 V, if the low side IGBT needs 15V in its gate to turns on, the high side IGBT should receive 515 V in its gate to fully turns on. So, we need a Dlevel Shifter circuit. 

Design and implementation of Isolated Gate Driver with IR2113 / (IR2110) IC

IR2113 IC is very suitable for driving the MOSFETs or IGBTs of the half-bridge, full bridge and H-bridge circuits. IR2113 is a high and low side driver. Totem pole configuration is used in this IC. This IC has a DC level shifter unit. The level shifter, changes the level of digital input voltage based on the bus voltage. This IC use a bootstrap capacitor and bootstrap diode for driving the high side MOSFET and can operate in 600V bus voltage. Perhaps the most important disadvantage of these drivers, is that the input is not isolated from the output. But the great advantages of this IC completely cover its disadvantages. As previously mentioned, this IC works on the basis of bootstrap, which means that the bootstrap capacitor should always be charged and discharged. According to Fig. 1, the VS pin or pin 5 will be connected to the source of the high side MOSFET, which this pin will be connected to the VB pin or pin 6 of IR2113 IC with the bootstrap capacitor. The bootstrap capacitor is charged with the bootstrap diode when the high MOSFET is off. To select the bootstrap capacitor, according to the AN978-b application note, we use the following formula [2]: 

Isolated Gate Driver

Qg = Gate charge of high side FET 

 = frequency of operation 

Icbs (leak) = Bootstrap capacitor leakage current 

Vf = Forward voltage drop across the bootstrap diode V 

VLS = Voltage drop across the low side FET or load 

Qls = level shift charge required per cycle = 5nC (500V/600V IC’s) or 20nC (1200V IC’s)  

Iqbs = quiescent current for the high side driver circuitry

Isolated Gate Driver (with IR2113 / (IR2110) IC) functional block diagram

Isolated Gate Driver

Isolated Gate Driver Functional Block Diagram [3]

The Altium (version 17.1) and PDF files of isolated gate driver of half bridge topology schematic can be downloaded from the following link (Password: ElectroDiscovery.com):

Isolated Gate Driver (with IR2113 / (IR2110) IC)

Design and implementation of Isolated Gate Driver with TLP250 IC

TLP250 can be used as isolated driver for MOSETs and IGBTs. For low side MOSFETs the drivers supply, can have a common ground but for high side MOSFETs the drivers supply, should have separate ground from each other and from low side drivers. The following figure shows the schematic of this driver circuit. 

Isolated Gate Driver

Isolated gate driver with TLP250 schematic

The Altium (version 17.1) and PDF files of Isolated gate driver with TLP250 schematic can be downloaded from  the following link (Password: ElectroDiscovery.com):

Isolated gate driver with TLP250

For high side MOSFET driving with TLP250 the pin 5 also should be connected to the MOSFET’s source and the power supply ground of TLP250 should be separate from any other ground.

Conclusion

In this page we introduced an isolated gate driver with two IC types (TLP250 and IR2113). Also the Altium (version 17.1) and PDF files of Isolated gate driver with TLP250 and IR2113 are included.

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