“This paper analyzes the loss composition of the inverter, compares the performance of the fourth generation IGBT and the seventh generation IGBT through thermal simulation, and finally verifies the conclusion through experiments. Under the same working conditions, the loss and junction temperature of IGBT7 are significantly lower than those of IGBT4, so that the volume of the inverter can b...
This article mainly introduces Renesas Electronics (also known as: Renesas Note 1) the selection and characteristics of high-voltage MOS in the development of customer power supplies and other products, and provides reference design advice for customer product development.
MOSFET is widely used in power supply and other products due to its advantages of voltage control, high switching frequency and fast switching speed. Renesas high-voltage MOS covers drain-source voltage (VDSS) levels of 600V, 800V, 900V, and 1400V, with extremely low RDS(ON) and rich package series, and is widely used.
The two most important parameters of a MOSFET are the drain-source voltage (VDSS) and the on-resistance RDS(ON). The current value and the maximum power dissipation value must be observed carefully, as they are only reached when the backplane temperature reaches 25OC, and the switching time is only applicable if the specific conditions described in the data sheet are met.
Generally speaking, the Renesas high-voltage MOS data sheet mainly contains the following parts: characteristics, limit values, electrical characteristics and typical characteristics.
The performance advantages of Renesas high-voltage MOS:
1. Has a relatively low Qg
2. Vgs voltage ±30 V
3. Has a relatively low on-resistance
4. Good avalanche resistance
RenesasMOS adopts five generations of UMOS technology, which can make the RDS(ON) relatively small. The on-resistance of 2SK3298B is only 0.75 ohms, which can greatly reduce the loss of MOS.
The Limits section gives the absolute maximum values for the 10 parameters. The device must not exceed this value during operation, otherwise the MOS will be permanently damaged. Among them, it is especially important to note that the values of drain current and dissipation power are given at 25OC, and can only be used as a reference in actual operation.
The electrical characteristics part mainly contains several important parameters: turn-on and turn-off time parameters, transconductance parameters, junction capacitance parameters, and body diode parameters. Renesas high-voltage MOS is generally faster than other brands of MOS of the same type, but there is a very important prerequisite: the gate drive voltage should be above 10V, because the Renesas high-voltage MOS junction capacitance parameter is relatively large.
The Typical Characteristics section gives dynamic curves for many parameters. The more important parameter curves are: thermal resistance curve, transfer characteristic curve, transconductance curve, the relationship between on-resistance and drain current, and the relationship between dissipated power and temperature. The dissipated power decreases with increasing temperature, and the on-resistance increases with increasing temperature.
The Renesas high-voltage MOS has obvious advantages of low on-resistance and fast switching speed, but the quality of the driving circuit directly affects the characteristics of the MOS. In order to achieve a good driving waveform and switching characteristics, so that the tube can work in an ideal state, it is now analyzed in conjunction with the influence of several parameters in the data sheet and the typical curve Note 2.
1. The variation curve of RDS(ON) with VGS:
It can be seen from the figure that when VGS is less than 10V, RDS(ON) is relatively large, especially when it is less than 7-8V, RDS(ON) is almost infinite, and the tube is hardly turned on. Therefore, we recommend that the driving voltage should be generally above 10V, so that a relatively low on-resistance can be obtained and the loss of MOS can be reduced.
2. The CISS, COSS, and CRSS of the Renesas high-voltage MOS obtained from the data sheet are relatively large, so in order to obtain a better driving waveform, it is recommended that the gate driving resistance should not be too large, and try to be in tens of ohms.
3. Transconductance parameters and curves. Transconductance is a very important parameter of MOS, which reflects the control ability of gate drive voltage to drain current. It can be seen from the transfer characteristic curve in the figure below: when the MOS gate drive voltage is about 10V, the MOS drain current can reach the nominal value.
Some characteristics of Renesas pressure MOS are matched with some parameters in order to achieve better switching characteristics.Now to summarize the above points, Renesas authorized agent Shiqiang Telecom
1. The gate driving voltage should be above 10V, which can obtain better driving waveform and lower on-resistance, which can reduce the heat generation and loss of MOS.
2. It is best to make a suitable choice between the EMI and the driving waveform for the gate drive resistance, preferably tens of ohms, and the driving resistance is 25 ohms in the test conditions of the parameters in the Renesas data sheet.
3. Because Renesas high-voltage MOS gate-source withstand voltage is relatively high, it can reach 30V. Therefore, when the load is heavy or the drain current is relatively large, in order to prevent the drain current runaway MOS from entering the amplification area, the gate drive voltage should be appropriately increased, as long as it does not exceed the nominal 30V.
Note 1: In this article, Renesas high-voltage MOS refers to the original NEC Electronic part.
Note 2: The curve in this article is from the Renesas 2SK3298B (600V, 7.5A) data sheet.