This post was last edited by xutong on 2022-10-28 14:24
In power supply design, we often have to select MOS and look at the driving waveform. In most cases, the simulation software may not have the model we want for MOS and the driver. So how do I simulate this circuit?
There are some relatively complete drivers that can be used for configuration in Simplis, as shown in Figure 1
Figure 1: MULTI_LEVEL_DRIVER
It can be used to set some basic driver parameters. The official explanation of level 0~2 driver is as follows:
We can use level 1 modeling.
Now that we have the driver, don’t we have to find the tube?
Figure 2: Extract MOSFET parameters
Here we choose use -defined, go to Innoscience to find a tube, and fill it out according to the manual.
Figure 3: INN650D140A manual
Figure 4: Fill in MOS tube parameters based on INN650D140A
Figure 5: Building a basic BOOST circuit
Figure 6: Selecting transient simulation
Figure 7: Simulation results
In the actual circuit, if the wiring is not good, there may be inductance on the ground. Let's see what changes will occur to the driving waveform when there is inductance on the ground. The modified circuit is shown in Figure 8.
Figure 8: Driving waveform of the ground series inductor test
Figure 9: Driving spikes caused by improper wiring
Let's take a look at the changes in voltage ripple at different switching frequencies, as shown in the figure below when the switching frequency is 1Meg.
Figure 10: Test circuit
Figure 11: Ripple at 1 Megahz switching frequency
Figure 12: Ripple at 100Khz switching frequency
Is there any way to reduce the ripple without changing the switching frequency? Let’s try changing the inductance.
Figure 13: Inductor current ripple and output ripple voltage when the inductance is increased to 100uH
Although the ripple current is relatively low at this time, is it because the capacitance is insufficient that causes the ripple to be large? Let's increase the capacitance value and see?
Figure 14: VOUT after increasing the capacitance Capacitor 100u—>1m
Figure 15: Adding D1 current monitoring
Figure 16: Blue is D1 current
Figure 17: Cyan is the current of the capacitor
It can be seen from the voltage and current waveforms that when the MOS tube is turned off, the load current flows through the output capacitor, and when the MOS tube is turned on, the two currents flow together.
When the switching frequency is higher, the inductor ripple current is smaller. When the switching frequency remains unchanged, increasing the inductance can reduce the inductor ripple current.
That’s all for today, bye~
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