EIE4402: Note on Guided assignment: Design of a Circuit-Programmed Controlled Boost Converter using LTSpice & UC3842

EIE4402 Power Electronics

Objectives:

1. To understand the importance of computer-aided design of switching power supplies;

2. To learn and understand the basic functionalities of SPICE circuit simulation software;

3. To gain hands-on experience in the design, construction, and testing of basic converter.

1. Getting Started with LTspice

To download the latest version of LTspice, go to:

Download LTSpice

To view YouTube video of the quick start guide: https://youtu.be/JRcyHuyb1V0

To view the online document “LTspice Getting Started Guide”, go to:

https://www.analog.com/media/en/simulation-models/spice-models/LTspiceGettingStartedGuide.pdf?modelType=spice-models

2. Simulating Boost Converter Using LTspice

Design Specifications:

Input voltage range	20 V ~ 28 V
Nominal output voltage	48 V
Rated output current	1 A
Line regulation @ 1-A load	< 2%
Load regulation @ 24-V input voltage	< 2%
Switching frequency	50 kHz ~ 100 kHz
Output voltage ripple @ switching frequency	< 200 mV_pp
Startup rise time	< 1 s
Startup overshoot	< 5 %
Transient output voltage’s overshoot/undershoot	< 5% (0.25 A«0.75 A step at 0.1 A/µs)
Efficiency	> 90%

Spice models for the following devices are included in the model library“eie402.lib”.

Device Name	Model Name	Model Type
FQP33N10 (N-Channel Power MOSFET)	FQP33N10	Sub-circuit
MUR820 (Power Rectifier)	Dmur820	Diode
S-R Flip-Flop	SRFF	Sub-circuit
Comparator	COMP	Sub-circuit
Error Amplifier	ERRAMP	Sub-circuit
Average Model for Current-Programmed-Controlled Boost Converter	BOOSTCM	Sub-circuit

(a) Open Loop

Figure 1: Boost converter with open loop.

(a) Open Loop

Draw the schematics of figure 1 as shown above.

For the voltage source V2, modify as voltage pulses (in LTSpice, right-click):

Simulate and Left-click the probe on R2 to measure the voltage output of the boost converter.

Simulation Results:

V(n003) (blue-color) is the voltage output of the boost converter, and V(n005) is the voltage of V2, DC pulses.

From the above graph, we can see that the voltage output of the boost converter goes to 80 V from time = 0 to 2.5 mS. Then it goes down to 48 V at about 40 mS.

Results:

Voltage mode - screen 1: