Buck Converter LTSpice Simulation

Orbital EPS Team – Investigate LTspice Simulation for Buck Converter 3V3

Task: Buck Converter LTspice Investigation

Owner: Kaviyan Jeyakumar

Last Updated: March 22, 2025

Status: Active Simulation Phase

1.0 Project Charter & System Requirements

1.1 Objective

To create a high-fidelity digital twin of the Electrical Power System (EPS) in LTspice, starting with the buck converter sub-system. The simulation will be used to analyze power converter behavior, validate the feedback loop's stability and response time, and test the power efficiency under various operational conditions.

1.2 Core System Requirements

Parameter	Requirement	Status
Target IC	Richtek RT8297B	Model Unavailable
Selected Sim IC	LTC3633A	In Use for Workflow Dev
Input Voltage	17 V	✓
Output Voltage	3.0 V - 3.3 V	✓
Switching Freq.	~800 kHz	✓
FB Reference	0.6 V	✓

2.0 Project Overview & Background

2.1 What Are We Doing and Why?

At its core, this project is about building a digital twin of our satellite's power system. We build a virtual model of our EPS buck converter 3V3 model in LTspice to run several simulations.

2.2 What is a Buck Converter?

A buck converter is an electrical device that efficiently converts a high voltage into a lower, stable voltage. In our satellite, the solar panels might provide a fluctuating high voltage (e.g., 17V), but our sensitive electronics need a very precise and stable low voltage (e.g., 3.3V) to function. The buck converter's job is to "step down" the voltage reliably.

2.3 Understanding the Key Components in Our Simulation

Here is a simple breakdown of each part in our LTspice schematic.

V1 (The Power Source): This represents the power coming from our solar panels. For now, it's a stable 17V source. Later, we will connect this to a more realistic solar panel model.
U1 (The Buck Converter IC): This is the brain of the operation. It's a special-purpose chip (like the LTC3633A) that makes all the decisions to keep the output voltage stable.