SNOAAA7 April   2024 LMG3522R030

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Overview of Inverter Model
    1. 2.1 Power Stage
    2. 2.2 Control and Modulation Method
  6. 3Realization of Digital Control Using C-Script Block
    1. 3.1 Overview of Project Structure
    2. 3.2 AC Voltage Sampling and True RMS Value Calculation
    3. 3.3 Multiple Loop Control
      1. 3.3.1 Voltage Loop With Notch Filter
      2. 3.3.2 Current Loop With PI Compensator Anti-Windup
      3. 3.3.3 Sinusoidal and Sawtooth Wave Generator
      4. 3.3.4 Totem-Pole Modulation and Dead-Time Control
  7. 4Simulation Results
  8. 5Summary
  9. 6References

1 Introduction

Inverters are widely used in various applications. For example, solar inverters, uninterruptible power supplies (UPS), and onboard chargers (OBC) utilize an inverter to convert DC power to AC. In these systems, the inverter performance has a significant impact on the performance of the entire system. So, many topologies and control algorithms are proposed and investigated to improve the performance of the inverter. One effective way to preliminarily verify the feasibility and performance of the converter is simulation. Besides, digital control is widely used to control the power stage in realistic situations and code is more flexible than a control block in simulation software. Hence, the purpose of this application note is to introduce the implementation of a single-phase off-grid inverter with digital control, and another purpose is to verify the performance of totem-pole modulation with multiple loop control. In conventional control methods, the input signal of the voltage loop comes directly from the sampling AC voltage in output. But in this application note, the RMS value of the output voltage is used as the reference value in the voltage loop. The benefit of this method is discussed in this note.

The PMP23338 is TI's 3.6kW, single-phase totem-pole bridgeless power factor correction (PFC) circuits reference design with e-meter function. The totem-pole bridgeless structure allows this reference design to support the inverter function. Two active half bridges form this topology: one half bridge works at a low frequency and the other one works at a high frequency.

The high-frequency half bridge in the PMP23338 consists of two LMG3522R030 devices. LMG3522R030 is TI's 650V GaN FET with an integrated driver and protection. Compared with Si FETs, the GaN FETs switching loss is much lower due to the lower COSS. In addition, the unique structure of the GaN FETS brings zero reverse recovery charge, which further improves the performance of GaN FETs at high frequencies.