--- title: "Inverter definition; buck switching regulator" subject: "Advanced Electronics" chapter: 8 key: "semester_4/advanced_electronics:inverter-buck-switching-regulator" source: https://www.bctengineer.com/q/semester_4/advanced_electronics/inverter-buck-switching-regulator site: BCT Engineering --- # Inverter definition; buck switching regulator Advanced Electronics · Chapter 8: Switched Power Supplies - Asked in: 2071 Chaitra, 2+5 marks - Video: [How does Buck Converter work? | DC-DC Converter - 1](https://www.youtube.com/watch?v=W6NOV6b8kxs) — Explorer - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_4/advanced_electronics/inverter-buck-switching-regulator - Whole chapter: https://www.bctengineer.com/md/semester_4/advanced_electronics/chapter-8 ## Question What is an inverter? Explain the Buck switching regulator with required necessary diagram and waveforms. ## Short answer An inverter converts DC to AC of required voltage and frequency using switches. A buck switching regulator steps DC voltage down with Va = k·Vs, using a switch, diode, inductor, and capacitor; current ramps up when switch is on and freewheels when off, with ripple ΔI = Va(Vs−Va)/(fLVs). ## Answer #### Inverter An **inverter** is a power electronic converter that changes **DC into AC** of the required voltage and frequency by switching SCRs, MOSFETs or IGBTs in a fixed sequence. Common types are single-phase half-bridge and full-bridge inverters. Uses: UPS, solar power systems, AC motor drives and induction heating. #### Buck switching regulator A Buck regulator steps DC voltage **down**: Va = k·Vs, where k = Ton/T. ```text Q (switch) L iL +Vs ---/ ----+------uuuu----+----+------+ | | | | Dm (↑) C LOAD Va | | | | − ---------+--------------+----+------+ ``` **Mode 1 – Q ON (0 < t < kT):** Dm is reverse biased; Vs drives current through L to C and the load. iL rises linearly from I1 to I2: ```text Vs − Va = L·ΔI/t1 ``` **Mode 2 – Q OFF (kT < t < T):** The inductor current freewheels through Dm. iL falls from I2 to I1: ```text Va = L·ΔI/t2 ``` **Waveforms:** ```text Q gate |‾‾‾|____|‾‾‾|____ 0 kT T vD |Vs | |Vs | | |____| |____ 0 iL I2 | /\ /\ I1 |_/ \__/ \__ Va |~~~~~~~~~~~~~ (average with small ripple) ``` **Relations:** ```text (Vs − Va)·kT = Va(1 − k)T → Va = k·Vs ΔI = Va(Vs − Va)/(f·L·Vs) ΔVc = ΔI/(8·f·C) ``` The average voltage across the diode (vD) equals Va, since the average inductor voltage is zero. Efficiency is high (about 90 %) because Q is either fully ON or fully OFF. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does an inverter do? A. Converts AC to DC B. Converts DC to AC of required voltage and frequency C. Steps DC voltage down D. Rectifies AC with SCRs Answer: B. An inverter changes DC to AC by switching devices in a fixed sequence. (Key point: Inverter) 2. When Q is ON in the buck regulator, what is true? A. Dm is reverse biased and iL rises linearly B. Dm conducts and iL falls C. The inductor current is zero D. Va equals zero Answer: A. With Vs applied through L, Vs − Va = L·ΔI/t1, so iL rises, and Dm is off. (Key point: Buck Mode 1) 3. What is the output of the buck regulator? A. Va = Vs/(1 − k) B. Va = k·Vs C. Va = −k·Vs/(1 − k) D. Va = Vs/k Answer: B. Equal rise and fall of current gives (Vs − Va)kT = Va(1 − k)T, so Va = kVs. (Key point: Output relation) 4. What is the average voltage across the diode? A. Zero B. Equal to Va, because the average inductor voltage is zero C. Equal to Vs D. Equal to Vs − Va Answer: B. Average voltage across L is zero, so the average of vD equals Va. (Key point: Diode voltage) ## Related in Advanced Electronics - [Buck regulator numerical (12 V to 6 V)](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-regulator-12v-numerical) — Advanced Electronics, chapter 8 - [Buck regulator numerical (14 V to 6 V)](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-regulator-14v-numerical) — Advanced Electronics, chapter 8 - [Buck regulator operation and derivation](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-regulator-operation) — Advanced Electronics, chapter 8, asked 2× - [Buck-boost regulator numerical (Vs = 10 V)](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-boost-10v-45-percent) — Advanced Electronics, chapter 8, asked 3× - [Buck-boost regulator numerical (Vs = 15 V)](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-boost-15v-40-percent) — Advanced Electronics, chapter 8, asked 3× - [Buck-boost regulator output and ripple derivation](https://www.bctengineer.com/question.md?key=semester_4%2Fadvanced_electronics%3Abuck-boost-derivation) — Advanced Electronics, chapter 8 ## Related in other subjects - [Three-phase SPWM inverter switching instants](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Aspwm-switching-instants) — Power Electronics, chapter 5, asked 3× - [PWM half-bridge inverter switching instants](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Apwm-inverter-switching-instants) — Power Electronics, chapter 5 - [180° inverter waveforms VRY, VYB, VBR, VNO, VRN](https://www.bctengineer.com/question.md?key=semester_7%2Fpower_electronics%3Ainverter-180-line-neutral-waveforms) — Power Electronics, chapter 5 - [Switching and why necessary](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aswitching-meaning-necessity) — Computer Networks and Security, chapter 2