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Analog Design Voltage Regulator Minh Thuy LE Department of Instrumentation and Industrial Informatics (3I), School of Electrical Engineering (SEE), Hanoi University of Science and Technology (HUST), Vietnam thuy.leminh@hust.edu.vn 10/2022 Content Introduction Basic linear regulators Integrated circuit voltage regulators 28/02/2023 Analog Design – Le Minh Thuy Introduction • DC voltage regulators are used to: • Providing power source for microelectric system such as: Op-amp, transistor,… • Standard power source for sensor systems • … • DC voltage regulators are divided into two types: • Linear regulator • Switching regulator 28/02/2023 Analog Design – Le Minh Thuy Introduction • DC voltage regulators: • Input: usually DC voltage with drastic change (output of a rectifier + filter) • Output: Stable DC voltage value (within the change of input and load) • Voltage regulator factor: represent the ability of a power supply to maintain a constant output for a change of input/load • Line regulation • Load regulation 28/02/2023 Analog Design – Le Minh Thuy Introduction Line regulation: measure the ability to maintain a constant output for changes in the input voltage • There are two expression: Line regulation = Line regulation = 28/02/2023 Δ𝑉𝑜𝑢𝑡 100% (𝑚𝑉/𝑉) Δ𝑉𝑖𝑛 Δ𝑉𝑜𝑢𝑡 /𝑉𝑜𝑢𝑡 Δ𝑉𝑖𝑛 100% (%/𝑉) or (%/𝑚𝑉) Analog Design – Le Minh Thuy Introduction Load regulation: measure the ability to maintain a constant output with varied load resistance • There are many expression for load regulation in datasheets • It can be calculated and expressed as a percentage using following equation: 𝑉𝑁𝐿 − 𝑉𝐹𝐿 Load regulation = × 100% 𝑉𝐹𝐿 With 𝑉𝑁𝐿 is the output voltage with minimum load (no load) and 𝑉𝐹𝐿 is the output voltage with maximum load (full load) Ideally, the percent load regulation is 0% 28/02/2023 Analog Design – Le Minh Thuy Introduction Load regulation: • Sometimes manufactures specify the equivalent output resistance of a power supply 𝑅𝑂𝑈𝑇 instead of load regulation: • Therefore we have: Load regulation = 𝑅𝑂𝑈𝑇 𝑅𝐹𝐿 × 100% In some datasheets, the %/mA expression is used, example: 0.01%/mA means a change in 1mA current will lead to 0.01% change 28/02/2023 in voltage Analog Design – Le Minh Thuy Introduction Example • A DC voltage supply have: • • Voltage with no load (𝐼𝐿 = 0) = 12.1 V Voltage with full load (𝐼𝐿 = 200𝑚𝐴) = 12 V • Calculate the load regulation? • Calculate the output resistance with no load? 28/02/2023 Analog Design – Le Minh Thuy Linear regulator • Series regulators • Shunt regulators 28/02/2023 Analog Design – Le Minh Thuy Linear regulator Series regulators Series voltage regulator 28/02/2023 Analog Design – Le Minh Thuy 10 Step-up Regulators • 𝑉𝑂𝑈𝑇 > 𝑉𝐼𝑁 28/02/2023 Electronic Design – Le Minh Thuy 30 Step-up Regulators • When Q1 is ON 28/02/2023 Electronic Design – Le Minh Thuy 31 Step-up Regulators • When Q1 is OFF 28/02/2023 Electronic Design – Le Minh Thuy 32 Voltage-Inverter 𝑉𝑂𝑈𝑇 and 𝑉𝐼𝑁 are opposite in sign 28/02/2023 Electronic Design – Le Minh Thuy 33 Voltage-Inverter When Q1 is ON → D1 is OFF 28/02/2023 Electronic Design – Le Minh Thuy 34 Voltage-Inverter When Q1 is OFF → D1 is ON 28/02/2023 Electronic Design – Le Minh Thuy 35 IC Regulators • Linear Voltage Regulators - 78xx, 79xx - LM317, LM337 • Switching Voltage Regulators - 78S40 28/02/2023 Electronic Design – Le Minh Thuy 36 IC 78xx 28/02/2023 Electronic Design – Le Minh Thuy 37 IC 79xx 28/02/2023 Electronic Design – Le Minh Thuy 38 IC LM317 Adjustable Positive Linear Voltage Regulators 28/02/2023 Electronic Design – Le Minh Thuy 39 IC LM317 28/02/2023 Electronic Design – Le Minh Thuy 40 IC LM317 Adjustable Negative Linear Voltage Regulators 28/02/2023 Electronic Design – Le Minh Thuy 41 IC 78S40 • Can be used with external components to provide stepup, step-down, and inverting operation 28/02/2023 Electronic Design – Le Minh Thuy 42 IC 78S40 – Step-down Configuration 28/02/2023 Electronic Design – Le Minh Thuy 43 IC 78S40 – Step-up Configuration 28/02/2023 Electronic Design – Le Minh Thuy 44