“As we all know, the boost chip is used in many Electronic circuits. In modern life, the boost chip is one of the indispensable devices. For boost chips, everyone must have a certain understanding. In this article, I will mainly explain the principle of the boost chip and the analysis of some common boost and buck circuits. I wonder if you are familiar with this boost chip and its application. Let’s learn together!

“

As we all know, the boost chip is used in many electronic circuits. In modern life, the boost chip is one of the indispensable devices. For boost chips, everyone must have a certain understanding. In this article, I will mainly explain the principle of the boost chip and the analysis of some common boost and buck circuits. I wonder if you are familiar with this boost chip and its application. Let’s learn together!

Voltage regulating circuit diagram

Step-up and step-down generally refer to the working mode of the power supply circuit. Some power supply ICs can support both step-up and step-down modes.

Step-down mode-Bust mode, this is familiar to everyone, and it is used more, such as 5V-》3.3V voltage regulator. Many of the corresponding chips can be searched on the Internet. There are LDO mode and DC-DC mode. . Among them, the peripheral circuit of the chip in LDO mode is relatively simple, and only need to add filter capacitors to the input and output ends. The DC-DC mode chip circuit is relatively more complicated, but the efficiency is higher. Generally, an external capacitor and inductor are required. The inductor is charged by closing the switch. After the switch is turned off, the inductor is discharged as a power supply. The output voltage value can be adjusted by the duty cycle of PWM, and the maximum voltage value will not exceed the power supply voltage. The basic circuit for DC-DC step-down mode is shown in the figure below:

Boost mode-Boost mode, this is also very common, and it is also a kind of DC-DC. When the entire circuit only uses a single power supply (such as a 3.7V lithium battery) to supply power, the IC can be powered by a lower voltage such as 3.3V and 1.6V through the step-down output. Sometimes a higher voltage is required in the circuit, such as some mobile devices. The screen needs to be driven by a higher voltage, such as 12V. It is not realistic to add a 12 independent power supply to the mobile device, and the lithium battery is generally 3.7V (full charge is 4.2V), this time you need to use the boost The circuit is complete. This also has a corresponding IC. Generally, it is necessary to cooperate with inductors and capacitors to achieve different DC-DC connection methods in boost and buck modes. The inductor is charged by closing the switch, and when the switch is opened, the electromotive force of the inductor is connected in series with the power supply to increase the voltage. The output voltage can be adjusted by the duty cycle of PWM. When the duty cycle is 50%, the output voltage is twice the input voltage. The basic circuit of boost is shown in the figure below:

Step-up and step-down chip circuit

When doing experimental projects, we often encounter situations where there is only one voltage power supply but another voltage power supply is needed, so there is a need for voltage conversion. In addition to the buck-boost circuit, there are also many commonly used chips for everyone to convert the voltage. .

7805 is commonly used when turning 12 to 5v, and 7905 is used when turning -5v. For the circuit, you can directly search the datasheet of the chip to view, or you can see the screenshot below.

7.2v to 5v is also very common, generally use lm2940 directly, the circuit is as follows:

The effect of using lm1117 from 7.2v to 3.3v is quite good, the circuit is as follows:

The circuit diagram of AMS1117 for 5v to 3.3v is as follows:

By the way, I would like to introduce the LM2596.LM2596 series is a 3A current output step-down switch integrated voltage regulator chip produced by Texas Instruments (TI). It contains a fixed frequency oscillator (150KHZ) and a reference regulator (1.23v), and has perfect Protection circuit, current limit, thermal shutdown circuit, etc. The use of this device can form a high-efficiency voltage stabilizing circuit with very few peripheral devices. Provided are: 3.3V, 5V, 12V and adjustable (-ADJ) and other voltage grade products. The relevant circuit can be known by downloading the datasheet directly. The circuit I have used myself is as follows:

Commonly used product applications: ①Mobile phone ②Mobile power supply, PMP player ③Cordless phone ④Radio communication equipment ⑤Sphygmomanometer, medical equipment, key security equipment ⑥Electronic scale, human body scale ⑦Toy⑧Three meters (electric meter, water meter, gas meter )⑨Digital camera, digital photo frame, camcorder⑩Handheld game console, PSP, PS2⑪Computer camera, computer motherboard, PC, MID⑫DVD, portable DVD⑬Mini speaker, Bluetooth speaker, WI-Fi mobile charging bag⑭U disk, electronic cigarette⑮LED flashlight, solar Table lamp, lawn lamp.

Briefly introduce common DC/DC boost ICs, such as:

Model: BT1001

»100KHzVFM switching DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-7V.

»Output voltage range: 2V~5.6V; fixed voltage output.

»Output current: 300mA.

»Built-in switch MOS tube.

»Package: SOT-23-3SOT-89-3TO-92.

Model: BT1002

»200KHzVFM switching DC-DC boost converter.

»Low voltage start: 0.9V start, input voltage 0.9-6V.

»Output voltage range: 2V~5.6V; fixed voltage output.

»Output current: 300mA~750mA.

»Built-in switch MOS tube.

»Package: SOT-23-3SOT-89-3.

Model: BT1003

»180KHzPFM switching DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-7V.

»Output voltage range: 2V~7V; fixed voltage output or adjustable output.

»Output current: 300mA~1000mA.

»There are built-in or external switch MOS tube.

»Package: SOT-23-3SOT-89-3SOT-23-5SOT-89-5.

Model: BT1004

»300KHzPFM switching DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-5V.

»Output voltage range: 2V~5V; fixed voltage output.

»Output current: 300mA~1200mA.

»There are built-in or external switch MOS tube.

»Package: SOT-23-3SOT-89-3SOT-23-5.

Model: BT1034

»300KHzPFM switching DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-5V.

»Output voltage range: 2V~3.6V; fixed voltage output.

»Output current: 300mA.

»Built-in switch MOS tube, built-in Schottky diode.

»Package: SOT-23-3SOT-89-3SOT-23-5.

Model: BT1011

»100KHzPFM switching DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-7V.

»Output voltage range: 2V~7V; fixed voltage output or adjustable output.

»Output current: 300mA~1000mA.

»There are built-in or external switch MOS tube.

»Package: SOT-23-3SOT-89-3SOT-23-5SOT-89-5

Model: BT2011

»1.0MHzPWM switching DC-DC boost converter.

»The input voltage is 2.6-5.5V.

»Adjustable output: 5V1000mA.

»Maximum output current limit function.

»Built-in switch 2AMOS tube.

»Package: SOT-23-6

Model: BT2012

»300KHz switching DC-DC boost converter.

»The input voltage is 2.6-5.5V.

»Low holding voltage: 0.9V, starting voltage 1.2V.

»Fixed output voltage: 5V1500mA.

»External switch MOS tube.

»Package: SOT-23-5.

Model: BT2013

»300KHzPFM/PWM automatic transfer switch type DC-DC boost converter.

»Low voltage start: 0.8V start, input voltage 0.8-6.5V.

»Output voltage range: 1.5V~20V; adjustable output.

»Output current: 300mA~2000mA.

»External switch MOS tube.

»Package: SOT-23-5.

Model: BT2014

»1.2MHz switching DC-DC boost converter.

»Input voltage 2V-24V.

»Output voltage range: “28V; adjustable voltage output.

»Output current: 2000mA.

»Built-in 4A switch MOS tube.

»Package: SOT-23-6.

Model: YD8001

»It has two functions: DC-DC boost converter and lithium battery charging management.

»Lithium battery charging current: 500mA.

»DC-DC output: 5V/1000mA; fixed voltage output.

»External switch MOS tube.

»Package: SOP8L.

Model: YD8002

»Mobile power solution: It has multiple functions such as DC-DC boost converter, lithium battery charging management, power display and so on.

»Lithium battery charging current: 500-700mA.

»DC-DC output: 5V/1000mA or 1500mA; fixed voltage output.

»Four LEDs display power.

»External switch MOS tube.

»Package: SOP8L.

Applications: MP3, digital cameras, Bluetooth headsets, electronic dictionaries, camcorders, PDAs, handheld phones, LED flashlights, LED lights, remote control toys; blood pressure monitors, car alarms, anti-lost devices, wireless mouse keyboards, chargers, etc.