UC2842 PDF

Справочник радиолюбителя Микросхемы ШИМ-контроллера KA, UC, UC Микросхемы ШИМ-контроллера ka или UC uc является самой распространенной при построении блоков питания для бытовой и компьютерной техники, часто используется для управления ключевым транзистором в импульсных блоках питания. Рассмотрим структурную схему микросхем и серий: На 7 вывод микросхемы подается напряжение питания в диапазоне от 16 Вольт до Микросхема имеет встроенный триггер Шмидта UVLO , который включает микросхему, если напряжение питания превышает 16 Вольт, и выключает если напряжение питания по каким-либо причинам станет ниже 10 Вольт. Микросхемы и серий также обладает защитой от перенапряжения: если напряжение питания превысит 34 Вольта, микросхема отключится. Для стабилизации частоты генерации импульсов микросхема имеет внутри свой собственный 5 вольтовый стабилизатор напряжения выход которого подключен к выводу 8 микросхемы.

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An output pin responsible for external loop compensation. This input provides through a resistor divider connected to a switching power supply. Current sensing is used to check the current in the circuit. The output voltage across current sensing resistor provides to this input.

Totem pole configuration provides a high current sink and source ability. It has short circuit protection and can provide 20 mA in excess for powering additional control system circuitry. The operating voltage range is 12V to 28V.

It has an amplifier. Therefore, you can use this IC in designing isolated and non-isolated power supply. If you require a wide temperature range in any project or application, then you can use this IC. How to use it? SOIC package has separate power and ground pins. The simplified block diagram is shown below. Pin numbers shown in parenthesis are for the SOIC package. Modes of Operation This IC can be used in two modes which are peak current or voltage control.

Vref is provided for charging timing capacitors through a timing resistor by providing charging current. The reference voltage should be grounded with a ceramic capacitor. The minimum value of this capacitor should be 0. It is very important for reference stability therefore it should be connected as close to the pin as possible.

The Voltage feedback is responsible for controlling a PWM signal based on the feedback. The change in current through the circuit monitored by shunt resistance. The voltage difference across this resistor is provided to the feedback pin.

VFB lead length and stray capacitance should be kept as small as possible for acquiring the best stability. How to set Frequency? We can a network of a resistor and a capacitor across this pin. The values of Rt and Ct define the frequency of an oscillator.

This mathematical relation defines relationship between timing capacitor, timing resistor, and frequency. But the maximum operating frequency of UC is 50KHz.

Simple test Circuit This is a circuit diagram of a test circuit. We use it to test IC outputs and internal circuits. Two potentiometers adjust the time period of PWM. Just play with these two variable resistors. After that, we will get different duty cycle PWM at the output pin.


UC2842 Current PWM Controller IC



Микросхемы ШИМ-контроллера KA3842, UC3842, UC2842


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