UC2843N

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UC2843N Application Field and Working Principle

UC2843N is a pulse width modulated (PWM) voltage controller from Texas Instruments, which belongs to the PMIC – Voltage Regulators – DC DC Switching Controllers family. It is mainly used to regulate the output voltage level by precisely controlling the switching frequency and duty cycle. The output voltage level can be adjusted based on the reference voltage and current limit. It has the capability to reduce electromagnetic interference (EMI) and to achieve high accuracy via synchronous rectification (if needed).

Features

Some of the key features of the UC2843N PWM voltage controller include:

• High-performance control loop architecture with on-chip regulator
• On-chip feedback divider
• Architecture is expandable to support current-mode regulation
• Operates from 10V to 50V with 600kHz - 1.0MHz switching frequency
• Internal soft-start
• Flexible oscillator with external synchronization
• Hiccup-mode output over-current protection
• Circuit is monolithic and highly integrated

Applications of UC2843N

The UC2843N PWM voltage controller is extensively used in a variety of applications such as consumer, automotive, industrial, or medical due to its advantages in terms of performance. These applications include personal computer, external storage and hard drive, personal video recorder, AA, AAA, C & D battery chargers, android TV box, DC-DC converters, Power over Ethernet (PoE) converter, and li-ion battery chargers. It is also used in LED lighting control and in automotive applications such as voltage and current regulation, lighting control, and transmission control.

Working Principle of UC2843N

The UC2843N PWM voltage controller is an on-chip voltage-mode control loop based off the required input and output voltage. Voltage-mode control is a compensation concept that uses a sensed output voltage for regulating the average output current. This regulation concept implements an embedded error amplifier, an internal current limit and the external opto-isolator coupled darlington power transistor.

At the input side, the UC2843N provides a means of setting the switching frequency by connecting an external resistor. This can be used to either strictly determine the frequency or to be adjustable by a voltage input, allowing dynamic frequency control based on the input voltage or other conditions. For the output stage, the UC2843N requires, at least, an external opto-isolator, a darlington power transistor, a free-wheeling diode and a few components (resistors, capacitors) to achieve the desired output characteristics.

The working principle of the UC2843N uses the voltage-mode control loop. The input voltage and the feedback voltage from the output (also known as the error amplifier voltage) are compared with each other to generate the internal clock pulse. The pulse is then shaped and used to trigger the power output stage, in turn controlling the output voltage. High voltage levels turn off the power output and low levels cause it to turn on, thus regulating the output voltage.

Conclusion

UC2843N is a versatile pulse width modulated (PWM) voltage controller from Texas Instruments that belongs to the PMIC – Voltage Regulators – DC DC Switching Controllers family. It has several applications such as in personal computers, LED lighting control and automotive control. Its voltage-mode control loop works by comparing the input voltage level with the feedback voltage from the output and generating an internal clock pulse to control the output voltage. The UC2843N voltage controller is a cost-effective solution that can provide efficient and accurate control over the output voltage.

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