UC2527AN

UC2527AN Application Field and Working Principle

UC2527AN is a high accuracy monolithic pulse width modulation (PWM) controller from Texas Instruments. It is a member of the UC25xx family of controllers designed for power supplies with high performance on/off line switcher applications. We can categorize it under Power Management Integrated Ciruits (PMIC) - Voltage Regulators - DC DC Switching Controllers.

UC2527AN is used for controlling and regulating the output voltage of a switched mode power supply (SMPS) and to more precisely deliver the desired output voltage. In a typical switching power supply application, UC2527AN controls the switching of the power transistors. It monitors the output voltage and keeps it within the predefined range.

Features

• Low start-up current, less than 14µA
• High accuracy voltage regulation
• 2kV minimum working voltage
• Wide operating temperature range from -40°C to 85°C
• Integrated logic level adjustable pulse generator
• Under-voltage lockout for power up and down
• Programmable slew rate for soft start
• Programmable overshoot prevention

Working Principle

In a normal power supply, the output voltage is controlled by the duty cycle of the switching transistor. This duty cycle is determined by the pulse width modulation (PWM) control system. UC2527AN is based on this principle and maintains a fixed output voltage. The voltage error is sensed by its internal voltage error amplifier and the output voltage is regulated by varying its duty cycle.

The UC2527AN starts by timing an internal RC oscillator. The oscillator then generates pulses that are used to switch power transistors at a fixed frequency. The duty cycle of the pulses determines the effective output voltage of the power transistors. The voltage sense feedback from the external output voltage is compared to a reference voltage and the results of this comparison are used to modulate the duty cycle of the generated pulses.

Thus the output voltage is monitored and maintained within a specified range while still meeting the output power requirements by controlling the duty cycle. The oscillator frequency can be externally programmed by connecting an external resistor. The frequency can thus be set according to the desired frequency of the output.

Applications

• AC/DC converters
• DC/DC converters
• Chargers
• Robotics
• Computers and peripherals
• Automotive
• Power supplies
• Industrial equipments

UC2527AN is a modern switch-mode controller and is used in many applications today. With its wide operating temperature range, high accuracy and low start-up current, it is ideal for many different applications. It also provides protection for overshoot and undervoltage and is programmable for soft start and output frequency.