E-UC3844BN

E-UC3844BN is an off-line switcher pulse width modulation (PWM) controller, designed for and capable of operating in all types of switched-mode power supply circuits including boost, buck and flyback. Operating from an input of 12 V over a voltage range of 3 V to 70 V, this system provides up to a 500 V output, drawing up to 4 A under peak load conditions with a frequency of up to 500 kHz. It offers excellent transient response and improved line and load regulation. The E-UC3844BN also incorporates useful features such as cycle-by-cycle current-limit protection, programmable switching frequency and soft start.

Application Field

The E-UC3844BN is widely used in HVAC systems, battery chargers, Uninterruptible Power Supplies (UPSs), printer power supplies, small motor control applications and portable or handheld electronic devices such as MP3 players, personal digital assistants (PDAs) and cellular telephones. Its high efficiency and low noise performance, combined with the on-chip protection features and available integrated current sensing, make it an excellent choice for portable and handheld devices where low power consumption and audio noise are critical, as well as for many other DC-DC converter applications.

Working Principle

The E-UC3844BN PWM controller implements an oscillator with selectable switching frequencies, current-limit, remote shutdown and a self-startup with soft-start mode. Its internal circuits provide the capability of time, interval and cycle-by-cycle current-limit control of the output, as well as lead-lag and dead-time control of the output signal. The signal is converted to a 20kHz pulse-width modulated (PWM) signal. The signal is then compared to an internal reference and the result is used to generate the output signal. The frequency of the output signal can be set manually by an external resistor.

The output of the E-UC3844BN controller is a pulse-width modulated signal. This signal is used to control the switching speed of a power switch, typically a power MOSFET or IGBT, that is connected to the output of the system. The power switch is typically in conduction for a predetermined amount of time and during that period passes current through to the output. The frequency of the output signal is regulated by an output capacitor, connected between the output and ground, that is charged during the pulse-on period and discharged during the off period.

The E-UC3844BN controller incorporates a number of useful features such as programmable operating frequency, cycle-by-cycle current-limit control, remote shutdown and a self-startup with soft-start mode. It also features a thermal shutdown feature that will turn off the power switch if the temperature exceeds a safe operating limit. This feature is designed to prevent the system from overheating and further protects against current and voltage overload conditions.

Overall, the E-UC3844BN is a highly reliable, efficient and cost-effective PWM controller that is suitable for a wide range of applications such as HVAC systems, battery chargers, Uninterrupted Power Supplies (UPSs), printer power supplies, small motor control applications and portable or handheld electronic devices such as MP3 players, PDAs and cellular telephones.