The isolated-flyback power supply controller provides Constant-Voltage (CV) and Constant-Current (CC) output regulation to improve transient response to large load steps. Primary-Side Regulation (PSR) eliminates the need for an Optocoupler.

The Texas Instruments UC3825A family of PWM controllers are improved versions of the standard UC3823 and UC3825 family. Performance enhancements have been made to several of the circuit blocks. Error amplifier gain bandwidth product is 12 MHz, while input offset voltage is 2 mV. Current limit threshold is assured to a tolerance of 5%. Oscillator discharge current is specified at 10 mA for accurate dead time control. Frequency accuracy is improved to 6%. Start-up supply current, typically 100 μA, is ideal for off-line applications. The output drivers are redesigned to actively sink current during UVLO at no expense to the start-up current specification. In addition each output is capable of 2-A peak currents during transitions.

Improved Versions of the UC3823/UC3825 PWMs
Compatible with Voltage-Mode or Current-Mode Control Methods
Practical Operation at Switching Frequencies to 1 MHz
50-ns Propagation Delay to Output
High-Current Dual Totem Pole Outputs (2-A Peak)
Trimmed Oscillator Discharge Current
Low 100-μA Start-up Current
Pulse-by-Pulse Current Limiting Comparator
Latched Overcurrent Comparator With Full Cycle Restart

Flyback Controllers, Texas Instruments

Current-Mode and Voltage-Mode PWM Controller
Primary-Side Regulation
Peak Power Mode
Low Power