The TLS1242 and TLS1244 are designed as optimal high-power-factor switching power supply systems with minimum external components. The current-mode PWM controller and the fixed-frequency average-current power-factor corrector (PFC) of each device are combined into a 20-pin DIP package. Internally implemented circuits include: undervoltage lockout (UVLO), featuring a low start-up current; a precision reference that can be trimmed for accuracy at the error amplifier input; a multiplier; two PWM comparators; overvoltage protection (OVP); and two totem-pole output stages designed to source or sink current. The output stage is suitable for driving n-channel MOSFETs, and is low when in the off state. The fixed-frequency average-current-mode power-factor-correction controller circuit is synchronized with a current-mode PWM controller internally. Fixed-frequency power-factor correction helps prevent problems in frequency-sensitive applications such as video monitor, telecom, RF transmitters, and medical imaging. The synchronization of the PFC with the PWM controller helps reduce EMI problems as well. The pin assignment of both the TLS1242 and the TLS1244 is intended to accommodate the UC3842/3844 as well, if PFC is not required in the application. The upper pins (1, 2, 3, 4, 17, 18, 19 and 20) have the same pin assignment as the UC3842, making the current-mode SPS application more flexible. The PWM portion of the TLS1242 can operate to duty cycle approaching 100%. A duty cycle range of 0 to 50% is obtained using the TLS1244. The TLS1242 and TLS1244 are characterized for operation from 0C to 70C.