The HA17384S/H and HA17385H are PWM control switching regulator IC series suitable for highspeed, current-mode switching power supplies. With ICs from this series and a few external parts, a small, low cost flyback-transformer switching power supply can be constructed, which facilitates good line regulation by current mode control. Synchronous operation driven after an external signal can also be easily obtained which offers various applications such as a power supply for monitors small multi-output power supply. The IC series are composed of circuits required for a switching regulator IC. That is a under-voltage lockout (UVL), a high precision reference voltage regulator (5.0 V 2%), a triangular wave oscillator for timing generation, a high-gain error amplifier, and as totem pole output driver circuit which directly drives the gate of power MOSFETs found in main switching devices. In addition, a pulse-by-pulse type, highspeed, current-detection comparator circuit with variable detection level is incorporated which is required for current mode control.