This paper introduces a high power density step-up converter for LED applications, based on a hybrid serial-output (HSO) architecture [1], which is suitable for on-chip implementation. In this system, the output voltage is formed by stacking the output of a switched-capacitor (SC) converter on top of a boost converter output. The high power density SC converter processes around a half of the power of the system and is left unregulated. The boost converter processes the remainder of the power and regulates the output voltage. In comparison with conventional boost-based solutions, the introduced boost-SC HSO drastically reduces the passive component volume and decreases peak voltage stress of switches. Experimental results obtained with a 3.7 V to 13 V, 2.6 W, 1080 kHz prototype show that the introduced SC-boost HSO converter has about three times smaller reactive component area than a conventional boost having the same power processing efficiency.