In this work, we describe a new approach for compact and energy-efficient cooling of converters where multiple miniaturized microfluidic cold-plates are attached to transistors providing local heat extraction. The high pressure drop associated with microchannels was minimized by connecting these cold-plates in parallel using a compact 3D-printed flow distribution manifold. We present the modeling, design, fabrication and experimental evaluation of this microfluidic cooling system and provide a design strategy for achieving energy-efficient cooling with minimized pumping power. An integrated cooling system is experimentally demonstrated on a 2.5 kW switched capacitor DC-DC converter, cooling down 20 GaN transistors. A thermal resistance of 0.2 K/W was measured at a flow rate of 1.2 ml/s and a pressure drop of 600 mbar, enabling the cooling of a total of 300 W of losses in the converter using only 75 mW of pumping power, which can be realized with small micropumps. Experimental results show a 10-fold increase in power density compared to conventional cooling, potentially up to 30 kW/l. This proposed cooling approach offers a new way of co-engineering the cooling and the electronics together to achieve more compact and efficient power converters.