An input stage circuit of a three-level DCDC converter is provided. The multiphase switching regulator is operated by switching the first phase at a higher switching frequency than the second phase via pulse width modulation signals provided to the phases. The present invention connects an adapting cable to a lateral side of the connector to achieve an easy installation and effectively avoid using excessive cable materials or having a poor cable management. Also, the knotter assembly includes a primary body supporting a rotatable, slotted knotter pinion.