In described examples, a system regulates provision of DC-DC electrical power. The system includes a DC-DC converter, an input voltage node to receive an input voltage, a current source, a voltage source node, and a ground switch. The DC-DC converter includes a flying capacitor and multiple converter switches. The current source is coupled between the input voltage node and a top plate of the flying capacitor, to provide current to the top plate when the current source is activated by an activation voltage. The voltage source node is coupled to the input voltage node and to the current source, to provide the activation voltage to the current source, such that the activation voltage is not higher than a selected voltage between: a breakdown voltage of the converter switches; and a maximum value of the input voltage minus the breakdown voltage. The ground switch is coupled between a bottom plate of the flying capacitor and a ground.