1. A switched-mode power supply (SMPS), comprising:a direct current (DC)-to-DC step-down converter having an input terminal, a positive output terminal, a negative output terminal, and a transistor having a channel being coupled between a cathode and an anode, the anode being coupled with a grounded current sense resistor, and the DC-to-DC step-down converter being: configured for operation in a boundary conduction mode; and configured for receiving a DC input current having an input voltage at the input terminal; and configured for causing a DC output current having an output voltage to flow from the positive output terminal through an output load to the negative output terminal; and configured for being integrated with a controller, the controller being configured for applying a pulse-width-modulated voltage to the channel of the transistor for controlling a duty cycle of the DC output current, the duty cycle having an on-time period (T-On) and an off-time period (T-Off), the controller being coupled with a T-On capacitor having a T-On voltage, the controller being configured for charging the T-On capacitor during the T-On period by a regulated T-On current for setting a maximum limit of the T-On period, the controller being configured for initiating the T-Off period when the T-On capacitor becomes charged to a selected maximum limit of the T-On voltage;
a voltage divider being coupled with the input terminal for receiving the input voltage and for reducing the input voltage to a signal voltage being within a selected voltage signal range;
a voltage-to-current converter having a connection with the voltage divider, the voltage-to-current converter including another output terminal being coupled with another transistor having another channel being coupled between another cathode and another anode, the voltage-to-current converter including a grounded precision resistor configured for generating a transconductance voltage, the voltage-to-current converter being configured for inputting the signal voltage and for outputting an error correction voltage being applied to the another channel for generating a signal current appearing at the another anode and defining a transconductance of the voltage-to-current converter and having a current signal value being within a selected current signal range representing the selected voltage signal range; and
a current mirror being coupled with the another cathode and being configured for receiving and combining a regulated supply current having a supply voltage together with the signal current as forming a T-On modulation current, with the current mirror being configured for causing the T-On modulation current to be combined with the regulated T-On current to charge the T-On capacitor.