Voltage and current triggered switch, and step-down dc-dc converters containing such a switch

A voltage and current triggered switch that turns on when a voltage across the switch reaches a turn-on voltage and that turns off when a current through the switch drops below a holding current, the switch comprising:

• a Zener diode having a breakdown voltage, the Zener diode connected to set the turn-on voltage of the switch to be the breakdown voltage of the Zener diode;
• a positive terminal and a negative terminal;
• a PNP bipolar junction transistor (BJT);
• an NPN BJT;
• a first resistor;
• a second resistor;
• wherein the positive terminal is connected to an emitter of the PNP bipolar junction transistor, and to a first terminal of the first resistor, and a second terminal of the first resistor is connected to a base of the PNP BJT;
• the negative terminal is connected to an emitter of the NPN BJT and to a first terminal of a second resistor, and a second terminal of the second resistor is connected to a base of the NPN BJT;
• a collector of the PNP BJT is connected to the base of the NPN BJT, and a collector of the NPN BJT is connected to the base of the PNP BJT.

A method comprising:

• rectifying AC electricity from a tribo energy harvesting device or a piezo energy harvesting device;
• storing the rectified electricity in a first capacitor;
• once the voltage across the first capacitor has built up to a turn-on voltage set by the breakdown voltage of a Zener diode, closing a V&I triggered switch with turn-on voltage threshold set by Zener diode breakdown voltage (VITSZ) to transfer the energy stored in the first capacitor to an inductor;
• opening the VITSZ, triggered by a current dropping below a threshold current;
• transferring energy from current in the inductor to a voltage across a second capacitor;
• and
• a load consuming the energy stored in the second capacitor.