US 12,088,287 B1
Low-current run plug enhanced safety circuit for underwater systems
Dwane F. Sample, Spokane, WA (US)
Assigned to United States of America as represented by the Secretary of the Navy, Washington, DC (US)
Filed by United States of America as represented by the Secretary of the Navy, San Diego, CA (US)
Filed on Apr. 20, 2023, as Appl. No. 18/303,771.
Int. Cl. H03K 17/687 (2006.01); H03K 17/06 (2006.01); H03K 17/0812 (2006.01)
CPC H03K 17/687 (2013.01) [H03K 17/063 (2013.01); H03K 17/08122 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A low-current run plug circuit comprising:
1st and 2nd terminals configured to pass through an external wall of a battery-powered apparatus;
a run plug configured to electrically connect the 1st and 2nd terminals on an exterior side of the external wall when the run plug is installed, wherein when the run plug is removed no current flows between the 1st and 2nd terminals;
a safety circuit mounted within the battery-powered apparatus comprising:
a junction field effect transistor (JFET) having a gate terminal (G1), a drain terminal (D1), and a source terminal (S1), wherein D1 is configured to be electrically connected to a cathode of the apparatus' battery;
a current set resistor (RA) electrically connected between the 1st terminal and S1, wherein G1 is electrically connected between the 1st terminal and RA such that a current IA flowing to the 1st terminal is set by a transfer function of the JFET and RA;
a P-channel enhancement mode metal oxide silicon field effect transistor (MOSFET) having a gate terminal (G2), a drain terminal (D2), and a source terminal (S2), wherein D2 is configured to be electrically connected to an electrical load within the apparatus;
a voltage divider having an input (Vin), an output (Vout), and a ground terminal (GR1), wherein Vin is electrically connected to S2 and D1, and wherein Vout is electrically connected to G2; and
an N-channel MOSFET having a gate terminal (G3), a drain terminal (D3), and a source terminal (S3), wherein D3 is electrically connected to GR1, G3 is electrically connected to the 2nd terminal, and S3 is electrically connected to a ground such that when the run plug is removed the N-channel MOSFET and the P-channel MOSFET are in cutoff wherein no current flows to the electrical load, and such that when the run plug is installed, the safety circuit creates a low-impedance electrical path from the cathode to the electrical load.