Normally-open solenoid valves and mass flow controllers having normally-open solenoid valves

A mass flow controller, comprising:

• a flow sensor configured to sense a mass flow of gas through a flow path;
• and
• a normally-open, proportional flow controller configured to control flow of the gas through the flow path, the flow controller comprising:
• a body comprising an inlet, an outlet, and an interior volume;
• a poppet configured to move within the interior volume between a seated position in which the poppet blocks gas flow between the inlet and the outlet, a fully opened position in which gas is permitted to flow between the inlet and the outlet, and positions between the seated position and the fully opened position;
• a biasing element configured to bias the poppet toward the seated position;
• a solenoid having a coil and a core;
• a permanent magnet positioned to bias the poppet away from the seated position;
• and
• control circuitry configured to selectively control the solenoid to control a net force of the permanent magnet and the solenoid on the poppet to control a position of the poppet.