Current switching sensor detector
View Patent ↗A sensor for a switching circuit detects the logical state of the switching circuit by monitoring the current flow through the switching circuit. The current flow is conditioned by one or more current limiters and a voltage regulator, coupled in series with the switching circuit. The sensor also includes a current limit control circuit coupled to each of the current limiters. The sensor is effectively shielded from the effect of parasitic capacitance in the switching device because the current flow through the switching circuit reacts immediately and without regard to the level of parasitic capacitance whenever the switching circuit makes a state change.
1. A circuit for detecting a state of a controllable element, comprising:
a current sensing amplifier for producing a first current;
a first current limiter, coupled to said current sensing amplifier, for limiting a current level of a current flowing through said first current limiter to be no greater than a first parameter; and
a voltage regulator, coupled to said first current limiter, for controlling a voltage at an output node of said voltage regulator to be at a second parameter;
wherein
said first current flows in series through said first current limiter, said voltage regulator, and said controllable element,
said current sensing amplifier senses a current level of said first current and produces an output signal as a function of said current level,
said output signal also being indicative of a state of said controllable element.
2. The circuit of claim 1 , wherein said controllable element is a switching circuit.
3. The circuit of claim 1 , further comprising:
a second current limiter, coupled to said controllable element, for limiting a current level of a current flowing through said second current limiter to be no greater than a third parameter;
wherein said first current also flows in series through said second current limiter.
4. The circuit of claim 3 , wherein said first current flows from said first current limiter to said controllable element, and from said controllable element to said second current limiter.
5. The circuit of claim 1 , further comprising:
a control circuit, coupled to said current sensing amplifier, for controlling a level of said first parameter.
6. The circuit of claim 5 , wherein said control circuit is also coupled to said voltage regulator and controls a level of said second parameter.
7. The circuit of claim 5 , further comprising:
a second current limiter, coupled to said controllable element, for limiting a current level of a current flowing through said second current limiter to be no greater than a third parameter;
wherein said first current also flows in series through said second current limiter and said control circuit also controls a level of said third parameter.
8. The circuit of claim 7 , wherein said control circuit is also coupled to said voltage regulator and controls a level of said second parameter.
9. The circuit of claim 8 , wherein said control circuit maintains a same level for said first and third parameters.
10. The circuit of claim 1 , wherein said current sensing amplifier comprises:
an input node for receiving an input power;
a current mirror having an input coupled to said input node, a first output for generating said first current, and a second output for generating a second current; and
a output circuit, said output circuit producing said output signal from said second current.