(57) A current measuring circuit (100; 200; 300) for providing a current flow signal indicative
of current flow between a first terminal (102; 202; 302) and second terminal (104;
204; 304), comprising:
a main transistor (106, 206) having a main drain, a main source (105; 205) and a main
gate (109; 209), wherein the main source (105; 205) and the main drain (106; 206)
define a main source-drain path, the main drain is connected to the first terminal
(102; 202; 302), the main source is connected to the second terminal (104; 204; 304)
and the main gate is connected to a first control terminal (109; 209);
a sense transistor having a sense drain, a sense source (107; 207) and a sense gate,
wherein the sense source and the sense drain define a sense source-drain path, the
sense drain is connected to the first terminal (102; 202; 302) and the sense gate
is connected to the first control terminal (109; 209);
a bypass switch (108; 208; 308) having:
a controllable conduction path connected in parallel with the sense drain-source path
of the main transistor between the first and second terminals (102; 202; 302, 104;
204; 304); and
a second control terminal (111; 211) for enabling or preventing a current flow through
the controllable conduction path;
an output amplifier (110; 210; 310) having:
an input connected to both the sense source of the sense transistor and the controllable
conduction path of the bypass switch; and
an output for providing the current flow signal; and
a controller (118; 218; 318) configured to set, in accordance with the current flow
signal, a first control signal for the first control terminal (109; 209) and a second
control signal for the second control terminal (111; 211) in order to enable current
flow through:
each of the respective drain-source paths of the main and sense transistors; or
the controllable conduction path of the bypass switch (108; 208; 308).
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