Power supply controller and semiconductor device
A voltage-dividing circuit 60 , which is formed of serially connected voltage-dividing resistors R 1 , R 2 , R 3 , is disposed between the source terminal S of a power MOSFET 15 and the ground. The divided voltage Va at a connecting point A is applied to one of the input terminals of a comparator 62 , while the divided voltage Vb at a connecting point B is applied to one of the input terminals of a comparator 64 . The other input terminals of the comparators 62, 64 are connected to the connecting line between an external terminal P 4 , to which an external resistor 12 is connected, and an FET 30.
1. A power supply controller disposed between a power source and a load, and configured to control power supply from said power source to said load, said power supply controller comprising:
a semiconductor switching element disposed on a current supply line from said power source to said load;
a current detecting circuit configured to detect a load current passing through said semiconductor switching element;
a voltage generator circuit configured to generate a voltage according to an output-side voltage of said semiconductor switching element; and
an anomaly detecting circuit configured to output an anomaly signal based on a detection signal from said current detecting circuit and a generated voltage of said voltage generator circuit, if a load current passing through said semiconductor switching element exceeds a threshold current corresponding to said generated voltage.
2. A power supply controller as in claim 1 , wherein said voltage generator circuit includes a voltage-dividing circuit configured to divide an output-side voltage of said semiconductor switching element so that a divided voltage is provided as said generated voltage.
3. A power supply controller as in claim 2 ;
wherein said semiconductor switching element is a power FET, and said current detecting circuit includes a sense FET through which a sense current having a predetermined relation to a load current passing through said power FET passes, said power supply controller further comprising:
a current-voltage converter circuit configured to convert a sense current passing through said sense FET to a voltage;
wherein said anomaly detecting circuit is configured to output said anomaly signal if an output voltage of said current-voltage converter circuit exceeds said generated voltage.
4. A power supply controller as in claim 3 , wherein:
said power FET, said sense FET and said anomaly detecting circuit are formed as a semiconductor device configured onto a signal chip or a plurality of chips housed in a package;
said voltage-dividing circuit is included in said semiconductor device; and
said current-voltage converter circuit includes an external resistor disposed outside of said semiconductor device.
5. A power supply controller as in claim 4 , wherein:
said voltage-dividing circuit is configured to generate a plurality of divided voltages; and
said anomaly detecting circuit is configured to output a plurality of anomaly signals depending on a level of an abnormal current by comparing an output voltage of said current-voltage converter circuit to said plurality of divided voltages.
6. A power supply controller as in claim 2 , wherein a bias circuit is provided on an upstream-end side or a downstream-end side of said voltage-dividing circuit.
7. A power supply controller as in claim 6 , wherein said bias circuit includes an FET, in which diode connection is formed, on the downstream-end side of said voltage-dividing circuit, and further includes a bias resistor connected between a gate of said FET and said power source.
8. A power supply controller as in claim 6 , wherein said bias circuit includes a bias resistor connected between said power source and the upstream end of said voltage-dividing circuit.
9. A power supply controller as in claim 7 , wherein a leakage current block circuit is provided on a current path for a current passing to said bias resistor, and configured to normally shut off said current and permit said current to pass when an input signal to said semiconductor switching element is active.
10. A power supply controller as in claim 8 , wherein a leakage current block circuit is provided on a current path for a current passing to said bias resistor, and configured to normally shut off said current and permit said current to pass when an input signal to said semiconductor switching element is active.
11. A semiconductor device configured to control power supply using a power FET, wherein:
said power FET, a sense FET through which a sense current corresponding to a current amount of said power FET passes, an anomaly detecting circuit configured to detect an anomaly of a current passing through said power FET based on a level of said sense current, and a voltage-dividing circuit configured to divide a source voltage of said power FET are provided as a single chip or a plurality of chips housed in a package;
an external terminal, to which a current path of said sense current is connected and an external resistor is externally connectable, is provided, and said sense current passes to said external resistor through said external terminal; and
said anomaly detecting circuit is configured to output an anomaly signal based on comparison of a terminal voltage of said external resistor with a divided voltage from said voltage-dividing circuit.