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US 7,605,598 B2Granted
Undercurrent sense arrangement and method
AssigneeNXP B.V.
InventorBrendan P. Kelly
Life of this patent
Estimating the term…
Abstract
An on-state low current detector uses a transistor with main (32) and sense (34) cells. Feedback circuit (36) acts to keep the voltage across main cells (32) at a substantially constant target value when the load current falls below a level that generates the target voltage value in the main cells. The target voltage value is sufficiently high to ensure that the voltages of low current detection comparator (18) are readily measurable.
Claims14
A power semiconductor device, comprising:
- an output transistor having
- main cells and sense cells,
- a control input connected to the main and sense cells, and
- main and sense cell controlled outputs;
- an output terminal connected to one of the main cell controlled outputs for connection to a load;
- a feedback circuit for measuring the voltage across the main cell controlled outputs of the output transistor and for controlling the voltage on the control input, the feedback circuit including a first comparator configured to output a signal responsive to the magnitude of the voltage across the main cell controlled outputs and a diode connected in series between the output of the first comparator and the control input, the diode orientated to pass current between the output of the first comparator and the control input to increase the voltage across the main cell controlled outputs;
- a reference current supply feeding a reference current through the sense cell controlled outputs;
- and
- a second comparator arranged to compare the voltages across the main cell controlled outputs and the sense cell outputs and to output a low-current signal when the magnitude of the voltage across the main cell controlled outputs falls below that across the sense cell outputs.
6 more elements
A method of operating a semiconductor device, the device including an output transistor circuit having main cells and sense cells, a control input connected to the main and sense cells, and main and sense cell controlled outputs, the method comprising:
- driving the main and the sense cells in common;
- driving a load from one of the main cell controlled outputs feeding a reference current through the sense cell controlled outputs;
- measuring the voltage across the main cell controlled outputs and controlling the voltage on the control input to increase the voltage across the main cell controlled outputs responsive to the magnitude of the voltage across the main cell controlled outputs falling below a predetermined value;
- outputting a signal using a comparator responsive to the magnitude of the voltage across the main cell controlled outputs;
- passing current between the output of the comparator and the control input to increase the voltage across the main cell controlled out, the current being passed through a diode that is connected in series between the output of the comparator and the control input;
- and
- comparing the voltages across the main cell controlled outputs and the sense cell controlled outputs and outputting a low-current signal when the magnitude of the voltage across the main cell controlled outputs falls below that across the sense cell controlled outputs.
4 more elements
A device comprising:
- an output transistor circuit having main cells and sense cells;
- a control input connected to the main and sense cells;
- main and sense cell controlled outputs;
- a first circuit configured and arranged to drive the main and the sense cells in common;
- a second circuit configured and arranged to drive a load from one of the main cell controlled outputs feeding a reference current through the sense cell controlled outputs;
- a measurement circuit configured and arranged to measure the voltage across the main cell controlled outputs and to control the voltage on the control input, the measurement circuit including a comparator configured to output a signal responsive to the magnitude of the voltage across the main cell controlled and a diode connected in series between the output of the comparator and the control input, the diode orientated to pass current between the output of the comparator and the control input to increase the voltage across the main cell controlled outputs;
- and
- a comparison circuit configured and arranged to compare the voltages across the main cell controlled outputs and the sense cell controlled outputs and to output a low-current signal when the magnitude of the voltage across the main cell controlled outputs falls below that across the sense cell controlled outputs.
5 more elements
Dependencies are inferred from the claim text.