Reliability in start up sequence for D-mode power FET driver
AssigneepSemi Corporation
InventorsArezu Bagheri, Buddhika Abesingha, Ronald E. Reedy
Life of this patent
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Abstract
Methods and devices to address start up of half-bridge circuits including D-mode power FETs are disclosed. The disclosed devices overcome possible issues of output overload or excess current through gate-source of power FETs during start up. Methods and devices based on monitoring coupling capacitors voltages and pre-charging such coupling capacitors using current sources are also described. The current sources can be implemented using negative voltages provided by negative voltage sources such as charge pumps.
Claims18
An electronic circuit configured to receive an input DC voltage, the electronic circuit comprising:
- a high side driver and a low side driver;
- a high side depletion mode field effect transistor (FET) connected to a low side depletion mode FET at a switch node;
- a high side coupling capacitor coupling the high side driver to the high side depletion mode FET, and a low side coupling capacitor coupling the low side driver to the low side depletion mode FET;
- an FET switch configured to couple the input DC voltage to the high side depletion mode FET;
- a bypass capacitor connected to the FET switch and the high side depletion mode FET at one end and to a reference voltage at another end;
- a first transistor connected to the high side depletion mode FET and the high side coupling capacitor at one end and connectable to a first supply voltage at another end;
- and
- a second transistor connected to the low side depletion mode FET and the low side coupling capacitor at one end and connectable to a second supply voltage at another end;
- wherein in a first state:
- the FET switch is in an OFF state, thereby electrically isolating the input DC voltage from the high side depletion mode FET;
- the first transistor is in an ON state, thereby charging the high side coupling capacitor;
- and
- the second transistor is in ON state, thereby charging the low side coupling capacitor.
A method of starting up or restarting a circuit configured to receive an input DC voltage, the circuit comprising:
- a high side depletion mode FET connected to a low side depletion mode FET at a switch node;
- a high side coupling capacitor connected to the high side depletion mode FET at one end and to a high side driver at another end;
- a low side coupling capacitor connected to the low side depletion mode FET at one end and to a low side driver at another end;
- and
- an FET switch connected to the input DC voltage at a first end and to the high side depletion mode FET at a second end,
- the method comprising:
- turning the FET switch off;
- monitoring a DC voltage at the second end;
- based on the monitoring, when the DC voltage at the second end is less than a threshold voltage:
- charging the high side coupling capacitor thereby enabling the high side driver to control the high side depletion mode FET to be in an OFF state;
- and
- charging the low side coupling capacitor thereby enabling the low side driver to control the low side depletion mode FET to be in an OFF state.
Dependencies are inferred from the claim text.