Dropper-type regulator
AssigneeOki Semiconductor Co., Ltd.
InventorsNorihiro KAWAGISHI, Kazuyoshi Asakawa
Life of this patent
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Abstract
A dropper-type regulator capable of providing a soft start function using a simple circuit configuration. An exemplary regulator includes a first FET having a relatively high current driving capability and a second FET having a relatively low current driving capability are provided in parallel between an input terminal and an output terminal. For a predetermined time immediately after power activation, only the second FET is driven, thereby preventing a large rush current. A switch circuit connected to the gate of the first FET is operated after the predetermined period of time, thereby supplying a driving voltage to the gate of the first FET.
Claims20
A regulator comprising:
- a first transistor including a first source connected to a first input terminal and a first drain connected to a first output terminal;
- a second transistor including a second source connected to the first source and a second drain connected to the first drain, the second transistor having a current driving capability lower than a current driving capability of the first transistor;
- a driving voltage generation circuit configured to generate a first driving voltage corresponding to a first output voltage appearing at the first output terminal, the first driving voltage being supplied to a gate of the second transistor;
- and
- a switch device configured to selectively supply the first driving voltage to a gate of the first transistor.
A power supply system comprising:
- a dropper-type regulator including
- a first transistor including a first source connected to a first input terminal and a first drain connected to a first output terminal,
- a second transistor including a second source connected to the first source and a second drain connected to the first drain, the second transistor having a current driving capability lower than a current driving capability of the first transistor,
- a driving voltage generation circuit configured to generate a first driving voltage corresponding to a first output voltage appearing at the first output terminal, the first driving voltage being supplied to a gate of the second transistor, and
- a switch device configured to supply the first driving voltage to a gate of the first transistor after a first predetermined period of time has elapsed after activation of the regulator, the switch device including
- an activation control circuit configured to generate an activation control voltage that varies over time after activation of the regulator,
- a first comparator configured to supply a first comparator output at a first voltage when the activation control voltage is less than a first predetermined threshold and at a second voltage when the activation control voltage is greater than the first predetermined threshold, and
- a switch circuit operatively connected to the first comparator and configured to receive the comparator output, the switch circuit being configured to selectively connect the gate of the first transistor to the first driving voltage based upon receipt of one of the first voltage and the second voltage;
- and
- a switching regulator including
- a series circuit including an inductor connected together in series with a diode at a connection point, the series circuit being connected a second input terminal and a second output terminal,
- a third transistor connected to the connection point, and
- a driving circuit configured to supply a driving voltage to a gate of the third transistor,
- wherein the driving circuit is configured to generate the driving voltage with a duty ratio corresponding to the activation control voltage.
Dependencies are inferred from the claim text.