Voltage regulator
View Patent ↗Provided is a voltage regulator capable of setting an accurate short-circuit current. Used as a circuit for determining a current value of a short-circuit current of an overcurrent protection circuit is not a resistor for converting current into voltage but a circuit for controlling in the form of current, that is, a circuit of an N-channel depletion type transistor including a gate and a drain that are connected to each other and operating in a non-saturated state. The N-channel depletion type transistor has process fluctuations that are linked with those of a detection transistor, and hence an accurate short-circuit current may be set without trimming.
1. A voltage regulator, comprising:
an error amplifier circuit for amplifying and outputting a difference between a divided voltage determined by dividing an output voltage of an output transistor, and a reference voltage, to control a gate of the output transistor; and
an overcurrent protection circuit for detecting an overcurrent flowing into the output transistor to limit a current of the output transistor,
wherein the overcurrent protection circuit comprises:
a sense transistor controlled by an output voltage of the error amplifier circuit, for sensing an output current of the output transistor;
a first transistor comprising an N-channel depletion type transistor or an N-channel enhancement type transistor having a gate connected to a drain thereof and that operates in a non-saturated region, for generating a voltage based on a current flowing through the sense transistor; and
an output current limiting circuit controlled by the voltage generated by the first transistor, for limiting a gate voltage of the output transistor.
2. A voltage regulator according to claim 1 , wherein the N-channel depletion type transistor comprises:
a plurality of N-channel depletion type transistors connected in series; and
a fuse for trimming connected in parallel to each of the plurality of N-channel depletion type transistors.
3. A voltage regulator, comprising:
an error amplifier circuit for amplifying and outputting a difference between a divided voltage determined by dividing an output voltage of an output transistor, and a reference voltage, to control a gate of the output transistor; and
an overcurrent protection circuit for detecting an overcurrent flowing into the output transistor to limit a current of the output transistor,
wherein the overcurrent protection circuit comprises:
a sense transistor controlled by an output voltage of the error amplifier circuit, for sensing an output current of the output transistor;
a first transistor that operates in a non-saturated region, for generating a voltage based on a current flowing through the sense transistor, wherein a source of the sense transistor is connected to a drain of the first transistor; and
an output current limiting circuit controlled by the voltage generated by the first transistor, for limiting a gate voltage of the output transistor.
4. A voltage regulator according to claim 1 ,
wherein the voltage regulator further comprises a resistor connected to a source of the N-channel enhancement type transistor.
5. A voltage regulator according to claim 1 ,
wherein the voltage regulator further comprises a second N-channel depletion type transistor connected to a source of the N-channel enhancement type transistor, the second N-channel depletion type transistor including a gate and a drain that are connected to each other.
6. A voltage regulator according to claim 1 ,
wherein the output current limiting circuit comprises a second transistor for detecting the voltage generated by the first transistor, and
wherein the second transistor comprises an initial transistor.
7. A voltage regulator according to claim 6 ,
wherein the output current limiting circuit further comprises a third transistor connected to a drain of the second transistor, and
wherein the third transistor comprises a P-channel transistor including a gate connected to a drain of the P-channel transistor.
8. A voltage regulator according to claim 3 , wherein the first transistor comprises an N-channel enhancement type transistor including a gate connected to a constant voltage circuit.