Granted Patent B2

US 8,179,107 · App. 12/354,559 · Granted May 15, 2012

Abstract

Claims (26)

1. A power supply circuit comprising:

a voltage generating circuit configured to generate an output voltage of a target level from an input voltage;

an overcurrent protection circuit configured to control the voltage generating circuit so as to stop an output current, when a level of the output current generated at a time of generating the output voltage is greater than a reference level; and

a reference-level change circuit configured to change the reference level in the overcurrent protection circuit to be at a second level higher than a first level from the first level for a predetermined period, when the overcurrent protection circuit detects that the level of the output current is greater than the reference level.

2. The power supply circuit according to claim 1 , wherein the overcurrent protection circuit includes:

a comparison circuit configured to output a comparison result between a voltage according to the output current and a reference voltage according to the reference level; and

a generation control circuit configured to control the voltage generating circuit so as to stop the output current when the level of the output current is greater than the reference level based on the comparison result, and wherein

the reference-level change circuit changes the reference voltage in the comparison circuit to be at a second reference voltage according to the second level from a first reference voltage according to the first level for the predetermined period, when the level of the output current is detected being greater than the reference level based on the comparison result.

3. The power supply circuit according to claim 2 , wherein the reference-level change circuit includes:

a timer circuit configured to detect that the predetermined period has elapsed after the level of the output current has become greater than the reference level based on the comparison result; and

a reference-voltage control circuit configured to set the reference voltage in the comparison circuit at the first reference voltage until a time when the level of the output current is detected being greater than the reference level based on the comparison result, to set the reference voltage in the comparison circuit at the second reference voltage when the level of the output current is detected being greater than the reference level, and to set the reference voltage in the comparison circuit at the first reference voltage when the timer circuit detects that the predetermined period has elapsed.

4. The power supply circuit according to claim 1 , wherein the overcurrent protection circuit includes:

a current detection circuit configured to output a detection voltage according to the output current;

a comparison circuit configured to output a comparison result between the detection voltage and a reference voltage according to the reference level; and

a generation control circuit configured to control the voltage generating circuit so as to stop the output current when the level of the output current is greater than the reference level based on the comparison result, and wherein

when the level of the output current is detected being greater than the reference level based on the comparison result, the reference-level change circuit controls the current detection circuit so as to change the reference level at a time when the level of the output current is greater than the reference level, to be at the second level from the first level for a predetermined period.

5. The power supply circuit according to claim 4 , wherein the reference-level change circuit includes:

a timer circuit configured to detect that the predetermined period has elapsed after the level of the output current has become greater than the reference level based on the comparison result; and

a detected-voltage control circuit configured

to control the current detection circuit so that the level of the output current is detected being greater than the reference level when the level of the output current is greater than the first level, until a time when the level of the output current is detected being greater than the reference level based on the comparison result,

to control the current detection circuit so that the level of the output current is detected being greater than the reference level when the level of the output current is greater than the second level, when the level of the output current is detected being greater than the reference level, and

to control the current detection circuit so that the level of the output current is detected being greater than the reference level when the level of the output current is greater than the first level, when the timer circuit detects that the predetermined period has elapsed.

6. Electronic equipment, comprising:

a voltage generating circuit configured to generate an output voltage of a target level from an input voltage;

an overcurrent protection circuit configured to control the voltage generating circuit so as to stop an output current, when a level of the output current to be output at a time of generating the output voltage is greater than a reference level; and

a reference-level change circuit configured to change the reference level in the overcurrent protection circuit to be at a second level higher than the first level from the first level for a predetermined period, when the overcurrent protection circuit detects that the level of the output current is greater than the reference level.

Assignments (8)