Switching regulator and electronic device

• US 9,270,162 B2
• Filed: 03/03/2014
• Issued: 02/23/2016
• Est. Priority Date: 03/04/2013
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Deguchi, Michiyasu, Kawano, Akihiro
• Primary Examiner(s): Patel, Dharti
• Application Number:
  US14/195,274
• Publication Number:
  US 20140247523A1
• Time in Patent Office: 722 Days
• Field of Search: 361/93.1
• US Class Current: 1/1
• CPC Class Codes: H02H 9/02 responsive to excess current current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

There is provided a switching regulator including an overcurrent protection circuit which is able to automatically return from an overcurrent state. The switching regulator includes an error amplification circuit which amplifies a difference between a feedback voltage and a reference voltage based on an output voltage and outputs the amplified difference; a PWM comparator which compares an output of the error amplification circuit with an output of a triangular wave oscillation circuit, and controls an output transistor; an overcurrent detection circuit which monitors a load current flowing through a load connected to an output terminal, detects that the load current is an overcurrent, and outputs an overcurrent detection signal causing a switching operation to stop; and a negative feedback control circuit which receives the overcurrent detection signal, and controls the load current to a predetermined current value.

Claims

1. A switching regulator comprising:

an error amplification circuit which amplifies a difference between a feedback voltage and a reference voltage based on an output voltage and outputs the amplified difference;

a PWM comparator which compares an output of the error amplification circuit with an output of a triangular wave oscillation circuit, and controls an output transistor;

an overcurrent detection circuit monitors a load current flowing through a load connected to an output terminal via a sense resistor through which the load current flows, detects an overcurrent generated from the load current, and outputs an overcurrent detection signal causing a switching operation to stop; and

a negative feedback control circuit which receives the overcurrent detection signal, and, while the overcurrent condition is detected, controls and holds the load current to a predetermined current value greater than zero until the overcurrent condition is removed.

2. The switching regulator according to claim 1,

wherein the overcurrent detection circuit includes:

a first reference voltage circuit which outputs a reference voltage used for an overcurrent detection in a normal state, and outputs a reference voltage used for an overcurrent release in an overcurrent state; and

a comparator which compares a voltage based on the load current with the reference voltage used for the overcurrent detection or the reference voltage used for the reference voltage used for the overcurrent release, and when the overcurrent state is detected, outputs the overcurrent detection signal.

3. The switching regulator according to claim 1,

wherein the negative feedback control circuit includes:

a transistor which adjusts the load current and is used for a load current limit;

a second reference voltage circuit which outputs the reference voltage used for the load current limit; and

an amplifier which compares the voltage based on the load current with the reference voltage used for the load current limit, and outputs a signal controlling the transistor used for the load current limit.

4. The switching regulator according to claim 3, wherein the transistor used for the load current limit is provided between a power supply and the output transistor.

5. An electronic device comprising:

a power supply; and

the switching regulator, which outputs a constant voltage obtained by adjusting a power supply voltage of the power supply, according to claim 1.