Semiconductor device

Patent metadata

Field	Value
Publication number	US-2017093145-A1
Application number	US-201615278179-A
Country	US
Kind code	A1
Filing date	Sep 28, 2016
Priority date	Sep 29, 2015
Publication date	Mar 30, 2017
Grant date	—

Abstract

A semiconductor device includes an integration of a first external terminal to which a DC input voltage is input, a second external terminal to which a rectifying and smoothing circuit is externally connected, an output transistor connected between the first external terminal and the second external terminal, a control circuit arranged to turn on and off the output transistor so that a desired DC output voltage can be obtained from the rectifying and smoothing circuit, a current detection circuit arranged to generate a sense voltage corresponding to an on-current of the output transistor, and an overcurrent protection circuit arranged to monitor the sense voltage so as to perform an overcurrent protection operation. The overcurrent protection circuit performs a first overcurrent protection operation of a pulse-by-pulse method when detecting that the sense voltage exceeds a first threshold value voltage, and performs a second overcurrent protection operation of a timer latch method when detecting that the sense voltage continues to increase though the first overcurrent protection operation is being performed.

First claim

What is claimed is:

1 . A semiconductor device comprising an integration of:
a first external terminal to which a DC input voltage is input; a second external terminal to which a rectifying and smoothing circuit is externally connected; an output transistor connected between the first external terminal and the second external terminal; a control circuit arranged to turn on and off the output transistor so that a desired DC output voltage can be obtained from the rectifying and smoothing circuit; a current detection circuit arranged to generate a sense voltage corresponding to an on-current of the output transistor; and an overcurrent protection circuit arranged to monitor the sense voltage so as to perform an overcurrent protection operation, wherein the overcurrent protection circuit performs a first overcurrent protection operation of a pulse-by-pulse method when detecting that the sense voltage exceeds a first threshold value voltage, and performs a second overcurrent protection operation of a timer latch method when detecting that the sense voltage continues to increase though the first overcurrent protection operation is being performed.

2 . The semiconductor device according to claim 1 , wherein
the overcurrent protection circuit includes a first comparator arranged to compare the sense voltage with the first threshold value voltage so as to generate a first comparison signal, and the control circuit forcibly turns off the output transistor until an on timing of a next period so that the first overcurrent protection operation is performed according to the first comparison signal.

3 . The semiconductor device according to claim 2 , wherein the overcurrent protection circuit includes
a second comparator arranged to compare the sense voltage with a second threshold value voltage higher than the first threshold value voltage so as to generate a second comparison signal, a counter arranged to generate a one-shot signal when a pulse of the second comparison signal is detected continuously for a plurality of periods, and a timer arranged to generate a timer signal for a predetermined time by a trigger of the one-shot signal, wherein the control circuit forcibly turns off the output transistor for the predetermined time so that the second overcurrent protection operation is performed according to the timer signal.

4 . The semiconductor device according to claim 2 , wherein the overcurrent protection circuit includes
a second comparator arranged to compare the sense voltage with a second threshold value voltage higher than the first threshold value voltage so as to generate a second comparison signal, a third comparator arranged to compare the sense voltage with a third threshold value voltage higher than the first threshold value voltage and lower than the second threshold value voltage, so as to generate a third comparison signal, a logic unit arranged to generate a one-shot signal when a pulse of the third comparison signal is detected and then in the next period a pulse of the second comparison signal is detected, and a timer arranged to generate a timer signal for a predetermined time by a trigger of the one-shot signal, wherein the control circuit forcibly turns off the output transistor for the predetermined time so that the second overcurrent protection operation is performed according to the timer signal.

5 . The semiconductor device according to claim 1 , further comprising an integrated filter circuit connected between the current detection circuit and the overcurrent protection circuit.

6 . The semiconductor device according to claim 1 , wherein the current detection circuit generates the sense voltage from the on-current using one of a wiring resistance of a current path in which the on-current flows, an on-resistance of the output transistor, and an on-resistance of a transistor for monitoring current connected in parallel to the output transistor.

7 . A DC/DC converter comprising:
a semiconductor device according to claim 1 ; and a rectifying and smoothing circuit externally connected to the semiconductor device so as to generate a desired DC output voltage.

8 . The DC/DC converter according to claim 7 , further comprising a power supply voltage generation circuit externally connected to the semiconductor device so as to generate a power supply voltage of the semiconductor device from the DC output voltage.

9 . A power supply device comprising:
an AC/DC converter arranged to generate a DC input voltage from an AC input voltage; and a DC/DC converter according to claim 7 arranged to generate a desired DC output voltage from the DC input voltage.

10 . An electronic apparatus comprising:
a power supply device according to claim 9 arranged to generate a desired DC output voltage from a AC input voltage; and a load arranged to receive supply of the DC output voltage so as to operate.

Assignees

• Rohm Co Ltd

Inventors

• Nate Satoru

Classifications

• H02H7/1213

  for DC-DC converters · CPC title

• H02H3/025

  Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection · CPC title

• H02H9/02

  responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)} · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M7/217

  using semiconductor devices only · CPC title