Isolated dc/dc converter, feedback circuit thereof, power supply device, power supply adaptor, and electronic device using the same

Patent metadata

Field	Value
Publication number	US-2016261202-A1
Application number	US-201615057522-A
Country	US
Kind code	A1
Filing date	Mar 1, 2016
Priority date	Mar 5, 2015
Publication date	Sep 8, 2016
Grant date	—

Abstract

A feedback circuit includes: an input terminal which receives a voltage detection signal corresponding to an output voltage of a DC/DC converter; an output terminal connected to an input side of the photo coupler; a ground terminal; a shunt regulator configured to amplify an error between the voltage detection signal and its target voltage and pull up a first current corresponding to the error from the input side of the photo coupler via the output terminal; and a protection circuit configured to pull up a second current from the input side of the photo coupler via the output terminal when an abnormality of the secondary side of the DC/DC converter is detected. The feedback circuit is packaged into a single module.

First claim

What is claimed is:

1 . A feedback circuit disposed at a secondary side of an isolated DC/DC converter, wherein the DC/DC converter includes:
a transformer having a primary winding and a secondary winding; a switching transistor connected to the primary winding of the transformer; a rectification element connected to the secondary winding of the transformer; a photo coupler; a primary side controller which is connected to an output side of the photo coupler and is configured to switch the switching transistor in response to a feedback signal from the photo coupler; and the feedback circuit configured to drive the photo coupler, the feedback circuit comprising:
an input terminal which receives a voltage detection signal corresponding to an output voltage of the DC/DC converter;
an output terminal connected to an input side of the photo coupler;
a ground terminal;
a shunt regulator configured to amplify an error between the voltage detection signal and its target voltage and draw a first current corresponding to the error from the input side of the photo coupler via the output terminal; and
a protection circuit configured to draw a second current from the input side of the photo coupler via the output terminal when an abnormality of the secondary side of the DC/DC converter is detected, and
wherein the feedback circuit is packaged in a single module.

2 . The feedback circuit of claim 1 , wherein the protection circuit includes a protection transistor having one end connected to the output terminal and the other end connected to the ground terminal, the protection transistor being turned on when the abnormality is detected.

3 . The feedback circuit of claim 1 , wherein the DC/DC converter further includes an abnormality detection circuit which is disposed at the secondary side and is configured to generate an abnormality detection signal to be asserted when the abnormality is detected,
the feedback circuit further comprising a sense terminal to which the abnormality detection signal is input and wherein the protection circuit draws the second current when the abnormality detection signal is asserted.

4 . The feedback circuit of claim 3 , wherein the abnormality detection circuit is configured to detect at least one of an overvoltage state and a high temperature state of the secondary side of the DC/DC converter.

5 . The feedback circuit of claim 1 , further comprising an abnormality detection circuit which is configured to determine whether the abnormality is present in the secondary side and assert an abnormality detection signal when the abnormality is detected,
wherein the protection circuit draws the second current when the abnormality detection signal is asserted.

6 . The feedback circuit of claim 5 , further comprising a sense terminal to which a sense signal indicating a state of the secondary side of the DC/DC converter is input,
wherein the abnormality detection circuit determines whether the abnormality is present, based on an electrical state of the sense terminal.

7 . The feedback circuit of claim 1 , further comprising:
a sense terminal to which a sense signal indicating a state of the secondary side of the DC/DC converter is input; and an abnormality detection comparator configured to compare a voltage of the sense terminal with a predetermined threshold voltage and generate an abnormality detection signal indicating a result of the comparison, wherein the protection circuit draws the second current when the abnormality detection signal is asserted.

8 . The feedback circuit of claim 7 , wherein an overvoltage detection signal corresponding to an output voltage of the DC/DC converter is input to the sense terminal, and
wherein the abnormality detection comparator detects an overvoltage state.

9 . The feedback circuit of claim 7 , wherein a temperature sensing element is connected to the sense terminal, and
wherein the abnormality detection comparator detects high temperature abnormality.

10 . The feedback circuit of claim 1 , wherein the shunt regulator includes:
a differential amplifier configured to amplify the error between the voltage detection signal and its target voltage; and an output transistor having one end connected to the output terminal, the other end connected to the ground terminal, and a control terminal to which an output signal of the differential amplifier is input.

11 . A DC/DC converter comprising:
a transformer having a primary winding and a secondary winding; a switching transistor connected to the primary winding of the transformer; a rectification element connected to the secondary winding of the transformer; a photo coupler; a primary side controller which is connected to an output side of the photo coupler and is configured to switch the switching transistor in response to a feedback signal from the photo coupler; and the feedback circuit of claim 1 , which is configured to drive the photo coupler.

12 . A power supply device comprising:
a filter configured to filter a commercial AC voltage; a diode rectification circuit configured to full-wave rectify an output voltage of the filter; a smoothing capacitor configured to generate a DC input voltage by smoothing an output voltage of the diode rectification circuit; and the DC/DC converter of claim 11 , which is configured to drop down the DC input voltage and supply the dropped-down voltage to a load.

13 . An electronic device comprising:
a load; a filter configured to filter a commercial AC voltage; a diode rectification circuit configured to full-wave rectify an output voltage of the filter; a smoothing capacitor configured to generate a DC input voltage by smoothing an output voltage of the diode rectification circuit; and the DC/DC converter of claim 11 , which is configured to drop down the DC input voltage and supply the dropped-down DC input voltage to the load.

14 . A power supply adaptor comprising:
a filter configured to filter a commercial AC voltage; a diode rectification circuit configured to full-wave rectify an output voltage of the filter; a smoothing capacitor configured to generate a DC input voltage by smoothing an output voltage of the diode rectification circuit; and the DC/DC converter of claim 11 , which is configured to drop down the DC input voltage to generate a DC output voltage.

Assignees

• Rohm Co Ltd

Inventors

• Kikuchi Hiroki
• Shimizu Ryo

Classifications

• H02M3/33523 Primary

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title