ISOLATED DC/DC CONVERTER, POWER SUPPLY DEVICE, POWER SUPPLY ADAPTOR, AND ELECTRONIC DEVICE USING THE SAME, AND FEEDBACK AMPLIFIER INTEGRATED CIRCUIT

• US 20160181932A1
• Filed: 12/11/2015
• Published: 06/23/2016
• Est. Priority Date: 12/17/2014
• Status: Abandoned Application

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: KIKUCHI, Hiroki, OYAMA, Manabu, SHIMIZU, Ryo
• Application Number:
  US14/966,423
• Publication Number:
  US 20160181932A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An isolated 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 feedback amplifier connected to an input side of the photo coupler and configured to generate an error current which increases as an output voltage of the DC/DC converter decreases; a primary side controller having a feedback terminal and configured to switch the switching transistor with a larger duty ratio as a voltage of the feedback terminal becomes higher; and a non-inversion type feedback circuit connected to the output side of the photo coupler and the feedback terminal and configured to increase the voltage of the feedback terminal as a feedback current flowing through the output side of the photo coupler increases.

Claims

1. An isolated 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 feedback amplifier connected to an input side of the photo coupler and configured to generate an error current which increases as an output voltage of the DC/DC converter decreases;

a primary side controller having a feedback terminal and configured to switch the switching transistor with a larger duty ratio as a voltage of the feedback terminal becomes higher; and

an non-inversion type feedback circuit connected to an output side of the photo coupler and the feedback terminal and configured to increase the voltage of the feedback terminal as a feedback current flowing through the output side of the photo coupler increases.

2. The isolated DC/DC converter of claim 1, wherein the non-inversion type feedback circuit includes a resistor placed between the feedback terminal and a ground, and

wherein the photo coupler is connected to the feedback terminal such that the photo coupler sources the feedback current.

3. The isolated DC/DC converter of claim 1, wherein the non-inversion type feedback circuit includes a capacitor placed between the feedback terminal and a ground, and

wherein the photo coupler is connected to the feedback terminal such that the photo coupler sources the feedback current.

4. The isolated DC/DC converter of claim 1, wherein the feedback amplifier includes:

a reference voltage source which generates a reference voltage;

a differential amplifier having a non-inverted input terminal, to which a detection signal corresponding to the output voltage of the DC/DC converter is input, and an inverted input terminal to which the reference voltage is input; and

an output transistor having a control terminal connected to an output of the differential amplifier, a first terminal connected to the input side of the photo coupler, and a second terminal connected to a ground terminal.

5. The isolated DC/DC converter of claim 1, wherein the rectification element includes a synchronous rectification transistor, and the isolated DC/DC converter further comprises a synchronous rectification controller which controls the synchronous rectification transistor.

6. The isolated DC/DC converter of claim 1, wherein the isolated DC/DC converter is of a flyback type.

7. The isolated DC/DC converter of claim 1, wherein the isolated DC/DC converter is of a forward type.

8. A power supply 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

DC/DC converter of claim 1, which is configured to drop down the DC input voltage and supply the dropped-down voltage to a load.

9. 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

DC/DC converter of claim 1, which is configured to drop down the DC input voltage and supply the dropped-down DC input voltage to a load.

10. 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

DC/DC converter of claim 1, which is configured to drop down the DC input voltage and supply the dropped-down voltage to a load.

11. A feedback amplifier integrated circuit disposed at a secondary side of an isolated DC/DC converter, wherein the isolated 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 has a feedback terminal and switches the switching transistor with a duty ratio corresponding to a voltage of the feedback terminal;

a non-inversion type feedback circuit which is connected to the feedback terminal and configured to increase the voltage of the feedback terminal as a feedback current flowing through an output side of the photo coupler increases; and

the feedback amplifier integrated circuit,

wherein the feedback amplifier integrated circuit comprises;

an output terminal connected to an input side of the photo coupler;

an input terminal which receives a detection signal corresponding to an output voltage of the DC/DC converter;

a ground terminal;

a reference voltage source which generates a reference voltage;

a differential amplifier having a non-inverted input terminal, to which the detection signal is input, and an inverted input terminal to which the reference voltage is input; and

an output transistor having a control terminal connected to an output of the differential amplifier, a first terminal connected to the output terminal, and a second terminal connected to the ground terminal, and

wherein the feedback amplifier integrated circuit is packaged into a single module.