# US 7,612,545 B2 · DC/DC converter

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- Number: US 7,612,545 B2
- Document ID: US7612545B2
- Status: Granted
- Kind: B2
- Application number: 10/595,785
- Filed: 2004-11-11
- Published: 2008-01-24
- Granted: 2009-11-03
- Earliest claimed: 2003-11-11
- Assignees: Rohm Co., Ltd.
- Inventors: Kiyotaka Umemoto; Ko Takemura
- Web page: https://patentgrep.com/patent/US7612545B2

## CPC

- H02M 3/1588: {comprising at least one synchronous rectifier element (H02M3/1582, H02M3/1584 take precedence)}
- 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
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A DC/DC converter includes a switching element which is opened and closed to supply power from an input power supply Vcc through a coil to an output terminal, which is connected to a load, and to adjust the voltage at the output terminal. The DC/DC converter also includes a coil current detection resistor arranged to detect a coil current, a smoothing capacitor connected to the load side of the coil current detection resistor and arranged to smooth the voltage at the output terminal, a reference current value control circuit arranged to detect the voltage on the coil side of the coil current detection resistor to control a reference current value of the coil current, a clock generator arranged to generate a reference clock, and a feedback circuit arranged to close the switching element in synchrony with the reference clock and to open the switching element when the coil current exceeds the reference current value.

## Claims

### Claim 1

A DC/DC converter for, through the opening and closing of a switching element, supplying power from an input power supply, via a coil, to an output terminal connected to a load, and adjusting a voltage of the output terminal, the DC/DC converter comprising:
a coil current detection element interposed between the coil and the output terminal, and arranged to generate, in a terminal connected to the coil and a terminal connected to the output terminal, a detection voltage in response to a coil current;
a smoothing capacitor connected to the load side of the coil current detection element to smooth the voltage of the output terminal;
a reference current value control circuit arranged to detect the voltage of the coil side of the coil current detection element and to control a reference current value of a current flowing in the coil; and
a feedback circuit having an offset voltage generator arranged to generate an offset voltage that corresponds to the reference current value in response to an output voltage of the reference current value control circuit, and arranged to close the switching element in synchronization with a reference clock signal of a clock signal generator, and open the switching element in response to comparing the detection voltage with the offset voltage when the current flowing in the coil exceeds the reference current value.

### Claim 2 (depends on 1)

The DC/DC converter according to claim 1, wherein the coil current detection element is a coil current detection resistor.

### Claim 3 (depends on 1)

The DC/DC converter according to claim 1, wherein the smoothing capacitor is a ceramic capacitor.

### Claim 4 (depends on 1)

The DC/DC converter according to claim 1, wherein an equivalent series resistance value of the smoothing capacitor is smaller than that of an electrolytic capacitor.

### Claim 5 (depends on 1)

The DC/DC converter according to claim 1, wherein the resistance value of the coil current detection element is larger than the equivalent series resistance value of the smoothing capacitor.

### Claim 6 (depends on 1)

The DC/DC converter according to claim 1, wherein the zero frequency of a frequency characteristic is determined by the coil current detection element and the smoothing capacitor.