DC/DC converter

• US 6,400,211 B1
• Filed: 09/18/2001
• Issued: 06/04/2002
• Est. Priority Date: 09/19/2000
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Yokomizo, Ichiro, Horiuchi, Sachito, Matsumae, Mayuka
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/954,036
• Publication Number:
  US 20020034082A1
• Time in Patent Office: 259 Days
• Field of Search: 363/60, 327/536, 330/297, 330/202
• US Class Current: 327/536
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/072 adapted to generate an output voltage whose value is lower than the input voltage

Abstract

A DC/DC converter is provided with a DC power source; a reference voltage generating circuit; an amplifier which receives an electric power from the DC power source and outputs an electric power of which voltage is controlled so as to assume a target voltage value by stepping down the voltage of the electric power from the DC power source depending on a difference between the reference voltage and a detection voltage; an oscillation circuit which generates signals having a specific frequency; a voltage boosting circuit which receives the output of the amplifier and the output of the oscillation circuit, causes switching of the output of the amplifier at the specific frequency to charge a first capacitor, and performs voltage boosting by transferring the electric charges-charged in the first capacitor through complementary ON/OFF switching with respect to the former switching into a second capacitor after raising substantially upto n/m time voltage (wherein n>m and n and m are integers equal to or more than 2) and charging the same therewith; and an output voltage detection circuit which generates the detection voltage depending on the output voltage of the boosting circuit, whereby a voltage of substantially n/m times of the target voltage value is generated from the voltage boosting circuit.

Claims

1. A DC/DC converter characterized in that, the DC/DC converter comprises a DC power source;

a reference voltage generating circuit;

an amplifier which receives an electric power from the DC power source and outputs an electric power of which voltage is controlled so as to assume a target voltage value by stepping down the voltage of the electric power from the DC power source depending on a difference between the reference voltage and a detection voltage;

an oscillation circuit which generates signals having a specific frequency;

a voltage boosting circuit which receives the output of the amplifier and the output of the oscillation circuit, causes switching of the output of the amplifier at the specific frequency to charge a first capacitor, and performs voltage boosting by transferring the electric charges charged in the first capacitor through complementary ON/OFF switching with respect to the former switching into a second capacitor after raising substantially upto n/m time voltage (wherein n>

m and n and m are integers equal to or more than

     2) and charging the same therewith; and

an output voltage detection circuit which generates the detection voltage depending on the output voltage of the boosting circuit, whereby a voltage of substantially n/m times of the target voltage value is generated from the voltage boosting circuit.

2. A DC/DC converter of claim 1, wherein the DC power source is a battery, the amplifier is a differential amplifier at the inputs of which the reference voltage and the detection voltage are respectively received, and the boosting circuit includes a charge pump circuit for charging the first and second capacitors.

3. A DC/DC converter of claim 2, wherein the differential amplifier is to perform an inverted amplification, the oscillation circuit is to generate a pulse for the switching operation, the specific frequency is a frequency having a period which permits the complementary switching after substantially completing the charging of the first capacitor, and the differential amplifier, the charge pump circuit, the oscillation circuit, the output voltage detection circuit and the reference voltage generating circuit are formed in an IC.

4. A DC/DC converter of claim 3, wherein the duty ratio of the pulse is substantially 50%, the charge pump circuit includes a plurality of switch circuits which permit selective ON/OFF switching, and the selective ON/OFF switching of the plurality of switch circuits is performed in response to the pulse.

5. A DC/DC converter of claim 4, wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits, and after charging the first capacitor by grounding one terminal of the first capacitor and by supplying at the other terminal thereof an electric power from the differential amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, and the one terminal of the first capacitor is connected to the output terminal of the differential amplifier to generate a boosted voltage at the other terminal thereof and to thereby charge the second capacitor.

6. A DC/DC converter of claim 4, further comprises a third capacitor wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits to connect the first and third capacitors in series, and after charging the first and third capacitors by grounding one terminal of the series connection and by supplying at the other terminal thereof an electric power from the differential amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, and the one terminal of the series connection circuit is connected to the output terminal of the differential amplifier to generate a substantially three times boosted voltage at the other terminal thereof and to thereby charge the second capacitor.

7. A DC/DC converter of claim 4, further comprises a third capacitor wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits to connect the first and third capacitors in series, and after charging the first and third capacitors by grounding one terminal of the series connection and by supplying at the other terminal thereof an electric power from the differential amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, the series connected first and third capacitors are connected in parallel, and the grounded one terminal is connected to the output terminal of the differential amplifier to generate a substantially 1.5 times boosted voltage at the other terminal thereof and to thereby transfer the electric charges in the first and third capacitors to the second capacitor.

8. A DC/DC converter of claim 1, wherein in place of the reference voltage generating circuit a variable voltage generating circuit is provided and in place of the output voltage detection circuit a voltage control circuit is provided, whereby, the voltage control circuit controls the output voltage of the variable voltage generating circuit depending on the output voltage of the voltage boosting circuit so that the output voltage of the amplifier assumes the target voltage value and causes the amplifier to generate an electric power having the target voltage value.

9. A DC/DC converter characterized in that, the DC/DC a converter comprises a DC power source;

a variable voltage generating circuit;

an amplifier which receives an electric power from the DC power source, amplifies the output voltage of the variable voltage generating circuit and outputs the same;

an oscillation circuit which generates signals having a specific frequency;

a voltage boosting circuit which receives the output of the amplifier and the output of the oscillation, circuit, causes switching of the output of the amplifier at the specific frequency to charge a first capacitor, and performs voltage boosting by transferring the electric charges charged in the first capacitor through complementary ON/OFF switching with respect to the former switching into a second capacitor after raising substantially upto n/m time voltage (wherein n>

m and n and m are integers equal to or more than

     2) and charging the same therewith; and

a voltage control circuit which controls the output voltage of the variable voltage generating circuit depending on the output voltage of the boosting circuit so that the output voltage of the amplifier assumes the target voltage value, whereby a voltage of substantially n/m times of the target voltage value is generated from the voltage boosting circuit.

10. A DC/DC converter of claim 9, wherein the DC power source is a battery, and the boosting circuit includes a charge pump circuit for charging the first and second capacitors.

11. A DC/DC converter of claim 10, wherein the oscillation circuit is to generate a pulse for the switching operation, the specific frequency is a frequency having a period which permits the complementary switching after substantially completing the charging of the first capacitor, and the amplifier, the charge pump circuit, the oscillation circuit, the voltage control circuit and the variable voltage generating circuit are formed in an IC.

12. A DC/DC converter of claim 11, wherein the duty ratio of the pulse is substantially 50%, the charge pump circuit includes a plurality of switch circuits which permit selective ON/OFF switching, and the selective ON/OFF switching of the plurality of switch circuits is performed in response to the pulse.

13. A DC/DC converter of claim 12, wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits, and after charging the first capacitor by grounding one terminal of the first capacitor and by supplying at the other terminal thereof an electric power from the amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, and the one terminal of the first capacitor is connected to the output terminal of the amplifier to generate a boosted voltage at the other terminal thereof and to thereby charge the second capacitor.

14. A DC/DC converter of claim 12, further comprises a third capacitor wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits to connect the first and third capacitors in series, and after charging the first and third capacitors by grounding one terminal of the series connection and by supplying at the other terminal thereof an electric power from the amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, and the one terminal of the series connection circuit is connected to the output terminal of the amplifier to generate a substantially three times boosted voltage at the other terminal thereof and to thereby charge the second capacitor.

15. A DC/DC converter of claim 12, further comprises a third capacitor wherein the charge pump circuit performs the selective ON/OFF switching of the plurality of switch circuits to connect the first and third capacitors in series, and after charging the first and third capacitors by grounding one terminal of the series connection and by supplying at the other terminal thereof an electric power from the amplifier, the ON/OFF switching of the plurality of switch circuits is inverted, the series connected first and third capacitors are connected in parallel, and the grounded one terminal is connected to the output terminal of the amplifier to generate a substantially 1.5 times boosted voltage at the other terminal thereof and to thereby transfer the electric charges in the first and third capacitors to the second capacitor.