DC-DC converter

• US 7,436,163 B2
• Filed: 12/08/2006
• Issued: 10/14/2008
• Est. Priority Date: 04/14/2003
• Status: Expired due to Fees

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: Katoh, Tomonari
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US11/635,763
• Publication Number:
  US 20070145964A1
• Time in Patent Office: 676 Days
• Field of Search: 323/282, 323/283, 323/284, 323/285, 323/351, 363/50, 363/59, 363/60
• US Class Current: 323/285
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps

Abstract

A DC-DC converter is disclosed that includes a constant voltage circuit outputting a first voltage, a charge pump circuit outputting a second voltage, a current detection circuit converting the output current of the constant voltage circuit into a third voltage and outputting the third voltage, a first detection circuit detecting the first voltage and outputting a first detection voltage proportional thereto, a first overcurrent protection circuit comparing the third voltage and the first detection voltage and reducing the output first voltage and current of the constant voltage circuit when the third voltage exceeds the first detection voltage, a second detection circuit detecting the second voltage and outputting a second detection voltage proportional thereto, and a second overcurrent protection circuit comparing the third voltage and the second detection voltage and reducing the output first voltage and current of the constant voltage circuit when the third voltage exceeds the second detection voltage.

Claims

1. A DC-DC converter of a charge pump type, comprising:

a constant voltage circuit for outputting a first voltage;

a charge pump circuit for outputting a second voltage based on the first voltage;

a current detection circuit for outputting a third voltage based on an output current of the constant voltage circuit;

a first output voltage detection circuit for outputting a first detection voltage proportional to the first voltage;

a first overcurrent protection circuit for reducing the first voltage and the output current of the constant voltage circuit based on a comparison of the third voltage and the first detection voltage;

a second output voltage detection circuit for outputting a second detection voltage proportional to the second voltage; and

a second overcurrent protection circuit for reducing the first voltage and the output current of the constant voltage circuit based on a comparison of the third voltage and the second detection voltage.

2. The DC-DC converter of claim 1, wherein the first overcurrent protection circuit reduces the first voltage and the output current of the constant voltage circuit when the third voltage is greater than the first detection voltage.

3. The DC-DC converter of claim 1, wherein the second overcurrent protection circuit reduces the first voltage and the output current of the constant voltage circuit when the third voltage is greater than the second detection voltage.

4. The DC-DC converter of claim 1, wherein the first output voltage detection circuit generates and outputs the first detection voltage so that the first detection voltage is higher than the second detection voltage when the first voltage output from the constant voltage circuit is higher than the second voltage output from the charge pump circuit.

5. The DC-DC converter of claim 1, wherein the first overcurrent protection circuit operates when the first voltage output from the constant voltage circuit is lower than the second voltage output from the charge pump circuit.

6. The DC-DC converter of claim 1, wherein the second overcurrent protection circuit operates when the second voltage output from the charge pump circuit is lower than the first voltage output from the constant voltage circuit.

7. A DC-DC converter of a charge pump type, comprising:

constant voltage means for outputting a first voltage;

charge pump means for outputting a second voltage based on the first voltage;

current detection means for outputting a third voltage based on an output current of the constant voltage means;

first output voltage detection means for outputting a first detection voltage proportional to the first voltage;

first overcurrent protection means for reducing the first voltage and the output current of the constant voltage means based on a comparison of the third voltage and the first detection voltage;

second output voltage detection means for outputting a second detection voltage proportional to the second voltage; and

second overcurrent protection means for reducing the first voltage and the output current of the constant voltage means based on a comparison of the third voltage and the second detection voltage.

8. The DC-DC converter of claim 7, wherein the first overcurrent protection means reduces the first voltage and the output current of the constant voltage means when the third voltage is greater than the first detection voltage.

9. The DC-DC converter of claim 7, wherein the second overcurrent protection means reduces the first voltage and the output current of the constant voltage means when the third voltage is greater than the second detection voltage.

10. The DC-DC converter of claim 7, wherein the first output voltage detection means generates and outputs the first detection voltage so that the first detection voltage is higher than the second detection voltage when the first voltage output from the constant voltage means is higher than the second voltage output from the charge pump means.

11. The DC-DC converter of claim 7, wherein the first overcurrent protection means operates when the first voltage output from the constant voltage means is lower than the second voltage output from the charge pump means.

12. The DC-DC converter of claim 7, wherein the second overcurrent protection means operates when the second voltage output from the charge pump means is lower than the first voltage output from the constant voltage means.

13. A method comprising:

outputting a first voltage from a first circuit part;

outputting a second voltage from a second circuit part based on the first voltage;

outputting a third voltage from a third circuit part based on an output current of the first voltage;

outputting a detection voltage from a fourth circuit part, wherein the detection voltage is proportional to the first voltage; and

reducing the first voltage and the output current of the first circuit part based on a comparison of the third voltage and the detection voltage from the fourth circuit part.