Switching regulator

• US 7,589,509 B2
• Filed: 09/13/2007
• Issued: 09/15/2009
• Est. Priority Date: 09/14/2006
• Status: Expired due to Fees

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: Nishida, Junji
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US11/898,623
• Publication Number:
  US 20080068054A1
• Time in Patent Office: 733 Days
• Field of Search: 323/283, 323/282, 323/284, 327/14, 327/170
• US Class Current: 323/283
• CPC Class Codes: H03K 4/502 the capacitor being charged from a constant-current source

Abstract

A switching regulator that includes a switching transistor configured to control an output current by switching, a proportional current generator configured to generate a current proportional to a current flowing through the switching transistor, a first slope voltage generator configured to generate a linear slope voltage, a second slope voltage generator configured to generate a slope voltage having a secondary curve characteristic by integrating the current proportional to the current flowing through the switching transistor, and a slope voltage compensation circuit to generate a superimposed slope voltage formed by superimposing an output voltage of the first slope voltage generator on an output voltage of the second slope voltage generator.

Claims

1. A slope voltage compensator, comprising:

a switching transistor configured to control an output current by switching;

a proportional current generator configured to generate a current proportional to a current flowing through the switching transistor;

a first slope voltage generator configured to generate a linear slope voltage;

a second slope voltage generator configured to generate a slope voltage having a secondary curve characteristic by integrating the current proportional to the current flowing through the switching transistor; and

a slope voltage compensation circuit to generate a superimposed slope voltage formed by superimposing an output voltage of the first slope voltage generator on an output voltage of the second slope voltage generator.

2. The slope voltage compensator of claim 1, wherein the first slope voltage generator comprises:

a current source; and

a capacitor to be charged by an output current of the current source and to output a linear slope voltage.

3. The slope voltage compensator of claim 2, wherein the first slope voltage generator further comprises a resistor provided between the current source and the capacitor and a summational voltage of a voltage drop at the resistor and the voltage of the capacitor is a linear slope voltage.

4. The slope voltage compensator of claim 1, wherein the second slope voltage generator comprises a capacitor to be charged by a proportional current of the proportional current generator and to output the slope voltage having the secondary curve characteristic.

5. The slope voltage compensator of claim 4, wherein the second slope voltage generator further comprises a resistor provided between the proportional current generator and the capacitor, and a summational voltage of a voltage drop at the resistor and the voltage of the capacitor is a secondary curved slope voltage.

6. The slope voltage compensator of claim 1, wherein the first slope voltage generator comprises:

a current source;

a capacitor to be charged by an output current of the current source and to output a linear slope voltage; and

a resistor provided between the current source and the capacitor,

wherein the second slope voltage generator comprises;

a capacitor to be charged by a proportional current of the proportional current generator and to output the slope voltage having the secondary curve characteristic; and

a resistor provided between the proportional current generator and the capacitor,

and wherein one capacitor is provided commonly to be charged by the output current of the current source and by the proportional current of the proportional current generator.

7. The slope voltage compensator of claim 6, wherein resistances of the resistors provided in the first and second slope voltage generators are variable.

8. The slope voltage compensator of claim 1, wherein the switching transistor comprises a first MOS transistor, and the proportional current generator comprises a second MOS transistor that forms a current mirror circuit with the first MOS transistor and has an equal conductivity to the first MOS transistor.

9. The slope voltage compensator of claim 8, wherein:

the second MOS transistor comprises a plurality of unit MOS transistors serially connected;

each unit MOS transistor has a gate length equal to a gate length of the first MOS transistor;

one end of the unit MOS transistors serially connected is used as a source of the second MOS transistor, another end is used as a drain of the second MOS transistor, and a connection node of all gates of the unit MOS transistors is used as a gate of second MOS transistor;

the second MOS transistor is divided into unit transistor groups each having a predetermined number of the unit MOS transistors; and

backgates of each unit MOS transistor are commonly connected in the unit transistor group and a backgate node commonly connected is connected to a source of the unit transistor.

10. A switching regulator employing a slope voltage compensator, the slope voltage compensator comprising:

a switching transistor configured to control an output current by switching;

a proportional current generator configured to generate a current proportional to a current flowing through the switching transistor;

a first slope voltage generator configured to generate a linear slope voltage;

a second slope voltage generator configured to generate a slope voltage having a secondary curve characteristic by integrating the current proportional to the current flowing through the switching transistor; and

a slope voltage compensation circuit to generate a superimposed slope voltage formed by superimposing an output voltage of the first slope voltage generator on an output voltage of the second slope voltage generator.