DC-DC CONVERTER, POWER SUPPLY VOLTAGE SUPPLYING METHOD, AND POWER SUPPLY VOLTAGE SUPPLYING SYSTEM

• US 20080238394A1
• Filed: 03/26/2008
• Published: 10/02/2008
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Monterey Research, LLC (Vector Capital Corporation)
• Original Assignee: Fujitsu Limited
• Inventors: MATSUMOTO, Takashi, NAGAI, Ryuta, HASEGAWA, Morihito
• Granted Patent: US 7,916,503 B2
• Time in Patent Office: Days
• US Class Current: 323/283
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

According to one aspect of the invention, a DC-DC converter including a soft-start function of a soft start in response to a soft-start signal, comprises: a detection circuit that detects whether the soft-start signal is active at an end of a soft-start operation; and an output voltage control circuit that controls an output voltage based on detection result of the detection circuit.

Claims

1. A DC-DC converter including a soft-start function of a soft start in response to a soft-start signal, comprising:

a detection circuit that detects whether the soft-start signal is active at an end of a soft-start operation; and

an output voltage control circuit that controls an output voltage based on detection result of the detection circuit.

2. The DC-DC converter according to claim 1, wherein the output voltage control circuit maintains the output voltage when the detection result indicates that the soft-start signal is active, and decreases the output voltage when the detection result indicates that the soft-start signal is inactive.

3. The DC-DC converter according to claim 1, wherein a completion of a soft-start operation is determined based on whether the output voltage reaches a terminal voltage set according to the soft-start function.

4. The DC-DC converter according to claim 1, further comprising:

an error amplifier that includes an input portion for receiving a soft-start-related signal, wherein the error amplifier amplifies a difference between the output voltage and a reference voltage; and

a PWM control circuit that controls a first switching transistor and a second switching transistor based on the output of the error amplifier.

5. A DC-DC converter comprising:

an input circuit that receives an external soft-start signal;

a soft-start conversion circuit that converts the external soft-start signal into an internal soft-start signal; and

a soft-start starting circuit that starts a soft-start operation in response to an activation of the internal soft-start signal,

wherein the soft-start conversion circuit includes;

a detection circuit that detects whether the soft-start signal is active at an end of a soft-start operation; and

an output voltage control circuit that controls an output voltage based on a detection result of the detection circuit.

6. The DC-DC converter according to claim 5, wherein the soft-start conversion circuit makes the internal soft-start signal inactive when the detection result indicates that the external soft-start signal is inactive.

7. The DC-DC converter according to claim 5, wherein a completion of a soft-start operation is determined based on whether the output voltage reaches a terminal voltage set according to the soft-start function.

8. The DC-DC converter according to claim 5, further comprising:

an error amplifier that includes an input portion for receiving a soft-start-related signal, wherein the error amplifier amplifies a difference between the output voltage and a reference voltage; and

a PWM control circuit that controls a first switching transistor and a second switching transistor based on the output of the error amplifier.

9. A power supply voltage supplying method comprising:

receiving a soft-start signal;

starting a soft-start operation in response to an activation of the soft-start signal;

detecting whether the soft-start signal is active at an end of the soft-start operation; and

controlling an output voltage based on a detection result.

10. The power supply voltage supplying method according to claim 9, further comprising:

maintaining the output voltage when the detection result indicates that the soft-start signal is active; and

decreasing the output voltage when the detection result indicates that the soft-start signal is inactive.

11. A power supply voltage supplying system comprising:

a CPU; and

a DC-DC converter that performs a soft-start operation based on a soft-start signal supplied from the CPU, the DC-DC converter including;

a detection circuit that detects whether the soft-start signal is active at an end of a soft-start operation; and

an output voltage control circuit that controls an output voltage based on a detection result of the detection circuit.

12. The power supply voltage supplying system according to claim 11, wherein the output voltage control circuit maintains the output voltage when the detection result indicates that the soft-start signal is active, and decreases the output voltage when the detection result indicates that the soft-start signal is inactive.

13. A DC-DC converter including a soft-start function in response to a soft-start signal, comprising:

a circuit that detects an output voltage in response to an activation of the soft-start signal and starts a soft-start operation when the output voltage falls within a prescribed range including a ground potential.

14. The DC-DC converter according to claim 13, further comprising:

an error amplifier that includes an input portion for receiving a soft-start-related signal, wherein the error amplifier amplifies a difference between the output voltage and a reference voltage; and

a PWM control circuit that controls a first switching transistor and a second switching transistor based on the output of the error amplifier.

15. The DC-DC converter according to claim 13, further comprising:

a comparison circuit that compares the output voltage with a ground potential;

a first latch circuit that latches a comparison result of the comparison circuit in response to the soft-start signal;

a second latch circuit that latches the soft-start signal in response to the comparison result; and

a logical operation circuit that performs a logical operation of outputs of the first circuit and the second latch circuit.

16. A DC-DC converter comprising:

an input circuit that receives an external soft-start signal;

a soft-start conversion circuit that converts the external soft-start signal into an internal soft-start signal;

a soft-start starting circuit that starts a soft-start operation in response to activation of the internal soft-start signal; and

a circuit that detects an output voltage in response to activation of the soft-start signal and starts a soft-start operation when the output voltage falls within a prescribed range including a ground potential.

17. The DC-DC converter according to claim 16, wherein the soft-start conversion circuit includes:

a comparison circuit that compares the output voltage with the ground potential;

a first latch circuit that latches the comparison result in response to the soft-start signal;

a second latch circuit that latches the soft-start signal in response to the comparison result; and

a logical operation circuit that performs a logical operation on outputs of the first circuit and the second latch circuit.

18. A power supply voltage supplying method for starting supply of a power supply voltage by starting a soft start based on a soft-start signal which is activated at a time of power-on or resetting, comprising:

receiving the soft-start signal;

detecting an output voltage in response to an activation of the soft-start signal; and

starting a soft-start operation when the output voltage falls within a prescribed range including a ground potential.

19. A power supply voltage supplying system comprising:

a CPU; and

a DC-DC converter that performs a soft-start operation based on a soft-start signal supplied from the CPU, the DC-DC converter including;

a circuit that detects an output voltage in response to activation of the soft-start signal and that starts a soft-start operation when the output voltage falls within a prescribed range including a ground potential.

20. The power supply voltage supplying system according to claim 19, wherein the DC-DC converter further comprises:

an error amplifier that includes an input portion for receiving a soft-start-related signal, wherein the error amplifier amplifies a difference between the output voltage and a reference voltage; and

a PWM control circuit that controls the first switching transistor and the second switching transistor based on the output of the error amplifier.