Method of controlling DC/DC converter

• US 20020071295A1
• Filed: 11/29/2001
• Published: 06/13/2002
• Est. Priority Date: 12/11/2000
• Status: Active Grant

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Nishikawa, Yukihiro
• Granted Patent: US 6,507,504 B2
• Time in Patent Office: Days
• US Class Current: 363/21.15
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/33515 with digital control
• CPC Class Codes: 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

Abstract

A DC/DC converter converts a voltage of a DC power supply to another DC voltage by switching on and off a switching element, which determines an oscillating period and a forced stop period of the switching element based on a comparison signal obtained by comparing an output of an output-voltage detecting and adjusting circuit, which controls the output of the DC/DC converter at a certain voltage, and an output of a triangular-wave generating circuit in a second comparator. The DC/DC converter facilitates confining the pulsation of the output voltage of the DC/DC converter caused by the maximum load in the state of light load including the state of no load, within an allowable range, and reducing the switching and conduction losses.

Claims

1. A method of controlling a DC/DC converter, comprising:

obtaining an output signal from an output voltage detecting and adjusting circuit, which controls an output of the DC/DC converter at a constant DC voltage, to use as a reference signal for determining an on-off timing of a switching element,

comparing the reference signal and a carrier signal of a constant frequency,

providing to the switching element a control signal for controlling an oscillating period and a forced stop period of the switching element in a state of light load including a state of no load, said control signal being obtained from a comparison signal by comparing the reference signal and the carrier signal to thereby operate the switching element on and off intermittently to convert a voltage supplied from a DC power supply to a constant DC voltage.

2. A method of controlling a DC/DC converter according to claim 1, wherein the carrier signal is a triangular wave or a saw-teeth wave.

3. A method of controlling a DC/DC converter according to claim 1, further comprising:

inputting the output signal from the output voltage detecting and adjusting circuit to an impedance conversion element; and

obtaining an output from the impedance conversion element as the reference signal for determining an on-off timing of the switching element, said output from the impedance conversion element being lowered to control the forced stop period of the switching element.

4. A method of controlling a DC/DC converter according to claim 2, further comprising:

inputting the output signal from the output voltage detecting and adjusting circuit to an impedance conversion element; and

obtaining an output from the impedance conversion element as the reference signal for determining an on-off timing of the switching element, said output from the impedance conversion element being lowered to control the forced stop period of the switching element.

5. A method of controlling a DC/DC converter according to claim 3, wherein said impedance conversion element is a voltage follower.

6. A method of controlling a DC/DC converter according to claim 4, wherein said impedance conversion element is a voltage follower.

7. A method of controlling a DC/DC converter according to claim 1, further comprising:

charging a capacitor at a constant current at a first changeover timing when the forced stop period is changed to the oscillating period by using the control signal for controlling the oscillating period and the forced stop period;

discharging the capacitor at a constant current at a second changeover timing when the oscillating period is changed to the forced stop period by using the control signal;

comparing the voltage of the capacitor and the reference signal with each other; and

using smaller one of the voltage of the capacitor and the reference signal as a new control signal for determining the on-off timing of the switching element.

8. A method of controlling a DC/DC converter according to claim 2, further comprising:

charging a capacitor at a constant current at a first changeover timing when the forced stop period is changed to the oscillating period by using the control signal for controlling the oscillating period and the forced stop period;

discharging the capacitor at a constant current at a second changeover timing when the oscillating period is changed to the forced stop period by using the control signal;

comparing the voltage of the capacitor and the reference signal with each other; and

using smaller one of the voltage of the capacitor and the reference signal as a new control signal for determining the on-off timing of the switching element.