DC/DC converter with reduced power consumpton and improved efficiency

• US 5,949,226 A
• Filed: 04/09/1996
• Issued: 09/07/1999
• Est. Priority Date: 04/10/1995
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
• Original Assignee: Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
• Inventors: Tanaka, Hiroto, Aoki, Shinobu
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US08/629,573
• Time in Patent Office: 1,246 Days
• Field of Search: 323/282, 323/284, 323/349-351, 323/273-274, 323/222, 323/303, 323/285, 323/283, 327/538, 363/20-23, 363/19-25
• US Class Current: 323/285
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• 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 comparator monitors an output voltage V_out. When an output voltage V_out decreases to a predetermined output voltage or less, the comparator sends a signal that represents this state to a controlling circuit. When the controlling circuit receives the signal, it causes a switching device to be turned on. Thus, a coil current I_L is increased. A hysteresis (window) comparator monitors the coil current I_L. When the coil current I_L reaches a comparison current I_LP, the controlling circuit causes the switching device to be turned off. When the coil current I_L decreases to the comparison current I_LB (where I_LP >I_LB), the controlling circuit references an output signal of the comparator. When the output voltage V_out is lower than the predetermined output voltage, the controlling circuit causes the switching device to be turned on.

Claims

1. A DC/DC converter for controlling switching means so as to vary a coil current and control an output, the converter comprising:

output monitoring means for monitoring an output value and outputting a first signal when the output value becomes a reference value;

current monitoring means for monitoring a coil current, outputting a second signal when the coil current becomes a first current value and outputting a third signal when the coil current becomes a second current value; and

controlling means for receiving the first, second and third signals, wherein the controlling means turns on the switching means when the first signal is received and turns off the switching means when the second signal is received,

wherein said controlling means is adapted for ignoring the first signal that is output from said output monitoring means after the first signal is received until the third signal is received.

2. The DC/DC converter as set forth in claim 1,

wherein said current monitoring means is composed of a hysteresis comparator.

3. The DC/DC converter as set forth in claim 1,

wherein said current monitoring means is composed of two comparators.

4. The DC/DC converter as set forth in claim 1,

wherein the second current value is 0.

5. The DC/DC converter as set forth in claim 1,

wherein at least a heavy load mode and a light load mode are provided as operation modes for supplying a power to a load, the switching means being controlled corresponding to each of the heavy load mode and the light load mode, and

wherein the period after the first signal is output until the third signal is output is a power supply cycle in the light load mode, the operation mode being switched from the light load mode to the heavy load mode when a predetermined number of the power supply cycles are successively performed.

6. The DC/DC converter as set forth in claim 1,

wherein at least a heavy load mode and a light load mode are provided as operation modes for supplying a power to a load, the switching means being controlled corresponding to each of the heavy load mode and the light load mode,

wherein the period after the first signal is output until the third signal is output is a power supply cycle in the light load mode, and

wherein the DC/DC converter further comprises:

voltage comparing means for comparing an output voltage with a predetermined voltage;

counting means for counting the number of the power supply cycles in the light load mode during the period the output voltage is lower than the predetermined voltage; and

controlling means for switching the operation mode from the light load mode to the heavy load mode when the count value of said counting means reaches a predetermined value.

7. The DC/DC converter as set forth in claim 6, further comprising:

resetting means for resetting said counting means when said voltage comparing means has determined that the output voltage is higher than the predetermined voltage.

8. A DC/DC converter for controlling switching means so as to vary a coil current and control an output, comprising:

first switch controlling means for turning on the switching means when an output voltage decreases to a reference value;

second switch controlling means for turning off the switching means when the coil current increases and exceeds a first threshold value; and

controlling means for controlling said first switch controlling means to prevent said first switch controlling means from controlling the switching means when the coil current decreases to a second threshold value that is smaller than the first threshold value and the output voltage is higher than the reference value.

9. A DC/DC converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, the converter comprising:

an output which is controlled corresponding to each operation mode; and

controlling means for controlling whether the output is at the light load mode or the heavy load mode, wherein the controlling means switches the operation mode at the output from the light load mode to the heavy load mode when a predetermined number of power supply cycles in the light load mode are successively performed.

10. A DC/DC converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, the converter comprising:

an output which is controlled corresponding to each operation mode;

voltage comparing means for comparing an output voltage with a predetermined voltage;

counting means for counting the number of the power supply cycles in the light load mode during the period the output voltage is lower than the predetermined voltage; and

controlling means for switching the operation mode from the light load mode to the heavy load mode when the count value of said counting means reaches a predetermined value.

11. The DC/DC converter as set forth in claim 10, further comprising:

resetting means for resetting said counting means when said voltage comparing means has determined that the output voltage is higher than the predetermined voltage.

12. A DC/DC converter having at least a heavy load mode and a light load mode as operation modes for supplying a current to a load and varying a coil current corresponding to each operation mode so as to control an output,

wherein an operation mode is switched from the heavy load mode to the light load mode when a lowest value of a coil current that varies corresponding to a control in the heavy load mode reaches a predetermined current value for a predetermined number of times.

13. A DC/DC converter having at least a heavy load mode and a light load mode as operation modes for supplying a current to a load and varying a coil current corresponding to each operation mode so as to control an output, comprising:

comparing means for comparing a coil current that varies corresponding to a control in the heavy load mode with a predetermined current value and outputting a detection signal when the coil current reaches the predetermined current value;

counting means for counting the number of times the detection signal is received from said comparing means; and

controlling means for switching an operation mode from the heavy load mode to the light load mode when the count value of said counting means reaches a predetermined value.

14. The DC/DC converter as set forth in claim 13, further comprising:

resetting means for resetting said counting means when the coil current that varies corresponding to a control in the heavy load mode becomes higher than the predetermined current value.

15. A DC/DC converter for controlling a switch so as to vary a coil current and control an output, the converter comprising:

a first monitoring circuit which monitors an output value and outputs a first signal when the output value becomes a reference value;

a second monitoring circuit which monitors the coil current, outputs a second signal when the coil current becomes a first current value, and outputs a third signal when the coil current becomes a second current value; and

a controller which receives the first, second and third signal, wherein the controller turns on the switch when the first signal is received and turns off the switch when the second signal is received,

wherein the controller is adapted for ignoring the first signal after the first signal is received until the third signal is received.

16. A method for controlling a DC/DC converter which controls a switch so as to vary a coil current and control an output, the method comprising:

generating a first signal when an output value becomes a reference value;

generating a second signal when the coil current becomes a first current value;

generating a third signal when the coil current becomes a second current value;

turning on the switch when the first signal is received;

turning off the switch when the second signal is received; and

ignoring the first signal after the first signal is received until the third signal is received.

17. A DC/DC converter for controlling a switch so as to vary a coil current and control an output, the converter comprising:

a first controller which turns on the switch when an output voltage decreases to a reference value;

a second controller which turns off the switch when the coil current increases to a first threshold value;

a third controller which controls the first controller to prevent the first controller from controlling the switch when the coil current decreases to a second threshold value that is smaller than the first threshold value and the output voltage is higher than the reference value.

18. A method for controlling a DC/DC converter which controls a switch so as to vary a coil current and control an output, the method comprising:

turning on the switch when an output voltage decreases to a reference value;

turning off the switch when the coil current increases to a first threshold value; and

preventing the switch from being turned on when the coil current decreases to a second threshold value that is smaller than the first threshold value and the output voltage is higher than the reference value.

19. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, the converter comprising:

an output which is controlled corresponding to each operation mode; and

a controller which controls whether the output is at the light load mode or the heavy load mode, wherein the controller switches the operation mode from the light load mode to the heavy load mode when a predetermined number of power supply cycles in the light load mode are successively performed.

20. A method for controlling a DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, the method comprising:

controlling an output of the converter corresponding to each operation mode; and

switching the operation mode from the light load mode to the heavy load mode when a predetermined number of power supply cycles in the light load mode are successively performed.

21. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, pulse frequency modulation being used in the light load mode, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a detector which detects the number of power supply cycles performed in the light load mode; and

a controller which switches the operation mode from the light load mode to the heavy load mode according to the number of power supply cycles detected by the detector.

23. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a first generator which generates a first control signal used in the light load mode;

a second generator which generates a second control signal used in the heavy load mode;

a switch which supplies or intercepts power to the load according to one of the first and second control signals;

a detector which detects a condition of a coil ripple current; and

a selector which selects one of the first and second control signals to be output to the switch according to the condition detected by the detector.

24. A method for controlling a DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the method comprising:

generating a first control signal used in the light load mode;

generating a second control signal used in the heavy load mode;

detecting a condition of a coil ripple current; and

selecting one of the first and second control signals to be output to a switch, which supplies or intercepts power to the load according to the selected control signal, on the basis of the condition detected by the detector.

25. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a comparator which compares a coil ripple current that varies corresponding to a control in the heavy load mode with a predetermined value; and

a detector which detects a condition that a lowest value of the coil ripple current in a power supply cycle reaches the predetermined value in the heavy load mode,

wherein an operation mode is switched from the heavy load mode to the light load mode when the detector detects the condition for a predetermined number of times.

22. The converter according to claim 26, wherein the controller switches the operation mode only when an output voltage is lower than a predetermined value.

26. The DC/DC switching converter according to claim 25, wherein the predetermined number of times is a natural number equal to or more than one.

27. The DC/DC switching converter according to claim 25, wherein the detector includes a counter.

28. The DC/DC switching converter according to claim 25, wherein the DC/DC switching converter is a synchronous rectifying DC/DC converter.

29. The DC/DC switching converter according to claim 25, wherein the predetermined value is substantially zero.

30. The DC/DC switching converter according to claim 25, wherein pulse width modulation is used in the heavy load mode.

31. The DC/DC switching converter according to claim 25, wherein the converter has a switching frequency and the switching frequency in the light load mode is lower than the switching frequency in the heavy load mode.

32. The DC/DC switching converter according to claim 25, wherein pulse frequency modulation is used in the light load mode.

33. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a comparator which compares a coil ripple current that varies corresponding to a control in the heavy load mode with a predetermined value; and

a detector which detects a lowest value of the coil ripple current in a power supply cycle,

wherein an operation mode is switched from the heavy load mode to the light load mode when the detector detects a condition that the lowest value of the coil ripple current in the heavy load mode reaches the predetermined value at least one time.

34. A DC/DC switching converter having at least a heavy load mode and a light load mode as operation modes for supplying a power to a load, pulse width modulation being used in the heavy load mode, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a detector which detects a lowest value of the coil ripple current in each power supply cycle in the heavy load mode; and

a controller which switches an operation mode from the heavy load mode to the light load mode according to the lowest value detected by the detector.

35. A DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the converter comprising:

a comparing circuit which compares a coil ripple current that varies corresponding to a control in the heavy load mode with a predetermined value; and

a detecting circuit which detects a condition that a lowest value of the coil ripple current in a power supply cycle reaches the predetermined value in the heavy load mode,

wherein an operation mode is switched from the heavy load mode to the light load mode when the detecting circuit detects the condition for a predetermined number of times.

36. A method for controlling a DC/DC switching converter having at least a light load mode and a heavy load mode as operation modes for supplying a power to a load, an output of the DC/DC switching converter being controlled corresponding to each operation mode, the method comprising:

comparing a coil ripple current that varies corresponding to a control in the heavy load mode with a predetermined value;

detecting a condition that a lowest value of the coil ripple current in a power supply cycle reaches the predetermined value in the heavy load mode; and

switching an operation mode from the heavy load mode to the light load mode when the condition is detected for a predetermined number of times.