DC-DC CONVERTER AND SEMICONDUCTOR INTEGRATED CIRCUIT

• US 20150069988A1
• Filed: 02/19/2014
• Published: 03/12/2015
• Est. Priority Date: 09/12/2013
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kimura, Hideki, Ikeda, Sadao, Miura, Tsukasa
• Granted Patent: US 9,209,686 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

The DC-DC converter includes a mask controlling circuit that outputs an overcurrent detection mask signal that prescribes a mask period in which the overcurrent detection result signal is masked. The DC-DC converter includes a mask adjusting circuit that adjusts a length of the mask period according to the power supply voltage. The DC-DC converter includes an operation circuit that performs an operation of the overcurrent detection result signal and the overcurrent detection mask signal and outputs an overcurrent controlling signal with the overcurrent detection result signal being masked in the mask period.

Claims

1. A DC-DC converter that outputs, at an output terminal, an output voltage obtained by stepping down or boosting a power supply voltage, comprising:

a switch element that controls supply of a current to the output terminal;

an overcurrent detecting circuit that compares a detected voltage responsive to a current flowing through the switch element and a reference voltage and outputs an overcurrent detection result signal responsive to a result of the comparison;

a mask controlling circuit that outputs an overcurrent detection mask signal that prescribes a mask period in which the overcurrent detection result signal is masked;

a mask adjusting circuit that adjusts a length of the mask period according to the power supply voltage;

an operation circuit that performs an operation of the overcurrent detection result signal and the overcurrent detection mask signal and outputs an overcurrent controlling signal with the overcurrent detection result signal being masked in the mask period; and

an output controlling circuit that performs PWM control on the switch element in such a manner that a feedback signal that is based on the output voltage comes closer to a target value, and forcedly turns off the switch element based on the overcurrent controlling signal.

2. The DC-DC converter according to claim 1, wherein the mask adjusting circuit adjusts the mask period to a first mask period in a case where the power supply voltage is equal to or higher than a switching threshold, and adjusts the mask period to a second mask period, which is longer than the first mask period, in a case where the power supply voltage is lower than the switching threshold.

3. The DC-DC converter according to claim 1, wherein the output controlling circuit

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the mask period.

4. The DC-DC converter according to claim 2, wherein the output controlling circuit

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the first mask period in the case where the power supply voltage is equal to or higher than the switching threshold, and

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the second mask period in the case where the power supply voltage is lower than the switching threshold.

5. The DC-DC converter according to claim 1, wherein the mask period starts when the switch element is turned on.

6. The DC-DC converter according to claim 5, wherein the mask period is shorter than a period in which the switch element is continuously in an on state.

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

a first converting circuit that detects a potential difference between a first end and a second end of a current path of the switch element, converts the potential difference into a detected current, and outputs the detected current; and

a second converting circuit that converts the detected current into the detected voltage and outputs the detected voltage.

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

an input terminal to which a first end of a current path of the switch element is connected and the power supply voltage is supplied;

a control terminal to which a second end of the current path of the switch element is connected;

a feedback terminal to which the feedback signal is supplied;

a coil connected between the output terminal and the control terminal;

a capacitor connected between the output terminal and a ground;

a diode connected to the control terminal at a cathode thereof and to the ground thereof at an anode thereof; and

a voltage dividing circuit that is connected between the output terminal and the ground and outputs a voltage obtained by dividing the output terminal as the feedback signal,

wherein the output voltage obtained by stepping down the power supply voltage is output at the output terminal.

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

a coil that receives the power supply terminal at a first end thereof;

a diode connected to a second end of the coil at an anode thereof and to the output terminal at a cathode thereof;

a capacitor connected between the output terminal and a ground;

an input terminal to which the second end of the coil is connected, the switch element being connected between the input terminal and the ground;

a feedback terminal to which the feedback signal is supplied; and

a voltage dividing circuit that is connected between the output terminal and the ground and outputs a voltage obtained by dividing the output terminal as the feedback signal, wherein the output voltage obtained by boosting the power supply voltage is output at the output terminal.

10. The DC-DC converter according to claim 1, wherein the operation circuit is a NOR circuit that receives the overcurrent detection result signal and the overcurrent detection mask signal and outputs the overcurrent controlling signal.

11. A semiconductor integrated circuit that is incorporated in a DC-DC converter that outputs, at an output terminal, an output voltage obtained by stepping down or boosting a power supply voltage, comprising:

a switch element that controls supply of a current to the output terminal;

an overcurrent detecting circuit that compares a detected voltage responsive to a current flowing through the switch element and a reference voltage and outputs an overcurrent detection result signal responsive to a result of the comparison;

a mask controlling circuit that outputs an overcurrent detection mask signal that prescribes a mask period in which the overcurrent detection result signal is masked;

a mask adjusting circuit that adjusts a length of the mask period according to the power supply voltage;

an operation circuit that performs an operation of the overcurrent detection result signal and the overcurrent detection mask signal and outputs an overcurrent controlling signal with the overcurrent detection result signal being masked in the mask period; and

an output controlling circuit that performs PWM control on the switch element in such a manner that a feedback signal that is based on the output voltage comes closer to a target value, and forcedly turns off the switch element based on the overcurrent controlling signal.

12. The semiconductor integrated circuit according to claim 11, wherein the mask adjusting circuit adjusts the mask period to a first mask period in a case where the power supply voltage is equal to or higher than a switching threshold, and adjusts the mask period to a second mask period, which is longer than the first mask period, in a case where the power supply voltage is lower than the switching threshold.

13. The semiconductor integrated circuit according to claim 11, wherein the output controlling circuit

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the mask period.

14. The semiconductor integrated circuit according to claim 11, wherein the output controlling circuit

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the first mask period in the case where the power supply voltage is equal to or higher than the switching threshold, and

forcedly turns off the switch element in a case where the detected voltage is equal to or higher than the reference voltage in a period except for the second mask period in the case where the power supply voltage is lower than the switching threshold.

15. The semiconductor integrated circuit according to claim 11, wherein the mask period starts when the switch element is turned on.

16. The semiconductor integrated circuit according to claim 15, wherein the mask period is shorter than a period in which the switch element is continuously in an on state.

17. The semiconductor integrated circuit according to claim 11, further comprising:

a first converting circuit that detects a potential difference between a first end and a second end of a current path of the switch element, converts the potential difference into a detected current, and outputs the detected current; and

a second converting circuit that converts the detected current into the detected voltage and outputs the detected voltage.

18. The semiconductor integrated circuit according to claim 11, further comprising:

an input terminal to which a first end of a current path of the switch element is connected and the power supply voltage is supplied;

a control terminal to which a second end of the current path of the switch element is connected;

a feedback terminal to which the feedback signal is supplied;

a coil connected between the output terminal and the control terminal;

a capacitor connected between the output terminal and a ground;

a diode connected to the control terminal at a cathode thereof and to the ground thereof at an anode thereof; and

a voltage dividing circuit that is connected between the output terminal and the ground and outputs a voltage obtained by dividing the output terminal as the feedback signal,

wherein the output voltage obtained by stepping down the power supply voltage is output at the output terminal.

19. The semiconductor integrated circuit according to claim 11, further comprising:

a coil that receives the power supply terminal at a first end thereof;

a diode connected to a second end of the coil at an anode thereof and to the output terminal at a cathode thereof;

a capacitor connected between the output terminal and a ground;

an input terminal to which the second end of the coil is connected, the switch element being connected between the input terminal and the ground;

a feedback terminal to which the feedback signal is supplied; and

a voltage dividing circuit that is connected between the output terminal and the ground and outputs a voltage obtained by dividing the output terminal as the feedback signal,

wherein the output voltage obtained by boosting the power supply voltage is output at the output terminal.

20. The semiconductor integrated circuit according to claim 11, wherein the operation circuit is a NOR circuit that receives the overcurrent detection result signal and the overcurrent detection mask signal and outputs the overcurrent controlling signal.