CURRENT DETECTION CIRCUIT AND DCDC CONVERTER INCLUDING THE SAME

• US 20170279357A1
• Filed: 03/17/2017
• Published: 09/28/2017
• Est. Priority Date: 03/23/2016
• Status: Active Application

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Renesas Electronics Corporation
• Inventors: TAJIMA, Hideyuki
• Granted Patent: US 10,256,725 B2
• Time in Patent Office: Days
• CPC Class Codes: G01R 15/146 Measuring arrangements for current not covered by other subgroups of G01R15/14, e.g. using current dividers, shunts, or measuring a voltage drop if no voltage isolation is involved G01R1/203 or G01R19/0092
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/15 using active elements
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

According to an embodiment, a current detection circuit includes a transistor, an operational amplifier, and a transistor. In the transistor, the source and the gate are coupled to the source and the gate of a transistor which is provided on a high side of a drive circuit. The operational amplifier amplifies a potential difference between a drain voltage of the transistor and a drain voltage of the transistor. The transistor is provided over a current path through which a current flowing to the transistor flows, and which has the gate to which an output voltage of the operational amplifier is supplied. A value of the current flowing Through The transistor is detected based on a value of the current flowing through the transistor.

Claims

1. A current detection circuit comprising:

a first sense transistor which includes a first terminal and a control terminal which are coupled respectively to a first terminal provided on an external output terminal side outputting externally an output voltage of the drive circuit and a control terminal, of terminals of a first drive transistor provided on a high side of a drive circuit, the first sense transistor being a same conductive type as the first drive transistor;

a first operational amplifier which amplifies a potential difference between a voltage of a second terminal provided on an external input terminal side to which an input voltage is supplied externally from the drive circuit and a voltage of a second terminal of the first sense transistor, of the terminals of the first drive transistor; and

a first current control transistor which is provided over a first current path through which a current from the first sense transistor flows, and which has a control terminal to which an output voltage of the first operational amplifier is supplied,

wherein a value of a current flowing through the first drive transistor is detected from a value of the current flowing through the first sense transistor.

2. The current detection circuit according to claim 1,

wherein the first operational amplifier operates, when the input voltage of the drive circuit is supplied as a low potential side source voltage, and when a first voltage higher than the input voltage is supplied as a high potential side source voltage

3. The current detection circuit according to claim 2,

wherein a differential voltage between the first voltage and the input voltage is equal to or lower than a withstand voltage of the transistor included in the first operational amplifier.

4. The current detection circuit according to claim 3, further comprising

a regulator which generates the first voltage.

5. The current detection circuit according to claim 1,

wherein there is provided a third current path, which discharges a current flowing from the first terminal to the second terminal of the first sense transistor, independently from the first current path.

6. The current detection circuit according to claim 1, further comprising

a first constant current source which is provided between the second terminal of the first sense transistor and a ground voltage terminal.

7. The current detection circuit according to claim 1, further comprising:

a first resistance element which is provided between one input terminal and other input terminal of the first operational amplifier; and

a first switch element which is coupled in series with the first resistance element, and controlled to be turned ON/OFF complementarily with the first sense transistor.

8. The current detection circuit according to claim 7,

wherein a resistance value of the first resistance element is approximately same as a resistance value when the first sense transistor is turned ON.

10. The current detection circuit according to claim 1,

wherein the drive circuit further has

a second drive transistor which is provided on a low side, and controlled to be turned ON/OFF based on a dead time existing therebetween complementarily with the first drive transistor, and

an inductor which is provided between the first and second drive transistors and the external output terminal,

wherein the current detection circuit further includes

a second sense transistor which includes a second terminal and a control terminal which are coupled respectively to a second terminal provided on the external output terminal side and a control terminal, of terminals of the second drive transistor, and which is same conductive type as the second drive transistor,

a second operational amplifier which amplifies a potential difference between a voltage of a first terminal provided on a ground voltage terminal side and a voltage of a first terminal of the second sense transistor, of the terminals of the second drive transistor, and

a second current control transistor which is provided over a second current path through which a current flowing through the second sense transistor flows, and which has a control terminal to which an output voltage of the second operational amplifier is supplied, and

wherein a current flowing through the inductor is detected based on a value of a current flowing through each of the first and second sense transistors.

11. The current detection circuit according to claim, 10, further comprising

a voltage supply unit which supplies a voltage, higher than a ground voltage supplied to the ground voltage terminal by a predetermined voltage, to one input terminal coupled to the ground voltage terminal together with the first terminal of the second drive transistor, of two input terminals of the second operational amplifier.

12. The current detection circuit according to claim 10, further comprising:

a second resistance element which is provided between one input terminal coupled to the ground voltage terminal together with the first terminal of the second drive transistor, of two input terminals of the second operational amplifier, and the ground voltage terminal; and

a second constant current source which supplies a current between the second resistance element and the one input terminal of the second operational amplifier.

13. The current detection circuit according to claim 12,

wherein the second resistance element is a transistor, in an ON state, being a same conductive type and having a same size as the second sense transistor.

14. The current detection circuit according to claim 10, further comprising

a switch transistor which is provided between one input terminal of the second operational amplifier and other input terminal thereof, and which is controlled to be turned ON/OFF complementarily with the second sense transistor.

9. A DCDC converter comprising:

a drive circuit;

a current detection circuit which detects a value of a current flowing through a first drive transistor;

a first comparator which compares a detection result of the current detection circuit and a reference voltage; and

a pulse signal generation unit which generates a pulse signal of a duty ratio in accordance with a comparison result of the first comparator,

wherein the drive circuit has

a second drive transistor which is provided on a low side, and which is controlled to be turned ON/OFF based on a dead time existing therebetween complementarily with the first drive transistor in accordance with a pulse signal, and

an inductor which is provided between the first and second drive transistors and the external output terminal.

15. A DCDC converter comprising:

a drive circuit;

a current detection circuit which detects a value of a current flowing through an inductor;

an error amplifier which amplifies a difference between a detection result of the current detection circuit and a reference voltage; and

a pulse signal generation circuit which generates a first and second pulse signals of a duty ratio in accordance with an output result of the error amplifier,

wherein the drive circuit has

the inductor,

a first drive transistor which controls a current flowing from an external input terminal to an external output terminal through the inductor, by being controlled to be turned ON/OFF based on a first pulse signal, during voltage step down,

a second drive transistor which controls a current flowing from a ground voltage terminal to the external output terminal through the inductor, by being controlled to be turned ON/OFF based on a dead time existing therebetween complementarily with the first drive transistor, during the voltage step down,

a third drive transistor which controls a current flowing from the external input terminal to the ground voltage terminal through the inductor, by being controlled to be turned ON/OFF based on a second pulse signal, during voltage step up, and

a fourth drive transistor which controls a current flowing from the external input terminal to the external output terminal through the inductor, by being controlled to be turned ON/OFF based on a dead time existing therebetween complementarily with the third drive transistor, during voltage step up.

16. A current detection circuit comprising:

an N-channel first sense transistor having a source and a gate which are coupled respectively to a source and a gate of an N-channel first drive transistor provided on a high side of a drive circuit;

a first operational amplifier which amplifies a potential difference between a drain voltage of the first drive transistor and a drain voltage of the first sense transistor; and

a first current control transistor which is provided over a first current path through which a current flowing through the first sense transistor flows, and which has a gate to which an output voltage of the first operational amplifier is supplied, and

wherein a value of a current flowing through the first drive transistor is detected based on a value of the current flowing through the first sense transistor.

17. The current detection circuit according to claim 16,

wherein the first operational amplifier operates, when an input voltage of the drive circuit is supplied as a low potential side source voltage, and when a first voltage higher than the input voltage is supplied as a high potential side source voltage.

18. The current detection circuit according to claim 16,

wherein the drive circuit further has

a second drive transistor which is provided on a low side, and is controlled to he turned ON/OFF based on a dead time exiting therebetween complementarily with the first drive transistor, and

an inductor which is provided between the first and second drive transistors and an external output terminal,

wherein the current detection circuit further includes

an N-channel second sense transistor having a drain and a gate which are coupled respectively to a drain and a gate of the second drive transistor,

a second operational amplifier which amplifies a potential difference between a source voltage of the second drive transistor and a source voltage of the second sense transistor, and

a second current control transistor which is provided over a second current path through which a current flowing through the second transistor flows, and which has a gate to which an output voltage of the second operational amplifier is supplied, and

wherein a current flowing through the inductor is detected from a value of a current flowing through each of the first and second sense transistors.