SEMICONDUCTOR INTEGRATED CIRCUIT AND POWER SUPPLY DEVICE

• US 20100213911A1
• Filed: 02/23/2010
• Published: 08/26/2010
• Est. Priority Date: 02/24/2009
• Status: Active Grant

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Microelectronics Limited (Fujitsu Limited)
• Inventors: OKI, Hideta
• Granted Patent: US 8,698,467 B2
• Time in Patent Office: Days
• US Class Current: 323/283
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

A semiconductor integrated circuit includes: a first switching element and a second switching element that are provided in series between a first power line and a second power line; a power supply circuit that outputs a given output voltage by on/off controlling the first switching element and the second switch element; a current detection circuit that detects a current corresponding to an output load current of the power supply circuit; a switching time control circuit that controls a switching time defined by a power supply voltage and the output voltage based on a current value detected by the current detection circuit; and a switching element control circuit that controls the first switching element and the second switching element based on an output signal of the switching time control circuit.

Claims

1. A semiconductor integrated circuit comprising:

a first switching element and a second switching element that are provided in series between a first power line and a second power line;

a power supply circuit that outputs a given output voltage by on/off controlling the first switching element and the second switch element;

a current detection circuit that detects a current corresponding to an output load current of the power supply circuit;

a switching time control circuit that controls a switching time defined by a power supply voltage and the output voltage based on a current value detected by the current detection circuit; and

a switching element control circuit that controls the first switching element and the second switching element based on an output signal of the switching time control circuit.

2. The semiconductor integrated circuit according to claim 1, wherein the power supply circuit comprises:

a coil that applies a current from the first switching element and the second switching element to an output terminal via a connection node; and

a smoothing capacitor that is provided between the output terminal and the second power line.

3. The semiconductor integrated circuit according to claim 2, wherein the current detection circuit is provided between the first switching element and the connection node.

4. The semiconductor integrated circuit according to claim 2, wherein the current detection circuit is provided between the first power line and the first switching element.

5. The semiconductor integrated circuit according to claim 2, wherein the current detection circuit is provided between the coil and the output terminal.

6. The semiconductor integrated circuit according to claim 2, wherein the current detection circuit is provided between the connection node and the coil.

7. The semiconductor integrated circuit according to claim 1, wherein the switching time control circuit includes:

a first comparator that compares a first voltage signal based on the power supply voltage and a second voltage signal obtained by adding a reference signal based on the output voltage and a signal based on the current value detected by the current detection circuit.

8. The semiconductor integrated circuit according to claim 1, wherein the switching time control circuit controls an on time of the first switching element.

9. The semiconductor integrated circuit according to claim 1, further comprising:

an error comparator that compares the output voltage with a reference voltage; and

a reference voltage generator that generates the reference voltage.

10. The semiconductor integrated circuit according to claim 9, wherein the power supply circuit controls the output voltage by using a ripple superimposed onto the output voltage by a parasitic resistance of the smoothing capacitor or by a resistor that is provided in series with the smoothing capacitor between the output terminal and the second power line;

and

the reference voltage generator generates the reference voltage in a fixed manner.

11. The semiconductor integrated circuit according to claim 9, wherein the output voltage is superimposed with a ripple by a high-pass filter that includes the coil and is supplied to the error comparator;

and

the reference voltage generator generates the reference voltage in a fixed manner.

12. The semiconductor integrated circuit according to claim 9, wherein the reference voltage generator generates the reference voltage onto which a ripple is superimposed.

13. The semiconductor integrated circuit according to claim 9, further comprising:

a ripple current detection circuit that is provided between the second power line and the second switching element.

14. The semiconductor integrated circuit according to claim 13, wherein the reference voltage generator generates the reference voltage to which a ripple is superimposed by adding a fixed voltage and an output voltage of the ripple current detection circuit.

15. The semiconductor integrated circuit according to claim 1, further comprising:

a ripple current detection circuit that is provided between the second power line and the second switching element;

an error amplifier that compares the output voltage with a reference voltage; and

a second comparator that compares an output signal of the error amplifier with an output signal of the ripple current detection circuit.

16. The semiconductor integrated circuit according to claim 15, wherein an operation of the current detection circuit is stopped if the output load current is small compared to an output of the ripple current detection circuit.

17. The semiconductor integrated circuit according to claim 1, wherein the semiconductor integrated circuit includes the first switching element and the second switching element.

18. The semiconductor integrated circuit according to claim 1, wherein the power supply circuit includes a plurality of modes;

and

the semiconductor integrated circuit further comprising;

a third switching element and a fourth switching element that are provided in series between the first power line and the second power line; and

a mode control circuit that sets at least one of the plurality of modes; and

wherein the output terminal is coupled to the connection node through the third switching element and the coil.

19. The semiconductor integrated circuit according to claim 18, wherein the plurality of modes includes a buck mode, a boost mode, and a buck-boost.

20. A power supply device comprising:

a semiconductor integrated circuit that includes;

a first switching element and a second switching element that are provided in series between a first power line and a second power line;

a power supply circuit that outputs a given output voltage by on/off controlling the first switching element and the second switching element;

a current detection circuit that detects a current corresponding to an output load current of the power supply circuit;

a switching time control circuit that controls a switching time defined by a power supply voltage and the output voltage based on a current value detected by the current detection circuit;

a switching element control circuit that controls the first switching element and the second switching element based on an output signal of the switching time control circuit;

a coil that applies a current from the first switching element and the second switching element to an output terminal through a connection node; and

a smoothing capacitor that is provided between the output terminal and the second power line.