CHARGE AND DISCHARGE SIGNAL CIRCUIT AND DC-DC CONVERTER

• US 20140306674A1
• Filed: 03/28/2014
• Published: 10/16/2014
• Est. Priority Date: 04/10/2013
• Status: Active Grant

• Current Assignee: Fujitsu Semiconductor Limited (Fujitsu Limited)
• Original Assignee: Fujitsu Limited, Fujitsu Semiconductor Limited (Fujitsu Limited)
• Inventors: KONDOU, Masafumi, Takekawa, Koji
• Granted Patent: US 9,337,732 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H03K 17/102 in field-effect transistor switches
• CPC Class Codes: H03K 2217/0063 High side switches, i.e. the higher potential [DC] or life wire [AC] being directly connected to the switch and not via the load
• CPC Class Codes: H03K 2217/0081 Power supply means, e.g. to the switch driver

Abstract

A charge and discharge signal circuit includes: high side transistors connected in series; low side transistors connected in series; high side drive circuits; low side drive circuits; and a drive signal generation circuit, wherein each drive circuit includes: a high side level shifter; a high side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the high side transistor; and a high side drive part, to which an output of the high side level shifter is supplied, and each of the low side drive circuits includes: a low side level shifter; a low side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the low side transistor; and a low side drive part, to which an output of the low side level shifter is supplied.

Claims

1. A charge and discharge signal circuit comprising:

a plurality of high side transistors connected in series between a high potential side power source and an output node;

a plurality of low side transistors connected in series between a low potential side power source and the output node;

a plurality of high side drive circuits provided respectively in correspondence to the plurality of high side transistors;

a plurality of low side drive circuits provided respectively in correspondence to the plurality of low side transistors; and

a drive signal generation circuit configured to output a drive signal, wherein

each of the high side drive circuits includes;

a high side level shifter configured to convert a level of the drive signal;

a high side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the high side transistor; and

a high side drive part connected between a source of the high side transistor and a connection node of the capacitor and the switch element of the high side capacitor switch string, to which an output of the high side level shifter is supplied, and which outputs a drive signal to the high side transistor, and

each of the low side drive circuits includes;

a low side level shifter configured to convert a level of the drive signal;

a low side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the low side transistor; and

a low side drive part connected between a source of the low side transistor and a connection node of the capacitor and the switch element of the low side capacitor switch string, to which an output of the low side level shifter is supplied, and which outputs a drive signal to the low side transistor.

2. The charge and discharge signal circuit according to claim 1, wherein

when a high level is output from the output node:

the switch element of the high side capacitor switch string of each of the high side drive circuits turns off and by a voltage charged in the capacitor, the plurality of high side drive parts drives the plurality of high side transistors to turn on; and

the capacitor of the low side capacitor switch string of each of the low side drive circuits is charged and by a voltage, which is a voltage between the output node and the low potential side power source divided by the plurality of low side capacitor switch strings, the plurality of low side drive parts drives the plurality of low side transistors to turn off, and

when a low level is output from the output node;

the capacitor of the high side capacitor switch string of each of the high side drive circuits is charged and by a voltage, which is a voltage between the output node and the low potential side power source divided by the plurality of high side capacitor switch strings, the plurality of high side drive parts drives the plurality of high side transistors to turn off; and

the switch element of the low side capacitor switch string of each of the low side drive circuits turns off and by a voltage charged in the capacitor, the plurality of low side drive parts drives the plurality of low side transistors to turn on.

3. The charge and discharge signal circuit according to claim 1, wherein the switch element is a diode.

4. The charge and discharge signal circuit according to claim 2, wherein the switch element is a diode.

5. The charge and discharge signal circuit according to claim 1, wherein the switch element is a transistor to the gate of which an output of the high side drive part is applied, and which turns off when the high side transistor turns on, and which turns on when the high side transistor turns off.

6. The charge and discharge signal circuit according to claim 2, wherein the switch element is a transistor to the gate of which an output of the high side drive part is applied, and which turns off when the high side transistor turns on, and which turns on when the high side transistor turns off.

7. The charge and discharge signal circuit according to claim 1, wherein

each of the high side drive circuits has a high side diode string including a plurality of diodes connected in series and connected in parallel with the high side capacitor switch string or the capacitor, and

each of the low side drive circuits has a low side diode string including a plurality of diodes connected in series and connected in parallel with the low side capacitor switch string or the capacitor.

8. The charge and discharge signal circuit according to claim 2, wherein

each of the high side drive circuits has a high side diode string including a plurality of diodes connected in series and connected in parallel with the high side capacitor switch string or the capacitor, and

each of the low side drive circuits has a low side diode string including a plurality of diodes connected in series and connected in parallel with the low side capacitor switch string or the capacitor.

9. The charge and discharge signal circuit according to claim 3, wherein

each of the high side drive circuits has a high side diode string including a plurality of diodes connected in series and connected in parallel with the high side capacitor switch string or the capacitor, and

each of the low side drive circuits has a low side diode string including a plurality of diodes connected in series and connected in parallel with the low side capacitor switch string or the capacitor.

10. The charge and discharge signal circuit according to claim 5, wherein

each of the high side drive circuits has a high side diode string including a plurality of diodes connected in series and connected in parallel with the high side capacitor switch string or the capacitor, and

each of the low side drive circuits has a low side diode string including a plurality of diodes connected in series and connected in parallel with the low side capacitor switch string or the capacitor.

11. The charge and discharge signal circuit according to claim 1, wherein

the high side transistor is a PMOS transistor, and

the low side transistor is an NMOS transistor.

12. The charge and discharge signal circuit according to claim 1, wherein

the high side transistor and the low side transistor are NMOS transistors.

13. The charge and discharge signal circuit according to claim 11, comprising:

a high side charge circuit configured to charge at all times the capacitor of the high side drive circuit connected to the high potential side power source;

a low side charge circuit configured to charge at all times the capacitor of the low side drive circuit connected to the low potential side power source;

at least one charge PMOS transistor connected between the connection node of the capacitor and the switch element of the high side capacitor switch string of the neighboring high side drive circuit and that of the other neighboring high side drive circuit, and to the gate of which, the output of the high side drive part on the side more distant from the high potential side power source of the neighboring high side drive circuit is applied; and

at least one charge NMOS transistor connected between the connection node of the capacitor and the switch element of the low side capacitor switch string of the neighboring low side drive circuit and that of the other neighboring low side drive circuit, and to the gate of which, the output of the low side drive part on the side more distant from the low potential side power source of the neighboring low side drive circuit is applied.

14. The charge and discharge signal circuit according to claim 13, comprising a power source voltage detection circuit configured to detect that the voltage of the high potential side power source is lower than a predetermined voltage, wherein

in the case where the voltage of the high potential side power source is lower than a predetermined voltage, the high side transistor connected to the high potential side power source, the low side transistor connected to the low potential side power source, the charge PMOS transistor connected to the high side drive circuit connected to the high potential side power source, and the charge NMOS transistor connected to the low side drive circuit connected to the low potential side power source are maintained in the on state.

15. The charge and discharge signal circuit according to claim 12, comprising:

a low side charge circuit configured to charge at all times the capacitor of the low side drive circuit connected to the low potential side power source; and

at least three charge NMOS transistors connected between the connection node of the capacitor and the switch element of the high side capacitor switch string of the neighboring high side drive circuit and/or of the low side capacitor switch string of the neighboring low side drive circuit and that of the high side capacitor switch string of the other neighboring high side drive circuit and/or of the low side capacitor switch string of the neighboring low side drive circuit, and to the gates of which, the output of the high side drive circuit on the side more distant from the low potential side power source of the neighboring high side drive circuit or the output of the low side drive part on the side more distant from the low potential side power source of the neighboring low side drive circuit is applied.

16. A DC-DC converter comprising:

a capacitor one terminal of which is connected to a ground;

an inductor one terminal of which is connected to the other terminal of the capacitor; and

a charge and discharge signal circuit configured to output an alternating-current signal to be applied to the other terminal of the inductor, wherein

the charge and discharge signal circuit comprising;

a plurality of high side transistors connected in series between a high potential side power source and an output node;

a plurality of low side transistors connected in series between a low potential side power source and the output node;

a plurality of high side drive circuits provided respectively in correspondence to the plurality of high side transistors;

a plurality of low side drive circuits provided respectively in correspondence to the plurality of low side transistors; and

a drive signal generation circuit configured to output a drive signal, wherein

each of the high side drive circuits includes;

a high side level shifter configured to convert a level of the drive signal;

a high side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the high side transistor; and

a high side drive part connected between a source of the high side transistor and a connection node of the capacitor and the switch element of the high side capacitor switch string, to which an output of the high side level shifter is supplied, and which outputs a drive signal to the high side transistor, and

each of the low side drive circuits includes;

a low side level shifter configured to convert a level of the drive signal;

a low side capacitor switch string of a capacitor and a switch element connected in series, being connected in parallel with the low side transistor; and

a low side drive part connected between a source of the low side transistor and a connection node of the capacitor and the switch element of the low side capacitor switch string, to which an output of the low side level shifter is supplied, and which outputs a drive signal to the low side transistor.

17. The DC-DC converter according to claim 16, wherein

the drive signal generation circuit outputs a PWM signal.