Method and system for controlling HS-NMOS power switches with slew-rate limitation

• US 8,564,359 B2
• Filed: 09/14/2010
• Issued: 10/22/2013
• Est. Priority Date: 09/07/2010
• Status: Active Grant

• Current Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Brauer, Michael, Drebinger, Stephan
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): Cole, Brandon S
• Application Number:
  US12/807,769
• Publication Number:
  US 20120056655A1
• Time in Patent Office: 1,134 Days
• Field of Search: 327365-508
• US Class Current: 327/427
• CPC Class Codes: H03K 17/166 Soft switching
• CPC Class Codes: H03K 2017/6875 using self-conductive, depletion FETs
• CPC Class Codes: H03K 2217/0054 Gating switches, e.g. pass gates
• 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 5/01 Shaping pulses discrimination against noise or interference H03K5/125

Abstract

A method and system for limiting the slew rate of the output voltage of one or more high side (HS) NMOS power switches is disclosed. A circuit arrangement configured to control a first NMOS switch is described. The arrangement comprises voltage provisioning means configured to supply a gate voltage to a gate terminal of the first NMOS switch; current provisioning means configured to provide a current; a first control stage configured to provide and/or remove a connection between the gate terminal of the first NMOS switch and the voltage provisioning means, thereby switching the first NMOS switch to an on-state and/or an off-state, respectively; and a first feedback control link between an output terminal of the first NMOS switch and the current provisioning means configured to control the slew-rate of a voltage at the first output terminal.

Claims

1. A circuit arrangement configured to control a first NMOS switch, the arrangement comprising:

voltage provisioning means configured to supply a gate voltage to a gate terminal of the first NMOS switch;

current provisioning means configured to provide a current;

a first control stage configured to provide and/or remove a connection between the gate terminal of the first NMOS switch and the voltage provisioning means, thereby switching the first NMOS switch to an on-state and/or an off-state, respectively; and

a first feedback control link coupling an output terminal of the first NMOS switch with the current provisioning means, wherein the current provisioning means are configured to control the slew-rate of a voltage at the output terminal using the current provided by the current provisioning means;

wherein the current provided by the current provisioning means or an amplified version thereof is equal to a current at the output of the first feedback control link.

2. The circuit arrangement of claim 1 wherein the first feedback control link comprises a first capacitor C1.

3. The circuit arrangement of claim 2, wherein the first feedback control link further comprises first feedback amplification means configured to map a current through the first capacitor C1 at an input of the first feedback amplification means to a current at an output of the first feedback amplification means coupled to the current provisioning means.

4. The circuit arrangement of claim 3, wherein

the current at the output of the first feedback amplification means is proportional to the current provided by the current provisioning means;

the slew rate of the output voltage

5. The circuit arrangement of claim 4, wherein

the first feedback amplification means is a first current mirror;

the first current mirror comprises an input transistor and an output transistor; and

the gain value

6. The circuit arrangement of claim 5, further comprising current biasing means configured to provide bias currents to the input transistor and the output transistor of the first current mirror.

7. The circuit arrangement of claim 6, wherein the current biasing means comprise

first bias amplification means configured to amplify the current of a biasing current source and to provide the current amplified by the first bias amplification means to the input transistor of the first current mirror;

and

second bias amplification means configured to amplify the current of the biasing current source and to provide the current amplified by the second bias amplification means to the output transistor of the first current mirror.

8. The circuit arrangement of claim 7, wherein the ratio of the current amplified by the second bias amplification means and the current amplified by the first bias amplification means corresponds to the gain value k₁.

9. The circuit arrangement of claim 5, further comprising a source follower, wherein an output terminal of the source follower is connected to a common gate terminal of the input transistor and the output transistor of the first current mirror.

10. The circuit arrangement of claim 9, further comprising a current source for the source follower, wherein the current source for the source follower (510) provides a current to a source terminal of the source follower.

11. The circuit arrangement of claim 1, wherein the first control stage comprises

a pull transistor configured to couple the gate terminal of the first NMOS switch to the voltage provisioning means when the pull transistor is switched on;

and

a push transistor configured to couple the gate terminal of the first NMOS switch to a low voltage point when the push transistor is switched on.

12. The circuit arrangement of claim 1, configured to control a second NMOS switch, further comprising:

a second control stage configured to provide and/or remove a connection between a gate terminal of the second NMOS switch and the voltage provisioning means, thereby switching the second NMOS switch to an on-state and/or an off-state, respectively; and

a second feedback control link between an output terminal of the second NMOS switch and the current provisioning means configured to control the slew-rate of a voltage at the output terminal of the second NMOS switch.

13. The circuit arrangement of claim 1, further comprising current amplification means configured to amplify the current provided by the current provisioning means and to provide the current amplified by current amplification means to the first feedback control link.

14. The circuit arrangement of claim 13, wherein the current amplification means corresponds to a current mirror.

15. The circuit arrangement of claim 1 wherein the voltage provisioning means and the current provisioning means are implemented as a common charge pump and wherein the first feedback control link is coupled to the gate terminal.

16. The circuit arrangement of claim 1, further comprising

a comparing portion configured to monitor the voltage at the gate terminal of the first NMOS switch and configured to detect that the voltage at the gate terminal of the first NMOS switch exceeds a voltage threshold value;

and

a mode switching portion configured to disconnect the current provisioning means from the first feedback control link and configured to provide a connection between the gate terminal of the first NMOS switch and the voltage provisioning means, if the voltage at the gate terminal of the first NMOS switch exceeds the voltage threshold value.

17. The circuit arrangement of claim 16, wherein the comparing portion comprises one or more transistors and a current sink.

18. The circuit arrangement of any of claim 16, wherein the mode switching portion comprises a transistor P4 configured to provide the connection between the gate terminal of the first NMOS switch and the voltage provisioning means.

19. The circuit arrangement of claim 16, wherein the mode switching portion comprises at least one of a Schmitt trigger, a D-Flip-Flop and an AND gate.

20. The circuit arrangement of claim 1, wherein the NMOS switch is a high side NMOS power switch.