Digital dead-time controller for pulse width modulators

• US 7,554,372 B1
• Filed: 08/14/2005
• Issued: 06/30/2009
• Est. Priority Date: 08/14/2005
• Status: Active Grant

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Wong, Hee
• Primary Examiner(s): Luu; An T
• Application Number:
  US11/204,284
• Time in Patent Office: 1,416 Days
• Field of Search: None
• US Class Current: 327/172
• CPC Class Codes: H02M 1/385 with means for correcting output voltage deviations introduced by the dead time
• CPC Class Codes: H02M 3/157 with digital control
• CPC Class Codes: H03K 5/1515 non-overlapping

Abstract

Dead-time gaps are inserted into one of two output transistor control signals from a digital pulse width modulator by controlling the leading and trailing edges using the same phase-division and dithering signals employed by the digital pulse width modulator. Adders add the phase select signals from the digital pulse width modulator and the dithering signal to the leading and trailing edge control signals, with the output employed by multiplexers as select controls in selecting a phase of from the phase-shifted versions of the system clock with which to clock latches controlling the leading and trailing edges.

Claims

1. A digital dead-time controller comprising:

a controller receiving a system clock and each of a plurality of phase-shifted versions of the system clock employed by a digital pulse width modulator, the controller further comprising;

first logic causing a duration of an output transistor control signal controlling a first output transistor driving an output node to be increased by a first selected multiple of phase-divisions of the system clock; and

second logic causing a leading edge of the output transistor control signal to be advanced relative to the system clock by a second selected multiple of phase-divisions of the system clock.

2. The digital dead-time controller according to claim 1, wherein the first logic causes a trailing edge of the output transistor control signal to be delayed relative to the system clock.

3. The digital dead-time controller according to claim 2, wherein a second output transistor control signal controlling a second output transistor driving the output node remains synchronized to the system clock.

4. A digital dead-time controller comprising:

a controller receiving a system clock and each of a plurality of phase-shifted versions of the system clock employed by a digital pulse width modulator, the controller further comprising;

first logic causing a duration of an output transistor control signal controlling a first output transistor driving an output node to be increased by a first selected multiple of phase-divisions of the system clock; and

second logic causing a leading edge of the output transistor control signal to be advanced relative to the system clock by a second selected multiple of phase-divisions of the system clock;

a first multiplexer receiving an output of the first logic as select controls, an output of the first multiplexer clocking a first latch controlling timing of a trailing edge of the output transistor control signal; and

a second multiplexer receiving an output of the second logic as select controls, an output of the second multiplexer clocking a second latch controlling timing of a leading edge of the output transistor control signal.

5. The digital dead-time controller according to claim 4, further comprising:

logic gates combining outputs of the first and second latches to produce the output transistor control signal.

6. The digital dead-time controller according to claim 5, wherein the logic gates further comprise:

a logic gate combining an output of an the digital pulse width modulator with an enable signal to produce a second output transistor control signal controlling a second output transistor driving the output node.

7. An integrated circuit including the digital dead-time controller according to claim 6, the integrated circuit further comprising:

the digital pulse width modulator; and

a dithering circuit increasing a duration of selected pulses within a series of output pulses from the digital pulse width modulator.

8. A digital dead-time control method comprising:

receiving a system clock and each of a plurality of phase-shifted versions of the system clock employed by a digital pulse width modulator;

increasing a duration of an output transistor control signal controlling a first output transistor driving an output node by a first selected multiple of phase-divisions of the system clock; and

advancing a leading edge of the output transistor control signal relative to the system clock by a second selected multiple of phase-divisions of the system clock.

9. The method according to claim 8, further comprising:

delaying a trailing edge of the output transistor control signal relative to the system clock.

10. The method according to claim 9, wherein a second output transistor control signal controlling a second output transistor driving the output node remains synchronized to the system clock.

11. The method according to claim 8, further comprising:

clocking a first latch controlling timing of a trailing edge of the output transistor control signal with an output of a first multiplexer; and

clocking a second latch controlling timing of a leading edge of the output transistor control signal with an output of a second multiplexer.

12. The method according to claim 11, further comprising:

combining outputs of the first and second latches to produce the output transistor control signal.

13. The method according to claim 12, further comprising:

combining an output of an the digital pulse width modulator with an enable signal to produce a second output transistor control signal.