Pulse width modulator having reduced signal distortion at low duty cycles

• US 6,838,862 B2
• Filed: 04/04/2003
• Issued: 01/04/2005
• Est. Priority Date: 04/04/2003
• Status: Active Grant

• Current Assignee: GatesAir Incorporated (Groupe Sipromad SA)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Luu, Ky Thoai
• Primary Examiner(s): HAN, YOUNGHUIE JESSICA
• Application Number:
  US10/407,689
• Publication Number:
  US 20040196012A1
• Time in Patent Office: 641 Days
• Field of Search: 323/273, 323/274, 323/275, 323/276, 323/277, 323/56, 323/57, 323/58, 323/299, 323/303
• US Class Current: 323/274
• CPC Class Codes: H02M 1/385 with means for correcting output voltage deviations introduced by the dead time
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A pulse width modulation apparatus includes a load circuit, a signal switch, a shunt switch, and a resistor. The signal switch isolates the load circuit from a voltage source along a signal path. The shunt switch is connected to the signal path at a point between the signal switch and the load circuit. The shunt switch isolates the signal path from a ground voltage. A resistor is connected in series between the signal switch and the shunt switch.

Claims

1. A pulse width modulation apparatus, comprising:

a load circuit, including a load;

a signal switch that isolates the load circuit from a voltage source along a signal path;

a shunt switch, connected to the signal path at a point between the signal switch and the load circuit, that isolates the signal path from a ground voltage;

a resistor connected in series between the signal switch and the shunt switch.

2. An apparatus as set forth in claim 1, wherein the apparatus further includes a shunt diode, connected to the signal path at its cathode and to a ground voltage at its anode.

3. An apparatus as set forth in claim 1, wherein the load comprises an antenna.

4. An apparatus as set forth in claim 1, wherein the load circuit further comprises a filter.

5. An apparatus as set forth in claim 4, wherein the filter comprises at least one inductor.

6. An apparatus as set forth in claim 1, wherein the signal switch and the shunt switch comprise transistors.

7. An apparatus as set forth in claim 1, wherein the apparatus further comprises a pulse generator that receives an input signal and generates a corresponding pulse width modulated drive signal.

8. An apparatus as set forth in claim 1, wherein the apparatus is implemented within a broadcast transmission system.

9. A pulse width modulation system, comprising:

a power supply that provides voltage to a load circuit along a signal path;

a signal switch that controls the flow of current along the signal path;

a shunt switch that controls the flow of current from the signal path to a ground voltage; and

a resistor that restricts the flow of current between the signal switch and the shunt switch.

10. A system as set forth in claim 9, wherein the system further includes a pulse generator that receives an input signal and generates a corresponding pulse width modulated drive signal.

11. A system as set forth in claim 10, wherein the signal switch is controlled by the drive signal.

12. A system as set forth in claim 10, wherein the shunt switch is controlled by an inversion of the drive signal.

13. A system as set forth in claim 9, wherein the system further includes a shunt diode that selectively prevents the flow of current from the signal path to a ground voltage.

14. A system as set forth in claim 13, wherein the shunt diode is connected to the signal path at its cathode, such that it prevents the flow of current until a threshold voltage is exhibited at a point of connection.

15. A system as set forth in claim 9, wherein the load circuit comprises a filter and a load, the filter correcting a plurality of signal pulses provided to the load, each signal pulse having an associated pulse width.

16. A system as set forth in claim 15, wherein the filter stores residual energy when a signal pulse is received at the circuit and discharges the residual energy between signal pulses.

17. A system as set forth in claim 16, wherein the residual energy is shunted as a current through the shunt diode for signal pulses above a threshold width, and the residual energy is shunted as a current through the shunt switch when the pulse width associated with the signal pulse is below a threshold width.

18. A system as set forth in claim 9, wherein the system is implemented within a broadcast transmission system.

19. A method of generating a pulse width modulated signal, comprising:

providing signal pulses, having an associated pulse width, across a load circuit, such that the load circuit accumulates residual energy;

shunting the residual energy from each signal pulse through a shunt diode when the associated pulse width of the signal pulse is above a threshold width;

shunting the residual energy from each signal pulse through a shunt switch when the associated pulse width of the signal is below a threshold width.