Power control system with improved phase control

• US 5,268,631 A
• Filed: 11/06/1991
• Issued: 12/07/1993
• Est. Priority Date: 11/06/1991
• Status: Expired due to Term

• Current Assignee: CAE Incorporated
• Original Assignee: Chicago Stage Equipment Company
• Inventors: Gorman, John E., Warren, Rufus W.
• Primary Examiner(s): Sterrett, J. L.
• Application Number:
  US07/788,437
• Time in Patent Office: 762 Days
• Field of Search: 323/235, 323/237, 323/242, 323/243, 323/246, 323/319, 323/320, 323/326, 323/905
• US Class Current: 323/246
• CPC Class Codes: G05F 1/455 with phase control
• CPC Class Codes: H02M 5/2573 with control circuit
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 323/905 Lamp dimmer structure

Abstract

An improved phase-controlled power control apparatus includes a semiconductor switching element for varying the effective power delivered to a load from the power lines. The conduction angle of the semiconductor power switch element is varied from a nominal angle to compensate for changes in power line voltage and for changes in load current. The amount of load current flow is continuously compared to the power line voltage to detect any overcurrent condition, even very close to the zero-crossing of the power line voltage. The shape of the transition from load current on to load current off (or vice versa) in controlled to minimize audible noise from the load. The load current can be shared between a plurality of compatible power control sections.

Claims

1. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means response to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

transition control circuit means interposed between said drive control circuit means and said power switching means and responsive to predetermined additional control signals for shaping the rise time of the voltage feed to the load in a predetermined fashion for reducing the acoustic noise produced by said load;

wherein said transition control circuit means includes voltage sensing means for sensing the voltage across said power switching means, and voltage comparator means for comparing the voltage sensed by said voltage sensing means with a predetermined voltage and coupled to said drive control circuit means for increasing the rate of transition of the voltage feed to the load after the start of an on-to-off transition of the power signal produced by the power switching means.

2. A system according to claim 1 and further comprising load compensation circuit means including current sensing means for sensing the current to said load and coupled to said drive control means for increasing the output voltage to said load to compensate for voltage drops experienced intermediate said power switching means and said load due to current draw by the load.

3. A system according to claim 2 wherein said load compensation circuit means further includes time delay control means for varying the amount of time delay in the voltage feed to the load in each AC half-cycle a predetermined fashion in accordance with the instantaneous AC line voltage throughout the AC line voltage cycle.

4. A system according to claim 1 and further including line voltage regulation circuit means coupled with said phase control timing circuit means for controllably varying a conduction angle of the phase controlled signal produced thereby in response to AC line voltage variations.

5. A system according to claim 4 wherein said line voltage regulation circuit means comprises sample and hold circuit means which samples a full-wave rectified line voltage signal only once per AC cycle to minimize response time and out overshoot on each half-cycle of AC voltage;

memory means responsive to said sample and hold circuit for generating a current correction signal, and timing ramp generator means responsive to the AC line voltage and to said memory means for generating a corrected ramp signal for varying the conduction angle of the phase-control timing signal generated by the phase-control timing circuit means.

6. A system according to claim 1 and further including short circuit protection circuit means comprising current sensing means for sensing the instantaneous current to the load and producing a corresponding voltage signal;

line voltage sensing means for producing a voltage signal corresponding to the line voltage;

voltage comparator circuit means for comparing said voltages produced by said line voltage sensing means and said current sensing means and producing a corresponding control voltage for causing said drive control circuit means to control the power switching circuit means for cutting off current to the load when the proportion of the instantaneous current to the line voltage exceeds a predetermined proportion, until the power line voltage reaches a zero crossing, to thereby allow repetitive application of current to said load every half-cycle.

7. A system according to claim 1 and further including load compensation circuit means comprising long-term current limiting circuit means comprising current sensing means for sensing the instantaneous current to said load;

averaging filter means for averaging said instantaneous current sensed by the current sensing means to produce a signal corresponding to the long-term load current and means for comparing said signal corresponding to said long-term current with a selectively time-variable threshold voltage for causing said drive control circuit means to limit the current delivered by said power switching circuit means to said load when the long-term instantaneous current exceeds a predetermined average rated power of said systems.

8. A system according to claim 1 and further including circuit means for sharing current among a plurality of compatible ones of said semiconductor-controlled power control systems and for providing substantially equal or properly proportioned current sharing between said systems.

9. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

transition control circuit means interposed between said drive control circuit means and said power switching means and responsive to predetermined additional control signals for shaping the rise time of the voltage feed to the load in a predetermined fashion for reducing the acoustic noise produced by said load;

wherein said transition control circuit means includes current sensing means for sensing the instantaneous current to the load and producing a corresponding voltage signal, and voltage comparator means for comparing said corresponding voltage signal with a predetermined voltage and coupled to said drive control circuit means for varying said drive control signal to cause said power switching means to reduce the rate of transition of the voltage near the end of the on-to-off transition of the power signal produced by said power switching means; and

wherein said voltage comparator means compares said corresponding voltage signal to the line voltage for varying the drive control signal to cause said power switching means to reduce the rate of transition of the voltage when the line voltage at the moment of the start of transition is below a preselected voltage.

10. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

circuit means for sharing current among a plurality of identical or compatible ones of said semiconductor-controlled power control systems and for providing substantially equal or properly proportioned current sharing between said systems.

11. A system according to claim 10 wherein said circuit means for sharing current comprises relatively low-value resistive means in the current path of the semiconductor power switching means of each of said systems and capacitive means coupled intermediate the semiconductor power switching means of each said system.

12. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

load compensation circuit means including current sensing means for sensing the current to said load and coupled to said drive control means for increasing the output voltage to said load to compensate for voltage drops experienced intermediate said power switching means and said load due to current draw by the load.

13. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplied;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals;

sand line voltage regulation circuit means coupled with said phase control timing circuit means of controllably varying a conduction angle of the phase controlled signal produced thereby in response to AC line voltage variations;

wherein said line voltage regulation circuit means comprises sample and hold circuit means which samples a full-wave rectified line voltage signal only once per AC cycle to minimize response time and overshoot on each half-cycle of AC voltage;

memory means responsive to said sample and hold circuit for generating a current correction signal, and timing ramp generator means responsive to the AC line voltage and to said memory means for generating a corrected ramp signal for varying the conduction angle of the phase-control timing signal generated by the phase-control timing circuit means.

14. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

short circuit protection circuit means comprising current sensing means for sensing the instantaneous current to the load and producing a corresponding voltage signal;

line voltage sensing means for producing a voltage signal corresponding to the line voltage;

voltage comparator circuit means for comparing said voltages produced by said line voltage sensing means and said current sensing means and producing a corresponding control voltage for causing said drive control circuit means to control the power switching circuit means for cutting off current to the load when the proportion of the instantaneous current to the line voltage exceeds a predetermined proportion, until the power line voltage reaches a zero crossing, to thereby allow repetitive application of current to said load every half-cycle.

15. An improved semiconductor-controlled power control system comprising:

power supply means for receiving an AC line voltage and for converting said AC line voltage to predetermined rectified AC and DC power supplies;

phase control timing circuit means coupled to said power supply means for generating and shaping electrical timing signals;

drive control circuit means responsive to said electrical timing signals for producing predetermined drive signals;

semiconductor power switching means for delivering power to a load in response to said drive control signals; and

load compensation circuit means comprising long-term current limiting circuit means comprising current sensing means for sensing the instantaneous current to said load;

averaging filter means for averaging said instantaneous current sensed by the current sensing means to produce a signal corresponding to the long-term load current and means for comparing said signal corresponding to said long-term current with a selectively time-variable threshold voltage for causing said drive control circuit means to limit the current delivered by said power switching circuit means to said load when the long-term instantaneous current exceeds a predetermined average rated power of said system.