Infrared inductive light switch using triac trigger-control and early-charging-peak current limiter with adjustable power consumption

• US 6,369,517 B2
• Filed: 03/12/2001
• Issued: 04/09/2002
• Est. Priority Date: 06/27/2000
• Status: Expired due to Fees

• Current Assignee: Pericom Technology Incorporated (Diodes Incorporated)
• Original Assignee: Pericom Technology Incorporated (Diodes Incorporated)
• Inventors: Li, Jian, Song, Qun, Xie, Fang
• Primary Examiner(s): Philogene, Haissa
• Application Number:
  US09/681,273
• Publication Number:
  US 20020000758A1
• Time in Patent Office: 393 Days
• Field of Search: 315/158, 315/159, 315/194, 315/199, 315/200.R, 315/208, 315/224, 315/291, 323/220, 323/223, 323/224, 361/3, 361/5, 361/100
• US Class Current: 315/194
• 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: H05B 47/13 by using passive infrared detectors
• CPC Class Codes: H05B 47/165 following a pre-assigned programmed sequence; Logic control [LC]
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

An electronic switch can replace a standard mechanical light switch for 110-240 volt alternating-current (A.C.) devices. A triac switches the A.C. current to an A.C. device such as a light. A rectifier bridge generates a direct-current (D.C.) voltage that is applied to a special current limiter. The special current limiter generates a large current peak at low voltages, but limits current at high voltages. The large current peak from the special current limiter charges a capacitor when voltage is low at the beginning of each A.C. half-cycle, before the triac turns on. The capacitor has enough charge to supply D.C. current to an Infrared detector and trigger control logic for the rest of the A.C. half-cycle. When the detector detects a person nearby, it signals the trigger control logic. The D.C. voltage from the rectifier bridge is filtered to generate a sync pulse to the trigger control logic when adds a phase delay to the sync pulse which triggers the triac.

Claims

1. An electronic switch comprising:

alternating-current (A.C.) terminals for receiving alternating current for powering an A.C. device;

a rectifier, coupled to the A.C. terminals, for generating a rectified D.C. voltage;

a triggered current switch, coupled to at least one of the A.C. terminals, for switching the alternating current to the A.C. device;

a coupler for coupling a trigger pulse to the triggered current switch, the trigger pulse causing the triggered current switch to switch the alternating current;

a current limiter, receiving the rectified D.C. voltage from the rectifier, for generating a charging-current pulse for low voltages of the rectified D.C. voltage, but limiting current at high voltages above the low voltages;

a charge store, receiving the charging-current pulse from the current limiter, for storing charge, the charge store outputting charge to an internal D.C. supply when the current limiter limits current at the high voltages; and

D.C. logic, powered by the internal D.C. supply from the charge store, the D.C. logic generating the trigger pulse coupled to the triggered current switch,

whereby the D.C. logic is powered by the charge store that is charged by the charging-current pulse for low voltages.

2. The electronic switch of claim 1 wherein the D.C. logic further comprises:

a detector, powered by the internal D.C. supply, for generating a detect signal when the electronic switch is to switch the alternating current to the A.C. device;

trigger control logic, powered by the internal D.C. supply, receiving the detect signal from the detector and generating the trigger pulse.

3. The electronic switch of claim 2 wherein the trigger pulse is synchronized to an A.C. cycle of the alternating current.

4. The electronic switch of claim 3 further comprising:

a synchronizing network, receiving the rectified D.C. voltage, for generating a sync pulse to the trigger control logic, the sync pulse being synchronized to the A.C. cycle of the alternating current;

the trigger control logic receiving the sync pulse from the synchronizing network, the trigger control logic generating the trigger pulse in response to the sync pulse when the detect signal is activated by the detector.

5. The electronic switch of claim 4 wherein the trigger pulse has a phase delay from the sync pulse, the phase delay determining a conducting angle, the conducting angle being a portion of the A.C. cycle wherein the A.C. device is powered, wherein larger phase delays reduce overall power delivered to the A.C. device by reducing the conducting angle.

6. The electronic switch of claim 5 wherein the conducting angle is between 5°

and 175°

, wherein each A.C. cycle contains two half-cycles having 180°

each;

wherein the A.C. terminals receive an alternating voltage of 110 to 240 volts root-mean-square (rms).

7. The electronic switch of claim 5 wherein the phase delay is variable to reducing power to the A.C. device.

8. The electronic switch of claim 5 wherein the detector detects infrared light, sound, motion, proximity, vibration, radio signals, or presence of a person nearby.

9. The electronic switch of claim 5 wherein the current limiter generates the charging-current pulse before the trigger pulse activates the triggered current switch, the charging-current pulse being terminated when the triggered current switch switches the alternating current to the A.C. device;

wherein when the detect signal is not generated by the detector and the triggered current switch is not triggered, the current limiter ends the charging-current pulse in response to the rectified D.C. voltage reaching a predetermined voltage.

10. The electronic switch of claim 9 wherein the current limiter comprises:

a first transistor, conducting a first current when the rectified D.C. voltage is below the predetermined voltage,

a first resistor, limiting the first current from the first transistor;

a second transistor, conducting a second current when the rectified D.C. voltage is above the predetermined voltage,

a second resistor, limiting the second current from the second transistor;

wherein the first resistor has a lower effective resistance than the second resistor, the first current being a larger current than the second current;

wherein the charging-current pulse is generated by the first current through the first transistor, while the second current is limited by the second resistor.

11. The electronic switch of claim 10 wherein the second current is less than a maximum first current at a peak of the charging-current pulse for all rectified D.C. voltages above the predetermined voltage.

12. The electronic switch of claim 11 wherein the current limiter further comprises:

a Zener diode, for conducting current to activate the second transistor when the rectified D.C. voltage is above the predetermined voltage, the Zener diode not conducting sufficient current to activate the second transistor when the rectified D.C. voltage is below the predetermined voltage,

whereby the Zener diode sets the predetermined voltage.

13. The electronic switch of claim 12 wherein the current limiter comprises:

a first path from the rectified D.C. voltage to the charge store, the first path comprising the first transistor and the first resistor in series;

a second path from the rectified D.C. voltage to the charge store, the second path comprising the second transistor and the second resistor in series;

wherein a voltage generated in the second path controls activation of the first transistor;

a third path from the rectified D.C. voltage to the charge store, the third path comprising the Zener diode and at least one resistor in series;

wherein a voltage generated in the third path controls activation of the second transistor.

14. The electronic switch of claim 10 wherein the first and second transistors are bipolar transistors activated by a base current that flows when an activating voltage occurs or metal-oxide-semiconductor (MOS) transistors activated by a gate voltage.

15. The electronic switch of claim 9 wherein when the detect signal is not generated by the detector and the triggered current switch is not triggered, a second charging-current pulse is generated by the current limiter when the rectified D.C. voltage falls back down to the predetermined voltage after having risen above the predetermined voltage,

whereby two charging-current pulses are generated when the detect signal is not generated.

16. The electronic switch of claim 15 wherein the A.C. cycle comprises two half-cycles;

wherein the charging-current pulse is generated at a beginning of each of the two half-cycles for every A.C. cycle,

whereby the charge store is recharged by the charging-current pulse at least twice for every A.C. cycle.

17. The electronic switch of claim 16 wherein the rectifier is a single diode half-wave rectifier or a four-diode full-wave rectifier:

wherein the coupler is an opto-electronic coupler, a capacitor, a transformer, or a direct-wired connection;

wherein the triggered current switch is a triac, a thyristor, or a silicon-controlled rectifier;

wherein the charge store is a shunt capacitor and a shunt diode to a ground;

wherein the synchronizing network is a resistor or a resistor in series with a capacitor.

18. A switch comprising:

terminals for receiving an alternating-current (A.C.) voltage, the A.C. voltage being a power source for the switch;

rectifier means, receiving the A.C. voltage, for generating a direct current (D.C.) voltage, the D.C. voltage varying in cycle pulses synchronized to A.C. cycles of the A.C. voltage, the cycle pulses including an initial region when the D.C. voltage is less than a critical voltage, a middle region wherein the D.C. voltage is above the critical voltage, and a final region wherein the D.C. voltage is again below the critical voltage;

current-switch means, coupled to the terminals, for switching the alternating-current voltage to selectively power an A.C. device in response to a trigger signal;

limiter means, receiving the D.C. voltage from the rectifier means, for generating a high-current peak during the initial region, but for limiting current to below the high-current peak during the middle region;

charge store means, coupled to receive the high-current peak from the limiter means, for storing charge and generating an internal D.C. supply voltage; and

D.C. means, powered by the internal D.C. supply voltage from the charge store means, for generating the trigger signal to the current-switch means, the trigger signal causing the current-switch means to power the A.C. device,

whereby the internal D.C. supply voltage is generated from the A.C. voltage by charging the charge store means during the initial region of the cycle pulses.

19. The switch of claim 18 wherein the D.C. means is only powered by the charge store means, the switch not receiving any external D.C. power.

20. The switch of claim 18 further comprising:

sync means, coupled to the D.C. voltage from the rectifier means, for generating sync pulses to the D.C. means at a start of every cycle pulse;

the D.C. means comprising detect means for detecting when the A.C. device is to be powered and trigger means, responsive to the detect means, for generating the trigger signal at a start of each cycle pulse when the detect means detects that the A.C. device be powered, the trigger signal being generated after a phase delay relative to the start of every cycle pulse, wherein when the detect means detects that the A.C. device be powered, the A.C. device is powered for a powered portion of every cycle pulse, but not powered for a start portion of every cycle pulse before the powered portion, the start portion being a portion including the phase delay;

whereby the A.C. device is pulsed on for the powered portion of the A.C. cycles but off for the start portions.

21. An alternating-current (A.C.) switch comprising:

A.C. terminals for receiving an A.C. voltage having an A.C. cycle;

a triac, coupled between the A.C. terminals, for connecting the A.C. terminals together to power an A.C. device in response to a trigger input;

a rectifier bridge, coupled across the A.C. terminals, having a ground output and a rectified D.C. node with a rectified voltage;

a special current limiter, coupled to the rectified D.C. node, having a first path that conducts a large peak current to an internal D.C. supply when the rectified voltage is below a critical voltage, and a second path that conducts a small current to the internal D.C. supply when the rectified voltage is above the critical voltage, the small current being less than the large peak current;

a shunt capacitor, coupled across the internal D.C. supply and the ground, for storing charge from the large peak current;

a shunt diode, coupled across the internal D.C. supply and the ground, for limiting a maximum voltage of the internal D.C. supply;

a detector, coupled between the internal D.C. supply and the ground, for generating a detect signal indicating that the A.C. device be powered;

a sync signal, having sync pulses generated in synchronization to the A.C. cycle;

trigger control logic, coupled between the internal D.C. supply and the ground, receiving the detect signal and the sync signal, for generating a first pulse when the detect signal is activated and a sync pulse is received; and

a coupler for coupling the first pulse to the trigger input of the triac,

whereby the triac is triggered on by the first pulse generated by the trigger control logic powered by the shunt capacitor charged by the special current limiter.

22. The A.C. switch of claim 21 wherein the special current limiter comprises:

the first path comprising a first transistor and a first resistor in series that generate the large peak current;

the second path comprising a second resistor and a second transistor in series that generate the small current and a first control voltage that disables the first transistor when the second transistor is enabled;

a third path comprising at least one resistor and a Zener diode that begins conducting when the critical voltage is reached, the third path generating a second control voltage that causes the second transistor to be enabled when the Zener diode begins conducting.

23. The A.C. switch of claim 22 wherein the special current limiter further comprises:

a first interlocked transistor in series with at least one resistor, for generating a third control voltage, coupled to the second transistor, the third control voltage enabling the second transistor;

a second interlocked transistor, of an opposite polarity type as the first interlocked transistor, coupled to conduct current around the Zener diode when the first interlocked transistor is enabled;

wherein the first interlocked transistor is controlled by the second control voltage, the first interlocked transistor beginning to conduct when the Zener diode conducts as the critical voltage is reached, but the first interlocked transistor continuing to conduct after the Zener diode stops conducting as the rectified voltage falls,

whereby the interlocked transistors prevent the first transistor from being re-enabled after the Zener diode turns off.

24. The A.C. switch of claim 23 wherein the sync signal is generated from the rectified voltage by a resistor and a capacitor;

wherein the coupler is an opto-electronic coupler, a capacitor, a transformer, or a direct-wired connection;

wherein the detector detects infrared light, sound, motion, proximity, vibration, radio signals, or presence of a person nearby.