CN115668735A

CN115668735A - Two-wire electronic switch and dimmer

Info

Publication number: CN115668735A
Application number: CN202080100015.9A
Authority: CN
Inventors: 马克·特勒富斯
Original assignee: Amber Semiconductor Inc
Current assignee: Amber Semiconductor Inc
Priority date: 2020-08-05
Filing date: 2020-08-05
Publication date: 2023-01-31
Also published as: JP2023525754A; EP4107849A4; US11870364B2; WO2022031276A1; KR20230008868A; US20220416681A1; EP4107849A1; US20220311350A1

Abstract

A bi-directional switch and dimmer for controlling power from an AC source to a load is described. The method uses power MOSFETs in a bidirectional switch sub-circuit configuration that includes a floating AC/DC power supply and a solid state bipolar switch that alternates between connection of an AC source to a load and periodic connection of the AC source to the AC/DC power supply. The switch and dimmer circuit configuration allows for the use of only two wires to be plugged into an existing single phase circuit. This design allows the entire circuit to be fabricated on a single chip.

Description

Two-wire electronic switch and dimmer

Cross Reference to Related Applications

Not applicable.

Statement regarding federally sponsored research or development

Not applicable.

Background of the invention

Technical Field

The invention relates to a power management system and method for providing electronic switching and dimming control.

Background

In both domestic and commercial environments, access to conventional Alternating Current (AC) power is provided through mechanical outlets wired to the facility electrical system. Electromechanical devices such as fuses and circuit breakers are used to protect these outlets from excessive electrical loads or potentially dangerous ground faults. Similarly, conventional indoor appliances such as lighting and ceiling fans are controlled using electromechanical switches. These substantially mechanical control devices provide simple on/off control and inevitably wear out and over time may lead to short circuits or potentially dangerous arcs.

Finer control of the general electrical appliance is typically provided by electronics, such as triacs, which allow the AC power waveform to be interrupted on a cycle by cycle basis, i.e., so-called phase control. Although much more efficient than previous varistors or autotransformers, the efficiency of triacs is still too low to be effectively used in small enclosures for controlling large electrical loads and may induce electrical noise back into the facility electrical system. In addition, they can cause modern Light Emitting Diode (LED) lights to flicker, which can have adverse health effects.

Prior art AC switches use high voltage semiconductor devices such as bipolar transistors or MOSFETs to control the application of AC power to the desired load. These modern circuits incorporate an AC/DC power supply and a transistor-type control circuit, which in a typical single-phase circuit requires access to all three wires: the hot line of the AC power source, the leads of the switching load and the common neutral line. An example of such a prior art three wire system includes international application publication WO 2019/133110, entitled "Electronic Switch and Dimmer", filed on 11, 7, 2018 by Telefus et al.

There is a need for an improved electronic AC control system that provides a wide range of more reliable and efficient control options for wide application in facility electrical systems. Further, there is a need for a control system that can be implemented using semiconductor devices that can be integrated with other circuitry to implement advanced power control functions that can be manufactured at low cost, and a control system that can be simply installed using only two wires (AC power supply live wire and load).

Disclosure of Invention

The present invention relates to a novel method for controlling AC power throughout a utility electrical system ranging from simple socket on/off switching to continuous variation of applied AC power-for dimming of e.g. electric lights. More particularly, the present invention relates to a functional combination that provides both on/off and phase control of an AC power waveform in one embodiment.

One embodiment uses a power MOS field effect transistor (MOSFET) as an electronic switch with a very low "on" resistance connected between the AC power supply and the desired load. Because a typical power MOSFET inherently incorporates a body diode in parallel with a conducting channel, pairs of devices are connected in a back-to-back arrangement with a common source terminal to provide a true bidirectional (AC) switching configuration. To control the switching action of the power MOSFETs, a novel floating AC/DC power supply is incorporated that is periodically refreshed by operating the MOSFET switches in synchronism with the AC power waveform.

The specific examples are not intended to limit the inventive concepts to the example applications. Other aspects and advantages of the invention will become apparent from the drawings and the detailed description.

Drawings

Fig. 1 is a block diagram of a basic prior art three-wire switching/dimmer circuit.

FIG. 2 is a schematic diagram of a prior art switching AC/DC power supply.

Fig. 3A is a schematic diagram of the basic elements of a prior art bi-directional switch.

Fig. 3B is a modification of the circuit of fig. 3A, including an additional load across the switching device.

Fig. 3C is the circuit of fig. 3B, showing current through the additional load when the switching device is "off.

Fig. 4 is a block diagram of an embodiment of a two-wire switch/dimmer circuit.

FIG. 5 is a schematic diagram of an embodiment of the AC/DC power supply of FIG. 2 using MOSFETs.

FIG. 6 is a schematic diagram of an embodiment of the three-wire circuit of FIG. 1 using a variation of the AC/DC power supply of FIG. 5 and the basic switching circuit of FIG. 3A.

Fig. 7 is a schematic diagram of the embodiment of fig. 6 in which the elements have been reconnected to produce the two-wire circuit of fig. 4.

Fig. 8A shows an effective configuration of the circuit of fig. 7 with the MOSFET "off" in the bi-directional switch and the neutral line positive with respect to the hot line.

Fig. 8B shows an effective configuration of the circuit of fig. 7 with the MOSFETs in the bi-directional switch "off" and the hot line positive with respect to the neutral line.

Fig. 9 shows an effective configuration of the circuit of fig. 7 when the MOSFET in the bi-directional switch is "on".

Fig. 10 shows the circuit of fig. 7 with the addition of sub-circuits for overcurrent protection and output DC voltage regulation.

Fig. 11 shows details of a ballast circuit as used in fig. 10.

Detailed Description

Fig. 1 is a block diagram of a basic prior art three-wire switching/dimmer cell 100 using solid state switching devices. An AC power source 101 provides a hot 103 and neutral 105 input connection through a switching/dimmer circuit 100 to a load 102, the load 102 being connected to a load 104 and neutral 105 output connection. The switching device 108 is driven by a switching control circuit 107, the switching control circuit 107 being supplied with DC power by the AC/DC power supply 106. In the switching mode, a continuous DC bias is applied by the control circuit 107 to the switching device 108 to maintain closure. In the dimmer mode, the operating bias is provided by the control circuit 107 as pulses synchronized to the AC power source 101 waveform, where the duty cycle of the pulses establishes the percentage of the total power applied to the load. As is known in the art, for dimmer operation, the controller 107 includes a pulse generation circuit and is synchronized with the AC power source. The controller may also contain a user interface to input the desired power to the load. In one embodiment, the user interface is physically incorporated into the control circuitry 107. In another embodiment, the control circuitry comprises wireless communication circuitry, and the user interface is physically remote from the control circuitry 107. It should be noted that at least three connections (103 to 105) are required to install the switch/dimmer unit.

FIG. 2 is a schematic diagram of a prior art switching AC/DC power supply 106. The circuit comprises a

voltage divider network

201, 202 having an output node 204 and connected across the AC power source 101. The inverting input of comparator circuit 203 is connected to the voltage divider output node 204 and has a reference voltage V _R Is connected to its non-inverting input, wherein the comparator 203 controls the series switch 206 if the voltage divider outputs a voltage V _D Exceeding a reference voltage V _R Then the series switch 206 disconnects (disconnect) the live input 103 from the subsequent circuit (open switch 206). When switch 206 is closed, capacitor 208 is charged through series diode 207. Diode 207 prevents capacitor 208 from discharging back through switch 206 when the voltage divider output voltage drops. Thus, the combination of the diode 207 and the capacitor 208 forms a "peak detector" circuit that stores energy in each half of the AC mains cycle for supply to the subsequent regulator circuit and load 209. The voltage across the capacitor 208 need only be large enough to meet the energy requirements of the subsequent regulator circuit and the load 209. The input voltage to the subsequent regulator 209 is significantly reduced compared to the rms value of the AC power supply. The operation of the "peak detector" circuit ensures that the steady state voltage stored on the capacitor 208 is always V _R Regardless of fluctuations in the peak voltage of the AC power source, as long as the voltage at the voltage divider output 204 remains greater than V _R . This embodiment of the switching circuit operates as a voltage regulator circuit itself.

FIG. 3A is a schematic diagram of the basic elements of a prior art bi-directional switch 108 that uses power MOSFET devices to create a bi-directional electronic switch that controls the power delivered from AC source 101 to load 102.

Power MOSFETs

301 and 302 include

body diodes

303 and 304, respectively. Switch 306 controls the gate-to-source bias voltage applied to

power MOSFETs

301 and 302. In the "on" 307 position, a bias voltage 305 is applied to the

gate terminals

313, 314 of the

power MOSFETs

301 and 302. Voltage 305 is a voltage greater than the threshold voltage of the power MOSFET (typically 5 to 10 volts) which causes inversion layer formation, creating a conductive channel extending from the

drain

309, 310 to the

source

311, 312 of each device. In this "on" state, the drain-to-source behavior of each power MOSFET can act as a low value resistor R _ds To model. The body diode remains non-conductive as long as the voltage drop between the drain and source remains below about 0.6 volts, and can be ignored. In the "on" state, the circuit of FIG. 3A is equivalently implemented by having a value of 2R _ds Is connected to a load 102 of the AC source 101.

In the "off" 308 position of switch 306, the

gate terminals

313, 314 of the

power MOSFETs

301, 302 are shorted to the

source terminals

311, 312 and the drain-to-source conductive channel disappears as long as the drain-to-source voltage remains below the breakdown voltage of the body diode. In the "off" state, the circuit of fig. 1 is equivalently the load 102 connected to the AC source 101 through back-to-

back body diodes

303 and 304, which effectively disconnects the load 102 from the source 101.

The drain-to-source voltage of the power MOSFET remains below the body diode breakdown voltage V in the "off" state _br The requirement of (a) requires that the breakdown voltage of the body diode exceed the peak voltage of the AC source 101. Thus, for example, assuming that source 101 corresponds to a common 120 volt (rms) AC power supply, the breakdown voltage of each body diode must exceed the peak source voltage of 170 volts.

A more detailed analysis of the power MOSFET structure shows that the body diode is actually the base-collector junction of a bipolar transistor connected in parallel with the MOSFET channel. The additional parasitic element includes the capacitance of the base-collector junctionAnd parasitic resistance between the base and the emitter. The AC coupling circuit changes the rate dV of the drain-to-source voltage _ds The/dt imposes a constraint to avoid forward biasing the base-emitter junction, thereby causing the bipolar transistor to conduct when the MOSFET channel is "off. While the resulting leakage current may not be sufficient to energize load 102, it may be large enough to cause additional efficiency or safety issues.

Similarly, the constraint in the "on" state needs to be represented by R _ds * Iload gives a drain-to-source voltage drop of less than about 0.6 volts per power MOSFET. Perhaps more importantly, from R _ds *Iload ² The power dissipated by each given power MOSFET in the "on" state must be kept to less than a few watts to avoid excessive temperature rise. Thus, for example, switching a common household circuit from a 120 volt AC power supply with a typical limit of 20 amps requires R for each power MOSFET _ds Less than 0.005 ohm (5 milliohms).

It is well known in the art that the breakdown voltage of a body diode can be advantageously matched to R by varying the structure and doping level in the device _ds The value of (c) is weighted. In particular, R has been shown _ds Value of and V _br ^2.5 Is in direct proportion. Thus, for example, V _br Halving leads to R _ds Decreasing by a factor of 5.7.

The circuit of fig. 3A shows a conceptual bias switching circuit comprising a switch 306 and a voltage source 305, which is electrically floating with the common source terminals of back-to-

back power MOSFETs

301 and 302 whose voltage varies across the peak-to-peak range of the source 101. Although conceptually simple, such floating bias circuits may be difficult to implement at low cost in practice.

Fig. 3B shows a modification of the circuit of fig. 3A in which an additional load device 317 is connected in parallel with the

power MOSFETs

301 and 302, with the control switch 306 in the "on" position, which connects the

power MOSFET gates

313, 314 to the voltage 305. Current flows from the AC source 101 through the power MOSFET channel to the load 102, effectively bypassing the extra load device 317 following path 318. Fig. 3C shows the circuit of fig. 3B when control switch 306 is moved to the "off" position to connect power

MOSFET gate electrodes

313, 314 to source

terminals

311, 312. In this case, the power MOSFET device is non-conductive and current flows from the AC source 101 through the extra load 317. Current follows path 319 to flow through the additional load 317 and the load 102 and back to the AC source 101. Thus, the bi-directional switching circuit acts as a bi-polar switch, supplying full current to the load 102 when the power MOSFET is "on" and supplying reduced power to the additional load 317 when the power MOSFET is "off.

Fig. 4 is a block diagram of an embodiment of a two-wire switch/dimmer 400. In contrast to fig. 1, the electronic switch and dimmer 400 requires only two

wires

103, 104 to connect and operate. The electronic switching element 401 connects the AC power source 101 directly to the load 102. The AC power is provided to the AC/DC converter 106 via

supply lines

402, 403, and the filtered and regulated DC power is provided to subsequent circuits via

DC output lines

404, 405. The control circuit 107 is supplied with DC power via

input lines

406, 407 and control signals for controlling the state of the switch 401 are provided via

control lines

408, 409. As in the circuit of fig. 1, in dimmer mode, the operating bias of the switch 401 is provided by the control circuit 107 as pulses synchronized with the AC power source 101 waveform, where the duty cycle of the pulses establishes the percentage of the total power applied to the load. Continuous full power operation in the switch mode requires the switch 401 to be periodically opened (open) to refresh the AC/DC power supply 106, which AC/DC power supply 106 must incorporate sufficient energy storage to provide operating DC power between refresh operations.

Fig. 5 is a schematic diagram of an embodiment of the AC/DC power supply of fig. 2 using MOSFETs, one 503 with an input/gate 510 and an output 511 to form a simple comparator circuit (203 in fig. 2), and one 506 with an input/gate 512 and an output 513 as a switch (206 in fig. 2). The input to the comparator is the gate 510 of the MOSFET503 and the analog of the voltage reference 205 in fig. 2 is the threshold voltage of the MOSFET 503. Two

MOSFETs

503 and 506 incorporate body diodes shown explicitly as 504 and 507, respectively. The voltage

divider comprising resistors

501 and 502 is actually present across the DC output node 514 rather than across the AC power source 101. Thus, when the DC output 514 reaches a value determined by the threshold voltage of MOSFET503 and the voltage division ratio established by

resistors

501 and 502, MOSFET503 turns on, thereby turning off switching MOSFET 506. It should be noted that when the hot line 103 of the AC power source 101 is positive with respect to the neutral line 105, the circuit operates as described. When the neutral 105 is positive with respect to the hot line 103, current flows through the body diode 504, the current limiting resistor 505, the parallel network of the zener diode 508 and the capacitor 509, and back to the AC power source 101 through the body diode 507. This charges the capacitor 509 to a zener voltage that is selected to sufficiently exceed the threshold voltage of the switching MOSFET 506 to ensure that it is fully conductive when the polarity of the AC power source 101 is reversed. This circuit configuration significantly reduces the power consumed by the switching MOSFET 506 in its forward conduction mode, thereby significantly improving the efficiency of the circuit.

FIG. 6 is a schematic diagram of an embodiment of the three-wire circuit 100 of FIG. 1 using a variation of the AC/DC power supply of FIG. 5 and the basic switching circuit of FIG. 3. The switching circuit includes

power MOSFETs

301 and 302, which contain

body diodes

303 and 304, respectively, and is relocated to the AC power source 101 neutral 105 to achieve the control voltage level provided by the AC/DC power supply. The function of the switch 306 in fig. 3 is achieved directly using the control circuit 107, the control circuit 107 providing the floating

control outputs

408 and 409 and being powered by the AC/DC power supply circuit shown in fig. 5.

Fig. 7 is a schematic diagram of the embodiment of fig. 6 in which elements have been alternately connected to produce the two-wire circuit 400 of fig. 4. The new configuration primarily involves reconnecting the live line 103 of the AC source 101 to the previous neutral line 105, reconnecting the load from the previous live line 103 of the AC source 101 to the AC source 101 neutral line 105, reconnecting the drain 701 of the MOSFET 506 from the previous live line 103 of the AC source 101 to the bidirectional switch output node 702, and separating the floating neutral line 404 connected to the capacitor 208, the control circuit 107, and the common source connection of the

MOSFET switching devices

301 and 302 from the previous AC source 101 neutral line 105. As in fig. 6, the control circuit 107 provides floating

control outputs

408 and 409. In summary, the bidirectional electronic switching system 400 is for switching current in an Alternating Current (AC) circuit between an AC source 101 having a first terminal and a second terminal and a load 102 having a first terminal and a second terminal, and has an input terminal 103 connected to the first terminal of the AC source 101 and an output terminal 104 connected to the first terminal of the load 102, wherein the second terminal of the AC source 101 and the second terminal of the load 102 are interconnected external to the bidirectional switching system; further comprising:

an AC-to-DC conversion system 106, the AC-to-DC conversion system 106 having a first 402 input terminal and a second 403 input terminal for providing energy from an AC source 101 in Direct Current (DC) to a first 404 output terminal and a second 405 output terminal connected to control circuitry 107, and

b. control circuitry 107, the control circuitry 107 having first and second

DC input terminals

406, 407 connected to first and

second outputs

404, 405, respectively, of the AC-to-DC conversion system 106; and a first output terminal 408 and a second output terminal 409 for providing control signals to the electronic switch 401, an

c. An electronic switch 401, the electronic switch 401 being connected between the input terminal 103 and the bidirectional switch output terminal 104; wherein the state of the control signal present between the control

system output terminals

408, 409 determines the state of the switch.

Fig. 8A shows an effective configuration of the circuit of fig. 7 in which

MOSFETs

301 and 302 are "off" in a bidirectional switching circuit and live line 103 of AC power source 101 is positive with respect to neutral line 105 of AC power source 101. Current flows through the body diode 504, the current limiting resistor 505, the parallel network of the zener diode 508 and the capacitor 509, and back to the AC power source 101 through the body diode 507 and the load 102. This charges the capacitor 509 to a zener voltage that is selected to sufficiently exceed the threshold voltage of the switching MOSFET 506 to ensure that it is fully conductive when the polarity of the AC power source 101 is reversed.

Fig. 8B shows an effective configuration of the circuit of fig. 7 with the MOSFET "off" in the bi-directional switch and the neutral 105 of the AC power source 101 positive with respect to the live 103 of the AC power source 101. Current flows through the load 102, the channel of MOSFET 506 and the peak detect diode 207, thereby charging the capacitor 208 to a voltage determined by the threshold voltage of MOSFET503 and the voltage

divider comprising resistors

501 and 502, back to the AC power source 101 through the forward biased body diode 303.

Fig. 9 shows an effective configuration of the circuit of fig. 7 when the MOSFET in the bi-directional switch is "on". The AC/DC power supply circuit is bypassed and all current flows from the AC power source 101 through the load 102.

Fig. 10 shows the circuit of fig. 7 with the addition of sub-circuits for overcurrent protection, for output DC voltage regulation, and to provide a ballast for LED lighting. The current sampling resistor 1002 and the npn bipolar transistor 1001 form an overcurrent protection circuit. Resistor 1002 has a very small value (much less than 1 ohm) determined by the maximum current rating of power MOSFET 506. When the voltage drop across resistor 1002 exceeds about 0.6V (for a silicon transistor), bipolar transistor 1001 conducts, thereby connecting the gate of MOSFET 506 to its source and reducing the current. The series pass MOSFET 1003, bias resistor 1004, zener diode 1005 and filter capacitor 1006 form a simple voltage regulation circuit. The output voltage 514 will be adjusted to the value given by the zener voltage of diode 1005 minus the threshold voltage of pass MOSFET 1003. In one embodiment, the two-wire switch further includes a ballast circuit 1007 that provides additional control of the load current. The circuit 1007 is connected in series with the

switches

301, 302. The ballast circuit 1007 is controlled by the control circuit 107 and is connected to the switch control circuit 107 through 1008. The connection 1008 may be a wired or wireless connection to the control circuitry 107.

In one embodiment shown in fig. 11, the ballast circuit 1007 comprises a ballast resistor 1101 and a switch 1102 wired in parallel. Switch 1102 is controlled by control circuit 107 via connection 1108. In one embodiment for dimming LED lighting, the switch 1102 is normally closed (close) and opens (open) when dimming to 0% output, so that the ballast resistor 1101 reduces the current through the connected LED load to less than the threshold required to illuminate the LED. In one embodiment, switch 1102 is a relay switch. In another embodiment, the control line 1008 is a wireless connection to the control circuitry 107.

Summary of the invention

A bi-directional switch and dimmer for controlling power to a load from an AC source is described. The method uses power MOSFETs in a bidirectional switch sub-circuit configuration that includes a floating AC/DC power supply and a solid state bipolar switch that alternates between connection of an AC source to a load and periodic connection of the AC source to the AC/DC power supply. The switch and dimmer circuit configuration allows for the use of only two wires to be plugged into an existing single phase circuit. This design allows the entire circuit to be fabricated on a single chip.

Claims

1. A bidirectional electronic switching system (400), the bidirectional electronic switching system (400) for switching current in an Alternating Current (AC) circuit between an AC source (101) having first and second terminals and a load (102) having first and second terminals, the bidirectional electronic switching system comprising:

a. an input terminal (103) and an output terminal (104), the input terminal (103) being connected to a first terminal of an AC source (101) and the output terminal (104) being connected to a first terminal of a load (102), and wherein a second terminal (105) of the AC source (101) and the second terminal of the load (102) are interconnected outside the bidirectional switching system, and

an AC-to-DC conversion system (106), the AC-to-DC conversion system (106) having a first input terminal (402) and a second input terminal (403) for providing energy from the AC source (101) in Direct Current (DC) to a first output terminal (404) and a second output terminal (405), the first output terminal (404) and the second output terminal (405) being connected to control circuitry (107), and

c. the control circuitry (107), the control circuitry (107) having a first output terminal (408) and a second output terminal (409) for providing a control signal to the electronic switch (401), an

d. The electronic switch (401), the electronic switch (401) being connected between the input terminal (103) and a bidirectional switch output terminal (104); wherein the state of the control signal present between the control system output terminals (408, 409) determines the state of the switch.

2. The bi-directional electronic switching system of claim 1 wherein said AC to DC conversion system comprises:

a. a voltage divider (501, 502), the voltage divider (501, 502) being connected across the control circuitry (107), an

b. A first switch (503), the first switch (503) having an input (510) and an output (511), the first switch (503) being connected to the voltage divider by its input (510), an

c. A second switch (506), the second switch (506) having an input (512) and an output (513), the input (512) of the second switch (506) being connected to the output (511) of the first switch (503) through a current limiting resistor (505), and

d. a storage capacitor (208), the storage capacitor (208) being connected to the output (513) of the second switch (506) through a diode (207), an

e. A Zener diode (508), the Zener diode (508) having a Zener voltage, the Zener diode (508) connected between the input (512) and the output (513) of the second switch (506) and a bypass capacitor (509), the bypass capacitor (509) connected in parallel with the Zener diode (508) clamping the voltage between the input (512) and the output (513) of the second switch (506) to the Zener voltage of the Zener diode (508), and

f. the control circuitry (107), the control circuitry (107) connected to the storage capacitor (208).

3. The AC-to-DC conversion system of claim 2, further comprising a series voltage regulator circuit interposed between the storage capacitor (208) and the control circuitry (107), the series voltage regulator circuit comprising a voltage regulator having a characteristic threshold voltage (Vthreshold) connected to the control circuitry (107) and a bias resistor (1004) _T ) And a zener diode (1005) having a zener voltage (Vz) connected to the bias resistor such that the output voltage to the control circuitry (107) is maintained at V _Z –V _T The bias resistor (1004) is connected across the pass transistor.

4. The AC-to-DC conversion system of claim 2, further comprising a current limiting electronic circuit interposed between the second switch (506) and the storage capacitor (208) to limit current flowing through the second switch (506), the current limiting electronic circuit comprising:

a. a sense resistor (1002), the sense resistor (1002) connected between the output (513) of the second switch (506) and the control circuitry (107), and

b. a bipolar transistor (1001), the bipolar transistor (1001) connected between the control circuitry and the input (512) of the second switch (506).

5. The AC-to-DC conversion system of claim 2 wherein said first switch and said second switch are both N-MOSFETs.

6. The AC-to-DC conversion system of claim 2 wherein said first switch and said second switch are bipolar transistors.

7. The AC-to-DC conversion system of claim 1 wherein all semiconductor devices are fabricated on a single integrated circuit chip.

8. The AC-to-DC conversion system of claim 2, wherein all semiconductor devices are fabricated on a single integrated circuit chip.

9. The AC-to-DC conversion system of claim 4, wherein all semiconductor devices are fabricated on a single integrated circuit chip.

10. A bi-directional electronic switching system according to claim 1 wherein the switch control circuit (107) output signal (408, 409) is pulsed in synchronism with the AC source (101) to provide phase control of the AC power delivered to the load (102).

11. The bi-directional electronic switch system of claim 1, wherein the control circuitry (107) output signal (408, 409) comprises: a pulse train synchronized to the AC source (101), the pulse train having an adjustable pulse width effective to control average current/power delivered to the load (102) to provide a dimming effect for a light source load and speed control for an AC motor load.

12. The system of claim 1, wherein the electronic switch (401) comprises:

a. a third and a fourth electronic switching device (301, 302) connected in series, each switching device having a drain terminal (309, 310), a source terminal (311, 312) and a gate terminal (313, 314), and each of the third and fourth switching devices connected in series having a characteristic threshold voltage between the gate terminal (313, 314) and the source terminal (311, 312), wherein the drain terminal (309) of the third switching device (301) comprises the first input terminal of the solid state bidirectional switch (400) and the drain terminal (310) of the fourth switching device (302) comprises the first output terminal of the solid state bidirectional switch (400), the source terminals (311, 312) of the first and second switching devices (301, 302) are interconnected at a first control terminal (315), and the gate terminals (313, 314) of the first and second switching devices are interconnected at a second control terminal (316).

13. The bidirectional electronic switching system of claim 12, further comprising a ballast circuit (1007), the ballast circuit (1007) connected between the drain terminal (309) of the third switching device (301) and the input terminal (103), the ballast circuit including a fifth switch (1102) and a ballast resistor (1101), the ballast resistor and the fifth switch connected in parallel, and the fifth switch controlled by the electronic control system (107) such that the fifth switch is closed in a first state and current through the bidirectional electronic switching system (400) to the load (102) bypasses the ballast resistor (1101), and the fifth switch is open in a second state and current through the bidirectional electronic switching system (400) to the load (102) is limited by the ballast resistor (1101).