Waveform shaping circuit for spurious harmonic suppression
A lighting system waveform shaping circuit (WSC) includes a line voltage input, a line voltage output connectable to an input voltage port of a control unit, a neutral line input connectable to a neutral line of a voltage power source, and the WSC including an impedance matching network (IMN) configured to alter an input impedance of the lighting control circuit. In one embodiment, the IMN can include a resistor in series with the line voltage input, and an actively-controlled bypass switch in parallel with the resistor. In another embodiment, the IMN can include respective ferrite chokes surrounding the input and the output voltage lines, a capacitor between the line voltage input and the neutral line input, a capacitor between the neutral line input and a protected earth ground, and a resistor in series between the neutral line input and the lighting control unit neutral line input port.
1. A waveform shaping circuit for a lighting system that includes a lighting control unit and at least one luminaire, and a data concentrator unit (DCU) in wireless communication with the lighting control unit,
the waveform shaping circuit external to the lighting control unit and in serial electrical communication with input terminals of the lighting control unit;
the waveform shaping circuit comprising:
a line voltage input connectable to a line voltage power source;
a line voltage output, the line voltage output connectable to an input voltage port of the lighting control unit;
a neutral line input connectable to a neutral line of the line voltage power source;
the waveform shaping circuit including an impedance matching network configured to alter an input impedance of the lighting control circuit; and
the waveform shaping circuit including a capacitive element connected from the neutral line to a protected earth ground, the capacitive element configured to bypass spurious harmonics generated by operation of the lighting control unit.
2. The waveform shaping circuit of claim 1 , including a neutral line output connectable to a neutral line input port of the lighting control unit.
3. The waveform shaping circuit of claim 1 , the impedance matching network including:
a resistor in series with the line voltage input; and
a bypass switch in parallel with the resistor.
4. The waveform shaping circuit of claim 3 , including the bypass switch actively controlled by the lighting control unit, wherein the lighting control unit activates the bypass switch during periods of lighting control unit inactivity.
5. The waveform shaping circuit of claim 2 , the impedance matching network including:
a first ferrite choke surrounding the line voltage input and the neutral line input;
a second ferrite choke surrounding the lighting control unit input line voltage port and the lighting control unit neutral line input port;
a shunt capacitor located between the line voltage input and the neutral line input;
a bypass capacitor located between the neutral line input and a protected earth ground; and
a resistor in series between the neutral line input and the lighting control unit neutral line input port.
6. A lighting system comprising:
a lighting control unit in control communication with a luminaire, the lighting control unit including a line voltage input port and a neutral line input port;
a data concentrator unit (DCU) in wireless communication with the lighting control unit;
a waveform shaping circuit external to the lighting control unit and in serial electrical communication with input terminals of the lighting control unit;
the waveform shaping circuit comprising:
a line voltage input connectable to a line voltage power source;
a line voltage output, the line voltage output connectable to the lighting control unit input voltage port;
a neutral line input connectable to a neutral line of the line voltage power source;
the waveform shaping circuit including an impedance matching network configured to alter an input impedance of the lighting control circuit; and
the waveform shaping circuit including a capacitive element connected from the neutral line to a protected earth ground, the capacitive element configured to bypass spurious harmonics generated by operation of the lighting control unit.
7. The lighting system of claim 6 , the waveform shaping circuit including a neutral line output connectable to the lighting control unit neutral line input port.
8. The lighting system of claim 6 , the impedance matching network including:
a resistor in series with the line voltage input; and
a bypass switch in parallel with the resistor.
9. The lighting system of claim 8 , including the bypass switch actively controlled by the lighting control unit, wherein the lighting control unit activates the bypass switch during periods of lighting control unit inactivity.
10. The lighting system of claim 7 , the impedance matching network including:
a first ferrite choke surrounding the line voltage input and the neutral line input;
a second ferrite choke surrounding the lighting control unit input line voltage port and the lighting control unit neutral line input port;
a shunt capacitor located between the line voltage input and the neutral line input;
a bypass capacitor located between the neutral line input and a protected earth ground; and
a resistor in series between the neutral line input and the lighting control unit neutral line input port.
11. A lighting system comprising:
a lighting control unit in control communication with a luminaire, the lighting control unit including a line voltage input port and a neutral line input port;
a data concentrator unit (DCU) in wireless communication with the lighting control unit;
a waveform shaping external to the lighting control unit and in serial electrical communication with input terminals of the lighting control unit;
the waveform shaping circuit comprising:
a line voltage input connectable to a line voltage power source,
a line voltage output, the line voltage output connectable to the lighting control unit input voltage port,
a neutral line input connectable to a neutral line of the line voltage power source, and
a neutral line output connectable to the lighting control unit neutral line input port;
the waveform shaping circuit including an impedance matching network configured to alter an input impedance of the lighting control circuit;
the impedance matching network is selected from the group consisting of:
a first impedance matching network that includes a resistor in series with the line voltage input of the waveform shaping unit and a bypass switch in parallel with the resistor; and
a second impedance matching network that includes a first ferrite choke surrounding the line voltage input and the neutral line input of the waveform shaping unit, a second ferrite choke surrounding the lighting control unit input line voltage port and the lighting control unit neutral line input port, a shunt capacitor located between the line voltage input and the neutral line input, a bypass capacitor located between the neutral line input and a protected earth ground, and a resistor in series between the neutral line input and the lighting control unit neutral line input port; and
the shunt capacitor configured to bypass spurious harmonics generated by operation of the lighting control unit.