SWITCHING CONTROL CIRCUITS AND METHOD OF ACTUATING A SWITCH HAVING REDUCED CONDUCTED EMI
The present disclosure provides a control circuit to power a load, the circuit generally comprising a first switch such as a TRIAC to switch on and off and power the load based upon user demand. The circuit is also comprised of a second connected in parallel with the TRIAC, the second switch switching to a conducting state at a zero-crossing of the source before becoming completely saturated. Once the second switch is saturated, the first switch switches from a non-conducting state to a conducting state, which minimizes conducted EMI generated in the circuit.
1 . A control circuit to control power to a load, comprising:
a first switch connected to a power source, the switch configured to switch from a first non-conducting state to a second conducting state;
an energy bank electrically connected to the first switch, the energy bank to store energy and power a device when the first switch is in the second conducting state;
a zero-crossing (ZC) detection circuit electrically connected to detect a zero-crossing of the power source,
a second switch in parallel electrical connection with the first switch, the slow linear switch activated after the zero-crossing of the power source.
2 . The control circuit of claim 1 wherein the first switch is a triode for alternating current (TRIAC).
3 . The control circuit of claim 1 wherein the first switch is further comprised of a switch activation circuit.
4 . The control circuit of claim 1 wherein the slow linear switch is further comprised of an SLS activation circuit.
5 . The control circuit of claim 1 further comprised of a diode electrically connected to the slow linear switch to ensure that the energy bank does not discharge when the slow linear switch is activated.
6 . The control circuit of claim 1 further comprised of a half wave rectifier diode.
7 . The control circuit of claim 1 wherein the slow linear switch is actuated before the first switch switches from the first non-conducting state to the second conducting state to reduce conducted electromagnetic interference of the control circuit.
8 . The control circuit of claim 7 further comprised of a second energy bank connected in between a gate and a source of the slow linear switch.
9 . The control circuit of claim 7 wherein the slow linear switch is activated during a period of time, whereby a voltage V GS of the slow linear switch is increasing slowly to reduce conducted electromagnetic interference of the control circuit.
10 . A method of activating a first switch, the steps comprising:
detecting a zero-crossing of a power source;
actuating a second switch after the zero-crossing of the power source; and,
actuating the first switch after the second switch is completely saturated to reduce conducted electromagnetic interference of a control circuit.
11 . The method of claim 10 wherein the second switch is a slow linear switch.
12 . The method of claim 10 wherein the second switch is actuated before the first switch switches from the first non-conducting state to the second conducting state.
13 . The method of claim 10 wherein the second switch is activated during a period of time, whereby a voltage V GS of the second switch gradually increases.