Primary side constant current regulation

A current sense circuit, comprising:

• a first sense diode having a first diode anode and a first diode cathode;
• wherein the first diode anode is grounded;
• and
• wherein the first diode cathode is connected to a second terminal of a first coil of a transformer having an operating frequency (TSW);
• wherein the first coil includes a first terminal coupled to an input voltage and received at an input current (IP);
• wherein the transformer includes a second coil coupled to at least one output node providing an output voltage and an output current (IO);
• a second sense diode having a second diode anode and a second diode cathode;
• a sensing resistor providing a sense resistance;
• a sensing capacitor;
• wherein the sensing resistor and the sensing capacitor are grounded;
• wherein the second diode anode is connected to the second terminal and the second diode cathode is connected, in parallel, to the sensing resistor, the sensing capacitor, and the compensating resistor at a voltage sense node;
• a voltage reference regulator configured to operate at a reference voltage (VREF), comprising:
• a ground node;
• a first reference node;
• and
• a second reference node;
• a set resistor having a set resistance;
• wherein the set resistor is configured to receive a sensed voltage (VS);
• a compensating resistor having a compensating resistance;
• wherein the compensating resistor is connected, in parallel, at the first reference node, to the set resistor;
• a source resistor, connected in series to the second reference node and to a source voltage (VCC);
• a feedback diode having a cathode coupled to the second reference node and an anode coupled to a feedback resistor;
• wherein the feedback resistor is coupled to a resonant circuit controller of a resonant circuit;
• and
• wherein the resonant circuit controller is configured to adjust the operating frequency of the transformer, based upon a feedback signal received from the current sense circuit to maintain a constant output current over multiple cycles of the transformer.

A circuit for primary side regulation of a constant output current resonant transformer, comprising:

• a transformer having a first coil and a second coil;
• wherein a coil ratio (N) defines the first coil relative to the second coil;
• wherein the first coil has a first terminal and a second terminal;
• wherein the second coil generates an output current (IO) and an output voltage (VO);
• a controller circuit configured to receive an input voltage (VIN);
• a resonant circuit coupling the controller circuit with the first terminal;
• a current sense circuit coupled to the second terminal and the controller circuit;
• wherein the current sense circuit is configured to detect fluctuations in a sensed resulting voltage potential (VCS);
• wherein the fluctuations are representative of the output current (IO) of the transformer;
• wherein the current sense circuit is configured to provide a feedback signal to the controller circuit when the sensed resulting voltage potential (VCS) is greater than a reference voltage;
• and
• wherein the feedback signal is representative of both the output current (IO) and the output voltage (VO) of the transformer.