System and method to enhance signal to noise ratio and to achieve minimum duty cycle resolution for peak current mode control scheme

A peak current mode control (PCMC) controller for a power converter, the power converter comprising a main transformer having a primary winding and a secondary winding, the primary winding electrically coupleable to an input voltage node and electrically coupled to a main switch, the secondary winding electrically coupleable to an output voltage node, the PCMC controller comprising:

• a control output node electrically coupled to a main switch control node of the main switch to control the operation of the main switch;
• a current sense input node to receive a current signal indicative of a current of the main switch;
• and
• a current sense circuit, comprising:
• a current sense resistor electrically coupled in series with the main switch;
• a filter resistor comprising a first terminal and a second terminal, the first terminal electrically coupled to a node between the current sense resistor and the main switch, and the second terminal electrically coupled to the current sense input node;
• a filter capacitor electrically coupled to the current sense input node;
• and
• a main switch control node resistor comprising a first terminal and a second terminal, the first terminal directly electrically coupled to the main switch control node, and the second terminal directly electrically coupled to the current sense input node such that, in operation, the main switch control node resistor resets the filter capacitor each time the main switch is turned off before a next turn-on cycle to maximize the ability of the filter capacitor to absorb a spike at the current sense input node caused by turning on the main switch during the next turn-on cycle.

A power converter, comprising:

• a transformer having a primary winding and a secondary winding, the primary winding electrically coupleable to an input voltage node and the secondary winding electrically coupleable to an output voltage node;
• a primary circuit electrically coupled to the primary winding, the primary circuit comprising a main switch;
• a peak current mode control (PCMC) controller, comprising:
• a control output node electrically coupled to a main switch control node of the main switch to control the operation of the main switch;
• a current sense input node to receive a current signal indicative of a current of the main switch;
• and
• a current sense circuit, comprising:
• a current sense resistor electrically coupled in series with the main switch;
• a filter resistor comprising a first terminal and a second terminal, the first terminal electrically coupled to a node between the current sense resistor and the main switch, and the second terminal electrically coupled to the current sense input node;
• a filter capacitor electrically coupled to the current sense input node;
• and
• a main switch control node resistor comprising a first terminal and a second terminal, the first terminal directly electrically coupled to the main switch control node, and the second terminal directly electrically coupled to the current sense input node such that, in operation, the main switch control node resistor resets the filter capacitor each time the main switch is turned off before a next turn-on cycle to maximize the ability of the filter capacitor to absorb a spike at the current sense input node caused by turning on the main switch during the next turn-on cycle.