Controller for a switched mode power supply

A switched mode power supply (SMPS), comprising:

• a secondary controller for a secondary side of the SMPS;
• wherein the secondary controller includes,
• a STOP pin, for connecting to both:
• (i) a thermistor, and (ii) an LED of an optocoupler;
• a voltage-supply-pin, which is also for connecting to both:
• (i) the thermistor, and (ii) the LED of the optocoupler, such that the thermistor and the LED of the optocoupler are connected in parallel with each other between the voltage-supply-pin and the STOP pin;
• and
• a reference-source, configured to provide a reference-signal between the STOP pin and the voltage-supply-pin,
• wherein the STOP pin is configured to receive a temperature-measurement-signal from the thermistor due to the reference-signal that is applied to the STOP pin by the reference-source;
• wherein the temperature-measurement-signal is representative of a resistance of the thermistor:
• wherein the secondary controller further includes,
• an OTP-comparator configured to compare:
• (i) the temperature-measurement-signal received at the STOP pin;
• with (ii) a threshold-level, and provide an OTP-signal that is representative of whether or not the temperature-measurement-signal at the STOP pin crosses the threshold-level;
• and
• a switchable-current-source configured to selectively provide a bias-current to the STOP pin based on the OTP-signal, wherein the bias-current is configured to cause the LED to emit a light-signal that is representative of a fault to an associated photo-detector;
• wherein the SMPS further comprises,
• a primary side;
• the secondary side;
• a transformer that provides galvanic isolation between the primary side and the secondary side of the SMPS, wherein the transformer comprises a primary winding and a secondary winding;
• wherein the thermistor is connected between the voltage-supply-pin and the STOP pin of the secondary controller;
• wherein the LED of the optocoupler is connected between the voltage-supply-pin and the STOP pin of the secondary controller;
• wherein the associated photo-detector is on the primary side of the switched mode power supply, and wherein the associated photo-detector is configured to receive the light-signal that is emitted by the LED on the secondary side of the SMPS;
• one or more power switches on the primary side of the switched mode power supply;
• and
• a primary controller that is configured to,
• provide control signals for the one or more power switches to control a power that is put into the primary winding of the transformer;
• and
• perform one or a plurality of different remedial-processes in response to the associated photo-detector receiving the light-signal from the LED.