Loosely regulated feedback control for high efficiency isolated DC-DC converters

An isolated DC-DC converter system comprising:

• (a) a primary side circuit;
• and
• (b) a secondary side circuit;
• wherein
• said primary side circuit is configured to accept an input voltage;
• said secondary side circuit is configured to generate a secondary output voltage for use by at least one point-of-load device;
• said secondary output voltage is electrically coupled to a main electrical load that is external to said isolated DC-DC converter system;
• said main electrical load comprises a point-of-load (POL) device;
• said secondary side circuit comprises an optocoupler device;
• said secondary side circuit is configured to establish an output voltage loose regulation point based upon a ±4% or greater regulation tolerance in said output voltage;
• said optocoupler device is configured to generate a reflected output voltage in said primary side circuit in response to said loose regulation point;
• said reflected output voltage conforms to a quasi-linear voltage transfer characteristic that is proportional to said output voltage;
• said reflected output voltage is utilized by said primary side circuit to regulate said secondary output voltage toward said loose regulation point.

An isolated DC-DC converter system comprising:

• (a) a primary side circuit comprising:
• (1) primary transformer winding circuit;
• (2) a plurality of primary switching devices for controlling current flow through said primary transformer winding circuit;
• (3) a controller configured to provide a variable duty cycle signal for driving said switching devices;
• and
• (4) a photosensor device electrically coupled to a resistance device, said photosensor device configured to generate a reflected output voltage signal for use by said controller;
• and
• (b) a secondary side circuit;
• wherein
• said secondary side circuit is configured to generate an output voltage;
• said output voltage is electrically coupled to a main electrical load that is external to said isolated DC-DC converter system;
• said main electrical load comprises a point-of-load (POL) device;
• said secondary side circuit comprises a secondary transformer winding inductively coupled to said primary winding;
• said secondary side circuit comprises a light emitter device electrically coupled to a voltage divider circuit, said light emitter device in optical view of said photosensor device;
• said reflected output voltage conforms to a quasi-linear voltage transfer characteristic that is proportional to said output voltage;
• said secondary side output voltage causes said light emitter device to influence said photosensor device to affect generation of said reflected output voltage for use by said controller in adjusting said duty cycle of said primary switching devices;
• and
• at low input voltages that cause said duty cycle to reach a maximum value, said duty cycle is automatically controlled downward from said maximum value during a load-dump to regulate said output voltage to a loose regulation tolerance greater than ±4% of a predefined value and to limit output voltage transients during said load-dump.

An isolated DC-DC converter system comprising:

• (a) an optocoupler device comprising:
• (1) a light emitter;
• and
• (2) a photosensor;
• (b) a primary side circuit comprising:
• (1) a primary transformer winding circuit;
• (2) a plurality of primary switching devices for controlling current flow through said primary transformer winding circuit;
• (3) a controller configured to provide a variable duty cycle signal for driving said primary switching devices;
• and
• (4) a resistance device in the emitter circuit of said photosensor configured to generate a reflected output voltage signal for use by said controller;
• and
• (c) a secondary side circuit;
• wherein
• said secondary side circuit is configured to generate an output voltage;
• said output voltage is electrically coupled to a main electrical load that is external to said isolated DC-DC converter system;
• said main electrical load comprises a point-of-load (POL) device;
• said secondary side circuit comprises:
• (1) secondary transformer winding circuit inductively coupled to said primary transformer winding circuit;
• and
• (2) voltage divider electrically coupled to said light emitter;
• said reflected output voltage conforms to a quasi-linear voltage transfer characteristic that is proportional to said output voltage;
• said secondary side output voltage causes said light emitter to influence said photosensor to affect generation of said reflected output voltage for use by said controller in adjusting the duty cycle of said primary switching devices;
• and
• at low input voltages that cause said duty cycle to reach a maximum value, said duty cycle is automatically controlled downward from said maximum value during a load-dump to regulate said output voltage to a loose regulation tolerance greater than ±4% of a predefined value and to limit output voltage transients during said load-dump.