Self start flyback power supply

A switching regulator power supply connected to a DC source of rectified AC voltage and having a regulation cycle of operation consisting of an energy storage cycle and an energy transfer cycle, said supply comprising:

• a multivibrator generator circuit having a supply voltage input terminal and an output terminal, said generator circuit generating pulses having a predetermined fixed pulse width at an adjustable frequency rate;
• a start-up circuit for starting the operation of said generator circuit, said circuit being connected to said DC source and to said generator circuit, said start-up circuit including:
• a power switching transistor circuit connected to one end of said DC source and to said generator circuit output terminal, said transistor circuit providing current during said energy storage cycle in response to a corresponding one of said pulses;
• a transformer including:
• a primary winding with one end connected to the other end of said DC source and the other end connected to said power transistor circuit to permit current flow in a first direction during said energy storage cycle and in the other direction during said energy transfer cycle;
• and,
• a feedback primary winding having one end connected to said other end of said DC source and the other end in series with a unidirectional element, said feedback winding having substantially less turns than said primary winding and AC coupled therewith so as to permit current flow through said unidirectional element in said second direction during a first energy storage cycle;
• a series resistor and capacitor network, one end of said resistor connected to said one end of said DC source and the other end of said resistor connected to said unidirectional element and a junction of said resistor and capacitor being connected to an output terminal and the other end of said capacitor being connected to said other end of said DC source;
• and,
• a voltage regulator circuit having input and output terminals, said input terminal connected to said output terminal and said output terminal being connected to said supply voltage input terminal, said voltage regulator circuit being conditioned when said capacitor initially charges proportionally to said AC rectified voltage to generate a first output voltage on said supply voltage input terminal sufficient to cause said multivibrator generator circuit to start generating a first pulse, said power transistor circuit being switched on causing current to flow through said primary winding in said first direction and said feedback primary winding in response to said current flow producing current flow through said unidirectional element in said second direction charging said capacitor to a predetermined voltage within the normal operating range of said regulator circuit within a predetermined time period and said regulator circuit in response to said voltage increasing said first output voltage on said supply voltage for completing the start-up of said multivibrator generator circuit wherein said multivibrator generates pulses having said predetermined pulse width.

A switching regulator power supply connected to a DC source of rectified AC voltage and having a regulation cycle of operation including an energy storage cycle, said supply comprising:

• pulse generator circuit means for generating pulses having a predetermined fixed pulse width defining the duration of said storage cycle;
• and,
• start-up circuit means connected to said DC source and to said pulse generator circuit means, said start-up circuit means including:
• primary transformer winding means connected to said DC source;
• feedback circuit means AC coupled to said primary transformer winding means;
• RC controlled voltage means connected to said DC source, to said primary transformer means, to said feedback circuit means and to said pulse generation means, said RC controlled voltage means including:
• an RC network means consisting of a resistor connected in series with a capacitor, said resistor being connected to said DC source and one end of said capacitor being connected to said feedback circuit means and the other end being connected to a common reference potential;
• and
• a voltage regulator circuit having an input terminal and an output terminal, said input terminal being connected to said capacitor and said output terminal being connected to said pulse generator circuit means, said RC network means in response to said rectified AC voltage conditioning said voltage regulator circuit to apply an output voltage to said pulse generator circuit means to begin operation by generating an output voltage, said output voltage enabling current to flow through said primary transformer means causing said feedback circuit means to generate and apply a feedback voltage to said RC network means for charging said capacitor to a predetermined input voltage, said voltage regulator circuit being conditioned by said RC network means to increase said output voltage to a predetermined value after a predetermined period of time and maintain said output voltage at said predetermined value causing said pulse generator circuit means to operate normally and generate said pulses having said predetermined pulse width.

A switching regulator power supply connected to a DC source of rectified AC voltage and having a regulation cycle of operation including an energy storage cycle, said supply comprising:

• pulse generator circuit means for generating pulses having a predetermined fixed pulse width at a variable frequency rate, said predetermined fixed pulse width defining the duration of said storage cycle, said pulse generator circuit means including a multivibrator circuit having a trigger input terminal and a threshold input terminal connected in common for operating said multivibrator circuit in an astable mode and voltage means;
• start-up circuit means connected to said DC source and to said pulse generator circuit means, said start-up circuit means including:
• primary transformer winding means connected to said DC source, and
• RC controlled voltage means connected to said DC source, to said primary transformer means and to said pulse generator circuit voltage means, said RC controlled voltage means in response to said rectified AC voltage being operative to apply an output voltage to said pulse generator circuit means sufficient to cause said pulse generator circuit means to begin operation by generating an output voltage, said output voltage enabling current to flow through said primary transformer means for generating a feedback voltage for application to said RC controlled voltage means, said voltage means increasing said output voltage to a predetermined value after a predetermined period of time causing said pulse generator circuit to operate normally and generate said pulses having said predetermined pulse width;
• secondary circuit means for providing a desired output voltage to a load, said secondary circuit means being AC coupled to said primary transformer winding means so as to permit current flow in a second predetermined direction opposite to said first predetermined direction during said energy transfer cycle for transferring energy to said load;
• and,
• voltage frequency conversion means, said conversion means including:
• error amplifier means connected to said secondary circuit means, said error amplifier means generating an error voltage indicative of the change in load energy requirements;
• and,
• DC coupling means connected to said error amplifier means and to said voltage means, said DC coupling means being operative in response to said error voltage to inhibit the triggering of said multivibrator so as to vary said frequency for controlling said energy transfer according to said change in load energy requirements.