Regulating control for single-ended switching power supply

Regulating control means for a single-ended regulated switching power supply operable from an external energy source providing a source voltage, the power supply being of the type having an output circuit connectable to a load to be supplied and a controllable switch to provide regulation of an electrical output parameter by controlling the duty cycle of the power transferred from the source to the output circuit, the regulating control means comprising:

• a pulse width modulator jointly responsive to the source voltage and the output parameter to be regulated for generating switch activating pulses having a duty cycle related to variations in said source voltage and the output parameter so as to maintain said output parameter at a desired value, said switch activating pulses not exceeding a maximum pulse width;
• an internal power supply circuit for said control means and including energy storage means supplied by current from the source at a restricted rate;
• and
• a start-up circuit for at least temporarily inhibiting switch activation to reduce the frequency of said switch activating pulses when the energy stored in the energy storage means is insufficient to maintain activation of the switch for a duration required to achieve the desired value of the output parameter, thereby to limit the source current utilized for the operation of the regulating control means during start-up.

Regulating control means for a single-ended regulated switching power supply operable from an external energy source and of the type having an output circuit connectable to a load to be supplied and a controllable switch to provide regulation of an electrical output parameter by controlling the duty cycle of the power transferred from the source to the output circuit, the regulating control means comprising:

• means jointly responsive to the source voltage and the output parameter to be regulated for generating a signal for activating the switch at a given normal repetition rate, the duration of each activation being variable in accordance with the source voltage and the output parameter so as to maintain said output parameter at the desired value during normal operation;
• an internal power supply circuit for said regulation control means including means to limit the current drawn from the energy source, a capacitor for receiving said limited current and connected to supply energy to the components of the regulating control means, and voltage reference means for maintaining the voltage at said capacitor at a selected value;
• energy storage means in circuit with the switch for storing a portion of the energy transferred through said switch during one portion of the repetition rate cycle and connected to supply said capacitor with supplemental energy during another portion of said cycle, thereby to charge said capacitor to a higher level upon successive periods of switch conduction;
• and
• means for inhibiting switch activation to thereby extend the off-time period between successive activations of said switch when the energy stored in said power supply circuit is less than a prescribed minimum value.

Regulating control means for a single-ended regulated switching power supply operable from an external energy source and of the type having an output circuit connectable to a load to be supplied, and a controllable switch to provide regulation of an electrical output parameter by controlling the duty cycle of the power transferred from the source to the output circuit, the regulating control means comprising:

• a time base signal generator defining a desired period of conduction for said switch at a specified switching rate, said rate establishing a normal time base period T.sub.p constituted of a maximum switch conduction period t.sub.max and a switch non-conduction period t.sub.off ;
• switch activation signal means jointly responsive to the source voltage and the electrical output parameter to be regulated for generating a switch activation pulse for each period T.sub.p having a duration which is variable in accordance with the source voltage and the output parameter so as to maintain said output parameter at the desired value,
• said switch activation signal means including a first circuit for developing a first signal varying generally linearly with time as a function of said source voltage and time-referenced to said period T.sub.p,
• a second circuit for developing a second signal whose magnitude is representative of the output parameter, and
• means jointly responsive to said first and second signals and providing said switch activation signal when the magnitude of one of said first and second signals is less than the magnitude of the other of said signals,
• the range of variaton of said signals being such as to restrict the duration of said switch activation signal to a value less than said maximum period t.sub.max under normal operating conditions;
• and
• means for restricting the maximum duration of said switch activation signal to said maximum period t.sub.max of said time base signal.

Regulating control means for a single-ended regulated switching power supply operable from an external energy source having a source voltage, said regulating control means being of the type having an output circuit connectable to a load to be supplied, and a controllable switch to provide regulation of an output power parameter by controlling the duty cycle of the power transferred from the source to the output circuit, regulating control means comprising:

• means jointly responsive to the source voltage and the power output parameter to be regulated for generating a switch activation signal having a normally fixed pulse frequency and a pulse duration variable in accordance with the source voltage and the output power parameter so as to maintain said output power parameter at a desired value;
• current limiting means responsive to incremental output current in excess of a prescribed maximmm value under excess load conditions for developing a current limiting signal;
• and
• means coupling said current limiting signal to said switch activation signal generating means so as to reduce the duty cycle of switch activation at said fixed pulse frequency, said current limiting means including
• an output-voltage sensing circuit providing a voltage reference signal variable in accordance with output voltages less than a given control level,
• a current sensing circuit for developing a signal that is a function of output current;
• and
• means responsive to said voltage reference and current function signals for generating said current limiting signal when the magnitudes of said signals have a predetermined relationship,
• said current limiting means being operative to reduce the output voltage and thereby maintain output current at a constant maximum value for output voltages exceeding said control level,
• said current limiting signal being generated at relatively lower output current values when said output voltage is less than said given control level so as to reduce the regulated output current to a value less than said maximum value.