Regulated ferroresonant power supply with soft start

Claim 2

A regulated DC power supply comprising, in combination, a power transformer including a primary winding for excitation from an externa AC power source, a secondary winding and a resonant winding mounted on a magnetic core, said core having a magnetic shunt between said primary winding and said secondary and resonant windings, a ferrocapacitor connected across said resonant winding, an electronic switch, an inductor, means connecting said switch and said inductor in series across at least a portion of said resonant winding, means for rectifying the voltage across said secondary winding to obtain a DC output, control means for establishing conduction through said electronic switch at a predetermined time in each half cycle to initiate discharging said ferrocapacitor for regulating the DC output, said control means including means for comparing a reference voltage with a voltage proportional to the DC output voltage and means for controlling conduction by said electronic switch in response to such comparison by said comparing means, and timing means for automatically reducing the reference voltage for a predetermined time interval when said primary winding is initially excited from the external AC source, said reduced reference voltage advancing conduction by said electronic switch during each half cycle whereby the voltage across said DC output is initially at a reduced voltage.

Claim 3

A regulated DC power supply, as set forth in claim 1, and including means for adjusting the amount at which the voltage at said DC output is initially reduced.

Claim 4

A regulated DC power supply, as set forth in claim 2, and further including means for generating a voltage proportional to the current delivered by said power supply to a load connected to said output, and means responsive to a preselected maximum load current for causing said comparing means to compare the reference voltage with such voltage proportional to the load current whereby said power supply has a regulated output voltage up to such preselected maximum current and a substantially constant current output for load demands above such preselected maximum current.

Claim 5

A regulated DC power supply, as set forth in claim 1, wherein said comparing means is a differential amplifier.

Claim 6

A regulated DC power supply comprising, in combination, a power transformer including a primary winding for excitation from an external AC power source, a secondary winding and a resonant winding mounted on a magnetic core, said core having a magnetic shunt between said primary winding and said secondary and resonant windings, a ferrocapacitor connected across said resonant winding, an electronic switch, an inductor, means connecting said switch and said inductor in series across at least a portion of said resonant winding, means for rectifying the voltage across said secondary winding to obtain a DC output, and control means for establishing conduction through said electronic switch at a predetermined time in each half cycle to regulate the DC output, said control means including means for automatically advancing the time in each half cycle at which conduction is established through said switch in each half cycle for a predetermined time interval when power is initially applied from the external AC source to said primary winding whereby the DC output is initially at a reduced voltage.

Claim 7

A regulated DC power supply comprising, in combination, a power transformer including a primary winding for excitation from an external AC power source, a secondary winding and a resonant winding mounted on a magnetic core, said core having a magnetic shunt between said primary winding and said secondary and resonant windings, a ferrocapacitor connected across said resonant winding, an electronic switch, an inductor, means connecting said switch and said inductor in series across at least a portion of said resonant winding, means for rectifying the voltage across said secondary winding to obtain a DC output, and control means for establishing conduction through said electronic switch at a predetermined time in each half cycle to regulate the DC output, said control means including means for automatically advancing the time in each half cycle at which conduction is established through said switch in each half cycle for a predetermined time interval when power is initially applied from the external AC source to said primary winding whereby the DC output is initially at a reduced voltage.

Claim 8

A regulated DC power supply comprising, in combination, a power transformer including a primary winding for excitation from an external AC power source, a secondary winding and a resonant winding mounted on a magnetic core, said core having a magnetic shunt between said primary winding and said secondary and resonant windings, a ferrocapacitor connected across said resonant winding, an electronic switch, an inductor, means connecting said switch and said inductor in series across At least a portion of said resonant winding, means for rectifying the voltage across said secondary winding to obtain a DC output, and control means for establishing conduction through said electronic switch at a predetermined time in each half cycle, said control means including means for timing conduction through said electronic switch to maintain a predetermined constant DC output voltage up to a preselected maximum load current, means for advancing conduction by said electronic switch for load demands above such preselected maximum load current to limit the maximum output current from said power supply and means for automatically advancing the time in each half cycle at which conduction is established through said switch in each half cycle for a predetermined time interval when power is initially applied from the external AC source to said primary winding whereby the DC output is initially at a reduced voltage.

Claim 9

A regulated DC power supply comprising, in combination, a power transformer including a primary winding for excitation from an external AC power source, a secondary winding and a resonant winding mounted on a magnetic core, said core having a magnetic shunt between said primary winding and said secondary and resonant windings, a ferrocapacitor connected across said resonant winding, an electronic switch, an inductor, means connecting said switch and said inductor in series across At least a portion of said resonant winding, means for rectifying the voltage across said secondary winding to obtain a DC output, and control means for establishing conduction through said electronic switch at a predetermined time in each half cycle, said control means including means for timing conduction through said electronic switch to maintain a predetermined constant DC output voltage up to a preselected maximum load current, means for advancing conduction by said electronic switch for load demands above such preselected maximum load current to limit the maximum output current from said power supply and means for automatically advancing the time in each half cycle at which conduction is established through said switch in each half cycle for a predetermined time interval when power is initially applied from the external AC source to said primary winding whereby the DC output is initially at a reduced voltage.