Electric power device with improved power factor

A switching type electric power device comprising:

• (a) an input rectifying circuit for effecting a full wave rectification on an AC input signal;
• (b) an output converter including a transforming device having a primary winding and a secondary winding, said secondary winding being operatively coupled through an output rectifying circuit including a load, said primary winding being operatively coupled at one end through an inductance device and a first diode device to one of paired outputs of said input rectifying circuit, the other end of said primary winding being operatively coupled with the other of said paired outputs of said input rectifying circuit through a first switching element which is controlled by a control circuit to alternately operate between ON and OFF states to control a flow of current to said primary winding in an ON-OFF manner;
• (c) a capacitance device operatively coupled in parallel with said primary winding and said first switching element so that said capacitance device is discharged through said primary winding during said ON state of said first switching element;
• (d) a second switching element operatively coupled in series to said paired outputs of said input rectifying circuit and said inductance device;
• (e) an ON-OFF control device for controlling said second switching element to alternately operate between ON and OFF states so that said capacitance device is charged during said OFF state through said inductance device and said diode device;
• and
• (f) an interrupting device for preventing over-charge of the capacitance device by overriding said control device in making said second switching element non-conductive when current through said second switching element exceeds a predetermined value, the predetermined value being associated with the voltage of said capacitance device such that the predetermined value is decreased as the voltage of the capacitance device increases and the predetermined value is increased as the voltage of the capacitance device decreases;
• wherein said control circuit controls said first switching element to alternately switch between the ON and OFF states with a frequency that is faster than a frequency of said AC input signal.

A power factor correcting control circuit for use with a switching type electric power device including a power factor correcting circuit, wherein said switching type electric power device comprises:

• (a) an input rectifying circuit for effecting a full wave rectification on an AC input signal;
• (b) an output converter circuit including a transforming device having a primary winding and a secondary winding, the primary winding being operatively coupled to paired outputs of said input rectifying circuit, said secondary winding being operatively coupled to an output rectifying circuit including a load, a first switching element controlled by a control circuit so as to alternately operate between ON and OFF states to thereby control a flow of current to said primary winding in an ON-OFF manner, and a capacitance device, the capacitance device being operatively coupled to said input rectifying circuit and the primary winding of said transforming device so that the capacitance device is charged during said OFF state of said first switching element and the capacitance device is discharged during said ON state of said first switching element through the primary winding of said transforming device;
• and
• (c) a power factor correcting circuit including an energy storage device connected with the paired outputs of said input rectifying circuit and adapted to be controlled by a second switching element, the energy storage device being adapted to store energy which is used to charge said capacitance device under control of said second switching element;
• wherein said control circuit controls said first switching element to alternately operate between said ON and OFF states with a frequency that is faster than a frequency of said AC input signal, and controls said second switching element in synchronized relationship with said first switching element to operate between said ON and OFF states;
• the power factor correcting control circuit comprising:
• (1) a current detecting device for detecting current through said second switching element;
• (2) a comparator device for comparing the current detected by said current detecting device against a predetermined value;
• and,
• (3) a switch for preventing over-charge of the capacitance device by overriding said control circuit in making said second switching element non-conductive when the current detected by the current detecting device exceeds the predetermined value, the predetermined value being associated with the voltage of said capacitance device such that the predetermined value is decreased as the voltage of the capacitance device increases and the predetermined value is increased as the voltage of the capacitance device decreases;
• wherein said current detecting device, said comparator device and said switch are placed on a single board to form a unit.

A power factor correcting control circuit for use with a switching type electric power device including a power factor correcting circuit, wherein said switching type electric power device comprises:

• (a) an input rectifying circuit for effecting a full wave rectification on an AC input signal;
• (b) an output converter circuit including a transforming device having a primary winding and a secondary winding, the primary winding being operatively coupled to paired outputs of said input rectifying circuit, said secondary winding being operatively coupled to an output rectifying circuit including a load, a first switching element controlled by a control circuit so as to alternately operate between ON and OFF states to thereby control a flow of current to said primary winding in an ON-OFF manner, and a capacitance device, the capacitance device being operatively coupled to said input rectifying circuit and the primary winding of said transforming device so that the capacitance device is charged during said OFF state of said first switching element and the capacitance device is discharged during said ON state of said first switching element through the primary winding of said transforming device;
• and
• (c) a power factor correcting circuit including an energy storage device connected with the paired outputs of said input rectifying circuit and adapted to be controlled by a second switching element, the energy storage device being adapted to store energy which is used to charge said capacitance device under control of said second switching element;
• wherein said control circuit controls said first switching element to alternately operate between said ON and OFF states with a frequency that is faster than a frequency of said AC input signal, and controls said second switching element in synchronized relationship with said first switching element to operate between said ON and OFF states;
• the power factor correcting control circuit comprising:
• (1) a current detecting device for detecting current through said second switching element;
• (2) a comparator device for comparing the current detected by said current detecting device against a predetermined value;
• and
• (3) a switch for preventing over-charge of the capacitance device by overriding said control circuit in making said second switching element non-conductive when the current detected by the current detecting device exceeds the predetermined value, the predetermined value being associated with the voltage of said capacitance device such that the predetermined value is decreased as the voltage of the capacitance device increases and the predetermined value is increased as the voltage of the capacitance device decreases;
• wherein at least one of said current detecting device, said comparator device and said switch is placed on a single board to form a unit.