AC to DC power supply circuit

• US 4,051,425 A
• Filed: 02/03/1975
• Issued: 09/27/1977
• Est. Priority Date: 02/03/1975
• Status: Expired due to Term

• Current Assignee: Telephone Utilities and Communications Industries Incorporated
• Original Assignee: Telephone Utilities and Communications Industries Incorporated
• Inventors: Smith, Jerry L.
• Primary Examiner(s): Shoop, William M.
• Application Number:
  US05/546,555
• Time in Patent Office: 967 Days
• Field of Search: 321/11, 321/14, 321/18, 321/24, 321/21, 321/25, 323/7, 323/24
• US Class Current: 363/86
• CPC Class Codes: H02M 1/092 the control signals being transmitted optically
• CPC Class Codes: H02M 3/315 using semiconductor devices only
• CPC Class Codes: H02M 5/253 using discharge tubes only
• CPC Class Codes: H02M 7/066 particular circuits having a special characteristic

Abstract

An electrical power supply circuit for converting alternating circuit power into a direct current output comprises a transformer and rectifier, a filter capacitor across the output terminals and a phase control switching device and a non-saturating inductor in the primary circuit. The circuit arrangement reduces the volt-time integral of the transformer and allows its core to be made of a smaller size, in comparison to the transformer cores of previously known power supplies, without danger of saturation. Other advantages such as low RFI, reduced transformer wire size and overload current protection are obtained. A commutator circuit may also be provided for turning off the phase control switching device before the end of the associated half cycle of input voltage to further reduce the transformer volt-time integral and to accordingly allow a further reduction in its core size.

Claims

1. A power supply circuit for converting alternating current power into a voltage regulated direct current output, said power supply circuit comprising a pair of input terminals for connection to a source of AC power and a pair of output terminals for connection to a DC load, a transformer with a primary winding and a secondary winding, a phase control switching means an an inductor connected in series with one another and with said primary winding across said input terminals, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, and a voltage regulating means responsive to the DC output voltage appearing across said output terminals for controlling the firing angle of said phase control switching means so as to maintain said DC output voltage at a desired value, said inductor being one which does not saturate during any half cycle of the voltage waveform of said AC power source even when said output terminas are shorted, and said transformer having a core of an optimally small size capable of supporting volt-time integrals associated with normal firing angles without saturating but incapable of supporting volt-time integrals associated with abnormally small firing angles whereby said core is of substantially smaller size than the size required to support volt-time integrals associated with such abnormally small firing angles and whereby in the event of said core saturating said inductor imposes an impedance to limit current through said primary winding.

2. A power supply circuit as defined in claim 1 further characterized by said rectifier being a full wave rectifier, and said phase control switching means being a bidirectional switching means for switching AC power from said input terminals to said primary winding during each half cycle of the AC input voltage applied across said input terminals.

3. A power supply circuit as defined in claim 1 further characterized by said bidirectional phase control switching means being a bistable switching component having for each direction of current flow therethrough a conducting and a non-conducting state, said bistable switching component also having a gate terminal and being one which is switched from its non-conducting to its conducting state by a trigger pulse signal applied to said gate terminal.

4. A power supply circuit as defined in claim 3 further characterized by said voltage regulating means comprising a voltage regulator circuit connected across said output terminals for developing an electrical signal which varies in accordance with the DC output voltage appearing across said output terminals, a trigger circuit connected across said input terminals for developing, during each half cycle of the AC input voltage applied across said input terminals, a trigger pulse signal for triggering said bistable switching component from its non-conducting to its conducting state, said trigger circuit being coupled with said electrical signal of said voltage regulator and being responsive thereto to control the timing of the trigger pulse signal produced during each of said half cycles.

5. A power supply circuit as defined in claim 4 further characterized by said electrical signal of said voltage regulator being coupled with said trigger circuit through an electrically isolating coupler so as to electrically isolate said voltage regulator from said trigger circuit.

6. A power supply circuit as defined in claim 2 further characterized by said bidirectional switching device being a triac.

7. A power supply circuit as defined in claim 2 further characterized by said bidirectional switching means comprising a unidirectional switching component and a diode network connected therewith for causing current to be directed through said switching component in the same direction during each half cycle of said AC input voltage.

8. A power supply circuit as defined in claim 7 further characterized by said unidirectional switching component being a transistor.

9. A power supply circuit as defined in claim 8 further characterized by said voltage regulating means comprising a voltage regulator circuit connected across said output terminals for developing an electrical signal which varies in accordance with the DC output voltage appearing across said output terminals, a drive signal circuit connected across said input terminals for developing during each half cycle of said input voltage a transistor drive signal applied to the control terminal of said transistor for controlling its conduction and which transistor drive signal switches from an OFF value to an ON value to correspondingly switch the transistor from a non-conducting state to a conducting state during each of said half cycles, said drive signal circuit being coupled with said electrical signal of said voltage regulator circuit and being responsive thereto control the timing of the switching of said drive signal from said OFF value to said ON value during each of said half cycles.

10. A power supply circuit for converting alternating current power into a direct current output, said power supply circuit comprising a pair of input terminals for connection to a source of AC power and a pair of output terminals for connection to a DC load, a transformer with a primary winding and a secondary winding, a phase control switching means and an inductor connected in series with one another and with said primary winding across said input terminals, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, and a control means for controlling the firing angle of said phase control switching means, said inductor being non-saturating for all firing angles of said phase control switching means, and said transformer having a core of an optimally small size capable of supporting volt-time integrals associated with normal firing angles without saturating but incapable of supporting volt-time integrals associated with abnormally small firing angles whereby said core is substantially smaller size than the size required to support volt-time integrals associated with such abnormally small firing angles and whereby in the event of said core saturating said inductor imposes an impedance to limit current through said primary winding.

11. A power supply circuit for converting alternating current power into a voltage regulated direct current output, said power supply circuit comprising a pair of input terminals for connection to a source of AC power and a pair of output terminals for connection to a DC load, a transformer with a primary winding and a secondary winding, a phase control switching means and an inductor connected in series with one another and with said primary winding across said input terminals, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, and a voltage regulating means responsive to the DC output voltage appearing across said output terminals for controlling the firing angle of said phase control switching means so as to maintain said DC output voltage at a desired value, said inductor being one which does not saturate during any half cycle of the voltage waveform of said AC power source even when said output terminals are shorted, said bidirectional phase control switching means being a bistable switching component having for each direction of current flow therethrough a conducting and a non-conducting state, said bistable switching component also having a gate terminal and being one which is switched from its non-conducting to its conducting state by a trigger pulse signal applied to said gate terminal, said voltage regulating means comprising a voltage regulator circuit connected across said output terminals for developing an electrical signal which varies in accordance with the DC output voltage appearing across said output terminals, a trigger circuit connected across said input terminals for developing, during each half cycle of the AC input voltage applied across said input terminals, a trigger pulse signal for triggering said bistable switching component from its nonconducting to its conducting state, said trigger circuit being coupled with said electrical signal of said voltage regulator and being responsive thereto to control the timing of the trigger pulse signal produced during each of said half cycles, and said electrical signal of said voltage regulator being coupled with said trigger circuit through an optoelectronic isolating coupler so as to electrically isolate said voltage regulator from said trigger circuit.

12. A power supply circuit for converting alternating current power into a voltage regulated direct current output, said power supply circuit comprising a pair of input terminals for connection to a source of AC poer and a pair of output terminals for connection to a DC load, a transformer with a primary winding and a secondary winding, a phase control switching means an an inductor connected in series with one another and with said primary winding across said input terminals, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, and a voltage regulating means responsive to the DC output voltage appearing across said output terminals for controlling the firing angle of said phase control switching means so as to maintain said DC output voltage at a desired value, said inductor being one which does not saturate during any half cycle of the voltage waveform of said AC power source even when said output terminals are shorted, said rectifier being a full wave rectifier, and said phase control switching means being a bidirectional switching means for switching AC power from said input terminals to said primary winding during each half cycle of the AC input voltage applied across said input terminals, said bidirectional switching means comprising a transistor and diode network connected therewith for causing current to be directed through said switching component in the same direction during each half cycle of said AC input voltage, said voltage regulating means comprising a voltage regulator circuit connected across said output terminals for developing an electrical signal which varies in accordance with the DC output voltage appearing across said otput terminals, a output signal circuit connected across said input terminals for developing during each half cycle of said input voltage a transistor drive signal applied to the control terminal of said transistor for controlling its conduction and which transistor drive signal switches from an OFF value to an ON value to correspondingly switch the transistor from a non-conducting state to a conducting state during each of said half cycles, said drive signal circuit being coupled with said electrical signal of said voltage regulator circuit and being responsive thereto to control the timing of the switching of said drive signal from said OFF value to said ON value during each of said half cycles, and said electrical signal of said voltage regulator being coupled with said drive signal circuit through an optoelectronic isolating coupler so as to electrically isolate said voltage regulator from said drive signal circuit.

13. A power supply circuit for converting alternating current power into a voltage regulated direct current output, said power supply circuit comprising a pair of input terminals for connection to a source of AC power and a pair of output terminals for connection to a DC load, a transformer with a primary winding and secondary winding, a phase control switching means and an inductor connected in series with one another and with said primary winding across said input terminals, said inductor being one which does not saturate during any half cycle of the voltage waveform of said AC power source even when said output terminals are shorted, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, a voltage regulating means responsive to the DC output voltage appearing across said output terminals for controlling the firing angle of said phase control switching means so as to maintain said DC output voltage at a desired value, and a commutation circuit connected with said phase control switching means operable after said phase control switching means is turned ON during a given half cycle of the AC input voltage applied across said input terminals for switching said phase control switching means OFF before the end of said given half cycle.

14. A power supply circuit for converting alternating current power into a voltage regulated direct current output, said poer supply circuit comprising a pair of input terminals for connection to a source of AC power and a pair of output terminals for connection to a DC load, a transformer with a primary winding and a secondary winding, a phase control switching means an an inductor connected in series with one another and with said primary winding across said input terminals, a rectifier having an input connected across said secondary winding and an output connected across said two output terminals, a filter capacitor connected across said two output terminals, and a voltage regulating means responsive to the DC output voltage appearing across said output terminals for controlling the firing angle of said phase control switching means so as to maintain said DC output voltage at a desired value, said inductor being one which does not saturate during any half cycle of the voltage waveform of said AC power source even when said output terminals are shorted, said transformer having a core of an optimally small size capable of supporting volt-time integrals associated with normal firing angles without saturating but incapable of supporting volt-time integrals associated with abnormally small firing angles, said phase control switching means being a bi-directional switching means for switching AC power from said input terminals to said primary winding during each half cycle of the AC input voltage applied across said input terminals, said bi-directional switching means comprising a transistor and a diode network connected therewith for causing current to be directed through said transistor in the same direction during each half cycle of said AC input voltage, said voltage regulating means comprising a voltage regulator circuit connected across said output terminals for developing an electrical signal which varies in accordance with the DC output voltage appearing across said output terminals, a drive signal circuit connected across said input terminals for developing during each half cycle of said input voltage a transistor drive signal applied to the control terminal of said transistor for controlling its conduction and which transistor drive signal switches from an OFF value to an ON value to correspondingly switch said transistor from a nonconducting state to a conducting state during each of said half cycles, said drive signal circuit being coupled with said electrical signal of said voltage regulator circuit and being responsive thereto to control the timing of the switching of said drive signal from said OFF value to said ON value during each of said half cycles, and said electrical signal of said voltage regulator being coupled with said drive signal circuit through an electrically isolating coupler so as to electrically isolate said voltage regulator from said drive signal circuit.