Direct-current power supply circuit having control sections with at least one control section having priority over another control section

• US 6,262,903 B1
• Filed: 12/23/1999
• Issued: 07/17/2001
• Est. Priority Date: 12/24/1998
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Kitamura, Tetsuyasu, Fujihashi, Yoshinori, Harada, Takuya
• Primary Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US09/471,231
• Time in Patent Office: 572 Days
• Field of Search: 363/84, 363/89, 363/125, 363/126, 363/127
• US Class Current: 363/89
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer
• CPC Class Codes: H02M 7/1557 with automatic control of the output voltage or current

Abstract

A direct-current power supply circuit, incorporated in an IC card, includes a coil for receiving an amplitude-modulated signal from an external device through electromagnetic induction. A full-wave rectifying circuit rectifies the amplitude-modulated signal received by the coil. The rectified output signal is used to charge a smoothing capacitor. A clamp circuit controls the terminal voltage of the smoothing capacitor to a predetermined level so as to produce a power supply voltage. The clamp circuit controls an output transistor to stabilize the power supply voltage to a constant level. Furthermore, the direct-current power supply circuit includes a short-circuit preventing circuit to forcibly turn off the output transistor when the electric potential difference between both ends of the coil is smaller than a predetermined value, thereby preventing the power supply voltage from suddenly decreasing due to delay of operation of the circuit elements when the coil output becomes zero due to amplitude modulation.

Claims

1. A direct-current power supply circuit comprising:

a signal receiving section for receiving an alternating-current signal from outside of the direct-current power supply circuit;

a rectifying section for rectifying an output of said signal receiving section;

a smoothing section for smoothing an output of said rectifying section;

a first control section for controlling the operation of a switching section to produce a constant voltage, said switching section changing the voltage level of an output of said smoothing section; and

a second control section, connected between said signal receiving section and said first control section, for prohibiting the switching operation of said switching section in accordance with a signal condition of the alternating-current signal received by said signal receiving section, the prohibition of the second control section having priority over the control of said first control section.

2. The direct-current power supply circuit in accordance with claim 1, wherein said second control section prohibits the switching operation of said switching section in response to a change of amplitude modulation of said alternating-current signal received by said signal receiving section.

3. The direct-current power supply circuit in accordance with claim 2, wherein said first control section is an analog circuit and said second control section is constituted primarily by a digital circuit.

4. The direct-current power supply circuit in accordance with claim 3, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said first control section is used to activate a semiconductor integrated circuit incorporated in said IC card.

5. The direct-current power supply circuit in accordance with claim 1, wherein

the alternating-current signal received by said signal receiving section is an amplitude-modulated signal changeable up to 100% in the degree of amplitude modulation, and

wherein said second control section prohibits the switching operation of said switching section in response to the change of the amplitude modulation of said alternating-current signal received by said signal receiving section.

6. The direct-current power supply circuit in accordance with claim 5, wherein said first control section is an analog circuit and said second control section is constituted primarily by a digital circuit.

7. The direct-current power supply circuit in accordance with claim 6, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said first control section is used to activate a semiconductor integrated circuit incorporated in said IC card.

8. A direct-current power supply circuit comprising:

a coil for receiving an alternating-current signal from outside of the direct-current power supply circuit;

a rectifying circuit for rectifying an output of said coil;

a capacitor for smoothing an output of said rectifying circuit;

a clamp circuit for controlling the operation of a switching element to produce a constant voltage, said switching element controlling the charging and discharging operations of said capacitor; and

a switching operation control circuit, connected between said coil and said clamp circuit, for executing an turning-off operation of said switching element in accordance with a signal condition of the alternating-current signal received by said coil, said turning-off operation of said switching element having priority over the control of said clamp circuit.

9. The direct-current power supply circuit in accordance with claim 8, wherein said switching operation control circuit executes the turning-off operation of said switching element in response to a change of amplitude modulation of said alternating-current signal received by said coil.

10. The direct-current power supply circuit in accordance with claim 9, wherein said clamp circuit is an analog circuit and said switching operation control circuit is constituted primarily by a digital circuit.

11. The direct-current power supply circuit in accordance with claim 10, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said clamp circuit is used to activate a semiconductor integrated circuit incorporated in said IC card.

12. The direct-current power supply circuit in accordance with claim 8, wherein

the alternating-current signal received by said coil is an amplitude-modulated signal changeable up to 100% in degree of amplitude modulation, and

wherein said switching operation control circuit executes the turning-off operation of said switching element in response to the change of the amplitude modulation of said alternating-current signal received by said coil.

13. The direct-current power supply circuit in accordance with claim 12, wherein said clamp circuit is an analog circuit and said switching operation control circuit is constituted primarily by a digital circuit.

14. The direct-current power supply circuit in accordance with claim 13, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said clamp circuit is used to activate a semiconductor integrated circuit incorporated in said IC card.

15. A direct-current power supply circuit comprising:

a coil for receiving an alternating-current signal from the outside of the direct-current power supply circuit;

a rectifying circuit for rectifying an output of said coil;

a smoothing capacitor for smoothing an output of said rectifying circuit; and

a clamp circuit for controlling a terminal voltage of said smoothing capacitor to a predetermined constant voltage, said clamp circuit including an output transistor connected in parallel with said smoothing capacitor;

wherein said clamp circuit includes a short-circuit preventing circuit which prevents said output transistor from short-circuiting both ends of said smoothing capacitor when an electric potential difference between both ends of said coil is smaller than a predetermined value.

16. The direct-current power supply circuit in accordance with claim 15, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read,

said coil receives an amplitude-modulated signal for data communication through electromagnetic coupling with an external apparatus, and

said direct-current power supply circuit produces a power supply voltage for activating a semiconductor integrated circuit accommodated in said IC card.

17. The direct-current power supply circuit in accordance with claim 15, wherein said short-circuit preventing circuit is a logic circuit.

18. The direct-current power supply circuit in accordance with claim 15, wherein said short-circuit preventing circuit forcibly turns off said output transistor when the electric potential difference between both ends of said coil is smaller than the predetermined value.

19. The direct-current power supply circuit in accordance with claim 18, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read,

said coil receives an amplitude-modulated signal for data communication through electromagnetic coupling with an external apparatus, and

said direct-current power supply circuit produces a power supply voltage for activating a semiconductor integrated circuit accommodated in said IC card.

20. The direct-current power supply circuit in accordance with claim 18, wherein said short-circuit preventing circuit is a logic circuit.

21. The direct-current power supply circuit in accordance with claim 15, wherein

said short-circuit preventing circuit comprises an auxiliary transistor connected in series with said output transistor, and said auxiliary transistor and said output transistor are connected in parallel with said smoothing capacitor,

and said short-circuit preventing circuit turns off said auxiliary transistor when the electric potential difference between both ends of said coil is smaller than the predetermined value.

22. The direct-current power supply circuit in accordance with claim 21, wherein

the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read,

said coil receives an amplitude-modulated signal for data communication through electromagnetic coupling with an external apparatus, and

said direct-current power supply circuit produces a power supply voltage for activating a semiconductor integrated circuit accommodated in said IC card.

23. A direct-current power supply circuit comprising:

a signal receiving section for receiving an amplitude modulated alternating-current signal from outside of the direct-current power supply circuit;

a rectifying section for rectifying an output of said signal receiving section;

a smoothing section for smoothing an output of said rectifying section;

a first control section for controlling operation of a switching section to produce a constant voltage, said switching section changing the voltage level of an output of said smoothing section; and

a second control section connected between said signal receiving section and said first control section to directly detect said amplitude modulated alternating-current signal from said signal receiving section, said second control section prohibiting the switching operation of said switching section in accordance with a signal condition of detected amplitude modulated alternating-current signal, the prohibition of the second control section having priority over the control of said first control section.

24. The direct-current power supply circuit in accordance with claim 23, wherein said second control section prohibits the switching operation of said switching section in response to a change of amplitude modulation of said alternating-current signal received by said signal receiving section.

25. The direct-current power supply circuit in accordance with claim 24, wherein said first control section is an analog circuit and said second control section is constituted primarily by a digital circuit.

26. The direct-current power supply circuit in accordance with claim 25,

wherein the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said first control section is used to activate a semiconductor integrated circuit incorporated in said IC card.

27. The direct-current power supply circuit in accordance with claim 23,

wherein said amplitude modulated alternating-current signal received by said signal receiving section is changeable up to 100% in degree of amplitude modulation, and

wherein said second control section prohibits the switching operation of said switching section in response to the change of the amplitude modulation of said amplitude modulated alternating-current signal received by said signal receiving section.

28. A direct-current power supply circuit comprising:

a signal receiving section for receiving an alternating-current signal from outside of the direct-current power supply circuit;

a rectifying section for rectifying an output of said signal receiving section;

a smoothing section for smoothing an output of said rectifying section;

a first control section for controlling operation of a switching section to produce a constant voltage, said switching section changing the voltage level of an output of said smoothing section; and

a second control section connected between said signal receiving section and said first control section for prohibiting the switching operation of said switching section in accordance with a signal condition of the alternating-current signal received by said signal receiving section, the prohibition of the second control section having priority over the control of said first control section,

wherein said second control section prohibits the switching operation of said switching section in response to a change of amplitude modulation of said alternating-current signal received by said signal receiving section, and

wherein said first control section is an analog circuit and said second control section is constituted primarily by a digital circuit.

29. A direct-current power supply circuit comprising:

a coil for receiving an amplitude modulated alternating-current signal from outside of the direct-current power supply circuit;

a rectifying circuit for rectifying an output of said coil;

a capacitor for smoothing an output of said rectifying circuit;

a clamp circuit for controlling the operation of a switching element to produce a constant voltage, said switching element controlling charging and discharging operations of said capacitor; and

a switching operation control circuit connected between said coil and said clamp circuit to directly detect said amplitude modulated alternating-current signal from said coil, said switching operation control circuit executing a turning-off operation of said switching element in accordance with a signal condition of detected amplitude modulated alternating-current signal, said turning-off operation of said switching element having priority over the control of said clamp circuit.

30. The direct-current power supply circuit in accordance with claim 29, wherein said switching operation control circuit executes the turning-off operation of said switching element in response to a change of amplitude modulation of said alternating-current signal received by said coil.

31. The direct-current power supply circuit in accordance with claim 29, wherein said clamp circuit is an analog circuit and said switching operation control circuit is constituted primarily by a digital circuit.

32. The direct-current power supply circuit in accordance with claim 31,

wherein the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said first control section is used to activate a semiconductor integrated circuit incorporated in said IC card.

33. The direct-current power supply circuit in accordance with claim 29,

wherein said amplitude modulated alternating-current signal received by said coil is changeable up to 100% in degree of amplitude modulation, and

wherein said switching operation control circuit executes the turning-off operation of said switching element in response to the change of the amplitude modulation of said amplitude modulated alternating-current signal received by said coil.

34. The direct-current power supply circuit in accordance with claim 33, wherein said clamp circuit is an analog circuit and said switching operation control circuit is constituted primarily by a digital circuit.

35. The direct-current power supply circuit in accordance with claim 34,

wherein the direct-current power supply circuit is incorporated in an IC card to or from which information is written or read, and

wherein the constant voltage produced by said first control section is used to activate a semiconductor integrated circuit incorporated in said IC card.

36. A direct-current power supply circuit comprising:

a coil for receiving an alternating-current signal from outside of the direct-current power supply circuit;

a rectifying circuit for rectifying an output of said coil;

a capacitor for smoothing an output of said rectifying circuit;

a clamp circuit for controlling the operation of a switching element to produce a constant voltage, said switching element controlling charging and discharging operations of said capacitor; and

a switching operation control circuit, connected between said coil and said clamp circuit, for executing a turning-off operation of said switching element in accordance with a signal condition of the alternating-current signal received by said coil, said turning-off operation of said switching element having priority over the control of said clamp circuit,

wherein said switching operation control circuit executes the turning-off operation of said switching element in response to a change of amplitude modulation of said alternating-current signal received by said coil, and

wherein said clamp circuit is an analog circuit and said switching operation control circuit is constituted primarily by a digital circuit.