초록 ▼

The invention relates to a protection circuit (30) which includes at least one switch (FET1, FET2) including at least one control means (G1, G2) for adjusting the conductivity of the at least one switch (FET1, FET2). The conductivity is arranged to be adjustable by means of an electrical control con

The invention relates to a protection circuit (30) which includes at least one switch (FET1, FET2) including at least one control means (G1, G2) for adjusting the conductivity of the at least one switch (FET1, FET2). The conductivity is arranged to be adjustable by means of an electrical control conducted to the control means (G1, G2). The protection circuit (30) includes means (22, 25, 26) for forming the electrical control, means (27, 28) for measuring at least one physical quantity affecting at least one switch (FET1, FET2), means (10) for providing information about the dependence of the conductivity properties of the at least one switch (FET1, FET2) on the at least one physical quantity, means (29) for determining the conductivity of the at least one switch (FET1, FET2) on the basis of the at least one physical quantity and the conductivity properties of the at least one switch (FET1, FET2) and means (29, 27) for determining the current (ITOT) conducted through the at least one switch (FET1, FET2) at least partly on the basis of the conductivity. Thus, the electrical control is arranged to be formed at least partly on the basis of the determined current.

대표청구항 ▼

1. A protection circuit comprising: a switch control means for adjusting the conductivity of said switch by means of an electrical control signal applied to the control means; means for forming the electrical control signal; means for measuring at least one physical quantity affecting the conducti

1. A protection circuit comprising: a switch control means for adjusting the conductivity of said switch by means of an electrical control signal applied to the control means; means for forming the electrical control signal; means for measuring at least one physical quantity affecting the conductivity of said switch; a parameter memory for storing dependence information about the relationship between the conductivity of said switch and said at least one measured physical quantity; means for calculating the conductivity of said switch on the basis of said at least one measured physical quantity and dependence information stored in said parameter memory; and means for determining current conducted through the switch at least partly on the basis of said calculated conductivity, wherein said means for forming the electrical control signal is arranged to form the electrical control signal at least partly on the basis of the determined current. 2. A protection circuit according to claim 1, wherein said at least one measured physical quantity is a temperature and said means for measuring at least one physical quantity affecting the conductivity of said switch comprises means for measuring the temperature of said switch. 3. A protection circuit according to claim 1, wherein said at least one measured physical quantity is the electrical control signal, and said means for measuring at least physical quantity affecting the conductivity of said switch comprises means for measuring the electrical control signal applied to the control means of said switch. 4. A protection circuit according to claim 1, wherein said means for measuring least one physical quantity affecting the conductivity of said switch comprises means for measuring a first physical quantity affecting the conductivity of said switch and means for measuring a second physical quantity affecting the conductivity of said switch. 5. A protection circuit according to claim 4, wherein the first physical quantity is a temperature of said switch and the second physical quantity is the electrical control signal applied to the control means of said switch. 6. A protection circuit according to claim 1, arranged to protect a battery from an exceptional state when the battery is charged or discharged. 7. A protection circuit according to claim 6, wherein the battery comprises more than one cell, and the protection circuit comprises means for measuring the voltage of each of the cells separately. 8. A protection circuit according to claim 6, wherein the battery is Lithium-based. 9. A protection circuit according to claim 6, arranged to provide information on an exceptional state to a host device the protection circuit detects the exceptional state. 10. A protection circuit according to claim 9, wherein information on an impending drop in voltage of the battery below a predetermined threshold value is to the host device before an under-voltage condition occurs in the battery. 11. The protection circuit of claim 9, further comprising means to compare a threshold value to an under-voltage threshold value to determine an impending under-voltage condition. 12. A protection circuit according to claim 6, arranged to provide information on an impending under-voltage condition host a device before the under-voltage condition occurs in the battery. 13. A protection circuit according to claim 6, further comprising means for supplying power from the battery to an electrically-powered device and means for supplying power from a charging device to the battery the protection circuit comprising two field-effect transistors whose drains are coupled in series in such a way that the first field-effect transistor is arranged to control charging of the battery and the second field-effect transistor is arranged to control the supply of power from the battery to the electrically-powered device. 14. A protection circuit according to claim 13, comprising: a temperature sensor for measuring the temperature of the first and second field-effect transistors; means for measuring a gate voltage of first field-effect transistor; means for measuring a gate voltage of the second field-effect transistor; and means for measuring a voltage U TOTbetween the source of the first field-effect transistor and the source of the second field-effect transistor. 15. A protection circuit according to claim 14, arranged to estimate the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)0represents the drain-to-source resistance of each of the first and second field-effect transistors at predetermined temperature gate voltage; K Tis a temperature dependent correction coefficient, obtained on the basis of value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first and the second field-effect transistors when the temperature changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of a measurement of gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 16. A protection circuit according to claim 14, arranged to estimate the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)0represents the drain-to-source resistance of each of the first and second field-effect transistors at predetermined temperature and gate voltage; K T1is a temperature dependent correction coefficient for the first field-effect transistor obtained on the basis of value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first field-effect transistor when the temperature of the first field-effect transistor changes at constant gate voltage; K T2is a temperature dependent correction coefficient for the second field-effect transistor obtained on the basis of value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the second field-effect transistor when the temperature of the second field-effect transistor changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of a measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(0n)of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 17. A protection circuit according to claim 14, arranged to estimate the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)01is the drain-to-source resistance of the first field-effect transistor at a predetermined temperature and gate voltage; R ds(on)02is the drain-to-source resistance of the second field-effect transistor at a predetermined temperature gate voltage; K Tis a temperature dependent correction coefficient obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistances Rds(on)1and Rds(on)2of the first and respectively the second field-effect transistor when the temperature changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at constant temperature; and U TOTis the Voltage between the sources of the first and second field-effect transistors. 18. A protection circuit according to claim 14, arranged to estimate the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)01is the drain-to-source resistance of the first field-effect transistor predetermined temperature and gate voltage; R ds(on)02is the drain-to-source resistance of the second field-effect transistor at predetermined temperature and gate voltage; K T1is a temperature dependent correction coefficient for the first field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the first field-effect transistor when the temperature of the first field-effect transistor changes at a constant gate voltage; K T2is a temperature dependent correction coefficient for the second field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the temperature of the second field-effect transistor changes at a constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuri ng the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at a constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 19. A protection circuit according to claim 14, wherein the temperature sensor comprises a first temperature sensor for measuring the temperature of the first field-effect transistor and a second temperature sensor for measuring the temperature of the second field-effect transistor. 20. A protection circuit according to claim 6, wherein the exceptional state is at least one of the following: an under-voltage condition, an over-voltage condition, an over-current condition. 21. A protection circuit according to claim 6, comprising means for measuring the voltage of the battery. 22. A protection circuit according to claim 1, comprising means for determining the charge condition of a battery. 23. A protection circuit according to claim 1, wherein the switch is a field-effect transistor, the control means is the gate of the field-effect transistor and the electrical control signal is a gate voltage used to control the drain-to-source resistance between the drain and the source of the field-effect transistor. 24. A protection circuit according to claim 23, wherein the parameter memory is arranged to store dependence information including information about the drain-to-source resistance of the field-effect transistor at a predetermined first temperature T0and a predetermined first gate voltage V0, as well as information on a change in the drain-to-source resistance when the gate voltage changes at the first temperature T0, and information on a change in the drain-to-source resistance when the temperature changes at the first gate voltage V0. 25. A protection circuit according to claim 23, wherein the parameter memory is arranged to store dependence information including information about the value of the drain-to-source resistance of the field-effect transistor for different combinations of temperature and gate voltage. 26. An integrated circuit including a protection circuit comprising a switch having a control means for adjusting the conductivity of said switch by means of an electrical control signal applied to the control means the protection circuit comprising: means for forming the electrical control signal; means for measuring at least one physical quantity affecting the conductivity of said switch; a parameter memory for storing dependence information about the relationship between the conductivity of said switch and said at least one measured physical quantity; means for calculating the conductivity of said switch on the basis of said at least one measured physical quantity and dependence information stored in said parameter memory; and means for determining a current conducted through the switch at least partly on the basis of said calculated conductivity, wherein said means for forming the electrical control signal is arranged to form the electrical control signal at least partly on the basis of the determined current. 27. An electrically-powered device including a protection circuit comprising a switch having a control means for adjusting the conductivity of said by means of an electrical control signal applied to the control mean s the protection circuit comprising: means for forming the electrical control signal; means for measuring at least one physical quantity affecting the conductivity of said switch; parameter memory for storing dependence information about the relationship between the conductivity of said switch and said at least one measured physical quantity; means for calculating the conductivity of said switch on the basis of said at least one measured physical quantity and dependence information stored said parameter memory; and means for determining a current conducted through the switch at least partly on the basis of said calculated conductivity, wherein said means for forming the electrical control signal is arranged to form the electrical control signal at least partly on the basis of the determined current. 28. An electrically-powered device according to claim 27, that is a wireless communication device. 29. An electrically-powered device according to claim 27, wherein the protection circuit is arranged to protect a battery used as a power source for the electronically-powered device. 30. An electrically-powered device according to claim 29, wherein the battery is arranged to be detachable connected to the device. 31. An electrically-powered device according to claim 29, wherein the battery is integrated in the device. 32. Electrically-powered device according to claim 29, wherein the protection circuit comprises means for determining the charge condition of the battery. 33. An electrically-powered device according to claim 32, arranged to be switched off responsive to information on the charge condition of the battery provided by the protection circuit. 34. A battery unit including a protection circuit comprising a switch having a control means adjusting the conductivity of said switch by means of an electrical control signal applied to the control means, the protection circuit comprising: means for forming the electrical control signal; means for measuring at least one physical quantity affecting the conductivity of said switch; parameter memory for storing dependence information about the relationship between the conductivity of said switch and said at least one measured physical quantity; means calculating the conductivity of said on the basis of said at least one measured physical quantity and dependence information stored in said parameter memory; and means for determining a current conducted through the switch at least partly on the basis of said calculated conductivity, wherein said means for forming the electrical control signal is arranged to for the electrical control signal at least partly on the basis of the determined current. 35. A battery unit according to claim 34, arranged to be detachably connected to an electrically-powered device. 36. A method for operating a protection circuit, the protection circuit comprising a switch having a control means for adjusting the conductivity of the switch by means of an electrical control signal to the control means, the method comprising: measuring at least one physical quantity affecting the conductivity of said switch storing dependence information about the relationship between the conductivity of said switch and said at least one measured physical quantity in a parameter memory; calculating the conductivity of said switch on the basis of said at least one measured physical quantity and the dependence information stored in said parameter memory; determining a current conducted through said switch at least partly on the basis of the calculated conductivity; and forming said electrical control signal at least partly on the basis of the determined current. 37. A method according to claim 36, wherein said at least one measured physical quantity is a temperature of the switch. 38. A method according to claim 36, wherein said at least one measured physical quantity is the electrical control signal applied to the control means of the switch. 39. A method according to cl aim 36, comprising: measuring a first physical quantity affecting the conductivity of the switch; measuring a second physical quantity affecting the conductivity of the switch; storing dependence information about the relationship between the conductivity of said switch and the first and second measured physical quantities in the parameter memory; calculating the conductivity of said switch on the basis of said first and second measured physical quantities and the dependence information stored in said parameter memory. 40. A method according to claim 39, used in a protection circuit in which the switch is a field-effect transistor, the control means is the gate of the field-effect transistor, and the electrical control signal is a gate voltage used to control the drain-to-source resistance between the drain and the source of the field-effect transistor. 41. A method according to claim 40, comprising storing dependence information including information about the drain-to-source resistance of the field-effect transistor at a predetermined first temperature T0and at a first gate voltage V0in the parameter memory, as well as information on a change in the drain-to-source resistance when the gate voltage changes at the first temperature T0and information on a change in the drain-to-source resistance when the temperature changes at the first gate voltage V0. 42. A method according to claim 40, comprising storing dependence information including information about the value of the drain-to-source resistance of the field-effect transistor for different combinations of temperature and gate voltage in said parameter memory. 43. A method according to claim 36, used to protect a battery from an exceptional state when the battery is charged or discharged. 44. A method according to claim 43, wherein the battery is a Lithium-based battery. 45. A method according to claim 43, comprising providing a host device with information on said exceptional condition. 46. A method according to claim 45, comprising providing information on an impending under-voltage condition to the host device before the under-voltage condition occurs in the battery. 47. A method according to claim 43, comprising determining the charge condition of the battery. 48. A method according to claim 43, wherein the exceptional state is at least one of the following: an under-voltage condition, an over-voltage condition, an over-current condition. 49. A method according to claim 43, used in a protection circuit comprising two field-effect transistors connected in series from their drains in such a way that the first field-effect transistor controls charging of the battery, and the second field-effect transistor controls the power supplied from the battery to an electrically-powered device. 50. A method according to claim 49, comprising: measuring the temperature of the first and second field-effect transistors by means of a temperature sensor; measuring the gate voltage of the first field-effect transistor; measuring the gate voltage of the second field-effect transistor; and measuring the voltage U ToTbetween the source of the first field-effect transistor and the source of the second field-effect transistor. 51. A method according to claim 50, comprising estimating the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)0represents the drain-to-source resistance of each of the first and second field-effect transistors at a predetermined temperature gate voltage; K Tis a temperature dependent correction coefficient obtained on the basis of a value given by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first and second field-effect transistors when the temperature changes at constant gate voltage; K U1is a gate voltage de pendent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the second field-effect transistor when the temperature of the second field-effect transistor changes at constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 52. A method according to claim 50, comprising estimating the current conducted via the first and the second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistor; R ds(on)0represents the drain-to-source resistance of each of the first and second field-effect transistors at a predetermined temperature and gate voltage; K T1is a temperature dependent correction coefficient for the first field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the first field-effect transistor when the temperature of the first field-effect transistor changes at constant gate voltage; K T2is a temperature dependent correction coefficient for the second field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the second field-effect transistor when the temperature of the second field-effect transistor changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the first field effect transistor and using dependence information stored in the parameter memory relating to the change in the drain-to-source resistance Rds(on)of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of a measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at a-constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 53. A method according to claim 50, comprising estimating the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors; R ds(on)01is the drain-to-source resistance of the first field-effect transistor at a predetermined temperature gate voltage; R ds(on)02is the rain-to-source resistance of the second field-effect transistor at a predetermined temperature and gate voltage; K Tis a temperature dependent correction coefficient obtained on the basis of a value provided by the temper ature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistances Rds(on)01and Rds(on)2of the first and respectively the second field-effect transistor when the temperature changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the field-effect transistor when the gate voltage of the first field-effect transistor changes at constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 54. A method according to claim 50, comprising estimating the current conducted via the first and second field-effect transistors according to the following formula:where: I TOTis the current conducted via the first and second field-effect transistors R ds(on)01is the drain-to-source resistance of the first field-effect transistor at a predetermined temperature and gate voltage; R ds(on)02is the drain-to-source resistance of the second field-effect transistor at a predetermined temperature and gate voltage; K T1is a temperature correction coefficient for the first field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the first field-effect transistor when the temperature of the first field-effect transistor changes at constant gate voltage; K T2is a temperature dependent correction coefficient for the second field-effect transistor obtained on the basis of a value provided by the temperature sensor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the temperature of the second field-effect transistor changes at constant gate voltage; K U1is a gate voltage dependent correction coefficient for the first field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the first field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)01of the first field-effect transistor when the gate voltage of the first field-effect transistor changes at a-constant temperature; K U2is a gate voltage dependent correction coefficient for the second field-effect transistor obtained on the basis of measurement of gate voltage provided by said means for measuring the gate voltage of the second field-effect transistor and using dependence information stored in the parameter memory relating to the change in drain-to-source resistance Rds(on)02of the second field-effect transistor when the gate voltage of the second field-effect transistor changes at constant temperature; and U TOTis the voltage between the sources of the first and second field-effect transistors. 55. A method according to claim 50, wherein the temperature sensor comprises a first temperature sensor for measuring the temperature of the first field-effect transistor and a second temperature sensor for measuring the temperature o f the second field-effect transistor.