Disclosed is a switching-type constant current power supply, which comprises an alteration circuit 9 provided on the output side of a power conversion circuit 3 together with a voltage detection circuit 7, and a feedback circuit 8 provided between the voltage detection circuit 7, a current detection
Disclosed is a switching-type constant current power supply, which comprises an alteration circuit 9 provided on the output side of a power conversion circuit 3 together with a voltage detection circuit 7, and a feedback circuit 8 provided between the voltage detection circuit 7, a current detection circuit 5 and a control circuit 4. The alteration circuit 9 is operable, during a current flow period where a load current IL is flowing, to set the signal level of a second feedback signal F 2 at a value less than a reference voltage Vref to be supplied to a common error amplifier EA1 in a control circuit 4, and operable, during a current cut-off period where the load current IL is not flowing, to set the signal level of the second feedback signal F 2 at a value greater than the reference voltage Vref. During the current cut-off period, the feedback circuit 8 is operable to supply the second feedback signal F2 to the control circuit 4 so as to substantially discontinue the operation of the power conversion circuit 3. The switching-type constant current power supply of the present invention can stabilize the load current even under the condition that a load (e.g. display including LEDs) is repeatedly turned on and off.
대표청구항▼
What is claimed is: 1. A switching-type constant current power supply device including a switching-type power conversion circuit for supplying a given current to a load connected to the output side thereof, a current detection circuit connected to said load and adapted to generate a first feedback
What is claimed is: 1. A switching-type constant current power supply device including a switching-type power conversion circuit for supplying a given current to a load connected to the output side thereof, a current detection circuit connected to said load and adapted to generate a first feedback signal proportional to a load current, and a control circuit connected to said power conversion circuit and said current detection circuit and adapted, in response to receiving said first feedback signal, to stabilize said load current, said switching-type constant current power supply device comprising: a voltage detection circuit connected to the output side of said power conversion circuit, and adapted to generate a second feedback signal proportional to an output voltage of said power conversion circuit; a feedback circuit connected to said current detection circuit, said voltage detection circuit and said control circuit, and adapted to supply either one of said first and second feedback signals to said control circuit; and an alteration circuit connected to a given position of a circuit block comprising said voltage detection circuit, said control circuit and said feedback circuit which are connected with each other, and adapted, in response to a change in said load, to alter a relative magnitude relationship between a reference voltage and said second feedback signal which are to be entered into a common error amplifier in said control circuit. 2. The switching-type constant current power supply device as defined in claim 1, wherein said alteration circuit is connected to said voltage detection circuit, and adapted, in response to the change in said load, to alter the signal level of said second feedback signal which is to be entered into one of input terminals of said error amplifier in said control circuit. 3. The switching-type constant current power supply device as defined in claim 2, wherein said load current is turned on and off at an arbitrary or given timing according to the operation of said load, wherein: said feedback circuit is operable to supply said first feedback signal to said control circuit when said load current is flowing, and to supply said second feedback signal to said control circuit when said load current is not flowing: and said alteration circuit is operable to alter said second feedback signal to a relatively large value in response to cutting off the flow of said load current, and to alter said second feedback signal to a relatively small value in response to initiating the flow of said load current. 4. The switching-type constant current power supply device as defined in claim 3, wherein said second feedback signal is altered to a value greater than that of said reference voltage immediately after the flow of said load current is cut off, and to a value less than that of said reference voltage immediately after the flow of said load current is initiated. 5. The switching-type constant current power supply device as defined in claim 4, wherein when said second feedback signal is being supplied at a value greater than that of said reference voltage, said control circuit is operable to substantially discontinue the operation of said power conversion circuit. 6. The switching-type constant current power supply device as defined in claim 2, wherein said alteration circuit comprises a parallel circuit which is composed of a resistor and a switch and connected between one terminal of said voltage detection circuit and the ground, said switch being adapted to be switched in accordance with said first feedback signal. 7. The switching-type constant current power supply device as defined in claim 2, wherein said alteration circuit comprises a level shift circuit connected to said voltage detection circuit, and a switch which is connected in parallel to said level shift circuit and adapted to be switched in accordance with said first feedback signal. 8. The switching-type constant current power supply device as defined in claim 1, wherein said load is repeatedly turned on and off at a high speed. 9. The switching-type constant current power supply device as defined in claim 1, wherein said alteration circuit is connected to said control circuit, and adapted, in response to the change in said load, to alter the level of said reference voltage which is to be entered into one of input terminals of said error amplifier in said control circuit. 10. The switching-type constant current power supply device as defined in claim 9, wherein said load current is turned on and off at an arbitrary or given timing according to the operation of said load, wherein: said feedback circuit is operable to supply said first feedback signal to said control circuit when said load current is flowing, and to supply said second feedback signal to said control circuit when said load current is not flowing: and said alteration circuit is operable to alter said reference voltage to a relatively small value in response to cutting off the flow of said load current, and to alter said reference voltage to a relatively large value in response to initiating the flow of said load current. 11. The switching-type constant current power supply device as defined in claim 10, wherein said reference voltage is altered to a value less than that of said second feedback signal immediately after the flow of said load current is cut off, and to a value greater than that of said second feedback signal immediately after the flow of said load current is initiated. 12. The switching-type constant current power supply device as defined in claim 11, wherein when said reference voltage is being supplied at a value less than that of said second feedback signal, said control circuit is operable to substantially discontinue the operation of said power conversion circuit. 13. The switching-type constant current power supply device as defined in claim 9, wherein said alteration circuit comprises a plurality of resistors connected in series between a reference voltage source for generating said reference voltage and the ground, and a switch which is connected in parallel to one of said plurality of resistors and adapted to be switched in accordance with said first feedback signal. 14. The switching-type constant current power supply device as defined in claim 9, wherein said alteration circuit comprises a series circuit which is composed of a resistor and a level shift circuit and connected between a reference voltage source for generating said reference voltage and the ground, and a switch which is connected in parallel to said level shift circuit and adapted to be switched in accordance with said first feedback signal. 15. The switching-type constant current power supply device as defined in claim 1, wherein said power conversion circuit includes first and second rectifying/smoothing circuits capable of providing respective outputs approximately in conjunction with one another, said first rectifying/smoothing circuit being operable to supply a given current to said load, wherein: said voltage detection circuit is connected to said second rectifying/smoothing circuit; and said alteration circuit is connected to said voltage detection circuit, and adapted, in response to the change in said load, to alter the signal level of said second feedback signal which is to be entered into one of input terminals of said error amplifier in said control circuit. 16. The switching-type constant current power supply device as defined in claim 15, wherein said load current is turned on and off at an arbitrary or given timing according to the operation of said load, wherein: said feedback circuit is operable to supply said first feedback signal to said control circuit when said load current is flowing, and to supply said second feedback signal to said control circuit when said load current is not flowing: and said alteration circuit is operable to alter said second feedback signal to a relatively large value in response to cutting off the flow of said load current, and to alter said second feedback signal to a relatively small value in response to initiating the flow of said load current. 17. The switching-type constant current power supply device as defined in claim 16, wherein said second feedback signal is altered to a value greater than that of said reference voltage immediately after the flow of said load current is cut off, and to a value less than that of said reference voltage immediately after the flow of said load current is initiated. 18. The switching-type constant current power supply device as defined in claim 17, wherein when said second feedback signal is being supplied at a value greater than that of said reference voltage, said control circuit is operable to substantially discontinue the operation of said power conversion circuit. 19. The switching-type constant current power supply device as defined in claim 15, wherein said alteration circuit comprises a parallel circuit which is composed of a resistor and a switch and connected between one terminal of said voltage detection circuit and the ground, said switch being adapted to be switched in accordance with said first feedback signal. 20. The switching-type constant current power supply device as defined in claims 15, wherein said alteration circuit comprises a level shift circuit connected to said voltage detection circuit, and a switch which is connected in parallel to said level shift circuit and adapted to be switched in accordance with said first feedback signal. 21. A switching-type constant current power supply device including a switching-type power conversion circuit for supplying a given current to a load connected to the output side thereof, a current detection circuit connected to said load and adapted to generate a first feedback signal proportional to a load current, and a control circuit connected to said power conversion circuit and said current detection circuit and adapted, in response to receiving said first feedback signal, to stabilize said load current, said switching-type constant current power supply device comprising: a voltage detection circuit connected to the output side of said power conversion circuit, and adapted to generate a second feedback signal proportional to an output voltage of said power conversion circuit; a feedback circuit connected to said current detection circuit, said voltage detection circuit and said control circuit, and adapted to supply either one of said first and second feedback signals to said control circuit; and an alteration circuit connected to said voltage detection circuit, and adapted to alter the signal level of said second feedback signal output from said voltage detection circuit, in accordance with to the state of said load. 22. A switching-type constant current power supply device including a switching-type power conversion circuit for supplying a given current to a load connected to the output side thereof, a current detection circuit connected to said load and adapted to generate a first feedback signal proportional to a load current, and a control circuit connected to said power conversion circuit and said current detection circuit and adapted, in response to receiving said first feedback signal, to stabilize said load current, said switching-type constant current power supply device comprising: a voltage detection circuit connected to the output side of said power conversion circuit, and adapted to generate a second feedback signal proportional to an output voltage of said power conversion circuit; a feedback circuit connected to said current detection circuit, said voltage detection circuit and said control circuit, and adapted to supply either one of said first and second feedback signals to said control circuit; and an alteration circuit adapted, in response to the change in said load, to alter the magnitude of a reference voltage which is to be entered concurrently with said second feedback signal into a common error amplifier in said control circuit, so as to change a relative magnitude relationship between said reference voltage and said second feedback signal. 23. A switching-type constant current power supply device including a switching-type power conversion circuit for supplying a given current to a load connected to the output side thereof, a current detection circuit connected to said load and adapted to generate a first feedback signal proportional to a load current, and a control circuit connected to said power conversion circuit and said current detection circuit and adapted, in response to receiving said first feedback signal, to stabilize said load current, said switching-type constant current power supply device comprising: said power conversion circuit including first and second rectifying/smoothing circuits capable of providing respective outputs approximately in conjunction with one another, said first rectifying/smoothing circuit being operable to supply a given current to said load; a voltage detection circuit connected to the output side of said second rectifying/smoothing circuit, and adapted to generate a second feedback signal proportional to an output voltage of said power conversion circuit; a feedback circuit connected to said current detection circuit, said voltage detection circuit and said control circuit, and adapted to supply either one of said first and second feedback signals to said control circuit; and said alteration circuit connected to said voltage detection circuit, and adapted to alter the signal level of said second feedback signal output from said voltage detection circuit, in accordance with to the state of said load.
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이 특허에 인용된 특허 (5)
Stratakos Anthony J. ; Lidsky David B. ; Clark William A., Discrete-time sampling of data for use in switching regulators.
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