POWER SUPPLY UNIT

• US 20020006045A1
• Filed: 10/08/1999
• Published: 01/17/2002
• Est. Priority Date: 07/27/1999
• Status: Active Grant

• Current Assignee: Nippon Signal Company Limited
• Original Assignee: Nippon Signal Company Limited
• Inventors: YUASA, TAKAYUKI, SHIRAI, TOSHIHITO, SAKAI, MASAYOSHI, FUTSUHARA, KOICHI
• Granted Patent: US 6,434,025 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H02H 7/1213 for DC-DC converters
• CPC Class Codes: H02H 7/1255 responsive to internal faults, e.g. by monitoring ripple in output voltage
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac

Abstract

The invention relates to a power supply unit which can fail-safely monitor not only for an excessive power supply output but also for an abnormal drop in output level. At the time of start-up, with the start signal from a start circuit, an AC signal is supplied to a primary side of a transformer and based on an AC output from a secondary side of the transformer, an output for supplying to an external load is generated and this output is monitored with a monitoring circuit. If the output level is within a set upper and lower limit threshold value range the output is judged to be normal and a high level normal verification signal is generated from the monitoring circuit, and with the high level normal verification signal, an AC signal is supplied to the primary side of the transformer, and the output supply to the external load is continued.

Claims

1. A power supply unit which switches a DC signal to produce an AC signal, and supplies to the outside an AC or DC power supply output based on the produced AC signal, comprising a monitoring circuit for monitoring as to whether or not said power supply output is within a previously set upper and lower limit threshold value range, and generating a normal verification signal of a high energy level indicating a normal condition when within said threshold value range, wherein the power supply output can be supplied to the outside when the normal verification signal is generated from said monitoring circuit.

2. A power supply unit according to claim 1, wherein after an abnormality is detected and said normal verification signal is temporarily stopped, a normal verification signal is not generated from said monitoring circuit even if said abnormality is cancelled.

3. A power supply unit according to claim 1, wherein there is provided a start circuit for generating a start signal for power supply output start-up.

4. A power supply unit according to claim 3, wherein said start circuit generates a start signal for a predetermined time from a power supply start-up time.

5. A power supply unit according to claim 3, wherein said start circuit generates a start signal for a predetermined time on input of a generation command signal from the outside after power supply start-up.

6. A power supply unit according to claim 3, wherein when a normal verification signal is generated from said monitoring circuit, supply of said start signal is stopped.

7. A power supply unit according to claim 1, wherein there is provided a limited output generating circuit for generating at the time of power supply start-up, an output which is limited to a level within said upper and lower limit threshold value range, and the generated limited output is input to said monitoring circuit, and said normal verification signal is generated from said monitoring circuit.

8. A power supply unit according to claim 1, wherein switch means is provided in an output supply path for supplying said power supply output to the outside, and said switch means is switched on by a normal verification signal from said monitoring circuit, to conduct an output supply path.

9. A power supply unit according to claim 8, wherein said switch means is constructed with a first switch and second switch connected in series, and the first switch is switched on after the second switch is switched on and is switched off prior to the second switch.

10. A power supply unit according to claim 9, wherein said monitoring circuit is able to generate a normal verification signal under the condition that said first switch is off and said second switch is off.

11. A power supply unit according to claim 1, provided with a first switching element for passing/interrupting said DC signal for input to a primary side of a transformer, and a switching control circuit for generating a control signal for ON/OFF switching of said first switching element, which generates a DC power supply output based on an AC output generated in a secondary side of said transformer with ON/OFF operation of said first switching element and supplies this to the outside, and at the same time inputs said power supply output to said switching control circuit and compares this with a target level set within said upper and lower limit threshold value range, and controls said control signal so that the power supply output level approaches said target level, to stabilize the power supply output,

wherein there is provided a start circuit for generating a start signal for starting power supply output, and when at least one of said start signal and said normal verification signal is being generated, the control signal of said switching control circuit is supplied to the first switching element.

12. A power supply unit according to claim 11, wherein there is provided logical sum means for generating a logical sum output for said normal verification signal and said start signal, and an output from said logical sum means is made a drive power supply for said switching control circuit.

13. A power supply unit according to claim 11, wherein signal transmission means is disposed in a control signal supply path for supplying a control signal of said switching control circuit to said first switching element, for closing said control signal supply path when at least one signal of said start signal and said normal verification signal is generated, and transmitting the control signal to said first switching element.

14. A power supply unit according to claim 11, wherein there is provided a limited output generating circuit for generating, when a start signal is generated from said start circuit, an output which is limited to a level within said upper and lower limit threshold value range, and the generated limited output is input to said monitoring circuit, and said normal verification signal is generated from said monitoring circuit.

15. A power supply unit according to claim 14, wherein said limited output is input to said monitoring circuit via said transformer.

16. A power supply unit according to claim 15, a series circuit of a second switching element and an output limiting impedance element is connected in parallel with said first switching element which is series connected to the primary winding of said transformer and there is provided a first and a second signal supply paths for respectively supplying the control signal of said switching control circuit to the first and second switching elements, and when the start signal is generated the second signal supply path is conducted to supply a control signal to the second switching element and a limited output is produced in the secondary side of said transformer, and when based on this limited output, the normal verification signal is generated from said monitoring circuit, the first signal supply path is conducted to supply a control signal to the first switching element.

17. A power supply unit according to claim 11, wherein switch means is disposed in an output supply path for supplying said power supply output to the outside, and when a normal verification signal is generated from said monitoring circuit the output supply path is conducted by said switch means.

18. A power supply unit according to claim 17, wherein said switch means is constructed with a plurality of switches connected in series.

19. A power supply unit according to claim 18, wherein of said plurality of switches, one switch comes on before the other switch and goes off after the other switch.

20. A power supply unit according to claim 17, wherein there is provided a switch off verification circuit for detecting an OFF condition of said switch means and outputting an OFF verification signal, and said monitoring circuit is able to generate a normal verification signal on the condition that said OFF verification signal is being generated.

21. A power supply unit according to claim 11, wherein said monitoring circuit incorporates;

level verification means for verifying that a voltage level of the power supply output is within said upper and lower limit threshold value range, ripple verification means for verifying that a ripple level of the power supply output is equal to or less than a predetermined level, logical product means into which is input the outputs from the two verification means, and off-delay means for generating an output after a predetermined off-delay time lapse from input of the output from said logical product means, and the output from said off-delay means is made said normal verification signal.

22. A power supply unit according to claim 19, wherein said monitoring circuit incorporates;

level verification means for verifying that the voltage level of the power supply output is within the upper and lower limit threshold value range, ripple verification means for verifying that a ripple level of the power supply output is equal to or less than a predetermined level, logical product means into which is input the outputs from the two verification means, off-delay means for generating an output after a predetermined off-delay time lapse from input of the output from said logical product means, and on-delay means which takes the output from said off-delay means and generates an output and stops the output after a predetermined on-delay time lapse from said output generation, and said one switch is driven based on the output from said off-delay means, and the output from said on-delay means is made said normal verification signal.

23. A power supply unit according to claim 20, wherein said monitoring circuit incorporates;

level verification means for verifying that the voltage level of the power supply output is within the upper and lower limit threshold value range, ripple verification means for verifying that a ripple level of the power supply output is less than a predetermined level, logical product means into which is input the outputs from the two verification means, off-delay means for generating an output after a predetermined off-delay time lapse from input of the output from said logical product means, self hold means with an output from said off-delay means input to a hold input terminal, and the off verification signal of said switch off verification circuit input to a trigger input terminal, which self holds a trigger output by its own output, and on-delay means which takes the output from said off-delay means and generates an output and stops the output after a predetermined on-delay time lapse from said output generation, and said switch means is driven based on the output from said self hold means, and the output from said on-delay means is made said normal verification signal.

24. A power supply unit according to claim 23, wherein a contact point which is operable from the outside is disposed in an off verification signal supply path for connecting to the trigger input terminal of said self hold means.

25. A power supply unit according to claim 11, wherein said start circuit generates a start signal for a predetermined time from the time of power supply start-up.

26. A power supply unit according to claim 11, wherein when said normal verification signal is generated the supply of said start signal is stopped.

27. A power supply unit according to claim 1, provided with a first switching element for passing/interrupting said DC signal for input to a primary side of a transformer, and a switching control circuit for generating a control signal for ON/OFF switching of said first switching element, which generates a DC power supply output based on an AC output generated in a secondary side of said transformer with ON/OFF operation of said first switching element and supplies this to the outside, and at the same time inputs said power supply output to said switching control circuit and compares this with a target level set within said upper and lower limit threshold value range, and controls said control signal so that the power supply output level approaches said target level, to stabilize the power supply output,

wherein there is provided switch means in an output supply path for supplying said power supply output to the outside, and said switch means is driven by the normal verification signal of said monitoring circuit to thereby conduct the output supply path.

28. A power supply unit according to claim 27, wherein said switch means is constructed with a first switch and second switch connected in series, and the construction is such that said first switch is switched on after the second switch is switched on and switched off prior to the second switch.

29. A power supply unit according to claim 28, wherein said monitoring circuit is able to generate a normal verification signal under the condition that said first switch is off and said second switch is off.

30. A power supply unit according to claim 29, wherein said monitoring circuit incorporates;

level verification means for verifying that a voltage level of the power supply output is within an upper and lower limit threshold value range, ripple verification means for verifying that a ripple level of the power supply output is equal to or less than a predetermined level, logical product means into which is input the outputs from the two verification means, first off-delay means for generating an output after a predetermined off-delay time lapse from input of the output from said logical product means, self hold means with an output from said first off-delay means input to a hold input terminal, and an off verification signal of an off verification circuit for verifying the OFF condition of said first switch input to a trigger input terminal as a result of an off verification of said second switch, which self holds the trigger input by its own output, second off-delay means for generating an output after a predetermined off-delay time lapse from input of the output from said self hold means, and on-delay means which takes the output from said self hold means and generates an output and stops the output after a predetermined on-delay time lapse from said output generation, and said monitoring circuit drives said second switch based on the output from said second off-delay means, and drives said first switch based on the output from said on-delay means.

31. A power supply unit according to claim 1, wherein with an AC power supply unit incorporating an oscillator for generating an oscillating signal with input of said DC signal, and an output circuit having a switch circuit which is switchingly operated with the oscillation signal from said oscillator to generate an AC power supply output, supply of AC power supply output to the outside is made possible when a normal verification signal is being generated from said monitoring circuit.

32. A power supply unit according to claim 31, wherein the construction is such that when said normal verification signal is being generated, an oscillating signal from said oscillator is transmitted to said switch circuit.

33. A power supply unit according to claim 32, wherein a band-pass filter with a previously set predetermined frequency for the oscillator signal as a central frequency, is disposed in a signal supply path for supplying the oscillating signal from said oscillator to the switch circuit.

34. A power supply unit according to claim 31, wherein the switching operation of said switching circuit is made possible when said normal verification signal is being generated.

35. A power supply unit according to claim 31, wherein switch means is disposed in an output supply path for supplying said power supply output to the outside, and said switch means is driven by the generation of a normal verification signal from said monitoring circuit to conduct the output supply path and supply the power supply output to the outside.

36. A power supply unit according to claim 35, wherein said switch means has two switches connected in series.

37. A power supply unit according to claim 36, wherein of said two switches, one switch comes on before the other and goes off after the other.

38. A power supply unit according to claim 35, wherein there is provided a switch off verification circuit for detecting an OFF condition of said switch means and outputting an off verification signal, and said monitoring circuit is able to generate a normal verification signal on the condition that said off verification signal is being generated.

39. A power supply unit according to claim 31, wherein said monitoring circuit incorporates;

level verification means for verifying that a voltage level of the power supply output is within said upper and lower limit threshold value range, frequency verification means for verifying that the power supply output frequency is within a predetermined frequency range based on the pulse width of the power supply output, and a logical product means into which is input the output of the two verification means, and the output from said logical product means is made said normal verification signal.

40. A power supply unit according to claim 39, wherein the construction is such that said frequency verification means detects the pulse width of the power supply output to verify the power supply output frequency.

41. A power supply unit according to claim 39, wherein said frequency verification means filters the power supply output with a band-pass filter and detects if the output level of the band-pass filter is equal to or above a predetermined value to verify the power supply output frequency.

42. A power supply unit according to claim 38, wherein said monitoring circuit incorporates;

level verification means for verifying that a voltage level of the power supply output is within said upper and lower limit threshold value range, frequency verification means for verifying that the power supply output frequency is within a predetermined frequency range based on the pulse width of the power supply output, a logical product means into which is input the output of the two verification means, and self hold means with an output from said logical product means input to a hold input terminal, and the off verification signal from said switch off verification circuit input to a trigger input terminal, which self holds the trigger input by its own output, and said switch means is driven based on the output from said self hold means.

43. A power supply unit according to claim 42, wherein a contact point which is operable from the outside is disposed in an off verification signal supply path for connecting to the trigger input terminal of said self hold means.

44. A power supply unit according to claim 36, wherein said monitoring circuit generates a normal verification signal on the condition that one switch is off, and there is provided a switch drive means for intermittently switching the other switch off based on said normal verification signal, and a switch performance verification means for detecting ON/OFF switching of said other switch and generating a hold signal so that the normal verification signal continues and inputting this to said monitoring circuit, and said one switch is driven ON by the normal verification signal of said monitoring circuit.

45. A power supply unit according to claim 31, wherein there is provided a start circuit for generating a start signal for starting power supply output, and when at least one of said start signal and the normal verification signal of said monitoring circuit is being generated, power supply output is supplied from said output circuit.

46. A power supply unit according to claim 31, wherein there is provided a start circuit for generating a start signal for starting power supply output, and a limited output generating circuit for generating a limited output of a level within said upper and lower limit threshold value range, and when a start signal is generated, the limited output of said limited output generating circuit is supplied from said output circuit.