High voltage power supply control apparatus

Claim 2

An apparatus according to claim 1, characterized in that said controlling means (40, 51-71, 81-89) includes: duty ratio control signal generating means (81-89) for comparing a predetermined reference value (59a) with a monitor value (45a) corresponding to the monitor voltage (44a) so as to generate a duty ratio control signal (51a) by which the duty ratio of said switching control signal (67a, 68a, 69a) is changed by the predetermined unit amount (±1 count or ±1 digit) when the monitor value (45a) differs from the predetermined reference value (59a), and the duty ratio of said switching control signal (67a, 68a, 69) is not changed when the monitor value (45a) matches the predetermined reference value (59a); and means (60-70) for generating said switching control signal (67a, 68a, 69a) having the duty ratio corresponding to the duty ratio control signal (51a) generated by said duty ratio control signal generating means (81-89).

Claim 3

An apparatus according to claim 2, characterized in that said duty ratio control signal generating means (81-89) includes: first means (81) for comparing the monitor value (45a) with the predetermined value (59a) so as to generated a first signal (81a, 81b, 81c = L, H, H) when the monitor value (45a=A) is smaller (A<B) than the predetermined value (59a=B); second means (81) for comparing the monitor value (45a) with the predetermined value (59a) so as to generate a second signal (81a, 81b, 81c = L, L, H) when the monitor value (45a=A) matches (A=B) the predetermined value (59a=B); third means (81) for comparing the monitor value (45a) with the predetermined value (59a) so as to generate a third signal (81a, 91b, 81c = H, H, L) when the monitor value (45a=A) is larger (A>B) than the predetermined value (59a=B); fourth means (82-89), when said first means (81) generates said first signal (81a, 81b, 81c = L, H, H), for generating the duty ratio control signal (51a) by which the duty ratio of said switching control signal (67a, 68a, 69a) is increased by the predetermined unit amount (±1 count or ±1 digit); fifth means (82-89), when said second means (81) generates said second signal (81a, 81b, 81c = L, L, H), for generating the duty ratio control signal (51a) by which the duty ratio of said switching control signal (67a, 68a, 69a) is not changed; and sixth means (82a, 81b, 81c = H, H, L), for generating the duty ratio control signal (51a) by which the duty ratio of said switching control signal (67a, 68a, 69a) is decreased by the predetermined unit amount (±1 count or ±1 digit).

Claim 4

An apparatus according to claim 3, characterized in that said controlling means (41, 51-71, 81-89) includes: means (45) for converting an analog amount of the monitor voltage (44a) into a digital value (45a); and digital control means (51-71) for changing the duty ratio of said switching control signal (67a, 68a, 69a), so that the digital value (45a) approaches to a predetermined digital reference value (59a).

Claim 5

An apparatus according to claim 4, characterized in that said digital control means (51-71) includes: means (51) for providing a duty ratio control signal (51a) in response to a difference between the digital value (45a) and the digital reference value (59a); means (57) for counting a reference clock (56a) having a predetermined cyclic period to output a count value (57a); means (60-65) for outputting a coincidence signal (63a, 64a, 65a) in response to matching between the count value (57a) and the duty ratio control signal (51a); means (55) for generating a frequency reference value (55a) having a cyclic period which is half of a cyclic period of the switching control signal (67a, 68a, 69a); means (66) for outputting a set signal (66a) in response to matching between the count value (57a) and the frequency reference value(55a); and means (70, 67-69) for generating said switching control signal (67a, 68a, 69a) in response to alternative triggering by said coincidence signal (63a, 64a, 65a) and said set signal (66a).

Claim 6

An apparatus according to claim 5, characterized in that said duty ratio control signal providing means (51) includes; means (58, 60-62) for temporarily storing the duty ratio control signal (51a) to provide a prescribed feedback value (58a).

Claim 7

An apparatus according to claim 6, characterized in that said duty ratio control signal providing means (51) includes: means (83) for adding either of said first, second, and third signals (81a, 81b, 81c) to the feedback value (58a) to output an added value (83a); and means (85-86) for comparing the added value (83a) with the frequency reference value (55a), so that the added value (83a) is outputted as said duty ratio control signal (51a) when the added value (83a) is smaller than the frequency reference value, and the frequency reference value (55a) is outputted as said duty ratio control signal (51a) when the added value (83a) is larger than the frequency reference value (55a).