Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
241 words
A circuit for supplying a constant dc current to a load comprising: a dc voltage source (20), an inverter (30) providing an ac voltage from said dc voltage source, said inverter including switching menas (31) driven to turn on and off for repetetively interrupting said dc voltage in order to provide said ac voltage, an ac-to-dc converter (50) connected to rectify and smooth said ac voltage for providing a resulting dc current to be supplied to said load (10), current sensing means (90) for sensing said dc current being supplied to said load (10); comparator means (100) for comparing a level of said sensed dc current with a predetermined reference level to provide a first output when the level of said sensed dc current is below said reference level and to provide a second output when the level of said sensed output dc current exceeds said reference level; and control means (110, 150, 60) responding to said first and second outputs to provide a first feedback control signal and a second feedback control signal, respectively, said first feedback control signal being a train of pulses having increasing duty ratio so as to correspondingly increase on-off time ratio of said switching means (31) for gradually increasing the dc current, and said second feedback control signal being a train of pulses of decreasing duty ratio so as to correspondingly decrease on-off time ratio of said switching means for gradually decreasing said dc current.
Claim 2
Dependent Claim
241 words
A circuit for supplying a constant dc current to a load comprising: a dc voltage source (20), an inverter (30) providing an ac voltage from said dc voltage source, said inverter including switching menas (31) driven to turn on and off for repetetively interrupting said dc voltage in order to provide said ac voltage, an ac-to-dc converter (50) connected to rectify and smooth said ac voltage for providing a resulting dc current to be supplied to said load (10), current sensing means (90) for sensing said dc current being supplied to said load (10); comparator means (100) for comparing a level of said sensed dc current with a predetermined reference level to provide a first output when the level of said sensed dc current is below said reference level and to provide a second output when the level of said sensed output dc current exceeds said reference level; and control means (110, 150, 60) responding to said first and second outputs to provide a first feedback control signal and a second feedback control signal, respectively, said first feedback control signal being a train of pulses having increasing duty ratio so as to correspondingly increase on-off time ratio of said switching means (31) for gradually increasing the dc current, and said second feedback control signal being a train of pulses of decreasing duty ratio so as to correspondingly decrease on-off time ratio of said switching means for gradually decreasing said dc current.
Claim 3
Dependent Claim
147 words
The circuit of claim 1, wherein said control means including a feedback controller (110), an integrator circuit (150), and a PWM controller (60), said feedback controller (110) providing said train of first feedback control pulses of increasing duty ratio in response to said first output from said comparator means (100) and providing said train of said second feedback control pulses of decreasing duty ratio in response to said second output from said comparator means (100); said integrator circuit (150) operating to integrate said first and second feedback control pulses into a corresponding first analog signal of increasing level and a corresponding second analog signal of decreasing level, respectively, and said PWM controller (60) connected to receive said first and second analog signals and to drive said switching means (31) at varying duty ratio which is a functionon of the level of said first and second analog signals.
Claim 4
Dependent Claim
77 words
The circuit of claim 2, wherein said first and second feedback control pulses are each defined to comprise repeating units of pulses occurring for a predetermined period of time, the width of said pulses being equal within each unit but increasing and decreasing in a stepwise manner as said units repeat in order to vary the duty ratio of said first and second feedback control pulses in the direction of increasing and decreasing said output dc current.
Claim 5
Dependent Claim
95 words
The circuit of claim 3, wherein said feedback controller (110) has a first period of time and a second period of time which is shorter than said first period of time, said feedback controller operating to provide said first feedback control pulses in which said units of pulses repeat for said first period of time until said dc current reaches said reference level, and to provide said first and second feedback control pulses in which said units of pulses repeat for said shortened second period of time once said dc current exceeds said reference level.