Switching constant-current power supply system

• US 20040183380A1
• Filed: 03/03/2004
• Published: 09/23/2004
• Est. Priority Date: 03/07/2003
• Status: Active Grant

• Current Assignee: TOKO Incorporated (Murata Manufacturing Co Limited)
• Original Assignee: TOKO Incorporated (Murata Manufacturing Co Limited)
• Inventors: Otake, Tetsushi
• Granted Patent: US 7,235,899 B2
• Time in Patent Office: Days
• US Class Current: 307/82
• CPC Class Codes: H02J 1/04 Constant-current supply systems
• CPC Class Codes: H02M 1/0019 the disturbance parameters being load current fluctuations
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 3/3374 with preregulator, e.g. current injected push-pull
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]

Abstract

Disclosed is a switching constant-current power supply system, comprising a feedback circuit 7 provided between a detector circuit 5 for generating a first feedback signal in proportion to a current flowing in a load 6, and a control circuit 4 for driving a first power converter circuit 3 which is provided on the input side of a second power converter circuit 10 to stabilize the load current. The feedback circuit 7 includes a signal hold section 8 for generating a second feedback signal. The feedback circuit 7 is operable to supply the first feedback signal to the control circuit 4 in a current supply period, and to supply the second feedback signal to the control circuit 4 in a current cutoff period. The second feedback signal has a signal value approximately equal to that of the first feedback signal appearing in the current supply period. The switching constant-current power supply system can stabilize the load current even under the condition that the load is repeatedly turned on/off.

Claims

1. A switching constant-current power supply system including:

a switching-type first power converter circuit operable, in response to supply of power from an external power source, to generate a stable DC voltage;

a second power converter circuit capable of functioning as a DC-AC converter and operable, in response to supply of said DC voltage, to supply an AC or pulsed current to a load;

a current detector circuit for generating a feedback signal in proportion to a load current; and

a control circuit for controlling the operation of said first power converter circuit according to said feedback signal, said switching constant-current power supply system comprising;

a feedback circuit provided between said current detector circuit and said control circuit, said feedback circuit including a signal hold section for holding a signal, said feedback circuit being operable to supply either one of a first feedback signal generated from said current detector circuit and a second feedback signal generated from said signal hold section, wherein said second feedback signal has a signal value approximately equal to that of said first feedback signal at a certain time point.

2. The switching constant-current power supply system as defined in claim 1, wherein said signal hold section provided in said feedback circuit is operable to refer to the first feedback signal at a certain time point when the load current flows, and then generate the second feedback signal approximately equal to said first feedback signal,

wherein said feedback circuit is operable to supply the first feedback signal to said control circuit when the load current flows, and to supply said second feedback signal to said control circuit when no load current flows.

3. The switching constant-current power supply system as defined in claim 2, wherein said signal hold section includes a peak hold circuit, wherein said second feedback signal is approximately equal to a maximum value of said first feedback signal generated when the load current flows.

4. The switching constant-current power supply system as defined in claim 3, wherein said signal hold section further includes a reset circuit operable, in response to the change from the state where no load current flows to the state where the load current flows, to supply a signal for allowing said peak hold circuit to be returned to its initial state.

5. The switching constant-current power supply system as defined in claim 2, wherein said load includes a light-emitting diode to be turned on and off at a high speed, wherein said switching constant-current power supply system is operable, to supply a given current to said light-emitting diode when said light-emitting diode is in its ON state.

6. The switching constant-current power supply system as defined in claim 3, wherein said load includes a light-emitting diode to be turned on and off at a high speed, wherein said switching constant-current power supply system is operable, to supply a given current to said light-emitting diode when said light-emitting diode is in its ON state.

7. The switching constant-current power supply system as defined in claim 4, wherein said load includes a light-emitting diode to be turned on and off at a high speed, wherein said switching constant-current power supply system is operable, to supply a given current to said light-emitting diode when said light-emitting diode is in its ON state.