Constant current power supply apparatus

摘要

A constant current power supply apparatus is provided which can drive a load with a constant current, even if the circuit configuration is such that a time delay is generated in the feedback control of a converter, or the like. An FB period restricting circuit including an ON generation circuit, OR circuit, inverter, and PMOS restricts the period during which an FB signal is fed back, to the logical sum of the ON period of an SW signal for driving an LED array on and a replenishment period generated by the OR circuit based on the SW signal. An FB signal generation circuit including a differential amplifier, NMOS, reference voltage, capacitor, and shunt regulator generates, in the replenishment period other than the ON period of the SW signal, an FB signal corresponding to an output current having flown through the LED array during the ON period of the SW signal.

主权项

1. A constant current power supply apparatus, supplying electric power from a primary side to a secondary side, and using the electric power supplied to the secondary side for driving a load on/off with a SW pulse signal as an external pulse signal supplied to the secondary side under PWM control, the constant current power supply apparatus comprising:
a feedback signal generator circuit for generating a feedback signal corresponding to an output current flowing through the load; a feedback circuit for feeding back the feedback signal generated in the feedback signal generator circuit from the secondary side to the primary side; a control circuit for controlling the supply of electric power from the primary side to the secondary side by generating a pulse signal having a pulse width in response to the feedback signal fed back by the feedback circuit; and a feedback period restricting circuit for adjusting the period during which the feedback signal is fed back, wherein the feedback period restricting circuit has an OR circuit which adjusts the period during which the feedback signal is fed back to the logical sum of the ON period of the SW pulse signal as an external pulse signal during which the load is driven on, and a replenishment period during which the SW pulse signal is terminated, such that the power supply current is constant during a delay period in feeding back the feedback signal.