Provided is an LED driving circuit suitable for use as a school teaching material capable of arbitrarily adjusting light of an LED light source, having excellent power efficiency with little power loss and heat generation, and capable of protecting an LED from overcurrent. . A total of a voltage of a light emitting source 6 including an LED or a plurality of LEDs and an input DC power supply 1 when a current having a predetermined limit current value in the normal forward voltage-forward current characteristics of the LED flows. DC voltage conversion circuit 4 that converts the voltage to a predetermined DC voltage value that is equal to or less than the forward voltage value, and converts the DC voltage output of the DC voltage conversion circuit into a PWM voltage pulse whose ON / OFF time ratio can be arbitrarily varied in a predetermined cycle. And a pulse voltage generation circuit 5 for applying this pulse voltage to the light source, and a current for detecting the current of the light source and limiting the current value when the current value reaches a predetermined limit current value of the LED. The limiting circuit 8 is provided. [Selection] Figure 1【課題】ＬＥＤ光源の調光が任意に可能で、しかも電力損失、発熱が極めて少ない電力効率に優れ、またＬＥＤを過電流から保護できる学校教材用に使用して好適なＬＥＤ駆動回路を提供する。【解決手段】単数または複数のＬＥＤを含む発光源６、入力直流電源１の電圧を上記ＬＥＤの通常の順方向電圧―順方向電流特性上の所定の制限電流値の電流が流れた時の合計順方向電圧値以下の所定の直流電圧値となるように電圧変換する直流電圧変換回路４、この直流電圧変換回路の直流電圧出力を所定周期でオンオフ時間比が任意に可変できるＰＷＭ電圧パルスに変換し、このパルス電圧を上記発光源に印加するパルス電圧発生回路５、及び上記発光源の電流を検出しこの電流値が上記ＬＥＤの所定の制限電流値に達するとその制限電流値に制限する電流制限回路８を備えて成ることを特徴とする。【選択図】図１
