Inductor selection:
In order to maintain strict hysteresis current control when designing the LED constant current source, the inductance must be large enough to ensure that energy can be supplied to the load during HO and ON, and the load current is not significantly reduced, resulting in the average current falling below the expected value.
First, let's look at the effect of the inductor. Suppose there is no output capacitor (COUT), so the load current and the inductor current are exactly the same, which can more clearly explain the effect of the inductor. The figure below shows the effect of the inductance value on the frequency over the range of the input voltage. It can be seen that the input voltage has a great influence on the frequency, and the inductance value has a great influence on the frequency reduction when the input low voltage. (Note: It is not necessarily the same as the reference picture, but it is only a description of the problem)
The figure above shows the frequency response at different inductance values. The figure below shows that the change in load current is significantly increased over the range of input voltage variation as the inductance decreases.
The figure below shows the variation of the frequency according to different output voltages and different inductance values.
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