HV9910B Driver

A offline LED constant-current driver and matching LED array / fixtures, based on HV9910B.

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Notes

This is an offline / mains design. Do not work on the board while it is powered.

If you are not experienced with mains circuitry, do not build this.

R6 is the current-sense resistor. Use a dedicated sense resistor with a low temperature coefficient. By changing R6, you can set the driver’s maximum current; the resistor value is inversely proportional to the maximum current. A practical range is 500mOhm < R6 < 2Ohm. If R6 is too large, it may dissipate excessive power and run hot.

R7 sets the driver’s off-time. Increasing R7 increases the off-time (i.e., the off-time is proportional to the resistor value). A practical range is 200kOhm < R7 < 600kOhm. If R7 is too small, the switching frequency may become too high and cause severe heating; if R7 is too large, the frequency may drop into the audible range.

By tuning R6 and R7 together, you can adjust the LED’s maximum average current. In general, increasing the maximum current will increase the average current, while increasing the off-time will reduce the average current. Then use VR1 for fine adjustment to match the LED’s recommended maximum current.

With the BOM configuration, the average current is about 225 mA when VR1 is fully counter-clockwise; after turning VR1 clockwise by 10 turns, the average current is about 150 mA.