I am designing a circuit to control a motorcycle horn (its operating frequency is 490 Hz, its resistance is 3 Ohm, and it consumes 1A on average as indicated by the power supply), and LED lights. The LED must be controlled by a high side switch, while the horn can be controlled by a low side switch.
The LED lights I am testing consist in multiple LEDs encased in a sealed commercially-available stoplight and plate light assembly. Additional components, which are probably present in the assembly, are not included in my schematic. The stoplight and illuminator are specified for 12 V, and at 12 VDC, consume about 100 mA. The plate LED turns on at a voltage of 2.8 V. The stoplight LEDs turn on at a voltage of 6.7 V.
The 12 V is supplied by a power supply (0 - 30 V DC, 0-5 A). I have also tested supplying 12 V with a DC/DC converter (5A, 12V, 50mVp-p ripple) connected to a 52V 40A battery.
When switching the horn on, the LED flickers on the whole time the horn is on. I think the issue is that V1 is spiking down by several volts when the horn is active. I have tried troubleshooting the issue by: i) adding a capacitor (470, 47, 0.1 uF) between GND and +12V ii) adding a snubber with R=10 Ohm and C=10 uF in parallel with the horn
But to no improvement. Can anyone suggest a design that would prevent the LED from flickering when the horn is active?