1. A constant voltage dimming power supply for lighting device, being configured to adjust the output voltage after being regulated by a dimmer to realize constant voltage PWM output, includes:a rectifying circuit, configured to rectify and filter an output voltage regulated by dimmer;
a constant voltage circuit, configured to be electrically connected to an output end of the rectifying circuit;
characterized in that:
a constant current load circuit, electrically connected to an output end of the rectifying circuit;
a frequency conversion and protection sampling circuit, configured to be electrically connected to the output end of the constant current load circuit and the output end of the constant voltage circuit;
and a switching circuit for controlling illumination of lighting load;
wherein the frequency conversion and protection sampling circuit includes a frequency conversion circuit that receives pulse signals output from the constant current load circuit, converts the output signal of the constant current load circuit into a duty cycle signal suitable for controlling the switching circuit, provides frequency conversion to output the same duty cycle signal, and detects the output abnormality of the constant voltage circuit in real time, so as to control the on-off of the switching circuit; and
a short circuit protection sampling circuit being configured to collect signals output from the constant voltage circuit and transmit them to the frequency conversion circuit.