how to fix varying pwm along with constant frequency of 20kHz in cyclon 2 ep2c5t144c8

I don't want to put you off your code but I can't follow it since I have my own simple code below for pwd at any duty cycle, any frequency:

    library ieee;
    use ieee.std_logic_1164.all;
    use IEEE.numeric_std.all;
    entity pwm is
    port(
        clk           : in  std_logic;
        freq_word     : in  std_logic_vector(13 downto 0) := "00011001100110";
        duty_scaled   : in  std_logic_vector(13 downto 0) := "10000000000000";
        pwm           : out std_logic
        );
    end entity;
    architecture rtl of pwm is
      
      signal ptr : unsigned(14 downto 0) := (others => '0');
       
      begin
      process(clk)
      begin
        if(rising_edge(clk)) then
           ptr <= ptr + unsigned(freq_word);
           pwm <= '0';
           if ptr(13 downto 0) < unsigned(duty_scaled) then
               pwm <= '1';
           end if;
        end if;
      end process;
         
    end rtl;