Chris Nelson wrote “This means that the power going into the regulator is 9V*500mA = 4.5W and the power out of the regulator is approximately 3.3V*500mA=1.65W.

Figure 1 LM317 and HC4053 combine to make a PWM power DAC while Q1 forces preregulator U3 to track and maintain a constant 3v U2 I/O headroom differential to improve efficiency.. As described in the ...