Looking for a Constant Voltage/ Constant Current power supply schematic
Produce a constant current circuit.
Feed its output into a constant voltage circuit. 
Can be done with 2 x LM317 or equivalent. 

As long as the voltage taken by the load of the CV circuit is less than the CC setting the system will provide CV. When the load tries to draw more than the CC setting the system automatically transitions into CC mode.

To run purely as CV set CC control to max.
 To run purely as CC set CV control to max.



Added:

@Felice - A single high power driver is about "how" not "what".
ie work out what you want to achieve and THEN see what circuit elements are required to do it. Olin has effectively answered your question in general terms. 

Here is a simple way of doing it with linear components and a single "pass element".   

Supply power via an N-Channel MoSFET - Vin to Drain, Vout from source.
Place a current sense resistor in series either twixt drain and supply or source and load.
Voltage sense Vout at the most negative point of this combination.
Convert sensed current and voltage to ground referenced voltages.
Compare these sense voltages to adjustable references and allow output voltage to rise (eg pullup on FET gate) until either of the sensed parameters is at its limit.
Limit voltage maximum using whatever senor comparator has reached its limit at any given moment.
If CV limit is reached first then the supply is a CV supply.
IOf CC limit is reached 1st supply is a CC supply.
If you turn up a reference that is the limiting one to the extent that the other non-varying sensor reaches its limit then the supply transitions smoothly CC-CV or CV-CC.

You can use the variable comparators to operate a SMPS instead  of a linear supply with the same result.  The SMPS can "think" that it is a Voltage controlled voltage source and it is of no "importance to it" that it is being voltage limited so that a CC condition is met.