An implicit first-order non-dimensional model of open loop dc-dc boost converter operating in discontinuous conduction mode with constant power (CPL) load is derived. Analysis of this model shows that successive period doubling bifurcations and subharmonic oscillation take place when certain parameters such as the switching period, the operating duty cycle and the load power are varied. The resulting typical period-doubling route to chaos is confirmed by numerical simulations under the mentioned operating conditions.