Voltage mode and peak current mode
Voltage-mode and current-mode control have both pros and cons that I've tried to list below:
Voltage-mode control (VM):

easy to implement: the duty ratio is directly controlled by comparing an artificial ramp of comfortable amplitude (1-2 V for instance) with an error voltage representative of the correction to apply. A latch ensures a robust operation for double-pulse suppression.

naturally-low open-loop output impedance: take a buck converter, its output impedance in dc is the inductor ohmic loss \$r_L\$ in parallel with the load resistance. An open-loop buck converter operated from a constant input voltage can deliver a stable voltage almost independent from the load current as long as continuous conduction (CCM) mode is ensured.

the control-to-output transfer function of a voltage-mode-controlled converter operated in CCM (for the three basic switching cells, buck, buck-boost and boost) is that of a second-order type with a right-half-plane zero (RHPZ) for the last two cells. The resonant frequency for the boost and buck-boost converters moves with the duty ratio and complicates compensation.

when operated in discontinuous conduction mode (DCM), the cell remains a second-order system but heavily damped: a pole dominates in low frequency while the second is positioned at higher frequencies.

considering points 3 and 4, a well-compensated VM system must seamlessly transition between the two modes as load current varies. It can complicate a bit the compensation strategy.

a voltage-mode converter operated in its simplest form is blind to the inductor current. Modern converters now include a cycle-by-cycle current limit for a safe operation.

the above point is bad for robustness but is good for very narrow continuous (read non-skip) duty ratio operation but also for values well beyond 50% (for a buck for instance) without the need to resort to some sort of compensation.

a voltage-mode converter offers a poor input-voltage rejection. The input-to-output transfer function of a buck involves \$V_{in}\$ and it requires a high open-loop gain to reject the input variations.

finally, an opel-loop VM converter offers a positive incremental input resistance.


Current-mode control (CM):

the duty ratio generation now requires to observe the inductor current and you need a sensor for this. Usually, a resistance does the job or a current-sense transformer for high-power operations.

high open-loop output impedance. As the peak inductor current transforms the inductor in a constant current generator (as a first-order approximation), the dc output resistance is that of the load. Unlike the VM case, you cannot fix the peak current of a CCM-operated open-loop buck powered from a constant input and vary the load current. The output voltage will change significantly. You need a control loop to ensure proper operations.

the control-to-output transfer function of a current-mode-controlled converter operated in CCM (for the three basic switching cells, buck, buck-boost and boost) is that of a third-order type with the right-half-plane zero (RHPZ) as in VM. A pole dominates at low frequency and two poles are located at \$\frac{F_{sw}}{2}\$.The resonant frequency for the boost and buck-boost converters no longer moves with the duty ratio and eases compensation.

a current-mode converter is susceptible to sub-harmonic oscillations when operated in CCM and having a duty ratio approaching or exceeding 50%. These oscillations find their origin in the inner current-loop whose crossover is too high. Reducing crossover by the means of an external ramp is a way to cure these sub-harmonic oscillations. It complicates the analysis but nothing insurmountable.

when operated in discontinuous conduction mode (DCM), the cell changes to a damped second-order system where a pole dominates in low frequency.

considering points 3 and 5, a well-compensated CM system naturally seamlessly transitions between the two modes as load current varies. Compensation is easy.

It is difficult to generate very narrow pulses with a current-mode controller. What is called a leading-edge blanking (LEB) circuit is used to cleanse the inductor current which, practically speaking, blinds the control for several hundreds of nano-seconds. Added to the propagation delay, it limits the minimum pulse duration.

current-mode control naturally offers an excellent input voltage rejection (if the prop. delay is short) as the target is the inductor peak current: the switch remains on until the current setpoint is met whether this happens at lo- or hi-line. With a properly-compensated buck converter, you can even theoretically null the input voltage ac contribution.

finally, an open-loop CM converter offers a negative incremental input resistance.


Based on these remarks, CM seems certainly simpler to use compared to VM and most of today PWM controllers operate in current mode. Still, many dc-dc modules for the telecom industry are implementing voltage-mode control for the naturally-low output impedance and the absence of compensation ramp. This is all I can think of for tonight!