A Hybrid Current Mode Controller with Fast Response Characteristics for Super Capacitor Applications

Abstract

A wide-bandwidth current-controller is required for the fast charging and discharging of applications containing super capacitors. To accomplish this, peak current mode is generally used due to the speed of its response characteristics. On the other hand, peak current mode control must be provided with a slope compensation function to restrain sub-harmonic oscillations. However, if the controlled output voltage is varied, the slope must be changed accordingly. Nonetheless, it is not easy to change the slope for every change in output voltage. Another solution involves the slope being set at the maximum value, which results in a slow response. Therefore, in this paper, a hybrid mode controller was proposed that uses a peak current and a newly-specified valley current. Using the proposed hybrid mode control, sub-harmonic oscillation did not occur for duty cycles larger than 0.5 and response times were fast.

Hybrid Current-Mode Control of PSFB Converter to Compensate Slew Interval and Prevent Magnetic Saturation of Transformers

“…In particular, the impact is significant when the charging target is a supercapacitor in which dynamic response is important. HCMC has been proposed to reduce the response delay associated with the application of slope compensation to boost converters [23]. HCMC combines PCMC and valley current-mode control.…”

“…Figure 9 shows a control block diagram of the HCMC technique proposed in Reference [23]. In this study, HCMC was applied to a non-isolated boost converter in which the peak and valley currents are easily detected.…”

“…From Equations ( 16), ( 17), ( 21) and ( 23), I p1 + I p2 can be obtained as Equation (23). ∆D can be obtained as Equation (24) using Equations ( 20) and (23).…”

“…This prevents the overcompensation-related response delay that typically occurs due to the operating slope compensation in the peak current mode. HCMC has been applied to boost converters, where the peak and valley currents are easily detected [23]. However, when HCMC is applied to PSFB converters, it is difficult to detect the valley current from a DC-link-side current sensor normally used in PCMC.…”