# Active Clamp Boost Converter with Blanking Time Tuning Considered
## 1 Introduction  
How to obtain a high-power density power supply is becoming more and more attractive in the world. By increasing the switching frequency, the size of magnetic devices and capacitors can be reduced so that high-power density requirements can be achieved. However, for the hard switching to be considered, the higher the switching frequency, the greater the switching loss and the more difficult the heat process. In addition, the switching loss under hard switching is proportional to the switching frequency. Consequently, the problem in high switching frequency is becoming more and more serious, thereby causing resonant and soft-switching converters to develop to reduce the switching loss. The conventional resonant converter is based on the inductor connected in series with the main switch or the capacitor connected in parallel with the main switch so as to form a resonant loop. As the voltage on or current in the switch is dropped to zero, the switch is switched to achieve zero voltage switching (ZVS) turn-on of the switch or zero current switching (ZCS) turn-off of the switch. Basically, this method can reduce the crossover area of voltage and current of the switch, thereby decreasing the switching loss. However, large voltage and current spikes increase the voltage and current stresses of switches as well as increase the conduction losses. Furthermore, in order to render the output voltagecontrolled at a desired value, the switching frequency is varied because the resonant time is fixed, causing the design of the filter to be difficult. As the conventional resonant converter has the demerits mentioned above, the soft-switching converter is presented. The ZVS/ZCS pulse-width-modulation (PWM) converter [1; 2; 3] has put an auxiliary switch to the resonant loop of the resonant converter to make the resonant time point adjustable, thereby leading to fixed frequency control and making the design of the filter easy. However, the conduction loss is large because the resonant voltage on and current in the circuit elements are large. The operating principle of the ZVT/ZCT converter is that prior to turn-on of the main switch, the auxiliary switch is conducted, and hence the transient resonance occurs. As the voltage on or current in the main switch resonates to zero, the main switch is turned on to achieve ZVT turn-on or ZCT turn-off. As the auxiliary switch in the off-state, no resonance happens, leading to effectively reducing the voltage or current stress as well as conduction loss. In the literature [4; 5], although the main switches have ZVS turn-on, the auxiliary switches still operate under hard switching. In the literature [6; 7; 8], although the main and auxiliary switches have ZVS turn-on, many components lead to an increase in cost. The operating behavior of the ZVZCT converter [9; 10; 11] is that the auxiliary switch has two transient resonances over one cycle so that the main switch has ZVT turn-on and ZCT turn-off. Indeed, this converter can reduce switching and conduction losses, and no additional voltage and current stresses on components. However, such a converter has complexity in control and a relatively large part count, leading to an increase in cost. Furthermore, as the ZVS or ZVT turn-on is relatively suitable for the metal-oxide-semiconductor field-effect transistor (MOSFET) switch [10], there are many studies on the MOSFET switch with ZVS or ZVT turn-on. In addition, based on the above-mentioned, the ZVS pulse width modulation (PWM) converter, the ZVT converter, and the ZVZCT converter have individual disadvantages. Accordingly, the active clamp technique is developed, which is composed of an auxiliary switch in series with a capacitor. The work of [12] applies the synchronous rectifier to the ZVS active clamp forward converter to reduce the conduction loss. Another paper [13] applies the soft-switched synchronous rectifier to the ZVS active clamp forward converter to reduce the conduction loss as well as the switching loss.