Active‐clamping forward converter with non‐linear step‐down conversion

Abstract

This study proposes a forward converter with non-linear step-down conversion ratio. In comparison with traditional forward converters, it has a higher duty utilisation ratio. Furthermore, the two output inductors can equally divide the load current, and therefore the current stress of inductors and output diodes can be reduced. Thus, the proposed converter is suitable for high step-down applications. On the primary side, active-clamp control can nullify the voltage spike of main switch while also achieving zero voltage switching operation of the main switch and auxiliary switch, hence the switching loss can be reduced. Detailed analysis and design of the proposed converter are described. Experimental results are recorded for a prototype converter with an AC input voltage ranging from 90 to 264 V, an output voltage of 12 V, and an output power of 240 W.

A new magnetron driving method using a phase‐shifted active clamp forward converter for sulfur plasma tube applications

“…The voltage of the clamp capacitor is also expressed by Equation (19). Besides, the voltage of the secondary winding of the power transformer is calculated by Equation (20). In Equation ( 20), V oT is the voltage of the secondary coil of the power transformer.…”

“…In the early part of the circuit, the voltage and current stress of the main transistors are expressed as Equations ( 17) and ( 18) [20]. In Equation ( 17), D 1 is the duty cycle of the main transistors.…”

Zero‐current transition single‐ended forward converter

“…(iv) The tertiary winding is still existing [12][13][14] and (v) the LLS requires numerous extra components (eight components) due to which the optimal design is complicated and losses are increased [15]. In [16][17][18], an active clamp circuit (ACC) consisting of an auxiliary switch and a capacitor in parallel with the primary of the transformer is proposed. The ACC achieves ZVS for main and auxiliary switches and reduces to the high-voltage spike of the main switch.…”

“…However, (i) the tertiary reset winding, (ii) high‐voltage spikes across power switch and rectifier diode due to resonant between parasitic capacitors and transformer leakage inductance, (iii) hard switching, which cause losses and electromagnetic interference (EMI), and (iv) reversing the recovery problems of output diodes is the main drawback of this converter. To solve these problems, some techniques are proposed in [1–23].…”

Step‐down converter with wide voltage conversion ratio

“…Moreover, if the capacitors in the input divider are not perfectly matched, the voltages across these two capacitors will not be equal, and this makes voltage sharing control required. In [18], two switched inductors are used on the secondary side of the forward converter to achieve a high step-down voltage gain, and since this converter belongs to an isolated converter, it is relatively suitable for high input voltage applications.…”