Energy conversion device comprising: - a
rectifier circuit (2) having a plurality of diodes (201-204) with a
full bridge configuration and rectifying the input from an
AC power supply (1); - a
choke coil (3) connected to a DC terminal of the
rectifier circuit (2); - an
inverter circuit (4), wherein a first
branch (A) having a first switching element (401) and a second switching element (402) connected in series with each other with a connection point (4a) therebetween as a first AC end (4a), a second
branch (B) having a third switching element (403) and a fourth switching element (404) connected in series with each other with an intermediate connection point (4b) as a second AC end (4b), and a
DC capacitor (5) connected in parallel between DC buses (P, N), wherein the first AC end (4a) is connected to a positive DC terminal (2a) of the
rectifier circuit (2), wherein a negative (N) of the DC buses (P, N) is connected to a negative DC terminal (2b) of the rectifier circuit (2); - an
isolation transformer (6) having a primary winding (6a) and a secondary winding (6b), wherein the first AC end (4a) and the second AC end (4b) of the
inverter circuit (4) are connected to the respective ends of the primary winding (6a); and - a
control circuit (11) for performing an output control of the
inverter circuit (4), - wherein the
control circuit (11) performs high
power factor control for the circuit current (iac) flowing from the
AC power supply (1) via the rectifier circuit (2) by means of PWM control for the first
branch (A) using the duty cycles of the first and second switching elements (401, 402), and controls the
voltage of the
DC capacitor (5) by means of PWM control for the second branch (B) using the duty cycles of the third and fourth switching elements (403, 404), limited by an upper limit (Dlim) which is the smaller of the duty cycles for the first and second switching elements (401, 402) in the first branch (A), so as to control the
power output to the
secondary side of the
isolation transformer (6).