2000~3000W AC-DC Full-Bridge LLC Circuit Design

1Detailed Circuit Design

Key Input/Output Specifications:

Input voltage: AC100V~AC240V,

Maximum power: 2000W @AC100V input, 3000W @AC220V input
Output voltage: DC 30V~DC90V (to be specified); this example 60V, regulation accuracy 1%
Output current: 25-80A; this example 50A, CC accuracy ±5%
Full-load efficiency: 92% @AC100V; 95% @AC220V
Standby power: approx. 2W (AC100V)

Circuit Design Overview:

The main topology is a totem-pole bridgeless PFC circuit + full-bridge LLC circuit. The AC input EMI suppression consists of 2 common-mode chokes and 3 X capacitors, followed by a lightning surge absorber and an inrush limiter (NTC + relay), then the PFC boost inductor and totem-pole bridgeless PFC control circuit produce a 400V DC bus on the 450V 900µF energy-storage capacitor, feeding the full-bridge LLC that converts 400V to 60V; the LLC secondary uses synchronous rectification to raise efficiency and reduce losses. The output CV/CC circuit consists of 4 op-amps, a reference source and an optocoupler. A CR5269-based flyback chip provides auxiliary power for the whole circuit.

The PFC unit is based on the HT1010 digital chip for totem-pole bridgeless PFC control, paired with two HT3600 half-bridge driver ICs. The LLC unit extends the L6599 half-bridge LLC chip with two EG3188 half-bridge drivers to form the full-bridge LLC topology.

2Circuit Block Diagram

2000~3000W AC-DC Full-Bridge LLC Circuit Design — figure 1 — FIG.01 · CLICK TO ENLARGE

3Circuit Schematic (three partial diagrams)

2000~3000W AC-DC Full-Bridge LLC Circuit Design — figure 2 — FIG.02 · CLICK TO ENLARGE

Figure 3-1: schematic of the PFC control circuit

2000~3000W AC-DC Full-Bridge LLC Circuit Design — figure 3 — FIG.03 · CLICK TO ENLARGE

Figure 3-2: schematic of the AC input filter and PFC boost circuits

2000~3000W AC-DC Full-Bridge LLC Circuit Design — figure 4 — FIG.04 · CLICK TO ENLARGE

Figure 3-3: schematic of the full-bridge LLC converter and auxiliary power unit

4Key components BOM (example 56V 50A output; when output voltage or power differs, recalculate the parameters of components shown in red)

Component/Function	Specification	Calculation Method & Notes
Input fuse	T15A / 250V / slow-blow	≥ 1.5× the AC maximum operating current; slow-blow type
Lightning surge varistor	561KD14	Withstands 2kV 1kA repeated or 4kV 2kA single lightning strikes
NTC inrush limiter	MF72-10D15	Suppresses power-on inrush
Bypass relay	Rated DC100V / 30A	Bypasses the NTC to reduce operating losses
EMI common-mode choke 1	2mH / 25A	Adjust per EMI test results
EMI common-mode choke 2	1mH / 25A	Adjust per EMI test results
X2 differential-mode capacitor 1	1µF / 275V	EMI suppression
X2 differential-mode capacitor 2	2.2µF / 275V	Adjust per EMI test results
Surge-protected rectifier bridge	800V / 10A	Surge-protection bypass for the totem-pole bridgeless PFC
Input E-CAP	6 × 150µF / 400V	≥ 0.3µF/W (see SMPS Energy-Storage Capacitor Calculation)
PFC inductor	165µH / 35A	See PFC Boost Inductor Design & Current Calculation
PFC high-speed switch	G1N65R035TB-N (650V / 35mΩ)	Low conduction loss, high-speed switching
PFC low-speed switch	LSB65R041GF (650V / 36mΩ, tr=26ns, tf=6.8ns)	Works with the high-speed switch for high efficiency
PFC control IC	HT1010	PFC control
PFC driver IC	HT3600	PFC drive
PFC current transformer	30A, 1:100 (SMD)	Current sensing
Half-bridge driver IC	EG3118	LLC drive
LLC control IC	L6599A	LLC control
LLC full-bridge switch	IPW60R045P7 (650V / 45mΩ, Coss=190pF, tr=15ns, tf=4ns)	Main power switch
LLC transformer	PQ5040	See LLC Circuit Calculation
LLC resonant inductor	PQ3225, 25µH / 15A	See LLC Circuit Calculation
LLC current transformer	30A, 1:100	Current sensing
LLC resonant capacitor	4 × 333 / 630V	See LLC Circuit Calculation
Synchronous rectifier IC	MP6924A	Synchronous rectification control
Synchronous rectifier MOS	IRFP4568PBF (150V / 4.8mΩ, 58V / 50A output)	Vds ≥ 2×Vout; Rds ≤ 0.1/Iout; parallel operation supported; Coss=977pF
Output E-CAP	63V / 250µF	C ≥ 14×Pout/(f×Vout²); see energy-storage capacitor calculation
Output relay	DC100V / 80A	Controls the output
Output current sampling	1.25mΩ	Rds ≤ 0.05/Iout; for wide-range high accuracy use a Hall sensor
Output common-mode filter	10µH / 50A	Adjust per EMI test results

5Key Power-Device Loss & Thermal Evaluation

The main heat-generating components are the input filter, the magnetic components of the PFC and LLC converters, power switches and power rectifiers. Below is the heat estimation method based on this example (input AC100V, output 56V 35A); for other output voltages and powers, adjust the parameters and recalculate:

1. Input filter: P_ac_emi = I_in_rms* I_in_rms*R_ac_emi = 21*21*0.1=4.4W 2. Input rectifier bridge: P_ac_rect = I_in_rms*1.0*2 = 2.3*1.0*2 = 4.6W 3. PFC inductor: see the PFC Circuit Calculation document, P_pfc_induct = 20.2W 4. PFC fast GaN FET: P_pfc_gan = P_turn_on + P_turn_off + P_coss + P_on=25.2W （P_turn_on =0.5*Vds*Ipeak*tr*fs=0.5*400*24.5*0.005*0.050=1.2W P_turn_off = 0.5*Vds*Ipeak*tf*fs=0.5*400*24.5*0.01*0.050=2.4W P_on = I_gan_rms*I_mos_rms*Rds_on=24.5*24.5*0.035=21.0W P_coss = 0.5*Coss*Vds*Vds*fs = 0.5*147*400*400*50*10^-9=0.6W） 5. PFC slow MOSFET: the switching frequency is 50Hz, so switching loss is negligible; P_pfc_mos = P_on =21.6W P_on = I_mos_rms*I_mos_rms*Rds_on=24.5*24.5*0.036=21.6W 6. LLC transformer: see the LLC Circuit Calculation document, P_trans = 51.7W 7. LLC switch MOSFET: P_mos = 4*(P_turn_on+P_turn_off +P_on)= 16W

The four bridge arms of the LLC converter have essentially identical losses; per arm:

P_turn_on = 0 (ZVS) P_turn_off = 0.2*Vds*Imag*tf*fs=0.2*400*7.4*0.004*0.087=0.2W P_on = I_mos_rms*I_mos_rms*Rds_on=9.2*9.2*0.045=3.8W 8. Resonant inductor loss: see Appendix 2 LLC Circuit Calculation, P_trans = 2.7W 9. Secondary rectifier: P_rec_mos = 2*(P_on + P_turn_on+ P_turn_off + P_diode) = 24W （P_turn_on = 0 P_turn_off = 0.3*Vout*Id*tf*fs=0.3*56*75*0.084*0.087=9.2W P_on = I_mos_rms*I_mos_rms*Rds_on=30*30*0.00025=2.25W P_diode = Vsd*Io*t_death*fs=0.9*50*0.1*0.087=0.4W） 10. Secondary current sense resistor: P_cs3 = I_out*I_out*Rcs=50*50*0.00125=3.1W

Total loss of items 1~10 above is 176W, so the overall efficiency is: 2000/(2000+176)=91.9%