Texas Instruments 600W Isolated PFC AVR Power Supply Evaluation Module UCC25600EVM-644 UCC25600EVM-644 Datenbogen
Produktcode
UCC25600EVM-644
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0
0.5
1
1.5
2
2.5
3
fn
10 W
100 W
600 W
1000 W
Gain
Design Considerations
5.2
LLC Resonant DC/DC Converter
The design of the resonant converter also general follows the standard procedure shown in the
documentation provided together with the UCC25600 but with some alterations based on the demand of
the audio application.
documentation provided together with the UCC25600 but with some alterations based on the demand of
the audio application.
5.2.1
LLC Gain
The input voltage to the LLC converter is when the boost converter is running approximately 390 VDC.
This voltage has a significant ripple at full power. The gain of the LLC converter depends on the ratio of
transformer magnetizing inductance and resonant induct size together with load and switching frequency.
transformer magnetizing inductance and resonant induct size together with load and switching frequency.
For this design, the following parameters were calculated:
L
M
: 170µH, L
R
: 30µH, n: 4.6, C
R
: 47nF
This gives a resonant frequency of 134kHz.
shows the gain curves normalized to the resonant
frequency as a function of the output power:
Figure 3. LLC Gain
During high power mode where the rail voltage is 50V, the minimum frequency is clamped to
approximately 90kHz. This limit is set by the parallel connection of R36 and R96 (Q12 is ON in this mode).
This should ensure enough gain to regulate the output voltage and keep the gain characteristics
monotone increasing with lower frequencies until the 90 kHz is reached.
approximately 90kHz. This limit is set by the parallel connection of R36 and R96 (Q12 is ON in this mode).
This should ensure enough gain to regulate the output voltage and keep the gain characteristics
monotone increasing with lower frequencies until the 90 kHz is reached.
During low power mode where the rail voltage is 25V and the PFC converter disabled, the DC/DC
converter needs additional gain at low line to regulate to 25V. During this mode, the transistor Q12 is OFF
and the lower frequency limit is given by R36 and is 62kHz.
converter needs additional gain at low line to regulate to 25V. During this mode, the transistor Q12 is OFF
and the lower frequency limit is given by R36 and is 62kHz.
11
SLOU293C – June 2010 – Revised September 2012
A 600-W, Isolated PFC Power Supply for AVR Amplifiers Based on the
TAS5630 and TAS5631
Copyright © 2010–2012, Texas Instruments Incorporated