AN3407 STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 25
Technical content
Datasheet sections
- 1 L6585DE combo IC
- 2 Main characteristics and cir cuit description
- 2.1 VCC section
- 2.2 Power factor corrector section
- 2.3 Resonant power section
- 2.4 Output voltage feedback loop
- 3 Efficiency measurements
- 4 Input current harmonics measur ement
- 5 Functional check
- 5.1 PFC circuit
- 5.2 Half-bridge resonant LLC circuit
- 5.3 Converter startup
- 6 Bill of material
- 7 EMI choke
- 8 PFC coil specifications
- 9 Transformer specifications
- 10 References
- 11 Revision history
topology provide very good overall circuit efficiency. by film capacitors in the STEVAL-ILL038V1 board. Figure 1. STEVAL-ILL038V1 demonstration board
1 L6585DE combo IC
- Transition mode PFC converter with overvoltage and overcurrent protection
- Half-bridge controller with high-voltage driver (600 Vdc) and integrated bootstrap diode
- 3% precise, fully programmable oscillator
- Overcurrent protection
- Hard-switching detection
Figure 2. Application example
AN3407 Main characteristics and circuit description Doc ID 018857 Rev 1 5/25
2 Main characteristics and circuit description
The main features of the SMPS are listed here below:
- Extended input mains range: 90 ~ 265 VAC - frequency 50/60 Hz
- Output voltage: 48 V at 2.08 A
- Long-life, electrolytic capacitors are not used
- Mains harmonics: according to EN61000-3-2 Class-D
- Efficiency at full load: better than 90%
- Dimensions: 75 x 135 mm
2.1 VCC section
The L6585DE is supplied by applying voltage between the VCC pin and GND pin. An undervoltage lockout (UVLO) prevents the IC from operating with supply voltages too low to guarantee the correct behavior of the internal structures. An internal voltage clamp limits the voltage to around 17 V and a delivery up to 20 mA. For this reason it cannot be used directly as a clamp for the charge pump (current peaks usually reach several hundreds of mA), but can be easily used during startup in order to charge the VCC capacitor or during save mode in order to keep the IC alive, for example, connecting VCC to input voltage through a resistor. The L6585DE is supplied by the startup MOSFET Q4 and R40 charging the capacitor C25. A charge pump connected to the auxiliary winding of the HB inductor T2 supplies the controller via a small linear regulator represented by Q7. Once both stages have been activated, the controllers are supplied also by the auxiliary winding of the resonant transformer, assuring correct supply voltage during all load conditions. As the voltage on the VCC pin reaches the turn-on threshold, the chip is enabled, and the half-bridge and the PFC sections start at the same time.
2.2 Power factor corrector section
The PFC output voltage is controlled by means of a voltage-mode error amplifier and a precise internal voltage reference. The PFC section achieves current mode control operating in transition mode, offering a highly linear multiplier including a THD optimizer that allows for an extremely low THD, even over a large range of input voltages and loading conditions. The controller is the L6585DE (U1), working in transition mode and integrating all functions that are needed to perform the PFC. It delivers a stable 450 Vdc. It is a conventional boost converter connected to the output of the rectifier bridge. It includes the coil T1, the PFC transformer by YuJing, the diode D2 (STTH3L06U) and the PFC output capacitors C2, C3 and C4 by film type of 5 µF/800 V. The T1 provides also the information about the PFC coil core demagnetization to pin#11 (ZCD) of the L6585DE. The T1 auxiliary winding is connected to pin#11 (ZCD) of the L6585DE through the resistor R10. Its purpose is to provide the information that T1 has demagnetized which is needed by the internal logic for triggering a new switching cycle. The boost switch is represented by the power MOSFET Q2. The T1 secondary winding (pins#8-6) and related circuitry are dedicated to power the L6585DE during normal operation.
protection is not latched, once the PFCCS falls below 1.7 V, the PFC driver restarts. Figure 3. Multiplier
2.3 Resonant power section
the internal logic in order to set the frequency during the startup. window comparator that can be triggered by a voltage variation due to a rectifying effect. set at a fixed voltage or at the same voltage as pin#7 (CTR) of the L6585DE.
Figure 4. Oscillator characteristics are fed into the L6585DE pin#14 (HBCS). Figure 5. Half-bridge protection thresholds during run mode
2.4 Output voltage feedback loop
modulating the L6585DE oscillator frequency, thus keeping the output voltage regulated. R17 connects the same pin to ground and sets the minimum switching frequency.
Figure 6. Electrical schematic
3 Efficiency measurements
efficiency, measured at 230 VAC - 50 Hz. resonant stage working in ZVS provides for an overall efficiency better than 90%. Figure 8 shows the efficiency at full load over the entire AC input voltage mains range. Figure 9 shows the power factor (PF) versus load variations. Table 1. Efficiency at 115 V AC
115 VAC - 60 Hz
Table 2. Efficiency at 230 V AC
230 VAC - 50Hz
4 Input current harmonics measurement
voltage mains. Figure 10 and 11 show the measurement results. Figure 10. EN61000-3-2 Class-D standard - 185 V Figure 11. EN61000-3-2 Class-D standard - 230 V AC/50 Hz, THD=5.98%, PF=0.980 at
5 Functional check
5.1 PFC circuit
waveforms at switching frequency are measured in Figure 16 and 17. Figure 14. PFC stage waveforms at 115 V Figure 15. PFC stage waveforms at 230 V AC - Figure 16. PFC stage waveforms at 115 V AC - Figure 17. PFC stage waveforms at 230 V AC -
5.2 Half-bridge resonant LLC circuit
has been chosen around 94 kHz. transformer’s secondary windings and in this case it is not an issue. frequency, while during the following half-cycle it is working at resonance frequency. value that would be 2 (VOUT+VF), hence about 100 V. Figure 18. Primary side LLC waveforms at Figure 19. Secondary side LLC waveforms at
230 VAC - full load
ripple of the circuit at full load.
5.3 Converter startup
Figure 20. High-frequency ripple on output Figure 21. Low-frequency ripple on output Figure 22. Wake-up at 115 V AC - 60 Hz - full Figure 23. Wake-up at 230 V AC - 60 Hz - full
6 Bill of material
Table 3. STEVAL-ILL038V1 demonstration board: bill of material
Table 3. STEVAL-ILL038V1 demonstration board: bill of material (continued)
7 EMI choke
Figure 28. EMI: OTC21V-4S vertical type EMI choke Table 4. Transformer specifications
22.0 MAX
26.0 MAX
8 PFC coil specifications
Figure 29. PFC: QP2520V-vertical type for PFC choke Table 5. Transformer specifications
9 Transformer specifications
Figure 30. Transformer: LP2920H - ho rizontal type for LLC transformer Table 6. Transformer specifications
10 References
- L6585DE datasheet, STMicroelectronics 2. L6562A datasheet, STMicroelectronics 3. L6599 datasheet, STMicroelectronics 4. Application notes: AN2870, AN3106, STMicroelectronics
Table 7. Document revision history 30-Aug-2011 1 Initial release.