AN3329 STMICROELECTRONICS | Alldatasheet

Document overview

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  • PDF pages: 47

Technical content

Datasheet sections

  • 1 Main characteristics and cir cuit description
  • 2 Efficiency measurement
  • 3 Harmonic content measurement
  • 4 Functional check
  • 5 Conducted emission pre-compli ance test
  • 6 Bill of materials
  • 7 PFC coil specifications
  • 8 Resonant power transformer speci fications
  • 9 Auxiliary flyback transformer specifications
  • 10 Revision history

170 W power supply with PFC and standby supply for flat TV

applications. The electrical specifications are tailored to a typical flat TV. very low input consumption during standby operation. Figure 1. EVL170W-FTV: 170 W demonstration board

Main characteristics and circuit description AN3329 6/47 Doc ID 18376 Rev 1

1 Main characteristics and circuit description

The main features of the SMPS are:

  • Universal input mains range: 90 ÷ 264 Vac - frequency 45 ÷ 65 Hz
  • Output voltage 1: 24 V ± 5 % at 6 A for backlight and audio supply
  • Output voltage 2: 12 V ± 3 % at 2 A for TV panel supply
  • Output voltage 3: 5 V ± 2 % at 2 A for microprocessor supply
  • Mains harmonics: acc. to EN61000-3-2 Class-D or JEITA-MITI Class-D
  • Standby mains consumption: at 230 Vac <150 mW with 50 mW load
  • Overall efficiency at full load: above 90 %
  • EMI: according to EN55022-Class-B
  • Safety: according to EN60065
  • Dimensions: 197x115 mm, 25 mm maximum component height from PCB
  • PCB: single side, 70 µm, CEM-1, mixed PTH/SMT. The circuit is made up of two sections; a 10 W supply generating 5 V standby output, dedicated to supplying the TV microprocessor and the logic circuitry, and a larger section made up of a PFC front-end and an LLC resonant converter which provides two output voltages, one dedicated to supplying the TV panel, and one for the backlight and audio power amplifiers. The PFC stage delivers 400 V constant voltage and acts as a pre- regulator for both the LLC stage and the standby supply. An external signal, referred to as secondary ground, turns the PFC and LLC stages on and off. Startup At turn-on the standby supply starts up and delivers 5 V dedicated to the TV microprocessor and other logic circuitry. It also generates the auxiliary supply voltage for the PFC and LLC controllers at primary side via the linear regulator Q7. Q7 is activated by the optocoupler U5, that is driven by the logic signal on/off (active high). At startup, the on/off signal (delivered by the microprocessor) is supposed to be low, so the PFC and the LLC are off. Once the on/off signal is asserted high, the regulator Q7 provides 14 V to the L6564 PFC controller and the L6599A LLC controller; to always ensure proper operation of the LLC, the circuit is designed so that the PFC starts first, then the downstream converter. The LINE pin of L6599A allows the resonant stage to operate only if the PFC output is delivering its rated output voltage. It prevents the resonant converter from working with an input voltage that is too low which may cause the undesirable capacitive-mode operation. The L6599A LINE pin internal comparator has a hysteresis allowing to set the turn-on and turn-off thresholds independently. The LLC turn-on voltage (PFC output) and the turn-off threshold are set to 380 V and 300 V respectively. This last value prevents the LLC stage operating in capacitive-mode but allows the resonant stage to operate even in the case of mains sag or dips lowering the PFC output voltage. Brownout protection Brownout protection prevents the circuit from working with abnormal mains levels. It is accomplished by both the Viper, through the brownout pin, and the L6564, through an internal comparator internally connected to the VFF pin (#5), which detects the mains voltage peak value. The internal comparators allow the IC operation with proper mains level only, as defined by power supply specifications, therefore, if the input voltage is below around 80 Vac (typ.), the circuit is not allowed to start up.

AN3329 Main characteristics and circuit description Doc ID 18376 Rev 1 7/47 Resonant power stage The downstream converter features the ST L6599A, which embeds all the functions needed to drive properly the resonant converter with 50 % fixed duty cycle and variable frequency. The converter makes use of a transformer designed with the integrated magnetic approach, using the primary leakage as the resonant series inductance and the magnetizing inductance as the resonant shunt inductance. The transformer secondary-side is center- tapped and power Schottky diodes are used as output rectifiers. Additional LC filter stages have been added on each output to minimize high-frequency ripple. Output voltage feedback loop The regulation feedback loop is implemented through a typical circuit using a TL431, which modulates the current through the optocoupler diode. In order to improve the cross regulation, the two resonant stage output voltages are regulated by a weighted feedback control, that is using a single rail to regulate multiple outputs. The feedback loop is closed to the primary side by R37, which connects the RFMIN (#4) pin of the resonant controller L6599A to the optocoupler phototransistor and sets the maximum switching frequency at around 130 kHz. This value has been chosen to limit the switching losses at light load operation. On the same pin, R36 connected to ground, sets the minimum switching frequency. The RC series R22 and C21 sets both soft-start maximum frequency as well as duration. L6599A overload and short-circuit protection Half bridge primary-side current is sensed by the lossless circuit consisting of R53, C36, D14, D12, R55, and C38 and is fed into the ISEN pin (#6). During an overcurrent event, the pin voltage rises to the internal comparator threshold (0.8 V), triggering the following protection sequence: the soft-start capacitor (C10) connected to the DELAY pin (#2) is charged by an internal 150 µA current generator and is slowly discharged by the resistor R12. This pin is connected to the DIS (#8) pin and, if the voltage reaches 1.85 V, the IC stops switching, being latched off. Once latched, an on/off signal recycle is needed to restart the converter. Overvoltage and open loop protection Both PFC and resonant stages are provided with their own overvoltage protections. The PFC controller L6564 monitors its output voltage through the resistor divider connected to the PFC_OK pin (#6) protecting the circuit in case of loop failure, disconnection, or deviation from the nominal value of the feedback loop divider. When a fault condition is detected, the L6564 is shut down and latched off by an internal circuit monitoring the voltage on the PFC_OK and INV pins, until the mains voltage is recycled. Upon the occurrence of an overvoltage condition, of either the 24 V or 12 V output of the resonant stage, the Zener diodes D16 and D17 conduct, respectively, forcing Q10 to be turned on by the resulting base current, which causes Q9 to conduct. These two transistors form a pnp-npn SCR (silicon controlled rectifier) structure that shorts to ground the anode of the U5 optocoupler in such a way that the IC supply voltage Vcc cannot be delivered to controllers by Q7, forcing them to be latched off until the mains voltage is recycled.

Figure 2. Electrical diagram

2 Efficiency measurement

also reported in the graph of Figure 3. Table 1. Overall efficiency measured at different AC input voltages

3 Harmonic content measurement

Figure 7. EN61000-3-2 compliance at 230 Vac Figure 8. JEITA-MITI compliance at

100 Vac - 50 Hz, full load

Figure 9. EN61000-3-2 compliance at

230 Vac - 50 Hz, 75 W

Figure 10. JEITA-MITI compliance at

100 Vac - 50 Hz, 75 W

4 Functional check

maximum input voltage and full load operation. drain voltage can be noted on the sidebar on the right. Figure 13. Standby supply waveforms at

115 Vac - 60 Hz, full load

Figure 14. Standby supply waveforms at

230 Vac - 50 Hz, full load

brownout circuit prevents the Viper27LN from starting up during abnormal mains conditions. Figure 15. Standby supply waveforms at

400 Vdc, full load

Figure 16. Standby supply output rectifiers Figure 17. Standby supply 5 V ripple at Figure 18. Standby supply startup at 115 Vac -

60 Hz, full load

with low standby consumption requirements. Figure 19. Standby supply burst mode Figure 20. Standby supply burst mode Figure 21. Standby supply OVP at 115 Vac - Figure 22. Standby supply OVP at 230 Vac -

Figure 23. Standby supply OVP at 115 Vac -

60 Hz - PFC on - 1 A

Figure 24. Standby supply OVP at 115 Vac - Figure 25. Standby supply output short-circuit Figure 26. Standby supply output short-circuit

soft-start cycle. Hiccup cycles are repeated as long as the short-circuit condition lasts. transitions are clean and there is no output voltage or Vcc dip. Figure 27. Standby supply dynamic load at

115 Vac - 60 Hz - PFC off

Figure 28. Standby supply dynamic load at

115 Vac - 60 Hz - PFC on

high power factor are achieved as the peak inductor current waveform follows the MULT pin. THD (total harmonic distortion) is considerably reduced by the L6564 THD optimizer. (zero voltage switching) condition is achieved, decreasing MOSFET commutation losses. transition losses, as seen in Figure 32. pin is tuned to make the turn-on of the MOSFET occur just on the valley of the drain voltage. Figure 29. PFC Vds and inductor current at Figure 30. PFC Vds and inductor current at

115 Vac - 60 Hz, full load - detail

L6564 signals are shown in Figure 33 and 34 for reference. (#3) pin at the peak of the line voltage matching that on the VFF pin. Figure 31. PFC Vds and inductor current at Figure 32. PFC Vds and inductor current at

230 Vac - 50 Hz, full load - detail

Figure 33. L6564 signals-1 at 115 Vac - 60 Hz, Figure 34. L6564 signals-2 at 115 Vac - 60 Hz,

also added to waveforms in order to get the maximum resolution. be noted that the 12 V output has a very tight variation - within +/- 3 %. 300 Hz load step frequency on one output, with the other delivering the rated load. 24 V output has a maximum deviation of ± 4 %, mainly due to the series filter inductor L4. therefore very tight and suitable to power properly the internal logic of the LCD panel. load on 12 V (cross-regulation) is ± 0.5 %. Figure 42. 12 V - 2 A; 24 V 0 ÷ 6 A transition at

115 Vac - 60 Hz

Figure 43. 24 V - 6 A; 12 V 0 ÷ 2 A transition at

Figure 46. 12 V short-circuit at full load and Figure 47. 12 V short-circuit at full load and

115 Vac - 60 Hz - detail

Figure 48. 24 V short-circuit at full load and Figure 49. 24 V short-circuit at full load and

therefore demonstrating a good immunity of the circuit against mains dips. Figure 56. Half cycle mains dip at full load and Figure 57. Full cycle mains dip at full load and

5 Conducted emission pre-compliance test

all test conditions the measurements are far below the limits. Figure 58. CE peak measurement at 115 V - 60 Hz and full load - phase wire Figure 59. CE peak measurement at 115 V - 60 Hz and full load - neutral wire

6 Bill of materials

Table 2. Bill of materials

Table 2. Bill of materials (continued)

AN3329 PFC coil specifications Doc ID 18376 Rev 1 39/47

7 PFC coil specifications

General description and characteristics

  • Application type: consumer, home appliance
  • Transformer type: open
  • Coil former: vertical type, 6+6 pins
  • Max. temp. rise: 45 ºC
  • Max. operating ambient temperature: 60 ºC
  • Mains insulation: n.a.
  • Unit finishing: varnished

Electrical characteristics

  • Converter topology: boost, transition mode
  • Core type: PQ32/20-PC44 or equivalent
  • Min. operating frequency: 30 kHz
  • Typical operating frequency: 120 kHz
  • Primary inductance: 240 µH ± 15 % at 1 kHz - 0.25 V (a) Electrical diagram and winding characteristics

Figure 62. PFC coil electrical diagram a. Measured between pins 1,2 and 5,6. Table 3. PFC coil winding data

  • Maximum height from PCB: 22 mm
  • Coil former type: vertical, 6+6 pins (pins #3, 4, 7, 12 are removed)
  • Pin distance: 5.08 mm
  • Row distance: 30.5 mm

Figure 63. PFC coil mechanical aspect

  • MAGNETICA
  • Inductor P/N: 2086.0001 AM08376v1 BOTTOM VIEW (PIN SIDE) ∅ 0.8 (X7) RECOMMENDED PCB HOLE ∅1.2 (X7)

35 MAX

33 MAX

21 MAX

AN3329 Resonant power transformer specifications Doc ID 18376 Rev 1 41/47

8 Resonant power transformer specifications

General description and characteristics

  • Application type: consumer, home appliance
  • Transformer type: open
  • Coil former: horizontal type, 7+7 pins, two slots
  • Max. temp. rise: 45 ºC
  • Max. operating ambient temperature: 60 ºC
  • Mains insulation: acc. to EN60065
  • Converter topology: half bridge, resonant
  • Core type: ETD34-PC44 or equivalent
  • Min. operating frequency: 70 kHz
  • Typical operating frequency: 90 kHz
  • Primary inductance: 660 µH ± 8 % at 1 kHz - 0.25 V(b)
  • Leakage inductance: 112 µH at 100 kHz - 0.25 V(c)

Figure 64. Transformer overall drawing b. Measured between pins 2-4. c. Measured between pins 2-4 with secondary windings with same polarity shorted at time. Table 4. Resonant transformer winding data

  • Maximum height from PCB: 30 mm
  • Coil former type: horizontal, 7+7 pins (pins #1 and 7 are removed)
  • Pin distance: 5.08 mm
  • Row distance: 25.4 mm

Figure 65. Transforme r electrical diagram

  • MAGNETICA
  • Transformer P/N: 1860.0014 Rev. 0.1 8 - 11 SEC - A 4.4 m Ω 2 90x φ 0.1 mm – G1 9 - 10 SEC - B 4.4 m Ω 2 90x φ 0.1 mm – G1 10 - 13 SEC - C 4.4 m Ω 2 90x φ 0.1 mm – G1 12 - 14 SEC - D 4.4 m Ω 2 90x φ 0.1 mm – G1

Table 4. Resonant transformer winding data (continued)

AN3329 Auxiliary flyback transformer specifications Doc ID 18376 Rev 1 43/47

9 Auxiliary flyback transformer specifications

General description and characteristics

  • Application type: consumer, home appliance
  • Transformer type: open
  • Winding type: layer
  • Coil former: horizontal type, 4+5 pins, two slots
  • Max. temp. rise: 45 ºC
  • Max. operating ambient temperature: 60 ºC
  • Mains insulation: acc. to EN60950
  • Unit finishing: varnished
  • Converter topology: flyback, CCM/DCM mode
  • Core type: E20-PC44 or equivalent
  • Typical operating frequency: 60 kHz
  • Primary inductance: 2.380 mH ± 10 % at 1 kHz - 0.25 V(d)
  • Leakage inductance: 30 µH at 50 kHz - 0.25 V(e)
  • Max. peak primary current: 0.5 Apk
  • RMS primary current: 0.17 Arms DC output characteristics
  • Converter topology: flyback, CCM/DCM mode d. Measured between pins 4-5. e. Measured between pins 2-4 with secondary windings with same polarity shorted at time.

Table 5. DC output voltage and load

5 V 2 A DC

Figure 66. Transformer construction Figure 67. Mechanical aspect and pin numbering Table 6. Standby transformer winding data

2 LAYERS POLYESTER TAPE

Figure 68. Mechanical aspect and pin numbering

  • MAGNETICA
  • Inductor P/N: 1715.0059 !-V 0,1 0$; 0$; 0$; 0$; %277209,(: 3,16,'( 3LQLVPLVVLQJ

Table 7. Document revision history 25-Feb-2011 1 Initial release.