View L6590D_382073.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

L6590
FULLY INTEGRATED POWER SUPPLY
s s s s s
s
s s s
WIDE-RANGE MAINS OPERATION "ON-CHIP" 700V V(BR)DSS POWER MOS 65 kHz INTERNAL OSCILLATOR 2.5V 2% INTERNAL REFERENCE STANDBY MODE FOR HIGH EFFICIENCY AT LIGHT LOAD OVERCURRENT AND LATCHED OVERVOLTAGE PROTECTION NON DISSIPATIVE BUILT-IN START-UP CIRCUIT THERMAL SHUTDOWN WITH HYSTERESIS BROWNOUT PROTECTION (SMD PACKAGE ONLY)
MINIDIP
SO16W
ORDERING NUMBERS: L6590N L6590D
s
- HOME APPLIANCES/LIGHTING LINE CARD, DC-DC CONVERTERS
MAIN APPLICATIONS s WALL PLUG POWER SUPPLIES UP TO 15 W s AC-DC ADAPTERS s AUXILIARY POWER SUPPLIES FOR: - CRT AND LCD MONITOR (BLUE ANGEL) - DESKTOP PC/SERVER - FAX, TV, LASER PRINTER TYPICAL APPLICATION CIRCUIT
DESCRIPTION The L6590 is a monolithic switching regulator designed in BCD OFF-LINE technology, able to operate with wide range input voltage and to deliver up to 15W output power. The internal power switch is a lateral power MOSFET with a typical RDS(on) of 13 and a V(BR)DSS of 700V minimum.
AC line 88 to 264 Vac
Pout up to 15W
AC line 88 to 264 Vac
Pout up to 15W
DRAIN
DRAIN
1
1
L6590
3
Vcc
L6590
3 6, 7, 8 5
COMP
Vcc
6, 7, 8
GND COMP
4
5
VFB
4
GND
VFB
Primary Feedback
Secondary Feedback
October 2000
1/23
L6590
DESCRIPTION (continued) The MOSFET is source-grounded, thus it is possible to build flyback, boost and forward converters. The device can work with secondary feedback and a 2.5V2% internal reference, in addition to a high gain error amplifier, makes possible also the use in applications either with primary feedback or not isolated. The internal fixed oscillator frequency and the integrated non dissipative start-up generator minimize the external component count and power consumption. The device is equipped with a standby function that automatically reduces the oscillator frequency from 65 to 22 kHz under light load conditions to enhance BLOCK DIAGRAM
DRAIN (1) [1]
START-UP
efficiency (Pin < 1W @ Pout = 0.5W with wide range mains). Internal protections like cycle-by-cycle current limiting, latched output overvoltage protection, mains undervoltage protection (SMD version only) and thermal shutdown generate a 'robust' design solution. The IC uses a special leadframe with the ground pins (6, 7 and 8 in minidip, 9 to16 in SO16W package) internally connected in order for heat to be easily removed from the silicon die. An heatsink can then be realized by simply making provision of few cm2 of copper on the PCB. Furthermore, the pin(s) close to the high-voltage one are not connected to ease compliance with safety distances on the PCB.
[x] : L6590D (SO16W)
THERMAL SHUTDOWN
SUPPLY & UVLO
VREF
+ -
VCC (3) [4]
OVP
VREF
SGND [5]
BOK [6]
VFB (5) [8]
BROWNOUT
+ + -
GND (6,7,8) PGND [9, ..., 16]
OCP PWM
2.5V
STANDBY
-
OSC 65/22 kHz
+
2.5V
COMP (4) [7]
PIN CONNECTIONS (Top view)
DRAIN DRAIN N.C. Vcc COMP GND GND GND VFB N.C. N.C. Vcc SGND BOK COMP MINIDIP L6590 VFB SO16W L6590D
PGND PGND PGND PGND PGND PGND PGND PGND
2/23
L6590
PIN FUNCTIONS
Pin# Name L6590 1 2 3 L6590D 1 2, 3 4 DRAIN N.C. VCC Drain connection of the internal power MOSFET. The internal high voltage start-up generator sinks current from this pin. Not internally connected. Provision for clearance on the PCB. Supply pin of the IC. An electrolytic capacitor is connected between this pin and ground. The internal start-up generator charges the capacitor until the voltage reaches the startup threshold. The PWM is stopped if the voltage at the pin exceeds a certain value. Output of the Error Amplifier. Used for control loop compensation or to directly control PWM with an optocoupler. Inverting input of the Error Amplifier. The non-inverting one is internally connected to a 2.5V 2% reference. This pin can be grounded in some feedback schemes. Connection of both the source of the internal MOSFET and the return of the bias current of the IC. Pins connected to the metal frame to facilitate heat dissipation. Brownout Protection. If the voltage applied to this pin is lower than 2.5V the PWM is disabled. This pin is typically used for sensing the input voltage of the converter through a resistor divider. If not used, the pin can be either left floating or connected to Vcc through a 15 k resistor. Current return for the bias current of the IC. Connection of the source of the internal MOSFET. Pins connected to the metal frame to facilitate heat dissipation. Description
4 5 6 to 8 -
7 8 6
COMP VFB GND BOK
-
5 9 to 16
SGND PGND
THERMAL DATA
Symbol Rthj-amb Rthj-pins Parameter Thermal Resistance Junction to ambient (*) Thermal Resistance Junction to pins Minidip 35 to 60 15 SO16W 40 to 65 20 Unit C/W C/W
(*) Value depending on PCB copper area and thickness.
ABSOLUTE MAXIMUM RATINGS
Symbol Vds Id Vcc Iclamp Drain Source Voltage Drain Current IC Supply Voltage Vcc Zener Current Error Amplifier Ouput Sink Current Voltage on Feedback Input BOK pin Sink Current Ptot Tj Tstg Power Dissipation at Tamb < 50C (Minidip and SO16W) 3 cm2, 2 oz copper dissipating area on PCB Operating Junction Temperature Storage Temperature -40 to 150 -40 to 150 C C Parameter Value -0.3 to 700 0.7 18 20 3 5 1 1.5 Unit V A V mA mA V mA W
3/23
L6590
ELECTRICAL CHARACTERISTCS (Tj = -25 to 125C, Vcc = 10V; unless otherwise specified)
Symbol POWER SECTION V(BR)DSS Drain Source Voltage Idss RDS(on) Off state drain current Drain-to-Source on resistance RDS(on) vs. Tj: see fig. 20 Id < 200 A; Tj = 25 C Vds = 560V; Tj = 125 C Id = 120mA; Tj = 25 C Id = 120mA; Tj = 125 C 13 23 700 200 16 28 V A Parameter Test Condition Min. Typ. Max. Unit
ERROR AMP SECTION VFB Input Voltage Tj = 25 C Tj = 125C Ib Avol B SVR Isink Isource VCOMPH VCOMPL E/A Input Bias Current DC Gain Unity Gain Bandwidth Supply voltage Rejection Output Sink Current Output Source Current Vout High Vout Low f = 120 Hz VCOMP = 1V VCOMP = 3.5V; VFB = 2V Isource = -0.5mA; VFB=2V Isink = 1mA ; VFB=3V -0.5 3.8 VFB = 0 to 2.5 V open loop 60 0.7 2.45 2.4 2.5 2.5 0.3 70 1 70 1 -1 4.50 1 -2.5 2.55 2.6 5 A dB MHz dB mA mA V V V
OSCILLATOR SECTION Fosc Oscillator Frequency Tj = 25 C 58 52 Dmin Dmax Min. Duty Cycle Max. Duty Cycle VCOMP = 1V VCOMP = 4V 67 70 65 65 72 74 0 73 % % kHz
DEVICE OPERATION SECTION Iop IQ Icharge Operating Supply Current Quiescent Current VCC charge Current fsw = Fosc MOS disabled Vcc = 0V to Vccon - 0.5V; Vds = 100 to 400V; Tj = 25C Vcc = 0V to Vccon - 0.5V; Vds = 100 to 400V VCCclamp VCC clamp Voltage Vccon Vccoff Vdsmin Start Threshold voltage Min operating voltage after Turn on Drain start voltage Iclamp = 10mA (*) (*) (*) -3 -2.5 16.5 14 6 4.5 3.5 -4.5 -4.5 17 14.5 6.5 7 6 -7 -7.5 17.5 15 7 40 mA mA mA mA V V V V
4/23
L6590
ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Test Condition Min. Typ. Max. Unit
CIRCUIT PROTECTIONS Ipklim OVP LEB Pulse-by-pulse Current Limit Overvoltage Protection Masking Time di/dt = 120 mA/ s Icc = 10 mA (*) After MOSFET turn-on (**) 550 16 625 16.5 120 700 17 mA V ns
STANDBY SECTION FSB Ipksb Ipkno Oscillator Frequency Peak switch current for Standby Operation Peak switch current for Normal Operation Transition from Fosc to FSB Transition from FSB to Fosc 19 22 80 190 25 kHz mA mA
BROWNOUT PROTECTION (L6590D only) Vth IHys VCL Threshold Voltage Current Hysteresis Clamp Voltage Voltage either rising or falling Vpin = 3V Ipin = 0.5 mA 2.4 -30 5.6 2.5 -50 6.4 2.6 -70 7.2 V A V
THERMAL SHUTDOWN (***) Threshold Hysteresis
(*) Parameters tracking one the other (**) Parameter guaranteed by design, not tested in production (***) Parameters guaranteed by design, functionality tested in production
150
165 40
C C
Figure 1. Start-up & UVLO Thresholds
Vcc [V]
Figure 2. Start-up Current Generator
Icc [mA]
16 14 12 10 8 6 -50
UVLO Start-up
5.5
Vdrain = 40 V
5 4.5 4 3.5
Tj = -25 C
Tj = 25 C
Tj = 125 C
0
50
Tj [C]
100
150
3
0
2
4
6
Vcc [V]
8
10
12
5/23
L6590
Figure 3. Start-up Current Generator
Icc [mA]
Figure 6. IC Operating Current
Icc [mA]
5.5
Vdrain = 60 V Tj = -25 C
5
VFB = 2.3 V fsw = 65 kHz Tj = 125 C Tj = 25 C
5
Tj = 25 C
4.5
4.5 4 4
Tj = 125 C Tj = -25 C
3.5 3
3.5
0
2
4
6
Vcc [V]
8
10
12
3
7
8
9
10
11
Vcc [V]
12
13
14
15
Figure 4. IC Consumption Before Start-up
Icc [A]
Figure 7. IC Operating Current
Icc [mA]
700 600 500 400 300 200 100 7 8 9 10 11
Vcc [V]
4.4
Tj = -25 C
4.2 4
VFB = 2.3 V fsw = 22 kHz
Tj = 125 C
Tj = 25 C Tj = 25 C Tj = 125 C
3.8 3.6 3.4 3.2
Tj = -25 C
12
13
14
15
3
7
8
9
10
11
Vcc [V]
12
13
14
15
Figure 5. IC Quiescent Current
Icc [mA]
Figure 8. Switching Frequency vs. Temperature
fsw [kHz]
4
VFB = 2.7 V Tj = 25 C
80 70 60 50
Normal operation
3.8 3.6 3.4 Tj = 125 C 3.2 3
Tj = -25 C
40 30 20
Standby
6
8
10
12
Vcc [V]
14
16
18
10 -50
0
50
Tj [C]
100
150
6/23
L6590
Figure 9. Vcc clamp vs. Temperature
VCCclamp [V]
Figure 12. OCP threshold vs. Temperature
Ipklim / (Ipklim @ Tj = 25C)
18 17.8 17.6 17.4
Iclamp = 10 mA Iclamp = 20 mA
1.1 1.08 1.06 1.04 1.02 1 0 50
Tj [C]
di/dt = 120 mA/s
17.2 17 -50
100
150
0.98 -50
0
50
Tj [C]
100
150
Figure 10. OVP Threshold vs. Temperature
Vth [V]
Figure 13. Internal E/A Reference Voltage
Vref [V]
16 15.8 15.6
2.6
2.55
2.5 15.4 15.2 15 -50 2.45
0
50
Tj [C]
100
150
2.4 -50
0
50
Tj [C]
100
150
Figure 11. OCP Threshold vs. Current Slope
Ipklim / (Ipklim @ di/dt = 120 mA/s)
Figure 14. Error Amplifier Slew Rate
VCOMP [V]
1.06 1.04 1.02 1 0.98 0.96 50
Tj = 25 C
5 4 3 VFB 2 1 0 100 150
dI/dt [mA/s]
VCOMP
RL = 10 k CL = 100 pF open loop
200
250
0
2
4
6
8
t [s]
10
12
14
16
7/23
L6590
Figure 15. COMP pin Characteristic
VCOMP [V]
Figure 18. Breakdown Voltage vs. Temperature
BVDSS / (BVDSS @ Tj = 25C)
6 5 4 3 2 1 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4
VFB = 0 Tj = 25 C
1.08 1.06 1.04 1.02 1 0.98 0.96 0.94 0.92 -50 0 50
Tj [C]
Idrain = 200 A
100
150
ICOMP [mA]
Figure 16. COMP pin Dynamic Resistance vs. Temperature
RCOMP [kOhm]
Figure 19. Drain Leakage vs. Drain Voltage
Idrain [A]
50
10.5 10 9.5 9 8.5 8 -50 10 100 0 50
Tj [C]
Tj = 125 C Tj = 25 C
VFB = 0
40
30
Tj = -25 C
20
200
300
400
Vdrain [V]
500
600
700
100
150
Figure 20. Rds(ON) vs. Temperature Figure 17. Error Amplifier Gain and Phase
Rds(ON) / (Rds(ON) @ Tj=25C)
1.8
dB
Phase
0
1.6 1.4
Idrain = 120 mA
100 50
Gain
90
m
1.2 1
0
180
0.8
1 10 100 1M f [Hz] 1k 10k 100k
0.6 -50
0
50
Tj [C]
100
150
8/23
L6590
Figure 21. Rds(ON) vs. Idrain
Rds(ON) / (Rds(ON) @ Idrain=120 mA)
Figure 22. Coss vs. Drain Voltage
Coss [pF]
1.3
Tj = 25 C
250
Tj = 25 C
1.2
200 150
1.1 100 1 50 0
0.9
0
100
200
300
Idrain [mA]
400
500
600
0
100
200
300
400
500
600
700
Vdrain [V]
Figure 23. Standby Function Thresholds
Drain Peak Current [mA]
220 200 180 160 140 120 100 80 60 -50 0 50
Tj [C]
22 kHz 65 kHz
65 kHz 22 kHz
100
150
9/23
L6590
Figure 24. Test Board (1) with Primary Feedback: Electrical Schematic
F1 2A/250V BD1 DF06M
T1 D1 BZW06-154 D2 STTA106 R1 68
Vin 88 to 264 Vac
D4 BYW100-100
L1 4.7 H
Vo =12 V 10% Po= 1 to 10 W
C1 22 F 400 V
C7, C8 330 F 16 V
C9 100 F 16 V
IC1 1 3
R2 5.6 k
D3 C2 22 F 1N4148 25 V C4 100 nF C7 2.2 nF Y
L6590
6, 7, 8
5
C5 R3 680 nF 1.1 k
4 C6 10 nF
R5 110
R4 1.5 k
T1 specification Core E20/10/6, ferrite 3C85 or N67 or equivalent 0.5 mm gap for a primary inductance of 2.9 mH Lleakage <90 H Primary : 180 T, 2 series windings 90T each, AWG33 ( 0.22 mm) Sec : 19 T, AWG30 ( 0.3 mm) Aux : 19 T, AWG33
Figure 25. Test Board (1) Evaluation Data
Load & Line regulation
Output Voltage [V] Efficiency [%]
Efficiency
86
13.5
1W
84 82
13 12.5 12 11.5 50
2.5 W 5W Pout = 10 W
Pout = 10 W 5W
80 78 76 74
2.5 W
1W
100
150
200
250
300
72 50
100
150
200
250
300
Input Voltage [Vac]
Input Voltage [Vac]
10/23
L6590
Figure 26. Test Board (1) Main Waveforms
Ch3: Idrain Ch3: Idrain
Vin = 100 VDC Pout = 10 W
Vin = 400 VDC Pout = 10 W
Ch2: Vdrain
Ch2: Vdrain
Ch3: Idrain
Ch3: Idrain
Vin = 100 VDC Pout = 1 W
Vin = 400 VDC Pout = 1 W
Ch2: Vdrain Ch2: Vdrain
Figure 27. Test Board (2) with Secondary Feedback: Electrical Schematic
F1 2A/250V L 22 mH CxB 100 nF BD1 DF06M
Vin 88 to 264 Vac
CxA 100 nF
T1 D1 BZW06-154 D2 STTA106 R1 10 C2 22 F 25V D3 1N4148
D4 1N5822
L1 4.7 H
5 Vdc / 2 A
C1 22 F 400 V
C5, C6, C7 470 F 16V Rubycon ZL
C8 220 F 10V Rubycon ZL
1 IC1
3 4
R2 560
L6590
6, 7, 8
5
C3 22 nF
OP1 PC817 R6 6.8 k
4 3
1 2
R5 2 k
C9 100 nF
R3 2.43 k
1 2 3
C4 2.2 nF Y1 class
IC2 TL431
R4 2.43 k
T1 specification Core E20/10/6, ferrite 3C85 or N67 or equivalent 0.6 mm gap for a primary inductance of 1.4 mH Lleakage <30 H Primary : 128 T, 2 series windings 64T each, AWG32 ( 0.22 mm) Sec : 6 T, 4xAWG32 Aux : 14 T, AWG32
11/23
L6590
Figure 28. Test Board (2) evaluation data
Load & Line regulation
Output Voltage [V] Efficiency [%]
Efficiency
80
264 VAC 88 VAC
5 4.98 4.96 4.94 4.92 4.9 0.003
220 VAC
70 60
110 VAC
50 40
110 VAC 88 VAC
264 VAC
220 VAC
30 20 0.003 0.01 0.03 0.1 0.3 1 3
0.01
0.03
0.1
0.3
1
3
Load Current [A]
Load Current [A]
Light-load Consumption
Input Power [mW]
Pdiss [W]
Device Power Dissipation
5
1,000 800 600
0.25W Pout 0.5W
Rthj-amb= 58 C/W @ 1.5W 2 1 0.5 0.2 0.1 0.05 0.003 0.01 0.03 0.1 0.3 1 220 VAC 264 VAC
88 VAC
400 200 0 50
0.1W 0.05W 0W
110 VAC
100
150
200
250
300
350
400
450
3
DC Input Voltage [V]
Load Current [A]
Figure 29. Test Board (2) EMI Characterization
12/23
L6590
Figure 30. Test Board (2) Main Waveforms
Ch1: Vdrain A1: Idrain
Vin = 100 VDC Iout = 2 A A1: Idrain Ch1: Vdrain
Vin = 400 VDC Iout = 2 A
A1: Idrain A1: Idrain Vin = 100 VDC Iout = 50 mA Vin = 400 VDC Iout = 50 mA
Ch1: Vdrain
Ch1: Vdrain
Figure 31. Test Board (2) Load Transient Response
Vout
Vout
Iout Iout
Standby Function is not tripped
Standby Function is tripped
Vin = 200 VDC Iout = 0.2 0.4 A
transition 22 65 kHz
transition 65 22 kHz
Vin = 200 VDC Iout = 0.1 0.3 A
13/23
L6590
APPLICATION INFORMATION In the following sections the functional blocks as well as the most important internal functions of the device will be described. Start-up Circuit When power is first applied to the circuit and the voltage on the bulk capacitor is sufficiently high, an internal high-voltage current generator is sufficiently biased to start operating and drawing about 4.5 mA through the primary winding of the transformer and the drain pin. Most of this current charges the bypass capacitor connected between pin Vcc (3) and ground and makes its voltage rise linearly. As the Vcc voltage reaches the start-up threshold (14.5V typ.) the chip, after resetting all its internal logic, starts operating, the internal power MOSFET is enabled to switch and the internal high-voltage generator is disconnected. The IC is powered by the energy stored in the Vcc capacitor until the self-supply circuit (typically an auxiliary winding of the transformer) develops a voltage high enough to sustain the operation. As the IC is running, the supply voltage, typically generated by a self-supply winding, can range between 16 V (Overvoltage protection limit, see the relevant section) and 7 V, threshold of the Undervoltage Lockout. Below this value the device is switched off (and the internal start-up generator is activated). The two thresholds are in tracking. The voltage on the Vcc pin is limited at safe values by a clamp circuit. Its 17V threshold tracks the Overvoltage protection threshold. Figure 32. Start-up circuit internal schematic
DRAIN
15 M
POWER MOSFET
UVLO
Vcc
150
17 V
GND
Power MOSFET and Gate Driver The power switch is implemented with a lateral N-channel MOSFET having a V(BR)DSS of 700V min. and a typical RDS(on) of 13. It has a SenseFET structure to allow a virtually lossless current sensing (used only for protection). During operation in Discontinuous Conduction Mode at low mains the drain voltage is likely to go below ground. Any risk of injecting the substrate of the IC is prevented by an internal structure surrounding the switch. The gate driver of the power MOSFET is designed to supply a controlled gate current during both turn-on and turn-off in order to minimize common mode EMI. Under UVLO conditions an internal pull-down circuit holds the gate low in order to ensure that the power MOSFET cannot be turned on accidentally.
14/23
L6590
Figure 33. PWM Control internal schematic
Max. Duty cycle
S OSCILLATOR Clock R Q to gate driver
+ PWM +
from OCP comparator
E/A
-
COMP
VFB
Oscillator and PWM Control PWM regulation is accomplished by implementing voltage mode control. As shown in fig. 33, this block includes an oscillator, a PWM comparator, a PWM latch and an Error Amplifier. The oscillator operates at a frequency internally fixed at 65 kHz with a precision of 10 %. The maximum duty cycle is limited at 70% typ. The PWM latch (reset dominant) is set by the clock pulses of the oscillator and is reset by either the PWM comparator or the Overcurrent comparator. The Error Amplifier (E/A) is an op-amp with a MOS input stage and a class AB output stage. The amplifier is compensated for closed loop stability at unity gain, has a small-signal DC gain of 70 dB (typ.) and a gain-bandwidth product over 1 MHz. In case of overcurrent the error amplifier output saturates high and the conduction of the power MOSFET is stopped by the OCP comparator instead of the PWM comparator. Under zero load conditions the error amplifier is close to its low saturation and the gate drive delivers as short pulses as it can, limited by internal delays. They are however too long to maintain the long-term energy balance, thus from time to time some cycles need being skipped and the operation becomes asynchronous. This is automatically done by the control loop. Standby Function The standby function, optimized for flyback topology, automatically detects a light load condition for the converter and decreases the oscillator frequency. The normal oscillation frequency is automatically resumed when the output load builds up and exceeds a defined threshold. This function allows to minimize power losses related to switching frequency, which represent the majority of losses in a lightly loaded flyback, without giving up the advantages of a higher switching frequency at heavy load. The Standby function is realized by monitoring the peak current in the power switch. If the load is low that it does not reach a threshold (80 mA typ.), the oscillator frequency will be set at 22 kHz typ. When the load demands more power and the peak primary current exceeds a second threshold (190 mA typ.) the oscillator frequency is reset at 65 kHz. This 110 mA hysteresis prevents undesired frequency change when power is such that the peak current is close to either threshold. The signal coming from the sense circuit is digitally filtered to avoid false triggering of this function as a result of large load changes or noise.
15/23
L6590
Figure 34. Standby Function timing diagram
Pout
0000000000000000000000000000000000000000000000 80 mA 190 mA Peak 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 Primary 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 Current 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000 0000000000000000000000000000000000000000000000
Load regulation
Vout
small glitch
STANDBY (before filter)
2 ms
1 ms
STANDBY (filtered)
fsw
65 kHz 22 kHz
Brownout Protection (L6590D only) Brownout Protection is basically a not-latched device shutdown functionality. It will typically be used to detect a mains undervoltage (brownout). This condition may cause overheating of the primary power section due to an excess of RMS current. Figure 35. Brownout Protection Function internal schematic and timing diagram
HV Input bus VON VOFF
HV Input bus Vcc
VinOK
50 A BOK
+
Vcc
VinOK 6.4 V
-
2.5 V
L6590D
PWM
000000000000000000000 000000000000000000000 000000000000000000000 000000000000000000000 000000000000000000000 000000000000000000000 000000000000000000000 000000000000000000000
Vout
16/23
L6590
Another problem is the spurious restarts that are likely to occur during converter power down if the input voltage decays slowly (e.g. with a large input bulk capacitor) and that cause the output voltage not to decay to zero monothonically. Converter shutdown can be accomplished with the L6590D by means of an internal comparator that can be used to sense the voltage across the input bulk capacitor. This comparator is internally referenced to 2.5V and disables the PWM if the voltage applied at its non-inverting input, externally available, is below the reference. PWM operation is re-enabled as the voltage at the pin is more than 2.5V. The brownout comparator is provided with current hysteresis instead of a more usual voltage hysteresis: an internal 50 A current generator is ON as long as the voltage applied at the non-inverting input exceeds 2.5V and is OFF if the voltage is below 2.5V. This approach provides an additional degree of freedom: it is possible to set the ON threshold and the OFF threshold separately by properly choosing the resistors of the external divider, which is not possible with voltage hysteresis. Overvoltage Protection The IC incorporates an Overvoltage Protection (OVP) that can be particularly useful to protect the converter and the load against voltage feedback loop failures. This kind of failure causes the output voltage to rise with no control and easily leads to the destruction of the load and of the converter itself if not properly handled. If such an event occurs, the voltage generated by the auxiliary winding that supplies the IC will fly up tracking the output voltage. An internal comparator continuously monitors the Vcc voltage and stops the operation of the IC if the voltage exceeds 16.5 V. This condition is latched and maintained until the Vcc voltage falls below the UVLO threshold. The converter will then operate intermittently. Figure 36. OVP internal schematic
Vcc
DRAIN to MOSFET to OVP latch
+
OVP
-
GND
Overcurrent Protection The device uses pulse-by-pulse current limiting for Overcurrent Protection (OCP), in order to prevent overstress of the internal MOSFET: its current during the ON-time is monitored and, if it exceeds a determined value, the conduction is terminated immediately. The MOSFET will be turned on again in the subsequent switching cycle. As previously mentioned, the internal powerMOSFET has a SenseFET structure: the source of a few cells are connected together and kept separate from the other source connections so as to realize a 1:100 current divider. The "sense" portion is connected to a ground referenced, sense resistor having a low thermal coefficient. The OCP comparator senses the voltage drop across the sense resistor and resets the PWM latch if the drop exceeds a threshold, thus turning off the MOSFET. In this way the overcurrent threshold is set at about 0.65 A (typical value).
17/23
L6590
At turn-on, there are large current spikes due to the discharge of parasitic capacitances and, in case of Continuos Conduction Mode operation, to secondary diode reverse recovery as well, which could falsely trigger the OCP comparator. To increase noise immunity the output of the OCP comparator is blanked for a short time (about 120 ns) just after the MOSFET is turned on, so that any disturbance within this time slot is rejected (Leading Edge Blanking). Figure 37. OCP internal schematic
DRAIN Max. Duty cycle
S OSCILLATOR Clock R Q
Driver
1 1/100
+ PWM + OCP -
Rsense
Clock
LEB
0.5 V GND
Thermal Shutdown Overheating of the device due to an excessive power throughput or insufficient heatsinking is avoided by the Thermal Shutdown function. A thermal sensor monitors the junction temperature close to the power MOSFET and, when the temperature exceeds 150 C (min.), sets an alarm signal that stops the operation of the device. This is a not-latched function and the power MOSFET is re-enabled as the temperature falls about 40 C.
18/23
L6590
APPLICATION IDEAS Figure 38. 10W AC-DC adapter with no isolation
F1 2A/250V CxA 100 nF L 22 mH CxB 100 nF BD1 DF06M C1 22 F 400 V
T1 D1 BZW06-154 D2 STTA106 R1 10
Vin 88 to 264 Vac
D4 STPS3L60S
L1 4.7 H
Vo =12 V 3% Io= 0 to 0.8 A
C7, C8 330 F 16 V
C9 100 F 16 V
IC1 1 3 (4) C4 R3 100 nF 27 k
C2 22 F 25 V
D3 1N4148 R2 3.9 k
L6590 (L6590D)
6, 7, 8 (9 to 16)
4 (7)
5 (8)
C5 2.2 nF
R4 1 k
T1 specification Core E20/10/6, ferrite 3C85 or N67 or equivalent 0.5 mm gap for a primary inductance of 1.6 mH Lleakage <30 H Primary : 130 T, 2 series windings 65T each, AWG33 ( 0.22 mm) Sec : 14 T, AWG26 ( 0.4 mm)
Figure 39. 15W Auxiliary SMPS for PC
Vin = 200 to 375 Vdc D1 BZW06-154 D2 STTA106 R1 10 R2 1.8 M
1 4
T1
D4 STPS10L25D
L1 4.7 H
5 Vdc / 3 A
C5, C6, C7 470 F 10 V
C8 100 F 10V
C2 22 F 25 V
D3 1N4148 R4 560 R5 2.43 k
IC1
6
L6590D
5
7
C1 10 nF R3 20 k
8
9, ..., 16
C3 47 nF
4
1
OP1 PC817
3 2
R7 240 C9 470 nF IC2 TL431 R6 2.43 k
1
3
C4 2.2 nF Y
2
T1 specification Core E20/10/6, ferrite 3C85 or N67 or equivalent 0.9 mm gap for a primary inductance of 2 mH Lleakage <50 H Primary : 200 T, 2 series windings 100T each, AWG33 ( 0.22 mm) Sec : 9 T, 2 x AWG23 ( 0.64 mm) Aux : 21 T, AWG33
19/23
L6590
Figure 40. 7.2V/7W Battery Charger
F1 2A/250V CxA 100 nF L 22 mH CxB 100 nF BD1 DF06M
T1 16:1
D1 BZW06-154
D5 1N4148
R5 4.7 k
Q1 BC337
Vin 88 to 264 Vac
7.2 Vdc / 1 A
C1 22 F 400 V D2 STTA106
3 4
C5, C6 330 F 16V
D3 BAV21 D4 1N5821
D8 BZX79C12
C7 10 F 25V
R2 5.6 k 1 3 (4)
R1 39
C3 10 F 25V
R6 0.1 R8 560
C8 680 nF
C2 220 nF
R7 620
L6590 (L6590D)
6, 7, 8 (9 to 16)
R9 22.6 k R10 6.8 k
5 (8)
4 (7) R4 10 k
OP1 PC817
1
R11
2
11.8 k
5 6 8 3
C3 10 nF
R3 1.5 k
C4 2.2 nF Y1 class
R12 1 k
D6 1N4148 D7 1N4148
IC2 7 TSM103 2
1 4
R13 12 k C9 330 nF
T1 specification Core E20/10/6, ferrite 3C85 or N67 or equivalent 1 mm gap for a primary inductance of 2.6 mH Lleakage <60 H Primary : 230 T, 2 series windings 115T each, AWG36 ( 0.16 mm) Sec : 13 T, AWG23 ( 0.64 mm) Aux : 60 T, AWG36
REFERENCES [1] "Getting Familiar with the L6590 Family, High-voltage Fully Integrated Power Supply" (AN1261) [2] "Offline Flyback Converters Design Methodology with the L6590 Family" (AN1262)
20/23
L6590
21/23
L6590
22/23
L6590
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics 2000 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com
(R)
23/23

▲Up To Search▲

Price & Availability of L6590D

	To Download L6590D Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .