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NCP1239

http://onsemi.com

Actual Peak Current

High Input
Voltage

Low Input
Voltage

Vopl/Rsense

Wished Maximum

Peak Current

Figure 49.

The propagation delay (

t) produces overcurrents (

at low line,

at high line in the figure) that are proportional to the input

voltage. As a consequence, the actual maximum current and then the power limit gets higher when the AC line increases.

I max

Vocp

Rsense

)

Vin

, where Vin is the converter

input voltage and

t is the total delay in turning off the

power switch.

The NCP1239 enables the compensation of the second

term in the Imax equation for a precise limitation of the peak
current. A current source (I

pin9

) proportional to the Pin 5

voltage flows out of Pin 9. Since Pin 5 receives a voltage
proportional to the input voltage for brown−out detection,
I

pin9

is proportional to the input voltage too. An external

resistor Rcomp can be connected between Pin 9 and the
positive terminal of Rsense, so that Pin 9 monitors the
following voltage:

Vpin9

[Rsense

(Ip

)

Ipin9)]

)

(Rcomp

Ipin9)

pin9

being small compared to the inductor current, the Pin 9

voltage simplifies as follows:

Vpin9

(Rsense

Ip)

)

(Rcomp

Ipin9)

pin9

is proportional to the Pin 5 voltage (80

A/V*V

pin5

–

see parameters specification table) and V

pin5

is a portion of

the input voltage (V

pin5

= k

*Vin). Finally,

Ipin9

kBO

Vin

The voltage V

pin9

is compared to the internal reference

Vocp. When V

pin9

reaches Vocp, the corresponding

threshold current (Ipth) is deducted from:

Vopl

(Rsense

Ipth)

)

(Rcomp

kBO

Vin)

Then,

Ipth

Vopl

(Rcomp

kBO

Vin)

Rsense

Taking into account the overcurrent resulting from the
propagation delays, the maximum current is finally:

I max

Vocp

Rsense

Rcomp

kBO

Vin

Rsense

)

Vin

Choosing Rcomp so that

Rcomp

kBO

Rsense

)

the current limit is made constant in the whole input voltage
range (Imax = Vocp/Rsense).

As an example, let’s assume that:

− the minimum input voltage for operation is 100 V =>
k

=0.5/100=0.005,

− Rsense is 0.25

− Lp=500

− The total propagation delays are

t = 350 ns,

Then, the Rcomp resistor should be:

Rcomp

Rsense

kBO

350 n

0.25

0.005

500 m

[

438

Содержание NCP1239FDR2

Страница 1: ...eriod Internal Frequency Dithering for Improved EMI Signature Go to Standby Signal for PFC Front Stage Large VCC Operation from 12 2 V to 36 V 500 mV Overcurrent Limit 500 mA 800 mA Peak Current Capab...

Страница 2: ...OVP GND Vout Rbo1 GND Rcomp Cbo 5 12 6 7 8 11 10 9 Rramp VCC REF5V REF5V 5V 10mA Css Rbo2 Rt NTC Thermistor Figure 2 NCP1239V Typical Application Example Cbulk Vbulk to PFC_VCC BO 1 16 2 3 4 15 14 13...

Страница 3: ...CC Going up 13 15 5 16 4 17 5 V VCCOFF Minimum Operating Voltage after Turn on 13 10 5 11 2 12 2 V HYST1 Difference VCCON VCCOFF 13 4 5 5 1 V VCCLATCH VCC Decreasing Level at which the Latch off Phase...

Страница 4: ...aded by 1 nF 10 130 220 ns TLEB 65kHz Leading Edge Blanking Duration Pins 9 and 10 65 kHz NCP1239F 9 10 420 ns TLEB 130kHz Leading Edge Blanking Duration Pins 9 and 10 130 kHz NCP1239F 9 10 230 ns TLE...

Страница 5: ...in standby state Pin 8 grounded Vpin6 4 5 V VCC 12 5 V 1 4 0 8 0 18 k Igts Sink Current Source in Normal Mode Vpin8 2 V Pin 7 open VCC Vpin1 0 7 V 1 0 6 1 0 mA FB skip Default Feedback Level for Skip...

Страница 6: ...the fault is confirmed and the circuit enters an auto recovery burst mode otherwise the pin goes back to a lower value and oscillates to perform frequency jittering 7 Skip Adjust Adjust skip level By...

Страница 7: ...nt Stby_detect Error_Flag Stby OVL OVL Vcc 7V stdwn Vstop PWM Latch Output Buffer BO_out Jittering Modulation Jittered Reference Jittering Modulation CLK CLK 0 5V BO_in Soft Start Ipk limit Soft Start...

Страница 8: ...ment Stby_detect Error_Flag Stby OVL OVL Vcc 7V stdwn Vstop PWM Latch Output Buffer BO_out Jittering Modulation Jittered Reference Jittering Modulation CLK CLK BO_in Soft Start Ipk limit Soft Start Ip...

Страница 9: ...STICS Figure 7 High Voltage Current Source vs Temperature VCC 0 V TEMPERATURE C 125 100 75 50 25 25 I C2 mA 6 0 0 5 0 4 0 3 0 2 0 1 0 0 Figure 8 High Voltage Pin Leakage Current vs Temperature 125 TEM...

Страница 10: ...igure 13 NCP1239F Circuit Consumption 1 nF on driver Pin 12 vs Temperature 130 kHz 4 5 5 0 100 kHz 65 kHz 0 TEMPERATURE C 125 100 75 50 25 25 I CC2 mA Figure 14 NCP1239V Circuit Consumption 1 nF on dr...

Страница 11: ...max K osc kHz k 130 kHz 77 78 80 82 Figure 19 Driver Voltage Clamp vs Temperature Figure 20 Maximum Duty Cycle vs Temperature NCP1239F Figure 21 Oscillator Kosc Parameter vs Temperature Kosc fsw Rpin4...

Страница 12: ...Temperature NCP1239F 0 0 506 0 504 0 502 0 500 0 498 0 496 0 494 0 492 TEMPERATURE C 125 100 75 50 25 25 BO_H V 0 510 TEMPERATURE C 125 100 75 50 25 25 FB stby out mV 780 0 0 TEMPERATURE C 125 100 75...

Страница 13: ...Figure 30 Fault Detect Threshold vs Temperature TEMPERATURE C 125 100 75 50 25 Dmax 24 5 0 Figure 31 Maximum Duty Cycle vs Temperature Vpin9 1 V NCP1239V Figure 32 Kdmax Coefficient vs Temperature Vpi...

Страница 14: ...100ms Fault confirmed New Startup attempt SS timer pin 0 9 V Error flag 0 9 V Error flag Fault Management This time is programmed by the Pin 6 capacitor Cpin6 390 nF nearly sets the following interva...

Страница 15: ...ect latch is reset 100ms 100ms delay FB skip Vpin7 FB stby out 1 7 Vpin7 4 3V 3 0V 1 8V Bunches of pulses Standby Detection This time is programmed by the Pin 6 capacitor Cpin6 390 nF nearly sets the...

Страница 16: ...tage The NCP1239 incorporates an internal logic that is able to detect a standby situation Pin1 state changes in accordance to the detected mode standby or normal mode Simply connect a pnp transistor...

Страница 17: ...e 0 9 V setpoint clamp during the startup period but also anytime an overload occurs an internal error flag is asserted testifying that the system is pushed to the maximum power At that moment a 100 m...

Страница 18: ...rt Time Tss 7 5 ms Jittering Period Tjittering 10 ms Fault Detection Delay Tdelay 100 ms More generally the times approximately depend on Cpin6 as follows Tss 7 5 ms Cpin6 390 nF Tjittering 10 ms Cpin...

Страница 19: ...e maximum peak setpoint is reached the internal 0 9 V Zener diode actively clamping the current amplitude to 0 9 V Rsense During this time the NCP1239 asserts an error flag A maximum current condition...

Страница 20: ...ely depend on Cpin6 as follows Tss 7 5 ms Cpin6 390 nF Tjittering 10 ms Cpin6 390 nF Tdelay 100 ms Cpin6 390 nF Figure 38 Vcc PWM Timer 0 9V flag PFC Vcc regulation 100ms 16 4V 11 2V 6 9V 100ms 100ms...

Страница 21: ...dependently of the auxiliary voltage level In auxiliary supply based power supplies it is necessary that the isolated secondary output conditions properly reflects on the non isolated auxiliary windin...

Страница 22: ...rted high a 100 ms timer gets started If the error flag keeps asserted during the 100 ms period then the controller detects a true fault condition and stops pulsing the output If this is a simple tran...

Страница 23: ...s the pulses flow The 100 ms delay could be shortened or lengthened by changing the Pin 6 capacitor VCCOFF VCC VCCON Figure 42 Drv 100ms 100ms t1 t2 t3 t 1 t 2 Latch off phase level Logic reset level...

Страница 24: ...CC higher than VCCOFF As a consequence the final duty cycle is lower than previously estimated longer than the switching phase period In this case the circuit detects an overload condition simply beca...

Страница 25: ...to be detected If the thermistor is a PTC it must be placed between Pin 3 and ground One must place a resistor between the 5 V reference voltage and Pin 3 Similarly the resistor must be selected so th...

Страница 26: ...ing VBO Vtrip 2 The best way to assess the right value of Cfil is to use a simple simulation sketch as the one depicted by Figure 46 A behavioral source loads the rectified DC line and adjusts itself...

Страница 27: ...ine V timing Vline bulk V2 timing 0 PWL 0 0 2 3s 1 7s 1 10s 0 2 V1 line 0 SIN 0 150 50 PSpice EBbrown Value IF V CMP 3 250m 0 PSpice EBload Value IF V CMP 3 35 V bulk 0 A simple simulation configurati...

Страница 28: ...d to provide the output with more power than normally necessary To the light of these statements it becomes interesting to accurately limit the amount of power drawn from the AC line in fault conditio...

Страница 29: ...that Pin 9 monitors the following voltage Vpin9 Rsense Ip Ipin9 Rcomp Ipin9 Ipin9 being small compared to the inductor current the Pin 9 voltage simplifies as follows Vpin9 Rsense Ip Rcomp Ipin9 Ipin...

Страница 30: ...time Practically the Pin 9 voltage is compared to the positive ramp of the internal oscillator and the power switch is allowed to be on only when the ramp is below Vpin9 Then the maximum on time is g...

Страница 31: ...activated when VCC ramps up either from zero fresh power on sequence or 6 9 V the latch off threshold after an overload detection OVL for instance Figure 51 shows the soft start behavior The time scal...

Страница 32: ...he ramp is disabled during standby i e when pfcON is low This inhibition avoids that the ramp compensation modifies the setpoint above which the NCP1239 enables PFC Frequency Jittering Frequency jitte...

Страница 33: ...s Lp primary inductance 350 H fsw switching frequency 65 kHz Ip skip 600 mA or 140 mV Rsense The theoretical power transfer is therefore 1 2 Lp Ip2 fsw 4 W If this IC enters skip cycle mode with a bun...

Страница 34: ...econd comparator COMP2 compares the feedback voltage FB or Vpin8 to 1 7 Vpin7 As long as the load keeps light FB does not exceed 1 7 Vpin7 i e 0 74 V typical if no voltage is forced to Pin 7 A timer c...

Страница 35: ...uctance of 250 H To pass 120 W we assume that a peak current of 4 2 A was needed Due to these numbers we can easily now when the GTS signal will be asserted Lp primary inductance 250 H 85 fsw switchin...

Страница 36: ...VCC as soon as the FB pin voltage has gone below a threshold about 2 7 V that is when the internal error flag stops being asserted Figure 61 Overload Conditions The feedback voltage goes high and asse...

Страница 37: ...As a consequence the FB pin voltage goes below the Vskip threshold and the soft start timer counts about 100 ms if Cpin6 330 nF When the 100 ms time has elapsed the PFC VCC stops being fed Figure 63...

Страница 38: ...t convey any license under its patent rights nor the rights of others SCILLC products are not designed intended or authorized for use as components in systems intended for surgical implant into the bo...

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