Datasheet NCP4328 (ON Semiconductor) - 7
| 制造商 | ON Semiconductor |
| 描述 | Secondary Side Controller, Constant Voltage / Constant Current (CV / CC) |
| 页数 / 页 | 12 / 7 — NCP4328. TYPICAL CHARACTERISTICS. Figure 13. LED Switching Frequency at. … |
| 文件格式/大小 | PDF / 254 Kb |
| 文件语言 | 英语 |
NCP4328. TYPICAL CHARACTERISTICS. Figure 13. LED Switching Frequency at. Figure 14. RSW at VCC = 15 V. VCC = 15 V
该数据表的模型线
文件文字版本
link to page 8 link to page 8 link to page 7 link to page 7 link to page 7
NCP4328 TYPICAL CHARACTERISTICS
1.40 100 1.30 90 80 1.20 ) W 70 (kHz) ( 1.10 SW2 60 R f SWLED 1.00 50 0.90 40 0.80 30 −40 −20 0 20 40 60 80 100 120 −40 −20 0 20 40 60 80 100 120 TJ (°C) TJ (°C)
Figure 13. LED Switching Frequency at Figure 14. RSW at VCC = 15 V VCC = 15 V APPLICATION INFORMATION
Typical application circuit for NCP4328A is shown in R3 ) R4 V + V (eq. 1) Figures 15 and 16 shows typical application circuit for OUT REF R4 NCP4328B that includes internal LED driver for indication purpose.
Current Regulation
The output current is sensed by the shunt resistor R5 in
Power Supply
series with the load. Voltage drop on R5 is compared with The NCP4328 is designed to operate from a single supply internal precise voltage reference VREFC at ISNS up to 36 V. It starts to operate when VCC voltage reaches transconductance amplifier input. 3.5 V and stops when VCC voltage drops below 2.5 V. VCC Voltage difference is amplified by gmC to output current can be supplied by direct connection to the VOUT voltage of amplifier, connected to FBC pin. Compensation network of the power supply. It is highly recommended to add a RC is connected between this pin and ISNS input to provide filter (R1 and C2) in series from VOUT to VCC pin to reduce frequency compensation for current regulation path. voltage spikes and drops that are produced at the converter’s Resistor R6 separates compensation network from sense output capacitors. Recommended values for this filter are resistor. Compensation network works into low impedance 220 W and 1 mF. without this resistor that significantly decreases compensation network impact.
Voltage Regulation Path
Current regulation point is set to current given by The output voltage is detected on the VSNS pin by the R3 Equation 2. and R4 voltage divider. This voltage is compared with the internal precise voltage reference. The voltage difference is VREFC I + (eq. 2) amplified by gm OUTLIM V of the transconductance amplifier. The R5 amplifier output current is connected to the FBC pin. The compensation network is also connected to this pin to
LED Driver (NCP4328B only)
provide frequency compensation for the voltage regulation LED driver is active when VCC is higher than VCCMIN. path. This FBC pin drives regulation optocoupler that LED driver consists of an internal power switch controlled provides regulation of primary side. The optocoupler is by a PWM modulated logic signal and an external current supplied via direct connection to VOUT line through limiting resistor R9. LED current can be computed by resistor R2. Equation 3 Regulation information is transferred through the V * V OUT F_LED optocoupler to the primary side controller where its FB pin I + (eq. 3) LED R9 is usually pulled down to reduce energy transferred to secondary output. PWM modulation is used to increase efficiency of LED. The output voltage can be computed by Equation 1.
www.onsemi.com 7
NCP4328 TYPICAL CHARACTERISTICS
1.40 100 1.30 90 80 1.20 ) W 70 (kHz) ( 1.10 SW2 60 R f SWLED 1.00 50 0.90 40 0.80 30 −40 −20 0 20 40 60 80 100 120 −40 −20 0 20 40 60 80 100 120 TJ (°C) TJ (°C)
Figure 13. LED Switching Frequency at Figure 14. RSW at VCC = 15 V VCC = 15 V APPLICATION INFORMATION
Typical application circuit for NCP4328A is shown in R3 ) R4 V + V (eq. 1) Figures 15 and 16 shows typical application circuit for OUT REF R4 NCP4328B that includes internal LED driver for indication purpose.
Current Regulation
The output current is sensed by the shunt resistor R5 in
Power Supply
series with the load. Voltage drop on R5 is compared with The NCP4328 is designed to operate from a single supply internal precise voltage reference VREFC at ISNS up to 36 V. It starts to operate when VCC voltage reaches transconductance amplifier input. 3.5 V and stops when VCC voltage drops below 2.5 V. VCC Voltage difference is amplified by gmC to output current can be supplied by direct connection to the VOUT voltage of amplifier, connected to FBC pin. Compensation network of the power supply. It is highly recommended to add a RC is connected between this pin and ISNS input to provide filter (R1 and C2) in series from VOUT to VCC pin to reduce frequency compensation for current regulation path. voltage spikes and drops that are produced at the converter’s Resistor R6 separates compensation network from sense output capacitors. Recommended values for this filter are resistor. Compensation network works into low impedance 220 W and 1 mF. without this resistor that significantly decreases compensation network impact.
Voltage Regulation Path
Current regulation point is set to current given by The output voltage is detected on the VSNS pin by the R3 Equation 2. and R4 voltage divider. This voltage is compared with the internal precise voltage reference. The voltage difference is VREFC I + (eq. 2) amplified by gm OUTLIM V of the transconductance amplifier. The R5 amplifier output current is connected to the FBC pin. The compensation network is also connected to this pin to
LED Driver (NCP4328B only)
provide frequency compensation for the voltage regulation LED driver is active when VCC is higher than VCCMIN. path. This FBC pin drives regulation optocoupler that LED driver consists of an internal power switch controlled provides regulation of primary side. The optocoupler is by a PWM modulated logic signal and an external current supplied via direct connection to VOUT line through limiting resistor R9. LED current can be computed by resistor R2. Equation 3 Regulation information is transferred through the V * V OUT F_LED optocoupler to the primary side controller where its FB pin I + (eq. 3) LED R9 is usually pulled down to reduce energy transferred to secondary output. PWM modulation is used to increase efficiency of LED. The output voltage can be computed by Equation 1.
www.onsemi.com 7