NCP1616 データシートの表示（PDF） - ON Semiconductor

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NCP1616

High Voltage High Efficiency Power Factor Correction Controller

ON Semiconductor 

NCP1616

DETAILED OPERATING DESCRIPTION

INTRODUCTION

The NCP1616 is designed to optimize the efficiency of your

PFC stage throughout the load range. In addition, it

incorporates protection features for rugged operation. More

generally, the NCP1616 is ideal in systems where cost

effectiveness, reliability, low standby power and high

efficiency are the key requirements:

• Current Controlled Frequency Foldback: the NCP1616

operates in Current Controlled Frequency Foldback

(CCFF). In this mode, the circuit operates in classical

Critical conduction Mode (CrM) when the inductor

current exceeds a programmable value. When the

current falls below this preset level, the NCP1616

linearly reduces the operating frequency down to a

minimum of about 26 kHz when the input current

reaches zero. CCFF maximizes the efficiency at both

nominal and light load. In particular, standby losses are

reduced to a minimum. Similar to frequency clamped

CrM controllers, internal circuitry allows near−unity

power factor at lower output power.

• Skip Mode: to further optimize the efficiency, the

circuit skips cycles near the line zero crossing when the

current is very low. This is to avoid circuit operation

when the power transfer is particularly inefficient at the

cost of input current distortion. When superior power

factor is required, this function can be inhibited by

offsetting the FFcontrol pin by 0.75 V.

• Integrated High Voltage Start−Up Circuit: Eliminates

the need of external start−up components. It is also used

to discharge the input filter capacitors when the line is

removed.

• Integrated X2 Capacitor Discharge: reduces input

power by eliminating external resistors for discharging

the input filter capacitor.

• Fast Line / Load Transient Compensation (Dynamic

Response Enhancer): since PFC stages exhibit low loop

bandwidth, abrupt changes in the load or input voltage

(e.g. at start−up) may cause an excessive over or

undervoltage condition. This circuit limits possible

deviations from the regulation level as follows:

♦ The soft and fast Overvoltage Protections accurately

limit the PFC stage maximum output voltage.

♦ The NCP1616 dramatically speeds up the regulation

loop when the output voltage falls below 95.5% of

its regulation level. This function is disabled during

power up to achieve a soft−start.

• Standby Mode Input: allows the downstream converter

to inhibit the PFC drive pulses when the load is reduced.

• Safety Protections: the NCP1616 permanently monitors

the input and output voltages, the MOSFET current and

the die temperature to protect the system during fault

conditions making the PFC stage extremely robust and

reliable. In addition to the bulk overvoltage protection,

the NCP1616 include:

♦ Maximum Current Limit: the circuit senses the

MOSFET current and turns off the power switch if

the maximum current limit is exceeded. In addition,

the circuit enters a low duty−ratio operation mode

when the current reaches 150% of the current limit

as a result of inductor saturation or a short of the

bypass/boost diode.

♦ Undervoltage Protection (UVP): this circuit turns off

when it detects that the output voltage is below 12%

of the voltage reference (typically). This feature

protects the PFC stage if the ac line is too low or if

there is a failure in the feedback network (e.g., bad

connection).

♦ Bulk Undervoltage Detection (BUV): the circuit

monitors the output voltage to detect when the PFC

stage cannot regulate the bulk voltage (BUV fault).

When the BUV fault is detected, the control pin is

gradually discharged.

♦ Brownout Detection: the circuit detects low ac line

conditions and stops operation thus protecting the

PFC stage from excessive stress.

♦ Thermal Shutdown: an internal thermal circuitry

disables the gate drive when the junction

temperature exceeds the thermal shutdown

threshold.

♦ A line overvoltage circuit monitors the bulk voltage

and disables the controller if voltage exceeds the

overvoltage level.

• Output Stage Totem Pole Driver: the NCP1616

incorporates a 0.5 A source / 0.8 A sink gate driver to

efficiently drive most medium to high power

MOSFETs.

HIGH VOLTAGE START−UP CIRCUIT

NCP1616 has an integrated high voltage start−up circuit

accessible by the HV pin. The start−up circuit is rated at a

maximum voltage of 700 V.

A start−up regulator consists of a constant current source

that supplies current from a high voltage rail to the supply

capacitor on the VCC pin (CVCC). The start−up circuit

current (Istart2) is typically 12 mA. Istart2 is disabled if the

VCC pin is below VCC(inhibit). In this condition the start−up

current is reduced to Istart1, typically 0.5 mA. The internal

high voltage start−up circuit eliminates the need for external

start−up components. In addition, this regulator reduces no

load power and increase the system efficiency as it uses

negligible power in the normal operation mode

Once CVCC is charged to the start−up threshold, VCC(on),

typically 17 V, the start−up regulator is disabled and the

controller is enabled. The start−up regulator remains

disabled until VCC falls below the lower supply threshold,

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