CS1630-FSZ datasheet(15/56 Pages) APEX

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CS1630/31

DS954F2

5.6.1 Maximum Peak Current

The maximum boost inductor peak current is configured by

adjusting the peak switching current with IPK(code). The

PEAK_CUR register (see "Peak Current (PEAK_CUR) –

Address 51" on page 39) is used to store IPK(code). Maximum

power output is proportional to IPK(code), as shown in

Equation 3:

where,

 = correction term = 0.55

VRMS(typ) = nominal operating input RMS voltage

IPK =IPK(code) 4.1mA

5.6.2 Output BSTOUT Sense & Input IAC

Sense

A current proportional to boost output voltage VBST is supplied

to the IC on pin BSTOUT and is used as a feedback control

signal. The ADC is used to measure the magnitude of the

IBSTOUT current through resistor RBST. The magnitude of the

IBSTOUT current is then compared to an internal reference

current (Iref) of 133A.

Figure 12. BSTOUT Input Pin Model

Resistor RBST sets the feedback current at the nominal boost

output voltage. For 230VAC line voltage applications, RBST is

calculated as shown in Equation 4:

where,

VBST = Nominal boost output voltage

Iref = Internal reference current

For 120VAC line voltage applications (CS1630), nominal

boost output voltage VBST is 200V, and resistor RBST is

1.5M

. By using digital loop compensation, the voltage

feedback signal does not require an external compensation

network.

A current proportional to the AC input voltage is supplied to the

IC on pin IAC and is used by the boost control algorithm.

Figure 13. IAC Input Pin Model

Resistor RIAC sets the IAC current and is derived from

Equation 5:

For optimal performance, resistors RIAC and RBST should use

1% tolerance or better resistors for best VBST voltage

accuracy.

5.6.3 Boost Auxiliary Winding

The boost auxiliary winding is used for zero-current detection

(ZCD). The voltage on the auxiliary winding is sensed through

the BSTAUX pin of the IC. It is also used to deliver startup

current during startup time (see "Startup Circuit" on page 12).

5.6.4 Boost Overvoltage Protection

The CS1630/31 supports boost overvoltage protection (BOP)

to protect the bulk capacitor C8 (see Figure 14). If the boost

output voltage exceeds the overvoltage protection thresholds

programmed in the OTP registers a BOP fault signal is

generated. The voltage level, VBOP(th), can be set within 227V

to 257V for a CS1630 and 432V to 462V for a CS1631 (see

"Configuration 53 (Config53) – Address 85" on page 45). The

control logic continuously averages the BOP fault signal using

a leaky integrator. When the output of the leaky integrator

exceeds a certain threshold, which can be set using bits

BOP_INTEG[3:0] in register Config53 (see "Configuration 53

(Config53) – Address 85" on page 45), a boost overvoltage

fault is declared and the system stops boosting. More

information on the leaky integrator size and sample rate is

provided in section 6.23 "Configuration 18 (Config18) –

Address 50" on page 38.

During a boost overvoltage protection event, the second stage

is kept enabled only if the MAX_CUR bit in register Config45

(see "Configuration 45 (Config45) – Address 77" on page 40)

is set to ‘1’ (enabled), and its dim input is railed to full scale.

This allows the second stage to quickly dissipate the stored

energy on the bulk capacitor C8, bringing down the boost

output voltage to a safe value. A visible flash on the LED might

appear, indicating that an overvoltage event has occurred.

When the boost output voltage drops to 195V (for a 120V

application), or 392V (for a 230V application), the boost stage

is enabled if bit BOP_RSTART in register Config54 (see

PIN max



 I

PK VRMS typ







------------------------------------------------

[Eq.3]

VBST

CS1630 /31

15k

ADC

RBST

IBSTOUT

Iref

BSTOUT

RBST

VBST

Iref

--------------

400V

133

A

------------------





[Eq.4]

RIAC

IAC

Vrect

CS1630 /31

15k

ADC

Iref

RIAC

RBST

[Eq.5]

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