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TEA1610T

Zero-voltage-switching resonant converter controller

Philips Electronics 

Philips Semiconductors

Zero-voltage-switching

resonant converter controller

Product specification

TEA1610P; TEA1610T

Dead time resistor Rdt (see Fig.10)

The dead time resistor Rdt is connected between the 3 V

reference pin (VREF) and the IFS current input pin. The

voltage on the IFS pin is kept constant at a temperature

independant value of 0.6 V. The current that flows into the

IFS pin is determined by the value of resistor Rdt and the

2.4 V voltage drop across this resistor. The IFS input

current equals the discharge current of capacitor Cf and

determines the falling slope of the oscillator.

The falling slope time is used to create a dead time (tdt)

between two successive switching actions of the

half-bridge switches:

IIFS = 2---R-.--4--d---Vt--

tdt = C-----f---×I--I--F-∆--S--V----C---f

tIFS = tdt

Minimum frequency resistor (see Fig.10)

The Rf(min) resistor is connected between the VREF pin (3 V

reference voltage) and the IRS current input (held at a

temperature independant voltage level of 0.6 V). The

charge current of the capacitor Cf is twice the current

flowing into the IRS pin.

The Rf(min) resistor has a voltage drop of 2.4 V and its

resistance defines the minimum charge current (rising

slope) of the Cf capacitor if the control current is zero. The

minimum frequency is defined by this minimum charge

current (IIRS1) and the discharge current:

IIRS1 = -R-2---f-.-(4--m---V-i-n---)

tIRS1 = -C-2---f--×-×----I-∆-I-R--V-S---C-1--f

fmin = -t-d---t---+---1--t--I-R---S---1-

Maximum frequency resistor

The output voltage is regulated by changing the frequency

of the half-bridge converter. The maximum frequency is

determined by the R∆f resistor which is connected between

the error amplifier output VCO and the oscillator current

input pin IRS. The current that flows through the R∆f

resistor (IIRS2) is added to the current flowing through the

Rf(min) resistor. As a result, the charge current ICF

increases and the oscillation frequency increases. As the

falling slope of the oscillator is constant, the relationship

between the output frequency and the charge current is

not a linear function (see Figs 7 and 9):

IIRS2 = V-----V---C--R--O---∆--–--f--0----.-6--

tIRS2 = -I-I--CR----S-f--1×----+-∆----IV--I-R--C--S-f--2- × 2

The maximum output voltage of the error amplifier and the

value of R∆f determine the maximum frequency:

IIRS2(max) = V-----V---C----O----(-Rm-----a∆--x-f--)---–----0----.--6-

tIRS(min) = I--I--R----S--C-1---f-+--×---I--I∆-R---V-S---C2---(-fm----a---x--) × 2

fmax = T----1o---s--c-

Tosc = tIRS(min) + tIFS

Bridge frequency accuracy is optimum in the low

frequency region. At higher frequencies both the dead time

and the oscillator frequency show a decay.

The frequency of the oscillator depends on the value of

capacitor Cf, the peak-to-peak voltage swing VCf and the

charge and discharge currents. However, at higher

frequencies the accuracy decreases due to delays in the

circuit.

handbook, halffpoasgce

f osc(max)

f osc(start)

MGW001

f osc(min)

0

I IRS

Fig.7 Frequency range.

2001 Apr 25

7

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