SSC9522S datasheet(9/21 Pages) SANKEN

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SSC9522S

SSC9522S - DSE Rev.1.3

SANKEN ELECTRIC CO.,LTD.

Jan.07, 2016

http://www.sanken-ele.co.jp/en

Operational Description

All of the parameter values used in these descriptions

are typical values, unless they are specified as minimum

or maximum. With regard to current direction, "+"

indicates sink current (toward the IC) and "–" indicates

source current (from the IC).

Q(H) and Q(L) indicate a high-side power MOSFET and

a low-side power MOSFET respectively. Ci, and CV

indicate a current resonant capacitor and a voltage

resonant capacitor respectively.

8.1

Resonant Circuit Operation

Figure 8-1 shows a basic RLC series resonant circuit.

Figure 8-1 RLC series resonant circuit

The impedance of the circuit, Ż, is as the following

Equation.

(1)

where, ω is angular frequency and ω = 2πf.

(2)

When the frequency, f, changes, the impedance of

resonant circuit will change as shown in Figure 8-2

Frequency

Inductance area

Capacitance area

Figure 8-2 Impedance of resonant circuit

In Equation (2), Ż becomes minimum value (= R) at

2πfL = 1/2πfC, and then ω is calculated by Equation

(3) .

(3)

The frequency in which Ż becomes minimum value is

the resonant frequency, f0. The higher frequency area

than f0 is the inductance area, and the lower frequency

area than f0 is the capacitance area.

From Equation (3), f0 is as follows;

(4)

Figure 8-3 shows the circuit of a current resonant

power supply. The basic configuration of the current

resonant power supply is a half-bridge converter. The

switching device Q(H) and Q(L) are connected in series

with VIN. The series resonant circuit and the voltage

resonant capacitor CV are connected in parallel with Q(L).

The series resonant circuit is comprised of a resonant

inductor LR, a primary winding P of a transformer T1

and a current resonant capacitor Ci.

In the resonant transformer T1, the coupling between

primary winding and secondary winding is designed to

be poor so that the leakage inductance increases. By

using it as LR, the series resonant circuit can be down

sized. The dotted mark in T1 shows the winding polarity,

the secondary windings S1 and S2 are connected so that

the polarities are set to the same position shown in

Figure 8-3, and the winding numbers of each other are

equal.

From Equation (1), the impedance of current resonant

power supply is calculated by Equation (5). From

Equation (4), the resonant frequency, f0, is calculated by

Equation (6).

(5)

(6)

where,

R: the equivalent resistance of load

LR: the inductance of the resonant inductor

LP: the inductance of the primary winding P

Ci: the capacitance of current resonant capacitor

Q(H)

Series resonant circuit

VOUT

(+)

(−)

VIN

VGH

VGL

Q(L)

VDS(L)

VDS(H)

VCi

ID(H)

ID(L)

ICi

IS2

IS1

Figure 8-3 Current resonant power supply circuit

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