AN1818/1004

Revision 1

1/6

1

Introduction

This paper describes how to reduce the power consumption, under no-load conditions, of battery

chargers and adapters by using STMicroelectronics’s TSM family of secondary-side devices. This family

of devices provides accurate voltage and current regulation, while incurring very low consumption at no-

load conditions. In fact, owing to these innovative, integrated devices, the total power consumption for the

entire system at no-load conditions can be reduced down to nearly 100mW. With the arrival of new power

consumption regulations, this capability is increasingly sought after.

The most innovative of ST’s devices are the TSM101x family. These are highly integrated solutions for

SMPS applications requiring CV and CC mode, integrating one voltage reference and two operational

amplifiers. The voltage reference combined with one operational amplifier makes them ideal voltage

controllers. The other operational amplifier, combined with the integrated voltage reference and a few

external resistors, can be used as a current limiter.

These products family are designed for use in battery chargers with a constant voltage and a limited

output current and in adapters.They can be used in every type of application requiring 0.5% and 1%

voltage reference precision.

2

Power dissipation under no-load conditions

In a typical system for battery charger and adapter applications, different factors contribute to the total

power dissipation under no-load conditions. However, in broad terms, the total power dissipation can be

Secondary-side power dissipation

This article deals with reducing the secondary-side power dissipation, so let us begin by considering a

typical schematic of the secondary-side of an SMPS application, shown in Figure 1.

Figure1: Typical application using CC-CV Standard in SMPS

Rsense

C2

R2

R1

C1

C3

optocoupler

secondary side

Cic1

Cvc1

Ric1

Rvc1

Rlimit

R4

R5

R3

D1

D2

OUT+

OUT-

Ric2

PWM

controller

optocoupler

primary side

Rref

CC-CV Standard

Vref

OP1

OP2

AN1818

Reducing the Total No-Load Power Consumption of

Battery Chargers and Adapter Applications