TSM1014

Principles of Operation and Application Tips

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Therefore, for most adapter and battery charger applications, a quarter-watt, or half-watt resistor to make

the current sensing function is sufficient.

The current sinking outputs of the two trans-conductance operational amplifiers are common (to the

output of the IC). This makes an ORing function which ensures that whenever the current or the voltage

reaches too high values, the optocoupler is activated.

The relation between the controlled current and the controlled output voltage can be described with a

square characteristic as shown in the following V/I output-power graph.

5.3 Compensation

The voltage-control trans-conductance operational amplifier can be fully compensated. Both its output

and negative input are directly accessible for external compensation components.

An example of a suitable voltage-control compensation network is shown in Figure 2 on page 4. It

consists of a capacitor Cvc1=2.2nF and a resistor Rcv1=22K

Ω in series.

The current-control trans-conductance operational amplifier can be fully compensated. Both of its output

and negative input are directly accessible for external compensation components.

An example of a suitable current-control compensation network is also shown in Figure 2 on page 4. It

consists of a capacitor Cic1=2.2nF and a resistor Ric1=22K

Ω in series.

5.4 Start-up and short circuit conditions

Under start-up or short-circuit conditions the TSM1014 is not provided with a high enough supply voltage.

This is due to the fact that the chip has its power supply line in common with the power supply line of the

system.

Therefore, the current limitation can only be ensured by the primary PWM module, which should be

chosen accordingly.

If the primary current limitation is considered not to be precise enough for the application, then a sufficient

supply for the TSM1014 has to be ensured under all conditions. For this, it would be necessary to add

some circuitry to supply the chip with a separate power line. This can be achieved in a number of ways,

including putting an additional winding on the transformer.

Figure 3: Output Voltage versus Output Current

Vout

Iout

Voltage regulation

TSM1014 Vcc : independent power supply

0

Secondary current regulation

TSM1014 Vcc : On power output

Primary current regulation