TSM1051

Application information

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Figure 10. Output voltage versus output current

5.2

Compensation

The voltage-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 compensation network is shown in Figure 3. It consists of a

capacitor Cvc1 = 2.2 nF and a resistor Rcv1 = 470 k

Ω in series.

The current-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 compensation network is shown in Figure 3. It consists of a

capacitor Cic1 = 2.2 nF and a resistor Ric1 = 22 k

Ω in series. In order to reduce the

the stability of the application it is suggested to limit the current flowing in the OUT pin of the

device adding a resistor in series with the opto-coupler.

5.3

Start up and short circuit conditions

Under start-up or short-circuit conditions the device 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 device has to be ensured under any condition. It would then

be necessary to add some circuitry to supply the chip with a separate power line. This can

be achieved in numerous ways, including an additional winding on the transformer.

The following schematic shows how to realize a low-cost power supply for the device (with

no additional windings).

Vout

Iout

Voltage regulation

(Vcc of the device independent from output voltage)