MC33025DWR2G データシートの表示（PDF） - ON Semiconductor

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MC33025DWR2G

High Speed Double−Ended PWM Controller

ON Semiconductor 

MC34025, MC33025

4

5

6

CT

C1

Current Sense

R1 7

Information

R2

3

Oscillator

1.25 V

This method of slope compensation is easy to implement, however, it is noise sensitive. Capacitor C1 provides AC coupling. The oscillator

signal is added to the current signal by a voltage divider consisting of resistors R1 and R2.

Figure 29A. Slope Compensation (Noise Sensitive)

Output

Current Sense

Transformer

Figure 29. Keeps Fig numbering sequence correct Output

Rw

Rf

RM

Cf

CM

Ramp

Input

7

1.25 V

3

Current Sense

Resistor

RM

CM

Rf

Cf

Ramp

Input

7

3

1.25 V

When only one output is used, this method of slope compensation can be used and it is relatively noise immune. Resistor RM and

capacitor CM provide the added slope necessary. By choosing RM and CM with a larger time constant than the switching frequency, you

can assume that its charge is linear. First choose CM, then RM can be adjusted to achieve the required slope. The diode provides a reset

pulse at the ramp input at the end of every cycle. The charge current IM can be calculated by IM = CMSe. Then RM can be calculated by

RM = VCC/IM.

Figure 29B. Slope Compensation (Noise Immune)

Oscillator

4

4

5

Vref 5

6

6

CT

RT

Oscillator

Figure 30. Current Mode Master/Slave Operation Over Short Distances

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