CR6203 데이터 시트보기 (PDF) - Unspecified

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CR6203

Switching Power Supply Controller ICs

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CR6203

switching frequency will fall until the oscillator is turned off.

As shown in the following figure,

4. Driving characteristic and high voltage endurance bias technology of power transistor

The power transistor adopts the ramp current drive, the driving current will increase with the output power,

when FB is 0, the current of OB is about 40mA, when FB is 6V, the current of OB is about 120 mA, and the

driving power consumption will decrease remarkably when the output is low.

The interior of IC integrates the particular bias technology, when the power transistor is shut, the output of

OB will be pulled down to the ground, meanwhile, it will bias the output of OE to 1.5V or so, bias the emitter

junction, accelerate the decreasing speed of Ic current, expand the effective safe working area, the switching

transistor affords the reverse voltage CB, therefore, the endurance characteristic of the switching transistor can

be up to 700V. For more detail information for the voltage endurance characteristic of the switching transistor,

please refer to the relevant technical data. The bias waveform is shown as follows:

5. Over-voltage and under-voltage protection

IC has the function of slow-moving under-voltage protection, when the voltage of VCC reaches 8.8V, IC

will set out to start, the initial start-up voltage is provided by the driving resistance, the high voltage of input

will be injected into the base of the switching transistor through Ic current, consequently, the driving voltage is

formed. When IC works normally, the voltage of VCC should be keep between 4.8V and 9V (including the

situation of full load output), if the voltage of VCC falls to 4.4V, the oscillator will enter the state of shutoff,

when it decreases to 3.8V further, IC will begin to reset. As shown in the following figure:

Aug.2008 V2.0

9/14

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