(7)

Electric Parameter Definitions

 　 Start-up receives current: The current of OC when

there’s a 0.5mA pull down current of OB in the start-up

period.

.

　 Start-up static current:The minimum current

sourcing current which can enable VCC surging when

VCC is connected to a filter capacitor and an adjustable

current sourcing, CT is connected to a 680pF capacitor,

and other pins with no connection.

.

　 Start-up voltage:The maximum of VCC above.

　 Re-start-up voltage:The minimum of VCC above.

　 Oscillator shut-down voltage:The negative-edge of

VCC above; the value of VCC which can stop the

oscillator.

.

　 Static current: The VCC power supply current in

normal period when FB is connected to the ground by

a 1.0KΩ resistance.

.

　 Oscillator pull up/pull down current: The pull up/pull

down current of CT when FB=2.5V and CT=1.25V in

normal period.

.

　 FB pull up current: which occurs in normal period,

when FB=2.5V, and IS=0A .

.

　 FB upper current protection: The pull down current

of FB when FB=6V and IS=0.6A in normal period.

　 Inside feedback power supply: The value of VCC

when there is no feedback circuit of CRE6203 in normal

period.

.

　 OC upper limit current: If FB=6V, the minimum OC

current when there is pull down current in FB.

　 Oscillator cycle: Which is the function of the

capacitor connected to CT, about CT*25400 seconds.

　 Current control switching power supply with

fly-back design, discontinuous current operation mode.

　 The power supply start-up current is 0.5-2mA

which is alternative. The magnification of power

transistor Q1 can be supposed as 10. Then the

alternation of the start-up resistance must assure the

current of the power transistor’s base is between

0.05mA to 0.2mA. Therefore, the power of the output

resistance can reduce to 1/10, which reduces the

power in idle state .

.

　 In diagram 3, C3=680pF, the maximum operation

frequency is about 67KHz .

.

　 The reference winding rectifier output is 4.8~9.0V

(6V is recommended) of the Switching transformer (T1

in diagram 3), which provide operation power for

CRE6203.

.

　 The maximum primary peak current of the

switching transformer is 0.6A. When at wide voltage or

110V Vac , or 85V magnetism dissipation voltage, the

maximum output power can achieve more than 12W.

　 The OC (Pin 7, 8) of CRE6203 is in high voltage,

and IS (Pin 6, for current sense resister) is connected.

Therefore, it is easy to open a divider between pin 6

and 7 to meet the requirement of the safe regulation.

　 Although there is over-temperature protection,

when high-power output is needed without considering

PCB heat dissipation, the output power and voltage

may fall.

.

PWM Controller of High-performance Current Mode

Product Specification

Power Supply Design Points

CRE6203

CRE Semiconductor Inc.