AP3783R

Document number: DS37448 Rev. 5 - 2

11 of 17

www.diodes.com

October 2015

© Diodes Incorporated

AP3783R

Light-load

High-load

0.5kHz

80kHz

37%

5%

24kHz

65kHz

full load

Figure 4. Multiple Segment Peak Current at CV Mode

It can be seen from Figure 4, with multiple segment peak current control, AP3783R power system can keep switching frequency above 24kHz

at whole heavy load and most of light load to guarantee the audible noise free performance.

Constant Voltage Operation in LL Mode and Dynamic Response

In primary side regulation of AP3783R application, APR3415 must be used at secondary side as the output voltage regulator, low standby power

and excellent dynamic response can be achieved. When the output voltage detected by APR3415 is lower than its trigger voltage, APR3415

outputs periodical signals which will be coupled to auxiliary side. When AP3783R detects the signal which is valid that the signal voltage is higher

By fast response and cooperation, APR3415 and AP3783R can maintain a constant output voltage with very low operating frequency in LL mode

and also can effectively improve dynamic performance for primary side regulation power system.

3-Segment Drive Current for Radiative EMI Suppression

When the power switch is turned on, a turn-on spike will occur, that worsens the radiative EMI. It is an effective way to decrease drive current

before gate voltage gets to miller platform. The AP3783R uses 3-segment drive current for radiative EMI suppression, as shown in Figure 5.

When gate voltage gets to 6V, the AP3783R drive current switches from low current (43mA) to high current (110mA). When the gate voltage

gets to 10V, the drive current will decrease gradually to 0mA until the gate voltage goes up to the clamp voltage (11V).