HA16107P Datasheet, PDF (35/40 Pages) Hitachi Semiconductor – PWM Switching Regulator for High-performance Voltage Mode Control

HA16107P/FP, HA16108P/FP
In Figure 5, the parameters are given by the following equations.
Gain
G1 = V3/V2 × R3/R1
G2 = V3/V2 × R4/R1
Corner frequencies
f1 = 1/(2π C1 R3)
f2 = 1/(2π C1 R4)
Where R3>>R4 (10:1 or above)
G₁ is made around 30 to 50 dB, taking both regulation and stability into consideration.
f₁ is made a lower value than commercial frequency ripple f_AC, thus preventing hunting (a system instability
phenomenon).
Next, G₂ is set to 0 dB or less as a guideline, so that there is no gain in IC operating frequency f_OSC (several tens to
several hundreds of kHz). f₂ should be set to a value that is substantially smaller than f_OSC, and that is appropriate for
the power supply response speed (several kHz). In the case of a bridge type rectification circuit, the commercial
frequency ripple is twice the input frequency (with a 50 Hz commercial frequency, f_AC = 100 Hz).
2. External Constant Design for Current Detection Section (HA16107, HA16108, HA16666)
In the above IC models, which incorporate a current detection function, a low-pass filter such as shown in Figure 6 must
be inserted between switch element current detection resistance R_CS and the current detection pin of the IC.
Input voltage V_B ^140V
Floating capacitance
C_X
Output
From PWM
output pin
of IC
To current
detection pin
of IC
V₁₂
C_A
R_A
R_B
Switch element
power MOS FET
I_D
V₁₁
Current detection resistance
R_CS
Several hundred mΩ
to several Ω
Filter (LPF)
Figure 6 Current Detection Circuit
Rev.4.00 Jun 15, 2005 page 35 of 39