LB1991V
Overlap Generation and Calculation Method
Absolute voltage
Calculated center point
Electrical
angle
High side residual
voltage
High side clamp potential
Low side clamp
potential
Low side residual
voltage
Time
[Overlap Generation]
Since the voltage generated in the amplitude control block is, taking the center point as the reference, 2 × <overlap> ×
(1/2 VS – VX) on one side, the intersection point of the waveform will be <overlap> × (1/2 VS – VX) from the center
point.
To clamp that waveform at (1/2 VS – VX) referenced to the center point the overlap must be:
A/B × 100 = <overlap> × 100 (%).
[Overlap Calculation]
• High side overlap
Calculated center point: VN =
—(V—S —– V—X—H –—V—XL—)
2
+ VXL =
—(V—S –—V—X—H +—V—XL—)
2
Since A = Vα – VN, B = VS – VXH – VN, the high side overlap will be:
<overlap> =
A
—
=
——V—α –—(—(V—S –—V—XH—+—V—XL—)/2—) —
× 100 (%)
B VS – VXH – ((VS – VXH + VXL)/2)
Which can be calculated as:
= —2V—α—–—(V—S –—V—XH—) —– V—X—L × 100 (%).
(VS – VXH) – VXL
• Low side overlap
Since C = VN – Vβ, and D = VN – VXL, the low side overlap will be:
C
<overlap> = —
=
——((—VS—–—V—XH—+—VX—L—)/2—) — × 100
D ((VS – VXH + VXL)/2) – VXL
Which can be calculated as:
= —(V—S—– V—X—H)—–—VX—L—–2—Vβ— × 100 (%).
(VS – VXH) – VXL
No. 5792-6/7