HCPL-0302-000E Datasheet, PDF (12/15 Pages) AVAGO TECHNOLOGIES LIMITED – 0.4 Amp Output Current IGBT Gate Drive Optocoupler

Selecting the Gate Resistor (Rg) for HCPL-3020
Step 1: Calculate Rg minimum from the IOL peak specification. The IGBT and Rg in Figure 17 can be analyzed as a
simple RC circuit with a voltage supplied by the HCPL-3020.
Rg
≤

VCC – VOL
IOLPEAK


=
24 - 1
0.4

=
57.5 Ω
The VOL value of 1 V in the previous equation is the VOL at the peak current of 0.4 A. (See Figure 4).
Step 2: Check the HCPL-3020 power dissipation and increase Rg if necessary. The HCPL-3020 total power dissipation
(PT) is equal to the sum of the emitter power (PE) and the output power (PO).
PT = PE + PO
PE = IF • VF • Duty Cycle
PO = PO(BIAS) + PO(SWITCHING) = ICC • VCC + ESW (Rg;Qg) • f
= (ICCBIAS + KICC • Qg • f ) • VCC + ESW (Rg;Qg) • f
where KICC • Qg • f is the increase in ICC due to switching and KICC is a constant of 0.001 mA/(nC*kHz). For the circuit
in Figure 17 with IF (worst case) = 10 mA, Rg = 57.5 Ω, Max Duty Cycle = 80%, Qg = 100 nC, f = 20 kHz and TAMAX =
85°C:
PE = 10 mA • 1.8 V • 0.8 = 14 mW
PO = [3 mA + (0.001 mA/nC • kHz) • 20 kHz • 100 nC] • 24 V + 0.3mJ • 20 kHz
= 126 mW < 250 mW (PO(MAX)) @ 85°C
The value of 3 mA for ICC in the previous equation is the max. ICC over entire operating temperature range.
Since PO for this case is less than PO(MAX), Rg = 57.5 Ω is alright for the power dissipation.
4.0
Qg = 50 nC
3.5
Qg = 100 nC
3.0
Qg = 200 nC
Qg = 400 nC
2.5
2.0
1.5
1.0
0.5
0
0
20
40
60 80 100
Rg – GATE RESISTANCE – Ω
Figure 18. Energy dissipated in the HCPL-3020 and HCPL-0302
and for each IGBT switching cycle.
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