HIP4080A/81AEVALZ Просмотр технического описания (PDF) - Intersil
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HIP4080A/81AEVALZ Datasheet PDF : 14 Pages
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Application Note 9404
Power Dissipation, the Easy Way
The average power dissipation associated with the IC and
the gate of the connected MOSFETs can easily be
measured using a signal generator, an averaging millimeter
and a voltmeter.
Low Voltage Power Dissipation
Two sets of measurements are required. The first set uses
the circuit of Figure 8 and evaluates all of the low voltage
power dissipation components. These components include
the MOSFET gate charge and internal CMOS charge
transfer losses shown in Equation 5 as well as the quiescent
bias current losses associated with the IC. The losses are
calculated very simply by calculating the product of the bias
voltage and current measurements as performed using the
circuit shown in Figure 8. For measurement purposes, the
phase terminals (AHS and BHS) for both A and B phases
are both tied to the chip common, VSS terminal, along with
the lower source terminals, ALS and BLS. Capacitors equal
to the equivalent gate-source capacitance of the MOSFETs
are connected from each gate terminal to VSS. The value of
the capacitance chosen comes from the MOSFET
manufacturers data sheet. Notice that the MOSFET data
sheet usually gives the value in units of charge (usually
nano-coulombs) for different drain-source voltages. Choose
the drain-source voltage closest to the particular DC bus
voltage of interest.
Simply substituting the actual MOSFETs for the capacitors,
CL, doesn’t yield the correct average current because the
Miller capacitance will not be accounted for. This is because
the drains don’t switch using the test circuit shown in
Figure 8. Also the gate capacitance of the devices you are
using may not represent the maximum values which only the
data sheet will provide.
The low voltage charge transfer switching currents are
shown in Figure 9. Figure 9 does not include the quiescent
bias current component, which is the bias current which
flows in the IC when switching is disabled. The quiescent
bias current component is approximately 10mA. Therefore
the quiescent power loss at 12V would be 120mW. Note that
the bias current at a given switching frequency grows almost
proportionally to the load capacitance, and the current is
directly proportional to switching frequency, as previously
suggested by Equation 5.
IBIAS
A
BHB
1
20 BHO
CL
+
12V
20K
HEN 2
DIS 3
19 BHS
18 BLO
CL
VSS 4
17 BLS
OUT
5
HIP4080A
16 VDD
20K
IN+ 6
15 VCC
IN- 7
HDEL 8
ALS
14
CL
ALO
13
100K
LDEL 9
AHB 10
100K
12 AHS
CL
11 AHO
CL = GATE LOAD CAPACITANCE
FIGURE 8. LOW VOLTAGE POWER DISSIPATION TEST
CIRCUIT
500
200
100
10,000
50
3,000
20
1,000
10
100
5
2
1
0.5
0.2
0.1
12
5 10 20 50 100 200
SWITCHING FREQUENCY (kHz)
500 1000
FIGURE 9. LOW VOLTAGE BIAS CURRENT IDD AND ICC
(LESS QUIESCENT COMPONENT) vs
FREQUENCY AND GATE LOAD
CAPACITANCE
High Voltage Power Dissipation
The high voltage power dissipation component is largely
comprised of the high voltage level-shifter component as
described by Equation 6. All of the difficulties associated with
the time variance of the ION and IOFF pulses and the level
shift voltage, VSHIFT, under the integrand in Equation 6 are
avoided. For completeness, the total loss must include a
small leakage current component, although the latter is
usually smaller compared to the level-shifter component.
The high voltage power loss calculation is the product of the
high voltage bus voltage level, VBUS, and the average high
voltage bus current, IBUS, as measured by the circuit shown
in Figure 10. Averaging meters should be used to make the
measurements.
9
AN9404.3
December 11, 2007
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