AND8019 Datasheet, PDF (3/12 Pages) ON Semiconductor – Offline Converter Provides 5.0 Volt, 1.0 Amp Output for Small Electronic Equipment

AND8019/D
Regulation
To measure line regulation, hold the load constant and
vary the input over the desired range taking measurements
at convenient intervals. The change in output voltage for a
fixed load, across the range of input voltages is the line
regulation.
Load regulation is measured in a similar manner. The line
is held constant and the output voltage is measured as the
load is varied from minimum to maximum.
Ripple
The scope should be connected as described in the
Measurement Techniques section, and should be ac coupled.
Peak–to–peak ripple is the measurement from the lowest
point to the highest point on the trace. If a peak–to–mean
measurement is desired, set the scope input to ground, move
the trace on top of the center graticule line of the scope, and
then set the scope coupling back to ac. The voltage from the
lowest point on the trace and the highest point on the trace,
to the center graticule line are the peak–to–mean
measurements.
Efficiency
Efficiency is defined as:
h = Pout/Pin = (V_o I_o) / Pin
The output power is the output voltage multiplied by the
output current. The input power must be read from a quality
wattmeter with a wide bandwidth due to the harmonic
content of the input current waveform. There is no accurate
method of measuring the input power by the use of DVM’s
or oscilloscopes.
Most wattmeters will also measure power factor, line
voltage and line current.
Transient Loads
Rapid changes in the load of a power converter cause the
output voltage to increase or decrease for a short period of
time. If the circuit that will be attached to this converter is
sensitive to small excursions in voltage, it is highly
recommended to test the unit under similar transients. The
following exercise will test the unit for a transient from
250 mA to 1.0 A and from 1.0 A to 250 mA. If the actual load
transient is different, the loads should be modified to reflect
those conditions.
Response to load transients can be observed by causing a
step load change and synching the oscilloscope to this event.
The best way to do this is to replace the switch on the 500 mA
load (10 W resistor) with a FET. An ON Semiconductor
MTD3302 transistor, driven by a pulse generator with a
0 volt to 10 volt pulse will make a simple electronic switch.
Figures 8 and 9 show the transient response to an output load
change of 10% to 100% load.
Observing the output voltage on an oscilloscope during
this event will allow measurement of the level of
perturbation as well as the duration.
Converter Test Data
Parameter
Conditions
Line Regulation
Load Regulation
Combined Line/
Load Regulation
85 V ≤ V_in ≤ 265 V
0 A ≤ I_o ≤ 1.0 A
85 V ≤ V_in ≤ 265 V
0 A ≤ I_o ≤ 1.0 A
Output Ripple
Input Power
Power Factor
Efficiency
I_o = 1.0 A
V_in = 115 V, I_o = 1.0 A
V_in = 220 V, I_o = 1.0 A
V_in = 115 V, I_o = 1.0 A
V_in = 220 V, I_o = 1.0 A
V_in = 115 V, I_o = 1.0 A
V_in = 220 V, I_o = 1.0 A
Data
DV_o = 6.0 mV
DV_o = 8.0 mV
DV_o = 10 mV
100 mV_pp
7.75 watts
7.88 watts
–0.57
–0.49
h = 66%
h = 64%
Troubleshooting
Symptom
Solution
Unit does not
turn on, does not
draw current
1. Assure that ac source and meter are
properly connected by measuring the
voltage at the input connector.
2. Measure the voltage across C2. If it is
not approximately equal to the peak input
voltage, check for wrong or defective
components (R6, R7, D1–D4).
3. Observe voltage at pin 1 of U1. This
voltage needs to exceed 8.5 volts for
unit to start, and remain greater than
7.5 volts for unit to operate. If not in this
range check for shorts, and assure that
pin 5 is greater than 50 volts, otherwise
replace chip.
4. Measure the voltage at pin 2 of U1.
It should measure less than 4.5 volts for
PWM to be active. If it is, and the output
is not switching, the NCP1000 may be
defective.
Unit does not
turn on, draws
excessive current
1. Check for obvious shorts on the board
and remove if found.
2. Disconnect all leads and measure
resistance across C2. If no short is found,
check test setup. If a short is found,
isolate it by removing components and
testing (D1–D4, C2, U1).
• Unit does
not regulate
1. Assure that the input voltage and output
current are in the specified ranges.
2. Measure voltage across C8. It should be
at least twice the output voltage. If not,
check D6, L2 and C8.
3. Check the voltage at pin 2. If it is greater
than 4.5 volts the opto may be shorted,
if 0 the opto may open or C4 may be
shorted.
4. Measure voltage at pin 8 of U3 and
measure voltage drop across R3. If:
• V₈ < 2.5 volts & V_R3 = 0 then replace U2.
• V₈ < 2.5 volts & V_R3 > 0 then replace U3.
• V₈ > 2.5 volts & V_R3 = 0 then replace U3.
• V₈ > 2.5 volts & V_R3 > 0 then replace U2.
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