HA17431 Series
Shunt Regulators
APPLICATION NOTE
2nd Edition
ADE-504-004A
(
Z
)
Cautions
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Contents
Section 1 Outline.............................................................................................. 1
1.1 Features ......................................................................................................... 1
1.2 Selection Guide ............................................................................................... 2
1.3 Pin Arrangement by Product .............................................................................. 3
Section 2 Specifications ................................................................................... 4
2. 1 Absolute Maximum Ratings.............................................................................. 4
2.2 Electrical Characteristics.................................................................................... 6
Section 3 Characteristics Curves...................................................................... 8
Section 4 Outline Dimensions.......................................................................... 13
Section 5 MPAK-5 and UPAK Marking Patterns............................................ 14
Section 6 Ordering Information........................................................................ 16
Section 7 Application Examples....................................................................... 17
7. 1 Application Hints ............................................................................................ 18
7.2 Design Guide for AC-DC SMPS (Switching Mode Power Supply) ........................... 21
7.2.1 Use of Shunt Regulator in Transformer Secondary Side Control..................... 21
7.2.2 Determination of External Constants for the Shunt Regulator........................ 21
7.2.3 Practical Example ................................................................................. 23
7. 3 Circuit Example AC-DC SMPS ......................................................................... 24
HITACHI 1
Section 1 Outline
The HA17431 series is a family of voltage referenced shunt regulators. The main application of
these products is in voltage regulators that provide a variable output voltage. The HA17431 series
products are provided in a wide range of packages; TO-92 and TO-92MOD insertion mounting
packages and MPAK-5, UPAK, and FP-8D surface mounting packages are available. The on-chip
high-precision reference voltage source can provide ±1% accuracy in the V versions, which have a
VKAmax of 16 volts. The HA17431VLP, which is provided in the MPAK-5 package, is designed
for use in switching mode power supplies. It provides a built-in photocoupler bypass resistor for
the PS pin, and an error amplifier can be easily constructed on the supply side.
1.1 Features
• The V versions provide 2.500 V ±1% at Ta = 25°C
• The HA17431VLP includes a photocoupler bypass resistor (2 kΩ)
• The reference voltage has a low temperature coefficient
• The MPAK-5 and UPAK miniature packages are optimal for use on high mounting density
circuit boards
• A wide operating temperature range (–40 to +85°C) is provided by the TO-92, TO-92MOD,
and FP-8D package versions
A
+
−
REF
K PS *
2 kΩ
2.500 V
Note: The PS pin is only provided by the HA17431VLP.
Figure 1.1 Block Diagram
2 HITACHI
1.2 Selection Guide
HA17431
Item V Version A Version Normal
Version Package Temp. Range
Reference
voltage Accuracy ±1% (at 25°C) ±2.2% ±4%
Max 2.525 V 2.550 V 2.595 V
Typ 2.500 V 2.495 V 2.495 V
Min 2.475 V 2.440 V 2.395 V
Cathode voltage 16 V max 40 V max 40 V max
Cathode current 50 mA max 150 mA max 150 mA max
Wide temperature use HA17431VPJ HA17431PNAJ TO-92 –40 to +85°C
HA17431PAJ TO-92MOD
HA17431PJ TO-92MOD
HA17431FPAJ FP-8D
HA17431FPJ FP-8D
Industrial use HA17431VLP MPAK-5 –20 to +85°C
HA17431VP HA17431PNA TO-92
HA17431UPA UPAK
HA17432UPA UPAK
HA17431PA TO-92MOD
HA17431P TO-92MOD
HA17431FPA FP-8D
HA17431FP FP-8D
Commercial use HA17431UA UPAK
HA17432UA UPAK
HITACHI 3
1.3 Pin Arrangement by Product
Product Name Package Pin Arrangement
HA17431PA TO-92MOD
AKR
HA17431VP (2.5 V series)
HA17431PNA TO-92
AKR
HA17431UA
HA17431UPA UPAK
AKR
HA17432UA
HA17432UPA UPAK
ARK
HA17431VLP (2.5 V series) MPAK-5
AKR
PSNC
HA17431FPA SOP-8 RNC ANC
KNC NC NC
4 HITACHI
Section 2 Specifications
2.1 Absolute Maximum Ratings (Ta = 25°C)
Item Symbol HA17431VLP HA17431VP HA17431VPJ Unit Notes
Cathode voltage VKA 16 16 16 V 1
PS term. voltage VPS VKA to 16 — — V 1, 2, 3
Continuous cathode
current IK–50 to +50 –50 to +50 –50 to +50 mA
Reference input current Iref –0.05 to +10 –0.05 to +10 –0.05 to +10 mA
Power dissipation PT150*4500*5500*5mW 4, 5
Operating temperature
range Topr –20 to +85 –20 to +85 –40 to +85 °C
Storage temperature Tstg –55 to +150 –55 to +150 –55 to +150 °C
Item Symbol HA17431P/PA HA17431FP/FPA HA17431UA/UPA Unit Notes
Cathode voltage VKA 40 40 40 V 1
Continuous cathode
current IK–100 to +150 –100 to +150 –100 to +150 mA
Reference input current Iref –0.05 to +10 –0.05 to +10 –0.05 to +10 mA
Power dissipation PT800*6500*7800*8mW 6, 7, 8
Operating temperature
range Topr –20 to +85 –20 to +85 –20 to +85 °C
Storage temperature Tstg –55 to +150 –55 to +125 –55 to +150 °C
Item Symbol HA17431PJ/PAJ HA17431FPJ/FPAJ Unit Notes
Cathode voltage VKA 40 40 V 1
Continuous cathode
current IK–100 to +150 –100 to +150 mA
Reference input current Iref –0.05 to +10 –0.05 to +10 mA
Power dissipation PT800*6500*7mW 6, 7
Operating temperature
range Topr –40 to +85 –40 to +85 °C
Storage temperature Tstg –55 to +150 –55 to +125 °C
HITACHI 5
Item Symbol HA17432UA/UPA HA17431PNA HA17431PNAJ Unit Notes
Cathode voltage VKA 40 40 40 V 1
Continuous cathode
current IK–100 to +150 –100 to +150 –100 to +150 mA
Reference input current Iref –0.05 to +10 –0.05 to +10 –0.05 to +10 mA
Power dissipation PT800*6500*5500*5mW 5, 6
Operating temperature
range Topr –20 to +85 –20 to +85 –40 to +85 °C
Storage temperature Tstg –55 to +150 –55 to +150 –55 to +150 °C
Notes: 1. Voltages are referenced to anode.
2. The PS pin is only provided by the HA17431VLP.
3. The PS pin voltage must not fall below the cathode voltage. If the PS pin is not used,
the PS pin is recommended to be connected with the cathode.
4. Ta ≤ 25°C. If Ta > 25°C, derate by 1.2 mW/°C.
5. Ta ≤ 25°C. If Ta > 25°C, derate by 4.0 mW/°C.
6. Ta ≤ 25°C. If Ta > 25°C, derate by 6.4 mW/°C.
7. 50 mm × 50 mm × t 1.5 mm glass epoxy board, Ta ≤ 25°C. If Ta > 25°C, derate by
5 mW/°C.
8. 15 mm × 25 mm × t 0.7 mm alumina ceramic board, Ta ≤ 25°C. If Ta > 25°C, derate by
6.4 mW/°C.
6 HITACHI
2.2 Electrical Characteristics
HA17431VLP/VP/VPJ (Ta = 25°C, IK = 10 mA)
Item Symbol Min Typ Max Unit Test Conditions Notes
Reference voltage Vref 2.475 2.500 2.525 V VKA = Vref
Reference voltage
temperature
deviation
Vref(dev) — 10 — mV VKA = Vref
Ta = –20°C to +85°C1
Reference voltage
temperature
coefficient
∆Vref/∆Ta — ±30 — ppm/°CV
KA = Vref
0°C to 50°C gradient
Reference voltage
regulation ∆Vref/∆VKA — 2.0 3.7 mV/V VKA = Vref to 16 V
Reference input
current Iref — 2 6 µA R1 = 10 kΩ, R2 = ∞
Reference current
temperature
deviation
Iref(dev) — 0.5 — µA R1 = 10 kΩ, R2 = ∞
Ta = –20°C to +85°C
Minimum cathode
current Imin — 0.4 1.0 mA VKA = Vref 2
Off state cathode
current Ioff — 0.001 1.0 µAV
KA = 16 V,
Vref = 0 V
Dynamic
impedance ZKA — 0.2 0.5 ΩVKA = Vref
IK = 1 mA to 50 mA
Bypass resistance RPS 1.6 2.0 2.4 kΩIPS = 1 mA 3
Bypass resistance
temperature
coefficient
∆RPS/∆Ta — +2000 — ppm/°CI
PS = 1 mA
0°C to 50°C gradient 3
HITACHI 7
HA17431PJ/PAJ/FPJ/FPAJ/P/PA/UA/UPA/FP/FPA/PNA/PNAJ, HA17432UA/UPA
(Ta = 25°C, IK = 10 mA)
Item Symbol Min Typ Max Unit Test Conditions Notes
Reference voltage Vref 2.440 2.495 2.550 V VKA = Vref A
2.395 2.495 2.595 Normal
Reference voltage
temperature
deviation
Vref(dev) — 11 (30) mV VKA = Vref Ta =
–20°C to
+85°C
1, 4
— 5 (17) Ta = 0°C
to +70°C1, 4
Reference voltage ∆Vref/∆VKA — 1.4 3.7 mV/V VKA = Vref to 10 V
regulation — 1 2.2 VKA = 10 V to 40 V
Reference input
current Iref — 3.8 6 µA R1 = 10 kΩ, R2 = ∞
Reference current
temperature
deviation
Iref(dev) — 0.5 (2.5) µA R1 = 10 kΩ, R2 = ∞
Ta = 0°C to 70°C4
Minimum cathode
current Imin — 0.4 1.0 mA VKA = Vref 2
Off state cathode
current Ioff — 0.001 1.0 µAV
KA = 40 V,
Vref = 0 V
Dynamic
impedance ZKA — 0.2 0.5 ΩVKA = Vref
IK = 1 mA to 100 mA
Notes: 1. Vref(dev) = Vref(max) – Vref(min)
Vref(dev)
Ta Min Ta Max
Vref(max)
Vref(min)
2. Imin is given by the cathode current at Vref = Vref(IK=10mA) – 15 mV.
3. RPS is only provided in HA17431VLP.
4. The maximum value is a design value (not measured).
8 HITACHI
Section 3 Characteristics Curves
HA17431VLP/VP/VPJ
2.575
2.550
2.525
2.475
2.450
2.425
−200 2040608085
Ambient temperature Ta (°C)
Reference voltage Vref (V)
REF
Reference Voltage Temperature Characteristics
1.0
0.5
0012345
Cathode voltage V
K
(V) Cathode voltage V
K
(V)
Cathode current I
K
(mA)
Cathode current I
K
(mA)
Cathode Current vs. Cathode Voltage Characteristics 1 Cathode Current vs. Cathode Voltage Characteristics 2
2.500
V
K
=Vref
I
K
=10mA
V
K
=Vref
K
A
I
K
VVref
50
0
−50
−50 5
V
K
=Vref
HITACHI 9
100
10
0.1
0.01
100 1k 10k 100k 1M
Frequency f (Hz)
Dynamic impedance ZKA (Ω)
REF
Dynamic Impedance vs. Frequency Characteristics
50
0
100 1k 100k 1M 10M
Frequency f (Hz)
Open loop voltage gain GVOL (dB)
Open Loop Voltage Gain, Phase vs. Frequency Characteristics
1K
A
VVK
REF
K
A
IK=10mA
io
io = 2mAP-P
ZKA=io
VK(Ω)
Phase delay ∅ (degrees)
−180
0
−360
10k
∅220Ω
Vo
15kΩ
8.2kΩ
Vi
10µF
−+
G = 20log Vi
Vo (dB)
GVOL
IK
10 HITACHI
HA17431PJ/PAJ/FPJ/FPAJ/P/PA/UA/UPA/FP/FPA
Oscillation Stability vs. Load Capacitance between Anode and Cathode
Cathode current I
K
(mA)
150
100
50
0
0.0001 0.001 0.01 0.1 2.01.0
Load capacitance C
L
(µF)
Stable
region
Oscillation
region
C
L
V
CC
1.5
Open loop voltage gain G
VOL
(dB)
0
10
20
30
40
50
60
Open Loop Voltage Gain, Phase vs. Frequency Characteristics (1)
(With no feedback capacitance)
Frequency f (Hz)
10 100 1 k 10 k 100 k
180
90
0
Phase φ (degrees)
Phase φ (degrees)
8.2 kΩ
15 kΩ
220 Ω
GND
Vout
10 µF
Vin
φ
G
V
I
K
= 10 mA
Open loop voltage gain G
VOL
(dB)
−4
0
5
8
10
Frequency f (Hz)
10 100 1 k 10 k
Open Loop Voltage Gain, Phase vs. Frequency Characteristics (2)
(When a feedback capacitance (Cf) is provided)
360
180
270
50 ΩGND
20 V
Vout
+
−
2 k
2.4 kΩ
7.5 kΩ
Vin
200 µFCf
Cf = 0.22 µF
Cf = 0.022 µF
φ
GυGυ
I
K
= 5 mA
HITACHI 11
Reference voltage pin Input current
Iref (µA)
0.5
1.0
1.5
2.0
2.5
Cathode voltage VK (V)
0152010525403530
IK = 10 mA
Reference Voltage Pin Input Current vs. Cathode Voltage Characteristics
Input/Output voltage VI (V)
1
2
3
4
5
Time t (µs)
0 456231
P.G
f = 100 kHz
Pulse Response
GND
Vout
220 Ω
50 Ω
OUTPUT
(Vout)
INPUT
(P.G)
Reference voltage Vref (V)
2.44
2.45
2.46
2.47
2.48
VKA = Vref
IK = 10 mA
2.49
2.50
Ambient temperature Ta (°C)
−200 2040608085
Reference Voltage Temperature Characteristics
12 HITACHI
Cathode current I
K
(mA)
Cathode voltage V
K
(V)
−10−2 123
−100
−80
−60
−40
−20
0
20
40
60
80
100
120
150
Cathode Current vs. Cathode Voltage Characteristics (1)
V
K
= Vref
Ta = 25°C
Cathode current I
K
(mA)
Cathode voltage V
K
(V)
1230
0.2
0.4
0.6
0.8
1.0
1.2
Cathode Current vs. Cathode Voltage Characteristics (2)
V
KA
= Vref
Ta = 25°C
Imin
Cathode current when off state Ioff (nA)
Ambient temperature Ta (°C)
−200 2040608085
0.5
1
1.5
2
Cathode Current Temperature Characteristics
when Off State
V
KA
= 40 V
Vref = 0
Reference voltage pin input current Iref (µA)
Ambient temperature Ta (°C)
−200 2040608085
0
0.5
1
1.5
2
2.5 R
1
= 10 kΩ
R
2
= ∞
I
K
= 10 mA
3
Reference Voltage Pin Input Current
Temperature Characteristics
HITACHI 13
Section 4 Outline Dimensions
10 mm 10 mm
HA17431VLP
10 mm
4.5 ± 0.1
1.8 Max 1.5 ± 0.1
0.44 Max
0.44 Max
0.48 Max
0.53 Max
1.5 1.5
3.0
2.5 ± 0.1
4.25 Max
0.8 Min
φ1
0.4
(1.5)
(2.5)
(0.4)
(0.2)
0.16
0 − 0.15
(0.95) (0.95)
(0.6)
(0.6)
1.1+ 0.2
− 0.1
HA17431UA/UPA Unit: mm
HA17431FP/FPJ/FPA/FPAJ HA17431VP/VPJ
1.9
2.9±0.2
0.4±0.1
0.4±0.1 0.4±0.1
0.4±0.1
2.8
+ 0.2
− 0.3
(0.8)
1.6
+ 0.2
− 0.1
0.10
0.40 ± 0.06
10 mm 10 mm
0.42 ± 0.08
1.27 ± 0.15
HA17431P/PJ/PA/PAJ
0.10 ± 0.10
2.03 Max
4.4
0.75 Max
85
14
4.85
5.25 Max
0.60 Max
0.5 ± 0.1
4.8 ± 0.3 3.8 ± 0.3
5.0 ± 0.2
0.7 2.3 Max
12.7 Min
0.5
1.27
2.54
0.60 Max
0.5 ± 0.1
4.8 ± 0.3 3.8 ± 0.3
8.0 ± 0.5
0.7 2.3 Max
10.1 Min
0.5
1.27
2.54
0.65 ± 0.1
0.75 Max
14 HITACHI
Section 5 MPAK-5 and UPAK Marking Patterns
The marking patterns shown below are used on MPAK-5 and UPAK products. Note that the
product code and mark pattern are different. The pattern is laser printed.
(b)
(2)
(c)
(4)
(1)
(a)
P4
HA17431VLP HA17431UA
NC PS
REF A K
(3) (4)
(1) (2)
(5)
Band Mark Band Mark
REF
AA
K
4A
HA17431UPA
(3) (4)
(1) (2)
(5)
REF
AA
K
4B
HA17432UA
(3) (4)
(1) (2)
(5)
Band Mark Band Mark
K
AA
REF
K
A
REF
4C
HA17432UPA
(3) (4)
(1) (2)
(5)
A
4F
Figure 5.1 MPAK-5 and UPAK Marking Patterns
Notes: 1. Boxes (1) to (5) in the figures show the position of the letters or numerals, and are not
actually marked on the package.
2. The letters (1) and (2) show the product specific mark pattern.
Product (1) (2)
HA17431VLP 4 P
HA17431UA 4 A
HA17431UPA 4 B
Product (1) (2)
HA17432UA 4 C
HA17432UPA 4 F
HITACHI 15
3. The letter (3) shows the production year code (the last digit of the year) for UPAK
products.
4. The bars (a), (b) and (c) show a production year code for MPAK-5 products as shown
below. After 2005 the code is repeated every 8 years.
Year 1997 1998 1999 2000 2001 2002 2003 2004
(a) Bar Bar Bar Bar None None None None
(b) None None Bar Bar None None Bar Bar
(c) None Bar None Bar None Bar None Bar
5. The letter (4) shows the production month code (see table below).
Production month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Marked code A B C D E F G H J K L M
6. The letter (5) shows manufacturing code for UPAK products.
16 HITACHI
Section 6 Ordering Information
Taping specifications must be attached after the product name. The quantity must be a multiple of
ordering unit (see table below).
HA17431VLP-EL 15,000pcs Quantity
Taping code
Product name
ex.
Table 6.1 Taping Specifications
Package Taping
Code Packing Ordering
Unit Illustration
MPAK-5 EL Embossed taping
L type in 180
φ
reel 3000 pcs
4.0
Feed direction
8.0
UPAK TL Embossed taping
L type in 180
φ
reel 1000 pcs
8.0
12.0
Feed direction
TO-92
TO-92MOD TZ Fan-folded taping in
336 × 262 × 47 mm3
box (TO-92),
Fan-folded taping in
330 × 200 × 43 mm3
box (TO-92MOD)
2500 pcs
12.7 Back
Adhesive tape
18.0
FP-8D EL Embossed taping
L type in 330
φ
reel 2500 pcs
8.0
12.0
Feed direction
HITACHI 17
Section 7 Application Examples
As shown in the figure below, this IC operates as an inverting amplifier, with the REF pin as an
input pin. The open-loop voltage gain is given by the reciprocal of “reference voltage deviation
by cathode voltage change” in the electrical specifications, and is approximately 50 to 60 dB. The
REF pin has a high input impedance, with an input current Iref of 3.8 µA typ (V version: Iref =
2 µA typ). The output impedance of the output pin K (cathode) is defined as dynamic impedance
ZKA, and ZKA is low (0.2 Ω) over a wide cathode current range. A (anode) is used at the minimum
potential, such as ground.
K
VCC OUT
VEE
A
REF
VZ ≅ 2.5V
−
+
Figure 7.1 Operation Diagram
18 HITACHI
7.1 Application Hints
No. Application Example Description
1 Reference voltage generation circuit
K
R
CL
Vout
GND
Vin
GND
REF A
This is the simplest reference voltage circuit. The
value of the resistance R is set so that cathode
current IK ≥ 1 mA.
Output is fixed at Vout ≅ 2.5 V.
The external capacitor CL (CL ≥ 3.3 µF) is used to
prevent oscillation in normal applications.
2 Variable output shunt regulator circuit
K
R
CL
Vout
GND
Vin
GND
A
R1
R2
REF
Iref
This is circuit 1 above with variable output
provided.
Vout ≅ 2.5 V ×Here, (R1 + R2)
R2
Since the reference input current Iref = 3.8 µA
typ (V version: Iref = 2 µA typ) flows through R1,
resistance values are chosen to allow the
resultant voltage drop to be ignored.
3 Single power supply inverting
comparator circuit
KVout
GND
Vin
GND
A
REF
VCC
RL
Rin
This is an inverting type comparator with an input
threshold voltage of approximately 2.5 V. Rin is
the REF pin protection resistance, with a value of
several kΩ to several tens of kΩ.
RL is the load resistance, selected so that the
cathode current IK ≥ 1 mA when Vout is low.
Condition
C1
C2
Vin
Less then 2.5 V
2.5 V or more
Vout
VCC (VOH)
Approx. 2 V (VOL)
IC
OFF
ON
HITACHI 19
No. Application Example Description
4 AC amplifier circuit
GND
KVout
Vin REF A
VCC
RL
R1
R2
R3
Cin
Cf
Gain G = (DC gain)
R1
R2 // R3
Cutoff frequency fc = 1
2π Cf (R1 // R2 // R3)
This is an AC amplifier with voltage gain G = –R1
/ (R2//R
3
). The input is cut by capacitance Cin, so
that the REF pin is driven by the AC input signal,
centered on 2.5 VDC.
R2 also functions as a resistance that determines
the DC cathode potential when there is no input,
but if the input level is low and there is no risk of
Vout clipping to VCC, this can be omitted.
To change the frequency characteristic, Cf
should be connected as indicated by the dotted
line.
5 Switching power supply error
amplification circuit
+
−
V+
V−
R
1
R
2
R
3
R
4
LED
Cf
Secondary
side GND
(Note)
Note: LED:
R
3
:
R
4
:
Light emitting diode in photocoupler
Bypass resistor to feed I
K
(>Imin)
when LED current vanishes
LED protection resistance
This circuit performs control on the secondary
side of a transformer, and is often used with a
switching power supply that employs a
photocoupler for offlining.
The output voltage (between V+ and V–) is given
by the following formula:
Vout ≅ 2.5 V ×(R1 + R2)
R2
In this circuit, the gain with respect to the Vout
error is as follows:
G = ×
R2
(R1 + R2)HA17431 open
loop gain ×Photocoupler
total gain
As stated earlier, the HA17431 open-loop gain is
50 to 60 dB.
6 Constant voltage regulator circuit
GND
VCC R1
R2
R3
Cf
Q
Vout
GND
This is a 3-pin regulator with a discrete
configuration, in which the output voltage
Vout = 2.5 V ×(R2 + R3)
R3.
R1 is a bias resistance for supplying the
HA17431 cathode current and the output
transistor Q base current.
20 HITACHI
No. Application Example Description
7 Discharge type constant current circuit
GND
VCC R
RS
Q
Load
2.5 V
+
−
IL
This circuit supplies a constant current of
IL ≅[A]
2.5 V
RS into the load. Caution is required
since the HA17431 cathode current is also
superimposed on IL.
The requirement in this circuit is that the cathode
current must be greater than Imin = 1 mA. The IL
setting therefore must be on the order of several
mA or more.
8 Induction type constant current circuit
GND
VCC
R
Q
Load
2.5 V
+
−
IL
RS
In this circuit, the load is connected on the
collector side of transistor Q in circuit 7 above. In
this case, the load floats from GND, but the
HA17431 cathode current is not superimposed
on IL, so that IL can be kept small (1 mA or less is
possible). The constant current value is the
same as for circuit 7 above:
IL ≅[A]
2.5 V
RS
HITACHI 21
7.2 Design Guide for AC-DC SMPS (Switching Mode Power Supply)
7.2.1 Use of Shunt Regulator in Transformer Secondary Side Control
This example is applicable to both forward transformers and flyback transformers. A shunt
regulator is used on the secondary side as an error amplifier, and feedback to the primary side is
provided via a photocoupler.
R1
R2R3
R4
Transformer
Photocoupler Light
emitting diode
Phototransistor
Output
C1R5
REF
GND
A
K
VK
IB
IF
HA17431
VF
SBD
PWM IC
HA17384
HA17385
Vref V0
(+)
(−)
Figure 7.2 Typical Shunt Regulator/Error Amplifier
7.2.2 Determination of External Constants for the Shunt Regulator
DC Characteristic Determination: In figure 7.2, R1 and R2 are protection resistor for the light
emitting diode in the photocoupler, and R2 is a bypass resistor to feed IK minimum, and these are
determined as shown below. The photocoupler specification should be obtained separately from
the manufacturer. Using the parameters in figure 7.2, the following formulas are obtained:
R1 = V0 − VF − VK
IF + IB, R2 = VF
IB
VK is the HA17431 operating voltage, and is set at around 3 V, taking into account a margin for
fluctuation. R2 is the current shunt resistance for the light emitting diode, in which a bias current IB
of around 1/5 IF flows.
Next, the output voltage can be determined by R3 and R4, and the following formula is obtained:
V0 = R3 + R4
R4× Vref, Vref = 2.5 V Typ
22 HITACHI
The absolute values of R3 and R4 are determined by the HA17431 reference input current Iref and
the AC characteristics described in the next section. The Iref value is around 3.8 µA typ.
(V version: 2 µA typ)
AC Characteristic Determination: This refers to the determination of the gain frequency
characteristic of the shunt regulator as an error amplifier. Taking the configuration in figure 7.2,
the error amplifier characteristic is as shown in figure 7.3.
When R5 = 0
When R5 ≠ 0
G1
f1fAC f2
G2
fOSC Frequency f (Hz)
Gain G (dB)
* fOSC : PWM switching frequency
Figure 7.3 HA17431 Error Amplification Characteristic
In figure 7.3, the following formulas are obtained:
Gain
G1 = G0 ≈ 50 dB (determined by shunt regulator)
G2 = R5
R3
Corner frequencies
f1 = 1/(2π C1 G0 R3)
f2 = 1/(2π C1 R5)
G0 is the shunt regulator open-loop gain; this is given by the reciprocal of the reference voltage
fluctuation ∆Vref/∆VKA, and is approximately 50 dB.
HITACHI 23
7.2.3 Practical Example
Consider the example of a photocoupler, with an internal light emitting diode VF = 1.05 V and IF =
2.5 mA, power supply output voltage V2 = 5 V, and bias resistance R2 current of approximately
1/5 IF at 0.5 mA. If the shunt regulator VK = 3 V, the following values are found.
R1 = 5V − 1.05V − 3V
2.5mA + 0.5mA = 317(Ω) (330Ω from E24 series)
R2 = 1.05V
0.5mA = 2.1(kΩ) (2.2kΩ from E24 series)
Next, assume that R3 = R4 = 10 kΩ. This gives a 5 V output. If R5 = 3.3 kΩ and C1 = 0.022 µF,
the following values are found.
G2 = 3.3 kΩ / 10 kΩ = 0.33 times (–10 dB)
f1 = 1/(2 × π × 0.022 µF × 316 times × 10 kΩ) = 2.3 (Hz)
f2 = 1/(2 × π × 0.022 µF × 3.3 kΩ) = 2.2 (kHz)
24 HITACHI
7.3 Circuit Example AC-DC SMPS
Photocoupler
Commercial
AC 100V
Rectifier bridge diode
Line filter
100µ
200V
1000µ
10V
RT
10k
220k
1/4W
22µ
50V
VIN
16.4V
141V
0.1µ
51
1k
4.7k
−+
BPS
1S2076A
DC
5V, 3A
OUTPUT
Vref
VIN
OUT
GND
COMP
FB
HA17384
HA17385 HA17431
2SK1567
SBD
HRP24
CS
RT/CT
+
−
+
−
+
−
+
−
1.8k
B
4.7k
1
2W
100p
150k
330p
CT
1000p
Transformer specification
example
EI-22 type core
(H7C18 × 06Z)
Gap length
lg = 0.3mm
Transformer coil example
P: 0.5φ80T/570µH
S: 0.5φ16T Bifiler/22µH
B: 0.2φ44T/170µH
330
3.3µ2k
+
−
Figure 7.4 Circuit Example AC-DC SMPS
HA17431 Series Shunt Regulators
Application Note
Publication Date: 1st Edition, July 1997
2nd Edition, August 1999
Published by: Electronic Devices Business Group
Hitachi, Ltd.
Edited by: Technical Documentation Group
UL Media Co., Ltd.
Co
py
ri
g
ht Hitachi, Ltd., 1997. All ri
g
hts reserved. Printed in Ja
p
an.
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