Title: Battery%20Voltage%20Boost%20Regulator
1Battery Voltage Boost Regulator
- Solving the Mary Gomez Park Incident
2The Mary Gomez Park Incident
- Yaesu FT-840 transceiver received bad (terrible)
signal quality reports on CW after being operated
on battery power for an extended period of time. - Believed to be a result of the dc input voltage
being out-of-spec low. - Actual battery voltage was near 11V
- FT-840 Spec is 13.5V /- 10 (12.15 to 14.85)
3Specification Review
- Battery Specs (100 SOC Voltage)
- Deep Cycle (Johnson Controls)
- 2.11 V/cell or 12.66 V
- Sealed Lead-Acid (Power Sonic)
- 2.15 V/cell or 12.9 V
- Transceivers Specs
- Yaesu FT-840
- 13.5 V 10 (12.15 to 14.85 V)
- Yaesu FT-847
- 13.8 V 10 (12.42 to 15.18 V)
- Alinco DX-70TH, ICOM IC-706MKIIG, Kenwood
TS-2000, Yaesu FT-857 - 13.8 15 (11.73 to 15.87 V)
4Possible Solutions
- Add a second battery (or a cell) in series with
the primary battery - Raise primary battery dc voltage to 14 or 18 or
24 volts and regulate down to 13V - Use a modified/enhanced computer UPS
- Let the primary battery power the UPS and let the
UPS power the transceiver ac power supply - Use a dc/dc converter and regulator
- Use a conventional dc/dc converter to provide 18V
then regulate down to 13V - Use a boost supply in series with the battery
- Add a differential voltage to the primary battery
voltage
5QST to the Rescue
- QST Article
- A 12V dc Boost Regulator for Battery Operation
- Daniel R. Kemppainen, N8XJK
- November 2004, page 37
- Quote from the article
- A dc-dc boost switching converter is the answer
to low voltage battery problems for mobile,
portable or emergency-power operation
6Step 1 Check the Current Status
- Contacted the author regarding availability of
bare PC board - Author responded that circuit had been redesigned
and that farcircuits had PC boards for sale - www.farcircuits.net
- Author also stated that he has uploaded the new
design to the ARRL website - www.arrl.org/files/qst-binaries/
7Step 2 Build It
- Procure the PC board and the components
- FAR Circuits
- PCB, E-core and bobbin, toroid core
- Digikey
- Filter capacitors, power MOSFETs, Schottkey dual
diode - Anything that needs to fit the PCB layout
- Anchor Electronics
- Miscellaneous ICs, semiconductors, resistors,
capacitors - Wind the transformer
- Wind the filter inductor
- Stuff and solder the PC board
- Cut, bend and drill some aluminum
- Final electrical/mechanical assembly and heat
sinking - Test
8The Finished Product
9PCB Top
PC Board (Top)
10PCB Bottom
PC Board (Bottom) Note the 18 SMT capacitors
installed
11Transformer could be salvaged from a PC power
supply and rewound
12N8XJK Schematic
13Power Supply 101
14Battery Boost Configuration
15N8XJK Design Concept
- The circuit is best visualized starting with a
full-wave power supply using a transformer with a
center tapped secondary. - The center tap, rather than being grounded, is
connected to the high side of the battery so that
the power supply adds to the battery voltage. - Feedback from the total output voltage back to
the full-wave power supply causes the power
supply to modulate its output voltage to keep the
sum of the battery voltage plus the power supply
voltage constant. - The power supply that supplies the additional
voltage is a switch-mode design that operates
from the same battery that is supplying the
baseline power. - The IC that drives the switch-mode power supply
provides the regulation by modulating the pulse
width.
16N8XJK Schematic
17N8XJK Block Diagram
Input fuse filter F1, F2, C1-C4
Switching transistors Q1/Q3/Q6 and Q2/Q4/Q5
Transformer and rectifier T1, D7
Low pass filter L1, C5-C12
13.8 Vdc
9-12 Vdc
Pulse Width Modulator (PWM) U1
Output voltage sensing R3, R4, R5, R16
Low battery protection U2, Q7
5.0V
Reference voltage divider R1, R2, C15
2.5V
RF detect Q9, Q8, Q7
RF Sample
PWM IC compensation C17
PWM Enable
PWM operating frequency C16, R6
18N8XJK Schematic (simplified)
RF sense/PWM enable
Low battery protection/PWM disable
19User Comments/Modification
- Battery protection circuit
- Reacts too quickly (false alarms)
- Can only be reset by removing input power
- RF detection/enable
- Boost power supply turned on only during transmit
- Different voltage during transmit and receive
- Not recommended IMHO
- Quiescent current is only 22 mA
I disabled battery protection RF detection by
removing U2 and grounding emitter of Q7 (jumper
U2-1 to U2-12)
20Test Results
- Test Duration 6 minutes, continuous
- Input Voltage 12.16 V dc
- Output Voltage 13.0 V dc
- Output Current 16 A dc
- Maximum Temperatures (IR Thermometer)
- Transformer 145 deg F
- Diode area 180 deg F
- Heat sink area Very hot to touch
- Filter capacitors Slightly warm
- Switching Frequency 40 kHz
- Ripple voltage 17 mV p-p
21Test Results (Continued)
- Quiescent current (no load)
- Input 12 Vdc, Output 13.4 Vdc
- Input current 21.8 mA
- Output voltage range adjustment (no load)
- Input 12 Vdc
- Output voltage 11.9 Vdc to 15.3 Vdc
- Minimum input voltage for 13.4V output (no load)
- 7.6 Vdc
22Parts Selection
- This power converter operates at about 40 kHz,
not 120 Hz - Conventional aluminum electrolytics are
ineffective as filter capacitors - Use low impedance (ESR) capacitors as specified
- The traditional 2N3055 NPN silicon transistor
cannot switch fast enough - Also power dissipation
- Use HEXFET Power MOSFET as specified
- The rectifier diodes need to be low forward
voltage drop (desired) and fast switching
(required) - Use Schottky rectifier as specified
- SMT capacitors added by the author (18 total)
indicate probable RFI issues fixed
23Parts Selection (Continued)
- FAR Circuits has the double-sided PCB (for new
design) for 17.00 - Add 8.00 for the T1 E-core and the L1 toroid
core - Or scavenge the cores from a defunct PC power
supply - Order C1 thru C12 from DigiKey (dont substitute)
- Order U1 from DigiKey (limited availability)
- Order Q5, Q6 and D7 from DigiKey (limited
availability) - Order C13 thru C15 from DigiKey (Panasonic parts)
- Order C17, C18, C21 from DigiKey (Kemet parts)
- Order R16 from DigiKey (fits the PCB)
- Remaining ICs, transistors, resistors and
capacitors can be purchased from Anchor
Electronics in Santa Clara for less than 9.00 - Total cost will be under 100.00 (Ive spent
81.58) - Jameco may also be a source
24Design Comments
- C1 thru C12 voltage ratings are marginal (16V in
13V circuit) - Probably ok since problem was input voltage too
low - And the output voltage is regulated
- Input has capability for two fuses in parallel
- Added by author in response to user requests
- This can be risky since load sharing is not
guaranteed - Why use 2.5V reference for comparator input when
5V would provide more sensitivity to output
voltage variations? - Apparently older versions of the LM3524 were not
suited for a reference input voltage as high as 5V
25MFJ-4416 Version
- Commercial version from MFJ
- Note adition of series RC snubbers and crowbar
circuit - Redesigned LV RF detect
- Shipped with battery protection circuit disabled
- 139.95
26The End
- Mary Gomez Park Incident Solved