Story Transcript
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Low Voltage
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High Voltage
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Replaces the traditional vehicle generator / alternator
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Converters “convert” the source power (whether it is ac or dc) to a lower or higher output value
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• Two types of converters in the automotive realm:
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o “Buck” Converter – converts the source power to a lower output value
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o “Boost” Converter – converts the source power to a higher output value
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• Example: GM 2-Mode (Tahoe/Yukon) system is using a boost function in the dc-dc Converter to charge the high voltage battery pack
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o The Electrical Power Law and operating frequency will dictate electrical current output based on the output voltage of the converter © FTA & QTS LLC
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Chevrolet Volt dc-dc Converter
Courtesy: General Motors Co. © FTA & QTS LLC
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DC Input Capacitors and Inductors to reduce IGBT
Module electrical (EMC) noise by using bus bar in lieu of cables or shortening cables
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Example: Sine Wave Input Filter
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Common Mode Choke shown
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Courtesy: EPCOS
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Chevrolet Volt dc-dc Converter
HV Input Connection
CAN Connection
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12V Chassis Ground Connection
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+ 12V Output Terminal Connection
Courtesy: General Motors Co. © FTA & QTS LLC
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Courtesy: Navistar
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Tandem 4kW dc-dc Converters (8kW total)
© FTA & QTS LLC
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Battery Pack to dc-dc Converter Power Connection
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dc-dc Converter
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Power Inverter
dc-dc Converter
Battery Pack
Hybrid Controller © FTA & QTS LLC
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12V Output to Battery + & -
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HV Battery Connections + & to dc-dc Converter Input
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dc-dc Converter Air Cooled
© FTA & QTS LLC
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Ford Escape Hybrid dc-dc Converter
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Note: two liquid cooling hoses
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connected to the dc-dc Converter
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for cooling
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12 Volt Output Connector
36 Volt Output Connector
APM Input/Output Control Connector
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dc-dc Converter Location
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Mounted on Bottom Side Of Power Inverter Assembly © FTA & QTS LLC
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dc-dc Converter System
© FTA & QTS LLC
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dc-dc Converter Switching Hz Benefits of High Switching Frequency
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1. Smaller converter
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• Smaller can be cheaper – up to a certain power output
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• Beyond that power level small size could be worth some added
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cost
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2. Transient response can improve with higher switching frequency.
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1. Efficiency is worse
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Drawbacks of High Switching Frequency
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Switching loss is proportional to switching frequency
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FET Switch drive power is also proportional to frequency
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2. Maximum conversion ratio (maximum VIN) is lower © FTA & QTS LLC
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12V (14.5V) Output
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L3
Q1
Q2
C1
L1
Q3
Q4
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L2
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Circuit Construction
C1 = Capacitor D1,2 = Rectifier Diodes L1,2,3 = Inductors Q1,2,3,4 = High Power Transistors (IGBT)
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L1, Q1,2,3, & 4 = PWM switching circuit (≈25kHz) L1 & L2 = Transformer D1, & D2 = Full wave rectifier L3 & C1 = Output filter for ripple smoothing
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1. 2. 3. 4.
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D2
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12V (14.5V) Output
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L3
Q1
Q2
C1
L1
Q3
Q4
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L2
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Circuit Construction
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L1, Q1,2,3, & 4 = PWM switching circuit (≈25kHz) L1 & L2 = Transformer D1, & D2 = Full wave rectifier L3 & C1 = Output filter for ripple smoothing
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1. 2. 3. 4.
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D2
C1 = Capacitor D1,2 = Rectifier Diodes L1,2,3 = Inductors Q1,2,3,4 = High Power Transistors (IGBT)
Note: 25kHz is only an example frequency
© FTA & QTS LLC
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Basic dc-dc Converter Design L1 (Transformer Primary Winding)
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Output During First Half Cycle Operation
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12V (14.5V) Output
To Power Inverter High Voltage Bus
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•12V Battery •Vehicle Electrical System
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Q3
Q4
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Load
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D1
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Resulting Waveform
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When L1 is switched OFF by Q4 and Q1 its magnetic field collapses resulting in the illustrated polarities. The resulting waveform is shown.
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Animation
© FTA & QTS LLC
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L1 (Transformer Secondary Winding)
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Output During Second Half Cycle Operation
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12V (14.5V) Output L3 D1 C1
•12V Battery •Vehicle Electrical System
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Q4
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Load
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D2
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Resulting Waveform
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When L1 is switched OFF by Q3 and Q2 its magnetic field collapses resulting in the illustrated polarities. The resulting waveform is shown.
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Animation
© FTA & QTS LLC
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L1 (Transformer Primary Winding) Output During Both First & Second Half Cycle Operation
To Power Inverter High Voltage Bus
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12V (14.5V) Output
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Basic dc-dc Converter Design
L3 C1
•12V Battery •Vehicle Electrical System
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Resulting Waveform
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When L1 is alternately switched ON / OFF by Q1,2,3 & 4 its magnetic field collapses during both the First and Second half switching cycles and this results in an alternating current waveform
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Basic dc-dc Converter Design
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Resulting Waveform
First Half Cycle Operation
Because D2 is not operational in this half wave rectification cycle, this results in half of the electrical power that could be delivered in a full wave rectification cycle
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14.5V
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-5V
To Power Inverter High Voltage Bus
D1
Load
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Q4
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•12V Battery •Vehicle Electrical System
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12V (14.5V) Output
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Diode reverse biased (turned off) power not usable during this half-cycle
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Polarities of L1 during magnetic Field collapse (field turned OFF) © FTA & QTS LLC
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Basic dc-dc Converter Design Second Half Cycle Operation
To Power Inverter High Voltage Bus
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Diode reverse biased power not usable during this half-cycle
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•12V Battery •Vehicle Electrical System
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C1
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Load
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12V (14.5V) Output
14.5V
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Resulting Waveform
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D2
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Because D1 is not operational in this half wave rectification cycle, this results in half of the electrical power that could be delivered in a full wave rectification cycle
0V
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-5V
© FTA & QTS LLC
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Waveform Outputs from Rectifier Diodes
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Waveform Output From PWM Switching Circuit and L1
25kHz
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First Half Cycle Output
50kHz
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Combined First and Second Half Cycles
25kHz
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Second Half Cycle Output
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Output Waveform Type: Fluctuating or Pulsating dc
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Output Frequency: 50kHz 25kHz input frequency 50kHz output (ripple) frequency through full wave rectifier
Note: 25kHz and 50kHz are only example frequencies © FTA & QTS LLC
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Comparison of Unfiltered and Filtered Output Waveforms
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Unfiltered waveform outputs from Rectifier Diodes D1 & D2
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Filtered waveform outputs from Rectifier Diodes through L3 & C1
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Filtered output provides a smoother dc voltage, not pulsating/ripple dc
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Pulsating dc causes electrical “noise” and can cause heating of other electrical and electronic omponents
© FTA & QTS LLC
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dc-dc Converter Testing
Power Inverter/dc-dc Converter
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dc/dc Converter
Toyota Prius Hybrid System
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MG1 Inverter
12 V Battery
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Controller
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MG1 (Generator)
Engine
MG2 (Motor – Generator)
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Test dc-dc Converter by load testing using Carbon-Pile equipment (i.e., VAT 40/60)
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95 Amps
MG2 Inverter
Battery Pack
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dc-dc Converter Testing
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Amps
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Maximum Output kW
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Prius 2003 Prius 2004
AU N Amps are specified at 12.8 – 13.8V Volts
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Chev. Yukon 2010
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Chev. Volt 2012
© FTA & QTS LLC
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dc-dc Converter
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CAN Diagnostics
© FTA & QTS LLC
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dc-dc Converter 12 Volt
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Over Voltage Fault
dc-dc Converter 42 Volt
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Over Voltage Fault
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dc-dc Converter 42 Volt Power Supply Fault
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dc-dc Converter 12 Volt Power Supply Fault (Buck)
dc-dc Converter 42 Volt
Under Voltage Fault
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dc-dc Converter ≈300 Volt
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Over Voltage Fault
dc-dc Converter Over Current
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dc-dc Converter ≈300 Volt
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Under Voltage Fault
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dc-dc Converter Under Current
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Under Voltage Fault
Auxiliary Battery Voltage Low
dc-dc Converter Over Temp
dc-dc Converter 12 Volt
Auxiliary Battery Voltage High
dc-dc Converter ≈300 Volt Power Supply Fault (Boost)
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Basic dc-dc Converter Diagnostic Codes
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dc-dc Converter Fault 34