Battery charger NG3
D01058-02 4
Operating principle
The battery charger considerably affects battery life and performances, which is the main part of every
electric vehicle.
A non controlled traditional battery charger (rectifier) provides a simple direct AC/DC conversion.
Disadvantages of this solution are:
• Low efficiency
• Large physical size
• Long charge times
• Charge depends on changes in the mains supply (with
overcharge danger in the final charge phase)
In modern battery chargers these disadvantages are solved with an indirect AC/DC conversion, by
passing through an intermediate DC/DC conversion.
This is the usual method of operation for the
SMPS (Switching Mode Power Supply) at
high power. This solution gives a good
performance for minimum costs and physical
dimensions using switches more faster and
powerful (modern technology).
The main advantages of this solution are:
• High efficiency
• Reduced dimensions
• Short charge times
• Charge independent from the changes of the mains supply
• Electronic control that provides the desired charge curve
The advent of electrical problems (due to commutation) has imposed the introduction of adequate filtering
to satisfy requirements of EMC 89/336/EEC directive for electromagnetic compatibility.
Block Diagram
STAGE
POWER
E
L
N
F1 F2
LOGIC
CONTROL
FILTER
FILTER
FILTER
RECTIFIER
RECTIFIER
RECTIFIER
AND
AND
AND
FILTER FILTER
EMI
EMI
Battery
v
DC
AC
Battery
i
v
DC
DC
DC
C
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