06-02-2013, 10:41 AM
Electric bicycle charger
1Electric bicycle .doc (Size: 114 KB / Downloads: 42)
INTRODUCTION
To lead-acid battery electric vehicles, nickel cadmium batteries to add energy, through the charger. Many different types of chargers. Generally distinguish between whether the frequency transformer can be divided into two broad categories. Cattle commonly used high-power frequency transformer ring. Although low efficiency, but current (available at 30A), and reliable. Electric three-wheeled cargo, without exception, to use it, and 30Ah batteries are mostly used the following switching power supply technology, thus improving efficiency, get rid of the bulky low frequency transformer. Electric bicycle charger at 2A maximum charge current is mostly about.
1. Using switching power supply technology for electric bicycle charger
(1) Shandong GD36 Charger
Circuit diagram shown in Figure. The charger for the half bridge charger. The main performance indicators: Input voltage :170-260V; output voltage: 44 V (adjustable); Maximum charge current: 1.8A; floating charge current: 200 ~ 100mA.
1) circuit
The main mains charger rectifier filter circuit, self-excited half-bridge converter plus he excited, PWM control, voltage control, current control, output rectifier filter six parts.
After filtering the mains rectifier diodes D1 ~ D4 220V/50Hz bridge rectifier, filter capacitor C5 ~ C7 to get around 310V DC voltage, as the switching converter power supply.
Self-excited half-bridge output circuit plus he excited mainly by Q1, Q2, B2, B3 and other components.
Self-excited to start the circuit is characterized by a self-excited start, the control circuit to provide the necessary auxiliary power by itself, without a separate. Self-excited oscillation is generated by core saturation, the specific process is: power, C5, C6 on the 150V voltage by R5, R7, R9, R10 to switch Q1, Q2 provides base bias. TR5 set by the bias and the micro-Q1 turns on, the drive transformer B2, 2 - 4 2 winding polarity is induced in the foot now, 4 foot negative voltage, so 1 - 2 1 foot winding induces a positive, 2 negative voltage pin added to the emitter of Q1, Q1's conduction speed. This is a very strong positive feedback process, Q1 quickly saturated conduction. At the same time, 3 - 5 3 foot winding induces a positive, 5 foot negative voltage, so that Q2 closed.
Q1 saturated conduction, the 150 voltage to B3 1 - 2 storage charge the main winding, coil current and the magnetic field it produces increases linearly with time. But when the magnetic flux density Bm increases to the saturation point, the inductance decreases rapidly, Q1's collector current sharp increase in the rate of increase than the increase of its base current, Vce increasing, so the Q1 out into the enlarged area saturated, to promote the transformer B2, 2 - 4, 1 - 2, 3 - 5 winding induced voltage will be reversed. This is also a strong positive feedback process, the result is close Q1, Q2 saturated conduction. Since then, this process is repeated and the formation of oscillation.
Works as follows:
He oscillation: the process of self-excited oscillation, B3 of the secondary output voltage through D9, D10 full-wave rectifier, C19 filter, PWM control circuit to establish the necessary working power chip TL494. TL494 to work, the Q3, Q4 output phase of the PWM pulse is 180 °, the B2 6 - 7, 7 - 8 winding induction to 1 - 2 or 3 - 5 winding. So Q1, Q2 will be turned by the self-excited PWM pulse excited in his turn driven by conduction. B3 secondary 9 - 7, 9 - 8 winding output voltage is full wave rectified by D15, C21 filter by +44 V voltage to charge the battery.
D6, D7 are two clamping diodes. Protect the switch Q1, Q2. Protection mechanism is the primary flyback relief B3 and leakage inductance energy storage, to eliminate anti-peak voltage. When the Q1 into cutoff and by the turn has not yet turns on Q2, D7 conduction, the flyback energy regeneration to charge C6; when Q2 turns into a cut-off while the then not turns on Q1, D6 conduction, the flyback energy regeneration to the C5 charge. On the one hand to eliminate the anti-peak voltage, on the other hand because of the energy back to the sending power flyback and greatly improve the power efficiency.
TL494 PWM control to the core composition. C12, R19 and the internal oscillation circuit is formed when these two parameters as icons RC component values, the oscillation frequency of about 50kHz. (13) feet to +5 V, pulse output mode is set to push-pull output. 8, (11) push-pull output pin pulse width modulated, amplified by the evacuation of half-bridge driver circuit output stage, control, Q1, Q2 turns conducting.
R20, R24 partial pressure control of dead-end set foot 4 potential, limit the maximum on-duty cycle less than 45%. C18 is a slow start capacitor, connected to the power, C18 both ends of the voltage is zero, 4 the foot of the potential is approximately +5 V, the output pulse duty cycle is zero. With the C18 charge, 4 pin voltage decreases, conduction duty cycle increases, the output voltage gradually controlled.