To use more electric bicycle charger switching power supply, model are numerous, but very much the same circuit structure, the main difference in the selected pulse width modulation (PWM) chip different (eg UC3845, UC3842, SG3524, TL494). Proton brand is the best charger, for example, describes the principles and troubleshooting methods.
Electric Bicycle Circuit
First, the circuit
According to Teng physical mapping of the good brand battery charger circuit shown in Figure 1. Machine can be divided into generation and promotion of PWM circuit, power switching conversion circuit, charge status indicator circuit and the AC input circuit of four parts.
I. PWM generation and to promote the circuit
PWM generation circuit by the IC1 (TL494) and peripheral component composition. TL494 is a PWM switching power supply integrated circuits. Pin function and the internal block diagram shown in Figure 2.
IC1 first 5, 6 foot external C1O, R19 is the timing components, determine the oscillation frequency of the oscillator ramp, f = 1.1/RC, according to the figure a value of 50kHz. (14) feet is +5 V reference voltage output, in addition to on-chip use, but also for the direct or partial pressure after the first 2, 4, (13) feet and IC2 use. (13) feet to control the output side of the foot received in the low single-ended output mode, then the figure (14) +5 V pin high, the double-ended output. Section 4 dead-time control pin end, the decision of the foot potential dead time. Potential rise, extend the dead time, output pulse width becomes narrower, when the potential greater than the ramp voltage, the output pulse width will become narrow, or even to stop vibration. Where the output of the half bridge or full bridge with switching circuit, dead time must be set correctly so that both switches are on simultaneously, the risk of a power short circuit. The potential of the figure by the reference voltage pin R24 and R20 by the partial pressure of the acquisition, the measured voltage is 0.46V. C15 is a soft-start capacitor. Section 1, 2 feet and (16), (15) feet within two voltage comparators IC1 positive and negative input, respectively, as the charging voltage sampling and charge current sampling. +44 V charging voltage by R28, R27 and R26 divider feedback to 1 feet. C15 is a soft-start capacitor. 2 feet first reference voltage potential from the R23 and R3 by the partial pressure of the acquisition, measured as 3. 2V, the first potential 1 feet higher, the more narrow the output pulse width, the lower the charging voltage; contrast pulse broadening, charging voltage increases. +44 V in order to achieve stability in the purpose of charging voltage. Ra is the charging voltage debug resistance, Ra, and the smaller R26's parallel resistance, the higher the charging voltage. R29 is the charge current sampling resistor, obtained by the resistor voltage change, the R13 into the IC1 (15) feet. The greater the charge current, (15) feet lower potential. When the first (15) feet less than the potential in (16) feet (ground) potential duration, IC output will be closed in order to achieve over-current protection. Rb is the over-current protection debug resistance, the machine is set to 1.8A.
Changes in the external input signal, the chip circuit processing, from the first 8, (11) lost a pair of the same size foot, the phase difference of 180 °, variable pulse width square wave, the V3, V4 push-pull amplification, the transformer T2 coupled to the power switching conversion circuits.
2. The power switch converter
V1, V2 are two switches connected in series in the +300 V supply voltage and ground to form a half bridge switching circuit, the pulse width modulated under the effect of rotation on and off, the ten high-frequency alternating current is converted to 300V DC . Current flow diagram shown in Figure 3. V1 turns on, C5 ten → V1 ce → T2 of 2, 4 terminal → T3 of 2, 1 end → C6 → C5-. V2 turns on, C5 → C4 → T3's ten 1, 2 end → T2's 4, 2 end → V2 ce → C5-. T3 secondary output voltage by D15, C17 full-wave rectifier filter, the output for the ten 44V battery. Another secondary winding T3 by D9, D10, C18 rectifier filter, the output from IC1 and IC2 ten 24V power supply.
R7, R9 is the startup resistor, in turn instantly to the V1, V2 base to provide the excitation current, the circuit self-excited to start. C7, D5, R4 (or C8, D8, Rl1) is to accelerate the network. D6, D7 for the protection diodes. C3, R1 for the peak absorption of the network.
3. AC input circuit
220V, by the bridge rectifier D1-D4, C5 filter, to obtain +300 V voltage conversion circuitry to the power switch.
4. Charging status indicator circuits
By the IC2 (HA17358) and two-color LED LED2 composition. IC2 is a dual op amp integrated circuits, where access to two voltage comparators. Charge current sampling resistor R29 by the voltage change signal obtained by the R31 into the IC2 first 2 feet. The initial charge, charge current is high, R29 on the blood pressure increase (Note: R29 to ground voltage on the negative voltage). Section 2 3 feet feet less than the first potential potential, the first 1 pin output high, the charging indicator light LED2-A light. When the battery is nearly full, the charging current decreases, R29 to reduce the voltage, when the first 2 3feet feet greater than the potential of potential, the first 1, 6 pin goes low, the first 7 pin output high, full of light LED2-B light.
Rc is the charge status indicator to adjust resistance, resistance selection of appropriate access, so that the instructions to set the state (200mA).
Second, the repair method
This machine has hot and cold to the point manner, measurements do not choose the wrong point of reference. Electricity and heat to the same, For power maintenance, should be added with the isolation transformer to prevent electric shock. In most cases, the use of multimeter resistance profile, online check, you can find the faulty components. PWM circuit with an external power supply repair (ie, +24 V at both ends of the external filter capacitor C18 15 to 20V power supply) is the most safe and effective. Power test machine, under normal circumstances, LED1 should light up. Ten 44V terminal not connected load, full instructions LED2-B should be light (green), +44 V voltage slightly, measured as +42 V, not to mistaken for failure. Continued into the off-load (1 000W heating wire can be used on behalf of) charging indicator LED2-A should be light.
1. Insurance blown, black glass wall or burst pipe.
This phenomenon shows that there is a serious short circuit between the circuit to filter C5, the mains rectifier D1 - D4 switch V1, V2, D15, and other components at the same time rectifying the breakdown common. Rx1 file with the multimeter to identify faulty components in the road.
2. The power indicator LED1 is not lit, no ten 44V voltage output.
Fault that the circuit did not work in +300 V voltage output under normal circumstances, should focus on checking the startup resistor R7, R9 or without open circuit, V1, V2 base circuit components of D5, R4, R6, D8, R11, R8 damage, IC1, V3, V4 pulse width modulated output without damage.
External power supply, measured by the oscilloscope first 5 IC1 feet, should be the normal form of jagged Sasser, if the timing components R19, C10 no wave normal can be determined IC1 bad. IC1 first 8, (11) feet shall be measured square wave was normal, when measured no waveform or abnormal, if the pin voltage is normal, replace IC1. If the V3, V4 wave is not normal, check Rl2, V3, V4 and peripheral components.
Schedule and Figure 4 shows an external 15V power supply ten, ten 44V output load conditions IC1, IC2 to ground voltage of the pin and key plot points for the maintenance of reference.
ICl (14) pin voltage (+5 V reference voltage) if the normal, ICl section (13), 2, 4 pin voltage are not normal, IC2 pin voltage will be related to abnormal. Disconnect the IC1 (14) feet outside the circuit, if the pin voltage is not normal, you can determine the IC1 damage.
