Electric bicycle controller working principle analysis - Power Circuit - Circuit Diagram

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First, the working principle of the controller

Referring to Figure 1, the main control chip of the controller is IC1 (TL494), which uses low-level brake and positive control mode. The 8-pin of IC1 can output PWM widened pulse, and the width is controlled by the voltage value of the signal line 3 pin. . The widened pulse square wave is supplied to the b pole of the transistor V2, and the MOS tube driving circuit composed of V2 shapes and amplifies the square wave to drive the high power tube V1, and the output end of the controller connected to the motor can output the same voltage value as the power source. .

Second, maintenance technology

1. It is necessary to judge whether the controller is faulty or not. After the power supply is normal, check the brake control line. In the electric vehicle with low-level braking mode, the two wires of the brake lever are normally at a high level, and the brake lever is pinched, and the voltage between the two wires is 0V. In the actual measurement, do not open the connection line between the brake lever and the controller, and insert the test lead into the root of the lead to touch the metal piece.

Then measure the voltage of the turn-over line. There are usually three control lines on the turn. The two sides-red-black are the positive power supply and the ground line respectively. The other different color line is the turn signal line.

The electric vehicle adopts the positive mode, and the signal line changes with the twist of the turning handle, and the voltage changes from low to high, and the maximum can reach 5V. The starting voltage values ​​are not the same for each car, but generally can reach 2.5V or more. The PWM chip should be able to output a drive pulse, and the output line has the same voltage value as the power supply voltage. In contrast, the control mode of the electric vehicle turns the signal line voltage from high to low, but this method is rare.

2. Controller overhaul experience

If the brake lever and the handle are normally controlled and the power supply is normal, the reason for the absence of the output voltage is that the controller is faulty. It can be removed from the car and taken to the workbench for inspection. Because the motor has been disconnected, it is no longer necessary to use the user's battery as the power source, and a small DC power supply can be made. As shown in Fig. 2, the transformer can use a double 17.5V winding of a black and white television, and can output a DC voltage of about 48V.

Disassemble the controller, first visually check the components with obvious appearance damage, whether there is open route strip or virtual welding or desoldering. It is important to measure whether the two diodes of D1 and MOS transistor V1 are short-circuited. This step is very important.

We will make a device that can simulate the turning handle, as shown in Figure 3. Two 5kΩ resistors are connected in series, and the two ends are connected to the power supply, the ground line, the intermediate and indirect signal lines, and the signal line can be supplied with a voltage of 2.5V to the main control chip. Connect the self-made 48V power supply and turning device, the measurement key points have the following two: (1) The G pole voltage of the MOS tube should be 6V or more, generally not more than 7V. If it is normal, check MOS tube V1 on the premise that D1 is normal; if it is abnormal, measure key point 2. (2) The b-pole voltage of the transistor V2 should be above 6V, generally not exceeding 7V. If the voltage at this point is abnormal, check TL494. First, measure whether the power supply 12 feet have 12V voltage. If there is any replacement of TL494, if not, check the relevant power supply circuit. The circuit mode of various controllers using the operational amplifier IC is basically the same as that of FIG. 1, and the maintenance method can also refer to the above procedure. Since many manufacturers erase the chip model, Table 1 provides the pin function of the chip with the brush controller. Use a meter of a multimeter to connect a thick black lead of the controller. This is usually a ground wire. The other meter measures the legs of the chip. The pin and ground are 0Ω. This is the grounding of the chip. Foot, refer to Table 1 to know that the LM339 model chip.

Since the starting current of the motor is large, when replacing the MOS tube, a tube with a withstand voltage higher than 60V, a rectification value of 40 to 80A, a power greater than 100W or the same parameters as the original MOS tube should be used.