A DC charging pile contactor control system

Abstract

The present invention relates to a DC charging pile contactor control system, which includes a power input unit, a voltage conversion unit, a timer unit, a power switching drive unit, a power switching output unit, and a coil protection unit. The voltage conversion unit includes a 3.3V voltage conversion unit and a 5V voltage conversion unit. The coil protection unit includes an input protection unit and an output protection unit. The power input unit is divided into three paths after being protected by the input protection unit: the first path generates 3.3V through the 3.3V voltage conversion unit as a holding voltage and is connected to the source switching output unit; the second path generates 5V voltage through the 5V voltage conversion unit, connects to the timer unit, and supplies power to the timer; the third path 12V is used as the rated driving voltage of the contactor and is directly connected to the source switching output unit. The present invention is provided with dual power supplies and an automatic switching power supply circuit, does not occupy the charging pile main control MCU resources, effectively reduces the heat generated by the contactor itself, and controls the two contactors at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current contactor control, and in particular to a direct current charging pile contactor control system. Background Art

[0002] At present, the rated current of the DC contactors used in small-power DC charging piles is basically below 100A, and DC contactors with current below 100A on the market are basically not equipped with energy-saving control boards, resulting in large power consumption of the DC contactors, generally above 5W, and serious self-heating. According to actual measurements, at an ambient temperature of 25℃, driven by 12V voltage, the temperature can reach above 70℃ after 1 hour without load, and the temperature rise exceeds 45k. Once loaded, the temperature will be even higher, seriously affecting the safe operation of the contactor itself and other surrounding devices, and also having a negative impact on the service life of the contactor itself and the energy efficiency conversion of the charging pile.

[0003] Existing contactor energy-saving control solutions typically use PWM duty cycle adjustment to adjust voltage. This approach not only consumes the MCU resources of the charging pile control board, but the rapid switching of PWM waves can cause power and signal noise, interfering with other circuits. In actual charging pile designs and applications, the motherboards of low-power DC charging piles typically directly output a 12V control voltage to control contactor engagement. This results in excessive contactor power consumption and severe self-heating, seriously impacting the contactor's service life, as well as the overall power consumption and safety of the charging pile. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a DC charging pile contactor control system that effectively reduces the heat generated by the contactor itself and can control two contactors at the same time.

[0005] The object of the present invention is achieved like this:

[0006] A DC charging pile contactor control system includes a power input unit, a voltage conversion unit, a timer unit, a power switching drive unit, a power switching output unit, and a protection unit. The voltage conversion unit includes a 3.3V voltage conversion unit and a 5V voltage conversion unit. The protection unit includes an input protection unit and an output protection unit.

[0007] The power input unit is divided into three paths after being protected by the input protection unit: the first path generates 3.3V through the 3.3V voltage conversion unit as a holding voltage and is connected to the power switching output unit; the second path generates 5V voltage through the 5V voltage conversion unit, which is connected to the timer unit to power the timer; the third path 12V is used as the rated driving voltage of the contactor and is directly connected to the power switching output unit; the timer unit outputs a high level according to the set time, is connected to the power switching output unit through the power switching drive unit, selects the corresponding voltage output, and drives the DC contactor after passing through the output protection unit;

[0008] The power switching output unit includes a relay K1, diodes D2~D7 and a resistor R3, and has two power inputs of 12V and 3.3V. The 12V power supply is connected to pin 5 of the relay K1 after passing through the diode D3, and the 3.3V power supply is connected to pins 3 and 4 of the relay K1 after passing through the diode D2; a diode D7 is connected in parallel to pins 1 and 2 of the relay K1; one side of the resistor R3 is connected to the 12V power supply, and the other side is connected in series with the anode of the light-emitting diode D6, and the cathode of the diode D6 is connected to the power switching drive unit; pin 4 of the relay K1 is an output pin, connected to the output terminals J3 and J4, and diodes D4 and D5 are connected in parallel between pins 3 and 4 of the output terminals J3 and J4 respectively. The output terminals are externally connected to two DC contactors that need to be driven, and pins 1 and 2 of the output terminals J3 and J4 are connected in parallel and directly connected to the feedback terminal J2 of the input test.

[0009] Furthermore, the power input unit includes a TVS transient voltage suppressor diode ESD1 and a Schottky diode D1. The positive electrode of diode ESD1 is connected to diode D1 via a magnetic bead FB1. The negative electrode of diode ESD1 is connected to one end of parallel capacitors C1, C2, and C4 via a magnetic bead FB2. The other end of the parallel capacitors C1, C2, and C4 is connected to diode D1. The positive electrode line is connected in series with Schottky diode D1 to prevent reverse polarity of the input. After filtering by capacitors C1, C2, and C4, it is connected to the subsequent circuit.

[0010] Furthermore, the controller is powered by 12V, and the power input is connected to terminal J1, which first passes through the TVS transient voltage suppression diode ESD1 to absorb the instantaneous pulse interference in the line.

[0011] Furthermore, the 3.3V voltage conversion unit includes a chip U1, an inductor L1, a capacitor C5, resistors R1 and R2, the BST pin of the chip U1 is connected to the capacitor C5, the SW pin of the chip U1 is connected to the inductor L1, the FB pin of the chip U1 is connected to the resistor R1 and the resistor R2 respectively, the resistor R1 is grounded, and the resistor R2 and the inductor L1 are connected to the capacitors C8, C9, C10 and C6 in parallel.

[0012] Furthermore, after the 12V input, it is divided and fed back through capacitor C5, DCDC chip U1, resistors R1 and R2, and then filtered by inductor L1, capacitors C8, C9, C10, and C6 to output a 3.3V DC power supply. According to the specific output voltage calculation formula Vout=0.768*(1+R2 / R1), the specific voltage divider resistance value can be calculated.

[0013] Furthermore, the 5V voltage conversion unit includes a linear regulator U2, the VIN end of the linear regulator U2 is connected to the capacitor C11, and the VOUT end of the linear regulator U2 is connected to C12; the 5V voltage conversion unit uses a linear regulator 7805 as a 5V output, and the 12V input outputs 5V after passing through capacitors C11, C12 and linear regulator U2, providing working power input for the timing module.

[0014] Furthermore, the timer unit includes a chip U3, and the 5V power supply is filtered by parallel capacitors C13 and C7 to power U3, and the reset pin 4 is pulled high to start the timing chip; the 5V power supply is connected to pins 2 and 6 of the chip U3 after passing through the series capacitor C3, and then connected in series with a resistor R4 to ground, which is used to control the charging time of C3. Diodes D are connected in parallel on both sides of the resistor R4, and capacitor C15 is used to filter out interference.

[0015] Furthermore, when the 12V power supply is connected and capacitor C3 starts to charge, the voltage levels of pins 2 and 6 of timer U3 are equal to the power supply VCC of chip U3. Since it is greater than 1 / 3 VCC, pin 3 of chip U3 outputs a low level at this time. As capacitor C3 continues to charge, the voltage levels of pins 2 and 6 of chip U3 gradually decrease until the voltage level of pin 2 of chip U3 is lower than 1 / 3 VCC. Then the circuit state is reversed, and pin 3 of chip U3 changes from low level to high level and continues to maintain this state, driving the subsequent circuit. The time for pin 3 of chip U3 to change from low level to high level is determined by the charging time of capacitor C3.

[0016] Furthermore, the power switching drive unit includes resistors R5, R6 and a transistor Q1, the base of the transistor Q1 is connected to the resistors R5 and R6 respectively, the other end of the resistor R5 is connected to the chip U3, and the other end of the resistor R6 is connected to the emitter of the transistor Q1;

[0017] Furthermore, the output of the third pin of the chip U3 of the timer unit drives the transistor Q1 switch through resistors R5 and R6. When the third pin of the chip U3 outputs a low level, Q1 is turned off, and when the third pin outputs a high level, Q1 is turned on, and the operation of the subsequent power switching module is controlled by Q1.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention provides a DC charging pile contactor control system, which is equipped with dual power supplies and an automatic switching power supply circuit. It has a pure hardware design, does not require complex program control, does not occupy the charging pile main control MCU resources, has no interference with other circuits, can effectively reduce the heat generated by the contactor itself, and can control two contactors simultaneously; the present invention also provides a contactor coil surge suppression circuit, which not only improves the overall reliability of the charging pile, but also optimizes the entire pile wiring process, facilitating production and installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Figure 2 It is a schematic diagram of the principle of the present invention.

[0022] Figure 3 FIG. 4 is a circuit diagram of the power input unit of the present invention.

[0023] Figure 4 FIG. 4 is a circuit diagram of a 3.3V voltage conversion unit of the present invention.

[0024] Figure 5 FIG. 4 is a circuit diagram of a 5V voltage conversion unit of the present invention.

[0025] Figure 6 FIG. 4 is a circuit diagram of a timer unit of the present invention.

[0026] Figure 7 Schematic diagram of waveform transition of the timer unit of the present invention.

[0027] Figure 8 FIG. 4 is a circuit diagram of a power switching drive unit according to the present invention.

[0028] Figure 9 FIG. 4 is a circuit diagram of the power switching output unit of the present invention. DETAILED DESCRIPTION

[0029] To better understand the technical solution of the present invention, the following detailed description is provided with reference to the relevant illustrations. It should be understood that the following specific embodiments are not intended to limit the specific implementation of the technical solution of the present invention; they are merely examples of possible implementations of the technical solution of the present invention. It should be noted that references herein to the positional relationships of various components, such as component A being located above component B, are based on the relative positions of the components in the illustrations and are not intended to limit the actual positional relationships of the components. Example 1

[0030] See also Figures 1-9 , Figure 1A schematic structural diagram of the present invention is provided. As shown in the figure, the present invention relates to a DC charging pile contactor control system, which includes a power input unit, a voltage conversion unit, a timer unit, a power switching drive unit, a power switching output unit, and a coil protection unit. The voltage conversion unit includes a 3.3V voltage conversion unit and a 5V voltage conversion unit, and the coil protection unit includes an input protection unit and an output protection unit.

[0031] The power input unit is divided into three paths after being protected by the input protection unit: the first path generates 3.3V through the 3.3V voltage conversion unit as the holding voltage and is connected to the power switching output unit; the second path generates 5V voltage through the 5V voltage conversion unit and is connected to the timer unit to power the timer; the third path is 12V as the rated driving voltage of the contactor and is directly connected to the power switching output unit;

[0032] The timer unit outputs a high level according to the set time, is connected to the power switching output unit through the power switching drive unit, selects the corresponding voltage output, and drives the DC contactor after passing through the output protection unit.

[0033] The power input unit includes a TVS transient voltage suppression diode ESD1 and a Schottky diode D1. The positive pole of the diode ESD1 is connected to the diode D1 through a magnetic bead FB1. The negative pole of the diode ESD1 is connected to one end of the parallel capacitors C1, C2, and C4 through a magnetic bead FB2. The other end of the parallel capacitors C1, C2, and C4 is connected to the diode D1.

[0034] The controller is powered by 12V. The power input is connected to terminal J1. It first passes through the TVS transient voltage suppression diode ESD1 to absorb the instantaneous pulse interference in the line. The positive and negative poles pass through the magnetic beads FB1 and FB2 respectively to suppress high-frequency signals and absorb electrostatic pulses. The positive line is connected in series with a Schottky diode D1 to prevent reverse connection of the input. After being filtered by capacitors C1, C2, and C4, it is connected to the subsequent circuit.

[0035] The 3.3V voltage conversion unit includes a chip U1, an inductor L1, a capacitor C5, and resistors R1 and R2. The BST pin of the chip U1 is connected to the capacitor C5, the SW pin of the chip U1 is connected to the inductor L1, and the FB pin of the chip U1 is connected to the resistors R1 and R2 respectively. The resistor R1 is grounded, and the resistor R2 and the inductor L1 are connected to the capacitors C8, C9, C10 and C6 in parallel.

[0036] Chip U1 uses the TPS563201DDCR, a DC / DC synchronous buck converter with a 4.5V to 17V input voltage and a 3A output current capability, sufficient to maintain the power required for the two DC contactors to remain engaged. The 12V input is divided and fed back through capacitor C5, DCDC chip U1, and resistors R1 and R2. Inductor L1, capacitors C8, C9, C10, and C6 provide energy storage and filtering before outputting a 3.3V DC power supply. The specific output voltage calculation formula (Vout = 0.768*(1+R2 / R1)) allows the specific divider resistor value to be calculated.

[0037] The 5V voltage conversion unit includes a linear regulator U2, the VIN end of the linear regulator U2 is connected to the capacitor C11, and the VOUT end of the linear regulator U2 is connected to C12; the 5V voltage conversion unit uses a linear regulator 7805 as a 5V output, and the 12V input outputs 5V after passing through capacitors C11, C12 and linear regulator U2, providing working power input for the timing module.

[0038] The timer unit includes a chip U3. The 5V power supply is filtered by parallel capacitors C13 and C7 to power U3, and the reset pin 4 is pulled high to start the timing chip. The 5V power supply is connected to pins 2 and 6 of the chip U3 after passing through the series capacitor C3, and then connected in series with a resistor R4 to the ground to control the charging time of C3. Diodes D8 are connected in parallel on both sides of the resistor R4 to quickly discharge the capacitor C3 after the power is cut off to ensure that the charging time of C3 does not change when it is started next time. Capacitor C15 is used to filter out interference.

[0039] Chip U3 uses NA555 timing IC. When the 12V power supply is connected and capacitor C3 starts charging, the voltage level of pins 2 and 6 of timer U3 is equal to the chip U3 power supply VCC. Since it is greater than 1 / 3 VCC, the chip U3 pin 3 outputs a low level. As capacitor C3 continues to charge, the voltage level of pins 2 and 6 of chip U3 gradually decreases until the voltage level of pin 2 of chip U3 is lower than 1 / 3 VCC. The circuit state is reversed, and the chip U3 pin 3 changes from low level to high level and maintains it, driving the subsequent circuit. The time for pin 3 of chip U3 to change from low level to high level is determined by the charging time of capacitor C3. The specific calculation formula is: Tw=1.1*R4*C3. Since the design switching time is 1000ms, the resistor R4 is 100K and the resistor C3 is 10uF. For the specific waveform jump, please refer to Figure 7 .

[0040] The power switching drive unit includes resistors R5, R6 and transistor Q1. The base of transistor Q1 is connected to resistors R5 and R6 respectively. The other end of resistor R5 is connected to chip U3. The other end of resistor R6 is connected to the emitter of transistor Q1.

[0041] The output of the 3rd pin of the chip U3 of the timer unit drives the transistor Q1 switch through resistors R5 and R6. When the 3rd pin of the chip U3 outputs a low level, Q1 is turned off, and when the 3rd pin outputs a high level, Q1 is turned on. The operation of the subsequent power switching module is controlled by Q1.

[0042] The power switching output unit includes a relay K1, diodes D2 to D7, and a resistor R3. Relay K1 uses a dual-channel switching relay HFD23 / 12-1ZS to complete switching. It has two power inputs, 12V and 3.3V. The 12V power supply is connected to pin 5 of relay K1 after passing through diode D3, and the 3.3V power supply is connected to pins 3 and 4 of relay K1 after passing through diode D2. Diode D7 is connected in parallel to pins 1 and 2 of relay K1. One side of resistor R3 is connected to the 12V power supply, and the other side is connected in series to the anode of light-emitting diode D6. The cathode of diode D6 is connected to the collector of transistor Q1 of the power switching drive unit.

[0043] Pin 4 of the relay K1 is the output pin, which is connected to the output terminals J3 and J4. Diodes D4 and D5 are connected in parallel between pins 3 and 4 of the output terminals J3 and J4, respectively. The output terminals are externally connected to the two DC contactors that need to be driven. Pins 1 and 2 of the output terminals J3 and J4 are connected in parallel and then directly connected to the feedback terminal J2 of the input test, which is used to connect the feedback contacts of the two DC contactors and feedback the working status of the contactors.

[0044] Resistor R3 and LED D6 are connected in series to indicate the operating status of relay K1. When LED D6 is on, the relay output is 3.3V, and when LED D6 is off, the relay output is 12V. Diode D7 is used to keep the relay coil freewheeling, preventing reverse electromotive force from being generated after the coil is powered off, which would affect the operation of other components in the circuit. Diodes D2 and D3 are used to prevent backflow between two different power supplies. Relay K1 is used to switch between two different power supply outputs. K1 outputs 12V under normal conditions. After K1 is driven, the 12V output is disconnected and replaced by a continuous 3.3V output.

[0045] Application of this embodiment 1:

[0046] Applied to 100A DC contactor, the coil resistance is 26Ω, 12V power supply generates 461.5mA drive current, coil power consumption is about 5.5W, no-load closure for one hour, at 25℃ ambient temperature, the contactor temperature can reach 70℃, the measured contactor release voltage is below 2.2V, and it can be reliably closed at 2.5V holding voltage. At this time, the drive current is 90mA and the power consumption is 0.225W.

[0047] The DC contactor's closing time is about 30ms, so the time for supplying the contactor coil with the rated drive voltage should be greater than this time. To ensure reliable closing, the rated voltage supply time is preset to 1000ms, after which it is switched to the holding voltage supply. If the input power is disconnected within the rated voltage supply time, the timing will terminate.

[0048] To further ensure reliability in actual use, the holding voltage is finally set to 3.3V. At this time, the measured drive current is 120mA, the power consumption is 0.4W, and the contactor temperature hardly rises after one hour of no-load operation and an ambient temperature of 25°C.

[0049] The above are only specific application examples of the present invention and do not constitute any limitation on the scope of protection of the present invention. Any technical solutions formed by equivalent transformation or equivalent replacement shall fall within the scope of protection of the present invention.

Claims

1. A DC charging pile contactor control system, characterized by: It includes a power input unit, a voltage conversion unit, a timer unit, a power switching drive unit, a power switching output unit and a coil protection unit. The voltage conversion unit includes a 3.3V voltage conversion unit and a 5V voltage conversion unit. The coil protection unit includes an input protection unit and an output protection unit. The power input unit is divided into three paths after being protected by the input protection unit: the first path generates 3.3V through the 3.3V voltage conversion unit as the holding voltage and is connected to the source switching output unit; the second path generates 5V voltage through the 5V voltage conversion unit, which is connected to the timer unit to power the timer; the third path 12V is used as the rated driving voltage of the contactor and is directly connected to the source switching output unit; the timer unit outputs a high level according to the set time, connects to the power switching output unit through the power switching drive unit, selects the corresponding voltage output, and drives the DC contactor after passing through the output protection unit; The power switching output unit includes a relay K1, diodes D2~D7 and a resistor R3, and has two power inputs of 12V and 3.3V. The 12V power supply is connected to pin 5 of the relay K1 after passing through the diode D3, and the 3.3V power supply is connected to pins 3 and 4 of the relay K1 after passing through the diode D2; a diode D7 is connected in parallel to pins 1 and 2 of the relay K1; one side of the resistor R3 is connected to the 12V power supply, and the other side is connected in series with the anode of the light-emitting diode D6, and the cathode of the diode D6 is connected to the power switching drive unit; pin 4 of the relay K1 is an output pin, connected to the output terminals J3 and J4, and diodes D4 and D5 are connected in parallel between pins 3 and 4 of the output terminals J3 and J4 respectively. The output terminals are externally connected to two DC contactors that need to be driven, and pins 1 and 2 of the output terminals J3 and J4 are connected in parallel and directly connected to the feedback terminal J2 of the input test.

2. A DC charging pile contactor control system according to claim 1, characterized in that: The power input unit includes a TVS transient voltage suppression diode ESD1 and a Schottky diode D1. The positive pole of the diode ESD1 is connected to the diode D1 through a magnetic bead FB1, and the negative pole of the diode ESD1 is connected to one end of the parallel capacitors C1, C2, and C4 through a magnetic bead FB2. The other end of the parallel capacitors C1, C2, and C4 is connected to the diode D1; the positive pole line is connected in series with the Schottky diode D1 for input reverse connection protection, and is connected to the subsequent circuit after filtering by the capacitors C1, C2, and C4.

3. A DC charging pile contactor control system according to claim 2, characterized in that: The controller is powered by 12V. The power input is connected to terminal J1 and first passes through the TVS transient voltage suppression diode ESD1 to absorb the transient pulse interference in the line.

4. A DC charging pile contactor control system according to claim 1, characterized in that: The 3.3V voltage conversion unit includes a chip U1, an inductor L1, a capacitor C5, and resistors R1 and R2. The BST pin of the chip U1 is connected to the capacitor C5, the SW pin of the chip U1 is connected to the inductor L1, and the FB pin of the chip U1 is connected to the resistors R1 and R2 respectively. The resistor R1 is grounded, and the resistor R2 and the inductor L1 are connected to the capacitors C8, C9, C10 and C6 in parallel.

5. A DC charging pile contactor control system according to claim 4, characterized in that: After 12V input, it is divided and fed back by capacitor C5, DCDC chip U1, resistors R1 and R2, and then output after energy storage and filtering by inductor L1, capacitors C8, C9, C10 and C6. For a 3.3V DC power supply, the specific voltage divider resistor value can be calculated based on the specific output voltage calculation formula Vout=0.768*(1+R2 / R1).

6. A DC charging pile contactor control system according to claim 1, characterized in that: The 5V voltage conversion unit includes a linear regulator U2, the VIN end of the linear regulator U2 is connected to the capacitor C11, and the VOUT end of the linear regulator U2 is connected to C12; the 5V voltage conversion unit uses a linear regulator 7805 as a 5V output, and the 12V input outputs 5V after passing through capacitors C11, C12 and linear regulator U2, providing working power input for the timing module.

7. A DC charging pile contactor control system according to claim 1, characterized in that: The timer unit includes a chip U3. The 5V power supply is filtered by parallel capacitors C13 and C7 to power U3, and the reset pin 4 is pulled high to start the timing chip. The 5V power supply is connected to pins 2 and 6 of the chip U3 after passing through the series capacitor C3, and then connected in series with resistor R4 to ground to control the charging time of C3. Diodes D are connected in parallel on both sides of the resistor R4, and capacitor C15 is used to filter out interference.

8. A DC charging pile contactor control system according to claim 7, characterized in that: When the 12V power supply is connected and capacitor C3 starts to charge, the voltage levels at pins 2 and 6 of timer U3 are equal to the power supply VCC of chip U3. Since it is greater than 1 / 3 VCC, pin 3 of chip U3 outputs a low level at this time. As capacitor C3 continues to charge, the voltage levels at pins 2 and 6 of chip U3 gradually decrease until the voltage level at pin 2 of chip U3 is lower than 1 / 3 VCC. Then the circuit state is reversed, and pin 3 of chip U3 changes from a low level to a high level, and continues to maintain this state to drive the subsequent circuit. The time for pin 3 of chip U3 to change from a low level to a high level is determined by the charging time of capacitor C3.

9. A DC charging pile contactor control system according to claim 1, characterized in that: The power switching drive unit includes resistors R5, R6 and transistor Q1. The base of transistor Q1 is connected to resistors R5 and R6 respectively. The other end of resistor R5 is connected to chip U3. The other end of resistor R6 is connected to the emitter of transistor Q1.

10. A DC charging pile contactor control system according to claim 9, characterized in that: The output of the chip U3 of the timer unit at the third pin drives the transistor Q1 switch through resistors R5 and R6. When the chip U3 outputs a low level at the third pin, Q1 is turned off, and when the chip U3 outputs a high level, Q1 is turned on. The operation of the subsequent power switching module is controlled by Q1.

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