introduction：
Olink IC-CPD EV charger bring EV owner safety in charging With more and more EVs rush into the market, the demands on IC-CPD ev charging station increasing rapidly.
What is IC-CPD EVSE? Below picture shows
Mode2 and Mode 3 ev charger IC-CPD elements graph 1
1.1 Mode 2/mode 3 EVSE includes:
power plug to insert into the socket for power-in sources; EV charger plug to plug in the vehicle inlet, cable, and function/protection box;Power supply cord：Usually it is same as the home appliance plug In China, it is with 10A/16A 220V two kind of spec. In some case, in order to make it safer, Thermal sensor may be embedded in the plug.Charging plug: it could be NACS, TYPE 2, J1772, or GB/T
The cables in IC-CPD are mainly divided into two parts:
The first part is the cable between the plug and the control protection box, as shown in Part A of Figure 1, with a length generally ranging from 20cm to 1m. Item 8.1 of NB/T42077-2016 specifies the maximum allowable length of the cable between the plug and the IC-CPD as 1.7m.
The second part is the cable between the control protection box and the vehicle connector, as shown in Part B of Figure 1, with a length generally ranging from 3 to 4m.
The standard does not explicitly specify the length of this part. Currently, the IC-CPD cables with a rating of 16A available on the market mainly come in lengths of 5m, 10m, and 15m. They are mostly made of high-quality pure copper cable, with a wire diameter of 0.75mm² for the A side and 2.5mm² for the B side. They should have advantages such as flame retardancy, impact resistance, waterproofness, and high-temperature resistance.
1.2 The main electronic components on the IC-CPD include
relays, MCUs, leakage current protection devices, current transformers, voltage transformers, etc. Below, I will introduce their main functions inside the IC-CPD one by one.
Picture 2：IC-CPD PCBA
2.Brief about IC-CPD PCBA components
2.1 Relay
Relays in IC-CPD mainly serve the switch control function for charging, boasting strong driving capability. The contact part should have an arc extinguishing circuit, and the discharge circuit of the driving coil part should have dual protection to increase reliability and prolong lifespan.
Internally, relays are generally divided into two parts: contacts and coils. The nameplate of the relay will specify the rated current, voltage of the contacts, and the rated voltage of the coil. However, the main parameter referenced on the IC-CPD’s board is the withstand voltage value of the relay. The voltage condition for withstand voltage testing in the IC-CPD testing standard is 2KV. Additionally, for European CE certification, the spacing between relay contacts needs to be greater than 3mm.Currently, major relay manufacturers in China include Hongfa, Saiter, Songle, etc., while internationally renowned relay manufacturers include Omron, Schneider, Panasonic, Tyco, ABB, etc.
2.2Chip
Recently, the chip industry has been booming, and the country is vigorously supporting the development of “Chinese chips.” With the iteration of chip technology and the strategic shift from silicon to copper, more integrated chip technologies are being used to replace copper process products. This not only saves resources but also increases the integration and intelligence of products. Let’s briefly introduce some related knowledge about chips.
An integrated circuit (IC) is a layout of active and passive electronic components interconnected in a circuit. It is fabricated on a semiconductor substrate through semiconductor processes or thin/thick film processes, forming a compact and multifunctional circuit. Compared to circuits composed of discrete components, ICs have characteristics such as small size, light weight, high integration, low power consumption, convenience of use, and low cost.
Chips can be classified into many types. Based on signal processing, they can be divided into analog chips and digital chips. Components like ADCs (Analog-to-Digital Converters), operational amplifier chips, and switch power supply ICs used in on-board chargers (IC-CPDs) belong to analog chips, which are mainly used to generate, amplify, and process various analog signals.
Digital chips are mostly used for logical operations, such as CPUs, memory chips, DSP chips, etc. Classified by different application scenarios, chips can be categorized as consumer-grade, industrial-grade, automotive-grade, military-grade, and aerospace-grade. The chips used in on-board chargers (IC-CPDs) need to meet industrial-grade requirements, with temperature requirements ranging from -40°C to 85°C during operation.
Logic chips (data processors) can be divided into single-core, dual-core, and multi-core. Taking ARM products as an example: ARM’s Cortex series is divided into A, R, and M series. The A series is mainly used for complex computer applications (such as computers, TVs, smartphones, etc.), the R series is mainly used in scenarios requiring real-time responses (such as autonomous driving), and the M series is mainly used in embedded devices, small sensors, and smart home products. In embedded development, the series mostly used is ARM Cortex-M.
The Cortex-M system is mainly divided into Cortex-M0, Cortex-M0+, Cortex-M1, Cortex-M3, Cortex-M4, Cortex-M7, Cortex-M23, Cortex-M33, and other series.
Picture 3：Cortex-M application
Picture 4：SKY stars graph of chip core
Simply put, the M0 series operates at a frequency of 48MHz and belongs to the entry-level basic version. The M3 series operates at a frequency of 72MHz and is chosen as the mainstream design core due to its wide application. The M4 series operates at a frequency of 168MHz, incorporating DSP processing for superior performance, and is commonly used in embedded audio applications. In on-board chargers (IC-CPDs), the requirements for chips are mainly simple functionality control, with no need for overly complex logic, and the overall cost should be kept as low as possible. Choosing a Cortex-M0 core can meet the requirements of IC-CPDs.
Currently, the types of chips used in on-board chargers (IC-CPDs) mainly include three categories: switch power control ICs, precision operational amplifier ICs, and microcontroller ICs.
2.2.1Introduction to operational amplifier chips
The main function of operational amplifier ICs is to compute and process the CP signal in on-board chargers (IC-CPDs), ensuring that the CP signal varies within the range specified by national standards. This is achieved by adjusting different charging states through changes in CP voltage values.
picture 5：GB/18487 define on out-put Volt. parameters
The operational amplifier IC has three ports: two input ports, labeled as “+” and “-“, and one output port. When the input signal is applied to the “-” port of the amplifier, the output signal at the output port is inverted relative to the input signal. Conversely, when the input signal is applied to the “+” port of the amplifier, the output signal at the output port is in phase with the input signal. When signals are simultaneously applied to both input ports, the operational amplifier performs subtraction, and the output signal is in phase with the larger of the two input signals. Therefore, the operational amplifier can be essentially considered as a voltage amplifier. An ideal operational amplifier must possess the following characteristics: infinite input impedance, zero output impedance, infinite open-loop gain, infinite common-mode rejection ratio, and infinite bandwidth.
Picture 6: Amplifier circuit
The output formula for the non-inverting operational amplifier circuit is: VO = VI × (1 + R2/R1)
The output formula for the inverting operational amplifier circuit is: VO = -VI × (R2/R1)
Selection of operational amplifier ICs mainly considers: input type, precision requirements, environmental conditions, number of channels, single or dual power supply, power rating, packaging, etc. For on-board chargers (IC-CPDs), the precision requirement for operational amplifiers is not high, and power consumption generally needs to be around 5W.Currently, mainstream brands of operational amplifier ICs include: ADI, Maxim, TI, NXP, ON, etc. In China, there are: Runshi Technology, Ruimeng Technology, Enraytek 3PEAK, etc. Foreign operational amplifier ICs generally have higher prices and longer lead times, but superior performance. Domestic manufacturers’ operational amplifier ICs are generally cheaper with relatively shorter lead times.
2.2.2Switching power supply chip introduction
The main function of switch power control ICs is to provide the required power supply to various modules. In on-board chargers (IC-CPDs), they are primarily used to supply the necessary voltage signals to relays, chips, and operational amplifier ICs. Switch power supplies are generally divided into two types: AC-DC and DC-DC. AC/DC switch power supplies are mainly categorized into non-isolated circuits and isolated circuits. In on-board chargers (IC-CPDs), isolated (flyback) switch power supply circuits are mainly used for AC-DC conversion, while DC buck regulation is mostly handled by LDO (Low-Dropout) modules.
2 kind of circuit on switch power
In switch power supply applications, power supplies below 400W account for approximately 70-80% of the market, with flyback power supplies comprising the majority. Virtually all common consumer products utilize flyback power supplies due to their advantages: low cost, fewer peripheral components, low energy consumption, suitability for wide voltage range inputs, and capability for multiple outputs. However, they have the disadvantage of relatively large output ripple. (Adding low impedance filtering capacitors or LC noise filters can improve this.)
Currently, well-known switch power control IC manufacturers in China include Xinpeng Microelectronics with their PN8 series, Shilanwei with their SDH series, and Huaguan with their UC series. Overseas, there are companies like Power Integrations and MPS. Generally speaking, domestic chips offer better cost-effectiveness with no issues regarding lead times, while foreign chips are expensive and may have longer lead times.
2.2.3 SCM IC Introduction
The main functions of microcontroller ICs are as follows:
- They serve as the central processing unit for the operational logic and computation of functions in charging guns.
- They act as the command center for communication and coordination, facilitating interaction among various IC modules.
- They integrate interfaces such as memory, serial ports, counters, A/D converters, DMA, etc.
- They calculate voltage and current, generate drive signals for devices such as relays and LED lights.
Microcontroller ICs control the charging process of on-board chargers (IC-CPDs) as follows:
The relay is normally in an open state, and the charging gun is not energized when plugged into the socket to prevent electric shock to charging personnel. When the charging gun is connected to the electric vehicle and the CP signal is established, the system detects the charging conditions. The MCU on the board then controls the relay to close, establishing the charging circuit. When charging is complete, manually terminated, or if a leakage occurs, the MCU controls the relay to disconnect immediately.
After meeting the charging conditions, the control guidance module continuously sends PWM signals to the on-board charger (OBC) of the vehicle, informing it of the maximum charging current of ICCPD. The vehicle then determines the charging current to be used.
Currently, most mainstream microcontroller ICs are developed by foreign companies such as ST, TI, NXP, ADI, Infineon, etc. Domestic customers usually buy them at high prices and may face issues such as long lead times and shortages. The country is now promoting “Made in China” chips, vigorously supporting many domestic chip companies to accelerate domestic chip development. Many excellent chip companies have emerged domestically.
2.3 Current/voltage sampling device - Transformer
Current/voltage transformers on the IC-CPD board primarily serve the function of current/voltage (power) sampling. In the circuit, excessive voltage can damage the switch power supply, while excessive current can lead to relay damage. The principles of voltage and current transformers utilize electromagnetic induction to convert high voltage into low voltage and large current into small current. This allows secondary devices (such as relays) to be miniaturized, protecting the circuit and keeping operators away from high voltage to ensure personal safety.
The main parameters of voltage and current transformers include rated voltage, primary current, secondary current, rated capacity, current/voltage ratio, etc. These specifications are usually indicated on the nameplate and in the datasheets, enabling the selection of suitable voltage and current transformers based on the actual circuit application.
Currently, well-known transformer manufacturers in China include Zhenhengtong, Zeming, and Nanjing Xiangshang Electronics.
2.4 Leakage current sensor
（1）Standard interpretation of leakage protection requirements
GB/T18487.1 stipulates that AC charging mode should have A device that meets the residual protection function of type B or type A, the current national standard has not mandatory requirements for the use of type B residual current protection device, but the future domestic IC-CPD leakage protection requirements will definitely be more and more stringent.
Picture 7：GB/T18487.1-2015 on residual current protect A type and B type
European Standard IEC61851-1: The requirements of IC-CPD are specified in the 2017 standard, requiring the residual current protection in AC charging equipment to use type B or type A +6mA smooth DC RCD, IEC62752-2018 on the on-board charging gun (IC-CPD) charging gun standard is also mentioned, Residual current protection is required to be able to detect a smooth DC of 6mA. Compared with the requirements of the national standard, the European standard is a higher requirement.
Picture 8： IEC 61851.1-2010 6.5 requirement on residual currents
（2）Types and causes of leakage current of IC-CPD and electric vehicle charging
Picture 9：Current leak logic
A simple description of the principle of detecting residual current: there are three water pipes A, B, C inside the water flow into the water pipe N. Under normal circumstances, when the pipe does not leak, the amount of water A+B+C=N, considering the direction of water flow, A+B+C-N=0. The dashed box of the ellipse in the figure is the element used to detect whether A+B+C-N is equal to 0. In the case of no water leakage, the product detects leakage flow equals 0.
If in some situation, one of the pipes breaks and leaks, like the picture above, some of the water goes to the earth (in electrical, we call it a ground fault). At this time, the components of the dotted box detect that A+B+C-N is not equal to 0, and then the monitoring system knows that there is water leakage. When the amount of leakage reaches a certain value, the monitoring system will issue an alarm.
In electrical systems, leakage refers to the phase line directly to the ground or to the N line leakage, rather than the N line to the ground leakage, only the phase line to the PE line leakage, will cause the N line current and the three-phase imbalance current in the value is not equal.
For the application scenario of IC-CPD charging electric vehicles, the internal power supply topology is relatively complex, and the battery of electric vehicles is a DC power supply system, so the current composition is relatively complex, including AC current and pulsating DC component, especially DC current will appear in this special application scenario. Based on this, The type of leakage current in the charging process of electric vehicles is also more complex.
Figure 10 shows the charging system of the on-board charging gun (IC-CPD) when charging the charging gun and the vehicle, the parts that may have leakage include: the charging gun line interface and the vehicle interior. The leakage current occurring at the front end of the vehicle charger (blue part) is AC sine, and the leakage occurring at the rear end of the vehicle charger (light orange) contains the DC residual current.
The areas that may generate leakage current in the figure below are divided into four parts a, b, c, and d.
Type of leakage current at point a: The AC leakage generated between the AC current in the charging gun head and the PE ground.
Type of leakage current at point b: pulsating DC leakage generated between the current at the front end of the vehicle charger and the PE ground.
Type of leakage current at point c: DC leakage generated between the DC current after rectification on the vehicle charger and the PE ground.
Type of leakage current at point d: non-power frequency leakage generated between the primary side of the high frequency isolation transformer and the PE ground.
Picture 10：power leakage while EV in charging
As shown in Figure 11 below, the blue box in the figure indicates that the leakage current of Type B leakage protection detection ranges from the leakage protection magnetic ring to the primary side of the high-frequency isolation transformer of the vehicle charger. Possible leakage currents include: AC current, pulsating DC current, smooth DC current, high frequency current.
The yellow box in Figure 18 indicates the protection range of Type A leakage protection, which is smaller than that of Type B. Type A can only protect the leakage of AC, pulsed DC, pulsed DC superposition 6mA smooth DC.
Picture 11：Different leakage protector function range
Olink using MAGTRON company launched products to meet the latest requirements of IC-CPD leakage current detection. This series of products is B-type leakage current sensor. Based on the iFluxgate chip independently developed by MAGTRON, it outputs trip signals and can detect different leakage components. It can fully meet the leakage protection requirements of IEC62752, and the product can fully cover the application scenarios of 3.3kW, 7kW single-phase IC-CPD and 22kW three-phase IC-CPD, which is more reliable, more sensitive and safer than the traditional leakage current sensor.
