“Nowadays, with the continuous improvement of energy saving and environmental protection requirements, there are further requirements for power standby power consumption. The latest CapZero 3 series products from Power Integration (PI) can reduce the power consumption related to the discharge resistance of the X capacitor in the switching power supply, so that the standby power consumption can meet the safety requirements.
“
Nowadays, with the continuous improvement of energy saving and environmental protection requirements, there are further requirements for power standby power consumption. The latest CapZero 3 series products from Power Integration (PI) can reduce the power consumption related to the discharge resistance of the X capacitor in the switching power supply, so that the standby power consumption can meet the safety requirements.
What is an X capacitor
The X capacitor is connected across the two lines of the power line, that is, between “LN”. The X capacitor can suppress the differential mode interference. Usually, a metallized film capacitor is used, and the capacitance capacity is uF level. Most X capacitors are square, which is similar to the shape of a box, and are generally marked with safety certification marks, withstand voltage words (usually AC300V or AC275V), and rely on standards on their surface.
X safety capacitor applications include the following three aspects
1. Suppression of Electromagnetic Interference
Anti-electromagnetic interference is the most common function of X capacitors. Generally, the two pins are connected between the neutral wire and the live wire. They are suitable for high frequency, DC, AC, coupling, and pulse circuits. They can withstand overvoltage shocks. Generally used in parallel with the resistor, the purpose is to discharge the charge;
2. Resistance-capacitance step-down
Resistance-capacitance step-down is also often used by X capacitors, especially for low-cost finished products. The working principle of capacitor step-down is to use the capacitive reactance generated by the capacitor at a certain AC signal frequency to limit the maximum operating current. At the same time, if a resistive element is connected in series with the capacitor, the voltage obtained at both ends of the resistive element and the power consumption it produces depend entirely on the characteristics of the resistive element. Therefore, the capacitor buck actually uses the capacitive reactance to limit the current, and the capacitor actually plays a role of limiting the current and dynamically distributing the voltage across the capacitor and the load.As shown below
3. Filtering
X2 safety capacitors can be used for DC filtering and can be used in parallel.
The X capacitor is a safety capacitor, which means that the capacitor must not cause harm to the human body. Therefore, the safety standard stipulates that when the power cord of the working machine is unplugged, the energy storage of the X capacitor should drop below 34V DC within one second.
Nowadays, with the continuous improvement of equipment power, whether it is EMI requirements or filtering requirements, larger-capacity X capacitors are required, ranging from 100 nF for small appliances to 6 µF for washing machines. However, in order to meet the requirements of fast energy dissipation, the discharge resistance required for discharging the X capacitor needs to decrease with the increase of the X capacitor. A huge problem came.
To meet new challenges, CAPZero upgrades
A few days ago, in order to reduce the power consumption of X capacitor discharge, PI specially developed a series of products called CAPZero3. CAPZero, as the name suggests, is a technology that reduces the “capacitive influence to zero”. PI senior technical training manager JASON YAN said that CAPZero can be regarded as a smart switch, which is only activated when the AC voltage is disconnected. A discharge circuit is provided for the filter capacitors so that minimal standby power consumption can be achieved. CAPZero adopts a self-powered working mode, and the power consumption is less than 4mW, which is far lower than the standby power consumption of the discharge resistor. Yan Jinguang said that for some large-sized X capacitors, the corresponding resistance standby power consumption may even exceed 1W.
How CAPZero works
The X capacitor and the corresponding standby power consumption, it can be seen that the larger the X capacitor capacity is, the higher the standby power consumption, and the two are linearly related.
Yan Jinguang pointed out that it is already the third generation of CAPZero products. Compared with the previous generation products, it supports lower total series resistance, that is, supports larger X capacitors.
In addition to this, the CAPZero-3 IC can be placed either before or after the system input fuse. The new devices have high common-mode surge immunity, eliminating the need for an external ground connection, and with an integrated 1000 V MOSFET, they also feature high differential-mode surge immunity. The creepage distance between the package and the PCB is kept below 4 mm.
According to Yan Jinguang, CAPZero’s products are fully pin-compatible, so if there are specifications that CAPZero-2 cannot meet, you can directly replace them with CAPZero-3. At the same time, this product meets IEC60335, IEC62368 and other safety standards. CAPZero-3 devices are certified to meet CB and Nemko safety requirements, so developers do not need to perform separate safety testing of the power supply’s X-capacitor discharge circuit.
Review SENZero Products
SENZero is not a new device from PI, but the product was also developed to reduce standby power consumption. SENZero disconnects the sense resistor connected to the high-voltage bus during the presence of AC power, thereby eliminating the power dissipation from the sense resistor, which in turn helps reduce overall system power consumption and helps meet the requirements of energy-conscious product manufacturers and energy-efficiency standards regulators strict requirements.
On the power factor correction (PFC) circuit of the power supply and/or in the power conversion stage, SENZero devices can disconnect the high voltage sense resistor or resistor divider from the DC high voltage bus in no-load or standby mode to achieve reduced purpose of power consumption. This shuts down or disables functional blocks in the power supply, saving unnecessary power consumption when the power supply is not fully operational.
Whether it is CAPZero or SENZero, the principle is to realize the switch control of key devices through IC, so as to achieve more stringent standby power consumption. This is also the development direction of PI, which reduces power consumption and simplifies circuit design.
The Links: LM64P51 EW162C1YMY
