New grid drive series KP8530X for high reliability motor drive.

Modern power electronics applications are based on the conversion technology of power devices, and all power devices require suitable gate drive solutions. As a bridge between the power device and the microcontroller, the gate driver receives the control signal from the microcontroller (MCU/DSP) to provide the current required to drive the gate capacitor of the power device, thus achieving a variety of power electronics applications.

Focusing on high-power motors and power applications, BYI Micro has launched a new grid driver KP8530X series, a total of 3 models in this series, the switching node voltage is 650V, the output peak pull current and current filling capacity are 300mA and 600mA, while these three models integrate the boot diode, The peripheral system is more streamlined.

Household appliance combination

Table 1: KP8530X control logic

Figure 1: KP85302 typical application circuit

For high-power applications, reliability is the primary consideration for customer device selection. For gate drivers, reliability is measured in two aspects, the negative pressure capacity of the switching node and the level of the transient voltage change rate of the switching node.

Highlight 1: Switch node negative pressure capability

In the application of half-bridge topology, inductive load is usually used, and because of the parasitic inductance of the power device itself and the parasitic inductance of the power loop, when the high-side power tube is turned off, the continuous current loop will generate negative pressure at the switching node. The negative pressure consists of a large dynamic peak negative pressure and a lower static negative pressure, as shown in the figure 2 is shown.

Figure 2: Switching current path and VS voltage

When the negative pressure of the switch node is greater, the pressure of the internal device of the gate driver chip is higher, and it is easier to breakdown failure. At the same time, the negative pressure of the switch node is larger, resulting in HB of the high-side power supply node of the gate driver chip.The lower the transient voltage, the more reliable control of input and output is affected. Therefore, higher negative pressure bearing capacity of switching nodes can bring greater reliability to power system operation.

The switch node negative pressure capability test waveform of the KP8530X series is as follows:

Figure 3: KP8530X switch node negative pressure test waveform

When the VDD supply voltage is 15V and the input HIN control signal is 20K switching frequency, the input signal HIN can still reliably control the output signal HO when the negative pressure of the switch node is pulled to -13.9V. Under the same test conditions, the comprehensive comparative test of several similar products on the market, BYI Micro KP8530X Series, the negative pressure bearing capacity is equivalent to that of international brands, with obvious advantages.

Highlight 2: High dv/dt noise suppression capability of the switching node

The high side drive circuit of the high voltage gate driver mostly adopts the bootstrap circuit structure, and the low voltage logic control signal can be transmitted to the high side by the level shift circuit inside the gate driver. Because the high-side control driver circuit refers to the switch node, in the high-speed switching state, the parasitic current inside the chip will be transferred to the low-voltage side through the coupling path, and when there is a mismatch inside the chip, the differential mode interference signal will be generated, thus affecting the correct input and output logic.

KP8530X series adopts the unique level shift and common mode noise suppression technology, which can effectively suppress the common mode noise interference of the product during the high-speed switching process of the switch node, prevent false triggering, so as to ensure the normal and reliable operation of the system.

According to the measured data, the dV/dt capability of the KP8530X gate driver can guarantee the capability of up to 50V/nS, and has a large reliability margin.

Figure 4: Output switch node dV/dt change (66V/nS)

In addition, the KP8530X gate driver family integrates a high-voltage bootstrap diode, a bootstrap diode with ultra-fast recovery characteristics to provide a high-side bootstrap capacitor charge path, and an integrated resistor to limit the surge current of the bootstrap capacitor at the moment of charging.

Figure 5: Integrated bootstrap diode

In the half-bridge application topology, as shown in Figure 6, the driver input signal peak voltage and ringing caused by the power ground oscillation current is a common problem. When the ringing is too large, the logical identification of the input control signal will be wrong. In order to solve this problem, KP8530X series has built-in Schmidt filter circuit. It can effectively improve the anti-interference ability of input pins. At the same time in logic control, when the input float or input pulse width is insufficient, the output can be kept low to prevent HO and LO.

The output responds to a narrow pulse width or ringing, causing the power device to turn on or off unexpectedly.

Figure 6: Input signal peaking and ringing

Figure 7: Input signal negative pressure tolerance test (-5V)

At the same time, the KP8530X series features an upside-down undervoltage lock (UVLO) feature that ensures that the peripheral power device driven by the half-bridge gate driver has enough gate voltage to fully turn on the power device. KP8530X

The series integrates internal interlocking and dead zone protection functions, which automatically insert dead zones when the output state changes, ensuring that the other side of the gate driver is completely turned off before the high and low side is opened, preventing the occurrence of high and low sides of the common situation.

Sum up

The new KP8530X series is a highly reliable, highly integrated set of highly reliable gate drives that meet the reliability needs of most consumer, appliance and industrial applications.