ZL2008 digital power supply provides multiple configurations and application flexibility

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The ZL2008 is the latest generation of digital DC-DC power controllers that use InterSIL Zilker Labs' pinout technology to configure power conversion and power management parameters.

Traditional analog power supplies are perfect in terms of topology, devices, efficiency, and functions. They are also widely used, and a large number of engineering and technical personnel are familiar with and are designing and using analog power supplies. But the biggest drawback of analog power is the lack of flexibility, and it takes a lot of time to redesign, verify, and test as the application's needs change.

The digital power supply can digitally set the parameters of the power system to achieve one design, repeated use, and easy expansion. Intersil Zilker Labs' ZL2008 is the latest generation of digital DC-DC power controllers that use Intersil Zilker Labs' pin-setting technology to configure power conversion and power management parameters while telemetry and monitoring via the PMBus interface, compensation, current distribution and Operating parameters such as output voltage can be configured via pins. ZL2008 can build a DC power supply by means of building blocks, using a 3.3V single-phase power supply to a 12V input multi-phase power supply.

Figure 1 Functional block diagram of ZL2008

Design features: Adaptive control algorithm

Current embedded power systems are typically optimized for efficiency at maximum load, reducing peak thermal stress by limiting the overall heat dissipation within the system. Unfortunately, most systems typically operate at well below peak conditions, and the power system is optimized for peak load conditions, so the best conversion efficiency is usually not achieved. Although this does not generate thermal stress, it consumes more power, which in turn leads to higher overall system operating costs.

According to Chris Young, senior manager of digital power technology at Intersil Zilker Labs, the ZL2008 DC-DC uses adaptive control algorithms that allow the power converter to automatically change operating conditions, always working at the optimum efficiency point, improving efficiency and overall performance. Only with little or no user intervention.

Figure 2 Typical application circuit of ZL2008

The ZL2008's PWM loop uses an analog and digital hybrid module that provides precise control over the entire process of power conversion without the need for any software. The ZL2008 integrates a variety of power management features that can be configured with simple pin connections. User configuration can be stored in internal non-volatile memory (NVM). In addition, all functions can be configured and monitored via the SMBus hardware interface using standard PMBus commands. See Figure 1 for the function of ZL2008.

Functional combination improves power conversion efficiency

The ZL2008 is a voltage mode synchronous buck converter with optional constant frequency PWM control combined with external MOSFETs, capacitors and inductors to form a complete power converter.

In its simplest configuration, the ZL2008 requires two N-channel power MOSFETs, one for the upper control MOSFET and one for the lower synchronous MOSFET (QL). The on-time of QH is proportional to the total switching period, which is called the duty ratio D and is expressed by the following equation.

During time D, QH turns on and VIN-VOUT is applied to the inductor. When QH is turned off, the current in the inductor must continue to flow from ground to QL, during which time the current drops at a certain slope. Since the impedance of the output capacitor COUT at this switching frequency is low, the AC component of the inductor current is filtered out of the output voltage, so the load sees almost DC voltage.

In general, the buck converter scales a maximum duty cycle to limit the maximum output voltage at a given input voltage. This duty cycle limit guarantees the shortest turn-on time of the low-side MOSFET during each switching cycle. This allows the startup capacitor to be charged to provide sufficient gate drive voltage for the high-side MOSFET.

In this circuit, the target output voltage is regulated by directly connecting the differential VSEN pin to the output regulation point. The VSEN signal is then compared to the reference voltage and the user sets the reference voltage to the desired output voltage level. The error signal generated after the comparison is converted into a digital value and converted by a low resolution analog to digital converter. The digital signal is then sent to an adjustable digital compensation filter that is used to generate the appropriate PWM duty cycle to drive the external MOSFET to produce the desired output.

ZL2008 has several features that can improve power conversion efficiency. The nonlinear response (NLR) loop improves response time and reduces output skew. The ZL2008 monitors the operating conditions of the power converter and continuously adjusts the turn-on and turn-off times of the high-side and low-side MOSFETs to optimize the overall efficiency of the power supply. Adaptive performance optimization algorithms such as dead time control, diode simulation, and frequency control provide better efficiency improvements.

A typical application circuit is shown in Figure 2. As you can see from this schematic, on the power transfer chain, only a few components are required to implement a fully functional, fully configurable power supply with digital power conversion, power management, fault management and telemetry.

to sum up

ZL2008 includes advanced energy-saving algorithms that continuously adjust the power supply to minimize losses. Embedded controllers use these algorithms to adjust various operating parameters (dead time, switching frequency, low-side FET on-time, etc.) in real time to optimize efficiency. In this way, ZL2008 can adapt to the effects of production changes, temperature changes, load changes, input voltage changes, temperature changes and component aging to provide the highest performance. The device also integrates power conversion control, power management, fault management and telemetry to save dozens of components and significantly reduce material costs. Another benefit that comes with it is that it speeds up development and reduces manufacturing time.