Digital Controller for Power Supply with PMBus Interface

Applications such as industrial and automotive are accelerating the transition to 48 V power supply systems, driven by the significant advantages of 48 V architecture in efficiency, power density, and system performance. Compared to traditional 12 V power supply systems, the 48 V architecture can significantly reduce current at the same power level, thereby minimizing energy loss in wiring and allowing the use of thinner, lighter conductors, which lowers system costs and weight. Additionally, the 48 V architecture provides stronger power support for high-power-demand devices, meeting the needs of modern industrial equipment for high performance and complex functionalities.

Recently, Hynetek launched its first multifunctional DC-DC digital power controller—the HP1000. Designed for high-density, high-efficiency DC-DC power conversion, it features an interface compliant with the PMBus™ 1.2 standard. This device offers advanced power control solutions, primarily targeting isolated and non-isolated DC-DC secondary-side applications with typical 48 V inputs. It covers closed-loop isolated topologies (such as full-bridge converters, half-bridge converters, active-clamp forward converters, push-pull converters, etc.), open-loop isolated topologies (such as open-loop LLC converters and intermediate bus converters (IBC)), multi-phase interleaved buck converters, and hybrid switched-capacitor converters.

Driven by the explosive growth of AI servers and robotics, the 48 V power architecture is becoming the inevitable choice for high-power-density scenarios. By quadrupling the voltage, the current is sharply reduced to one-fourth of its original level, significantly lowering transmission losses and fundamentally overcoming the bottlenecks of transmission loss and heat dissipation, achieving a leap in energy efficiency. With the HP1000 digital power controller, new topology technologies (such as hybrid switched-capacitor architectures) deeply integrate capacitive energy storage with high-frequency switching characteristics, achieving dual breakthroughs in efficiency and power density in ultra-high step-down ratio scenarios. Additionally, using the HP1000 to control gallium nitride (GaN)-based multi-phase interleaved converters enables smaller size and higher efficiency.

The HP1000 boasts extensive programmability, including an integrated high-performance digital compensator, support for fast input voltage feedforward, multiple PWM output types and timing configurations, constant current mode, and soft start/stop sequences with synchronization. Furthermore, it offers flexible protection features, including over-voltage protection (OVP), short-circuit protection (SCP), reverse current protection (RCP), and over-temperature protection (OTP), all aimed at creating reliable power management solutions.

The HP1000 features an intuitive user-programmable interface, eliminating the need for engineers to have software expertise. Hardware engineers can directly monitor various power states and flexibly modify power configurations (including loops) to quickly identify issues and optimize performance. The graphical interface configuration significantly accelerates product development.

The HP1000 is widely applicable to scenarios such as isolated or non-isolated DC-DC brick module power supplies, intermediate bus converters, communication power supplies, and industrial intelligent power systems. The HP1000 is available in a 4mm x 4mm QFN-24L package.

Figure 1: HP1000 QFN-24L Package and Pinout Diagram

FEATURES

• Versatile Digital Voltage Mode Controller

• −40°C to +125°C Operating Temperature

• PMBus Revision 1.2 Compliant with PEC and Extended Manufacturer Specific Commands

• 6 PWM Control Signals with 312.5 ps Resolution

  – Programmable Switching Frequency from 48.8 kHz to 1 MHz

  – Multi-segments Soft-start of Duty and Switching Period for Open-loop LLC

  – Frequency Synchronization

  – Support HiZ Mode

• High-speed Voltage Sense

  – Independent 50 MHz 11-bit Tracking ADC for Input Voltage and Output Voltage Sense

  – Up to 1.6 V Differential Voltage Sense

  – Secondary-side Rectified Voltage Sense Capability for VFF

• High-speed Current Sense

  – 25 MHz Σ-Δ ADC for CS1 and CS2

  – Primary-side Cycle-by-cycle Fast over-current Protection

  – Secondary-side Cycle-by-cycle Fast overcurrent Protection

  – Secondary-side Diode Emulation Mode

• Advance control algorithm  

  – Digital Control Loop with Programmable Loop Filters for CCM, DCM and Low-temperature

  – Duty-cycle Double Update

  – Fast Line Voltage Feed-forward

  – Pre-bias Startup

  – Synchronous Rectifier Control in DCM Condition

• Auxiliary functions

  – 25 MHz Σ-Δ ADC for TSNS, ADDR, VSET

  – Accurate Droop Current Sharing

  – IMON for Output Current Indicator

  – Compatible with NTC Temperature Sense

  – Redundant Programmable OVP

  – Extensive Fault Detection and Protection

  –Up to 4 GPIOs

  – Compatible with DOSA Analog Trim 

• Programming via Easy-to-use Graphical User Interface (GUI)

• 512 bytes EEPROM for Programming and Data Storage

• Available at QFN4x4-24L Packages

Figure 2: Block diagram of a typical HP1000 application

Feature Highlight 1: Highly Configurable High-Performance Type-III Digital Compensator

The HP1000 integrates a high-performance Type-III digital compensator with configurable zeros and poles. It samples and filters the differential output voltage (VS±) signals through a high-speed tracking ADC before performing loop calculations, effectively reducing the impact of system disturbances on high-speed loop control. Additionally, the HP1000 supports a dual-sample, dual-update mode, significantly reducing control latency while improving system bandwidth and phase margin.

Figure 3 shows the performance under a 48 V input, 12 V output, and 20 A load condition with dual-sample, dual-update mode enabled. The crossover frequency is 16.3 kHz, with a phase margin of 67.8° and a gain margin of 10.6 dB.

Figure 3: Closed-loop transfer function bode plot with dual-sampling and dual-update enables

Figure 4 shows the performance under the same conditions with the dual-sample, dual-update mode disabled, achieving a crossover frequency of 10.7 kHz, a phase margin of 59.5°, and a gain margin of 10.75 dB.

Figure 4: Closed-loop transfer function bode plot with double sampling and double updating off

Feature Highlight 2: High-Speed Input Voltage Feedforward

The HP1000 utilizes a high-speed tracking ADC to support direct input voltage sampling (GPA mode) or secondary-side rectified voltage sampling (VRS mode). In transformer-isolated hard-switching bridge topology applications, sampling the plateau voltage of the secondary-side rectified voltage in VRS mode enables real-time participation in input voltage feedforward calculations. This allows the output PWM pulse width to dynamically adjust in response to input voltage variations.

Figure 5: Real-time input voltage monitoring and feedforward calculation via VRS sampling mode of VFF

Figure 6: Output current 20 A, input voltage step change from 36 V to 75 V (<10 μs), slew rate 6 V/μs

C1: VIN; C2: PWM2; C3: Primary Current; C4: VOUT (AC)

Feature Highlight 3: Digital Power Monitoring Functionality

The HP1000 incorporates comprehensive digital power monitoring (PSU Monitor) capabilities. Through the PMBus interface, the host system can accurately and in real-time acquire critical power parameters including input voltage, output voltage, output current, output power, module temperature, and fault protection status. This enables system administrators to maintain real-time awareness of power conditions and ensure safe operation.

Figure 7: HP1000 system real-time monitoring interface

Figures 8 and 9 show the output current and output voltage monitoring test data:

Figure 8: Output current monitoring

Figure 9: Output Voltage Monitoring

Hynetek has simultaneously launched a 240W full-bridge converter evaluation board for the HP1000. The key specifications of this evaluation board are as follows:

Input voltage: 36 to 75 VDC
Output voltage: 12 VDC
Output power: 240 W
Switching frequency: 200 kHz

Figure 10: 240 W Full-Bridge Converter Evaluation Board with HP1000

The following are some of the performance test results of the evaluation board:

Figure 11: Load Regulation

Figure 12: Line Regulation

Figure 13: Load transient test with 48V input voltage, output current step change from 0 to 10A, load slew rate 2.5A/μs

C1: VOUT (AC); C4: IOUT

Figure 14: Load transient response at 48V input, output current step change 10A to 20A (slew rate 2.5A/μs)

C1: VOUT (AC); C4: IOUT

Figure 15: Load transient performance (48V input, 0→20A output current step, 2.5A/μs slew rate)
C1: VOUT (AC); C4: IOUT

Figure 16, Output Voltage Overvoltage Protection and Restart

C1: VOUT; C4: IOUT

Figure 17: Constant current output with overcurrent/undervoltage protection and restart characteristics
C1: VOUT; C4: IOUT

Figure 18: Output short-circuit protection and restart behavior (48V input, output port shorted)
C1: VOUT; C4: IOUT

From "Adequate" to "Excellent" – HP1000 Makes Power Design Simpler, More Efficient, and Smarter!