“How is dynamic voltage regulation typically done efficiently in digital power supplies? Dynamic voltage regulation means that the output voltage of the power supply can be adjusted during operation. There are several reasons for making such adjustments.
How is dynamic voltage regulation typically done efficiently in digital power supplies? Dynamic voltage regulation means that the output voltage of the power supply can be adjusted during operation. There are several reasons for making such adjustments.
Improved conversion efficiency of the PFC stage under light load operating conditions
Power Factor Correction (PFC) stage for power compensation, which boosts the AC voltage of the grid voltage to the DC intermediate circuit voltage. In a 240 V AC system, this intermediate circuit voltage is typically 380 V, as shown in Figure 1. The ADP1047 PFC controller can use DVS to independently step down the output voltage load, eg, to 360 V, without affecting the set 380 V voltage. This improves the conversion efficiency of the power supply during partial load operation.
Figure 1. ADP1047 PFC Stage with Downstream ADP1046 DC-DC Converter
Microcontrollers operate efficiently in various operating states
Another DVS usage example is shown in Figure 2. In this example, the ADP2147 step-down switching regulator powers a digital signal processor (DSP). In many applications, a microcontroller, DSP, or FPGA can be used to increase system efficiency by reducing the core voltage while the processor is in standby mode. Various DSPs, including the ADSP-BF527 from Analog Devices, can operate more efficiently when the VDD_INT voltage (core voltage) is reduced (eg, from 1.2 V to 1.0 V when the DSP is operating at low load). The power consumption of a processor is largely proportional to the square of its clock frequency and operating voltage. Reducing the supply voltage of the ADSP-BF527 by 25% reduces dynamic power consumption by more than 40%. Many of ADI’s DSPs have similar characteristics.
Figure 2. ADP2147 switching regulator with DVS enables efficient operation of ADSP-BF527
Improved recovery speed after load transients
As shown in the previous two examples, common reasons for using DVS are to improve efficiency or reduce losses. However, there are other interesting applications as well. Many systems require a precisely regulated supply voltage. For the voltage range shown in Figure 3, a 1.2 V core voltage can be used. This voltage can be 1.2 V ± 10%. In this example, the voltage is kept constant under static load and when the load changes dynamically. If the feedback control is set in the middle of the allowable range, half the range applies to static error sources as well as to dynamic voltage changes after load transients. There is a little trick to slightly increase the output voltage at low loads and slightly lower it at high loads. Under high load conditions, lower loads are sometimes used, in which case a small voltage overshoot usually occurs. This voltage overshoot can be kept within tolerance by slightly reducing the set point voltage for high loads, as shown in Figure 3. High load on the left and low load on the right.
Figure 3. Dynamically Adjusting Supply Voltage Based on Load Current
The opposite situation naturally also applies. It goes up at some point when the load is low. Voltage overshoot may occur dynamically. At low loads, the voltage rises slightly, so it remains within the allowable range. For this characteristic, it is usually called voltage auto-positioning.
In addition to the above-mentioned applications, there are many other applications where dynamically varying voltages are advantageous. Examples include controlling DC motors, operating actuators, or driving Peltier elements for temperature regulation. Dynamic voltage regulation refers to the dynamic regulation of the generated voltage, which can be very helpful or even necessary for many applications. Especially in digitally controlled power supplies, DVS is common and easy to implement.