Architecture for multi-port AC/DC switching mode power supply
An architecture for a multi-port AC/DC Switching Mode Power Supply (SMPS) with Power Factor Correction (PFC) comprises power management control (PMC) for PFC On/Off Control and Smart Power Distribution, and optionally, a boost follower circuit. For example, in a universal AC/DC multi-port USB-C Power Delivery (PD) adapter, PMC enables turn-on and turn-off of PFC dependent on output port operational status and a combined load of active output ports. A microprocessor control unit (MCU) receives operational status, a voltage sense input and a current sense input for each USB port, computes output power for each USB port, and executes a power distribution protocol to turn-on or turn-off PFC dependent on the combined load from each USB port. Available power may be distributed intelligently to one or more ports, dependent on load. In an example embodiment, turning-off PFC for low load and low AC line input increases efficiency by 3% to 5%.
1. A method of operating a multi-port AC/DC SMPS which comprises power factor correction (PFC) and supplies a maximum output power of ≥75 W to a plurality of output ports, comprising:
in a microprocessor unit (MCU) of a power management control circuit, monitoring an operational status of each output port and a current and voltage being supplied to each output port;
computing an output power of each output port from said current and voltage being supplied to each output port; and
based on the operational status of each output port, and a combined output power being supplied to each output port, executing a power management protocol comprising:
when the combined output power is greater than a first threshold value, outputting a PFC On/Off trigger signal to a PFC On/Off circuit to turn on PFC or maintain the PFC in an on-state;
when the combined output power is less than a second threshold value, outputting a PFC On/Off trigger signal to the PFC On/Off circuit to turn off PFC or maintain the PFC in an off-state.
2. The method of claim 1 , comprising:
when only one output port is operational, enabling the maximum output power to be supplied to said one output port; and
when two or more output ports are operational, enabling power distribution of the maximum output power amongst the two or more ports that are operational.
3. The method of claim 2 , wherein said power distribution comprises unequal distribution of power to the two or more ports.
4. The method of claim 1 , wherein the multi-port AC/DC SMPS comprises a boost follower circuit (BFC), and comprising turning on the BFC when PFC is on and turning off the BFC when PFC is off.
5. A power management circuit for a multi-port AC/DC SMPS which comprises power factor correction (PFC) and supplies a maximum output power of ≥75 W to a plurality of output ports, comprising:
a microprocessor control unit (MCU) having an interface for monitoring an operational status of each output port and inputs for receiving voltage sense and current sense signals from each port,
a PFC On/Off circuit for controlling a supply voltage to the PFC to turn-on and turn-off the PFC;
the MCU being configured to implement the method of claim 1 .
6. A boost follower circuit for a multi-port AC/DC SMPS which comprises power factor correction (PFC), comprising:
a first voltage divider comprising resistors R 1 and R 2 to sense a PFC output voltage Vdc;
a second voltage divider comprising resistors R 3 and R 4 , a diode D 1 and a capacitor C 1 to sense an AC input peak voltage from a rectified voltage Vrect;
a transistor Q 3 , resistor R 6 , and Zener diode ZD 1 configured to provide a bias current i bias , wherein bias current i bias is inversely proportional to the AC input peak voltage through the transistor Q 3 , resistor R 6 , and Zener diode ZD 1 , which provides a bias voltage; and
wherein a feedback signal FB is provided to the PFC controller and the PFC output voltage V dc follows with input AC voltage and is equal to:
Vdc
=
(
Vref
R
2
-
i
bias
)
×
R
1
+
Vref
.
7. The boost follower circuit (BFC) of claim 6 which is controlled by the same supply voltage Vcc_PFC, as for the PFC, so that when the PFC is on, the BFC is on, and when the PFC is off, the BFC is off.
8. A multi-port AC/DC Switching Mode Power Supply (SMPS) comprising a power factor correction circuit (PFC) for converting an AC input voltage to a DC voltage Vdc, and a DC/DC converter which receives Vdc and supplies a bus voltage Vbus to a plurality of output ports, each output port comprising a DC/DC converter providing an output voltage Vout, comprising:
power control comprising a microcontroller unit (MCU) and a PFC On/Off control circuit comprising means to turn the PFC on and off;
each of the output ports comprising a current sense circuit and a voltage sense circuit which output current sense and voltage sense signals;
the MCU having inputs for receiving said current sense and voltage sense signals from the current sense circuit and voltage sense circuit of each output port, and having an interface to controllers of the DC/DC converters of each of the output ports;
the MCU being configured to execute a power management protocol comprising:
obtaining an output status comprising an operational status of each output port, and an output power of each output port, computed from the current and voltage sense signals from each output port, and
based on the output status, outputting a trigger to the PFC on/off control circuit to turn the PFC on or off.