Totem-pole Power Factor Correction (PFC) Rectifier: Description and Operation

Totem-pole PFC rectifier is widely used topology in single-phase applications for power factor correction.

1. Circuit Description
2. Circuit Operation
3. Circuit Analysis
4. Circuit Design

Circuit Description

The totem-pole topologies are shown below. This topology replace the conventional diode bridge rectifier in boost PFC topology with an active high-frequency switches in one leg and low-frequency diodes in another leg.

The diode leg can be further replace with low-frequency switches to reduce the conduction losses and further boost the efficiency.

This topology is also called bridgeless topology because it completely eliminated the diode bridge in boost PFC rectifier by replacing it with active switches.

• Leg-1 : fast/high-frequency leg

• Leg-2 : slow/low-frequency leg

Circuit Operation

The operation of totem-pole divided into

1. Positive half cycle: positive voltage and current
2. Negative half cycle: Negative voltage and current

Voltage and current which are drawn from grid are always in-pahse with same frequency.

Positive half cycle: positive voltage and current

Current which is drawn in positve half cycle from grid can go in two directions. One is through body diode of Q₁ and another is through switch Q₂.

• Current can enter through switch Q₂ when it is ON and leaves to grid through diode D₂ due to forward bias as shown in first figure below. This current does not flow through load. The stored energy in output capacitor discharge througu load resistance, hence output voltage appears.

Voltage across inductor,

V_L = V_s

• When Q₂ is OFF, current always go through body diode of switch Q₁ and flows through load, diode D₂ and then grid as shown in second figure below. This current does flow through output capacitor and load. The energy will be stroed in output capacitor and appears across load.

Voltage across inductor,

V_L = V_s – V_o

It is observed that D₂ always conducts to provide path to positve current in positve half cycle, conduction of body diode of Q₁ and switch Q₂ alter due to control of turn-on and turn-off periods for the switch Q₂.

Q₂ ON period: turn-on period of positve half cycle

Q₁ ON period: turn-off period of positive half cycle

Negative half cycle: negative voltage and current

Current which is flowing in negative half cycle to grid can flow in two directions. One is through switch Q₁ and another is through body diode of Q₂.

• Current can enter through switch Q₁ when it is ON and leaves to grid to flow through diode D₁ due to forward bias as shown in first figure below. This current does not flow through load. The stored energy in output capacitor discharge througu load resistance, hence output voltage appears.

Voltage across inductor,

V_L = V_s

• When Q₁ is OFF, current always go through body diode of switch Q₂ and flows through grid, diode D₁ and then load as shown in second figure below. This current does flow through output capacitor and load. The energy will be stroed in output capacitor and appears across load.

Voltage across inductor,

V_L = V_s + V_o

It is observed that D₁ always conducts to provide path to current in negative half cycle, conduction of body diode of Q₂ and switch Q₁ alter due to control of turn-on and turn-off periods for the switch Q₁.

Q₁ ON period: turn-on period of negative half cycle

Q₂ ON period: turn-off period of negative half cycle.

The analysis and design of above discussed totem-pole circuit is discussed here.