Digitally controlled PFC converter with multiple discontinuous modes

Patent metadata

Field	Value
Publication number	US-9621028-B2
Application number	US-201514692465-A
Country	US
Kind code	B2
Filing date	Apr 21, 2015
Priority date	Apr 22, 2014
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

A PFC circuit having a switching circuit and a control circuit, the control circuit controls an operation mode of the switching circuit based on an input current and a switching frequency of the switching circuit, when the switching circuit works under a continuous current mode, the switching circuit is turned ON when the input current is less than an OFF current reference signal, and when the switching circuit works under a first discontinuous mode or a second discontinuous mode, the switching circuit is turned ON after a turn ON delay time period when the input current is less than the OFF current reference signal.

First claim

We claim:

1. A control method for controlling a power factor correction circuit, wherein the power factor correction circuit comprises a switching circuit having an input terminal configured to receive an input voltage and an input current, and an output terminal configured to provide an output voltage, the control method comprising:
providing a peak current sampling signal indicative of a maximum value of the input current;
providing an input voltage sampling signal indicative of the input voltage;
providing an output voltage sampling signal indicative of the output voltage;
providing a current reference signal based on the input voltage sampling signal, the output voltage sampling signal and a voltage reference signal;
providing a turn ON delay time period based on the peak current sampling signal and the current reference signal;
providing a comparison signal via comparing the input current with an OFF current reference signal;
determining an operation mode of the switching circuit based on the input current and a switching frequency of the switching circuit, wherein the operation mode comprises a continuous current mode, a first discontinuous current mode and a second discontinuous current mode; and
turning ON the switching circuit based on the comparison signal, and turning OFF the switching circuit when an ON-time period of the switching circuit equals a predetermined ON-time period; wherein
when the switching circuit works under the continuous current mode, turning ON the switching circuit when the input current is less than the OFF current reference signal, and calculating the predetermined ON-time period based on the input voltage sampling signal; wherein
and calculating the predetermined ON-time period based on the input voltage sampling signal; and wherein

when the switching circuit works under the second discontinuous current mode, turning ON the switching circuit after the turn ON delay time period when the input current is less than the OFF current reference signal, and calculating the predetermined ON-time period based on the input voltage sampling signal, the current reference signal and the peak current sampling signal.

2. The control method of claim 1 , further comprising:
when twice of the current reference signal is larger than or equals the peak current sampling signal, the switching circuit transits to the continuous current mode, and the OFF current reference signal is provided based on the current reference signal and the peak current sampling signal;
when twice of the current reference signal is smaller than the peak current sampling signal and a switching frequency of the switching circuit is higher than a minimum frequency threshold, the switching circuit transits to the first discontinuous current mode, and the OFF current reference signal equals a constant; and
when twice of the current reference signal is smaller than the peak current sampling signal and the switching frequency of the switching circuit is lower than or equals the minimum frequency threshold, the switching circuit transits to the second discontinuous current mode, and the OFF current reference signal equals the constant.

3. The control method of claim 1 , wherein when the switching circuit works under the first discontinuous current mode, the turn ON delay time period equals Tmin*Iref(n)/2Ipk(n)−Tmin, where Tmin is constant, Iref(n) is the current reference signal, and Ipk(n) is the peak current sampling signal.

4. The control method of claim 1 , wherein when the switching circuit works under the second discontinuous current mode, the turn ON delay time period equals Tmax−2Iref(n)*Tmax/Ipk(n), where Tmax is constant, Iref(n) is the current reference signal, and Ipk(n) is the peak current sampling signal.

5. The control method of claim 1 , further comprising:
providing a delay time period based on the peak current sampling signal and the current reference signal; and
providing the turn ON delay time period based on the delay time period and an oscillation period of the input current during discontinuous.

6. The control method of claim 5 , wherein when the switching circuit works under the first discontinuous current mode, the delay time period equals Tmin*Iref(n)/2Ipk(n)−Tmin, and when the switching circuit works under the second discontinuous current mode, the delay time period equals Tmax−2Iref(n)*Tmax/Ipk(n), where Tmin and Tmax are constant, Iref(n) is the current reference signal, and Ipk(n) is the peak current sampling signal.

7. The control method of claim 5 , wherein the turn ON delay time period equals (K+0.5)Tzcd, where Tzcd is the oscillation period of the input current during discontinuous, and K is an integer making (K+0.5)Tzcd as close as possible to the delay time period.

8. The control method of claim 5 , wherein the turn ON delay time period equals Td 1 ( n )−Td 1 ( n )mod(Tzcd)+Tzcd/2, where Td 1 ( n ) is the delay time period, Tzcd is the oscillation period of the input current during discontinuous.

9. A control circuit for controlling a power factor correction circuit, wherein the power factor correction circuit comprises a switching circuit having an input terminal configured to receive an input voltage and an input current, and an output terminal configured to provide an output voltage, the control circuit comprising:
an AD conversion control module configured to provide an input voltage sampling signal based on the input voltage, an output voltage sampling signal based on the output voltage, and a peak current sampling signal based on the input current;
a DA conversion unit configured to provide an OFF current reference signal based on a digital OFF current reference signal;
a current reference computing module configured to provide a current reference signal based on the input voltage sampling signal and the output voltage sampling signal;
a mode control module configured to provide a mode control signal based on the current reference signal, the peak current sampling signal and a switching frequency of the switching circuit; and
a pulse generator configured to provide a switching control signal to control the switching circuit, wherein the switching control signal is configured to turn OFF the switching circuit based on a predetermined ON-time period; wherein
when the mode control signal is at a first state, the switching circuit works under a continuous current mode, and the switching control signal is configured to turn ON the switching circuit when a feedback signal indicative of the input current is less than the OFF current reference signal; wherein
when the mode control signal is at a second state, the switching circuit works under a first discontinuous current mode, and the switching control signal is configured to turn ON the switching circuit after a turn ON delay time period when the feedback signal indicative of the input current is less than the OFF current reference signal; and wherein
when the mode control signal is at a third state, the switching circuit works under a second discontinuous current mode, and the switching control signal is configured to turn ON the switching circuit after the turn ON delay time period when the feedback signal indicative of the input current is less than the OFF current reference signal.

10. The control circuit of claim 9 , wherein the control circuit further comprises:
an OFF current computing module configured to provide the digital OFF current reference signal based on the mode control signal, the current reference signal and the peak current sampling signal;
an ON-time period computing module configured to provide the predetermined ON-time period, wherein when the mode control signal is at the first state or the second state, t

Assignees

• Chengdu Monolithic Power Sys

Inventors

• Lin Sicong
• Lu Wenbin
• Hu Wangmiao
• Jiang Lijie
• Zhao Qiming
• Zhang Guangchao

Classifications

• H02M1/4225 Primary

  using a non-isolated boost converter · CPC title

• Y02B70/126

  Cross-Sectional Technologies · mapped topic

• H02M2001/0019

  Electricity · mapped topic

• H02M2001/0012

  Electricity · mapped topic

• H02M1/0019

  the disturbance parameters being load current fluctuations · CPC title