Switching mode power supply and the control method thereof

Patent metadata

Field	Value
Publication number	US-9401647-B2
Application number	US-201414191957-A
Country	US
Kind code	B2
Filing date	Feb 27, 2014
Priority date	Aug 9, 2013
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A switching mode power supply, having: a power switch; an energy storage component coupled to the power switch; a current sense resistor configured to generate a current sense signal; a mode select resistor configured to generate a mode select resistor; a ZCD (Zero Cross Detecting) circuit configured to generate a ZCD signal; and a control circuit configured to provide a switch control signal to control the on and off of the power switch, the control circuit having a multi-function pin configured to receive the mode select signal, the current sense signal and the ZCD signal.

First claim

I claim:

1. A switching mode power supply, comprising:
a power switch;
an energy storage component coupled to the power switch, the energy storage component storing energy when the power switch is on and transferring energy when the power switch is off;
a current sense resistor coupled between the power switch and a ground reference to generate a current sense signal based on a current flowing through the power switch;
a mode select resistor having a first terminal and a second terminal, the first terminal coupled to a connection node of the current sense resistor and the power switch;
a ZCD (zero cross detecting) circuit configured to generate a ZCD signal based on a voltage across the power switch;
a first diode having an anode terminal and a cathode terminal, the anode terminal coupled to the ZCD circuit to receive the ZCD signal; and
a control circuit configured to provide a switch control signal to control the on and off of the power switch, the control circuit having a multi-function pin coupled to the second terminal of the mode select resistor and the cathode terminal of the first diode;
wherein: in a startup period of the switching mode power supply, the control circuit compares a signal received by the multi-function pin with a mode control reference signal, and determines a work mode of the switching mode power supply based on a comparison result; in a normal operation period of the switching mode power supply, the control circuit compares the signal received by the multi-function pin with a peak current signal when the power switch is on, and compares the signal received by the multi-function pin with a ZCD reference signal when the power switch is off, and controlling the on and off of the power switch based on comparison results.

2. The switching mode power supply of claim 1 , wherein the control circuit comprises:
a startup detect circuit configured to generate a startup detect signal indicative of whether the control circuit is in the startup period or is in the normal operation period based on the status of the control circuit;
a mode control circuit having a first input terminal coupled to the multi-function pin of the control circuit to receive a mode select signal, a second input terminal coupled to the startup detect circuit to receive the startup detect signal, a third input terminal configured to receive the mode control reference signal, and an output terminal configured to generate a mode control signal based on the mode select signal, the startup detect signal and the mode control reference signal;
a peak current signal circuit having a first input terminal configured to receive a rectified voltage, a second input terminal coupled to the mode control circuit to receive the mode control signal, a third input terminal configured to receive a feedback reference signal, a fourth input terminal coupled to the multi-function pin to receive the current sense signal, a fifth input terminal configured to receive the switch control signal, and an output terminal configured to provide the peak current signal based on the rectified voltage, the mode control signal, the feedback reference signal, the current sense signal and the switch control signal;
a voltage control circuit having a control terminal configured to receive the switch control signal, a first input terminal coupled to the multi-function pin to receive the ZCD signal, a second input terminal configured to receive the ZCD reference signal, and an output terminal configured to provide a voltage control signal based on the switch control signal, the ZCD signal and the ZCD reference signal;
a current control circuit having a control terminal configured to receive the switch control signal, a first input terminal coupled to the multi-function pin to receive the current sense signal, a second input terminal coupled to the peak current signal circuit to receive the peak current signal, and an output terminal configured to provide a current control signal based on the switch control signal, the current sense signal and the peak current signal; and
a logic circuit having a first input terminal coupled to the voltage control circuit to receive the voltage control signal, a second input terminal coupled to the current control circuit to receive the current control signal, and an output terminal configured to provide the switch control signal based on the voltage control signal and the current control signal.

3. The switching mode power supply of claim 2 , wherein the peak current signal circuit comprises:
a current average circuit having a first input terminal coupled to the multi-function pin to receive the current sense signal, a second input terminal configured to receive the switch control signal, and an output terminal configured to provide a current average signal based on the current sense signal and the switch control signal;
an error amplifier having a first input terminal coupled to the current average circuit to receive the current average signal, a second input terminal configured to receive the feedback reference signal, and an output terminal configured to provide an error amplify signal based on the current average signal and the feedback reference signal;
an input voltage process circuit having a first input terminal configured to receive the rectified voltage, a second input terminal coupled to the mode control circuit to receive the mode control signal, and an output terminal configured to provide a PFC (Power Factor Correction) reference signal based on the rectified voltage and the mode control signal; and
a first multiply circuit having a first input terminal coupled to the input voltage process circuit to receive the PFC reference signal, a second input terminal coupled to the error amplifier to receive the error amplify signal, and an output terminal configured to provide the peak current signal based on the PFC reference signal and the error amplify signal.

4. The switching mode power supply of claim 3 , wherein the input voltage process circuit comprises:
a peak detect circuit having an input terminal configured to receive the rectified voltage, and an output terminal configured to provide a peak detect signal indicative of a peak value of the rectified voltage based on the rectified voltage;
a second multiply circuit having an input terminal coupled to the peak detect circuit to receive the peak detect signal, and an output terminal configured to generate a clamp reference signal based on the peak detect signal, wherein the clamp reference signal is a product of the peak detect signal and a coefficient smaller than 1;
a clamp circuit having a first input terminal coupled to the second multiply circuit to receive the clamp reference signal, a second input terminal configured to receive the rectified voltage, and an output terminal configured to provide a clamped signal based on the clamp reference signal and the rectified voltage; and
a first select circuit having a control terminal configured to receive the mode control signal, a first input terminal coupled to the clamp circuit to receive the clamped signal, a second input terminal configured to receive the rectified voltage, and an output terminal configured to provide the clamped signal or the rectified voltage as the PFC reference signal based on the mode control signal.

5. The switching mode power supply of claim 2 , wherein the peak current signal circuit comprises:
an error amplifier having a first input terminal configured to receive a feedback signal indicative of the output voltage of the switching mode power supply, a second input terminal configured to receive a feedback reference signal, and an output terminal configured to provide an error amplify signal based on the feedback signal and the feedback reference signal;
an input voltage process circ

Assignees

• Chengdu Monolithic Power Sys
• Chengdu Monolithic Power Systems Co Lt D

Inventors

• Kuang Naixing

Classifications

• H02M1/083

  for the ignition at the zero crossing of the voltage or the current · CPC title

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M2001/0058

  Electricity · mapped topic

• H02M1/36

  Means for starting or stopping converters · CPC title

• Y02B70/10

  Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes · CPC title