Voltage converter

Patent metadata

Field	Value
Publication number	US-9960664-B2
Application number	US-201615240787-A
Country	US
Kind code	B2
Filing date	Aug 18, 2016
Priority date	Dec 7, 2014
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

A voltage converter comprises a second controller as a power switch of the secondary side of the transformer for comparing a detection voltage representing an output voltage and/or load current with a first reference voltage and generating a control signal, and a coupling element for transmitting the control signal generated by the second controller to the first controller on the primary side of the transformer enabling the first controller to generate a first pulse signal driving the power switch to control the on/off state of the primary side winding.

First claim

The invention claimed is:

1. A voltage converter comprising:
a transformer comprising a primary winding and a secondary winding, wherein the primary winding and a master switch are connected in series between an input voltage and a ground terminal, and the secondary winding is connected between an output node for providing an output voltage to a load and a reference ground potential;
a first controller configured to produce a first pulse signal for driving the master switch to be turned on or turned off;
a second controller configured to compare a detection voltage representing the output voltage and/or a load current value with a first reference voltage, thus determining the logic state of a control signal generated thereof according to a comparison result signal, wherein the detection voltage is inputted at an inverting input terminal of a first comparator of the second controller while the first reference voltage is inputted at a non-inverting input terminal; further, when the detection voltage is lower than the first reference voltage, an RS trigger of the second controller is set by a high level comparison result signal of a first comparator, so that a control signal outputted by the RS trigger is turned from a low level to a high level; further, an on-time generator of the second controller starts timing from the moment that the control signal turns from the low level to the rising edge of the high level, and finishes timing when a preset on-time is ended; and further, when the timing is finished, a signal outputted by the on-time generator turns from the low level to the high level and resets the RS trigger, so that the control signal is turned from the high level to the low level; and
a coupling element connected between the first and the second controllers for transferring the logic state of the control signal from the second controller to the first controller, so that the first controller determines the logic state of the first pulse signal according to the logic state of the control signal.

2. The voltage converter of claim 1 , wherein
a first switch and a second switch are connected in series between one bias circuit of the second controller and the reference ground potential, the first and second switches are mutually connected to a common node, the first switch is driven by the control signal while the second switch is driven by an inversion signal of the control signal; and
a first capacitor of the coupling element is connected between a non-inverting input terminal of the second comparator in the first controller and the common node, while a second reference voltage is inputted to an inverting input terminal of the second comparator, a resistor is connected between the non-inverting input terminal of the second comparator and the ground terminal, and a second capacitor of the coupling element is connected between the ground terminal and the reference ground potential.

3. The voltage converter of claim 2 , wherein
the first switch is turned on while the second switch is turned off when the control signal is at the high level, the voltage provided by the bias circuit is applied at the common node, the voltage of the non-inverting input terminal of the second comparator is increased greater than the second reference voltage by the coupling element, and the second comparator outputs a high level first pulse signal; and
the first switch is turned off while the second switch is turned on when the control signal is at the low level, the potential at the common node is clamped to the reference ground potential, the voltage of the non-inverting input terminal of the second comparator is reduced lower than the second reference voltage by the coupling element, and the second comparator outputs a low level first pulse signal.

4. The voltage converter of claim 1 , wherein
the coupling element is a pulse transformer, the control signal is transmitted to one end of the primary winding of the pulse transformer through one coupling capacitor in the second controller, and the other end of the primary winding is connected to the reference ground potential; and
a coupling capacitor is connected between one signal generation node in the first controller and one end of the secondary winding of the pulse transformer, and the other end of the secondary winding is connected to the ground terminal, so that a first pulse signal keeping consistent with the logic state of the control signal is generated at the signal generation node.

5. The voltage converter of claim 4 , wherein a resistor and a diode are arranged in parallel and are connected between the signal generation node and the ground terminal, and a cathode of the diode is connected to the signal generation node while an anode of the diode is connected to the ground terminal.

6. The voltage converter of claim 1 , wherein an anode of one rectifier diode is connected to one end of the secondary winding of the transformer, a cathode of the rectifier diode is connected to the output node, and the other end of the secondary winding of the transformer is then directly connected to the reference ground potential.

7. The voltage converter of claim 1 , wherein one end of the secondary winding of the transformer is directly connected to the output node, and a synchronous switch is connected between the other end of the secondary winding of the transformer and the reference ground potential, wherein:
the synchronous switch is driven by a second pulse signal which is an inversion signal mutually to the first pulse signal generated by the second controller, and the synchronous switch is turned off when the master switch is turned on, and the synchronous switch is turned on when the master switch is turned off; or
the synchronous switch is driven by a second pulse signal generated by the second controller, and the synchronous switch is controlled to be turned off by the second pulse signal during a stage that the first pulse signal controls the master switch to be turned off.

8. The voltage converter of claim 7 , wherein
a sampling holder in the on-time generator samples and holds the voltage value at the end of the secondary winding of the transformer connected to the synchronous switch during a stage that the master switch is turned on but the synchronous switch is turned off, and a voltage-current converter of the on-time generator converts the sampled voltage value into a current to charge a charging capacitor in the on-time generator;
a third switch in the on-time generator and the charging capacitor are connected in parallel between a charging node and the ground terminal, the voltage at the charging node is inputted into a non-inverting input terminal of a third comparator in the on-time generator while a third reference voltage is inputted into an inverting input terminal of the third comparator; and
a one-shot trigger of the second controller is triggered by the rising edge of the control signal to generate a high level clock signal, the clock signal is at a low level all the time but is at a high level at the moment of the rising edge of the control signal, so that the third switch is turned on by the clock signal at the moment of the rising edge of the control signal to discharge the charging capacitor transiently; and
the charging capacitor starts timing a charging time interval after discharging transiently until the voltage of the charging node is greater than the third reference voltage, so that the comparison result signal of the third comparator is stopped when the level is turned from low to high; the high level comparison result signal of the third comparator triggers the RS trigger to restore, and the period timed is served as the preset on-time for turning on the master switch.

9.

Assignees

• Alpha & Omega Semiconductor Cayman Ltd
• Alpha & Omega Semiconductor

Inventors

• Lin Tien-Chi
• Chen Yu-Ming
• Cheng Jung-Pei
• Hsu Yung-Chuan
• Yu Yueh-Ping
• Wang Wei-Ting
• Huang Pei-Lun

Classifications

• H02M3/33592

  having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer · CPC title

• H02M1/08 Primary

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• Y02B70/1475

  Cross-Sectional Technologies · mapped topic

• H02M2001/0009

  Electricity · mapped topic

• H02M1/36

  Means for starting or stopping converters · CPC title