Voltage detection circuit and a method of detecting voltage changes

Patent metadata

Field	Value
Publication number	US-9515570-B2
Application number	US-201514671001-A
Country	US
Kind code	B2
Filing date	Mar 27, 2015
Priority date	Dec 3, 2014
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A power conversion system and a method for voltage change detection, specifically, relates to a detection circuit implemented in the AC-DC power converter, detect the voltage change. The AC input voltage is rectified to convert into a DC input voltage transmitted to a detection unit generating a detection voltage signal at different logical states corresponding to the input voltage changes. A charge current source unit is used for charging the capacitor when the detection voltage signal is in a second state and a discharge current source unit is used for discharging the capacitor when the detection voltage signal is in a first state. A primary comparator compares the voltage changes of the capacitor in the alternating charge and discharge processes with a critical zero potential and outputs a detection signal identifying the changing trend of the input voltage.

First claim

The invention claimed is:

1. A voltage detection circuit comprising:
a rectifier circuit converting an AC voltage to a DC input voltage;
a detection unit receiving the DC input voltage and generating a detection voltage signal of different states of logic level corresponding to fluctuations of the DC input voltage amplitude;
a capacitor;
a charge current source unit for charging the capacitor when the detection voltage signal is in a second state of logic level;
a discharge current source unit for discharging the capacitor when the detection voltage signal is in a first state of logic level; and
a primary comparator comparing a varying voltage of the capacitor in the alternating processes of charging and discharging with a critical zero potential and generating a detection signal that identifies a changing trend of the input voltage.

2. The voltage detection circuit of claim 1 , wherein, when the input voltage exceeds a preset value, the detection unit generates the detection voltage signal of the first state; and when the input voltage is less than the preset value, the detection unit generates a detection voltage signal of the second state.

3. The voltage detection circuit of claim 2 , wherein the detection unit comprises a Zener diode and a junction field effect transistor with an anode of the Zener diode connected to a drain of the junction field effect transistor, wherein the input voltage is applied to a cathode of the Zener diode and the preset value is a breakdown voltage of the Zener diode, wherein the detection voltage signal is generated at a source of the junction field effect transistor.

4. The voltage detection circuit of claim 3 , wherein the source of the junction field effect transistor is connected to a non-inverting input terminal of a comparator in the detection unit, an inverting input terminal of the comparator is applied with a threshold voltage;
wherein when the input voltage is higher than the preset value, the detection voltage signal potential is greater than the threshold voltage, characterizing in that the detection voltage signal of the first state having a logic high level, and a drive signal generated by the comparator in the detection unit is high level;
when the input voltage is lower than the preset value, the detection voltage signal potential is smaller than the threshold voltage, characterizing in that the detection voltage signal of the second state having a logic low level, and the drive signal generated by the comparator in the detection unit is low level.

5. The voltage detection circuit of claim 1 , wherein the charge current source unit includes a voltage-current converter and a switch connected between a voltage source and an input terminal of the voltage-current converter;
wherein when the detection voltage signal is in the second state, the detection unit transmits a drive signal to turn on the switch, providing the voltage source for the charge current source unit to convert into a charge current to charge the capacitor.

6. The voltage detection circuit of claim 1 , wherein the discharge current source unit comprises a voltage-current converter and a switch connected between a voltage source and an input terminal of the voltage-current converter;
wherein when the detection voltage signal is in the first state, the detection unit transmits a drive signal to turn on the switch, providing a voltage source for the discharge current source unit to convert into a discharge current to discharge the capacitor.

7. The voltage detection circuit of claim 3 , wherein at a falling edge the detection voltage signal changes from the first state to the second state, the capacitor begins to charge, and at a rising edge the detection voltage signal changes from the second state to the first state, the capacitor begins to discharge; and
at each falling edge the detection voltage signal changes from the first state to the second state, a transient discharge of the capacitor occurs before the capacitor begins to charge.

8. The voltage detecting circuit of claim 7 further comprising a switch connected in parallel with the capacitor and with one end grounded, wherein a drive signal from the detection unit after going through an inverter is fed to an input terminal of a monostable multivibrator, an output terminal of the monostable multivibrator is connected to a control terminal of the switch;
a rising edge obtained by inverting the falling edge of the detection voltage signal via the inverter is used to trigger the monostable multivibrator to output a drive signal to turned on the switch thus resulting in the transient discharge of the capacitor.

9. The voltage detection circuit of claim 8 , wherein a reference input voltage having a reference effective value V HVR is inputted to the detection unit, with the breakdown voltage of the Zener diode of V Z1 , within a cycle of the reference input voltage, a reference duty D B of the detection voltage signal having a first state is:

D
B

=

1
-

sin

-
1

⁡

(

V

Z
⁢

⁢
1

2

⁢

V
HVR

)

90
⁢
°

;

While the charge current of the capacitor, I 1 , and the discharge current of the capacitor, I 2 , satisfy the relationship

I
1

I
2

=

D
B

1
-

D
B

.

10. The voltage detection circuit of claim 9 , wherein when an actual duty cycle is greater than the reference duty cycle D B , the detection signal generated from the primary comparator in each cycle of the actual input voltage provides a high level signal, indicating a peak of the actual input voltage being greater than a peak of the reference input; or
when the actual duty cyc

Assignees

• Alpha And Omega Semiconductor (Cayman) Ltd
• Alpha & Omega Semiconductor

Inventors

• Chen Yu-Ming
• Liu Chih-Yuan
• Huang Pei-Lun

Classifications

• H02M1/4225

  using a non-isolated boost converter · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• G01R19/15

  Indicating the presence of current · CPC title

• G01R19/155

  Indicating the presence of voltage · CPC title

• H02M7/217 Primary

  using semiconductor devices only · CPC title