Low voltage warning circuit

• US 8,258,971 B2
• Filed: 06/17/2010
• Issued: 09/04/2012
• Est. Priority Date: 04/02/2010
• Status: Expired due to Fees

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: Huang, Yong-Zhao
• Primary Examiner(s): PHAM, TOAN NGOC
• Application Number:
  US12/818,120
• Publication Number:
  US 20110241894A1
• Time in Patent Office: 810 Days
• Field of Search: 340/663, 340/636.15, 340/660, 340/661, 340/662, 361/92, 320/135, 320/136
• US Class Current: 340/663
• CPC Class Codes: G01R 19/165 Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values

Abstract

A low voltage warning circuit includes an input terminal configured to receive a supply voltage, a reference voltage connected to the input terminal for providing a reference voltage, a transistor connected to the reference voltage circuit and the input terminal, and a silicon controlled rectifier connected to the transistor and the input terminal via a indicating device, the low voltage warning circuit raise a warning through the indicating device when the supply voltage is below the reference voltage.

Claims

1. A low voltage warning circuit, comprising:

an input terminal configured to receive a supply voltage;

a reference voltage circuit comprising a first terminal connected to the input terminal and a second terminal grounded;

a transistor comprising a base connected to a first node between the input terminal and the reference voltage circuit, an emitter connected to the input terminal, and a collector; and

a silicon controlled rectifier comprising a control terminal connected to the collector, a first anode connected to the input terminal via a indicating device, and a first cathode grounded;

wherein the reference voltage circuit provides a reference voltage to the base, the indicating device raise a warning when the supply voltage below the summation of the reference voltage and a switching voltage of the transistor.

2. The low voltage warning circuit as claimed in claim 1, wherein the reference voltage circuit comprises an adjustable reference source, a first voltage dividing resistor, and a second voltage dividing resistor, the first voltage dividing resistor comprises a first terminal connected to the first node and a second terminal grounded via the second voltage dividing resistor, the adjustable reference source comprises a reference terminal, a second anode, and a second cathode, the reference terminal is connected to a second node between the first voltage dividing resistor and the second voltage dividing resistor, the second cathode is connected to the first node, the second anode is grounded.

3. The low voltage warning circuit as claimed in claim 1, wherein the low voltage warning circuit further comprises a first resistor connected between the input terminal and the first node and configured to control current flowing through the base of the transistor.

4. The low voltage warning circuit as claimed in claim 3, wherein the reference voltage circuit is a Zener diode comprising a first terminal connected to the first resistor and a second terminal grounded.

5. The low voltage warning circuit as claimed in claim 1, wherein the low voltage warning circuit further comprises a second resistor connected between the collector of the transistor and the control terminal of the silicon controlled rectifier and configured to control current flowing through the emitter of the transistor.

6. The low voltage warning circuit as claimed in claim 1, wherein the low voltage warning circuit further comprises a third resistor connected between the indicating device and the input terminal and configured to control current flowing through the silicon controlled rectifier.

7. The low voltage warning circuit as claimed in claim 1, wherein the indicating device is a lamp.

8. The low voltage warning circuit as claimed in claim 1, wherein the indicating device is a light emitting diode.

9. A low voltage warning circuit comprising:

an input terminal configured to receive a supply voltage;

a first voltage dividing resistor comprising a first terminal connected to the input terminal and a second terminal grounded through a second voltage dividing resistor;

an adjustable reference source comprising a reference terminal connected to a first node between the first voltage dividing resistor and the second voltage dividing resistor, a first cathode connected to a second node between the input terminal and the first voltage dividing resistor, and a second anode grounded;

a transistor comprising a base connected to the second node, a emitter connected to the input terminal, and a collector; and

a silicon controlled rectifier comprising a control terminal connected to the collector, a second anode connected to the input terminal via a indicating device, and a second cathode grounded;

wherein the adjustable reference voltage, the first voltage dividing resistor, and the second voltage dividing resistor cooperatively provide a reference voltage to the base, the indicating device to raise a warning when the supply voltage below the summation of the reference voltage and a switching voltage of the transistor.

10. The low voltage warning circuit as claimed in claim 9, wherein the low voltage warning circuit further comprises a first resistor connected between the input terminal and the first node and configured to control current through the base of the transistor.

11. The low voltage warning circuit as claimed in claim 9, wherein the low voltage warning circuit further comprises a second resistor connected between the collector of the transistor and the control terminal of the silicon controlled rectifier and configured to control current through the emitter of the transistor.

12. The low voltage warning circuit as claimed in claim 9, wherein the low voltage warning circuit further comprises a third resistor connected between the indicating device and the input terminal and configured to control current through the silicon controlled rectifier.

13. The low voltage warning circuit as claimed in claim 9, wherein the indicating device is a lamp.

14. The low voltage warning circuit as claimed in claim 9, wherein the indicating device is a light emitting diode.

15. A low voltage warning circuit comprising:

an input terminal configured to receive a supply voltage;

a Zener diode comprising a first terminal connected to the input terminal and a second terminal grounded;

a transistor comprising a base connected to a first node between the input terminal and the Zener diode, an emitter connected to the input terminal, and a collector; and

a silicon controlled rectifier comprising a control terminal connected to the collector, a second anode connected to the input terminal via a indicating device, and a second cathode grounded;

wherein the Zener diode to provide a reference voltage to the base, the indicating device to raise a warning when the supply voltage below the summation of the reference voltage and a switching voltage of the transistor.

16. The low voltage warning circuit as claimed in claim 15, wherein the low voltage warning circuit further comprises a first resistor connected between the input terminal and the first node and configured to control current through the base of the transistor.

17. The low voltage warning circuit as claimed in claim 15, wherein the low voltage warning circuit further comprises a second resistor connected between the collector of the transistor and the control terminal of the silicon controlled rectifier and configured to control current through the emitter of the transistor.

18. The low voltage warning circuit as claimed in claim 15, wherein the low voltage warning circuit further comprises a third resistor connected to the indicating device and the input terminal and configured to control current through the silicon controlled rectifier.

19. The low voltage warning circuit as claimed in claim 15, wherein the indicating device is a lamp.

20. The low voltage warning circuit as claimed in claim 15, wherein the indicating device is a light emitting diode.