Dual voltage threshold circuit and power-off protection circuit thereof

Abstract

The present invention provides a dual voltage threshold circuit and a power-off protection circuit thereof, wherein the power-off protection circuit comprises: a high threshold reset circuit, wherein when the voltage of a low voltage source is greater than a high threshold voltage, the output end of the high threshold reset circuit outputs a first level; when the voltage of the low voltage source is less than the high threshold voltage, the output end of the high threshold reset circuit outputs a second level or turns off the output; a switch circuit, which controls the connection or disconnection between the high voltage source and the power supply end of the high voltage circuit based on the output of the high threshold reset circuit; a low threshold reset circuit, wherein the input end is connected to the low voltage source, and the output end is connected to the power supply end of the low voltage circuit, and when the voltage of the low voltage source is greater than or less than the low threshold voltage, the low threshold reset circuit connects or disconnects the low voltage source to the power supply end of the low voltage circuit. Compared with the prior art, the present invention can protect the high voltage circuit when the low voltage circuit loses power.

Description

[Technical field]

[0001] The present invention relates to the technical field of circuit design, and in particular to a dual voltage threshold circuit and a power-off protection circuit thereof. [Background technology]

[0002] Please refer to Figure 1 As shown, it is a circuit diagram of a multi-voltage threshold circuit in the prior art, in which there are two or more voltage thresholds, wherein the power supply terminal of the high voltage circuit 110 is connected to the high voltage source VDD high The power supply terminal of the low voltage circuit 120 is connected to the low voltage source VDD low If the high voltage source VDD is connected, the low voltage circuit 120 will output a control signal to control the high voltage circuit 110. high If the low voltage source VDD low When the power is off, the control signal will be in an unknown state, causing the high-voltage circuit 110 to malfunction or even be damaged.

[0003] Therefore, it is necessary to propose an improved technical solution to overcome the above problems. [Summary of the invention]

[0004] One of the purposes of the present invention is to provide a dual voltage threshold circuit and a power-off protection circuit thereof, which can protect a high voltage circuit when a low voltage circuit loses power.

[0005] According to one aspect of the present invention, the present invention provides a power-off protection circuit of a dual voltage threshold circuit, which includes: a high threshold reset circuit, whose input terminal is connected to a low voltage source VDD low When the low voltage source VDD is connected low The voltage is greater than the preset high threshold voltage Vth high When the output terminal of the high threshold reset circuit outputs a first level; when the low voltage source VDD low The voltage is less than the high threshold voltage Vth high When the high threshold reset circuit outputs the second level or turns off the output; the switch circuit, the first connection terminal of which is connected to the high voltage source VDD high The switch circuit is connected to the high voltage source VDD, the second connection end of which is connected to the power supply end of the high voltage circuit, and the control end of which is connected to the output end of the high threshold reset circuit. When the output end of the high threshold reset circuit outputs a first level, the switch circuit switches the high voltage source VDD high connected to the power supply terminal of the high voltage circuit; when the output terminal of the high threshold reset circuit outputs the second level or turns off the output, the switch circuit cuts off the high voltage source VDD high A low threshold reset circuit, whose input terminal is connected to the low voltage source VDDlow connected, and its output end is connected to the power supply end of the low voltage circuit. When the low voltage source VDD low The voltage is greater than the low threshold voltage Vth low When the low threshold reset circuit resets the low voltage source VDD low connected to the power supply terminal of the low voltage circuit; when the low voltage source VDD low The voltage is less than the low threshold voltage Vth low When the low threshold reset circuit cuts off the low voltage source VDD low Connection to the power supply terminal of the low voltage circuit.

[0006] According to another aspect of the present invention, the present invention provides a dual voltage threshold circuit, which includes: a high voltage circuit; a low voltage circuit; and a power-off protection circuit. The power-off protection circuit includes: a high threshold reset circuit, whose input terminal is connected to a low voltage source VDD low When the low voltage source VDD is connected low The voltage is greater than the preset high threshold voltage Vth high When the output terminal of the high threshold reset circuit outputs a first level; when the low voltage source VDD low The voltage is less than the high threshold voltage Vth high When the high threshold reset circuit outputs the second level or turns off the output; the switch circuit, the first connection terminal of which is connected to the high voltage source VDD high The switch circuit is connected to the high voltage source VDD, the second connection end of which is connected to the power supply end of the high voltage circuit, and the control end of which is connected to the output end of the high threshold reset circuit. When the output end of the high threshold reset circuit outputs a first level, the switch circuit switches the high voltage source VDD high connected to the power supply terminal of the high voltage circuit; when the output terminal of the high threshold reset circuit outputs the second level or turns off the output, the switch circuit cuts off the high voltage source VDD high A low threshold reset circuit, whose input terminal is connected to the low voltage source VDD low connected, and its output end is connected to the power supply end of the low voltage circuit. When the low voltage source VDD low The voltage is greater than the low threshold voltage Vth low When the low threshold reset circuit resets the low voltage source VDD low connected to the power supply terminal of the low voltage circuit; when the low voltage source VDD low The voltage is less than the low threshold voltage Vth low When the low threshold reset circuit cuts off the low voltage source VDD low Connection with the power supply terminal of the low voltage circuit 220.

[0007] Compared with the prior art, the present invention designs reset circuits with different threshold voltages for high-voltage and low-voltage domains, thereby controlling the power-off reset sequence of different voltage domains to ensure that the circuit will not be damaged or abnormal due to uncertain power-off sequence, thereby protecting the high-voltage circuit when the low-voltage circuit is powered off.

Brief Description of the Drawings

[0008] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0009] Figure 1 It is a circuit diagram of a multi-voltage threshold circuit in the prior art;

[0010] Figure 2 FIG. 4 is a circuit diagram of a dual voltage threshold circuit in one embodiment of the present invention. [Specific implementation method]

[0011] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0012] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "connected", "connected", and "connected" herein that indicate electrical connection all refer to direct or indirect electrical connection.

[0013] Please refer to Figure 2 As shown, it is a circuit diagram of a dual voltage threshold circuit in one embodiment of the present invention. Figure 2 The dual voltage threshold circuit shown includes a high voltage circuit (or first circuit) 210 , a low voltage circuit (or second circuit) 220 , and a power-off protection circuit 230 .

[0014] The power-off protection circuit 230 includes a high threshold reset circuit (or a first threshold reset circuit) 232 , a switch circuit 234 , and a low threshold reset circuit (or a second threshold reset circuit) 236 .

[0015] The input terminal of the high threshold reset circuit 232 is connected to the low voltage source (or the second voltage source) VDD low The output end is connected to the control end 3 of the switch circuit 236, and the high threshold reset circuit 232 is used to compare the low voltage source VDDlow The voltage and the preset high threshold voltage (or first threshold voltage) Vth high When the low voltage source VDD low The voltage is greater than the high threshold voltage Vth high When the high threshold reset circuit 232 outputs the first level, the output terminal outputs the first level; when the low voltage source VDD low The voltage is less than the high threshold voltage Vth high When the high threshold reset circuit 232 outputs a second level or turns off the output, the first level and the second level can be two logic states of the same signal, for example, the first level is a high level and the second level is a low level, or the first level is a low level and the second level is a high level.

[0016] The first connection terminal 1 of the switch circuit 234 is connected to the high voltage source (or the first voltage source) VDD high The second connection terminal 2 is connected to the power supply terminal of the high voltage circuit 210, and the control terminal 3 is connected to the output terminal of the high threshold reset circuit 232. When the output terminal of the high threshold reset circuit 232 outputs the first level, the switch circuit 234 switches the high voltage source VDD high Connected to (or connected to) the power supply terminal of the high voltage circuit 210, the high voltage source VDD high Power the high voltage circuit 210; when the output terminal of the high threshold reset circuit 232 outputs the second level or turns off the output, the switch circuit 234 cuts off the high voltage source VDD high The connection with the power supply terminal of the high voltage circuit 210 is disconnected, and the power supply of the high voltage circuit 210 is cut off.

[0017] The input terminal of the low threshold reset circuit 236 is connected to the low voltage source VDD. low The output end of the low voltage circuit 220 is connected to the power supply end of the low voltage circuit 220, and the low threshold reset circuit 236 is used to compare the low voltage source VDD low The voltage is the same as the preset low threshold voltage (or second threshold voltage) Vth low When the low voltage source VDD low The voltage is greater than the low threshold voltage Vth low When the low threshold reset circuit 236 switches the low voltage source VDD low is connected to (or communicated with) the power supply terminal of the low voltage circuit 220, and the low voltage source VDD low Power the low voltage circuit 220; when the low voltage source VDD low The voltage is less than the low threshold voltage Vth low When the low threshold reset circuit 236 cuts off the low voltage source VDD low The connection with the power supply terminal of the low voltage circuit 220, that is, the low threshold reset circuit 234 is reset, the output is turned off, and the power supply of the low voltage circuit 220 is cut off.

[0018] Among them, the high voltage source VDD high Voltage value>Low voltage source VDD low Voltage value; low voltage source VDD low The voltage value of > high threshold voltage Vth high The voltage value of > low threshold voltage Vth low Voltage value.

[0019] In addition, the output end of the low voltage circuit 220 is connected to the control end of the high voltage circuit 210, and the low voltage circuit 220 outputs a control signal to the control end of the high voltage circuit 210 through its output end to control the high voltage circuit 210. High voltage source VDD high The voltage value can be as high as tens of volts, even hundreds of volts, or higher, such as 12V, 24V, 48V, 220V, 380V, etc. The low voltage source VDD low The voltage value can be several volts, such as 5V, 4.2V, etc. In one embodiment, the low voltage circuit 220 can also be referred to as a second circuit, and the low voltage source VDD low It can be called the second voltage power supply, the high voltage circuit 210 can also be called the first circuit, the high voltage source VDD high Can be called the first voltage source.

[0020] exist Figure 2 In the embodiment shown, the switch circuit 234 includes a first resistor R1, a second resistor R2, a first MOS transistor PM1, and a second MOS transistor NM1. The first connection end of the first MOS transistor PM1 is connected to the first connection end 1 of the switch circuit 234, the second connection end is connected to the second connection end 2 of the switch circuit 234, and the control end is connected to the high voltage source VDD via the first resistor R1. high The first connection end of the second MOS transistor NM1 is connected to the control end of the first MOS transistor PM1, the second connection end thereof is grounded, the control end thereof is connected to the control end 3 of the switch circuit 234, and the control end of the second MOS transistor NM1 is grounded via the resistor R2. When the output end of the high threshold reset circuit 232 outputs the first level, the first MOS transistor PM1 and the second MOS transistor NM1 are both turned on, and the first MOS transistor PM1 switches the high voltage source VDD to the high voltage source VDD. high connected (or connected) to the power supply terminal of the high voltage circuit 210; when the output terminal of the high threshold reset circuit 232 outputs the second level or turns off the output, the first MOS transistor PM1 and the second MOS transistor NM1 are both turned off, and the first MOS transistor PM1 cuts off the high voltage source VDD high Connection to the power supply terminal of the high voltage circuit 210.

[0021] exist Figure 2In the specific embodiment shown, the first MOS transistor PM1 is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the first MOS transistor MP1 are respectively the source, the drain and the gate of the PMOS transistor; the second MOS transistor NM1 is an NMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the second MOS transistor NM1 are respectively the drain, the source and the gate of the NMOS transistor; the first level output by the high threshold reset circuit 232 is a high level, and the second level output by the high threshold reset circuit 232 is a low level.

[0022] exist Figure 2 In the specific embodiment shown, when the low voltage source VDD low The voltage value is greater than the high threshold voltage Vth high When the high threshold reset circuit 232 outputs a high level, the gate of the second MOS transistor NM1 is pulled up to the high level, and the gate of the first MOS transistor PM1 is pulled down to the ground, so that the second MOS transistor NM1 and the first MOS transistor PM1 are both turned on, and the high voltage source VDD high Power the high voltage circuit 210; when the low voltage source VDD low The voltage value is less than the high threshold voltage Vth high When the high threshold reset circuit 232 is reset and the output is turned off, at this time, the gate of the second MOS transistor NM1 is pulled down to the ground, and the gate of the first MOS transistor PM1 is pulled up to the high voltage source VDD high , so that the second MOS transistor NM1 and the first MOS transistor PM1 are both turned off, and the power supply of the high-voltage circuit 210 is cut off.

[0023] It should be noted that, in another embodiment, Figure 2 The resistor R2 is removed and its Figure 2 The embodiment shown differs in that when the low voltage source VDD low The voltage value is less than the high threshold voltage Vth high When the high threshold reset circuit 232 outputs a low level, the gate of the second MOS transistor NM1 is pulled down to the low level, and the gate of the first MOS transistor PM1 is pulled up to the high voltage source VDD. high , so that the second MOS transistor NM1 and the first MOS transistor PM1 are both turned off, and the power supply of the high-voltage circuit 210 is cut off.

[0024] If the high voltage source VDD high If the power is turned off first, the high voltage circuit 210 will not be damaged. low First, the power is turned off. Since the threshold voltages of the two reset circuits 232 and 236 are different, the high threshold reset circuit 232 will be reset first and turn off the output (i.e., the low voltage source VDD). low First power down to a voltage lower than the high threshold voltage Vth high), at this time, the gate of the second MOS transistor NM1 is pulled down to ground, and the gate of the first MOS transistor PM1 is pulled up to the high voltage source VDD high , the second MOS transistor NM1 and the first MOS transistor PM1 are both turned off, so the power supply of the high voltage circuit 210 is cut off first; when the low voltage source VDD low Continue to power down to a voltage lower than the low threshold voltage Vth of the low threshold reset circuit 234 low When the low threshold reset circuit 234 is reset and the output is turned off, the power supply of the low voltage circuit 220 is cut off, so that when the low voltage circuit 220 loses power, the high voltage circuit 220 can be effectively protected.

[0025] In addition, Figure 2 The product shown in the figure with the dual voltage threshold circuit provided with the power-off protection circuit 230 has proved that the solution is simple, reliable and low-cost.

[0026] In the present invention, words such as “connect”, “connected”, “connected”, “connected”, etc. indicating electrical connection, if not otherwise specified, indicate direct or indirect electrical connection.

[0027] It should be noted that any changes made by those skilled in the art to the specific embodiments of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the above specific embodiments.

Claims

1. A power-off protection circuit for a dual voltage threshold circuit, characterized in that: It includes: High threshold reset circuit, its input terminal is connected to the low voltage source VDD low When the low voltage source VDD is connected low The voltage is greater than the preset high threshold voltage Vth high When the output terminal of the high threshold reset circuit outputs a first level; when the low voltage source VDD low The voltage is less than the high threshold voltage Vth high When , the output terminal of the high threshold reset circuit outputs a second level or turns off the output; The switch circuit has a first connection terminal connected to a high voltage source VDD high The switch circuit is connected to the high voltage source VDD, the second connection end of which is connected to the power supply end of the high voltage circuit, and the control end of which is connected to the output end of the high threshold reset circuit. When the output end of the high threshold reset circuit outputs a first level, the switch circuit switches the high voltage source VDD high connected to the power supply terminal of the high voltage circuit; when the output terminal of the high threshold reset circuit outputs the second level or turns off the output, the switch circuit cuts off the high voltage source VDD high connection to a power supply terminal of the high voltage circuit; The low threshold reset circuit has its input connected to the low voltage source VDD low connected, and its output end is connected to the power supply end of the low voltage circuit. When the low voltage source VDD low The voltage is greater than the low threshold voltage Vth low When the low threshold reset circuit resets the low voltage source VDD low connected to the power supply terminal of the low voltage circuit; when the low voltage source VDD low The voltage is less than the low threshold voltage Vth low When the low threshold reset circuit cuts off the low voltage source VDD low Connection to the power supply terminal of the low voltage circuit.

2. The power-off protection circuit of the dual voltage threshold circuit according to claim 1, characterized in that: The high voltage source VDD high The voltage value of the low voltage source VDD low Voltage value; The low voltage source VDD low The voltage value of > the high threshold voltage Vth high The voltage value of > the low threshold voltage Vth low Voltage value.

3. The power-off protection circuit of the dual voltage threshold circuit according to claim 2, characterized in that: The switch circuit includes a first MOS transistor PM1 and a second MOS transistor NM1. The first connection end of the first MOS transistor PM1 is connected to the first connection end of the switch circuit, the second connection end is connected to the second connection end of the switch circuit, and the control end is connected to the high voltage source VDD. high connected; A first connection end of the second MOS transistor NM1 is connected to the control end of the first MOS transistor PM1 , a second connection end thereof is grounded, and a control end thereof is connected to the control end of the switch circuit.

4. The power-off protection circuit of the dual voltage threshold circuit according to claim 3, characterized in that: When the output terminal of the high threshold reset circuit outputs a first level, the first MOS transistor PM1 and the second MOS transistor NM1 are both turned on; When the output terminal of the high threshold reset circuit outputs the second level or turns off the output, both the first MOS transistor PM1 and the second MOS transistor NM1 are turned off.

5. The power-off protection circuit of the dual voltage threshold circuit according to claim 4, characterized in that: The first MOS transistor PM1 is a PMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the first MOS transistor MP1 are respectively the source, the drain and the gate of the PMOS transistor; The second MOS transistor NM1 is an NMOS transistor, and the first connection terminal, the second connection terminal and the control terminal of the second MOS transistor NM1 are respectively the drain, the source and the gate of the NMOS transistor; The first level output by the high threshold reset circuit is a high level, and the second level output by the high threshold reset circuit is a low level.

6. The power-off protection circuit of the dual voltage threshold circuit according to claim 5, characterized in that: The switch circuit further includes a second resistor R2, which is connected between the control terminal and the ground terminal of the second MOS transistor NM1; When the low voltage source VDD low The voltage is less than the high threshold voltage Vth high , the high threshold reset circuit turns off the output.

7. The power-off protection circuit of the dual voltage threshold circuit according to claim 5, characterized in that: The switch circuit further includes a first resistor R1 connected to the control terminal of the first MOS transistor PM1 and a high voltage source VDD. high between.

8. A dual voltage threshold circuit, characterized in that: It includes: High voltage circuits; Low voltage circuits; A power-off protection circuit as described in any one of claims 1 to 7.

Images