CN105823955B - Detection circuit - Google Patents

Abstract

Detection circuit avoids error detection of the detection circuit after power supply just starts.As solution, the load open-circuit detection circuit that detection circuit includes the output transistor between voltage input-terminal and output voltage terminals and detected to the open circuit for the load connecting with output voltage terminals, the structure that there is the output circuit of load open-circuit detection circuit the 1st transistor and the 2nd transistor to be connected in series, 1st transistor and output transistor common gate connection, the grid of 2nd transistor is entered the signal for indicating to detect load open circuit, and the 1st transistor is configured to the cut-off when output transistor ends.

Description

Detection circuit

Technical field

The present invention relates to the detection circuits detected to the open circuit of the load connected.

Background technique

Fig. 6 is previous detection circuit.Previous detection circuit has voltage input-terminal 401, output voltage terminals 402, the load open circuit of the open circuit for the load that output transistor 403, control circuit 404, detection are connect with output voltage terminals 402 The output terminal 406 of detection circuit 405 and load open-circuit detection circuit 405.

Control circuit 404 carries out conduction and cut-off control to output transistor 403.Load open-circuit detection circuit 405 is detecting When the open circuit for the load connecting out with output voltage terminals 402, detection signal is exported to output terminal 406.

In load open-circuit detection circuit 405, in order to detect the open circuit for the load connecting with output voltage terminals 402, often The method for being often used the electric current of monitoring output transistor 403.For example, between voltage input-terminal 401 and output transistor 403 Resistance 410 is set, is determined using the voltage that its both ends generates.In the open circuit for the load being connect with output voltage terminals 402 Under state, electric current should be unable to be flowed through in output transistor 403, therefore detection connects with output voltage terminals 402 as described above The open circuit of the load connect.

Patent document 1: Japanese Unexamined Patent Publication 6-289087 bulletin

Output transistor 403 in order to correspond to load that output voltage terminals 402 are connect and flow through larger current, element Size is larger, input capacitance is also larger.In order to output transistor 403 biggish input capacitance carry out charge/discharge and into The control of row conduction and cut-off, needs the time in the physical sense, therefore output transistor 403 is difficult to rise in the power supply of detection circuit On state is immediately become when dynamic.Therefore, after the power supply of detection circuit just starts, output transistor 403 shows cut-off shape State does not generate voltage in resistance 410 although not becoming the open-circuit condition of load actually.

Therefore, in previous detection circuit shown in Fig. 6, exist after the power supply of detection circuit just starts, resistance The voltage generated in 410 is smaller and the problem of being supported 405 misinterpretation of open detection circuit.

Summary of the invention

The present invention provides a kind of electricity avoided in detection circuit precisely in order to eliminate above such problem and propose Source just start after error detection detection circuit.

In order to solve conventional problems, detection circuit of the invention is constituted as follows.

Detection circuit include output transistor between voltage input-terminal and output voltage terminals and to The load open-circuit detection circuit that the open circuit of the load of output voltage terminals connection is detected, the output of load open-circuit detection circuit The structure that there is circuit the 1st transistor and the 2nd transistor to be connected in series, the 1st transistor and output transistor common gate connection, should The grid of 2nd transistor is entered the signal for indicating to detect load open circuit, and the 1st transistor is configured to end in output transistor When end.

Detection circuit according to the present invention is capable of providing the detection circuit for avoiding the error detection after power supply just starts.

Detailed description of the invention

Fig. 1 is the explanatory diagram for showing the detection circuit of present embodiment.

Fig. 2 is another explanatory diagram for showing the detection circuit of present embodiment.

Fig. 3 is another explanatory diagram for showing the detection circuit of present embodiment.

Fig. 4 is another explanatory diagram for showing the detection circuit of present embodiment.

Fig. 5 is the explanatory diagram for showing an example of the potential circuit of detection circuit of present embodiment.

Fig. 6 is the explanatory diagram for showing previous detection circuit.

Label declaration

101,102,301: voltage source；103: comparator；106,107: current source；302: amplifier；404: control circuit； 405: load open-circuit detection circuit.

Specific embodiment

Hereinafter, being illustrated referring to attached drawing to present embodiment.

Fig. 1 is the explanatory diagram for showing the detection circuit of present embodiment.

The detection circuit of present embodiment has that voltage input-terminal 401, output voltage terminals 402, to be connected to voltage defeated Enter output transistor 403 between terminal 401 and output voltage terminals 402, control circuit 404, load open-circuit detection circuit 405, the output terminal 406 and resistance 410 of load open-circuit detection circuit 405.Load open-circuit detection circuit 405 is to defeated with voltage The open circuit for the load that terminal 402 connects out is detected.Resistance 410 generates and should to monitor the electric current of output transistor 403 The corresponding voltage of electric current.

Load open-circuit detection circuit 405 has potential circuit 101, voltage source 102, comparator 103, transistor 104, crystal Pipe 105 and current source 106.The voltage of VSS benchmark of the generation of potential circuit 101 based on the voltage generated at the both ends of resistance 410 VSIG.Voltage source 102 generates reference voltage VREF.Comparator 103 is compared voltage VSIG with reference voltage VREF, control The conduction and cut-off of transistor 104.Transistor 105 and output transistor 403 are by common gate connection, and transistor 105 and transistor 104 are connected in series.Current source 106 and the transistor 104 and 105 being connected in series are connected in series, tie point and output terminal 406 Connection.Transistor 104,105 and current source 106 constitute the output circuit of load open-circuit detection circuit 405.

Fig. 5 is the circuit diagram for showing an example of potential circuit 101.Potential circuit 101 shown in fig. 5 has input terminal 300 and 301, amplifier 302, resistance 304 and 305, transistor 303 and output terminal 306.Input terminal 300 and resistance 410 The terminal of 401 side of voltage input-terminal connects.Input terminal 301 is connect with another terminal of resistance 410.

Potential circuit 101 will press resistance to the voltage at 410 both ends of resistance on the basis of the voltage of voltage input-terminal 401 Than the voltage after multiplication, the voltage VSIG as VSS benchmark is exported to terminal 306.

In addition, as long as potential circuit 101 generates the electricity of the VSS benchmark based on the voltage generated at the both ends of resistance 410 The structure for pressing VSIG, is not limited to the circuit.

Then, the movement of the detection circuit of present embodiment is illustrated.Control circuit 404 is to output transistor 403 Carry out conduction and cut-off control.Load open-circuit detection circuit 405 is detecting opening for the load connecting with output voltage terminals 402 Lu Shi, by detecting signal (high level) output to output terminal 406.The voltage generated in resistance 410 is based on output transistor 403 electric current, therefore under the open-circuit condition for the load being connect with output voltage terminals 402, it should not in output transistor 403 Electric current can be flowed through, therefore by determining that the voltage generated in resistance 410 detects the open circuit of load below a certain numerical value.

Voltage VSIG works as the smaller Shi Bian little of voltage generated in resistance 410 based on the voltage generated in resistance 410. Therefore, under the open-circuit condition for the load connecting with output voltage terminals 402, voltage VSIG becomes smaller.Comparator 103 is being determined as When VSIG < VREF, conducting control is carried out to transistor 104.

About output transistor 403, since in order to flow through larger current, component size is larger, input capacitance is also larger, Therefore it is not connected immediately in the power activation of detection circuit.Here, transistor 105 in the same manner as output transistor 403, is set Being set to becomes off state in the power activation of detection circuit.That is, in the power activation of detection circuit and output transistor 403 be off state when, transistor 105 is also switched off, therefore, even if by the output of comparator 103 make transistor 104 conducting, Also detecting signal is not exported to the output terminal 406 of load open-circuit detection circuit 405.

As described above, detection circuit according to the present embodiment is capable of providing and avoids detection circuit in electricity Source just start after error detection detection circuit.

As long as in addition, transistor 105 is after the power supply of detection circuit just starts according to the control of control circuit 404 certainly Signal carries out movement identical with output transistor 403, and structure and characteristic is not limited.For example, transistor 105 with it is defeated The type of transistor 403 is identical out, and has same threshold.

In addition, transistor 105 is set as single transistor but it is also possible to be being inserted into connection in the source electrode of transistor 105 Thus the transistor of diode or the structure for being set as Darlington connection make the threshold value of transistor 105 be higher than output transistor 403。

In addition, transistor 105 can also intervene electricity not necessarily with 403 common gate connection of output transistor between the two (voltage level shift) grade is changed in flat turn.Level conversion grade can be for example made of source follower amplifying stage.In the feelings Under condition it is understood that compared with output transistor 403, the size of the gate source voltage of transistor 105 becomes smaller, therefore can more may be used Error detection is avoided by ground.

Here, the detection circuit of Fig. 1 when control circuit 404 ends output transistor 403, can not export expression load Open-circuit condition signal.For example, when load open-circuit detection circuit 405 detects the open circuit of load, ambient temperature liter sometimes Height, so that control circuit 404 carries out cut-off control to output transistor 403.

Fig. 2 is another explanatory diagram for showing the detection circuit of present embodiment.With Fig. 1's the difference lies in that new tool There is transistor 110 that is in parallel with transistor 105, being controlled by control circuit 404.Control circuit 404 for example according to it is above-mentioned that Transistor 110 is connected in the state of sample, thus it enables that 105 invalidation of transistor, therefore, even if output transistor 403 is in Off state also can export detecting signal to the output terminal 406 of load open-circuit detection circuit 405.

Fig. 3 is another explanatory diagram for showing the detection circuit of present embodiment.It is different from the detection circuit of Fig. 1 it Be in output circuit in, load open-circuit detection circuit 405 by be connected in series transistor 104 and current source 106, be connected in series Transistor 105 and current source 107 and "AND" circuit 201 constitute.Such structure can also obtain the detection circuit with Fig. 1 Same effect.

Furthermore, it is possible to be illustrated, as long as being related to being made of the condition of circuit the logic gate or combinations thereof that pressure secures output, Such as by having used the circuit appropriate of OR circuit to constitute circuit, it may have same effect.

Fig. 4 is another explanatory diagram for showing the detection circuit of present embodiment.Circuit with Fig. 2 is again it is by brilliant The circuit that body pipe 202 and transistor 105 are arranged in parallel, can obtain effect same as the circuit of Fig. 2.

In addition, load open-circuit detection circuit 405 is illustrated according to circuit shown in Fig. 1 to Fig. 4, but this is only one Example, as long as same effect can be obtained, does not limit embodiment.

In the above description, the level of each output is provided according to high level and low level for convenience, but It does not need to be particularly limited to.

Claims (5)

1. a kind of detection circuit, with voltage input-terminal, output voltage terminals, it is set to the voltage input-terminal and described Output transistor between output voltage terminals, the control output transistor control circuit, to the voltage output end The load open-circuit detection circuit that is detected of open circuit of the load of son connection, the detection circuit be characterized in that,

The output circuit of the load open-circuit detection circuit has the structure of the 1st transistor and the series connection of the 2nd transistor, this 1 transistor and the output transistor common gate connection, the grid of the 2nd transistor are entered the letter for indicating to detect load open circuit Number,

1st transistor ends when the output transistor ends.

2. detection circuit according to claim 1, which is characterized in that

1st transistor is identical as the output transistor type and the transistor with same threshold or more high threshold.

3. detection circuit according to claim 1, which is characterized in that

The grid of the output transistor is connect with the grid of the 1st transistor via level conversion grade.

4. detection circuit according to claim 3, which is characterized in that

The level conversion grade is source follower amplifying stage.

5. detection circuit described in any one according to claim 1~4, which is characterized in that

The detection circuit has and the 1st coupled in parallel and the 3rd transistor that is controlled by the control circuit.