TWI409845B - Relay drive circuit - Google Patents

Abstract

A driving circuit for relay is disclosed and has at least one excitation side and at least one switch side which parallel connects a limiting current resistance on an electric power route through which a sudden current passes. A switch unit and a driving period modulation unit are connected to the driving circuit of the excitation side; wherein the switch unit connects the excitation side to determine that the excitation side provides the current passing through. The switch unit conduction is controlled by the driving period modulation unit which pre-sets an over drive period and a holding period. The holding period follows the over drive period. The driving period modulation unit respectively outputs an over drive signal and a holding signal in the over drive period and the holding period to drive the switch unit for conduction. The duty ratio of the switch unit conduction driven by the holding signal drive is lower than the over drive signal to control the lower current in the holding period to maintain the switch side in the conduction state.

Description

Relay drive circuit

A driving circuit for a relay, in particular, a current limiting resistor for suppressing a surge current in a power supply, and driving a relay to bypass the current limiting resistor during a normal operation time of the power supply.

When the power supply is just turned on, since each circuit unit in the power supply needs to reach the working voltage as soon as possible, and the circuit contains many capacitive components, a large inrush current is generated at the initial startup. Therefore, suppressing the on-rush current of the power-on has become a technology that all power supply providers must study, and the most basic method is to set a current-limiting current limiting resistor on the path through which the surge current passes. However, the problem that comes with it is that even if the current limiting resistor suppresses the surge current, the current limiting resistor causes unnecessary power loss when the power supply is operating normally. In the era of focusing on energy efficiency, this Knowing technology is not a long-term strategy.

Based on the above-mentioned conventional techniques, a manufacturer has proposed the Republic of China Patent Certificate No. I301689 "AC-DC converter capable of actively suppressing inrush current", in which a "first suppression unit (20)" is applied to The current path is used to suppress the surge current. The first suppression unit includes a thermistor and an electronic switch SW1 (physically a relay) connected in parallel with the thermistor, and the electronic switch SW1 is normally open, so the current still needs to pass after the power supply is turned on. The thermistor is suppressed. However, when the auxiliary power supply inside the power supply is established, the electronic switch SW1 is driven to be turned on, and the thermistor is bypassed. Similarly, a second suppression unit (30, 30') in this case also utilizes a similar concept, but the second suppression unit is controlled by an output voltage comparison circuit (71) and a logic determination circuit (72). .

Although the above-mentioned conventional technology can avoid the power consumption of the thermistor by bypassing the thermistor, the relay driving circuit bypassing the thermistor also loses part of the work. rate. As shown in the fourth diagram of the I301689 patent, the prior art utilizes a bias power (Vcc) to energize the relay to conduct, and to ensure that the relay is turned on, the voltage typically applied to the relay is slightly greater than the turn-on voltage of the relay itself. After the relay is turned on, the thermistor is bypassed, and the power supply enters a normal operating state. At this time, the conventional power supply still applies the same bias power to keep the relay turned on until the power supply is turned off. Although the thermistor is prevented from consuming power, the relay also has a power loss of 0.6 watt or more when a large voltage is continuously applied, and a resistor or the like connected to the relay is added.

The loss caused by the relay and its driving circuit is less than 5 watts. In the prior art, no corresponding circuit improvement has been made for the loss of the relay. But today's 80 PLUS specification has a stricter distinction between Bronzen, Silver, and Gold, so a loss of 5 watts (or even less than 1 watt) will make a significant difference. Moreover, the service life of the power supply is prolonged, and the energy loss accumulated over a long period of time is considerable. Therefore, the relay is still in need of improvement, in order to strive for high efficiency, energy saving performance.

In view of the above-mentioned prior art, no further energy saving improvement is made for the relay driving circuit, so the purpose of the present invention is to improve the driving circuit of the relay to reduce the loss during the operation of the relay.

The present invention is a relay driving circuit for controlling at least one relay in a power supply, the relay having at least one excitation side and at least one switching side, and the switching side and a current limiting resistor are connected in parallel to the power path through which the surge current passes. on. The driving circuit connected to the excitation side includes a switching element and a driving period modulation unit, wherein the switching element is connected to the excitation side and determines whether the excitation side is for current to pass. The switching element is turned on and otherwise controlled by the driving period modulation unit. The driving period modulation unit presets an over drive period and a holding period, and the sustain period is continued from the overdrive period. After that, the driving cycle modulation unit is in the overdrive period And the sustain period outputting an over drive signal and a holding signal to drive the switching element to be turned on, wherein the duty ratio of the sustain signal driving the switching element to be turned on is less than the overdrive driving a signal to control the conduction state to maintain the switch side in a conducting state with a small current. Since the conventional relay is already designed to have hysteresis characteristics, that is, as long as the excitation side is turned on at the beginning to obtain a large electric excitation drive switch side, the conduction is due to the intrinsic hysteresis characteristic, even on the excitation side. A slight drop in current does not cause the switch side to trip, and the switch side will trip when the current on the excitation side is greatly reduced. Therefore, the technology disclosed in the present disclosure can drive the switching element with a sustain signal having a small duty ratio after the switching signal is ensured to be turned on, thereby providing a smaller current to maintain conduction through the excitation side. This saves the power lost on the relay.

Please refer to FIG. 1 , which is a driving circuit of a relay for controlling at least one relay 4 in a power supply. The power supply and the use and circuit diagram of the relay 4 in the power supply are visible in the above-mentioned conventional knowledge. In the patent, it will not be repeated here. When the power supply is just started, the generated inrush current is suppressed by at least one current limiting resistor 8, and is required to pass through one after ensuring that the nodes of the power supply have been boosted to reach the normal operating voltage. The relay 4 bypasses the current limiting resistor 8. In order to determine when the current limiting resistor 8 needs to be bypassed, a determining unit 1 can be connected to a predetermined determining terminal 10 in the power supply, and the determining whether the determining terminal 10 reaches a predetermined operation The voltage, in turn, determines the timing at which a bypass signal is output. In the present case, the conduction of the relay 4 is controlled by a driving cycle modulation unit 2 and a switching element 3 driven by the driving cycle modulation unit 2, the relay 4 having at least one excitation side 41 and at least one switching side. 42. The switch side 42 is coupled in parallel with a current limiting resistor 8 in a power path through which the surge current passes. A surge current is often generated between the rectifier circuit 6 and the power factor correction circuit 7 in the power supply, so the current limiting resistor 8 is used in the schematic diagram of the present case. The two ends are connected to the rectifier circuit 6 and the power factor correction circuit 7 as an example. The excitation side 41 of the relay 4 is electrically connected to an auxiliary power source 5 through which the supply current is supplied, and the excitation side 41 is connected in parallel with a diode 9 to prevent current from flowing back. Therefore, when the determining unit 1 determines that the determining end point 10 in the power supply has reached the predetermined operating voltage, the bypass signal is output to trigger the driving period modulation unit 2 to further drive the switching element 3 to be turned on. After the switching element 3 is turned on, the current supplied by the auxiliary power source 5 passes through the excitation side 41 of the relay 4 and gradually rises. When the magnetic force generated by the excitation side 41 is large enough, the switch side 42 is turned on and bypassed ( Bypass) the current limiting resistor 8.

The driving period modulation unit 2 presets an over drive period and a holding period, and the driving period modulation unit 2 determines a timing for driving the switching element 3 to be turned on, thereby controlling the flow. The current on the excitation side 41. The driving cycle modulation unit 2 starts the overdrive period after being triggered by the bypass signal, and outputs an over drive signal in the overdrive period to drive the overdrive signal. The switching element 3 is fully turned on, and the overdrive signal causes the switching element 3 to be turned on for a length of time sufficient for the auxiliary power source 5 to generate a large current on the excitation side 41 to ensure that the switch side 42 is turned on and thus bypassed ( Bypass) the current limiting resistor 8 achieves the function of the relay 4 designed in the power supply. After ensuring that the switch side 42 is turned on, the holding period is continued after the overdrive period, and the driving period modulation unit 2 outputs a sustain signal (holding period) during the holding period. The driving element 3 is turned on, wherein the duty signal driving the switching element 3 is turned on by a duty ratio smaller than the over drive signal, resulting in the switching element 3 being intermittently Turning on and turning off, causing the current passing through the excitation side 41 to be suppressed and falling, thereby controlling the holding period to maintain the switching side in an on state with a small current until the holding period The power supply is turned off.

The driving period modulation unit 2 can be divided into a turn-on pulse generator 21 that generates the overdrive signal, a fixed volt-second controller 22 that generates the holding signal, and the turn-on pulse is generated. The device 21 and the fixed volt-second controller 22 are electrically connected to the switching element 3. The bypass signal can simultaneously activate the turn-on pulse generator 21 and the fixed volt-second controller 22, and the turn-on pulse generator 21 generates a fixed square wave overdrive signal for a predetermined period of time after startup. The fixed volt-second controller 22 outputs a holding signal having a high and low level pulse waveform after being triggered, and the two combine to drive the switching element 3 on the power path. In this case, please refer to FIG. 1 and FIG. 2 together, and FIG. 2 is a waveform diagram corresponding to FIG. It can be seen that the waveform of the over drive signal and the holding signal is mixed on the path of driving the switching element 3. In the initial stage of the driving period modulation unit 2, the fixed square wave is overexcited. The over drive signal covers the low level of the holding signal, so that the waveform driving the switching element 3 is a fixed square wave, so that the switching element 3 has a long on-time, and thus the excitation side A sufficient current is passed through 41 to ensure that the switch side 42 is conducting. After the overdrive period of the preset length of time, the overdrive signal is stopped, and the switching element 3 is driven by a pulse-like holding signal, so that the switching element 3 is intermittent. The conduction and the off control suppress the current passing through the excitation side 41, thereby achieving the purpose of reducing power loss. Furthermore, in order to prevent the relay 4 from being turned off, the fixed volt-second controller 22 monitors the voltage of the auxiliary power source 5 and adjusts the duty cycle of the holding signal in a fixed volt-second (V*S) mode (duty Ratio). As shown in FIG. 2, when the switching element 3 is turned on and off depending on the sustain signal (Vd), the pulse width of the sustain signal (Vd) is adjusted as the voltage of the auxiliary power source 5 (Vcc) decreases, reaching a fixed energy. Make sure that relay 4 remains conductive.

In summary, the present example ensures that after the relay 4 is turned on, the relay 4 is maintained at a lower energy by the principle of hysteresis, thereby saving energy for driving the relay 4, so that The power supply is closer to the requirements of the 80 PLUS specification.

While the present invention has been described above in terms of the preferred embodiments thereof, it is not intended to limit the invention, and it is intended that those skilled in the In the invention, the scope of the invention is therefore defined by the scope of the appended claims.

In summary, the present invention enhances the above-mentioned effects in comparison with the conventional creations, and should fully comply with the novelty and progressive statutory innovation patent requirements, and submit an application according to law, and invites you to approve the invention patent application to encourage creation. Feeling the virtues.

1‧‧‧judging unit

10‧‧‧Judgement endpoint

2‧‧‧Drive cycle modulation unit

21‧‧‧Continuation pulse generator

22‧‧‧ Fixed Volt Controller

3‧‧‧Switching elements

4‧‧‧ Relay

41‧‧‧Exciting side

42‧‧‧Switch side

5‧‧‧Auxiliary power supply

6‧‧‧Rectifier circuit

7‧‧‧Power factor correction circuit

8‧‧‧ Current limiting resistor

9‧‧‧ diode

Figure 1 is a circuit diagram of the present invention.

FIG. 2 is a waveform diagram of each node in FIG. 1.

1‧‧‧judging unit

10‧‧‧Judgement endpoint

2‧‧‧Drive cycle modulation unit

21‧‧‧Continuation pulse generator

22‧‧‧ Fixed Volt Controller

3‧‧‧Switching elements

4‧‧‧ Relay

41‧‧‧Exciting side

42‧‧‧Switch side

5‧‧‧Auxiliary power supply

6‧‧‧Rectifier circuit

7‧‧‧Power factor correction circuit

8‧‧‧ Current limiting resistor

9‧‧‧ diode

Claims (4)

A relay driving circuit for driving at least one relay in a power supply, the relay having at least one excitation side and at least one switching side, and the switching side and a current limiting resistor are connected in parallel to a power path through which the surge current passes The excitation side is electrically connected to an auxiliary power source that supplies current through the excitation side, wherein the driving circuit connected to the excitation side includes: a switching element connected to the excitation side and determining whether the excitation side supplies current; And setting a driving period modulation unit, wherein the driving period modulation unit starts to output an overdrive driving signal to drive the switching element to be turned on, wherein the sustain period is subsequent to the overexciting period, the driving The periodic modulation unit outputs a sustain signal to drive the switching element to be turned on, wherein the sustain signal drives the switching element to be turned on for a duty cycle shorter than the overdrive signal to control the sustain current to maintain the current with a smaller current. The switch side is in an on state; and the drive period modulation unit is monitored Auxiliary power supply voltage of the sustain signal and modulating the duty cycle of work. The driving circuit of the relay of claim 1, wherein the driving circuit of the relay further comprises a determining unit determining a timing of outputting a bypass signal according to whether the power supply reaches a predetermined operating voltage, and the driving cycle is adjusted. The variable unit receives the trigger of the bypass signal to initiate the overdrive period. The driving circuit of the relay of claim 1, wherein the driving period modulation unit comprises a conduction pulse generator for generating the overdrive signal, a fixed volt-second controller for generating the sustain signal, and the conducting The pulse generator and the fixed volt-second controller are electrically connected to the switching element. The driving circuit of the relay according to claim 3, wherein the fixed volt-second controller monitors the voltage of the auxiliary power source to adjust the duty cycle of the maintenance signal.