Circuit for converting an AC or a DC electrical input into a DC electrical output

A circuit converts an AC or DC electrical input applied between first and second input leads into a DC output applied to a load via first and second output leads. Four thyristors have their anodes respectively connected to one of the first and second input leads or one of the first and second output leads. Cathodes of two thyristors are connected to the first and second output leads while cathodes of two other thyristors are connected to the first and second input leads. Gates of each thyristor are connected to respective unidirectional switches that open and close at the same time. When closed, the unidirectional switches polarize the gates. Thyristors having a positive voltage on their anodes apply this voltage to the first output lead to power the load. Thyristors having a negative voltage on their cathodes transmit return current from the load to the first or second input lead.

TECHNICAL FIELD

The present disclosure relates to the field of power electronics. More specifically, the present disclosure relates to a circuit for converting an AC or a DC electrical input into a DC electrical output.

BACKGROUND

Electrical power converters are commonly used all types of electrical applications. Many applications require the provision of direct current (DC) voltage. When an electrical grid is not readily available, fuel powered electrical generators may be used.

For example, electromagnets are used in metal recycling plants, commonly called wrecking yards or scrapyards. These magnets are held on vehicle-mounted cranes that travel throughout large fields where metal parts, for example wrecked cars, are stacked on top of one another. Large metal pieces are collected using those magnets. To this end, a magnet is powered with a DC voltage and attracts metal that can be moved around. Cranes on which these magnets are mounted need to move around large fields and, for that reason, cannot usually rely on the electrical grid to provide power. Electrical generators are mounted on the vehicles that support the cranes. DC voltage at a first polarity is used to energize the magnet. Simply removing the DC voltage from the magnet would cause a slow depolarization of the metal attracted by the magnet, the metal remaining attached for several seconds. Usually, a DC voltage of an opposite polarity is provided to the magnet, causing a rapid release of the metal. There is therefore a need for the provision of output power at both opposite polarities at different times.

Alternating current (AC) generators are usually less expensive and require less maintenance than DC generators. The provision of DC voltage when the source is an AC generator requires the use of AC to DC converters.

When DC generators are used, voltage is usually referenced to a neutral, or ground reference, but that is not always the case. A DC generator may provide a positive voltage or a negative voltage on one output lead, and a ground reference on another output lead. Another DC generator may at once provide a positive voltage on one lead and a negative voltage or another lead. DC to DC conversion becomes necessary to ensure that DC power is provided according to the needs of a particular application.

In the field, provision of a DC output voltage converted from any one of a DC or AC input power source may cause challenges and distinct conversion equipment may be used for adaptation to the type of available generator. In the particular case when DC electrical power is provided by a generator, an accidental inversion of leads having positive and negative voltages may lead to the destruction of the converter or to other safety hazards.

Therefore, there is a need for improved power conversion circuits that alleviate or overcome the above described deficiencies.

SUMMARY

According to the present disclosure, there is provided a circuit for converting an electrical input into a DC output, comprising: a first input lead and a second input lead adapted for receiving an electrical input between the first and second input leads, the electrical input being one of a positive DC voltage, a negative DC voltage and an AC voltage; a first output lead and a second output lead adapted for providing the DC output to a load; a first thyristor having an anode connected to the first input lead and a cathode connected to the first output lead; a second thyristor having a cathode connected to the first input lead and an anode connected to the second output lead; a third thyristor having an anode connected to the second input lead and a cathode connected to the first output lead; a fourth thyristor having a cathode connected to the second input lead and an anode connected to the second output lead; a first unidirectional switch connecting the first input lead to a gate of the first thyristor; a second unidirectional switch connecting the second output lead to a gate of the second thyristor; a third unidirectional switch connecting the second input lead to a gate of the third thyristor; a fourth unidirectional switch connecting the second output lead to a gate of the fourth thyristor; and a controller adapted to cause the first, second, third and fourth unidirectional switches to open and close at the same time.

According to the present disclosure, there is also provided the circuit further comprising a fifth thyristor having an anode connected to the second input lead and a cathode connected to the second output lead; a sixth thyristor having a cathode connected to the second input lead and an anode connected to the first output lead; a seventh thyristor having an anode connected to the first input lead and a cathode connected to the second output lead; an eighth thyristor having a cathode connected to the first input lead and an anode connected to the first output lead; a fifth unidirectional switch connecting the second input lead to a gate of the fifth thyristor; a sixth unidirectional switch connecting the first output lead to a gate of the sixth thyristor; a seventh unidirectional switch connecting the first input lead to a gate of the seventh thyristor; and an eighth unidirectional switch connecting the first output lead to a gate of the eighth thyristor; the controller being further adapted to cause the fifth, sixth, seventh and eighth unidirectional switches to open and close at the same time, and prevent concurrent closing of the first and fifth unidirectional switches.

The foregoing and other features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.

Like numerals represent like features on the various drawings.

DETAILED DESCRIPTION

Various aspects of the present disclosure generally address one or more of the problems of providing DC power from various AC or DC sources.

The present disclosure introduces a circuit that converts an electrical input having any polarity, including a positive DC input, a negative DC output, or an AC input, into a DC output at a first polarity. To generate the DC output at the first polarity, the input power is applied via a pair of input leads to a bank of four (4) thyristors that are also connected to a pair of output leads. Four (4) unidirectional switches that are each connected to the gates of a respective one of the four (4) thyristors are closed when a command is received by the circuit for the provision of the DC output at the first polarity. A configuration of the connections between the input leads, the thyristors and their gates, the unidirectional switches and the output leads ensures that DC voltage at the first polarity is present on the output leads when the unidirectional switches are closed. To this end, only two (2) of the four (4) thyristors are placed in conduction, depending on the polarities at the input leads, so that the proper voltage is applied at the output leads.

Optionally, to generate a DC output at a second polarity opposite from the first polarity, the input power may also be applied via the pair of input leads to another bank of four (4) thyristors that are controlled to operate in a reverse fashion. A processor of the circuit ensures that commands for the provision of the DC output at the first and second polarities are mutually exclusive.

In an example application, the DC output at the first polarity is used to activate an electromagnet and DC output at the second polarity is used to briefly deactivate the electromagnet. In another example application, the DC output at the first polarity is used to cause a DC motor to rotate in a first direction and the DC output at the second polarity is used to cause the DC motor to rotate in a second direction, opposite from the first direction.

Referring now to the drawings,FIG. 1is a high-level block diagram of a circuit adapted to convert alternative or direct current into a direct current supply according to an embodiment. A circuit1000includes a power input module1100, a low voltage power supply module1200, a relay breaker1300, a processing unit1400, or controller, an external signal connector1500, a capacitor bank1600, a thyristor driver unit1700and an output power module1800. A load1900receives DC power from the circuit1000.

Embodiments of the various modules of the circuit1000are described inFIGS. 2 to 8. The modules as illustrated implement various features that are specific to a particular application, for example when the load1900powered by the circuit1000is an electromagnet. The electromagnet is activated when energized at a first DC polarity. When a metallic load is held by the electromagnet, the load itself becomes magnetized. Deactivation of the electromagnet would eventually lead to release of the metallic load after a few seconds. The electromagnet may be deactivated (being in fact activated at a reverse magnetic polarity) when briefly energized at a second, opposite DC polarity, causing a rapid release of the metallic load. Although the examples disclosed herein relate to using the circuit1000for activating and deactivating an electromagnet, the circuit1000may alternatively be used for driving other loads, for example a DC motor. Distinct DC polarities may be output from the circuit1000for rotating the DC motor in forward and reverse directions. A simpler version of the circuit1000may output DC power in a single polarity for some applications.

The shown modules implement a variety of timing and protection features that are not directly related to the conversion of AC or DC input power into DC output power. For that reason, some detailsFIGS. 2 to 9are not described. The person of ordinary skill in the art of electronic controls and in the art of power electronics will be able to appreciate the use of each component of the illustrated modules.

FIG. 2is a detailed circuit diagram of the power input module ofFIG. 1. The power input module1100includes an external connector1102adapted to receive electric power in the form of an AC voltage or in the form of a DC voltage having any polarity. The input may for example have a range of 120 to 500 volts AC or 170 to 700 volts DC, according to the needs of an application for the circuit1000. Fuses1104and1106and metal oxide varistors (MOV) diodes1108,1110and1112provide overvoltage and overcurrent protection for the circuit1000. The relay breaker1300is also shown onFIG. 2. An input1302of the relay breaker1300is connected to the processing unit1400for control of the breaker1300. Current flows out of the power input module1100and to the power output module1800for power delivery, via pins1,2of the connector1102, when the relay breaker1330is closed. The voltage from the external connector1102is also present on pins12, and4,5of a connector1114linked to the low voltage power supply module1200, for example via a flat cable. The connector1114is an internal connector; all connectors mentioned herein are internal to the circuit1000unless otherwise mentioned. The low voltage power supply module1200returns a 16-volt DC supply received by the power input module1100at pins9,10of the connector1114and fed to the processing unit1400via another connector1116.

An ammeter1118measures a current flowing through the power input module1100to the relay breaker1300and further towards the output power module1800. A comparator circuit1120provides a measurement of the input power voltage. A phase detector1122determines whether the input power is in the form or AC or DC current. Current measurement from the ammeter1118, voltage measurement from the comparator circuit1120and AC/DC detection are applied on another connector1124that is connected to the processing unit1400.

FIG. 3is a detailed circuit diagram of the low voltage power supply module ofFIG. 1. The low voltage power supply module1200includes a connector1202linked to the connector1114of the power input module1100. An input AC or DC voltage that may vary over a broad range, for example between +/−120 to 500 volts, is received on pins6,7and9,10of the connector1202. The low voltage power supply module1200converts this input voltage into a 16-volt DC supply that is applied on pins1,2of the connector1202for the benefit of the power input module1100and of the processing unit1400. A precise 16-volts output is facilitated in part by the use of a pulse width modulation controller1204and of a precision programmable reference unit1206. A transformer1208and an optocoupler1210ensure decoupling between the input and output voltages present on the connector1202. Other components of the low voltage power supply module1200are conventional and the skilled reader will be able to reproduce this module or substitute therefor another module having equivalent capabilities. For that reason, they are not described further herein.

FIG. 4is a detailed circuit diagram of the processing unit ofFIG. 1. Primary functions of the processing unit1400are controlled by a microprocessor1402, which is for example a PIC18F26K20 microprocessor from Microchip Technology Inc. The processing unit1400includes six (6) internal connectors used to provide connections, for example using flat cable, to other components of the circuit1000.

A connector1404receives the 16-volt DC supply at pins3,4from the connector1116of the power input module1100. The circuit1400is powered by this 16-volt DC supply and is therefore independent from the voltage applied at the external connector1102of the power input module1100. The circuit1400is also independent from a rated current output of the circuit1000. Pins1,2of the connector1116are connected to the output1302of the relay breaker1300. The processing unit1400may cause opening of the relay breaker1300by sending a command via the pins1,2of the connector1116in case of a fault. The processing unit1400is informed of possible overload of the output power module1800via pins5,6of the connector1404.

A connector1406is linked to the connector1124of the power input module1100and receives therefrom the current measurement, the voltage measurement and the AC/DC detection. These measurements are provided to the microprocessor1402, either directly or through various amplifiers of the processing circuit1400.

A connector1408is linked to the external connector1500. Depending on external equipment connected to the circuit1000via the external connector1500, the connector1408may receive on pins7,8, from an external terminal having a display, commands that are compliant with a controller area network (CAN) standard. Alternatively, the connector may receive conventional commands on pins5,6. In the case of CAN-compliant commands, pin7is activated when an operator desires to activate an electromagnet powered by the circuit1000. Pin8is activated when the operator desires to deactivate the electromagnet. These commands are applied to a CAN controller1410, which is for example a MCP2551 from Microchip Technology Inc. The CAN controller1410buffers these commands and applies them to the microprocessor1402. If CAN-compliant commands are not available, pins5,6respectively receive activation and deactivation commands that are used to activate a RelayA1412or a RelayB1414. The microprocessor1402either treats signals from the CAN controller1410or from the RelayA1412and RelayB1414to control operation of the electromagnet. Pins1,3,4of the connector1408provide signals that are used for programming of the microprocessor1402. Pins2,9,10of the connector1408respectively provide 5-volt DC reference, a ground reference and a 16-volt DC reference to the external connector1500.

A connector1416is linked to the capacitor bank1600to temporarily maintain the processing unit1400and the thyristor driver unit1700energized in case of a loss of input power into the power input module1100. The processing unit1400detects the loss of input power and adapts its control of the circuit1000while energized by the capacitor bank1600. For example, when the load1900is an electromagnet, depolarization of the electromagnet at the time of the input power loss causes current to return from the electromagnet to the output power module1800. The processing unit1400then causes the output power module1800to dissipate energy returning from the electromagnet.

Connectors1418and1420are both connected to the thyristor driver unit1700and to the output power module1800. The connector1418is used in an implementation to control activation of an electromagnet while the connector1420is used to control deactivation of the electromagnet.

On the connector1418, a 12-volt DC feed is applied on pin8. A “lift” signal to activate the electromagnet is applied on pin10. The “lift” signal has a voltage lower than 12 volts, for example 0 volt. Signals received from the thyristor driver unit1700on pins1,3,5,7,9,11,13,15of the connector1418are directly forwarded to pins9,10,12,16,15,10,13respectively, of a connector1422that is linked to the output power module1800. Pins3,13of the connector1418are both linked to pin10of the connector1422. On the connector1420, a 12-volt DC feed is applied on pin8. A “down” signal to deactivate the electromagnet is applied on pin10. The “down” signal also has a voltage lower than 12 volts Signals received from the thyristor driver unit1700on pins1,3,5,7,9,11,13,15of the connector1420are directly forwarded to pins respectively3,8,2,1,5,6,8,7, of the connector1422. Pins3,13of the connector1420are both linked to pin8of the connector1422. How these connections allow control of the thyristor driver unit1700and of the1800will become apparent in the following description ofFIGS. 6, 7 and 9.

Other components of the processing unit1400provide various control and protection functions for the circuit100. The skilled reader will be able to reproduce these functions using the same or components or using components having equivalent capabilities. For that reason, they are not described further.

FIG. 5is a detailed circuit diagram of the capacitor bank ofFIG. 1. The capacitor bank1600comprises a plurality of large capacitors1602connected in parallel, with resistors1604to prevent overcurrent flowing form the capacitor bank1600. The capacitor bank1600is linked to the connector1416of the processing unit1400via its own connector1606. The capacitor bank1600is trickle charged by the processing unit1400in normal operation. In of a loss of input power, the capacitor bank1600provides backup power to the processing unit1400for a short period, for example for 30 seconds. A fuse1608protects the capacitor bank1600from overcurrent.

FIG. 6is a detailed circuit diagram of the thyristor driver unit ofFIG. 1. In the shown embodiment, the thyristor driver unit1700comprises two (2) identical driver portions1710and1760. The driver portion1710includes a connector1712linked to the connector1418of the processing unit1400and is put in operation when a command to activate the electromagnet is received. The driver portion1760includes a connector1762linked to the connection1420of the processing unit1400and is put in operation when a command to deactivate the electromagnet is received. It should be understood that a single driver portion may be used in a circuit used to convert AC or DC power into DC power for applications outputting a single DC power polarity. Because the driver portions1710and1760are identical in the shown embodiment, only the driver portion1710is described in details.

Pins8,10of the connector1712are respectively linked to the pins8,10of the connector1418. The 12-volt DC feed is applied on pin8. When the “lift” signal is applied on the pin10, current flows from the pin8through a light emitting diode (LED)1714which provides a visible indication that DC power at the first polarity is available. The current also flows through LEDs1716,1718,1720and1722of optocoupled solid state relays (SSR)1724,1726,1728and1730, which are respectively connected in series with diodes1732,1734,1736and1738. Each pair formed by one of the SSRs1724,1726,1728and1730connected in series with one of the diodes1732,1734,1736and1738forms a respective unidirectional switch that either blocks any current, when open, or allows current to flow in a single direction, when closed.

When current flows through the LEDs1716,1718,1720and1722, the SSRs1724,1726,1728and1730become conductive. The diodes1732,1734,1736and1738ensure that Current may only flow through the SSRs when the corresponding diodes are correctly polarized. For example, if the voltage at pin3of the connector1712is higher than the voltage at pin1, the diode1732and the SSR1724become conductive, provided that the SSR1724is energized by the LED1716. Likewise, if the voltage at pin7of the connector1712is lower than the voltage at pin5, the diode1734blocks any conduction through the SSR1726, even when SSR1726is energized by the LED1716.

FIG. 7is a detailed circuit diagram of the thyristor bank in a power output unit ofFIG. 1. The power output unit1800includes four (4) pairs of thyristors forming a thyristor bank. The thyristor bank includes pairs of thyristors1802(T1, T2) and1804(T3, T4) that output, via output leads1820,1822and1824, DC power applied at the first polarity to energize the electromagnet when the “lift” signal is received at the processing unit1400. Pairs of thyristors1806(T5, T6) and1808(T7, T8) output DC power applied at the second, reverse polarity to briefly de-energize the electromagnet when the “down” signal is received at the processing unit1400. Instead of the electromagnet, the load attached to the circuit1000may include a DC motor. Two (2) pairs of thyristors (T1, T2, T3, T4) may be used if the DC motor is to be operated in a single direction. The four (4) pairs of thyristors may be used when forward and reverse operation of the DC motor is desired.

Leads1810are connected to pins1,2of the connector1102of the power input module1100and receive therefrom the input voltage applied at the input power module1100, provided that the1300is not opened and that the fuses1104,1106and that the MOV diodes1108,1110do not detect overcurrent or overvoltage. The input voltage present on the leads1810may be in the form of AC voltage or in the form of DC voltage of any polarity.

The input voltage is applied on inputs1and2of the pairs of thyristors1802,1804,1806and1808.

Depending on a polarity of a DC input voltage present on the leads1810, or depending on an instantaneous polarity of an AC input voltage present on the leads1810, positive or negative voltages may be present on the inputs1and2of each pair of thyristors1802,1804,1806and1808. Considering the pair of thyristors1802and1804that are intended to provide a DC output at the first polarity, the input1of the pair of thyristors1802has an opposite polarity when compared to the input2of the pair of thyristors1804, and vice-versa.

A connector1818is linked to the connector1422of the processing unit1400, the connector1422being in turn linked to the SSRs1724,1726,17281730of the driver portion1710via the connectors1418and1712and to further SSRs of the driver portion1760via the connectors1420and1762.

FIGS. 8aand 8bshow a combination of elements of the processing unit, of the thyristor driver unit and of the output power module, different voltages being applied to the output power module on each ofFIGS. 8aand 8b. The impact of the input voltage on the leads1810will only be described for the thyristor pairs1802(T1, T2) and1804(T3, T4) while a “lift” command is applied on the1750to close the SSRs1724,1726,1728and1730.

Summarily stated, a first input lead1810aand a second input lead1810bare adapted for receiving the electrical input from the power input module1100, via the relay breaker1300. The electrical input may be any one of a positive DC voltage, a negative DC voltage and an AC voltage. DC output is provided to the load1900between a first output lead1824and a second output lead1820. A first thyristor T1has an anode (A) connected to the first input lead1810aand a cathode (K) connected to the first output lead1824. A second thyristor T2has a cathode (K) connected to the first input lead1810aand an anode (A) connected to the second output lead1820. A third thyristor T3has an anode (A) connected to the second input lead1810band a cathode (K) connected to the first output lead1824. A fourth thyristor T4has a cathode (K) connected to the second input lead1810band an anode (A) connected to the second output lead1820. A first unidirectional switch (the diode1734and the SSR1726) connects the first input lead1810ato a gate (G) of the first thyristor T1. A second unidirectional switch (the diode1732and the SSR1724) connects the second output lead1820to a gate (G) of the second thyristor T2. A third unidirectional switch (the diode1736and the SSR1728) connects the second input lead1810bto a gate (G) of the third thyristor T3. A fourth unidirectional switch (the diode1738and the SSR1730) connects the second output lead1820to a gate (G) of the fourth thyristor T4. The processing unit1400causes the first, second, third and fourth unidirectional switches to open and close at the same time by applying a difference of potential on pins8,10of the connector1712of the thyristor driver unit1700.

Optionally, in the embodiment as shown, a fifth thyristor T5has an anode connected to the second input lead1810band a cathode connected to the second output lead1820. A sixth thyristor T6has a cathode connected to the second input lead1810band an anode connected to the first output lead1824. A seventh thyristor T7has an anode connected to the first input lead1810aand a cathode connected to the second output lead1820. An eighth thyristor having a cathode connected to the first input lead1810aand an anode connected to the first output lead1824. The thyristors T5, T6, T7and T8are respectively connected to four (4) unidirectional switches of the driver portion1760. The processing unit1400causes the unidirectional switches of the driver portion1760to open and close at the same time by applying a difference of potential on pins8,10of the connector1762of the thyristor driver unit1700. The processing unit1400prevents concurrent closing of the unidirectional switches of the distinct driver portions1710and1760.

FIGS. 8aand 8bdiffer in the polarity of the voltage applied on the leads1810. OnFIG. 8a, a voltage present on the lead1810ais higher than a voltage present on the lead1810b. For example, the voltage on the lead1810bmay be negative or zero while the voltage in the lead1810ais greater than zero. The input voltages may be constant (DC) or variable (AC). In the case of an AC voltage,FIG. 8arepresents an instant when the voltage at the lead1810ais higher than the voltage at the lead1810bwhileFIG. 8brepresents a next instant when the voltage at the lead1810ais lower than the voltage at the lead1810b.

ConsideringFIG. 8ainitially, the positive voltage from the lead1810ais applied on the anode of T3, on the cathode of T4and on the anode of the diode1736, which becomes conductive. This causes the application of the positive voltage on the gate of T3, which also becomes conductive so that the positive voltage from the lead1810ais now present on the output lead1824, which is connected to the load1900. The output lead1820is at a lower voltage than that of the output lead1824because it receives current returning from the load1900. That voltage is applied to the anode of T2and to the anode of the diode1732. That voltage is at least marginally higher than the negative voltage from the lead1810bthat is applied on the cathode of T2. This causes the gate of T2to be polarized via the diode1732and the SSR1724, so T2becomes conductive. Current returning from the load1900via the lead1820flows through T2and returns to the lead1810b.

Considering nowFIG. 8b, the positive voltage from the lead1810bis applied on the anode of T1, on the cathode of T2and on the anode of the diode1734, which becomes conductive. This causes the application of the positive voltage on the gate of T1, which also becomes conductive so that the positive voltage from the lead1810bis now present on the output lead1824, which is connected to the load1900. The output lead1820is at a lower voltage than that of the output lead1824because it receives current returning from the load1900. That voltage is applied to the anode of T4and to the anode of the diode1738. That voltage is at least marginally higher than the negative voltage from the lead1810athat is applied on the cathode of T4. This causes the gate of T4to be polarized via the diode1738and the SSR1730, so T4becomes conductive. Current returning from the load1900via the lead1820flows through T4and returns to the lead1810a.

The thyristor pairs1806(T5, T6) and1808(T7, T8) operate in an equivalent manner to output a negative DC voltage when the “down” command is applied. The voltage is lower at the output lead1820than at the output lead1824which receives the current returning from the load1900. The polarity is therefore inversed when compared to the situation ofFIGS. 8aand8b.

When the circuit1000is used to activate and deactivate an electromagnet, the anodes of T6and T8are connected to the output lead1822instead of1824. When the “down” command is applied, the voltage applied to the load by the output lead1820is higher than the voltage on the return lead1822. For example,FIG. 9is a detailed circuit diagram of a final stage of the power output unit ofFIG. 1used to energize an electromagnet. The leads1820,1822and1824shown onFIG. 7extend to a final stage1850that comprises an output connector1852for the circuit1000. When the circuit1000outputs DC power at a positive voltage, for example when the “lift” command is applied, the voltage is higher at the output lead1824than at the output lead1820. A positive DC voltage is therefore present on pin3of the output connector1852, pin6being negative or neutral. Current flows out of pin3of the output connector1852and reaches an electromagnet1902. The current then flows back to the output connector1852at pin4, which is internally connected to pin5. The current flows out of pin5and through a low impedance resistor1854, for example a 0.2 ohm, 400 watts resistor. The current returns to the lead1820via pin6of the output connector1852. A MOV diode1856provides further overvoltage protection between the output leads1824and1820.

When the voltage applied between the output leads1824and1820is released, electromagnetic charges in the electromagnet1902are dissipated at least in part in a residual current flowing between the electromagnet1902, pins4,5of the output connector1852, the resistor1854, pin6of the output connector1852, a diode1858, pin2of the output connector1852and a dissipating resistor1860, for example a 40 ohms, 50 watts resistor. This manner of dissipating the electromagnetic charges in the electromagnet would take several seconds

To deactivate the electromagnet1902more rapidly, electric power is applied between the output leads1822and1820, the “down” command being received at the processing unit1400. At that time, the voltage is higher at the output lead1820than at the output lead1822. Current flows from the lead1820to pin6of the output connector1852, the resistor1854, pins5,4of the output connector1852, the electromagnet1902, a current limiting resistor1862, for example a 120 ohms, 250 watts resistor and pin1of the output connector1852before returning to the lead1822.

The final stage1850ofFIG. 9is specific to the use of the circuit1000for activation and deactivation of the electromagnet1902. To control other types of loads1900, for example a reversible DC motor, positive or negative DC voltages are simply taken from a pair of leads1822/1824and1820as illustrated onFIGS. 8aand8b.

Those of ordinary skill in the art will realize that the description of the circuit for AC or DC to DC conversion are illustrative only and are not intended to be in any way limiting. Other embodiments will readily suggest themselves to such persons with ordinary skill in the art having the benefit of the present disclosure. Furthermore, the disclosed circuit may be customized to offer valuable solutions to existing needs and problems related to conversion of DC or AC electric power into DC power of chosen polarity. In the interest of clarity, not all of the routine features of the implementations of the circuit are shown and described. In particular, combinations of features are not limited to those presented in the foregoing description as combinations of elements listed in the appended claims form an integral part of the present disclosure. It will, of course, be appreciated that in the development of any such actual implementation of the circuit, numerous implementation-specific decisions may need to be made in order to achieve the developer's specific goals, such as compliance with application-, system-, and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the field of power electronics having the benefit of the present disclosure.

The present disclosure has been described in the foregoing specification by means of non-restrictive illustrative embodiments provided as examples. These illustrative embodiments may be modified at will. The scope of the claims should not be limited by the embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole.