STMicroelectronics STEVAL-IHT008V1 Manuale utente

March 2016

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www.st.com

UM2027

User manual

Inrush current limitation when charging a DC bus capacitor for

IEC 61000-3-3 compliance

Introduction

The STEVAL-IHT008V1 evaluation board limits the inrush current charging a DC bus capacitor so that it

is compliant with the IEC 61000-3-3 standard. This inrush current is based on a soft-start procedure for

the rectifier bridge achieved with a Triac added in series with the mains line, which is controlled through

progressive phase-control during the startup phase.

This solution drastically reduces standby losses as the DC bus can be totally disconnected from the AC

mains when it is not required. The DC bus is easily turned off by turning off the series Triac, without

needing an additional relay to open the circuit in standby.

Steady-state losses are also reduced because NTC resistors, traditionally used to limit inrush current,

are not required; nor are the corresponding relays to bypass them.

This board also demonstrates that AC loads can be driven with an isolated easy-to-design solution by

using the same power supply as the whole system and some opto-transistors which control the AC

switches.

Figure 1: STEVAL-IHT008V1 evaluation board (top view)

Contents

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Contents

1Evaluation board objectives..........................................................3

1.1 What does this evaluation board aim to demonstrate? ....................3

1.2 Principal board blocks......................................................................3

1.3 Targeted applications.......................................................................4

1.4 Main part numbers...........................................................................4

1.5 Operating range and performances .................................................5

1.6 Stand-by consumption .....................................................................7

2Getting started................................................................................9

2.1 Safety instruction..............................................................................9

2.2 Board connection and start-up.........................................................9

2.3 DC bus capacitor discharge for demonstration purpose ................10

2.4 LED indications..............................................................................10

2.5 Possible board adaptations............................................................11

2.5.1 ACST use and MOV removal..........................................................11

2.5.2EMI filter and DC bus capacitors change........................................11

2.5.3 Power factor circuit connection .......................................................12

2.5.4 Motor Inverter connection................................................................12

2.5.5 Control with an external microcontroller..........................................12

3Conclusion....................................................................................13

4STEVAL-IHT008V1 circuit schematics........................................14

5STEVAL-IHT008V1 power supplies and typical consumption...17

6Inrush-current limitation..............................................................19

7Mains voltage dips and interruptions .........................................23

8AC voltage monitoring and zero-voltage synchronisation........26

9Triacs and AC switches insulated control..................................29

10 EN55014 test results ....................................................................31

11 STEVAL-IHT008V1 silk-screen ....................................................32

12 Test points....................................................................................35

13 Revision history ...........................................................................36

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1 Evaluation board objectives

1.1 What does this evaluation board aim to demonstrate?

This board offers an efficient solution, balancing the following requirements:

Inrush current limitation without inrush current resistor

Standby losses in line with ECO European directive

Low cost and reliable solution to drive AC loads using a single MCU and referenced to

the DC bus ground

The STEVAL-IHT008V1 board is designed to demonstrate these criteria independently;

you only need to connect the AC loads to check this part.

The STEVAL-IHT008V1 board is also intended as a development tool for designers who

want to design a whole system (appliance, air conditioning system, telecom power supply,

etc.).

For this purpose, connectors are available to add an external Power Factor Corrector, an

Intelligent Power Module (IPM) or to use an external microcontroller (see Section 2.5:

"Possible board adaptations").

1.2 Principal board blocks

Section 5: "STEVAL-IHT008V1 power supplies and typical consumption" details the

STEVAL-IHT008V1 schematics.

Figure 2: "Board synopsis" summarizes the STEVAL-IHT008V1 board with the following

main components:

The Triac (T_ICL) in series with the diode bridge

The AC switches (T1 to T5) connected on AC side to control AC loads. It should be

noted that their drive reference (A1) is also connected to the A1 terminal of T_ICL. All

A1 terminals are connected to the VCC_AC terminal, allowing this power supply to

provide a trigger current to all AC switches gates.

The MCU, which drives all the AC switches (through opto-transistors, refer to ) and

can also control any supply or motor inverter referenced to the DC bus ground

(GND_DC) in a final application.

The flyback power converter providing:

VCC_AC: 5 V output connected to the Line L1 to implement a negative power

supply. This supply is used for the Triac and AC switches control. Maximum

output current: 200 mA.

5V_DC: 5 V positive output, referenced to the DC bus Ground (GND_DC). This

output supplies the MCU and all the control circuit. Maximum output current: 90

mA.

15V_DC: 15 V positive output, referenced to the DC bus Ground (GND_DC). This

output can be used to supply an IPM to control a three-phase motor in a final

application. Maximum output current: 500 mA (together with 5V_DC

consumption).

VCC_INS: 5 V insulated output. This supply can be used if certain components,

like sensors, must be insulated from the mains voltage. This output is not used in

the demo board. Maximum output current: 90 mA.

For further information on the SMPS outputs, please refer to Section 5: "STEVAL-

IHT008V1 power supplies and typical consumption".

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Figure 2: Board synopsis

1.3 Targeted applications

Target applications include all applications using a diode-bridge to rectify the line AC

voltage and require the removal of the NTC (or PTC) resistor and the limitation of standby

losses. Such applications include:

telecom power supplies

televisions, DVD and CD players, set-top boxes, etc.

computers

lighting equipment

This demo board is also particularly interesting for applications where AC loads have to be

controlled, such as for valves, fans, pumps, heating resistors, etc. Such applications

include:

wet appliances (washing machines; dish machines; laundry dryers)

cold appliances (fridges, freezers)

air conditioning units

1.4 Main part numbers

The main part number references used in this demo board are:

Microcontroller Unit (MCU): STM8S103K3

Flyback IC: VIPER26LD

Inrush current limiter Triac: T1635T-8FP or ACST1635-8FP (pin-to-pin compatible with

T1635T-8FP, SIOV1 can be removed)

AC loads AC switches:

T1: ACST210-8FP (TO-220FPAB package)

T2 and T3: ACS108-8SN (SOT223 package)

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T4 and T5: Z0109MUF (SMD package)

1.5 Operating range and performances

The STEVAL-IHT008V1 board is designed to operate inside the following operating ranges:

Line voltage, 2 ranges are possible:

198-264 V RMS, 50 or 60 Hz

90-132 V RMS, 50 or 60 Hz. For this voltage range, operation both in rectifier

mode (DC peak voltage = peak line voltage) or in doubler mode are possible (see

Section 2.2: "Board connection and start-up").

Ambient temperature: 0°C to 60°C

Maximum DC load power:

DC load (connected between HVDC and GND-DC): 1000 W or 500 W

respectively for operation on 230 V or 120 V mains.

Maximum AC load power:

T1: maximum load RMS current has to be lower than 1.1 A, this allows 250 VA or

130 VA power for operation on 230 V or 120 V mains, respectively. This Triac

can be used to control a heating resistor or a pump.

T2 to T5: the footprint for each of these devices allow either a SMBflat-3L or a

SOT-223 package to be soldered. By default, two ACS108-8SN (SOT-223) are

used for T2 and T3, with a 5.5 mm² copper area under the tab. These devices

can control an RMS load current up to 0.6 A. This allows a 100 VA or 50 VA

power load to be controlled on 230 V or 120 V mains, respectively. By default,

two Z0109MUF (SMBflat-3L) are used for T4 and T5, with a 33.6 mm² copper

area under the tab. These devices can control an RMS load current up to 0.44 A.

This allows a 140 VA or 70 VA power load to be controlled on 230 V or 120 V

mains, respectively. These four Triacs can be used to control a pump, a fan or

any electromagnet (valve, damper, door-lock, etc.).

Allowed DC output capacitor (or DC bus capacitor) range: 50 µF to 500 µF (in rectifier

mode) or to 1000 µF (in doubler mode).

This DC output capacitor value is the equivalent value of all capacitors placed in

parallel at the bridge output, like C1, C9, C3, and CPFC at PFC output (refer to

Figure 3: "Connection of a PFC at the HVDC output"). If an interleaved PFC is

used, all the output capacitors of each PFC must be added.

If the J7 connector is closed (doubler mode), no PFC should be used. C3 is also

not added. In this case, the equivalent capacitor is only C1 (or C9 as they both

have the same value).

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Figure 3: Connection of a PFC at the HVDC output

The main STEVAL-IHT008V1 board performance characteristics are:

Efficiency at 230 V 50 Hz 1000 W (only DC resistive load) = 97%

Efficiency at 120 V 60 Hz 500 W (only resistive DC load, rectifier or double modes) =

96%

Standby losses < 150 mW (refer also to section 2.6)

Compliance with IEC 61000-3-3 (with potentiometer "MAX_INRUSH CURRENT" set

to default position; refer to Section 6: "Inrush-current limitation")

Compliance with EN55014 (CIPSPR 22 method B; refer to Section 10: "EN55014 test

results")

IEC 61000-4-4: 2 kV criteria A, T_ICL Triac withstands a 5 kV level without triggering.

This is to avoid undesirable triggering and uncontrolled inrush current due to EMI

noise.

IEC 61000-4-5: 2 kV criteria A

IEC61000-4-11: criteria A for dips down to 100% of the line voltage during 1 cycle;

criteria B for interrupts up to 300 cycles or more (refer to Section 7: "Mains voltage

dips and interruptions").

Figure 4: "Inrush current at STEVAL-IHT008V1 startup on 230 V line (500 µF output DC

capacitor)" shows an example of the progressive DC capacitor charge ensured by the

T_ICL Triac. The test is performed at startup when the STEVAL-IHT008V1 board is

connected to a 230 V 50 Hz grid, while the output DC capacitor is completely uncharged

(initial voltage is zero). The output DC capacitor is implemented in this case via the series

association of C1 and C9, hence the equivalent capacitance is 500 µF.

The output capacitor is charged in 550 ms with the input RMS current remaining far below

the 16.1 A limit. IEC 61000-3-3 compliance is therefore easily achieved.

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Figure 4: Inrush current at STEVAL-IHT008V1 startup on 230 V line (500 µF output DC

capacitor)

1.6 Stand-by consumption

One of the main advantages of using the T_ICL Triac in front of the rectifier bridge is that it

allows full bridge disconnection during standby to suppress losses. This can also be

achieved by adding a front-end relay (like S2 in Figure 5: "Solution using relays to limit

inrush current and standby losses"). But, thanks to the T_ICL Triac, this function is already

available by simply turning off this Triac.

Figure 5: Solution using relays to limit inrush current and standby losses

To give an idea of the benefits of such bridge disconnection, we measured the typical

losses of the STEVAL-IHT008V1 board in standby mode. Three cases are tested:

Case 1: STEVAL-IHT008V1 board (unmodified) with T_ICL in OFF state ("HVDC"

switch in OFF position).

Case 2: as above, but with a PTC (EPCOS B59107J0130A020) plugged in place of

the T_ICL Triac to simulate the losses for a classic solution using only one PTC and

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one bypass relay (refer to RLIM and S1 on Figure 5: "Solution using relays to limit

inrush current and standby losses").

Case 3: as above, but circuits used solely for demonstration purposes and which

consume undesired power at standby are disconnected. These circuits are the "HV

Capacitor Discharge" circuit (where R7 and R10 are connected to the DC bus) and the

"HVDC" LED (D2) indicating presence of high voltage (where D1, R12, and R13 are

connected to the DC bus).

Table 1: "Comparison of standby losses" gives the experimental results for the three cases

in the three different modes of operation (230 V, 110 V line voltage in rectifier and doubler

mode). The tests results clearly show that the Triac solution is the only one to achieve a

power consumption level lower than 0.5 W, as currently required by European directive

2005/32/EC.

The losses measured for case 3 are mainly due to the resistor divider circuit (R9, R11,

R14, R16) used to balance the voltage across the 2 series capacitors (C1 and C9) and the

other resistor divider circuit (R30, R31) used to sense the HVDC voltage. On our board, the

HVDC voltage is monitored to check proper soft-start operation and to avoid that the DC

capacitor charge duration is too long (if, for example, a load remains connected to the DC

bus before start-up). In standard circuits, however, such a voltage sensor is often required

(to start the PFC or the DC-DC supplies, for example).

The losses for a 230 V rectified voltage equal 520 mW for the 200 kΩ R9, R11, R14 and

R16 equivalent resistor, and 52 mW for the 2 MΩ R30 and R31 equivalent resistor.

Table 1: Comparison of standby losses

Mode of

operation

Case 1

T_ICL OFF

Case 2

PTC instead of Triac

Case 3

PTC discharge and D2 LED

circuits removed

230 V

125 mW

1.7 W

950 mW

110 V / rectifier

mode

70 mW

0.6 W

280 mW

110 V / doubler

mode

70 mW

1.5 W

860 mW

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2 Getting started

2.1 Safety instruction

The high voltage levels used to operate the STEVAL-IHT008V1 evaluation board

can represent a serious electrical shock hazard. This evaluation board must be

used in a suitable laboratory only by qualified personnel who are familiar with the

installation, use, and maintenance of power electrical systems.

The STEVAL-IHT008V1 evaluation board is designed for demonstration purposes only,

and must never be used for either domestic or industrial installations.

2.2 Board connection and start-up

Please follow this procedure to use the STEVAL-IHT008V1 board:

1. If you want to operate the board on a 98-132 V line voltage and have a DC bus

voltage two times higher than the peak line voltage, plug the jumper (see Figure 6: "(a)

J7 jumper plugged on board (doubler mode)") to the position indicated by the silk-

screen (refer to Figure 7: "(b) Jumper position left free (rectifier mode)"). If you want

the rectifier to operate in a classic rectifier circuit, do not plug the J7 jumper.

2. Connect the AC load terminals (if used) to the associated headers (e.g., for AC switch

T1, refer to the "N1-OUT1" label in Figure 23: "STEVAL-IHT008V1 silk-screen (Top

side)").

3. Connect the L, N and PE (if required) of J9 header to an unpowered mains plug.

4. Apply the mains voltage. From this moment on, avoid any contact with live parts

subject to line voltage.

5. Switch the "HVDC ON" toggle button to the "ON" position" to start charging the DC

capacitors.

6. The AC loads are switched on and off each time the associated push-buttons (T1 to

T5) are pressed. These loads are controlled even if the "HVDC ON" button is kept in

the OFF position.

7. The rate of DC capacitor charging can be increased if the allowed peak current is

increased. To do this, turn the "MAX-INRUSH CURRENT" potentiometer clockwise.

compliance with the IEC 61000-3-3 standard is only guaranteed when th

potentiometer is set to the default position (between 0 and 1 mark) and with

original values of the EMI filter and output DC capacitors.

The following figures show the J7 jumper connection for doubler mode (a) or rectifier mode

(b).

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Figure 6: (a) J7 jumper plugged on board

(doubler mode)

Figure 7: (b) Jumper position left free

(rectifier mode)

2.3 DC bus capacitor discharge for demonstration purpose

With default STEVAL-IHT008V1 1000 µF output capacitors (C1, C5) and associated 50 kΩ

resistors (R9, R11, R14, R16) used in parallel to balance the voltage across the two series

capacitor, the DC bus discharging time takes a few minutes if no load is connected.

A circuit is included to accelerate this discharging time, especially if several startups need

to be performed inside a short time interval for test or demonstration purposes. This circuit

is made with the Q2 MOSFET and R8 Resistor. Q2 remains on for as long as the SW7

SPDT toggle (refer to the "HV CAPACITOR DISCHARGE" label in Figure 23: "STEVAL-

IHT008V1 silk-screen (Top side)") is switched to the momentary ON position.

The two 1000 µF capacitors are then discharged within two seconds, approximately. The

SW2 switch must at least be kept in the momentary ON position during these two seconds.

The D2 LED (refer to the "HVDC" label in Figure 23: "STEVAL-IHT008V1 silk-screen (Top

side)") remains lit while the HVDC voltage is above 50 V, so the SW2 switch can be

released and a new startup can begin as soon as this LED turns off.

2.4 LED indications

Several LEDs are available to signal useful information:

ICL-STATUS" (LED D18): indicates several things according to its color:

When the board is powered, the LED passes from red, to orange, to green, which

indicates that the microcontroller has finished startup (correct mains connection

and line frequency measurement, power supply available, etc.) and the board is

ready. The green LED then switches off to reduce the board consumption in

standby. From this moment, the DC output capacitor can be charged when the

"HVDC" switch (SW6) is set to the "ON" position.

Green flashing indicates the DC bus capacitors are charging (flashing starts after

setting the "HVDC" button to the ON position and ends when the DC bus

capacitors are fully charged). This flashing mode can last less than 1 second and

may therefore go undetected by the end-user.

Green constant indicates the DC bus is charged to the correct voltage.

Orange flashing indicates the DC bus capacitors are charging but the output DC

voltage rate of increase is too low. This may occur if a power load is connected to

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