DRIVE CIRCUIT FOR SWITCH

• US 20200136603A1
• Filed: 10/21/2019
• Published: 04/30/2020
• Est. Priority Date: 10/25/2018
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: DEWA, Tetsuya
• Granted Patent: US 11,218,143 B2
• Time in Patent Office: Days
• CPC Class Codes: H02M 1/0054 Transistor switching losses periodically suspending operation of switching converter in low power mode H02M1/0035
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/088 for the simultaneous control of series or parallel connected semiconductor devices
• CPC Class Codes: H02M 7/5387 in a bridge configuration
• CPC Class Codes: H02P 27/06 using dc to ac converters or inverters H02P27/05 takes precedence
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: H03K 17/08116 in composite switches H03K17/0812, H03K17/0814 take precedence
• CPC Class Codes: H03K 17/0828 in composite switches
• CPC Class Codes: H03K 17/162 without feedback from the output circuit to the control circuit
• CPC Class Codes: H03K 17/166 Soft switching
• CPC Class Codes: H03K 17/168 in composite switches
• CPC Class Codes: H03K 2017/066 Maximizing the OFF-resistance instead of minimizing the ON-resistance
• CPC Class Codes: H03K 2217/0027 Measuring means of, e.g. currents through or voltages across the switch

Abstract

A drive circuit Dr for a switch that reduces a surge voltage caused when a switch SW is switched to an off state. The drive circuit Dr detects, as an on voltage Von, a collector-emitter voltage of the switch SW while the switch SW is in an on state. When the detected on voltage Von is large, the drive circuit Dr sets a resistance value Rd of a discharging resistor 53 when the switch SW is switched to an off state to be larger than the resistance value Rd when the detected on voltage Von is small. More specifically, the drive circuit Dr sets the resistance value Rd to a larger value as the detected on voltage Von is increased.

Claims

1. A drive circuit (Dr) for a switch, the drive circuit driving a switch (SW, SWA, SWB), the drive circuit comprising:

an acquisition section, which acquires a surge-correlated value, the surge-correlated value being one of an inter-terminal voltage (Von, VonA, VonB) of the switch while the switch is in an on state and a time period from when an on command for the switch is issued to when a gate voltage of the switch reaches a determination voltage (Vα

) that is less than an upper limit value (VH) and is larger than or equal to a Miller voltage (Vmil); and

a setting section, wherein, when the acquired surge-correlated value is larger, the setting section sets a switching speed of the switch when the switch is switched to an off state to be lower than the switching speed of the switch when the acquired surge-correlated value is small.

2. The drive circuit for the switch according to claim 1, wherein the setting section sets the switching speed when the switch is switched to the off state to a lower value as the acquired surge-correlated value is increased.

3. The drive circuit for the switch according to claim 1, wherein the acquisition section acquires, as the surge-correlated value, the inter-terminal voltage of the switch while the switch is in the on state.

4. The drive circuit for the switch according to claim 3, wherein, after the on command is issued, the acquisition section acquires the inter-terminal voltage at every predetermined control cycle during a time period until an off command for the switch is issued,

the setting section sets the switching speed in accordance with the inter-terminal voltage every time the acquisition section acquires the inter-terminal voltage, and

the switch is switched to the off state by the switching speed set at the point in time when the off command is issued.

5. The drive circuit for the switch according to claim 3, further comprising:

a speed calculator, which calculates an increase speed of the inter-terminal voltage in accordance with the inter-terminal voltage acquired by the acquisition section during the time period after the on command is issued until the off command for the switch is issued; and

an estimation section, which estimates the inter-terminal voltage at the point in time when the off command is issued in accordance with the calculated increase speed, wherein

the acquisition section acquires the estimated inter-terminal voltage as the surge-correlated value.

6. The drive circuit for the switch according to claim 3, wherein

the acquisition section further acquires a time period from when the on command is issued to when the gate voltage reaches the determination voltage, and

the switch is switched to the off state at the lower one of a first switching speed set in accordance with the acquired inter-terminal voltage and a second switching speed set in accordance with the acquired time period.

7. The drive circuit for the switch according to claim 1, wherein the acquisition section acquires, as the surge-correlated value, a time period from when the on command is issued to when the gate voltage reaches the determination voltage.

8. The drive circuit for the switch according to claim 1, wherein, in the drive circuit that drives a plurality of the switches (SWA, SWB) in parallel connection with each other,

the acquisition section acquires the surge-correlated value of each switch while each switch is in the on state, and

the setting section uses the largest one of the acquired surge-correlated values for setting the switching speed.

9. The drive circuit for the switch according to claim 1, wherein, in the drive circuit that drives a plurality of the switches (SWA, SWB) in parallel connection with each other,

among the switches that are in the off state, the switch that is switched to the on state first is referred to as a first on switch (SWA), and among the switches that are in the on state, the switch that is switched to the off state last is referred to as a last off switch (SWA, SWB),

the acquisition section acquires the surge-correlated value of the first on switch, and

when the surge-correlated value is large, the setting section sets the switching speed of the last off switch when the last off switch is switched to the off state to be lower than the switching speed when the acquired s surge-correlated value is small.